East Coast Estuaries Research Articles

Dermal ulcerations and mortalities of estuarine fishes as indicators of environmental problems

Dermal ulcers appeared in young menhaden Brevoortia tyrannus in 1984. Field sampling showed dermal ulcers in this clupeid and in species of other families of fish from Delaware to Florida. Some mortalities were associated with the lesions. No definitive causative organism or process of lesion development was discovered and the disease was called Ulcer Disease Syndrome (UDS) by some investigators. Because various fungi were found in many of the sores, the disease was termed Ulcerative Mycosis (UM) by others. The epizootic waned around 1989–1990 as did political and scientific interest. Renewed attention, due to outbreaks of ulcers and mortalities of fish attributed to the toxic dinoflagellate Pfiesteria piscicida, revealed that UDS/UM had persisted in many East Coast estuaries. In North Carolina and Chesapeake's Pocomoke River, fish have died and some humans seem to have been affected. River closures resulted. The extent and nature of dinoflagellate and/or fungal involvement in ulcer epizootics of menhaden is under investigation. Unfortunately, ulcerations in other fishes are being largely ignored. Regardless of the principal causative organisms or the detailed processes involved in ulcer initiation and development and associated (?) mortalities, adverse environmental factors seem to have been involved in both epizootics.

The response of two South African east coast estuaries to altered river flow regimes

The response of two South African east coast estuaries to altered river flow regimes

Pfiesteria piscicida and Ulcerative Mycosis of Atlantic Menhaden-Current Status of Understanding.

Ulcerative lesions in estuarine finfish are associated with a variety of parasitic, bacterial, and fungal infectious agents as well as water quality and other abiotic stress factors. Atlantic menhaden Brevoortia tyrannus are a severely affected species typically exhibiting solitary, perianal, focal, deep, granulomatous lesions containing oomycete hyphae. Intense recent emphasis in the scientific literature and in the popular press has been placed on Pfiesteria-like dinoflagellates and their toxins as the causative agents for ulcerative finfish lesions in east coast estuaries of the United States. Dramatic descriptive terms for Pfiesteria, including "phantom," "ambush-predator" and "the cell from hell," capable of affecting humans, have appeared in scientific journals and the news media. However, there is no scientific evidence to date that supports a single, causal relationship between the presence of toxic Pfiesteria-like dinoflagellates and fish kills or the associated ulcerative lesions. This is due, at least in part, to the difficulty of maintaining toxic Pfiesteria-like dinoflagellates in clonal culture and, in part, to the presence of other microorganisms in laboratory culture systems. Further, there is at present no toxin-specific probe to identify Pfiesteria toxins in estuarine environments during fish kills, nor has Pfiesteria been isolated from fish lesions. Yet, based on the limited published scientific evidence and the popular press coverage, there have been river closures, notable economic losses, and public alarm due to Pfiesteria. Future research into agents infectious to menhaden, such as Aphanomyces (Oomycetes) and toxin-producing estuarine inhabitants like Pfiesteria, is needed. These organisms and the disease processes in which they are implicated may also serve as markers for overall estuarine condition. Control of microorganisms, including Pfiesteria, to improve finfish health in estuaries is unlikely. However, using the presence of these microorganisms and their Atlantic menhaden hosts as sentinels to help monitor water quality may be a viable approach to assist future estuarine management.

Seasonal benthic organic matter mineralisation measured by oxygen uptake and denitrification along a transect of the inner and outer River Thames estuary, UK

