2008/2009 Research Projects

A review of harmful algal blooms on Long Island in 2008: A bad situation worsens

Christopher J. Gobler, Ying Zhong Tang, Timothy W. Davis, Amanda Burson, Theresa Hattenrath, Elyse Walker

Harmful algal blooms (HABs) are serious threats to coastal ecosystems and economies. Long Island is an example of an increasingly common occurrence in the US: a coastline which is stricken by multiple HABs annually. The intensity, duration, and impacts of HABs can vary interannually, being influenced by changes climatic conditions and other factors. In 2008, Long Island had its worst year ever for HABs. For the first time in eight years, a brown tide broke out across all of Long Island's south shore. The bloom was record-setting with regards to timing (initiation in April), its intensity (> two million cells per ml), its geographic extend (from South Oyster Bay to Shinnecock Bay), and its durations (> eight months). A second, perhaps even more serious, HAB problem occurred from April through June in Northport and Huntington Bay on Long Island's northshore. An unprecedented Paralytic Shellfish Poisoning (PSP) event lead to the closure of more than 7,000 acres of shellfish beds due to lethal levels of toxin in shellfish. The PSP event was caused by an Alexandrium fundyense bloom which persisted for more than two months and achieved densities of more than one million cells per liter. At the same time, high levels of the PSP-producing dinoflagellate were also found on the south shore and east end of Long Island. In August and September, a Cochlodinium red tide event spread through all of the Peconic Estuary and eastern Shinnecock Bay. This species has been found to be highly toxic to fish and shellfish and during the bloom event, fishermen reported complete mortality of caged fish. In September, a dense cyanobacteria bloom occurred and crashed in Mill Pond, causing low oxygen levels and the death of more than 3,500 pounds of fish. Details of these events, their causes, and some solutions will be reported.

The effects of elevated carbon dioxide concentrations on the metamorphosis and survival of larval hard clams (Mercenaria mercenaria), bay scallops (Argopecten irradians), and eastern oysters (Crassostrea virginica)

Stephanie C. Talmage and Christopher J. Gobler

The combustion of fossil fuels during the past century has enriched levels of CO2 in the world's oceans, decreasing ocean pH and CO32- concentrations. The continuation of these changes this century will alter the growth, survival, and diversity of marine organisms which synthesize CaCO3 such as corals and calcifying plankton. In addition, net heterotrophy, freshwater discharge, and upwelling in coastal ecosystems can also lead to pelagic zones experiencing extended periods of high CO2. Here we present experiments which examined the metamorphosis, growth, and survivorship of larvae from three species of commercially and ecologically valuable shellfish (Mercenaria mercenaria, Argopecten irradians, and Crassostrea virginica) at the levels of CO2 projected to occur during the 21st century and beyond. Under CO2 concentrations estimated to occur later this century (~650 ppm), Mercenaria mercenaria and Argopecten irradians larvae exhibited dramatic declines (> 50%) in survivorship as well as significantly delayed metamorphosis. In contrast, Crassostrea virginica larvae were unaffected at these levels of CO2 but displayed diminished survival at CO2 levels expected next century (~1,500 ppm). These results demonstrate that larval stages of shellfish are extremely sensitive to enhanced levels of CO2 and future increases in pelagic CO2 concentrations may deplete and/or alter the composition of shellfish populations in coastal ecosystems.

Bathing beach and shellfishing water quality of Havens Beach, Sag Harbor, NY

Florian Koch and Christopher Gobler

Havens Beach in Sag Harbor, NY, is one of the villages most popular recreational summer bathing sites. A large ditch near Havens Beach receives road and groundwater drainage from a significant portion of Sag Harbor and this ditch discharges into Havens Beach during period of wet weather. The subsequent impact of this drainage on Havens Beach water quality is unknown. Beginning in the spring of 2008 an extensive sampling program was initiated to quantify levels of pathogenic bacteria in the ditch and the receiving waters of Havens Beach. Sampling occurred bimonthly and/or after significant rain events (>1") and was conducted at seven stations, three inside the drainage ditch and four extending into the receiving estuarine waters. Water quality was evaluated using two different bacterial indicators, Enterococci faecalis and Total Coliform (TC) bacterial abundance, which are the standards used by the Department of Health to open or close of shellfish beds and bathing beaches in New York State. Although bacterial densities were low during spring, during summer months, E. faecalis and TC bacterial abundances were often above regulatory limits (93% and 75% of samples respectively) for bathing beaches and shellfishing, respectively. Abundances decreased during the fall before reaching zero by winter. Correlations between temperature, rain events and water quality will be discussed.

