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ANTHROPOGENIC NUTRIENT ENRICHMENT IN BAYS AND WATER SHEDS: A COMPARISON OF SARASOTA BAY, FLORIDA AND KANEOHE B AY, HAWAII BY ALLISON WYATT A Thesis Division of Natural Sciences New College of Florida in partial fulfillment of the requirements for the degree Bachelor of Arts Under the sponsorship of Dr. Diana Weber Sarasota, Florida May, 2012
ii ACKNOWLEDGEMENTS There are a number of people who made this thesis p ossible and assisted me throughout the process. I would like to thank the New College Environmental Studies Committee and the New College Council for Academic Affairs for allocating me gran t money necessary for supplies and shipping. I would also like to acknowledge Colleen Swessel for ordering my supplies, Dr. Paul Patek fr om the University of Hawaii at Manoa for use of his laboratory, my parents John and Rebe cca Wyatt for supporting me and helping me collect samples in Hawaii, and Alexander Duff for helping me with research in Florida. I would especially like to thank Dr. H eidi Harley, Dr. Suzanne Sherman, and Julie Morris for being on my committee, and Dr. Dia na Weber, who was not only my sponsor but my initial inspiration for this thesis and never stopped encouraging me.
iii TABLE OF CONTENTS List of Tables .. iv List of Figures .. . ...v List of Appendices . .. . .vii Abstract ... . ... ..viii Introduction and Background . .. .. .1 Materials and Methods ... .. ..18 Results .. .. 25 Discussion .. .. ..28 Conclusion .39 References ... .. .41 Tables . 48 Figures .. .. 55 Appendix 1 .. .. .80
iv LIST OF TABLES Table 1. Upstream and Downstream Sites in Hawaii Table 2. Upstream and Downstream Sites in Florida Table 3. Significant Values between Upstream and Do wnstream Sites Table 4. Comparison of Hawaii Sites: Critical Value s Table 5. Comparison of Florida Sites: Critical Valu es Table 6. Status of Impaired Waterbodies around Kane ohe Bay Table 7. Status of Impaired Waterbodies around Sara sota Bay
v LIST OF FIGURES Figure 1. The nitrogen cycle Figure 2. Sampling sites in Sarasota Bay, Sarasota, Florida USA Figure 3. Sampling sites in Kaneohe Bay, Kaneohe, H awaii USA Figure 4. Keneke Street site in Hawaii Figure 5. Holowai Street site in Hawaii Figure 6. Alaloa Street site in Hawaii Figure 7. Fishpond site in Hawaii Figure 8. Kaneohe Market site in Hawaii Figure 9. Kauhale Beach Cove site in Hawaii Figure 10. Golf Course Bridge site in Florida Figure 11. Magellan Drive site in Florida Figure 12. Westmoreland Street site in Florida Figure 13. 32nd Street site in Florida Figure 14. Whitakers Lane site in Florida Figure 15. High School site in Florida Figure 16. Selby Gardens site in Florida Figure 17. Mean nutrients at all sites in Hawaii Figure 18. Comparison of all upstream and downstrea m nutrient means in Hawaii Figure 19. Mean nutrients at all sites in Florida Figure 20. Comparison of all upstream and downstrea m nutrient means in Florida Figure 21. Comparison of nutrient means between Flo rida and Hawaii Figure 22. Comparison of salinity means between Flo rida and Hawaii
iii Figure 23. Comparison of distance to respective bay between upstream and downstream sites in Florida and Hawaii Figure 24. Mean annual rainfall and watershed bound aries in Oahu, Hawaii Figure 25. Florida average annual precipitation
vii APPENDICES Appendix 1. GPS coordinates for all sites
viii ANTHROPOGENIC NUTRIENT ENRICHMENT IN BAYS AND WATER SHEDS: A COMPARISON OF SARASOTA BAY, FLORIDA AND KANEOHE B AY, HAWAII Allison Wyatt New College of Florida, 2012 ABSTRACT Bays and watersheds are threatened globally by anth ropogenic nutrient enrichment, a process that degrades water quality t hrough an influx of nutrients including nitrogen, ammonia, and phosphorous. Two areas of t he United States that have experienced periods of degraded water quality that have lead to declines in their bay ecosystems are Kaneohe, Hawaii, and Sarasota, Flori da. As their recent histories and land uses are similar, I chose to compare the nutri ent content in the watersheds of these two locations as well as show how nutrient levels d iffered based on their location within the watershed. My results suggest that nutrient le vels are generally higher within the watershed than near the mouth of the bay, and that Kaneohe has significantly greater levels of nitrates while Sarasota has significantly greater levels of phosphates. Levels of ammonia were similar between both bays. The dispar ities in nutrient levels are due to geological and physical differences unique to each location as well as surrounding land uses and characteristics of each testing site. It is critical to continue studying watersheds and examine how changes and processes in the waters hed affect its adjacent off-shore ecosystems, especially as coastal development and p opulations continue to grow and threaten the health of bays and watersheds. Dr. Diana Weber Division of Natural Sciences Environmental Studies Program
Introduction and Background Purpose of Study This study was conducted to examine anthropogenic nutrient enrichment and the impacts it has on bays and watersheds. I specifica lly investigated Kaneohe Bay, Hawaii and Sarasota Bay, Florida because of their similar, urban aspects and measured nutrient levels in tributaries adjacent to each bay. I comp ared nutrient levels within each location at different areas in the watershed as well as nutr ient levels between both Kaneohe and Sarasota. Watersheds and Water Quality A watershed is an area of land, in which all the wa ter draining off it is diverted to a common location (Bade 2009). In the United State s, rapidly growing populations have spread causing detrimental impacts over its 2,000 w atersheds. The greatest changes in anthropogenic nutrient cycling have been in coastal ecosystems with high population density and/or intense agriculture practices (Howar th et al. 2000). Anthropogenic, landbased nutrient enrichment is a threat to aquatic ec osystems around the world (Howarth et al. 2000), and nutrients like nitrogen and phosphor ous are directly related to water quality (Hulen and Angino 1979). A healthy ecosystem needs nutrients, but excess amounts are harmful if they enter coastal waters ( Sarasota Bay Estuary Program 2010), ultimately contributing to significant ecological impacts (Pet erjohn and Correll 1984). For example, near-shore ecosystems, e.g., seagrass beds and cora l reefs, can reflect the health of the entire watershed (Kaiser et al. 2008). Increases in population and coastal development are exposing aquatic ecosystems to greater amounts of nutrients (Fabricius 2005), w hich affects biological growth (Fruh et
al. 1966). Nutrient pollution has been associated with dangerous algal blooms, shellfish poisoning, reductions of biodiversity in ecosystems and eutrophication ( Sarasota Bay Estuary Program 2010, Howarth et al. 2000). The latter is a progre ssion of changes that occur when excess nutrients cause increases in prim ary producers (algae, phytoplankton, plants) biomass (Schindler 2009). Water may become turbid from the increased biomass and block sunlight essential for growth of photosyn thesizing organisms as well as lead to an increase of mortality as oxygen is depleted in t he water. The excess of decaying organisms can result in hypoxia and potentially ano xia (Howarth et al. 2000). As these conditions persist ecosystem can become stressed, c ausing organisms to move if possible or die, thus changing the biodiversity and abundanc e present. Land use changes affect hydrologic processes direct ly (Fohrer et al. 2001) and influence water quality (Gove et al. 2001). For ex ample, with expanding urban areas and residential development there is a decrease in natu ral areas and an increase in impervious surfaces, which alter the natural conditions of wat ershed hydrology by creating more surface and stormwater runoff (Tang et al. 2005). Wastewater runoff from sewage can contribute large amounts of nitrogen to a watershed if the environment around the watershed is intensely populated (Howarth et al. 20 00). Erosion occurs from construction, which can result in sedimentation, ma king adjacent waterbodies more turbid. Additionally, pollutants can come from ind ustrial activities that utilize toxic substances, which enter the environment (Gove et al 2001). Besides urbanization, other anthropogenic activitie s, e.g., land clearing, agriculture, and fertilizer use, change water quali ty in coastal areas, creating further damaging effects to surrounding watersheds (Fabrici us 2005). Increases of nitrogen
levels are a special concern in coastal waters. As agriculture has increased, so too have the amount of nutrients making their way into adjac ent waters (Peterjohn and Correll 1984, Gove et al. 2001), providing a significant no npoint source of nitrogen into surrounding watersheds and coastal waters through r unoff (Howarth et al. 2000). Animal waste associated with agricultural production also plays a large role in the influx of nitrogen into coastal waters. Another nutrient, ph osphorous, is often associated with fertilizer compounds and agriculture, and the compl exity of both nitrogen and phosphorous interactions within aquatic ecosystems can create detrimental effects. Large amounts of nitrogen, phosphorous, and other h armful compounds in the environment mandate the need for proper management of fertilizers (Heathwaite et al. 2000). Appropriate management provides direct bene fits, e.g., improved water quality and quantity inside the watershed, ground and surfa ce water quality enhancement, aquifer recharge, and biodiversity protection. This increa ses the health of the watershed, which positively impacts near-shore resources (beaches) a nd off-shore resources (seagrass beds and coral reefs). The connection between health of the watershed and the resources is not usually considered when it comes to policy decision s, but is necessary when devising comprehensive watershed conservation strategies. W atershed conservation creates both ecological and economical benefits, and in some wat ersheds, it has been found that the cost of conservation was very low compared to the e conomic benefits realized (Kaiser et al. 2008). Water Quality Indicators Many factors inherent in aquatic ecosystems must b e maintained at ranges optimal for organisms living in the ecosystem, othe rwise organisms become stressed,
suffer from decreased health, which can affect thei r overall fitness and lead to death. The following are necessary components to the well bein g of organisms in aquatic ecosystems and thus indicators of water quality. Nitrogen The global nitrogen cycle (Figure 1) has been sever ely altered as the use of inorganic nitrogen fertilizers has been steadily in creasing since the mid-20th century (Howarth et al. 2000). Nitrogen-containing fertili zer contributes to 70% of the anthropogenic greenhouse gas nitrous oxide (N2O) in the world (Matson et al. 1998). In addition to fertilizers used for agriculture and la wns, other sources of nitrogen include animal waste, sewage, and industrial pollutants (Co lorado River Watch Network 2011). Excess nitrogen increases algal growth and depletes oxygen essential for aquatic life (Colorado River Watch Network 2011), leading to eut rophication, particularly in temperate, coastal waters (Howarth et al. 2000). F urthermore, 10 mg/L or more of nitrogen in drinking water can be toxic to humans ( Colorado River Watch Network 2011). Nitrogen pollution is one of the main conce rns surrounding the water quality for Sarasota Bay ( Sarasota Bay Estuary Program 2010). Nitrogen may undergo a number of transformations, e ach of which has its own concern as a pollutant. Organic nitrogen changes t hrough mineralization to become ammonium nitrogen, a compound used by plants, provi ding an indication why organic nitrogen is the largest amount of nitrogen found in soils (Barbarick 2011). Nitrification is the process where ammonium nitrogen transforms into oxidized nitrogen (nitrate) aerobically by bacteria and is used by plants. Nit rates (NO3 ) leach easily from the soil where they are naturally occurring, and flow into w astewater, raising concerns for
