Long Island Sound Research Articles

Persistent Chlordane Concentrations in Long Island Sound Sediment: Implications from Chlordane, 210Pb, and 137Cs Profiles

Concentrations of chlordane, a banned termiticide and pesticide, were examined in recently collected surficial sediment (10 sites) and sediment cores (4 sites) in Long Island Sound (LIS). The highest chlordane concentrations were observed in western LIS, near highly urbanized areas. Chlordane concentrations did not decrease significantly in the past decade when compared to the data collected in 1996, consistent with the observation of near-constant chlordane levels in blue mussel tissues collected during the same time period. Chlordane concentrations in many of the sites exceeded levels above which harmful effects on sediment-dwelling organisms are expected to frequently occur. Chlordane concentrations in two of the four sediment cores showed a peak below the sediment surface, suggesting reduced chlordane inputs in recent years. The lack of a chlordane concentration maximum below the sediment surface in the other two cores, coupled with the lack of a well-defined 137Cs peak, indicated significant sediment mixing. Simulations of 137Cs and 210Pb profiles in sediment cores with a simple sediment-mixing model were used to constrain both the deposition rate and the bioturbation rate of the sediment. Simulations of the chlordane profiles indicated continued chlordane input to LIS long after chlordane was phased out in the U.S. Continued chlordane input and significant sediment mixing may have contributed to the persistent chlordane concentrations in surficial sediment, which poses long-term threats to benthic organisms in LIS.

A Decision Support Framework to Facilitate Nitrogen Load Reductions in Long Island Sound (LIS) Watershed

A Decision Support Framework to Facilitate Nitrogen Load Reductions in Long Island Sound (LIS) Watershed

Characteristics of Marine Aggregates in Shallow-water Ecosystems: Implications for Disease Ecology

Marine aggregates were evaluated for their potential role in the ecology of aquatic pathogens using underwater video surveys coupled with direct collection of aggregates in modified settling cones. Six locations, two each in New York, Connecticut, and Massachusetts, were surveyed over 8 months to explore differences in the characteristics of aggregates found in habitats populated by clams (Mercenaria mercenaria) and oysters (Crassostrea virginica). Microaggregate ( 500 μm) concentrations, but peak concentrations of macroaggregates and microaggregates, mean size of particles, and volume fraction of aggregated material varied among the six shallow-water habitats. Concentrations (colony-forming units per ml) of total heterotrophic bacteria (THB) and total mesophilic pathogenic bacteria (MPB) from samples of aggregates were significantly different among the four locations bordering Long Island Sound (LIS). The highest concentrations and enrichment factors in aggregates were observed in August for THB and in June for MPB. Significant correlations were detected for salinity and the concentrations and enrichment factors of THB in aggregates and for the concentrations and percentages of MPB in seawater samples. Significant correlations were also detected for temperature and the concentrations of MPB in aggregates and the enrichment factors for THB and MPB (marginal significance). Bacterial species identified in association with aggregates included: Vibrio cholerea, V. parahaemolyticus, V. vulnificus, V. alginolyticus, Aeromonas hydrophila, Pseudomonas aeruginosa, Escherichia coli, and Mycobacteria sp. These results have important implications for the way in which aquatic pathogens are collected, quantified, and monitored for risk-based surveillance in shallow-water ecosystems.

The behavior of natural and anthropogenic osmium in the Hudson River–Long Island Sound estuarine system

