Linking the dynamics of nutrient cycling and primary producers to hypoxia in the Forge River, Mastic, NY

Amanda M. Burson, Stephanie C. Talmage, and Christopher J. Gobler

As coastal human populations expand globally, adverse environmental impacts are being observed in estuaries. The Forge River in Mastic, NY, is a brackish riverine estuary that has gained recent attention due to reports of seasonal hypoxia and deaths of multiple marine species. A major cause of hypoxia can be eutrophication and anthropogenic nutrient loading. Research was conducted to understand the role of eutrophication and primary producers in the occurrence of hypoxic conditions of the Forge River ecosystem. Bi-weekly time series water sampling, light-dark respiration experiments, and a submerged water quality probe were used to collect information about the water column's physical structure, phytoplankton community biomass, diversity, productivity, and nutrient concentrations. Surveys and experiments were conducted to understand the role of Ulva lactuca in nutrient cycling and hypoxia in the Forge River. From 2006 - 2008, the Forge River experienced chlorophyll a levels exceeding 120 µg L-1 and ammonium levels peaked at levels 47.0 µM, nitrate levels at 20.0 µM, and phosphate at 4.50 µM through the summer months. Bottom waters of the Forge remained hypoxic and/or anoxic for extended periods of time during summer (i.e. several weeks during July and August). In April, Ulva abundance peaked with percent cover ranging from 45 - 97%. Ulva abundance then declined dramatically at all sites during the summer months and then displayed a minor increase peak in September and October (~2% coverage). The decline in Ulva abundance during summer occurred when temperatures exceeded 25ºC and when less light was unable to penetrate to the bottom of the water column due to high pelagic chlorophyll a levels. Experimental incubations demonstrated that decaying Ulva both released nutrients and contributed to oxygen consumption. Therefore, the seasonal decline in Ulva may supply regenerated nutrients to pelagic algal blooms and may directly and indirectly promote hypoxia in the Forge River.

Quantification of nutrient loads and their impact on cyanobacteria blooms in a hyper-eutrophic freshwater system, Lake Agawam, Southampton, NY, USA.

Matthew Harke, Tim Davis and Christopher Gobler

Nuisance cyanobacteria blooms have plagued Lake Agawam, Southampton, NY, for a number of years. Recent monitoring has shown that during May through October, blooms are dominated by Microcystis spp., and become nitrogen limited. Recent studies have found toxins produced by Microcystis spp. and other cyanobacteria within the lake and fish kills from low oxygen levels have also been documented to follow bloom crashes. Here we report on a nutrient budget constructed to quantify point and non-point sources for nutrients entering the lake to assist in guiding lake remediation efforts. Dissolved nitrogen was found to primarily originate from groundwater, a storm drain at the north end of the lake and benthic fluxes from sediments. Phosphorus inputs, both organic and inorganic, mainly originated from sediments. These findings suggest that remediation efforts should focus on relieving groundwater inputs but as this can often prove too costly or politically difficult, significant changes can be made by reducing storm water input and possible dredging of the lake bottom. Nutrient dilution experiments performed in 2007 demonstrated that reducing nutrients will not only reduce algal biomass, but may also yield a shift in the phytoplankton community away from cyanobacteria and toward non-blue green algal species. Since cyanobacteria blooms are the cause of many environmental problems in Lake Agawam, including fish kills, a focus on nutrient reduction should be a part of any future management plan for Lake Agawam.

The effect of water column circulators on algal blooms and water quality in Mill Pond, Watermill, NY