pollution. Both ammonium nitrogen and nitrates may undergo immobilization, turning back into unusable organic nitrogen. Additionally, gases, e.g., denitrification and ammonia volatilization, can be products of nitrogen transformations. Denitrification occurs when microrganisims, in low-oxygen soil, tra nsform nitrate into gaseous nitrogen. Similarly, ammonia volatilization is ammonium nitrogen convert ing to ammonia gas in soils that have a 7.5 or greater pH value. Nitroge n naturally exists as a gas in the atmosphere, but must be converted by processes into nitrate, a compound of nitrogen and oxygen, to be used by organisms such as plants. Ammonia Ammonia as nutrient enrichment can originate from f ertilizers in agricultural runoff, animal wastes, and anthropogenic sources, e .g., industrial waste and wastewater treatment facilities. In the environment, organic nitrogenous matter naturally degrades into ammonia, (Augspurger 2003) that can be convert ed into ammonium by becoming ionized (NH4 +). Ammonia, a common pollutant, is toxic to aquati c organisms, in contrast to ammonium that is not (Sawyer 2008). Ammonia is a common component of fertilizers and sometimes applied as anhydrous ammonia, which i s without water (Nowatzki 2011). Stored under high pressure as a liquid, the anhydro us ammonia is applied in agricultural systems as a gas, and can be very harmful to organi sms if not diluted by water. Ammonia can be volatilized into the atmosphere in t errestrial agriculture, while in aquatic environments, ammonia often becomes concent rated in the sediment (Howarth et al. 2000). Phosphorous
Similar to nitrogen, phosphorous increases primary productivity and biomass in aquatic environments while simultaneously decreasin g oxygen (Howarth et al. 2000). Human activities have doubled non-point sources of phosphorous flowing into coastal waters (Howarth et al. 2000) and sources such as ag riculture have contributed to eutrophication of rivers and lakes throughout the U nited States and Europe (Heathwaite et al. 2000). Phosphorous is important for plant h ealth, and plants with phosphate deficiencies suffer from stunted growth, delayed ma turity, and reduced seed quality (Howarth et al. 2000). Phosphorous is widely used i n fertilizers because soils often do not naturally contain enough phosphorous to produce max imum crop yields and plant growth (Hart et al. 2004). However, it is often lost due to soil leaching and runoff. Phosphate (PO3 4), a polyatomic anion and the common inorganic form of phosphorus, present in the natural environment, has historically been de rived in coastal environments from use of detergents, which enter the water in sewage (Ryt her and Dunstan 1971, Smil 2000). In urban environments this sewage can account for the largest sources of phosphorous, though phosphorous compounds have been banned in ma ny detergents since the 1970s (Smil 2000). Unlike ammonia and nitrates, an influx of phosphoro us into aquatic environments is not directly toxic to fish, livestock, or humans (Florida Industrial and Phosphate Research Institute) unless concentrations are very high (Smil 2000), but even small amounts can lead to degraded water quality and eutr ophic conditions (Hart et al. 2004). Neuro and hepatotoxins released from phosphorous de rived algal blooms can be hazardous if ingested, and contribute to fish kills (Smil 2000). Phosphorous is thought to be a key nutrient in algal blooms, especially in fr esh water (Correll 1999). Though
phosphorus concentrations have been reduced by 50% between 1985 and 1995, many soils are still rich with phosphorus and make their way into waterbodies through erosion. Many management plans have focused on the reduction of nitrogen in fertilizer, which has resulted in overcompensation in phosphorous ins tead, causing some areas to be at risk for degradation from high phosphorous concentration s in soil and waterbodies (Heathwaite et al. 2000). Fecal coliform Fecal coliform from animal and human wastes can res ult in harmful pathogens, for example Escherichia coli that infect living organisms in the environment ( Cahoon et al. 2006, Colorado River Watch Network 2011). Aqua tic systems and water supplies are often regulated for fecal coliform to monitor level s in water that may contain raw sewage and stormwater runoff (Auer and Niehaus 1993). If f ecal coliform levels remain high bodies of water may be listed as impaired. Dissolved Oxygen Dissolved oxygen (DO ) is extremely important for all organisms living in aquatic environments and must be maintained within a certai n range (Colorado River Watch Network 2011). DO is essential for organism surviv al, but harmful if levels become too high. In comparison, decreased levels of DO result ing from increased decomposition of sewage and plant matter in the water are also harmf ul. pH The pH of water describes its alkalinity or acidity concentration on a scale from one to 14, with seven being neutral (Colorado River Watch Network 2011). pH values lower than seven are more acidic and values higher than seven are more basic. Many
aquatic organisms can only tolerate a limited pH ra nge without becoming stressed physiologically (Addy et al. 2004). Acid rain, pol lution, agricultural runoff, bedrock, and wastewater can all affect pH levels. Temperature Many organisms require a specific temperature rang e to survive successfully (Colorado River Watch Network 2011). Water tempera ture can affect the types of aquatic plants present in the environment, determin e susceptibility organisms have to parasites and diseases, and change DO in the water. Urban sources, such as industry, can change temperatures in watersheds. Salinity When freshwater from the watershed meets and mixes with saltwater, a salinity gradient is created in the area, i.e. estuaries (Ey re and Balls 1999). This gradient can change nutrients chemically, physically, and biolog ically, affecting dissolution, recycling, and biological uptake. How the nutrients interact with the water influences how they are cycled and what impacts they have on the ecosystem. Additionally, tides, as well as the amount of freshwater flowing into the ecosystem (st reams, runoff, flooding events), influence salinity. Seagrass Seagrass beds are found in shallow coastal waters t hroughout the world and provide a biological and physical basis for aquatic ecosystems (Kurz et al. 1999). Extremely productive, seagrasses have a high nutrie nt demand and thus have an important role in cycling nutrients (Hemminga et al 1991). Seagrass beds provide habitat for different stages of species life cycles including nursery grounds and foraging
n areas for many commercial fish and shellfish specie s (Little 2000). As rooted soft bottom plants, seagrasses slow the flow of water, collect and stabilize sediments, and support large populations of epiphytic organisms (Mann 1982 ). Along many parts of the coast of Florida, such as in Sarasota Bay, seagrasses are im portant because of their economical and ecological values, and it is therefore essentia l to monitor seagrasses for trends in distribution and health (Kurz et al. 1999). This m onitoring provides insight to management tools to protect seagrasses in estuaries like Sarasota Bay. The distribution and health of seagrass is affected by various anthropogenic and environmental factors (Ralph et al. 2007). Light a vailability is one factor seagrasses are sensitive to and even small decreases in the amount of light available can cause seagrasses to decline because without light, photos ynthesis, the process necessary for production of carbohydrates and oxygen, cannot occu r. For light to reach seagrasses, it must penetrate through the water column as well as any epiphytes (small plants growing on seagrass blades). Light attenuation can be infl uenced in a number of ways, depending on depth and other physical attributes of the water Human activities such as development, agriculture, fishing, and dredging may change light attenuation and create run-off, which can offload excess sediments and nut rients into the water. The Sarasota Bay Estuary Program determined that decreased light attenuation is the main abiotic factor shaping the amount of seagrass coverage in S arasota Bay and that management goals should focus on increasing water clarity (Mot e Marine Laboratory 1995). Other factors affecting seagrass growth and distrib ution include water depth, salinity, and temperature, depending on the species of seagrass (Mann 1982). While some seagrasses may be able to survive in very shal low intertidal waters, maximum
biomass of seagrass is normally located in areas of total submergence, and seagrasses will often grow downwards in depth as far as necessary l ight penetration will reach. Some species of seagrass can tolerate and survive low sa linities of 10% and low temperatures just above freezing in the winter, though higher te mperatures are required for flowering (Mann 1982). Other seagrasses are able to tolerate combinations of stresses, but certain combinations are detrimental. Zieman Jr. (1970) fo und that turtle grass was able to tolerate low salinity and temperate but not low sal inity and high temperature. Coral Reefs Coral reefs support some of the highest benthic pro ductivity in the world and provide habitat for a diverse and large number of o rganisms in tropical and sub-tropical regions (Szmant-Froelich 1983). The backbone coral reefs are the anthozoan coelenterates, reef-building corals that produce ex ternal calcium carbonate skeletons to provide the structure and support system of a coral reef (Mann 1982). Corals form a symbiotic relationship with unicellular algae, call ed zooxanthellae, that live within the tissues of corals. Corals need access to sunlight, and therefore they generally grow in waters less than 25 meters. Zooxanthellae use the energy obtained from sunlight to photosynthesize, produce, and transfer energy to th e corals. The energy produced affects the growth rate of the calcium skeleton in the cora l colony (Mann 1982). This form of energy production is very important for corals as t hey live in nutrient poor waters with little primary productivity. However, corals acqui re nutrients in a variety of ways; besides photosynthetic production by zooxanthellae, corals filter particles (e.g. plankton) in the water, take in organic matter dissolved in t he water, and use extent land-based nutrients from terrestrial runoff (Nybakken and Ber tness 2005).