The extent to which riverine Os is trapped in a temperate estuary was the aim of this study. The behavior of Os through the Hudson River, East River and the Long Island Sound (LIS) system is addressed using both natural Os and anthropogenically mobilized Os. The Os concentration ([Os]) and isotopic composition ( 187Os/ 188Os) of the Mid-Atlantic Bight as inferred from the analysis of a water sample of 31‰ salinity (S) at Vineyard Sound, MA are 46 fM and 1.070, respectively. In comparison, the Hudson River at Newburgh, NY has [Os] = 68 fM and 187Os/ 188Os = 1.265. The Os concentration of the East River at the Whitestone Bridge is 51 fM and remains essentially constant proceeding eastward in the LIS despite the increase of salinity from 20‰ towards the higher value of the Mid-Atlantic Bight. The 187Os/ 188Os ratio of water at Whitestone Bridge is 0.945 and increases eastward through the Sound to 0.979 at 7 km and then to 1.019 at 39.6 km. The behavior of Os through LIS appears to be conservative at S > 20‰. On the basis of Os concentration and isotopic composition we infer that anthropogenic Os is being added to the East River through sewers with the likely isotopic ratio of ∼0.13 and that about 24% of riverine Os must be removed at S ⩽ 20‰. There is a net transport of about 0.4–1 mole of anthropogenic Os per year from the East River into the LIS. The residence time of Os in the ocean at present must be about 39,000 years, unless an independent source of supply of Os can be identified.

Lack of Enantioselective Microbial Degradation of Chlordane in Long Island Sound Sediment

Numerous studies have examined the enantiomeric compositions of trans- and cis-chlordane in soils (agricultural, background, and house foundation soils) and in the atmosphere. In contrast, little is known aboutthe enantiomeric compositions of chlordane in sediment. In this work, surficial sediments and sediment cores were collected at various sites in Long Island Sound (LIS) previously surveyed by the National Oceanic and Atmospheric Administration's (NOAA) National Status and Trends (NS&T) Program. Archived surficial sediments at selected sites were acquired from the NS&T Specimen Bank. The chlordanes were racemic or nearly racemic in most archived and recently collected sediments, indicating thatthe enantiomeric compositions of the sources of chlordane to LIS sediment did not change in the past two decades, and that house foundation soils are likely the major source of chlordanes to LIS. Invariant enantiomeric compositions temporally in surficial sediments and at different depths in sediment cores clearly indicate the lack of enantioselective biodegradation in LIS sediment, in striking contrast to the widely observed enantioselective biodegradation of chlordanes in soils.

Residual circulation in eastern Long Island Sound: Observed transverse-vertical structure and exchange transport

Residual currents in eastern Long Island Sound (LIS) are investigated using direct velocity measurements from an acoustic Doppler current profiler mounted on a ferry. Circulation at the site has major influence on exchange of water and water-borne materials between LIS and the coastal ocean. Ferry sampling enables sufficient averaging to isolate the residual motion from stronger tidal currents, and captures its spatial structure. Mean along-estuary currents based on about 2 years of sampling reveal a vigorous estuarine exchange circulation (peak 25–30 cm s −1 at depth), with flow eastward out of the estuary in the upper water column of the southern half and inward westward movement strengthening with depth over the central and north section. Application of volume conservation implies there is a strong eastward current out of the estuary in the shallowest 7 m where no measurements were made, as expected for estuarine exchange flow. Water from the Connecticut River, entering LIS on the north shore nearby to the west, does not appear to exit the estuary directly eastward along the north shore unless this occurs wholly in the shallow layer not sampled. Transverse currents have complex structure with generally northward (southward) flow where shallow outward (deep inward) motion occurs. An idealized semi-analytic solution for transverse-vertical structure of along- and across-estuary flow has limited success accounting for observed currents, despite inclusion of bathymetric, frictional, and rotational influences; this suggests the importance in LIS of dynamics it omits, in particular stratification, or does not represent with sufficient realism, such as complex bathymetry. Estimated annual-mean exchange volume transport, based on the better-sampled deep inward component, is 22,700±5000 m 3 s −1. This is comparable to previous estimates from some salt budget and hydrographic analyses, and implies advection contributes substantially to the total salt transport, contrary to results of a recent box-model analysis of hydrographic measurements. At seasonal timescales, changes to the transverse-vertical velocity structure are modest, but amplitude variations cause exchange volume transport increases (decreases) to 30,000 m 3 s −1 (18,000 m 3 s −1) in the summer (winter) months; a power-law dependence of exchange on river flow, as seen in other estuaries, is not supported. Strengthened summer transport is associated with enhanced stratification, suggesting that mixing effects modulate the exchange. To the extent that advection by residual flow contributes to total exchange between LIS and coastal waters, the flushing of materials from LIS should occur substantially faster in summer than in winter.