Timothy W. Davis and Christopher J. Gobler

Harmful cyanobacteria blooms have become common occurrences in some Long Island lakes to the ecological detriment of these systems. Because such blooms are often associated with poorly flushed waters, mixing surface waters with high densities of cyanobacteria to deeper waters with low light levels has been hypothesized to be a means of disrupting cyanobacteria blooms. The goal of this study was to compare the algal dynamics and water quality in Mill Pond, Watermill, NY, before (2005, 2006) and after (2007) the installation of Solar Bee water column circulators. Temperature, nutrient levels, and water clarity were not significantly altered by the introduction of the circulators, although the average dissolved oxygen concentration was significantly reduced (10.7 ± 2.28 mg L-1 to 7.62 ± 2.85 mg L-1; p=0.003; t-test; Table 1). While average chlorophyll a concentrations also decreased from 220.0 ± 92.95 µg L-1 to 64.1 ± 14.05 µg L-1, total concentrations of the cyanobacteria (based on phycocyanin levels) were unchanged. As such, the average phycocyanin:chlorophyll ratio increased from 0.37 ± 0.05 to 0.90 ± 0.33, suggesting an increase in the relative abundance of phycocyanin-containing cyanobacteria among the phytoplankton community. The composition of the cyanobacteria community was altered by the water mixers. In 2007, Microcystis colony densities almost doubled (986 ± 253 to 1,816 ± 596 mL-1), Anabaena colony densities decreased slightly (< 10%), while Aphanizomenion colony densities were dramatically reduced to nearly undetectable levels (1,416 ± 673 to 1 ± 1 colonies mL-1; p< 0.001; Mann-Whitney rank sum). In sum, increasing vertical water circulation alone did not reduce blooms of cyanobacteria Mill Pond in 2007, perhaps due to its shallow nature (< 4 m). Since our prior research has demonstrated that nutrients stimulate cyanobacterial blooms in Mill Pond, remediation efforts which target nutrient reductions may have greater success in alleviating blooms.

The effect of tidal export from salt marsh ditches on estuarine water quality and plankton communities

Florian Koch and Christopher J. Gobler

Salt marshes are an important transition zone between terrestrial and marine ecosystems. In their natural state they often function to cycle or trap important natural and anthropogenic derived nutrients and pollutants. Many US east coast salt marshes, including those on Long Island, were ditched during the 20th century, potentially altering their function. The goal of this study was to assess the impact of water from salt marsh ditches across Long Island, NY, USA, on estuarine water quality. We found that concentrations of inorganic nutrients (ammonium, phosphate), dissolved and particulate organic nitrogen and carbon, and coliform bacteria were significantly enriched in salt marsh ditches compared to the estuaries they discharge into and became more enriched in ditches as tidal levels decreased. Quantification of nitrogen sources in Flanders Bay, NY, suggested salt marsh ditches could represent a substantial source of N to this estuary (6 - 20%). Bottle incubation experiments demonstrated that water from salt marsh ditches was capable of significantly enhancing the growth of multiple classes of phytoplankton, with large diatoms and dinoflagellates being the groups which displayed the most dramatic increases in growth. Experiments further demonstrated that salt marsh ditches were capable of significantly enhancing pelagic respiration rates, suggesting discharge from ditches could effect estuarine oxygen consumption. In summary, this study demonstrates that tidal draining of salt marsh ditches is capable of degrading multiple aspects of estuarine water quality.

The role of sulfide toxicity among other multiple stressors in Zostera marina populations in Long Island South Shore Estuaries

Konstantine Rountos and Bradley J. Peterson

Eelgrass (Zostera marina) has been declining in the south shore estuaries over the last several decades. This loss has affected many of the functions that this plant provides to the ecosystem. Like all plants, the primary limiting factors for growth and survival are sufficient light and nutrient availability. However, there are many areas of the south shore estuaries where neither of these are limiting and yet there is no eelgrass. This project explored the impact of sulfide toxicity and how reduced light (and hence photosynthesis) might compound this toxicity for eelgrass. A field survey of porewater sulfide was conducted in Great South Bay. In addition, both a manipulative laboratory and field experiment were conducted. The field survey demonstrated that there are many areas in GSB where the porewater sulfide concentration is above what has been found to be toxic to eelgrass. The laboratory experiment showed that productivity was reduced at the highest sulfide levels and that when present hard clams significantly increased productivity at the highest sulfide levels. The field experiment resulted in lowered productivity at the highest sulfide concentration and significantly reduced standing crop. The negative effects of sulfide were elevated when light availability was reduced.

The effect of nutrient loading and suspension-feeding bivalves on water quality and estuarine resources: eelgrass, juvenile fish, juvenile shellfish