There are many direct anthropogenic effects which c an physically and permanently affect coral ecosystems (Fabricius 2005 ), and the impacts on reefs have grown exponentially with increased human population s (Hughes et al. 2003). Excess nutrients enter coral reef ecosystems through terre strial runoff and cause stress by promoting the increase of macroalgae and phytoplank ton (Fabricius 2005) as well as decrease light, increase siltation, and contribute to salinity stress (Szmant-Froelich 1983). Nutrient enrichment, increased sediments, and highe r turbidity have all been shown to compromise reefs at local levels, but effects are h arder to assess at regional scales due to compounded amounts of pollutants and other disturba nces (Fabricius 2005). Increased nutrients can change a coral-dominated system to a n algal-dominated one and once this occurs it is extremely difficult to return the ec osystem to a coral-dominated state (Hughes et al. 2003). Exposure to chemical and oil pollution from runoff or spills may also have toxic effects on corals and reef organisms (Hughes et al. 2003). Coastal development can involve dredging, erosion, or increased sediment de position, which may smother or bury corals. Long-term sedimentation can block sunlight ; this reduces the ability of zooxanthellae to photosynthesize and impacts coral growth. These human-induced stresses that deteriorate water quality and increas e pollution can make corals more susceptible to diseases, furthering the possibility of permanent and long-term damage. Even if corals are not killed by these stresses, th ey can remain compromised for long periods of time, unable to sustain high levels of p roductivity and diversity (Kaiser et al. 2008). Sarasota Bay
Sarasota Bay, Florida (Figure 2a), is an estuarine water body of approximately 83 km2 (United States Environmental Protection Agency 201 0) comprised of many embayments and tributaries ( Sarasota Bay Estuary Program 2010) (Figure 2b). Since its formation approximately 6,000 years ago, the bay ha s experienced many changes in shoreline, sea level, and usage. In the 1500s, Sa rasota Bay served an important role as one the primary waterways for many Native Americans living in Florida, but with the arrival of Europeans and new diseases, these early populations were wiped out by the end of the century. In the following centuries, Cuban fisherman, Seminole Indians, and European explorers all utilized the bay for its res ources. By the 1920s, projects to drain 100,000 acres of f reshwater sawgrass marshes were conducted for Sarasota Bay to produce more agr iculture land ( Sarasota Bay Estuary Program 2010). However, after the Second World War a larg e population influx caused these drained lands to be developed as residential areas. Coastal development exploded from the 1950s to 1970s, with continued dredging and draining of the bay and its canals. One of the largest changes in the bay was the development of Bird Key, located between downtown Sarasota and St. Armands Key. Bir d Key was built up and enlarged with dredged materials from the bay to provide addi tional residential property. Unfortunately, Bird Key was historically the locati on of one of the largest seagrass beds in Sarasota Bay. Additional dredging, construction of the Intercoast al Waterway channel, and other activities continued to smoother and reduce seagras s habitats ( Sarasota Bay Estuary Program 2010). Miles of natural shoreline and mangroves w ere replaced with seawalls causing the usual patterns of water circulation in the bay to be altered. Seagrasses were
further compromised by increased nonporous surfaces in the areas surrounding the bay, which contributed to increased stormwater runoff an d contaminants flowing into the bay, subsequently further reducing water quality, and de creasing seagrass growth and habitat for organisms within the seagrass beds. Though the watershed has experienced intense development, major sources of pollutants come from non-point sources such as stormwater, agricultural and urban runoff, and mari nas; point sources account for wastewater effluents (Sherblom et al. 1995). Point sources of nutrients can be more easily identified and mitigated when compared with non-point sources, which are often harder to recognize. Tidal creeks are small coastal tributaries that ex ist in the transitional zones of open estuaries like Sarasota Bay and its terrestria l uplands (Janicki Environmental Inc. 2011). These creeks transport freshwater and nutri ents from the watershed to the bay. Being that they are at sea-level, these creeks are dominated by intertidal fluctuations and therefore do not contribute as much stormwater runo ff as do creeks that originate above sea-level. Vegetation such as red and white mangro ves are often found in less developed areas along the creeks, while submerged aquatic veg etation, such as seagrass, is normally absent. A variety of species, many of economic val ue, e.g., species of mullet ( Mugilidae ), blue crab ( Callinectes sapidus ), and red drum ( Sciaenops ocellatus ) inhabit tidal creeks in southwest Florida. The full ecolog ical roles of these creeks are not yet fully understood, but it is known they contribute t o the environment in many ways, serving as a habitat for many juvenile species and a source of primary production. Nutrients from the surrounding watershed enable the se habitats to flourish, therefore it has been suggested a numeric nutrient criteria for the tidal creeks of Sarasota Bay is
needed to ensure the functions and overall health o f Sarasota Bay are maintained (Janicki Environmental Inc. 2011). Kaneohe Bay Kaneohe Bay (Figure 3a) is a coral reef and estuar ine ecosystem located on the island of Oahu, Hawaii (Hunter and Evans 1995). Se t against the Koolau mountain range, it is the largest bay in the Hawaiian island chain, at approximately 13.5 km in length and surrounded by 30.7 km of shoreline (Figu re 3b). The Koolau volcano was one of two large shield volcanoes that formed the i sland of Oahu approximately three million years ago (Rowland and Garcia 2004). The v olcano was once 2,000 meters tall, but severe erosion has weathered it down to around 1,100 meters today. Combined, the watersheds surrounding Kaneohe Bay equal an area of 97 km2 (Hunter and Evans 1995), and include the Kaneohe, Heeia, Kahaluu, Kaalae a, Watahole, Waikane, and Hakipuu/Kualoa watersheds (State of Hawaii: Office of State Planning 1992). Native Hawaiians lived along the bay in subdistricts (ahup uaa), cultivated taro, and created fishponds around the bay until western contact and diseases spread throughout the late 1800s and diminished their populations. Land use was changed around the beginning of the 20th century, when rice and pineapple plantations were established. The bay and surrounding watersheds have been subjec ted to many human derived land use changes, such as agriculture and grazing a ctivities, and later, extensive urbanization (Hunter and Evans 1995). One of the f irst large human impacts on the bay occurred around the Second World War when coral ree fs were widely dredged, especially in the southern portion of the bay (State of Hawaii : Office of State Planning 1992). In just two decades, between 1940-1960, the area of Ka neohe experienced a 450%
population increase, from 5,387 to 29,622 people (H unter and Evans 1995). With this large increase of population came intensive develop ment, i.e., building of roads and additional housing. This development has subjected the bay to increased nutrient loads, increased siltation, sewage discharges, and other t ypes of impacts (Banner 1974). In 1977 and 1978, municipal and United States Marin e Corps military base sewer discharges were diverted from the bay (Smith et al. 1981). The subsequent effects on the bay ecosystem indicated the rate of productivity wa s beyond the rate of nutrient loading, but after the sewage was rerouted, the excess bioma ss of plankton and benthic organisms quickly fell. In addition, there was a large decre ase in turbidity and nutrient levels in areas that had been affected by the sewage outfall (Hunter and Evans 1995). These rapid improvements in water quality and coral reef health in Kaneohe Bay demonstrate the ability the ecosystem has to rebound from anthropog enic stress. Although sewage is not being directly released into the bay anymore, other non-point sources of anthropogenic stress still exist in the form of excess nutrients and sedimentation from runoff and erosion. The proximity of the Kaneohe Bay reef to land means that it will always be influenced by land runoff, both natural and anthrop ogenic. Since the World War II era, large-scale urbanizatio n and increased populations have encroached upon the Kaneohe watershed (Banner 1974). Today, the bay is surrounded by an intense and urban residential, com mercial, and industrial landscape (State of Hawaii: Office of State Planning 1992). In the area between the southern and central portion of the bay lies Coconut Island, hom e to the University of Hawaii Institute of Marine Biology. The military has a base on the Mokapu Peninsula of Kaneohe Bay and uses sections of the bay area as an air field.