Nutrient limitation in the lower Housatonic River estuary

One of the most serious threats to freshwater and marine ecosystems is high rates of anthropogenic nutrient loading, particularly nitrogen (N) and phophorus (P). One of the major freshwater sources of nutrients to Long Island Sound (LIS) is the Housatonic River (HR). Current management plans that call for reducing N inputs without reducing P inputs may change the N: P ratio in the water column and the pattern of algal nutrient limitation and species composition in the tidal portion of the river. To assess the current pattern of algal nutrient limitation in the HR estuary, nutrient bioassays were conducted in spring, summer, and fall at 5 sites throughout the tidal portion and adjacent LIS. Diatoms were a dominant taxon at all sites throughout the sampling period. Other seasonally important taxa include cyanobacteria, cryptophytes, and euglenoids. Phytoplankton in LIS were always strongly N limited and were co-limited by P in spring. During low flow (summer), phytoplankton in the lower HR estuary were N limited. Phytoplankton in the middle reaches showed no evidence of N or P limitation and were likely limited by other factors. In spring, phytoplankton in the upper HR estuary were P limited. Periods of N or P limitation were better correlated with periods of lower concentrations of nitrate or phosphate than with differences in N: P ratio. These results suggest that decreases in N concentration could increase the prevalence of N limitation throughout the estuary that in turn may reduce phytoplankton biomass and alter species composition of the phytoplankton.

Bioaccumulation and Trophic Transfer of Methylmercury in Long Island Sound

Humans are exposed to methylmercury (MeHg) principally by consumption of marine fish. The coastal zone supports the majority of marine fish production, and may therefore be an important source of MeHg to humans; however, little is known about the bioaccumulation of MeHg in near-shore marine ecosystems. We examined MeHg in microseston, zooplankton, a decapod crustacean, and four representative species of finfish that differ in trophic status and/or prey selection in Long Island Sound (LIS), a large coastal embayment in the northeastern United States. MeHg biomagnifies in LIS; levels in microseston were 10(4.2) greater than those in water and 2.3-fold less than zooplankton. MeHg concentrations were related positively to fish length for each species, but often varied considerably among larger individuals. This may be due to differences in the past dietary MeHg exposure of these fish, some of which are migratory. Sedimentary production and mobilization can account for most of the MeHg in microseston of LIS, and by extension, other near-shore locations. Hence, much of the MeHg in higher trophic levels of coastal marine ecosystems, including fishes destined for human consumption, may be attributed to net sedimentary production and dietary bioaccumulation.

Optical determinations of suspended sediment dynamics in western Long Island Sound and the Connecticut River plume

The magnitude of beam attenuation attributed to suspended sediments, cp, and the slope of the log‐transformed attenuation spectrum, γ, were used to investigate the properties and dynamic nature of matter suspended in the waters of western Long Island Sound (LIS) and the adjacent Connecticut River plume (CRP). Within the LIS, cp and γ indicate a robust relationship between sediment concentration and particle size distribution (PSD). As concentration increased, the PSD shifted to larger particles. The highest concentrations and particle sizes were found in a nepheloid layer adjacent to the sound floor. Within the adjacent CRP, sediments were observed to shift towards smaller particles at the lateral plume boundary, where current shear stress may have disrupted large particle aggregates, relative to sediments in the more quiescent plume interior. A strong linear correlation between γ and salinity was also found, indicating that mixing between the two water masses may also have altered the PSD of the plume sediments. A suspended sediment attenuation model based on Mie theory, a power law form of the PSD, and a single sediment source indicates that the observed changes in LIS cp and γ are consistent with sediment removal as particles settle with size‐dependent rates. In contrast, within the CRP, the model supports the hypothesis that turbulence‐induced aggregate disruption at the lateral plume boundary is responsible for the observed variability in cp and γ. However, mixing between the LIS and CRP particle populations would violate the single source requirement of the model and necessitate a more complicated set of particle dynamics in order to correctly interpret the observed variability in particulate attenuation.