Characterization of the toxicity of Cochlodinium polykrikoides isolates from NY estuaries to planktivorous fish and larval bivalves

Ying Zhong Tang and Christopher J. Gobler

Harmful algal blooms caused by Cochlodinium polykrikoides are annual occurrences in coastal ecosystems around the world although the precise mechanism of bloom toxicity is unknown. On Long Island, blooms have become an annual occurrence in the Peconic Estuary and Shinnecock Bay achieving cell densities exceeding 1,000 cells/mL with unknown consequences for marine resources. We report on the toxicity of Cochlodinium polykrikoides strains recently isolated from these estuaries to planktivorous fish and larval bivalves and on potential mechanisms of toxicity. Cochlodinium cultures caused complete fish mortality within ~1 h at densities as low as 300 cells/mL and >90% mortality of hard clam, bay scallop, and oyster larvae during 3-day exposures at 1,000 cells/mL. The toxic activity per Cochlodinium cell was dependent on the growth stages of cultures with early exponential growth cultures being more potent than cultures in late-exponential or stationary phases. The ichthyotoxicity was also dependent on cell density and fish size. Simultaneous exposure of fish to Cochlodinium and a second algal species increased survival time of fish, suggesting ichthyotoxicity depends on the relative abundance of Cochlodinium within the plankton. Cell-free culture medium connected to a culture through a 5um nylon membrane caused mortality in fish, although fish death time was significantly increased relative to direct contact indicating direct contact is not required for toxicity. The enzymes peroxidase and catalase significantly reduced toxicity of Cochlodinium, but hydrogen peroxide did not mimic the ichthyotoxicity of cultures, suggesting a non-hydrogen peroxide reactive oxygen or nitrogen species may be responsible for the toxicity of this species. It is concluded that annual blooms of Cochlodinium are likely to be adversely impacting Long Island fish and shellfish populations.

A quantitative budget of nitrogen sources, sinks, and remineralization in the Forge River, NY

M. J. Harke, R.L. Swanson, B. Brownawell, R.C. Aller, C.J. Gobler

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. Research was conducted to quantify the relative contribution of various nitrogen sources to the Forge River for the purposes of developing future management plans for this system. The supply of total nitrogen to the Forge River was estimated to establish the relative contribution of various sources to these systems. Nitrogen fluxes considered included atmospheric deposition, land run-off, diffusive groundwater seepage, tributaries, tidal exchange, burial, benthic fluxes, and the remineralization of Ulva lactuca. The largest in source of N to the Forge River is groundwater flow at 64% of the total N load (Table 2). This loading integrates N emanating from the entire Forge River watershed and thus includes cesspools and septic tanks within the watershed as well as commercial and residential fertilizer application. The second largest source of N to the Forge are tributaries (27% of load) with West Mill Pond being by far the largest at more than 72% of the load from tributaries (Table 2). Atmospheric deposition and surface run-off are both small sources of N to the Forge River representing ~3% and ~6% of the total N load to this system, respectively (Table 2). Benthic fluxes are a large source of N to the Forge, representing 40% of the total inputs however, this is considered a regenerated N sources as it ultimately emanates from land-derived N. Ulva lactuca is a small source of N (2% of input). However, the timing of this input may make it ecologically important to this system. It is suggested that addressing N inputs from West Mill Pond, groundwater, and sediments are likely to improve water quality in the Forge River.

