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Abstract: In the temperate North Atlantic Ocean the ecological changes in coastal waters associated with a warming period in the 1930s were compared with the past couple of decades when the North Atlantic Oscillation was also positive. Long-term monitoring data sets from Rhode Island and nearby coastal waters were used to identify trends in the recent warming period. During both events winter water temperatures warmed above a mean value of 2.9°C from 1°C to 3°C. There was no apparent trend in the annual salinity cycle correlated with the increased temperature. During both periods boreal species declined, southern species increased, and widespread declines in eelgrass occurred. Estuaries on the western Atlantic Ocean during the recent warming period had phytoplankton biomass during the winter-spring bloom decrease, zooplankton number increase, and nutrients remain elevated due to enhanced zooplankton grazing. Zooplankton numbers decreased in summer due to enhanced ctenophore predation. In these waters the loss of boreal demersal fish has been compensated by an increase in demersal decapods. The very large ecological changes caused by small increases in seasonal temperature provide an insight to the large alterations that may be associated with global warming.

The potential role of lobster trap bait as a significant food subsidy contributing to unprecedented recent increases in abundance and landings of the American lobster Homarus americanusis seldom considered seriously outside the fishing community. Although bait input is a very small source of organic carbon compared with primary production, the yearly input of bait per unit area to the inshore waters of the Gulf of Maine is about 85 kg/ha, an amount equal to a very productive fishery yield from a marine area. Because much of the bait is imported from outside the inshore area of the Gulf of Maine, it represents a direct subsidy to secondary production within this portion of the system. An empirical relationship between fish yield and primary production in phytoplankton-based marine systems suggests that inshore primary production would have to be increased by about 80% to provide an increment in fish yield equal to the bait input. Moreover, a simple trophic calculation based on an estimated amount of bait consumed in traps and the growth efficiency of juvenile American lobsters also shows that the bait could potentially support one-quarter to one-third of the recent American lobster landings from the inshore area of the Gulf. This preliminary assessment suggests that lobster bait may make a substantial contribution to American lobster production—a contribution that, if confirmed, should be further examined and carefully considered in future American lobster management.

Abstract: Three factors affecting the structure of nekton communities 9fishes and decapod crustaceans) in eelgrass beds were identified and evaluated: contiguous shoreline type, distance from shore, and macrophyte biomass. Throw traps (1 m2) were used to sample eelgrass nekton at seven locations in Great South Bay (New York, U.S.) along Fire Island National Seashore from May through October 1995. Abundances ofGobiosoma ginsburgi, Apeltes quadracus, andOpsanus tau were significantly higher in eelgrass beds adjacent to salt marshes.Menidia menidia, Syngnathus fuscus, Pseudopleuronectes americanus, andPalaemonetes pugio were significantly more abundant in eelgrass adjacent to beaches. Regression analyses indicated thatSyngnathus fuscus, Pseudopleuronectes americanus, andAnguilla rostrata abundances were positively related to eelgrass biomass, andApeltes quadracus andGobiosoma ginsburgi abundances were highest at moderate levels of macroalgae biomass. The distance of an eelgrass bed from shore was also important. Species generally associated with salt marshes (Fundulus heteroclitus, Cyprinodon variegatus, Lucania parva, andPalaemonetes pugio) were more abundant in eelgrass near the marsh shore. Abundances ofApeltes quadracus, Syngnathus fuscus, Menidia menidia, Hippolyte pleuracanthus, andCrangon septemspinosa increased with distance from the shoreline. Shoreline type, distance from shore, and macrophyte biomass appear to affect the abundance and distribution of some nekton species. The effect of shoreline type may be related to the distribution of macrophyte biomass; the biomasses of eelgrass and macroalgae were significantly higher along beach and marsh shorelines, respectively. Explaining within-habitat variability and identifying microhabitat preferences for nekton will aid in the proper design of future studies and habitat restoration efforts.