Charles C. Wall, & Bradley J. Peterson, Christopher J. Gobler,

Long Island estuaries previously supported high densities of eelgrass (Zostera marina) and resource bivalves, such as hard clams (Mercenaria mercenaria), eastern oysters (Crassostrea virginica), and bay scallops (Argopecten irradians). Overfishing, eutrophication, harmful algal blooms, and habitat loss have all taken their toll on these populations, and many stake-holders would like to restore these resources to local waters. Recent changes in land use and wastewater treatment have reduced nutrient loading to these estuaries, but eelgrass and bivalve populations have not recovered. We conducted a series of mesocosm experiments to simultaneously test the effects of nutrient loading and historic suspension-feeder densities on the growth of eelgrass, juvenile bivalves, and juvenile fish (sheepshead minnow, Cyprinodon variegatus). High nutrient loading rates (above current management goals) led to higher chlorophyll a levels, lower water clarity, and increased growth of juvenile bivalves (hard clams and oysters) relative to controls with low nutrient loads (ambient waters). Filtration by adult suspension-feeders (M. mercenaria) decreased chlorophyll a levels, increased water clarity and the growth of eelgrass, but significantly decreased the growth of juvenile bivalves and fish relative to controls with no filtration from adult suspension-feeders. These results suggest that either nutrient loading or bivalve filtration or both have the capacity to structure estuarine food webs and affect the recovery of estuarine resources. Ecosystem-based approaches will need to account for both anthropogenic nutrient-loading and bivalve restoration to successfully manage our estuaries.

Estimating impacts of power plant water withdrawal on fish populations: Developing a novel Bayesian approach for calculating entrainment mortality
Santiago Salinas and Stephan B. Munch

The Indian Point and Northport power plants withdraw enormous volumes of water from nearby river and estuarine habitats throughout the year with the potential to heavily impact fish populations through entrainment and impingement. To estimate the impact of entrainment mortality on the local fish populations we collected larvae at fourteen stations near each power plant from June through October 2007. To analyze these data we developed a Bayesian population dynamics model that accounted for both natural and entrainment mortality. We applied this modeling framework to data for Bay anchovy from the Hudson river and estimate that approximately 11 million larvae were killed by entrainment. Although large, this number likely reflects only about 1% of the initial population of Bay anchovy in the Hudson.

2006/2007 Research Projects

The effect of salt marsh ditches on estuarine water quality
By Florian Koch and Christopher J. Gobler

Salt marshes are an important part of coastal ecosystems, representing critical habitats and serving as filters for terrestrially-derived nutrients and contaminants. Due to the threat posed by mosquito born-illnesses, salt marshes lining many northeast US estuaries have been drained of their standing water by "ditching" for nearly a century. This activity can accelerate the flow of water through salt marsh and to neighboring estuaries via tidal exchange. The future of salt marsh ditches remains an open question, as there are plans to re-excavate ditches which have filled in via sedimentation, as well as plans to restore marshes via "plugging" of the ditches (e.g. marsh reclamation project in Accabonac Harbor, East Hampton). The objective of this study was to establish flux rate of nutrients (especially nitrogen) from ditched marshes adjacent to Flanders Bay (western Peconic Estuary) and in Accabonac Harbor and determine the impact of exported ditch water on estuarine phytoplankton communities. Through the summer of 2006, ditches in Flanders Bay and Accabonac Harbor contained significantly higher levels of total dissolved nitrogen (57 ± 14 M and 27 ± 4.7 µM) then adjacent estuarine waters in each system (21 ± 2.7 M and 14 ± 4.0 µM; p < 0.05). The tidal draining of the ditches accounts for a flux of >1,100 moles of N per day into Flanders Bay and > 450 moles of N per day into Accabonac Harbor, suggesting ditch drainage may be a major source of N to each system. Experimental incubations demonstrated the ability of ditchwater to significantly (p < 0.05) enhance phytoplankton biomass and growth rates in both estuarine systems. Pigment analysis indicated that ditch water specifically increased the growth of larger phytoplankton, such as diatoms and dinoflagellates, in Accabonac Harbor. In Flanders Bay, these additions yielded enhanced growth of all major phytoplankton groups, including those implicated in the formation of harmful algal blooms (HABs). Managed plugging of salt marsh ditches in either system will decrease N fluxes, contributing toward the Peconic Estuary's Comprehensive Management Plan to minimize N loads.