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 197:103-119 (2000) - doi:10.3354/meps197103 Seasonal benthic organic matter mineralisation measured by oxygen uptake and denitrification along a transect of the inner and outer River Thames estuary, UK M. Trimmer1, D. B. Nedwell1,*, D. B. Sivyer2, S. J. Malcolm2 1Department of Biological Sciences, University of Essex, Colchester CO4 3SQ, United Kingdom 2Centre for Environment Fisheries and Aquaculture Sciences, Lowestoft NR33 OHT, United Kingdom *Corresponding author. E-mail: nedwd@essex.ac.uk ABSTRACT: Seasonal measurements of organic matter mineralisation by oxygen uptake and denitrification were carried out from July 1996 to March 1998 along a ~200 km transect of the River Thames estuary, UK. There was a distinct gradient of decreasing rates of organic matter mineralisation seaward, which was related to the concentration of suspended solids and sedimentary organic carbon (C) at each site. There was clear seasonality and highest rates of oxygen uptake (10056 µmol O2 m-2 h-1) at the muddy sites, but lower rates and non-temperature-dependent oxygen uptake at the sandier sites. Denitrification, both that driven by nitrate from the overlying water (Dw) and that coupled to nitrification in the sediment (Dn), followed a similar trend to oxygen uptake, from negligible rates of approximately 1 µmol N m-2 h-1 for both Dw and Dn at the furthest offshore site, Site 12, to 11407 and 8209 µmol N m-2 h-1, respectively, at the inner muddy Site 1. The Thames estuary is heterotrophic and a very efficient organic C filter, trapping and remineralising 77% of its organic C input. Attenuation of fluvial nitrate loads was regulated by freshwater flow. Minimal attenuation (3%) occurred during peak flows (i.e. during periods of shortest freshwater flushing time) and >100% attenuation during periods of lowest freshwater flow (longest flushing times). Including the sewage treatment works (STWs) nitrate load in this calculation reduced the degree of attenuation of the nitrate load to, on average, 11%. Annual rates of Dw and Dn for an inner area of 125 km2 were 112 and 85 Mmol N yr-1, respectively, with a total rate of 196 Mmol N yr-1 (2744 t), which was equivalent to 9% of the total dissolved inorganic nitrogen (DIN) load for 1995-96. A mean denitrification rate (Dw) of 0.64 mol N m-2 yr-1, based on measurements in 4 east coast estuaries, was used to estimate a total rate of denitrification for the entire area of UK east coast estuaries. The total rate of 0.81 Gmol N yr-1 represented 16% attenuation of the total fluvial discharge of nitrate (~6 Gmol N yr-1) to the UK¹s east coast estuaries (1995-96) and hence a 16% reduction in the UK nitrate load to the North Sea. KEY WORDS: Organic mineralisation · Oxygen uptake · Denitrification · Nutrient attenuation Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 197. Publication date: May 12, 2000 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 2000 Inter-Research.

The response of two South African east coast estuaries to altered river flow regimes

The response of two South African east coast estuaries to altered river flow regimes

Fishing, Consumption, and Risk Perception in Fisherfolk along an East Coast Estuary

Increasingly public and governmental agencies are concerned about the safety of fish and shellfish that recreational fishermen consume. Fishing behavior, consumption patterns, and risk perceptions were examined for people fishing and crabbing in Barnegat Bay, NJ. Women fished in significantly larger groups than men, and their groups included more children. Subjects fished an average of seven times per month and crabbed three times per month; they caught fish on most outings, and 80% ate their catch. Subjects consumed fish an average of five times a month, eating just under 10 oz (ca. 280 g) per meal. Only 25% of the fish consumed by women, and 49% of the fish consumed by men, are self-caught. Nearly 90% of the people believe the fish and crabs from Barnegat Bay are safe to eat, although about 40% have heard some warnings about their safety. Most people heard about advisories from newspapers or television. Most subjects believe that saltwater fish are safer than freshwater fish and that fish they catch themselves or buy in a bay store are safer than those from a supermarket. People generally do not have a clear understanding of the relationship between contaminants and fish size or trophic level, suggesting an avenue for risk reduction.

