The effect of chronic oil pollution on salt-marsh nitrogen fixation (acetylene reduction)

Annual acetylene reduction rates associated with interidal communities in a chronically oil polluted Virginia salt marsh were compared to rates measured in an undisturbed marsh. Chronic oil treatment resulted in visible damage to the higher plants of theSpartina alterniflora zones; however, vegetation-associated acetylene, reduction was not different from the untreated control. Sediment rates generally were affected little by oil application, except during the summer when rates in the median tidal elevation zones were considerably higher than those of the control. Acetylene reduction occurred in all transects, each of which extended from upper mudflat to theSpartina patens zone. Intertidal sediment acetylene reduction was patchy, both spatially and seasonally. Estimated rates were greatest near the surface; free-living bacterial N₂ fixation activity averaged 2.23 mg N per m² per d (range=undetectable to 365 mg N per m² per d) in the untreated and 3.17 mg N per m² per d (range=undetectable to 564 mg N per m² per d) in the oil-treated marsh during the year. Vegetation-associated N₂ fixation activity yielded highest overall mean rates (156 mg N per m² per d). The seasonal pattern of sediment and vegetation-associated fixation may be controlled by temperature and availability of oxidizable substrates.     

Carbon dynamics of estuarine ponds receiving treated sewage wastes

The carbon dynamics of six estuarine ponds at Morehead City, North Carolina, were measured from August 1969 through August 1970. Three waste ponds received secondary treated sewage effluent and three served as controls. Total organic levels were determined by combustion with a Beckman total carbon analyzer. Inorganic levels were calculated from temperature, pH, and carbonate alkalinity. Carbon dioxide diffusion across the air-water interface was measured with a floating plastic dome and an infrared gas analyzer. Carbon metabolism was determined from diurnal changes in total inorganic carbon. From October through April the wastereceiving ponds were characterized by an intense bloom of a small alga,Monodus guttula. During the bloom organic levels reached 75 mg C per 1. The warmer months were characterized by a more diverse flora and organic concentrations averaging 25 mg per 1. Organic levels in the control ponds seldom were greater than 10 mg per 1. CO₂ diffused constantly out of the control ponds due to input of high alkalinity water supersaturated with inorganic carbon. During the bloom in the waste ponds diffusion of CO₂ from the atmosphere was as high as 0.5 g C per m² per day. CO₂ diffused into the water constantly because the high uptake rate of inorganic carbon by the small algae reduced the levels in the water to less than 5 mg per 1. Gross production of the waste receiving ponds avearaged 2,86 g C per m² per day during the bloom and 2.44 during the non-bloom period. The average productivity of the control ponds was 1.7. Corrections for CO₂ diffusion were significant in the control ponds and in the waste ponds during theMonodus bloom. Availability of carbon from diffusion and respiratory regeneration seemed to limit phytoplankton productivity during the bloom. The annual budgets for the two sets of ponds were distinctly different. For the control ponds, the input of organic matter was nearly equal to losses indicating almost no net production of organic material. A high net loss of organic material and a net gain of inorganic carbon for the waste ponds reflected the net productive nature.     

Bacterial consortium expressing surface displayed,intra- and extracellular lipases and pseudopyronine B for the degradation of oil

The lipA gene, encoding a solvent-tolerant extracellular lipase from Proteus sp. SW1, was displayed on the cell surface of Escherichia coli by fusing it to an antigen 43 anchoring motif. The display of LipA on the Escherichia coli cell surface was directly confirmed by immunofluorescence microscopy and flow cytometry. After 6 days of incubation in media containing 1 % used cooking oil, an Escherichia coli strain expressing surface displayed lipase was able to degrade 27 % of the oil. The biosurfactant, pseudopyronine B, was purified from culture supernatants of Pseudomonas sp. SL31. Its critical micelle concentration was determined to be 1400 mg/l, and the surfactant was stable within a temperature range from 0 to 120 °C and a pH range of 3–11. Pseudopyronine B-containing crude media extracts efficiently removed up to 51 % of the cadmium from contaminated water. We demonstrated the oil degradation ability of the mixed culture of four bacterial strains, namely the recombinant Escherichia coli expressing cell surface displayed lipase (pKKJlipA), His-tagged lipase (pETlipA), extracellular lipase-producing Proteus sp. SW1, and pseudopyronine B-producing Pseudomonas sp. SL31 by culturing in LB media containing 1 % oil. The consortium degraded 29 % of oil in one day and reached 84 % after 7 days.     

Productivity,detritus flux,and nutrient cycling in a Carex lyngbyei tidal marsh

Net annual primary production of a sedge Carex lyngbyei dominated tidal marsh in the Fraser River estuary, British Columbia, Canada was 634 g ash-free dry weight (AFDW) per m² per yr (687 g dry weight per m² per yr). Mean maximum shoot elongation during the short (May to August) growing season was 1.88 cm per day from overwintering shoots. The maximum aboveground standing crop of 690 g AFDW per m² represented only 25% of the total below-ground biomass, which appears to be controlling most of the critical life history processes of the sedge marsh. An estimate of 14 percent of the aboveground standing crop was lost through leaching of dissolved organic carbon from the growting plant. Aboveground tissue losses, which were negligible during the growing season, occurred primarily via translocation in autumn and tidal export during the winter. In situ measurements showed that of the original maximum standing crop, approximately 38%, 37%, and 25% were lost by downward translocation, tidal export, and sediment burial, respectively. Based on changes in above and belowground nutrient pools, rapid spring (May to late June) uptake rates of 109 mg N per m² per day and 23.0 mg P per m² per day by shoots were followed by downward translocation rates of 44.8 mg N per m² per day and 12.2 mg P per m² per day during late June to the end of August. Aboveground leaching rates were estimated as 23.9 mg N per m² per day and 7.8 mg P m² per day and belowground uptake rates as 100 mg N per m² per day and 26 mg P per m² per day; root uptake occurred primarily after late June. Nutrient levels in decomposing litter more than doubled over the winter period showing a pattern of nutrient enrichment characteristic of marsh ecosystems. *** DIRECT SUPPORT *** A01BY023 00004     