Effects of once-through cooling on fish populations
Professor Steven Munch and Santiago Salinas

Electric and nuclear power plants withdraw large volumes of water from rivers and estuaries every year. This water, used for cooling of the system, teems with eggs and larvae, which are entrained and often killed by the water pumps. Entrainment could then be another hurdle to recovery for declining fish populations. This focus area of SCERP will estimate the number of fish and biomass that would have reached adulthood had entrainment not occurred. Several demographic and modeling approaches will be used (adult equivalent loss, fecundity hindcast, empirical transport model) to determine power plants' impact to a variety of commercially and/or ecologically important species. Population abundances and number of entrained larvae, necessary inputs to the models, will be assessed through in-situ plankton net sampling

Toxic blue green algal blooms on Long Island: Problems and potential solutions.Timothy W. Davis and Christopher J. Gobler

Cyanobacteria or blue green algae are a common family of photosynthetic organisms which can produce natural biotoxins. During the past 4 years, the aim of this study has been to: 1. Assess the presence of toxic cyanobacteria in lakes located in Suffolk County, 2. Assess factors that promote these blooms, and 3. Assess methods which might be employed to alleviate bloom occurrence. All twenty lakes sampled contained potentially toxic cyanobacteria (typically Microcystis sp.) and detectable levels of the hepatoxin made by cyanobacteria, microcystin. Fifteen of the lakes had levels of microcystn exceeding levels permissible for drinking water according to the World Health Organization (WHO). Fortunately, Suffolk County residents use these systems for recreation, not potable water, and levels of toxin in 15 of the 20 lakes sampled were below levels considered to be a low recreational risk by the WHO. However, the remaining four lakes (Lake Agawam, Old Town Pond, Mill Pond, and Lake Ronkonkoma) all posed moderate-to-high risks to human health for recreation at various times during the study. Each system hosted elevated densities of multiple species of toxic cyanobacteria (up to 106 cells ml-1) and high levels of microcystin (up to 15 mg L-1) and, in some cases, anatoxin-a (up to 1 µg L-1). All of these systems except Lake Ronkonkoma are hypereutrophic, with high levels of nitrogen and phosphorus, suggesting a relationship between nutrient loading and bloom occurrence. In 2006, Mill Pond and Lake Agawam continued to have spectacular blooms, with levels of microcystin which far exceeded levels which represent a moderate recreational risk. Since incubation experiments with natural communities have demonstrated that nutrient loading can enhance the biomass and toxicity of these two systems lakes. This suggests watershed management plans to restrict nutrient loading could serve to limit the severity of toxic blooms. A final aspect of this project was to quantify toxic and non-toxic densities of Microcystis and to compare these densities to levels of microcystin. These results that toxin levels tracked densities of toxic sub-populations rather than total cell densities, indicating quantification of these populations may be more valuable that

In 2007, two approaches will be tested as methods for reducing the occurrence of toxic blue green algae blooms. One approach, to be employed by the Mill Pond Homeowners association, will be the installation of water circulators which will push surface dwelling cyanobacteria to the bottom of the lake, potentially preventing bloom occurrence. The second approach will be a theoretical test of nutrient reductions in Lake Agawam. A nutrient budget will be constructed to determine the primary sources of nutrients to this system which should be targeted for reductions. In addition, experiments will be conducted to assess what impact nutrient loads will have on algal blooms.

The facilitation of seagrass (Zostera marina) productivity by suspension-feeding bivalves in an experimental setting.
Charles C. Wall, Christopher J. Gobler and Bradley J. Peterson

Seagrasses and suspension feeders are both critical ecosystem engineers in estuaries. Seagrass beds are important structural habitats and suspension feeders, when abundant, can control phytoplankton densities. Furthermore, there may be mutual facilitation of growth and recruitment between seagrasses and suspension-feeding bivalves. In a series of mesocosm experiments, the effects of environmentally realistic densities of three different suspension-feeding bivalves (Mercenaria mercenaria, Crassostrea virginica, Mytilus edulis) on the growth of eelgrass (Zostera marina) in a eutrophied environment were examined. Experimental treatments with bivalves consistently had significantly lower chlorophyll a concentrations (p < 0.05), and most bivalve treatments also showed significant increases in light penetration (p < 0.05). Eelgrass growth was measured by leaf area productivity, and varied from 0.318 ± 0.018 cm2 shoot-1 d-1 to 0.832 ± 0.036 cm2 shoot-1 d-1 (mean ± SE); leaf area productivity was always significantly higher in the treatments with the highest density of bivalves compared to a control without bivalves (p < 0.05). The data indicate that clearance of the water column and the subsequent increase in light penetration was the primary mechanism by which suspension-feeding bivalves facilitated the growth of eelgrass. This finding has important implications for the conservation of estuarine seagrass habitats and shellfish populations, specifically suggesting that healthy populations of suspension-feeding bivalves can serve as a control on estuarine eutrophication and can help restore degraded, light-limited seagrass habitats.