PFIESTERIA HEALTH CONCERNS REALIZED

Pfiesteria piscicida has been killing fish in East Coast estuaries and rivers for at least six years. But a concerted and coordinated federal response to the problem did not begin until this September. Since then, eight federal agencies began collaborating to intensify research into these microbes and the ecological conditions underlying their outbreaks. Also, the Environmental Protection Agency started to plan steps to strengthen control over the nutrients that may be causing Pfiesteria outbreaks. And on Sept. 25, Congress held a hearing to discuss the Pfiesteria problem (C&EN, Sept. 29, page 8). The first fish kill in the wild attributed to Pfiesteria took place in North Carolina in May 1991. That was followed by massive outbreaks of the microbe in 1995 and 1997 that killed millions of fish in North Carolina estuaries. In Maryland, Pfiestena was first observed in October 1996, when menhaden, fish used for bait or converted to oil and fertilizer, were found with ...

Nitrogen Losses Through Sediment Denitrification in Boston Harbor and Massachusetts Bay

Sediment denitrification is a microbial process that converts dissolved inorganic nitrogen in sediment porewaters to N2 gas, which is subsequently lost to the atmosphere. In coastal waters, it represents a potentially important loss pathway for fixed nitrogen which might otherwise be available to primary producers. Currently, data are lacking to adequately assess the role of denitrification in reducing or remediating the effects of large anthropogenic nitrogen loads to the coastal zone. This study describes the results of 88 individual measurements of denitrification (as a direct flux of N2 gas) in sediment cores taken over a 3-yr period (1991–1994) from six stations in Boston Harbor, nine stations in Massachusetts Bay, and two stations in Cape Cod Bay. The dataset is unique in its extensive spatial and temporal coverage and includes the first direct measurements of denitrification for North Atlantic shelf sediments. Results showed that rates of denitrification were significantly higher in Boston Harbor (mean=54, range<5–206 μmol N2 m−2 h−1) than in Massachusetts Bay (mean=23, range<5–64 μmol N2 m−2 h−1). Highest rates occurred in areas with organic-rich sediments in the harbor, with slower rates observed for low-organic sandy sediments in the harbor and at shallow shelf stations in the bay. Lowest rates were found at the deepest shelf stations, located in Stellwagen Basin in Massachusetts Bay. Observed rates were correlated with temperature, sediment carbon content, and benthic macrofaunal activity. Seasonally, highest denitrification rates occurred in the summer in Boston Harbor and in the spring and fall in Massachusetts Bay, coincident with peak phytoplankton blooms in the overlying water column. Despite the fact that sediment denitrification rates were high relative to rates reported for other East Coast estuaries, denitrification losses accounted for only 8% of the annual total nitrogen load to Boston Harbor, a consequence perhaps, of the short water-residence times (2–10 d) of the harbor.

Transport and Recruitment of Blue Crab Larvae:a Model with Advection and Mortality

The present paper develops a mathematical model for the transport and recruitment of blue crab (Callinectes sapidus) larvae, and applies it to the inner continental shelf of the Middle Atlantic Bight near Delaware Bay, U.S.A. Blue crab larvae develop through seven or eight planktonic zoeal stages to a megalopa stage suitable for recruitment to adult populations of east coast estuaries. The larvae are concentrated near the surface, and the currents are primarily forced by alongshelf winds and river discharge through major estuaries. Model currents are prescribed based on a realistic synthesis of their observed relationship to wind and river discharge. Besides the resulting advection, particle diffusion and biological mortality are added to determine the fate of larvae released from their parent estuary. Groups of particles were released across the source region of the outflowing buoyancy-driven current in the model estuary mouth. Most larvae were swept alongshelf to the south with the buoyancy-driven coastal current, and thus were lost as recruits to the population of their parent estuary. However, some larvae released close to the seaward edge of the emerging coastal current were able to cross the coastal current front and move seaward into inner shelf water during upwelling-favorable (northward) wind events. Some of these, in turn, were suitably placed near the parent estuary mouth so that they could be advected landward as megalopae into the estuary during a subsequent downwelling-favorable (southward) wind event and thus join the adult population. The model results for megalopae returns were computed from consecutive daily release of 1000 particles, and were compared with 4 years of blue crab megalopa settlement data for Delaware Bay. The model results for 1989 and 1990 matched the observed data remarkably well, with both years showing dominance by a single return event of a few days duration. For 1991 and 1992, the observed results showed multiple return events, and the model results did not follow these well.