Kaneohe Bay supports the only barrier coral reef in the archipelago (Hunter and Evans 1995). Over the years it has experienced man y natural disturbances, such as freshwater flooding and runoff from erosion. The s hallow topography and limited tidal exchange of the bay causes water circulation to be compromised throughout, restricting water flow and allowing for heightened anthropogeni c effects (Banner 1974). The extent to which each watershed affects the bay depends on how much of the water enters the bay, rainfall events, and amount of pollutants pres ent. The majority of urbanization is located near the southern region of the watersheds, where water circulation is especially limited, contributing to greater impacts in that ar ea (Hunter and Evans 1995). Towards the northern end of the bay, there is less urbaniza tion and more natural streams, as opposed to channelized ones in the south (State of Hawaii: Office of State Planning 1992). Nine perennial streams border the shoreline of Kaneohe Bay, providing an influx of freshwater to near shore areas and reducing sali nity (Figure 3c) (Hunter and Evans 1995). Purpose of the Study I compared Sarasota Bay, Saraosta, Florida and Kane ohe Bay, Ohau, Hawaii because though there are very different geologic an d regional differences, the two locations have other factors that are strikingly si milar. Both experienced dramatic increases in population density, with primarily urb an and residential areas bordering their coastal ecosystems. The populations are estimated to be 51,917 for Sarasota and 34,597 for Kaneohe (U.S. Census Bureau 2010). Additionall y, both locations began experiencing heavy development in the early to mid20th century that compromised their off-shore ecosystems, though they have since reboun ded when major anthropogenic
effects were been realized and mitigated ( Sarasota Bay Estuary Program 2010, State of Hawaii: Office of State Planning 1992). This study had two main goals. First, I investigat ed if there was a change in nutrient concentration downstream near the mouth of a bay compared to further upstream in the watersheds of both Sarasota and Kaneohe. I also pooled all downstream sites and all upstream sites within each location to establis h variability of nutrients regarding distance from the bay. I hypothesized that concent rations of nutrients would be greater in upstream sites, where land use is affecting water q uality. Second, I examined total amounts of nutrients between Sarasota and Kaneohe t o determine if there were differences between their nutrient levels. I hypot hesized that because the two areas have similar history, development, land use, and populat ion size, levels of nutrients would be comparable.
Materials and Methods Locations: Hawaii I collected water samples from streams that flowed into Kaneohe Bay, Ohau, Hawaii [212433 N, 1574757 W] seven times from December 2011 to January 2012 during the rainy season. The six different samplin g locations included three upstream sites, Keneke Street, Alaloa Street, and Kaneohe Ma rket, and three corresponding downstream sites, Kauhale Beach Cove, Fishpond, and Holowai Street, respectively (Figure 3, Table 1, Appendix 1). Site Descriptions Approximately 2.25 km upstream from Kaneohe Bay was the Keneke Street site (Figure 4a) located in the Kamooalii Stream, a trib utary of the Kaneohe Stream. At this location, Kamooalii Stream was approximately five m eters below street level and five meters wide, with concrete slopes that have been bu ilt along either side of it, and a small walking bridge (Figure 4b) above the collection sit e. Small amounts of vegetation, namely grass and weeds, grew on either side of the stream bank. The area surrounding the stream was residential. The Holowai Street site was located downstream from the Keneke Street site, approximately 165 meters upstream from where the Ka neohe Stream joined Kaneohe Bay (Figure 5a). At this location the stream was a round 32 meters wide. The banks were grassy and lined with rocks, with water level appro ximately one meter below (Figure 5b). Water was always calm at this site with little to m oderate flow. The surrounding area was residential on the north side of the bank where water was collected, with a golf course nearby on the south side.
n The Alaloa Street site (Figure 6a) was located upst ream along the Heeia Stream beside Alaloa Street, approximately 1.6 kilometers upstream from Kaneohe Bay. The stream was approximately 15 meters wide at this loc ation, with concrete slopes approximately six meters in height lining it and a wide bridge for vehicular traffic (Figure 6b). Dense amounts of grass, trees, and bushes gre w on the banks and in various parts inside the stream, and animals such as ducks, chick ens, pigeons, and pigs were spotted frequently. The area was surrounded primarily by h ouses with a school and mall located several blocks away. The Fishpond site (Figure 7a) was downstream from t he Alaloa Street site, located along Kamehameha Highway and situated appro ximately 110 meters from where the Heeia Stream encountered Kaneohe Bay. The wate r was collected under a low highway bridge, approximately one meter in height, and was very stagnant, showing little to no movement (Figure 7b). Raw animal parts were dumped here about halfway through sampling and still remained at the conclusion of th e study. Many trees grew alongside and into the water, and the banks surrounding the c ollection site were sandy. The Kaneohe Market site, (Figure 8a) located upstre am along the Keaahala Stream approximately 1.15 kilometers upstream from Kaneohe Bay, was under a bridge adjacent to the busy Kamehameha Highway. The strea m was approximately six meters below street level and five and a half meters wide, lined with tall concrete walls (Figure 8b). Water was collected by lowering a water colle ctor into the stream, which often had trash in it. In the immediate surrounding neighbor hood there were shops, businesses, restaurants, and residential areas.
The Kauhale Beach Cove site (Figure 9a) was downst ream and located where the Keaahala Stream joins Kaneohe Bay, adjacent to a ma rina. Water was sampled near a small fishing dock (Figure 9b) and alternated betwe en being calm or turbulent from day to day. On several occasions yard work was taking place close to the testing site, and people were often fishing or hanging out on the doc k. The surrounding area consisted of a gated apartment community. Locations: Florida I collected water samples from streams that flowed into Sarasota Bay, Sarasota, Florida [272011 N, 823150 W] 15 times from Fe bruary 2012 to March 2012 during the dry season. The seven different sampling locat ions included three upstream sites, the High School, 32nd, the Golf Course Bridge, and three downstream corr esponding sites, Selby Gardens, Whitakers Lane, and Westmoreland Str eet, respectively. A seventh site, Magellan Drive, was located between the Golf Course Bridge and Westmoreland Street sites (Figure 2, Table 2, Appendix 1). Site Descriptions Three sites were located along Bowlees Creek. The site farthest upstream on Bowlees Creek was the Golf Course Bridge site (Figu re 10a) located on the east side of Tamiami Trail in Bradenton approximately 1.8 kilome ters upstream from Sarasota Bay. On Magellan Drive, a bridge for one-lane traffic bo th ways was located about two meters above the creek, which was about 3 meters wide (Fig ure 10b). The testing site was on the south side of the bridge, surrounded by a golf course. Downstream, on the north side of the bridge, the area was primarily residential. The water at the testing site was easily accessible from either bank. The east bank consist ed of a sandy slope while the west
bank was lined with a small wall, about half a mete r tall. Dead fish were sometimes seen in the water. The Magellan Drive site (Figure 11a) was also locat ed upstream on Bowlees Creek on the east side of Tamiami Trail in Bradento n, approximately 940 meters upstream from Sarasota Bay. A short seawall surrou nded both sides of the creek as well as trees and other vegetation (Figure 11b). Access ible from Magellan Drive, the area adjacent to the testing site was residential, and m any houses along the water had docked boats. The Westmoreland Street site (Figure 12a) was loca ted the furthest downstream on Bowlees Creek on the west side of Tamiami Trail in Bradenton, approximately 270 meters upstream from Sarasota Bay and 40 meters wid e. The testing site was on an empty lot on Westmoreland Street, which was residen tial with a seawall on the south side of the creek, while the north side of the creek was less developed with a partial mangrove shoreline (Figure 12b). Water level was approximat ely one meter below street level, and boats and pelicans were often seen here. Near the end of testing, much of the excess vegetation in the empty lot was removed. The 32nd Street site (Figure 13a) was located upstream on W hitaker Bayou on the east side of Tamiami Trail in Sarasota, approximate ly 1.8 kilometers upstream from Sarasota Bay. The bayou, about five meters across, ran between streets and had large grassy slopes on either side that droped off steepl y to the water about five meters below street level (Figure 13b). Fish of varying sizes a s well as dead fish were usually seen here. The area was residential.