Eutrophication in the Forge River Estuary
Amanda Burson and Christopher J. Gobler

As coastal human populations expand globally, adverse environmental impacts are being observed in estuaries. The Forge River in Mastic, NY, is a brackish riverine estuary that has gained recent attention due to reports of seasonal hypoxia and deaths of multiple marine species. A major cause of hypoxia can be eutrophication, which in turn can be stimulated by anthropogenic nutrient loading. During 2006, research was conducted to understand the role of eutrophication in the hypoxic conditions of the Forge River water column. Bi-weekly time series water sampling, spatial cruises, light-dark respiration experiments and a submerged water quality probe were used to collect information about the water column's physical structure, phytoplankton community biomass, diversity and productivity and nutrient concentrations. The Forge River experienced chlorophyll a levels exceeding 400 µg L-1 and dissolved inorganic nitrogen concentrations at >100 µM through the summer and fall months. Bottom waters of the Forge remained hypoxic for extended periods of time during summer (i.e. several weeks during July and August). Phytoplankton communities included several potentially harmful dinoflagellate species including A. sanguinea, P. minimum and P. micans. Light-dark respiration experiments indicated the water column was net heteritrophic, meaning oxygen consumption strongly outweighed production in the Forge River. This is likely caused by the great abundance of heterotrophic dinoflagellates and bacteria and is a factor in the hypoxic conditions observed throughout the summer. A reduction in nutrient concentrations in the Forge may ease the occurrence of algal blooms and improve bottom oxygen levels in the Forge River.

Can hard clams (Mercenaria mercenaria) ameliorate anthropogenic light stress for eelgrass (Zostera marina ) through increased nutrient availability?
John Carroll, Christopher J. Gobler, Bradley J Peterson

Eelgrass, Zostera marina, is a critical habitat in many estuarine systems, providing refuge from predation and nursery grounds for many commercially important fin and shellfish species. Positive interactions have been studied between seagrass and bivalves, including hard clams, Mercenaria mercenaria, often indicating the importance of grass to bivalve survival and growth. However, the coastal lagoons which make up the Long Island South Shore Estuaries (LISSE) have seen precipitous declines in both hard clam stocks and eelgrass. This study examined the distribution of seagrass and environmental characteristics along two bays of the LISSE, Shinnecock and Quantuck. A total of 81 randomly selected sites were chosen throughout the two bays, where the benthic plant community was surveyed, eelgrass standing crop was sampled, sediment cores were removed and hard clam densities were assessed. Concurrently, an in situ fertilization experiment was run at two light levels with the addition of a commercial fertilizer or a hard clam. In the survey, eelgrass was found at only 11 surveyed sites with a mean 65.4 ± 62.7 grams dry weight/m2. Hard clam stocks were estimated to be very low, 0.77± 1.03 clams/m2 over the whole study area. However, in the manipulative experiment, hard clams were shown to significantly increase leaf area productivity (cm2SS-1d-1) in shaded plots (p<0.001), indicating that clams are able to ameliorate light stress for eelgrass. These findings demonstrate a need for recognizing and understanding positive interactions in coastal marine ecosystems as they may be critical to restoring these systems.

Burrow Competition Between the Native Fiddler Crab, Uca spp., and the Invasive Asian Crab, Hemigrapsus sanguineus.
Alexa Fournier and Bradley J. Peterson

Hemigrapsus sanguineus, the Asian shore crab, was first observed on the Atlantic coast of the United States in 1989 and has since spread from Nova Scotia to North Carolina, becoming the numerically dominant species in some rocky intertidal areas. Recently, it has been observed outside of its native habitat, in salt marshes on Long Island (NY) using algae and fiddler crab burrows for shelter. The use of Uca burrows by the invasive, non-burrowing crab may have an effect on the burrowing activity of Uca crabs, which in turn could affect salt marsh functioning. Laboratory experiments were performed to examine potential competition for burrows between the native fiddler crab ( Uca pugnax and U. pugilator) and H. sanguineus. Preliminary results indicate that H. sanguineus does compete with Uca and is able to displace an established crab from its burrow. Often, Uca showed aggressive behaviors toward H. sanguineus (claw waving, repeated approaches to the burrow), yet only once in this study was a fiddler crab able to re-take its burrow by ejecting the Asian shore crab. These findings suggest that the expansion of H. sanguineus into the salt marsh may cause changes in the burrowing activity of Uca spp.
Because Uca burrowing is known to influence primary production in the salt marsh, the expansion of H. sanguineus into the salt marsh could have wide-ranging effects on this ecosystem.