Nitrogen and silicon limitation of phytoplankton communities across an urban estuary: The East River-Long Island Sound system

To understand how nutrient loading may impact phytoplankton community growth, structure, and photosynthetic efficiency in Long Island Sound (LIS), nutrient enrichment (N, P, or Si) experiments were conducted at stations along the longitudinal gradient of the East River-Long Island Sound system during high and low river flow conditions (spring and summer). During summer, East River (ER) phytoplankton showed no response to N, P, or Si additions. In contrast, N enrichment significantly increased growth rates of all algal size classes (pico- (<3 μm), nano- (3–20 μm) and microphytoplankton (>20 μm)) and most major groups (dinoflagellates, diatoms) beyond control treatments in all regions of LIS (western, WLIS, central, CLIS and eastern, ELIS). Nitrogen enrichment also increased particulate organic carbon production and the photosynthetic efficiency of the phytoplankton community. During spring, ER phytoplankton remained nutrient replete, while larger phytoplankton (nano- and microphytoplankton; diatoms, dinoflagellates) within WLIS and CLIS algal communities were stimulated by N and/or Si additions (1.5- to 7-fold increased growth rates). An absence of response in ELIS phytoplankton following nutrient enrichment during spring together with elevated dissolved inorganic nutrients concentrations and river discharge rates suggests that seasonal variation in river flow can impact the degree to which ELIS phytoplankton are nutrient-limited. A 14-year record of nutrient concentrations and ratios in LIS suggested that our experimental results were representative of long-term seasonal trends, with N-limitation most likely to occur during the spring, summer, and fall in CLIS, during summer and fall in ELIS, and during late spring and summer in WLIS. The existence of low silicate levels relative to inorganic nitrogen in WLIS during spring months suggested that anthropogenic nutrient loading in this region may promote the seasonal Si-limitation of diatoms at this time.

Spatio‐temporal variation in serum chemistry of the lobster, Homarus americanus Milne‐Edwards

Monthly variations in serum chemistry of the American lobster, Homarus americanus Milne-Edwards, were investigated at one location in Long Island Sound (LIS). Comparisons between three locations within and outside LIS were also made for a single time point. Most serum analytes displayed significant fluctuation over the study period and between locations. Temporal patterns could be classified as: low in cool months/high in warm months, i.e. Na, Cl, Na:K ratio, Ca, albumin:globulin ratio, percentage Fe saturation; high in cool months/low in warm months, i.e. pH, K, urea, total protein, albumin, globulin, alanine aminotransferase (ALT), aspartate aminotransferase (AST), lipaemia; June spike, i.e. glucose, cholesterol, creatine kinase, iron, transferrin iron-binding capacity; other less obvious fluctuations, i.e. Mg, PO4; and no apparent fluctuation, i.e. HCO3, alkaline phosphatase. The proportion of samples correctly classified into month of collection by a subset of 13 analytes using discriminant analysis improved as the months progressed from May (0.75) to October (>0.95). Discriminant analysis also resolved 96.5% of samples by location. The significant depression of serum calcium at the eastern LIS site correlates with excretory calcinosis, a calcium storage disease described from lobsters at this site, but contrasts with a seasonal elevation in serum calcium recorded in the temporal component of the study. Serum proteins, the electrolytes Ca and K and the enzymes ALT and AST proved to have the strongest spatio-temporal patterns of variation. Serum chemistry is a useful research tool for lobster populations, but the dearth of information on the homology of analyte functions in this species with those in vertebrate species makes interpretation of the results challenging. Late summer/autumn water conditions appear to cause stress for lobsters in LIS.