Consumption of brown tide by the slipper shell snail, Crepidula fornicata
Matthew Harke, Sandra Shumway, Christopher J. Gobler

The American slipper limpet (Crepidula fornicata) is a protandrous hermaphroditic gastropod native to the Atlantic Coast of North America. One of the important characteristics of Crepidula that has led to its success is its remarkable ability to consume a vast array of particle sizes as small as 1 ?m in size. Populations of C. fornicata have expanded within certain embayments of the Peconics Estuary in Long Island, NY following the collapse of the bay scallop (Argopectin irradians) and the hard clam (Mercenaria mercenaria) due to recurrent brown tides (Aureococcus anophagefferens). Since the expansion of C. fornicata into the Peconics Estuary, brown tides have not recurred. However, brown tides continue to plague Great South Bay where historic populations of hard clam (once composing two out of every three hard clams eaten on the east coast) have not recovered despite a reduction in harvesting pressure. In this study, we quantified rates of suspension feeding by of C. fornicata and M. mercenaria in the presence of brown tide blooms and cultures. Our preliminary results suggest that C. fornicata can suspension feed during dense brown tides when M. mercenaria feeds at low rates.

Estimating impacts of power plant water withdrawal on fish populations: Developing a novel Bayesian approach for calculating entrainment mortality

Industrial power plants that withdraw cooling water from adjacent water bodies have the potential to entrain millions of fish larvae each year. We estimated icthyoplankton entrainment mortality for the Indian Point and Northport power plants. We monitored fourteen sites near each power plant over a four month period from April through August 2008. After identifying all species that were collected, we were able to estimate total abundance for Bay Anchovy, Stripped Bass, and White Perch. Over our sample period we found a decreasing trend in abundance for each species. As a first estimate of entrainment mortality we compared the rates of change in abundance for each station over time. After accounting for natural mortality, the differences in these rates of change can be attributed to entrainment mortality. Additionally, to obtain a more precise estimate of entrainment, we developed a Bayesian statistical analysis which explicitly accounts for both natural and entrainment mortality. This analysis assigned a probability to each possible entrainment level, based on the observed data. The results of these analyses and implications for future research efforts are discussed.

The growth of estuarine resources (Zostera marina, Mercenaria mercenaria, Crassostrea virginica, Argopecten irradians, Cyprinodon variegatus) across a naturally-occurring eutrophication gradient in the Peconic Estuary

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

While many coastal ecosystems previously supported high densities of seagrass and resource bivalves, the impacts of overfishing, eutrophication, harmful algal blooms, and habitat loss have contributed to the decline of these important resources. Anthropogenic nutrient loading that leads to eutrophication has been identified by some researchers as a primary driver of these losses, but other researchers have described potential positive effects of eutrophication on estuarine resources. The Peconic Estuary, Long Island, NY, USA, offers a naturally occurring nutrient loading gradient from eutrophic tidal creeks in the western region to mesotrophic bays in the eastern region. We conducted a five-month field grow-out experiment at four stations across this gradient to examine the effects of eutrophication on estuarine resources: eelgrasss (Zostera marina), juvenile bivalves (hard clams, Mercenaria mercenaria, Eastern oysters, Crassostrea virginica, and bay scallops, Argopecten irradians), and juvenile fish (sheepshead minnow, Cyprinodon variegatus). Water quality parameters were also monitored at the field stations. Hard clams grew maximally at the least eutrophic site, but did not display a consistent east-west pattern along the eutrophication gradient. Eastern oysters grew maximally at the most eutrophic tidal creek, but also did not have a consistent east-west pattern. Bay scallops displayed the only consistent east-west pattern: growth was always maximal at the least eutrophic sites and minimal at the more eutrophic sites. These results suggest that nutrient loading can have significant and complex effects on estuarine resource species, and that select species (e.g. oysters) may benefit from eutrophication under some conditions. Future ecosystem-based approaches that seek to restore estuarine resources will need to account for the differential effects of nutrient loading as managers target species and regions to be restored.

Environmental controls on eelgrass populations on Long Island
Brad Peterson