The Whitakers Lane site (Figure 14a) was located d ownstream on Whitaker Bayou on the west side of Tamiami Trail in Sarasota approximately 200 meters upstream from Sarasota Bay and 60 meters across. The area s urrounding the site was upscale residential with some newly built houses. Water wa s collected on the south side of the bank, and both sides of the bank had a seawall and sported many docks and boats (Figure 14b). Directly east of the site was a small boatya rd where boats were often being lifted in and out of the water. Small groups of pelicans for aging were always seen here. The High School site (Figure 15a) was located next to Tamiami Trail past downtown Sarasota, upstream on Hudson Bayou, approx imately 1.4 kilometers upstream from Sarasota Bay. The width of the bayou here was about two meters across, and water flowed about two meters below street level. The si des were lined with a grassy slope and vegetation that shaded the bayou (Figure 15b). Tra sh was always seen at this site. The area consisted primarily of businesses, with a muse um and high school nearby. The Selby Gardens site (Figure 16a) was located dow nstream on Hudson Bayou just south of downtown Sarasota, and was approximat ely 340 meters upstream from Sarasota Bay and 85 meters across. The site was on the north side of the bayou and surrounded by a grassy area outside of Selby Garden s. Both sides of the bayou had seawalls, with many docks and boats (Figure 16b). Water level was about one meter below ground level. Some mangroves grew in the wat er next to the testing site, and beside the gardens, the area was primarily resident ial. Measurements At each site environmental variables were recorded [water temperature (C), salinity (ppt), pH, conductivity, and total dissolv ed solids (TDS) (ExStik EC500, Extech
Instruments; refractometer, Spartan)] and water sam ples collected (water sampler (LaMotte) or a collection bottle). At the Florida sites, a turbidity tube (Carolina Biological Supply) was used to determine the turbid ity of the water. Rain gauges provided the amount of rain that occurred during ea ch sampling period. The gauges were mounted at sites in Hawaii: Keneke Street, Fishpond and Alaloa Street sites, and sites in Florida: 32nd Street, Whitakers Lane, Golf Course Bridge, Magell an Drive, and Magellan Drive sites. For each water sample collected, I measured ammonia nitrate, and phosphate in parts per million (ppm) using single parameter wate r kits (LaMotte), which included low range phosphate kit for brackish water and a high r ange kit for fresh water. Fecal coliform tests (Carolina Biological Supply) were pe rformed once for each Hawaii site in January 2012 and twice for each Florida site in Mar ch 2012. Data Analysis Nutrient data was analyzed using a one-way ANOVA wi th SPSS (IBM 2008) to determine the differences, if any, between nutrient data. The assumptions of this test are that all samples are normal and random, and that al l samples follow a normal curve. First, I investigated nutrient data associated with each set of sites (upstream and downstream) adjacent to both Kaneohe Bay and Saraso ta Bay, to see how nutrient levels changed at different points in the watershed along the same tributary. Second, the same procedure was used to examine how different all ups tream, and all downstream, sites were to one another, both in Kaneohe and Sarasota, to see if there was variability of nutrients higher in the watershed and lower in the watershed. Lastly, differences were assessed between each nutrient measured in Hawaii a nd each nutrient measured in
Florida to determine if levels of ammonia, nitrate, or phosphate were significantly higher in one location over the other. Statistics were ru n on additional parameters including salinity, distance of sites from bay, and rainfall.
Results Upstream VS Downstream One-way ANOVAs and confidence intervals with a sign ificance level of 0.05 were conducted to look for differences in nutrient amounts measured between each upstream and downstream set of sites in Hawaii (Tab le 3a) and Florida (Table 3b). Hawaii Means for all nutrients per site in Hawaii were det ermined (Figure 17) and compared between upstream and downstream sites (Fig ure 18). Analyzing the Hawaii sites, I found a significant difference between Ken eke Street (up) and Holowai Street (down) for nitrate ( F =5.33, P =0.04, 0.562 1.072), and Alaloa Street (up) and the Fishpond (down) for nitrate ( F =40.33, P =0.00, -0.046 0.108). In both cases, the upstream sites had significantly greater nitrate am ounts than the downstream sites. For all other sites, no significant difference was dete cted between nutrient levels. Comparing all upstream sites in Hawaii together, nitrate vari ed significantly ( F =12.40, P =0.00, 0.992 1.146) while phosphate and ammonia did not. All d ownstream sites were evaluated together, again nitrate varied significantly (F=28. 00, P=0.00, 0.562 1.072) but phosphate and ammonia did not (Table 4). Florida I examined the data to determine if there were diff erences for the Florida sites. Means for all nutrients per site in Florida were as sessed (Figure 19) and compared between upstream and downstream sites (Figure 20). One of the waterways, Bowlees Creek, had two upstream sites (Golf Course Bridge a nd Magellan Drive) instead of one. I compared these two sites for each nutrient first and found that phosphate was the only
nutrient with a significant difference, and therefo re I tested the sites individually against the downstream site (Westmoreland Street). Ammonia and nitrates did not show a significant difference between the two upstream sit es, so I grouped them together when comparing upstream and downstream nutrients on Bowl ees Creek. I found significant differences for phosphate betw een the Golf Course Bridge (up) and Magellan Drive (down) ( F =6.17, P =0.02, 0.129 0.331), the Golf Course Bridge (up) and Westmoreland Drive (down) ( F =48.81, P =0.00, 0.291 0.549), and Magellan Drive (up) and Westmoreland Drive (down) ( F =23.69, P =0.00, 0.129 0.331). There were also significant differences in phosphate levels between 32nd Street (up) and Whitakers Lane (down) ( F =38.71, P =0.00, -0.015 0.042) and the High School (up) and Selby Gardens (down) ( F =26.19, P =0.00, -0.015 0.042). No significant differences were detected for nitrate a nd ammonia for any of the sites (Figure 19). Comparing all upstream sites in Florida toget her, I found that phosphate varied significantly (F=5.29, P=0.00, 0.129 0.331) but ammonia and nitrate did not. All downstream sites showed no significant variation (T able 5). Hawaii VS Florida I conducted one-way ANOVAs to determine differences in collective nutrient amounts measured between Hawaii and Florida. Means for each nutrient were calculated per state (Figure 21). A significant difference wa s detected for phosphate ( F =19.85, P =0.00, -0.009 0.047), indicating that the mean amount of phospha te measured in Florida (0.28 ppm) is significantly greater than th e mean amount of phosphate measured in Hawaii (0.02 ppm). I found that the amount of a mmonia measured in Florida (0.29 ppm) and in Hawaii (0.3 ppm) were not significantly different ( F =0.01, P =0.98, 0.16
0.427). Interestingly, the mean amount of nitrate measured in Hawaii (0.57 ppm) was significantly greater than the mean amount of nitra te measured in Florida (0.08 ppm) ( F =83.78, P =0.00, 0.448 0.707). Other Parameters The fecal coliform test was performed once in Hawai i and twice in Florida at each site, all of which gave negative results. Salinity evaluated between the downstream sites ( F =438.3, P =0.00, 1.055 6.088) and upstream sites ( F =40.32, P =0.00, 10.79 15.71) of Hawaii and Florida were significantly gre ater in Florida (Figure 22). The distances from upstream sites in Florida and upstre am sites in Hawaii to their respective bays were similar (Figure 23) and not significantly different ( F =0.25, P =0.64, 0.293 3.04), and although mean salinities in Florida dow nstream sites were higher than those in Hawaii, Florida downstream sites were significan tly farther from the bay than Hawaii downstream sites ( F =7.98, P =0.048, -0.117 0.3). Rainfall was variable between sites. In Hawaii, r ain gauges were placed at three sites, and in Florida, rain gauges were placed at f ive sites. Combining these measurements, the mean rainfall in Hawaii (n=16) wa s 0.21 mm while the mean rainfall in Florida (n=53) was only 0.07. The differences i n rainfall between bays was significant ( F =5.97, P =0.02, 0.87 0.323).