Coastal-marine discontinuities and synergisms: implications for biodiversity conservation

Coastal-marine biodiversity conservation must focus increasingly at the level of the land- and seascape. Five cases illustrate discontinuities and synergisms and how system changes may take place. For Caribbean coral reefs, the result of overfishing and disease has been a ‘shrinkage’ in the entire system, the effects of which may cascade through the coastal seascape. For Beringia, patterns of benthic diversity are best understood in a manner that matches the multiscale, integrated dynamics of weather, ice, marine mammal feeding, and community structure. In the case of US East Coast estuaries, oyster reefs may be keystone elements, with important effects on functional diversity. Large-scale coastal systems depend upon the connectivity of fresh and marine waters in the coastal zone, having implications for the apparent stochasticity of coastal fisheries. And, for a coastal barrier-lagoon site, a state change may be described in terms of a combination of succession, the attainment of a quasi-equilibrium state, and disturbance. A profound problem for conservation is that there is very little information about the relationship between species diversity and ecological function. Coastal-marine biodiversity conservation is best addressed at the level of the land- and seascape.

Persistence and Degradation Pathways of Tributyltin in Freshwater and Estuarine Sediments

The degradation of tributyltin (TBT) in contaminated freshwater and estuarine sediments was investigated for a 330-day period under controlled laboratory conditions. Rates of TBT degradation at different depths within various sediments were established, where possible, using regression modelling, and revealed TBT half-lives ranging from 360 to 775 days in surficial sediments. There appeared to be very little difference between degradation rates in freshwater and estuarine sediments, although a notable increase in TBT half-life was evident in spiked sediments containing elevated TBT concen-trations. Degradation trends suggest that TBT either debutylates to dibutyltin (DBT) and monobutyltin (MBT) in aerobic sediments or degrades to DBT which subsequently desorbs to the overlying water column. In anaerobic sediment, the half-life of TBT was not discernible and appears to be in the order of tens of years. Biotic processes were the most important mechanisms for the decomposition of TBT in freshwater and estuarine sediments. The results are reviewed in the context of concentrations of TBT determined in marina and boatyard sediments in U.K. east coast estuaries.

Estuaries and saltmarshes: the interface between land and sea

Research over the last 20 years has had a major focus on the ecology of east coast estuaries, including the interaction between coastal seawater and saltmarshes. It is not possible to separate intertidal coastal saltmarshes from the rest of the coastal marine environment as they are involved in a truly interactive system. The significance of this system is attracting increasing attention as the effect of elevated nutrient concentrations on the ecology of the coastal zone has become apparent. It is only when we understand how the various chemical and biological processes influence the flux of nutrients through the estuarine interface between land and sea that any sensible management strategy can be developed.

Organotin distribution in sediments and waters of selected east coast estuaries in the UK

An extensive spatial survey of butyl- and methyltin compounds in the sediments and water column of seven Suffolk and Essex estuaries was undertaken between June and August 1990 to determine the main areas of organotin contamination. A number of these estuaries contain important shellfisheries and all have a high degree of boating activity. Speciation of organotins was performed by a purge and trap/boiling point separation method and detected by Atomic Absorption Spectrometry. Despite the implementation of the 1987 UK retail ban on tributyltin (TBT) based antifouling paints on vessels <25 m in length, 7 of the 17 sites sampled exhibited TBT water concentrations above the Environmental Quality Target (EQT) set in 1987. Water column concentrations ranged from <3–71.2 ng l −1. Dredging had occurred at some of these sites indicating that desorption of TBT from the sediment may occur following sediment disturbance. Surficial sediment organotin concentrations displayed high spatial variability with TBT levels ranging from <3–3935 ng g −1. The highest organotin concentrations occurred at sites with high levels of boating activity.