The effects of increased temperature and bioturbation on porewater sulfide concentrations in Great South Bay (NY) sediment.
Konstantine Rountos and Bradley J. Peterson

The effects of increased temperature and presence of bioturbators ( Mercenaria mercenaria ) on sulfide (?H2S) production in natural manipulated sediments was assessed in a 14-d laboratory experiment. We hypothesized that increased temperature and absence of hard clams would promote increased porewater sulfide concentrations (z = 0-1, 5-6, 14-15 cm). Forty-eight microcosms were filled with sediments collected in close proximity to Zostera marina (eelgrass) beds near Fire Island, Great South Bay (GSB) NY. Microcosms were randomly assigned to treatments of glucose enrichment (high, medium, low), molybdate (presence/absence), hard clams (presence/absence), and temperature (ambient/+4°C ambient). Three sediment perfusers filled with glucose, filtered seawater, or molybdate were added to sediments to create high (HG), medium (MG), low glucose (LG), and molybdate (MB) treatments. Glucose was used
to stimulate microbial sulfate reduction in sediments producing sulfides, molybdate was used to inhibit sulfate reduction. Twelve microcosms in both ambient and +4°C ambient temperature treatments received 3 hard clams (shell length = 25mm), producing 16 different treatments of 3 replicates each. Microcosms were exposed to a 10hr light - 14hr dark photoperiod and were sampled weekly using porewater sipper devices to extract porewater at the desired depths. Porewater was analyzed for total sulfide and total Fe concentrations colorimetrically using a UV spectrophotometer. The influence of multiple stressors (sulfide toxicity, habitat modification, increased temperature) on eelgrass survival in GSB has not been adequately assessed. This research provides insight into sulfide dynamics in GSB sediments for a future comprehensive eelgrass field experiment.

Characterization, dynamics, and ecological impacts of harmful Cochlodinium polykrikoides blooms on eastern Long Island, NY, USA.
Christopher J. Gobler, Dianna L. Berry, Amanda Burson, Florian Koch, Brooke S. Rodgers, Lindsay K. Moore, Jennifer A. Goleski, Bassem Allam, Yingzhong Tang

We report on the emergence of Cochlodinium polykrikoides blooms in the Peconic Estuary and Shinnecock Estuary, NY, USA, during 2004 - 2006. Blooms occurred during late summer when temperatures and salinities ranged from 20-25°C and 22-30 ppt, respectively. Bloom patches achieved cell densities exceeding 105 ml-1 and chlorophyll a levels exceeding 100 µg L-1, while background bloom densities were typically 103 - 104 cells ml-1. Light, scanning electron and ultrathin-section transmission electron microscopy suggested that cells isolated from blooms displayed characteristics of C. polykrikoides and provide the first clear documentation of the fine structure for this species. Sequencing of a hypervariable region of the large subunit rDNA confirmed this finding, displaying 100% similarity to other North American C. polykrikoides strains, but a lower similarity to strains from Southeast Asia (88-90%). Bioassay experiments demonstrated that 24 h exposure to bloom waters (> 5 x 104 cells ml-1) killed 100% of multiple fish species (1-week old Cyprinodon variegates, adult Fundulus majalis, adult Menidia menidia) and 80% of adult Fundulus heteroclitus. Microscopic evaluation of the gills of moribund fish revealed epithelial proliferation with focal areas of fusion of gill lamellae, suggesting impairment of gill function (e.g. respiration, nitrogen excretion, ion balance). Lower fish mortality was observed at intermediate C. polykrikoides densities (103 - 104 cells ml-1), while all fish survived for 48 hr at cell densities below 1 x 103 cells ml-1. The inability of frozen and thawed-, or filtered (0.2 µm)-bloom water to cause fish mortality suggested that the thick polysaccharide layer associated with cell membranes and/or a toxin principle within this layer may be responsible for fish mortality. Juvenile bay scallops (Argopecten irradians) and American oysters (Crassostrea virginica) experienced elevated mortality compared to control treatments during a nine-day exposure to bloom water (~5 x 104 cells ml-1). Surviving scallops exposed to bloom water also experienced significantly reduced growth rates. Moribund shellfish displayed hyperplasia, hemorrhaging, squamation, and apoptosis in gill and digestive tissues with gill inflammation specifically associated with areas containing C. polykrikoides cells. In summary, our results indicate C. polykrikoides blooms have become annual events on eastern Long Island and that bloom waters are capable of causing rapid mortality in multiple species of finfish and shellfish.