THE CONTRIBUTION OF EGG-BEARING FEMALE AMERICAN LOBSTER (HOMARUS AMERICANUS) POPULATIONS TO LOBSTER LARVAE COLLECTED IN LONG ISLAND SOUND BY COMPARISON OF MICROSATELLITE ALLELE FREQUENCIES

Abstract In 1999, the massive die-off of the American lobster (Homarus americanus) populations in western Long Island Sound (LIS) caused complete collapse of the commercial lobster fishery. Reestablishment of a commercial fishery in western LIS requires, in part, knowledge of lobster populations that provide larvae to western LIS. To address this issue, larvae collected from sites within LIS were assigned to egg-bearing female lobsters by comparison of microsatellite allele frequencies. Egg-bearing female lobsters were collected from three sites within LIS and from a site in the Hudson Canyon (Crivello et al. 2005). Tissue samples were collected from female lobsters in spring, summer, and fall of 2001, and lobster larvae were collected in late summer of 2001 and 2002 from five sites within LIS. Differences in microsatellite allele frequencies were used to assign larvae to female lobster populations by a Bayesian and neural network approach. Larval assignments indicated that a high percentage (35% to 45%) ...

THE GENETIC STOCK STRUCTURE OF THE AMERICAN LOBSTER (HOMARUS AMERICANUS) IN LONG ISLAND SOUND AND THE HUDSON CANYON

The genetic population structure of the American lobster (Homarus americanus) was examined in populations collected in Long Island Sound (LIS) and the Hudson Canyon of the Northeastern United States with recently developed microsatellite DNA loci probes. Pereiopods, a thoracic appendage used for movement, feeding and defense, were collected from egg-bearing female lobsters from three sites within LIS—an eastern, central and western site—and from sites within the Hudson Canyon. Genomic DNA was isolated from each pereiopod and examined for nine microsatellite loci. Microsatellite allele frequencies, corrected for the presence of null alleles, were used to determine genetic differences between sampled groups. In agreement with earlier studies that used mitochondrial DNA and allozyme markers, there was little genetic differentiation between eastern and central LIS sites and the Hudson Canyon site. However, the genetic differences between western LIS populations and other sampled populations were 10 times higher. These were greater differences than could be attributed to geographical separation. These differences may have arisen as a result of the massive lobster die-off that occurred in 1998/1999 in western LIS.

EFFECT OF HABITAT BIOGEOCHEMICALS ON SURVIVAL OF LOBSTERS (HOMARUS AMERICANUS)

Abstract Lobsters from eastern Long Island Sound (LIS) were exposed to laboratory conditions designed to simulate the habitat in western LIS during the 1999 mass mortality. Elsewhere (Robohm et al. 2005) we have shown that hypoxia and concomitant biogeochemical conditions increase the susceptibility of lobsters to a common pathogen at normal summer temperatures. Here we report that in otherwise favorable conditions, high temperature (24°C) alone had no lethal effect on disease-free eastern LIS lobsters for weeks. However, at this temperature, moderate hypoxia (<2.5 mg/L dissolved oxygen) was lethal to half of a group (n = 20) of lobsters in about 5 days. Addition of sulfide and ammonium to levels reported for LIS (5.5 μM sulfide and 17 μM ammonium) decreased the LT50 to 3.3 days. Higher sulfide concentrations decreased the LT50 significantly. We conclude that lobster survival times are greatly diminished by hypoxia, sulfide and ammonium at high temperature. Because seasonal hypoxia with the production of ...

EFFECTS OF ENVIRONMENTAL STRESSORS ON DISEASE SUSCEPTIBILITY IN AMERICAN LOBSTERS: A CONTROLLED LABORATORY STUDY

Abstract The objective of this work is to determine whether increased (but environmentally realistic) temperature, hypoxia, sulfide and ammonium, alone or in combination, can increase susceptibility of lobsters to microbial infection. Lobsters from eastern Long Island Sound (LIS) were injected with Aerococcus viridans var homari, a pathogen that causes a disease known as gaffkemia. Injected animals (and controls) were placed in a flow-through seawater-system with mechanisms for control of temperature, dissolved oxygen, sulfide and ammonium levels as well as disinfection of effluent. Exposure variables included 0.1 mL injections of A. viridans at doses of 1 × 103 and 1 × 106; dissolved oxygen at 2.5–6.3 mg L−1; sulfide at 0–21 μM; ammonium at 0–80 μM and temperatures at 14.5 and 19.5°C. The criterion for stressor effect was the time at 50% survival in each set of 15 to 22 lobsters per treatment variable. Also, at regular time intervals, lobster hemolymph and hepatopancreas tissues were analyzed for bacteri...