Discussion Present Nutrients and Other Parameters Throughout the study, the tributaries around Kaneoh e Bay showed significantly greater amounts of nitrate than the tributaries aro und Sarasota Bay (Figure 21). This may be due to successful wastewater treatment in Saraso ta (Kurz et al. 1999), which contributed to a 46% reduction in nitrogen loads be tween 1988 and 1990, though the loads are still above baseline conditions (Tomask o et al. 2005). As I was testing a primarily urban and residential environment in Sara sota, lawn fertilizers probably were greater factors than agricultural fertilizers. How ever, the two sites with the highest levels of nitrate (Golf Course Bridge and Magellan Drive) were both adjacent to the Sarasota Bay Country Club golf course, suggesting fertilizer s used there contributed to elevated nitrate levels (Figure 19). Hawaiian soils are initially poor in nitrogen cont ent, but are replenished constantly in the environment because the nitrogen is atmospherically derived (Chadwick et al. 1999). The three upstream sites in Hawaii ( Keneke Street, Kamehameha Market, and Alaloa Street) all showed higher levels of nitr ates than their downstream counterparts. Additionally, these upstream sites a re all channelized and surrounded by tall, concrete slopes which facilitates stormwater runoff from adjacent residences (De Carlo et al. 2007) (Figures 4, 6, and 8). Converse ly, the upstream sites in Sarasota had lesser and generally more natural slopes (Figures 1 0, 11, 13, and 15), which may facilitate absorption of nitrates before they reach the stream. Additionally, according to the Total Maximum Daily Load (TMDL) report for the Kaneohe/Kamooalii Streams, there are several total nitrogen and phosphorous no n-point sources of pollution within the
n Kaneohe watershed (Hawaii Department of Health Envi ronmental Health Administration 2009), including forested areas, agriculture, open water areas, the Koolau Golf Course, and the Veterans Memorial Cemetery. Rainfall is another important factor that contribu tes to nutrient enrichment. Mean rainfall around Kaneohe Bay was significantly great er than mean rainfall around Sarasota Bay. This distinction is probably due to differenc es between seasons. In Hawaii, the wet season is generally from December-February (Stearns 1983), and in Sarasota, the wet season is from May-October (Guentzel et al. 2001). Therefore the dates of my study coincide with the wet season of Hawaii, but not the wet season of Florida. The amount of rainfall received in each location is important, as it affects anthropogenic nutrient levels (Dillon and Chanton 2005). In subtropical island e nvironments, for example Oahu, there are pulses of fresh stormwater runoff that are prim ary pathways for non-point sources of pollution to enter aquatic environments (De Carlo e t al. 2004). Located on the wetter, windward side of the island, rainfall is particular ly prominent around the Kaneohe Bay area (Figure 24). Precipitation can also contribut e to the atmospheric deposition of nitrogen, as industry and combustion processes rele ase nitrogen into the air (Puckett 1994). In places that receive large amounts of rai nfall, this atmospheric source of nitrogen can be considerable. Though I did not sam ple immediately following any rainfall events, greater levels of nitrates in Kane ohe could have resulted from more frequent precipitation carrying atmospheric nitroge n, as well as transporting nitrogen to waterbodies through runoff. My results suggest that Sarasota Bay tributaries co ntain significantly greater phosphate levels than those in Kaneohe (Figure 21) which is probably due to geological
differences. The geologic history of Florida revea ls that large amounts of phosphorous naturally occur in Florida because ancient seas dep osited sediments rich in phosphorous millions of years ago through processes of precipit ation (Florida Industrial and Phosphate Research Institute 2010). Animal remains, in parti cular bones, also contributed to the formation of phosphorous. Mining of phosphorous in Florida dates back to the late 19th century, and today, phosphorous is heavily mined in Bone Valley, central Florida. Worldwide, 25% of the phosphorous used in fertilize r comes from Florida, and the value rises to 80% for the United States alone. Conversely, the Hawaiian Islands have a much differ ent geological history. The island of Oahu, where Kaneohe Bay is located, is se veral million years old, and, similar to the rest of the islands, was formed from volcani c activity (MacDonald et al. 1983). Chadwick et al. (1999) found that the older Hawaiia n Islands have lost rock-derived phosphorous used by plants through weathering and l eaching processes, thus lowering the biological availability of phosphorous. In fact, a s the island ages, greater amounts of available phosphorous are atmospherically deposited and derived from places like Asia rather than the parent lava rock, which was initial ly rich in phosphorous. Therefore, the area around Sarasota Bay likely contains larger amo unts of natural phosphorous than the area around Kaneohe Bay. As previously mentioned, rainfall is another factor that can have an effect on phosphate levels. Similar to nitrogen and other co ntaminants, phosphorus influxes can be tied to rainfall and stormwater events (Dillon and Chanton 2005). However, as rainfall was greater in Kaneohe, this parameter does not acc ount for the difference in phosphate levels between bays. I therefore conclude that the discrepancy in phosphate levels
between bays is probably the result of Florida havi ng much higher levels of naturally occurring phosphate than Oahu, Hawaii. Another nutrient I examined was ammonia, which had levels in Sarasota and Kaneohe that were nearly identical (0.29 ppm and 0. 3 ppm, respectively) and not significantly different (Figure 21). As a compound of nitrogen, it is curious that ammonia levels were so similar in both locations gi ven that nitrate levels were much higher in Kaneohe. However, this ammonia could be coming from sources such as motor vehicle exhaust, cleaning products, decomposition o f organic matter, and products made of glass, concrete, or paper (National Pollutant In ventory). I observed many of these types of sources that could contribute to total amo unts of ammonia, as all of my sites at both locations were primarily urban and residential The lack of results for the fecal coliform analysis may indicate levels were too low for the tests to be able to identify their pres ence. A U.S. Environmental Protection Agency (EPA) 2010 Water Quality Assessment Status r eport found all of Florida tributaries that were sampled in my study (Hudson B ayou, Whitaker Bayou, and Bowlees Creek) had fecal coliform listed as a source of imp airment (United States Environmental Protection Agency 2010). The report also listed Sa rasota Bay as impaired from fecal coliform, but the 1998 and 2002 reports did not lis t fecal coliform as a factor, indicating that fecal coliform had not been an important pollu tant in the bay for at least a decade prior to 2010. While the EPA does not identify a p robable source for the 2010 fecal coliform measurements, the disparity between report s suggests it is more of a recent occurrence in these tributaries. My tests may have not detected fecal coliform for a number of reasons, including reduced amounts in tho se waterbodies since the 2010
report, differences in the specific areas I was tes ting compared to those used in the report, differences in season affecting fecal coliform leve ls, and increased runoff in tributaries, i.e., possible dilution of fecal coliform. In the most recent EPA report for Kaneohe Bay, none of the tributaries included in my study (Heeia Stream, Kaneohe Stream, Kamooali i Stream, and Keaahala Stream) are listed as impaired for fecal coliform (United S tates Environmental Protection Agency 2006), though other areas in Kaneohe Bay are listed as impaired for Enterococcus bacteria (United States Environmental Protection Ag ency 2008). In the past, sewage input did have many ecological ramifications in Kan eohe Bay before it was diverted in the late 1970s (Hunter and Evans 1995), but does n ot appear to have a major presence in the bay today. Therefore, my results are suggestiv e of this ongoing trend of reduced levels of fecal coliform, although a new report is needed to assess the current conditions of these waterbodies. The average salinity in Florida (20.53 ppt) was muc h higher than in Hawaii (1.79 ppt) (Figure 22), suggesting the tributaries adjace nt to Kaneohe Bay are significantly less saline than those adjacent to Sarasota Bay. Distan ce of the sites from their respective bays (Figure 23) did not contribute to this dispari ty, because salinity levels were higher farther upstream in Florida than in Kaneohe. There fore the difference is likely due to susceptibility to flooding, elevated topography, an d increased rainfall in Kaneohe (Figure 24) compared to Sarasota (Figure 25). Additionally while I was sampling it was the rainy season in Hawaii and dry season in Florida, w hich could have contributed to differences in salinity as well.
The Kaneohe Bay watershed has a history of flooding because the area receives an average of 203.2 centimeters of rainfall every y ear (United States Society on Dams 2005) and has small drainage basins (Ringuet and Ma ckenzie 2005). To prevent flooding damage, the Flood Control Act of 1970 authorized a $25 million dollar project, which was completed by the Army Corps of Engineers in 198 1 (U.S. Army Corps of Engineers, Honolulu District 2005). This project included a d am and reservoir on the Kamooalii Stream, and provided Kaneohe Stream modifications a nd recreational park improvements. Since its completion, the project ha s saved millions of dollars in flood damages and is inspected yearly. Even so, Kaneohe Bay has since experienced storm floods, one of which occurred in late 1987 and caus ed a reef-kill when salinity in the bay fell to 15% in some areas (Jokiel et al. 1993). Ad ditionally, the amount of development that has occurred in Kaneohe Bay has likely led to more flash flooding events in its surrounding streams (State of Hawaii: Office of Sta te Planning 1992). While the initial influx of waters may create a pulse of nutrients, t he continual flow of water from rain and high mountains also keep salinity levels low. In comparison, the Sarasota area received approxim ately 127-152 centimeters of rainfall in 2011, substantially less than Kaneohe B ay receives (NOAA 2011). Furthermore, the topography of Florida is very flat which allows for salty bay waters to enter nearby tributaries. Adding to the salinity o f Sarasota Bay tributaries is saltwater intrusion into groundwater and reduced stream flows which are related to declines in Floridian aquifer water levels (Florida Department of Environmental Protection 2012). Differences between Upstream and Downstream Sites
In nearly all cases, nutrient levels upstream were greater than nutrient levels downstream (Figures 18 and 20). In Hawaii, two set s of sites (Keneke Street and Holowai Street, Alaloa Street and Fishpond) showed significantly greater amounts of nitrate upstream than downstream (Table 3a). For a ll other nutrients, differences between upstream and downstream were not significant. When comparing all Hawaii upstream sites to one another, and all downstream sites to o ne another, nitrate again was the only nutrient to show significant differences in both ca ses (Figure 18). In Florida, all sets of sites showed significantly greater levels of phosph ate upstream than downstream, but for all other nutrients, there was no significant diffe rence between upstream and downstream (Figure 20). When comparing all Florida upstream sites against one another, phosphate was the only nutrient to vary significantly (Table 3b). A comparison of all Florida downstream sites yielded no significant differences It is especially interesting to note that while Hawaii had significantly greater nitrate levels than Florida (Figure 21), there was a disparity between Hawaii nitrate concentratio ns, with the greatest levels occurring farthest from the bay. In Florida, phosphate level s were shown to be significantly greater than levels in Hawaii (Figure 21), with larger conc entrations of phosphate higher in the watershed (upstream) as well. The data suggests that greater levels of nutrients are concentrated further up in the watershed, and by the time the water makes its way to the bay, nutrient levels were lowered. This difference is due to processes withi n the watershed that can be physical, biological, or chemical (Hall Jr. 2003). It has be en found that the removal of forests can increase element exports, e.g., nitrates into water bodies (Likens et al. 1970) because of mineralization, soil nitrification, and limited nit rogen uptake by plant s (Likens et al.