2005 Research

Effects of Tidal Discharge from Salt Marsh Ditches on Estuarine Ecosystems By Tanya Reisenauer

Although salt marshes are critical habitats in coastal ecosystems, anthropogenic activities threaten the natural function of these systems. For nearly a century, 'ditching' of salt marshes has been undertaken to reduce standing water and mosquito populations in salt marshes. This practice concurrently accelerates the flow of salt marsh water to neighboring estuaries via tidal exchange. The objective of this study was to establish flux rates of nitrogen and fecal coliform bacteria from salt marsh ditches to estuaries and to determine the impact of salt marsh ditch water on the growth of estuarine phytoplankton communities. Mosquito ditches contained high levels of nitrogen (> 100 µM) and fecal coliform bacteria (>2,000 per 100 ml). The draining of mosquito ditches in Flanders Bay likely accounts for a flux of > 1,200 moles of N per day and thus represents ~25% of the N load to the southern portion of the bay and nearly 10% of the N load to the entire bay. Partial and complete plugging of these ditches can reduce these N fluxes by 50 - 100%. Experiments demonstrated that ditch water is capable of enhancing phytoplankton growth rates, in general, and the growth of harmful algae (i.e. Aureococcus anophagefferens , Heterosigmna akishiwo, Prorocentrum minimum) in particular. As such, mosquito ditches are a source of N and fecal coliform bacteria which can degrade water quality in estuaries such as Flanders Bay. Since the plugging mosquito ditches can effectively eliminate ditch flow, such a practice seems warranted in ecosystems such as the western Peconic Estuary where the primary goal of the estuary's Comprehensive Management Plan is to minimize N loads to this region.
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Eelgrass Growth Dynamics as a Function of Nutrients Availability and Light Limitation in the Long Island South Shore Estuary By Sara Petrochic

Eelgrass (Zoatera marina) meadows are important ecological habitats that act as sediment stabilizers, nursery grounds, and food sources for many marine organisms. Unfortunately, eelgrass meadows have declined worldwide in temperate estuaries in recent years. This study looked at how nutrients ease the stress of shading, one possible reason for this decline. By marking and collecting grass, and measuring leaf morphometrics from infield experimental quadrants with differing levels of light and nutrients, we determined that increased nutrients can ameliorate the stress of shading. Nutrients added by natural sources, such as bivalves, are significant enough to increase productivity and leaf area in both shaded and non-shaded areas. Therefore, adding clams or other bivalves could be one way to slow the decline of seagrass meadows.
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An assessment of the environmental factors that promote toxic cyanobacteria blooms in various Suffolk County lakes

By Timothy Davis and Jennifer Goelski

Cyanobacteria or blue green algae are a common family of photosynthetic organisms which can produce natural biotoxins. The aim of this study was to assess the presence of toxic cyanobacteria in lakes located in Suffolk County and to assess factors which promote these blooms. Of the dozen lakes sampled, all contained potentially toxic cyanobacteria (typically Microcystis sp.) and levels of the hepatoxin, microcystin, which exceeded levels permissible for drinking water by the World Health Organization (WHO). Fortunately, Suffolk County residence rely on these systems for recreation rather than drinking water, and 8 of the 12 lakes sampled were below the levels considered to be a low recreational risk by the WHO. However, the remaining four lakes monitored (Lake Agawam, Old Town Pond, Mill Pond, and Lake Ronkonkoma) all posed moderate-to-high risks to human health for recreation at various times during the study. Each system hosted elevated densities of multiple species of toxic cyanobacteria (up to 106 cells ml-1) and high levels of microcystin (up to 1 mg L-1) and, in some cases, anatoxin-a (up to 1 µg L-1). All of these systems except Lake Ronkonkoma are hypereutrophic systems, with high levels of nitrogen and phosphorus, suggesting nutrient loading may be promoting bloom occurrences. Incubation experiments with natural communities confirmed this hypothesis, demonstrating that at various times, nutrient loading enhanced the biomass and toxicity of these lakes. Such a finding suggests watershed management plans to restrict nutrient loading could serve to limit the severity of toxic blooms. The finding that warmer temperatures enhance cyanobacteria biomass suggests that future global warming may increase bloom duration and intensity if nutrient levels remained unchecked.
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The ameliorating effects of the hard clam Mercenaria mercenaria on eelgrass Zostera marina during experimental algal blooms By Molly Fox