Abstract: The metabolic rate of individual habitats can differ significantly in their contribution to the total system productivity of estuaries. Changing environmental conditions such as those created by tidal exchange can frequently alter these rates. In an effort to quantify these rate responses, metabolic rates were measured for macroalgal and sediment habitats at different salinities. Microcosms representing the two habitats were incubated at three salinity ranges (high: 25 to 31‰; moderate: 12 to 18‰; and low: 0 to 4‰) and production and respiration rates were estimated. The production rates for both habitats were proportional to the salinity of the water in the incubation, with the lowest metabolic rates associated with the lowest salinity. Average macroalgal habitat net production rates were 879 mg O2 m−2 h−1, 609 mg O2 m−2 h−1, and 451 mg O2 m−2 h−1 at high, moderate, and low salinity treatments, respectively, and the dark respiration rates were −401 mg O2 m−2 h−1, −341 mg O2 m−2 h−1, and −333 mg O2 m−2 h−1. Average sediment habitat net production rates were 60 mg O2 m−2 h−1, 13 mg O2 m−2 h−1 and 10 mg O2 m−2 h−1 and the respiration rates were −114 mg O2 m−2 h−1, −55 mg O2 m−2 h−1, and −31 mg O2 m−2 h−1 at high, moderate, and low salinity treatments. The larger contribution of macroalgal habitats to system metabolism may account for observed diurnal changes in water column oxygen levels in some estuaries. Macroalgal production rates explained 83% of the increase in water column oxygen levels during daylight hours and macroalgal respiration rates explained 65% of the decline in oxygen levels during the night. The contribution of macroalgal metabolism to the system can be influenced by even short-term changes in water column salinity. Environmental processes that alter salinity levels on hourly time scales may moderate the effect of macroalgal metabolism on oxygen levels.

Abstract: Consumption rates ofMnemiopsis leidyi by butterfish,Peprilus triacanthus, ranged between 4 ml/gm dry wt/hr to 184 ml/gm dry wt/hr, depending on fish size and feeding history. These rates of comsumption supply adequate food to support the metabolism of the fish and probably account for the late summer-early fall decline in population levels ofMnemiopsis observed in Narragansett Bay.

Abstract: The maximum population density of the burrowing anemone (Ceriantheopsis americanus) was estimated at 17–28 animals m−2 in soft-bottom sediments of mid Narragansett Bay. The gut contents of the anemone indicated primary prey of harpacticoid and calanoid copepods. The consumption of calanoid copepods was higher in October than April, which may be due to decreased density of hapacticoids in the fall. The anemones apparently avoid fish predation in late summer by withdrawing into the sediments. After the seasonal fall migration of fish out of the bay, anemones reappear.

Abstract:Elevated UV-B radiation levels (~100% above ambient) generally failed to produce significantly different effects at different trophic levels in well-mixed mesocosms during the winter spring bloom period. Although not significantly different, several consistent trends were noted. Phytoplankton abundance, measured as total cell counts, and biomass, measured as in vivofluorescence, tended to be reduced in UV-B enhanced treatments. Effects were significantly different for fluorescence (p< 0.05) during the bloom event but not abundance (p= 0.29) and not over the entire experiment. There was a tendency for the ratio of nanoplankton to microplankton biomass to be lower in UV-B enhanced systems (p= 0.16). Total copepod abundance (adults, copepodites and nauplii) and abundance of the dominant species, Acartia hudsonica(Giesbrecht), also tended to be lower in the treatment mesocosms. Significant differences (p< 0.05) in copepod abundance between controls and treatments were observed in the adult stage prior to and during the bloom event. Survival of winter flounder (Pleuronectes americanus[Walbaum]) eggs incubated at 0.1 and 0.5 m depths was significantly lower in UV-B elevated mesocosms (p< 0.05) while no significant differences were observed at greater depths (p= 0.55). Survival and growth of winter flounder larvae added to the mesocosms during the final three weeks of the experiment did not vary significantly between controls and treatment mesocosms.

Abstract: Field surveys of phytoplankton metabolism, based on oxygen changes, were made in Narragansett Bay from 1971–73. Annual daytime net production varied from 218 g C per m2 per yr in the East Passage to 429 g C per m2 per yr in the Providence River. The area based average for the bay was 269 g C per m2 per yr. The area based average night respiration was 159 g C per m2 per yr resulting in an annual net carbon available for export or to the benthos of 110 g C per m2 per yr. A set of microcosms, operated so as to simulate the Bay, had an annual net production of 276 g C per m2 per yr and a night respiration of 163 g C per m2 per yr resulting in an annual net carbon available for export or to the benthos of 113 g C per m2 per yr. *** DIRECT SUPPORT *** A01BY015 00002

Abstract: The distributions of dissolved organic carbon (DOC), phytoplankton biomass (as measured by in vivo fluorescence), total nitrogen and phosphorus, and light extinction were observed on 10 cruises during 1989 and 1990 in the Pawcatuck River estuary located in southern Rhode Island. In the lower estuary, the distance of peak phytoplankton biomass from the head of the estuary was positively correlated with river discharge while the magnitude of the peak increased with decreasing discharge. High light-extinction appeared to limit the accumulation of biomass in the upper estuary. Variability in light extinction was largely (50%) explained by variation in the concentration of DOC. Salinity versus constituent plots suggested that DOC behaved nonconservatively in the estuary. These observational data indicate that the mixing behavior of DOC in the estuary influences light extinction and thus may limit accumulation of phytoplankton biomass in the upper estuary. This interpretation of observational data was supported by experimental work that demonstrated the significant contribution of DOC to light extinction, and by measurements, of phytoplankton productivity that showed greater light limitation in the upper estuary.