On meteorologically induced flushing in three U.S. east coast estuaries

Meteorologically induced exchange with the coastal ocean is examined for three U.S. east coast estuaries using time series of subtidal volume flux over a common five-month period. A volume of water equal to that of the estuary was discharged every 86·4, 135·3 and 108·8 days for Narragansett, Delaware and Chesapeake Bays, respectively. However, a large fraction of the water discharged to the shelf is recirculated ocean water. For Chesapeake Bay, outflowing estuarine water can be considered as a mixture of 2·4–3·0% water of mean estuarine salinity and the remainder water of oceanic salinity. The degree of meteorological flushing is strongly influenced by mean depth, as a drop in sea level of a given amplitude will force a greater fraction of water from a shallow estuary than from a deep system. The relative importance of the meteorologically forced circulation and the gravitational circulation is frequency dependent, as illustrated by salinity variance at the entrance to Chesapeake Bay. Seasonal salinity variance must ultimately be controlled by seasonal changes in runoff, through the mechanism of gravitational circulation. However, the high coherence of wind-induced changes in bay volume and bay entrance salinity at periods of 2–20 days suggests that meteorologically forced advection is primarily responsible for salinity variance at these time scales.

Phytoplankton production in two east coast estuaries: Photosynthesis-light functions and patterns of carbon assimilation in Chesapeake and Delaware Bays

Chesapeake Bay is a large and productive estuary that has received close scrutiny in recent years because of indications that its water quality and biota have been damaged by man's activities. Data on primary production for the estuary as a whole, however, are surprisingly sparse. We describe here the distribution of photosynthetic carbon assimilation by phytoplankton in Chesapeake Bay, and relate productivity patterns to hydrographic characteristics of the estuary. Between March 1982 and April 1983, a series of four cruises was conducted on Chesapeake Bay, and two cruises on the urbanized Delaware Bay for comparison. The upper Chesapeake and Delaware were highly turbid with high concentrations of suspended particulate matter and dissolved inorganic nutrients. Low chlorophyll concentrations were usually found in these areas of high turbidity, despite the abundance of nutrients, suggesting light limitation. Application of Wofsy's (1983) model of phytoplanton growth confirmed this suggestion. Chlorophyll and productivity maxima usually occurred seaward of the turbidity maxima where light penetration increased and suffient nutrients were present to support active phytoplankton growth. Further seaward of the chlorophyll maxima in the Chesapeake, the photic zone depth increased, concentrations of nutrients decreased, and phytoplankton biomass decreased, suggesting that nutrient availability, rather than light, controlled phytoplankton growth in the lower portion of the estuary. In contrast to the Chesapeake, Delaware Bay was more turbid, had generally higher nutrient concentrations, and was lower in phytoplankton productivity. The chlorophyll maxima and region of rapid phytoplankton growth occurred further toward the lower estuary and shelf regions in Delaware Bay because the high turbidity extended further seaward. Nutrients were never depleted at the shelf end of the estuary sufficiently to retard phytoplankton growth. Photosynthesis-irradiance (P-I) curves from simulated in situ and constant intensity incubations showed a strong correlation of the light-limited slope ( a B) with the light-saturated rate ( P m B ) on each cruise. Spatial variations in P m B corresponded to patterns of phytoplankton abundance, as did integral production (PP) and carbon-based growth rates ( μ C, μ m), and photosynthetic parameters varied significantly with temperature.

Observations on the fish populations of an east coast Estuary

Monthly samples of fish were collected from the cooling-water intake screens at Kingsnorth Power Station on the Medway Estuary. A total of 26 372 fish, comprising 41 species, was recorded between April 1981 and August 1983. The seasonal distribution of both species numbers and abundance of fish was similar to earlier studies, although the community structure has altered in recent years. The regular occurrence and increased population size of Osmerus eperlanus, the smelt, and Clupea harengus, the herring, were the most notable changes. The results are compared with previous studies, and the indirect effects of enhanced water quality conditions in the tidal Thames and the subsequent recolonization by fish, which were previously absent for many years, are discussed.