1969). Bernhard et al. (2003) showed that in a New Hampshire watershed nitrate levels increased drastically in the years following vegeta tion damage, and subsequently, nitrates were removed in large amounts by processes within t he stream. Therefore, it is possible for streams to act as buffers for nutrient change c aused by disturbances or influxes of nutrients within the watershed (Bernhard et al. 200 3). Current Trends: Kaneohe Bay The corals and other organisms that inhabit the Kan eohe Bay ecosystem have experienced severe nutrient enrichment in the past from both point and non-point sources (De Carlo et al. 2007, Done 1992, Hunter and Evans 1995, Ringuet and Mackenzie 2005). Major point sources of nutrients, i.e., sew age outfalls, have been greatly reduced by efficient management and legislation (De Carlo e t al. 2007). Nonetheless, non-point sources still exist and are difficult to identify. The Hawaii State Department of Health considers Kaneohe Bay near-shore waters and tributa ries moderately to severely impaired. The Clean Water Act forHawaii specifies that TMDLs are needed for pollutants in impaired waterbodies to determine and maintain healthy water quality standards (Hawaii Department of Health Environmenta l Health Administration 2009). All streams I used as part of my study (Kaneohe/Kam ooalii, Heeia, and Keaahala Streams) are included in the 2006 EPA impaired wate rbody report for Oahu (Table 6) (United States Environmental Protection Agency 2006 ). However, Kaneohe/Kamooalii Streams are the only ones that have a completed and /or available TMDL report, but only for total nitrogen and total phosphorous. Today, coral diseases are an ongoing problem for Ka neohe Bay corals, especially the Montipora White Syndrome coral disease (Aeby et al. 2010). Corals suffer tissue loss
and higher susceptibility to this disease when stre ssed from high temperatures or poor water quality. Increases in algae in coral habitat acerbate this stress on corals. A State of Hawaii Department of Land and Natural Resources 201 0 news release revealed that new innovative solutions to rid Kaneohe Bay of invasive algae were showing success (State of Hawaii Department of Land and Natural Resources 201 0). These techniques involved a combination of manually removing algae, bringing in urchins to graze on algae, and using an underwater vacuum to suck up the algae. Current Trends: Sarasota Bay Although historical populations of seagrass have be en threatened, there has been improvement in Sarasota Bay water quality recently, attributed to successful reductions in anthropogenic nutrient loads, improving water quali ty and light penetration (Kurz et al. 1999). From 1988 to 2010, wastewater nitrogen load s decreased by 64% ( Sarasota Bay Estuary Program 2010), contributing to seagrass coverage increases of 7% (1988 to 1994) and then 11% (1994 and 1996) in Sarasota Bay (Kurz et al. 1999). According to the State of the Bay 2010 report by the Sarasota Bay Es tuary Program, coverage of seagrass has increased 24% above 1950 levels ( Sarasota Bay Estuary Program 2010) In the same areas I conducted my study, the Florida Department of Environmental Protection (2012) reported that seagrass coverage increased in upper Sarasota Bay from upgrades to wastewater treatment plants (Florida Department of Environmental Protection 2012). This shows how interconnected nutrient runoff is to the health of seagrasses in near-shore waters. At the moment, stormwater runoff is the largest sou rce of nutrient loads to Sarasota Bay (Tomasko et al. 2005). Nutrient loads vary strongly with rainfall and can
be at different levels depending on the season. Th is makes management practices hard in areas that have unpredictable rainfall, such as Flo rida. Although current seagrass levels are above historic levels, increases or pulses of n utrient loads drastically impact these types of ecosystems, therefore, seagrasses in Saras ota Bay should be studied in conjunction with rainfall patterns. All tributarie s included in this study are listed as impaired waterbodies by the 2010 EPA report, though nitrogen and phosphorus are not included (Table 7) (United States Environmental Pro tection Agency 2010). Even if not all nutrients are of primary concern, it is importa nt to maintain a monitoring program for water quality in aquatic ecosystems to identify if changes occur. Future Research and Development It is important that nutrient levels be continually monitored and sources of anthropogenic nutrient enrichment identified. Toma sko et al. (1996) suggested testing seagrasses directly provided a better indication of their health than testing for nutrients in water. The same assessments could be applied in ar eas with coral reefs and possibly other aquatic ecosystems as well. These options ma y be more costly than traditional water quality measurement techniques, but they prov ide more direct indications of ecosystem health. Low impact design, development, and upgrades to sto rmwater and sewage treatment plants in urban areas can reduce nitrogen phosphorous, and other pollutants into waterbodies (van Roon 2007). There are many d evelopment techniques that create more sustainable urban environments and at the same time reduce anthropogenic nutrient loads in bays and watersheds. For example, creatin g drainage systems, e.g., retention ponds and swales, for stormwater outfalls that do n ot lead directly into a stream or bay
reduces non-point pollution (Miller et al. 2006). These types of infrastructural retrofits have already been put into use around Sarasota Bay, e.g., Indian Beach/Sapphire Shores neighborhood. Problems and Improvements I believe there were several problems with my stud y that could have been addressed with additional time and resources. Firs t, twice as much data was gathered on the tributaries surrounding Sarasota Bay over Kaneo he Bay; it would have improved my analysis if I had been able to collect comparable d ata for Kaneohe Bay. I also would have liked to sample during rainfall events and/or sample stormwater runoff nutrient contents, as the literature discusses nutrient enri chment effects extensively. A year-long study would provide comparisons that could be made between nutrients present during wet and dry seasons of both bays. Lastly, as I onl y measured nutrient content in the water column, an analysis of pore water in sediment s taken at different points along a tributary would have revealed how many nutrients we re concentrated or trapped in the sediment. Other issues I had with my experimental design inv olved some of the materials being too subjective. Testing kits for nutrients r elied on matching colors on a scale, and it was often hard to determine what color most clos ely resembled each test. The turbidity tube was also problematic because on days without b right sunlight, visibility was not as good and turbidity always appeared higher than usua l. Additionally, the water meter I used could not be utilized in saltwater, so I could not compare parameters such as conductivity and total dissolved solids between Kan eohe Bay and Sarasota Bay sites.
n Conclusion My results indicate that tributaries around Sarasot a Bay and Kaneohe Bay both have measurable amounts of nutrients, but the major ity were located higher up in the watershed rather than closer to the mouth of the ba ys. Interestingly, there were significantly greater amounts of nitrates in Kaneoh e Bay watersheds, and significantly greater amounts of phosphates in the Sarasota Bay w atershed, suggesting these results are from geological and physical differences at both lo cations. Though levels of nitrates and phosphates differed, the amount of ammonia in each location was very similar, indicating that urban sources of ammonia occurred at comparabl e levels. Furthermore, greater nutrient levels were found higher in the watershed, but a nutrient by nutrient comparison revealed not all upstream sites had the same nutrie nt level. This finding indicates there is a relationship between waterbodies and adjacent lan d and its uses, e.g., the site adjacent to a golf course had some of the highest nutrient l evels. The health of a bay is dependent upon the health of its watersheds, which can be influenced by a number of factors. In areas where the majority of land use is in agricultural and farming use, it can be expected th at runoff from fertilizer and animal manure would contribute to the greatest sources of nutrients in the watershed (Puckett 1994). In areas receiving very high levels of rain fall, atmospheric deposition and stormwater runoff contribute as one of the biggest sources of anthropogenic nutrient enrichment. Impacts of precipitation, e.g., stormw ater runoff, are compounded in urban areas where much of the natural land has been repla ced with impervious surfaces (Tang et al. 2005). Bays across the United States, as we ll as around the world, have been subjected to the effects of anthropogenic nutrient enrichment in their adjacent watersheds.
Kaneohe Bay and Sarasota Bay both have been severel y impacted in the past from human activities and development along their coasts, whic h have compromised their near-shore coral reef and seagrass ecosystems. With further r esearch, improved technology, and better management, these ecosystems are making reco veries. Continued research and monitoring of anthropogenic nutrient enrichment is needed, not just for ecosystems experiencing dramat ic environmental and land use changes but also for ecosystems recovering from imp acts. For each individual system, point and non-point sources of nutrients need to be identified as and a management plan created unique to each situation. As the world bec omes more developed, especially in coastal areas, near-shore waters and ecosystems nee d to be increasingly protected.