ABSTRACT:
Wastewater solids were added to a series of marine mesocosms at the Marine Ecosystem Research Laboratory (MERL), University of Rhode Island. There was a range of sludge addition simulating 1, 4, and 8 times the average nitrogen enrichment of Narragansett Bay. Three other mesocosms received inorganic nutrients at similar levels, and three mesocosms were maintained as controls. In systems receiving nutrients or sludge, primary production was initially increased. Respiration of the increased loading in the sludge treatment generally resulted in decreased dissolved oxygen concentrations. In the highest level of sludge treatment, the benthic respiration resulted in anoxic conditions in the fourth month of the experiment. The benthos seemed to be the area primarily affected by wastewater disposal. Species feeding at or near the sediment–water interface showed a strong positive density response to sludge addition because of the increase in available food. Based on the findings of this experiment and comparison with marine areas of wastewater disposal, the condition of the benthic community can be generally defined based on organic loading rates. Organic loading rates less than approximately 0.1 g/m2· d C had little effect on the sediment community. Loading rates between 0.1 and 1.0 g/m2· d C resulted in an enriched sediment community, while loading over 1.5 g/m2· d C produced degraded conditions. The quantification of the relationship between organic loading and benthic response presented here can be useful in evaluating wastewater treatment and disposal options.

Measurements of the abundance of major populations, their metabolism, and the seasonal patterns of total system metabolism throughout a year were used to develop energy—flow diagrams for a New England salt—marsh embayment. The annual ecological energy budget for the embayment indicates that consumption exceeds production, so that the system must depend on inputs of organic detritus from marsh grasses. Gross production ranged from almost zero in winter to about 5 g O2m—2day—1in summer. Respiration values were similar, but slightly higher, with the maximum difference observed in fall. Populations of shrimp and fish were largest in fall, with a much smaller peak in spring. Few animals were present in the embayment from May to July, but fall populations of shrimp ranged from 250 to 800 m—2and fish averaged over 10 m—2. Birds were most abundant in winter and spring. In spite of high numbers, no evidence was found that the marsh embayment exported large amounts of shrimp or fish to the estuary. Production of aboveground emergent grasses on the marsh equaled 840 g m—2for tall Spartina alterniflora, 432 g m—2for short S. alterniflora, and 430 g m—2for S. patens. These values are similar to those for New York marshes, but substantially lower than the southern marsh types. The efficiency of production of marsh grasses in the New England marsh was lower than reported for southern areas. A simulation model based on the laboratory and field metabolism and biomass measurements of parts of the embayment system was developed to predict diurnal patterns of dissolved oxygen in the marsh. The model was verified with field measurements of diurnal oxygen curves. The model indicated the importance of the timing of high tides in determining oxygen levels and was used to explore simulated additions of sewage BOD and increases in temperature.

A mussel bed dominated by Mytilus edulis contained large concentrations of living consumer biomass, with over 14 kg dry weight/m2 distributed among eleven species. An additional 14.4 kg dry weight/m2 was present as empty shell fragments that contributed to community structure. Field measurements of community respiration for this dense animal system showed a roughly hyperbolic response to increasing current speed. In still water, oxygen uptake was 0.2g O2/m2/hr while in currents over 0.1 m/sec it quickly rose to about 2.7 g O2/m2/hr.

Measurement of community metabolism in a coastal pond eelgrass bed gave values of 2.9 g O2m—2day —1for apparent production and 3.6 g O2m—2day—1for night respiration. The excess of consumption over production during a full day in early August is indicative of the declining state of the plants by midsummer. Measurements of upstream—downstream dissolved oxygen in a tidal river eelgrass bed showed unusual transients and occasional high values for production and respiration. These observations may have been related to turbulent tidal transport, to exchanges of oxygen between the water and lacunar spaces within the Zostera, and to higher metabolic rates in faster currents.