NUCLEAR SMALL-SUBUNIT RIBOSOMAL RNA GENE-BASED CHARACTERIZATION, MOLECULAR PHYLOGENY AND PCR DETECTION OF THE NEOPARAMOEBA FROM WESTERN LONG ISLAND SOUND LOBSTER

Western Long Island Sound (LIS) lobsters collected by trawl surveys, lobstermen and coastal residents during 2000 to 2002 were identified histologically as infected with a parasome-containing amoeba. Primers to conserved SSU rRNA sequences of parasome-containing amoebae and their nonparasome-containing relatives were used to amplify overlapping SSU rRNA fragments of the presumptive parasite from gill, antenna, antennal gland and ventral nerve cord of infected lobsters. The consensus sequence constructed from these fragments had 98% or greater nucleotide sequence identity with SSU rRNA gene sequences of strains of Neoparamoeba pemaquidensis and associated with high confidence in distance- and parsimony-based phylogenetic analyses with strains of Neoparamoeba pemaquidensis and not members of the family Paramoebidae, e.g., Paramoeba eilhardi. Primers designed to SSU rRNA sequences of the lobster amoeba and other paramoebid/vexilliferid amoebae were used in a nested polymerase chain reaction (PCR) protocol to test DNA extracted from formalin-fixed paraffin-embedded tissues of lobsters collected during the 1999 die-off, when this amoeba initially was identified by light and electron microscopy and reported to be a paramoeba of the genera Paramoeba or Neoparamoeba (Mullen et al. 2004). All sequences amplified from 1999 lobsters, with the exception of one, had 98% to 99% identity to each other, and the 1999 PCR product consensus had 98% identity to Neoparamoeba pemaquidensis strains CCAP 1560/4 (AF371969.1) and 1560/5 (AF371970.1). Molecular characterization of the amoeba from western LIS lobsters by direct amplification circumvents a collective inability to culture the organism in vitro, provides insight into the molecular epidemiology of neoparamoebiasis in American lobster, and allows for PCR-based detection of infected lobsters for future research and diagnostics.

Interannual variability of temperature and salinity in shallow water: Long Island Sound, New York

Variabilities of temperature and salinity over Long Island Sound (LIS), New York, are examined using observations from 1991 to 2002. There is a strong seasonal variation in the temperature, and its interannual variability is characterized by a higher variance during winter than summer. The salinity exhibits regular seasonal patterns driven by freshwater input, but there is a long‐term change throughout LIS. Anomaly maps of temperature and salinity indicate strong longitudinal gradients increasing in the westward direction. Empirical orthogonal function analyses indicate that the first modes of temperature and salinity anomalies can explain 87% and 89% of the total variances, respectively. The first mode principle components of the temperature and salinity anomaly contain quasi‐biennial periodicities. The salinity anomaly also contains an additional signal at a decadal timescale. Seasonal variations in the temperature and salinity are primarily associated with heat flux and freshwater discharge. However, the surface heat flux anomaly only accounts for 17% of the total variance of the time rate change of the temperature anomaly, and the freshwater discharge anomaly explains 25% of the variance of the salinity anomaly. Contrary to traditional paradigm about estuaries, this result shows that forcings other than local processes control the interannual variabilities of the temperature and salinity in LIS, most probably through horizontal exchanges. Also, the significant correlation between the salinity anomaly and the Gulf Stream (GS) position suggests that the interannual variability of salinity in LIS is possibly connected to shelf slope water properties associated with changes in the GS position.