Eggs and Early Larvae of the Bay Anchovy, Anchoa mitchilli, and the Weakfish, Cynoscion regalis, in Lower Chesapeake Bay with Notes on Associated Ichthyoplankton

The seasonal abundance and spatial distribution of eggs and early larvae of the bay anchovy,Anchoa mitchilli, and the weakfish,Cynoscion regalis, were determined from plankton collections taken during 1971–1976 in the lower Chesapeake Bay. Eggs and larvae of the bay anchovy,Anchoa mitchilli, dominated the ichthyoplankton, making up 96% of the total eggs and 88% of all larvae taken. A comparison of egg and larval densities from the lower Chesapeake Bay to existing data from other East Coast estuaries suggested that Chesapeake Bay is a major center of spawning activity for this species.Anchoa mitchilli spawning commenced in May when mean water column temperatures approached 17°C and abruptly ceased after August. Eggs and early larvae presented a continuous distribution throughout the study area during these months. Eggs and larvae of several sciaenid species, especiallyC. regalis, ranked second in numerical abundance. Larval weakfish were consistently taken in late summer of each sampling year but peak abundance and distribution was observed in August 1971. Sciaenid eggs exhibited a distinct polyhaline distribution with greatest concentrations observed at the Chesapeake Bay entrance or along the Bay eastern margin. Analysis of sciaenid egg morphometry and larval occurrence suggested spawning activity of at least four species. Additional important species represented by eggs and/or larvae in the lower Chesapeake Bay wereHypsoblennius hentzi, Gobiosoma ginsburgi, Trinectes maculatus, Symphurus plagiusa andParalichthys dentatus with the remaining species occurring infrequently.

Jamaica Bay Studies: I. Environmental Determinants of Abundance and Distribution of Common Terns (Sterna hirundo) and Black Skimmers (Rynchops niger) at an East Coast Estuary

Jamaica Bay Studies: I. Environmental Determinants of Abundance and Distribution of Common Terns (Sterna hirundo) and Black Skimmers (Rynchops niger) at an East Coast Estuary

The Chironomid (Insecta: Diptera) and Other Fauna of a Myriophyllum spicatum L. Plant Bed in the Lower Hudson River

The benthic fauna of a small cove of the Hudson River containing the aquatic plantMyriophyllum spicatum L. was studied for a one-year period. The fauna was characteristic of oligohaline zones of United States east coast estuaries. Total abundance of invertebrates retained on a 0.12 mm mesh sieve averaged 124,631 organisms m−2 (sediment and plant populations combined) and ranged up to 196,000 m−2. During the May–August period, invertebrates living on the plants comprised 16–35% of the invertebrate fauna in the cove. Chironomid larvae were the most abundant organisms on plants and the third most abundant in the sediments. Two assemblages of chironomid species were recognized; one lived solely in the sediments, the other lived primarily on the plants.Chironomus decorus andTanytarsus sp. dominated the former group andCricotopus sylvestris the latter. The chironomidDicrotendipes modestus utilized both habitats. During the May–August period, chironomid biomass on the plants comprised approximately 50% of total chironomid biomass in the cove. The mean dry-weight biomass of chironomids in the cove (1.6 g m−2) is estimated to be sixteen times greater than that of the fauna in the deeper areas of the river. Because chironomid larvae are eaten by fish and invertebrates, shallow water regions with their rich chironomid (and other fauna) may contribute importantly to the trophic dynamics of estuarine systems. *** DIRECT SUPPORT *** A01BY009 00004

Seasonal variations in Delaware Bay phytoplankton community structure

Whole-water phytoplankton samples were obtained from 3 stations in Delaware Bay on a once- or twice-monthly basis from June 13, 1974 to May 28, 1975. The flora was composed primarily of small flagellates during the summer and early fall, while diatoms dominated from October to May. Peak cell numbers occurred during fall and early spring blooms. Evenness diversity was lowest during periods of maximum diatom abundance and highest when microflagellates predominated. There was a gradual shift in dominance, except during the early spring Skeletonema costatum bloom. Cluster analysis allowed the separation of the flora into 3 time groups and 8 recurrent species groups. The species composition and community structure of Delaware Bay phytoplankton is compared with other USA east-coast estuaries where comparable sampling techniques have been used.