A series of mesocosm experiments were conducted to evaluate the potential for hard clams to increase light levels for eelgrass productivity. Throughout all experiments, there was an increasing trend of increased eelgrass productivity in mesocosms with hard clams verses those without. Statistical analysis did not reveal significant differences in eelgrass productivity. However, there were clear trends in the reduction of the larger phytoplankton by the hard clams. Mesocosms with and without clams were visibly different from each other by day 4 of all of the experiments. In those mesocosms that had clams, the bottom of the mesocosm was visible, while it was not in those that lacked them. The first set of experiments did not partition the chlorophyll by size fraction. The second and third set of mesocosm experiments did. The subsequent phytoplankton partitioning revealed that the larger sized phytoplankton was significantly reduced in the clam treatments. However, it appeared that the high water temperatures that were present for the second experiment reduced the hard clam grazing rates and thus their effect on the eelgrass. The third set of experiments was conducted in late September and the lower light at that time resulted in lower eelgrass productivity in both treatments, making a statistically significant difference unachievable. Despite the lack of statistical significance for these experiments, the strong trend in the second experiment supports the original hypothesis that hard clam grazing can enhance eelgrass productivity through increasing water transparency.
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The occurrence and ecology of harmful algae in the tributaries and estuaries of eastern Long Island By Colleen Norman and Brian Gibbins

Harmful phytoplankton represent a serious threat to coastal aquatic resources, and to date, but the documentation of these events in eastern Long Island estuaries has been limited. This study was designed to historically examine the types of phytoplankton which have been present in the brackish Peconic River, and to closely examine the dynamics of phytoplankton in multiple tributaries on eastern Long Island in 2005. A secondary goal was to examine the potential role of nitrogen and vitamins in promoting the occurrence of harmful algal bloom events. Examination of phytoplankton samples collected within the Peconic River from 2000 - 2005 indicated the presence of more than a dozen harmful phytoplankton species. Blooms were caused primarily by dinoflagellates which reached densities exceeding 106 cells L-1 and most commonly bloomed during late summer. Patterns among tributaries monitored were similar in 2005 with multiple harmful dinoflagellates forming blooms in August and September. Notably, a spectacular bloom of the red tide dinoflagellate Cochlodinium polykrikoides began in the Peconic River and Meetinghouse Creek in August and then spread throughout the Peconic Estuary in September, to the detriment of multiple species of shellfish. Observational and experimental data demonstrated that both nitrogen and organic vitamins play a key role in promoting these blooms. In summation, it seems that tributaries which have high nutrient loads may serve as incubators for the growth of harmful algae and are capable of seeding receiving estuaries with massive blooms via tidal exchange. As such, more careful monitoring and nutrient mitigation strategies in these tributaries are required to minimize the impacts of these blooms on east end estuaries.

Lindsey Rohrbach, class of 2005:Trace metal burdens in liver samples from seals stranded on Long Island, NY (1988-2004)

John Carroll, class of 2004: An assessment of the eelgrass, Zostera marina, populations in Shinnecock and Quantuck Bays, Long Island: limitations on growth

Jessica Lucchini, class of 2005:Hypoxia in the Peconic River Estuary and its effects on the benthic and pelagic community

Melanie Morin, class of 2005: Optimal conditions for automated fragment analysis of Zostera marina microsatellite PCR products

Brian Gibbins, class of 2005:Effects of pesticide application on Cyprinidon variegatus in a Salt Marsh ecosystem

Timothy W. Davis, class of 2004: Toxic cyanobacteria blooms on Long Island, NY

Patrick Curran, Class of 2004: Causes and impacts of anthropogenic eutrophication in the Peconic River Estuary, Long Island, NY

Laurie Mentzner, Class of 2003: Microsatellite diversity and fitness in stranded juvenile harp seals (Phoca groenlandica)

Ray Patelli, Class of 2003: Tracing the Movement of Water Through a Grid Ditched Salt Marsh

Matt Vilbas, Class of 2003: The Effects of Pesticide Application on Cyprinodon variegatus and Mysidopsis bahia in Salt Marsh Ecosystems

Michelle Weiss, Class of 2004: A Preliminary Study Assessing the Most Effective DNA Extraction Protocol for Zostera marina Populations Present in Long Island, NY Bays