Dissolved Trace Element Concentrations in the East River−Long Island Sound System: Relative Importance of Autochthonous versus Allochthonous Sources

Dissolved trace metal (Ag, Cd, Cu, Fe, Ni, Pb, and Zn), inorganic nutrient (NO3, NH4, PO4, H4SiO4), and DOC concentrations were measured at 43 stations during low (July 2000) and high (April 2001) river discharge conditions in surface waters of Long Island Sound (LIS). To evaluate the impact of fluvial sources to the total metal budget of the sound, samples were collected from major tributaries discharging into LIS (Thames, Quinnipiac, Housatonic, Connecticut, and East Rivers). To compare LIS with other coastal embayments, samples were also collected from five LIS coastal embayments (Manhassett Bay, Huntington Harbor, Oyster Bay, Hempstead Harbor, and Port Jefferson Harbor), which are monitored by the U.S. National Status and Trends Program. Metal and nutrient distributions identified two biogeochemical regimes within LIS: an area of relatively high nutrient and metal concentrations in the East River/Narrows region in western LIS and an area in the eastern region of the sound that had comparatively lower concentrations. Mass balance estimates indicated that, during low flow conditions, the East River was the dominant allochthonous source of most trace metals (Ag, Cd, Cu, Ni, Zn) and inorganic nutrients (NO3 and PO4); during high flow conditions, the most influential source of these constituents was the Connecticut River. Mass balance estimates also evidenced a large autochthonous source of Cu, Ni, and Zn, as their spatial distributions displayed elevated concentrations away from point sources such as the East River. Principal component analysis suggested that metal and nutrient distributions in the LIS system were influenced by different seasonal processes: remobilization from contaminated sediments, anthropogenic inputs from sewage discharges and phytoplankton scavenging during the spring freshet, and benthic remobilization during summer conditions.

The structure of the coastal density front at the outflow of Long Island Sound during spring 2002

South of the eastern end of Long Island (Montauk Point) along the Eastern U.S. coast, a coastal density front forms between the buoyant outflow plume of the Long Island Sound (LIS) and the denser shelf waters offshore. During a 2-day cruise in April 2002, measurements of the density and velocity structure of this front were obtained from high-resolution CTD and ADCP data. Transects show the front intersecting the bottom inshore of the 30 m isobath and shoaling offshore. Variability in the location of the front is small offshore of the 40 m isobath, yet tidal excursions of the front along the bottom are significant (5 km) inshore of this depth. The frontal structure of the LIS plume was similar to observations of bottom-trapped coastal density fronts and shelf break fronts. A coastal jet in the along front direction was the main feature of the mean velocity field and was found to be in thermal wind balance with the mean density field. Stronger than expected offshore velocities near the surface, most likely a result of wind forcing, were the only exception to these similarities. In addition, analysis of temperature and salinity gradients along isopycnals gives evidence of secondary cross-frontal circulation and detachment of the bottom boundary layer. Characteristics of the LIS plume are used to evaluate recent analytical models of bottom-trapped coastal density fronts and bottom-advected plume theory, finding good agreement.

ACUTE TOXICITY OF RESMETHRIN, MALATHION AND METHOPRENE TO LARVAL AND JUVENILE AMERICAN LOBSTERS (HOMARUS AMERICANUS) AND ANALYSIS OF PESTICIDE LEVELS IN SURFACE WATERS AFTER SCOURGE, ANVIL AND ALTOSID APPLICATION

Abstract Acute toxicity and immune response, combined with temperature stress effects, were evaluated in larval and juvenile American lobsters (Homarus americanus) exposed to malathion, resmethrin and methoprene. These pesticides were used to control West Nile virus in New York in 1999, the same year the American lobster population collapsed in western Long Island Sound (LIS). Whereas the suite of pesticides used for mosquito control changed in subsequent years, a field study was also conducted to determine pesticide concentrations in surface waters on Long Island and in LIS after operational applications. The commercial formulations used in 2002 and 2003—Scourge, Anvil and Altosid—contain the active ingredients resmethrin, sumithrin and methoprene, respectively. Concentrations of the synergist piperonyl butoxide (PBO) were also measured as a proxy for pesticide exposure. Acute mortality in Stage I-II larval lobsters demonstrated that they are extremely sensitive to continuous resmethrin exposure. Resmeth...