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Table 1. Upstream and Downstream Sites in Hawaii Upstream Downstream Keneke Street Holowai Street Kaneohe Market Kauhale Beach Cove Alaloa Street Fishpond
Table 2. Upstream and Downstream Sites in Florida Upstream Downstream Golf Course Bridge Magellan Drive Magellan Drive Westmoreland Street 32 nd Street Whitakers Lane High School Selby Gardens
Table 3. Significant Values between Upstream and Do wnstream Sites 3a. HAWAII Nutrient Upstream Site Downstream Site Critical Val ues Confidence Interval Phosphorous Keneke St. Holowai St. None (means were 0) None (means were 0) Phosphorous Kaneohe Market Kauhale Beach Cove None (means were 0) None (means were 0) Phosphorous Alaloa St. Fishpond F =2.21, P =0.16 -0.074 0.303 Ammonia Keneke St. Holowai St. F =0.03, P =0.86 -0.033 0.637 Ammonia Kaneohe Market Kauhale Beach Cove F =0.64, P =0.44 -0.386 1.344 Ammonia Alaloa St. Fishpond F =0.1, P =0.76 0.1 0.383 Nitrogen Keneke St. Holowai St. F =5.33, P =0.04 0.562 1.072 Nitrogen Kaneohe Market Kauhale Beach Cove F =0.65, P =0.44 0.137 0.523 Nitrogen Alaloa St. Fishpond F =40.33, P =0.00 -0.046 0.108 3b. FLORIDA Nutrient Upstream Site Downstream Site Critical Val ues Confidence Interval Phosphorous Golf Course Bridge Magellan Dr. F =6.17, P =0.02 0.129 0.331 Phosphorous Magellan Dr. Westmoreland Dr. F =23.69, P =0.00 0.129 0.331 Phosphorous Golf Course Bridge Westmoreland Dr. F =48.81, P =0.00 0.291 0.549 Phosphorous 32nd St. Whitakers Ln. F =38.71, P =0.00 -0.015 0.042 Phosphorous High School Selby Gardens F =26.19, P =0.00 -0.015 0.042 Ammonia Golf Course Bridge Magellan Dr. F =0.8, P =0.38 0.135 0.32 Ammonia Golf Course Bridge & Magellan Dr. Westmoreland Dr. F =0.69, P =0.41 0.111 0.27 Ammonia 32nd St. Whitakers Ln. F =3.92, P =0.06 0.185 0.465 Ammonia High School Selby Gardens F =0.51, P =0.82 0.15 0.439 Nitrogen Golf Course Bridge Magellan Dr. F =0.55, P =0.46 -0.03 0.323 Nitrogen Golf Course Bridge & Magellan Dr. Westmoreland Dr. F =2.86, P =0.1 -0.034 0.092 Nitrogen 32nd St. Whitakers Ln. F =1.0, P =0.33 -0.034 0.092 Nitrogen High School Selby Gardens F =1.91, P =0.18 -0.049 0.225
Table 4. Comparison of Hawaii Sites: Critical Value s Sites Phosphate Ammonia Nitrate Upstream None (means were 0) F =0.25, P =0.79, -0.028 0.567 F =12.40, P =0.00, 0.992 1.146 Downstream F =2.21, P =0.14, -0.074 0.303 F =0.31, P =0.74, -0.033 0.637 F =28.00, P =0.00, 0.562 1.072
Table 5. Comparison of Florida Sites: Critical Valu es Sites Phosphate Ammonia Nitrate Upstream F =5.29, P =0.00, 0.129 0.331 F =0.88, P =0.46, 0.135 0.32 F =1.89, P =0.14, -0.03 0.323 Downstream F =0.50, P =0.61, -0.015 0.042 F =1.40, P =0.26, 0.111 0.27 F =0.05, P =0.61, -0.034 0.092
Table 6. Status of Impaired Waterbodies around Kane ohe Bay1 Location Nitrate/Nitrite Total Nitrogen Total Phosphorus Trash Turbidity Dieldrin Heeia Stream TMDL 2 needed TMDL needed None None TMDL needed None Keaahala Stream TMDL needed TMDL needed TMDL needed TMDL needed TMDL needed None Kaneohe Stream TMDL needed TMDL completed TMDL completed None TMDL needed TMDL needed Kamooalii Stream TMDL needed TMDL completed TMDL completed None TMDL needed None 1Source: U.S. Environmental Protection Agency (2006) Hawaii, Oahu Watershed, Water Quality Assessment and Total Maximum Daily Loads In formation. 2Total Daily Maximum Load (TMDL), a pollution level that is developed to restore waters that are impaired, indicates acceptable leve ls of pollution.
Table 7. Status of Impaired Waterbodies around Sara sota Bay1 Location Chlorophyll-A Fecal Coliform Mercury in Fish Tissue Dissolved Oxygen Bowlees Creek TMDL needed 1 TMDL needed TMDL needed None Whitaker Bayou (Tidal) TMDL needed TMDL needed TMDL needed TMDL needed Hudson Bayou (Tidal) None TMDL needed TMDL needed TMDL needed 1Source: U.S. Environmental Protection Agency (2010) Waterbody Report for Sarasota Bay, Water Quality Assessment and Total Maximum Dai ly Loads Information. 2Total Daily Maximum Load (TMDL), a pollution level that is developed to restore waters that are impaired, indicates acceptable leve ls of pollution.
Figure 1. Major processes of the biogeochemical ni trogen cycle. Red numbers represent fluxes and are in teragrams (Tg=1012 g) N/year. Soils and terrestrial organisms contai n organic nitrogen active in the cycle. Figure taken from Bloom 2010.
n Figure 2. Sampling sites in Sarasota Bay, Sarasota, Florida USA [272045 N, 823402 W]. Star with respective number represent the follo wing sites sampled: 1Westmoreland Street, 2Magellan Drive, 3Golf Course Bridge, 4 Whitakers Lane, 532nd Street, 6Selby Gardens, and 7High School. Map of the stat e of Florida taken from http://www.netstate.com/states/geography/mapcom/ima ges/fl_h.gif (accessed May 1, 2012). Map of the Sarasota area taken from the Sar asota Bay Estuary Program: State of the Bay 2010.
Figure 3. Sampling sites in Kaneohe Bay, Kaneohe, Hawaii USA [212630 N, 1574742 W]. Star with respective number represent the follo wing sites sampled: 1Fishpond, 2Alaloa Street, 3Kauhale Beach Cove M arina, 4Kaneohe Market, 5Holowai Street, and 6Keneke Street. Map of Oahu taken from http://hawaiianforest.com/journal/wp-content/upload s/2010/08/Oahu-Map-Mountains.jpg (accessed May 1, 2012). Map of the Hawaiian Island chain and Kaneohe area taken from De Carlo et al. 2007.
Figure 4. Keneke Street site in Hawaii. A: View o f the sampling site. B: The street, bridge, and sidewalk above the sampling site.
Figure 5. Holowai Street site in Hawaii. A: View of the sampling site. B: The grassy area around the sampling site.
n Figure 6. Alaloa Street site in Hawaii. A: View o f the sampling site. B: The street and bridge above the sampling site.
n Figure 7. Fishpond site in Hawaii. A: View of the sampling site. B: The street and bridge above the sampling site.
n Figure 8. Kaneohe Market site in Hawaii. A: View of the sampling site. B: The freeway and bridge above the sampling site.
n Figure 9. Kauhale Beach Cove site in Hawaii. A: V iew of the sampling site and marina. B: The dock next to the sampling site.
n Figure 10. Golf Course Bridge site in Florida. A: View of the sampling site. B: The bridge above the sampling site.
n Figure 11. Magellan Drive site in Florida. A: Vie w of the sampling site. B: The foliage around the sampling site.
nn Figure 12. Westmoreland Street site in Florida. A: View of the sampling site. B: The area surrounding the sampling site.
n Figure 13. 32nd Street site in Florida. A: View of the sampling s ite and bridge. B: The grassy slopes surrounding the sampling site.
n Figure 14. Whitakers Lane site in Florida. A: Vie w of the sampling site. B: The residential docks next to the sampling site.
n Figure 15. High School site in Florida. A: View o f the sampling site. B: The surrounding foliage by the sampling site.
Figure 16. Selby Gardens site in Florida. A: View of the sampling site. B: The surrounding bridge and houses by the sampling site.
Figure 17. Mean nutrients at all sites in Hawaii, with upstream and downstream sites marked. Nitrate and ammonia was measured at each s ite while phosphate was only detected at one site.
Figure 18. Means of nutrients upstream and downstr eam in Hawaii. Nitrate levels were higher in upstream sites while phosphates and ammon ia levels were greater in downstream sites.
Figure 19. Mean nutrients at all sites in Florida, with upstream and downstream sites marked. Ammonia was measured at all sites while ph osphate and nitrate were more variable.
Figure 20. Means of nutrients upstream and downstr eam in Florida. Levels of all nutrients were higher in upstream sites than downst ream sites, with phosphate levels showing the greatest difference.
Figure 21. Comparison of nutrient means between Fl orida and Hawaii. Nitrate levels were significantly greater in Hawaii, phosphate lev els were significantly greater in Florida, and ammonia levels were very similar.
n Figure 22. Comparison of salinity means between Fl orida and Hawaii. Sites in Florida had significantly greater levels of salinity, both in upstream and downstream sites.
Figure 23. Comparison of distances to respective b ays between upstream and downstream sites in Florida and Hawaii. In upstrea m sites, distance from the bay was slightly farther in Hawaii. In downstream sites, d istance from the bay was slightly farther in Florida.
Figure 24. Mean annual rainfall and watershed boun daries in Oahu, Hawaii. The east side of the island where Kaneohe Bay is located rec eives some of the highest levels of rainfall on the island. Source: De Carlo et al. 2004.
Figure 25. Florida average annual precipitation (19 71-2000). The area around Sarasota Bay receives medium amounts of rainfall when compar ed with the rest of the state. Source: PRISM Group and Oregon Climate Service, Ore gon State University. http://www.prism.oregonstate.edu/pub/prism/state_pp t/florida300.png (accessed May 3, 2012).
Appendix 1GPS coordinates for all sites Hawaii Site GPS Coordinates Keneke Street 212426 N, 1574806 W Alaloa Street 212526 N, 1574838 W Fishpond 212616 N, 1574843 W Kaneohe Market 212501 N, 1574805 W Kauhale Beach Cove 212504 N, 1574725 W Holowai Street 212441 N, 1574706 W Florida Site GPS Coordinates Magellan Drive 272503 N, 823419 W Golf Course Bridge 272508 N, 823353 W Westmoreland Street 272449 N, 823435 W Whitakers Lane 272112 N, 823301 W Selby Gardens 271935 N, 823222 W High School 271927 N, 823146 W 32nd Street 272150 N, 823236 W