Effects of continuous chlorination on spat of the American oyster (Crassostrea virginica)

Newly settled spat of the American oyster (Crassostrea virginica) exhibited reduced survival and growth when exposed to chronic chlorination (as Na-OCl). Spat exposed to nominal concentrations of 0.250 and 0.500 mg per 1 chlorine-produced oxidant (CPO) had only 20% survival after 12 weeks, compared to 64% survival in controls. Spat growth was retarded by nominal concentrations as low as 0.125 mg per I CPO. Shell height of control oysters increased 103% after 12 weeks, while spat exposed to 0.125 mg per I CPO grew 39% and spat exposed to 0.250 mg per I CPO had no net growth. Surviving spat exposed to 0.500 mg per I CPO showed an apparent growth increase of 160%, due mainly to heavy mortality among smaller-sized spat. The numbers of spat (whether surviving or not) that showed any growth over the 12-week exposure period decreased with increasing chlorine concentration. Larger spat were found to be more resistant than smaller spat to increased chlorination. The mechanism of growth inhibition in spat (mantle retraction and cessation of feeding) appeared to be similar to that found in adult oysters exposed to chlorine.     

Seasonal variations in chlorophyll and nutrients in a Canadian arctic estuary

The Eskimo Lakes and Liverpool Bay constitute a series of estuarine waters to the Beaufort Sea in arctic Canada. Salinity ranges in summer from 20‰ at the mouth to less than 1‰ at the head of the system. Arctic features include an ice cover lasting for about 8 months annually and water temperatures which fluctuate from ?1°C in winter to as high as 12°C in late summer. Subsurface light is severely attenuated. Reactive phosphate varies from a spring high of 0.3 μg-at P per 1 to undetectable levels during summer. Nitrate is more abundant, and silicate is consistently plentiful. Chlorophyll a reaches a maximum only occasionally higher than 3 mg per m³ in June and July, rising from undetectable levels in winter. Photosynthetic rates are low by all standards, and have not been measured at greater than 6.4 mg C per m² per hour in summer. Low levels of subsurface light and reactive phosphate and nitrate characterize this exceptionally oligotrophic arctic estuary.     

Biodeposition by a fouling community in the Indian River,Florida

Biodeposition rates were studied for a fouling community with a biomass of 6–10 kg per m² dry wt including shells in which the barnacle Balanus eburneus was a dominant species. The fouling community filtered Indian River lagoon water containing 2–15 mg per 1 mud-size particles and deposited them as sand-size fecal pellets. Measurements of the fecal pellet flux by sediment traps indicated seasonal variations between 16.7 and 74.8 g per m² per day. A significant correlation was found between fecal pellet flux and temperature (r=0.90; p<0.001). The average flux of fecal pellet deposition was four times greater than the average flux of suspended particle settling without biological influence. Suspended sediment concentration did not significantly affect the rate of biodeposition. Annual biodeposition was 18 kg per m².     

Response of the phoxocephalid amphipod,Rhepoxynius abronius,to a small oil spill in Yaquina Bay,Oregon

A spill of approximately 284,000 liters of Bunker C and diesel fuel oils occurred at the entrance of Yaquina Bay, Oregon, following the wreck of the freighterBlue Magpie on 19 November 1983. A portion of this oil entered the lower estuary and was deposited on subtidal benthic habitats occupied by the phoxocephalid amphipodRhepoxynius abronius. This species is particularly sensitive to contaminants in sediment and its life history had previously been studied at the same sites affected by the spill. The oil was initially present as small, sand-coated globules at the study site, and persisted in association with detritus and sediment for months. Bioassays withRhepoxynius abronius showed that the oil globules were not acutely toxic unless mixed into the sediment at concentrations of 1.0 parts per thousand or greater. A series of 10-d bioassays before and after the spill showed that sediment collected from oiled subtidal sites did not become acutely toxic to this species. Although the density of theR. abronius population declined by 75% after the spill, similar declines of the same population were observed at this site in fall 1980. Oil-exposedR. abronius from Yaquina Bay were slightly more sensitive to cadmium in sediment than individuals from Whidbey Island, Puget Sound, Washington. Although mean fecundity was greater in 1984 than in 1981, recruitment following the spill was lower than in the 1980–1981 study. Thus, there is limited evidence for a small impact of the oil spill on this sensitive amphipod.     

Improving microbial oil production with standard and native oleaginous yeasts by using Taguchi design

Production of microbial oil has attracted a great attention in recent years. The potential of lipid production by the yeast strains is the reason for using microorganisms for biodiesel production. Microbial lipid has high similarity to the oil obtained from plants and animals in type and composition. Production of oil from yeasts must be economical, so optimization of the cultivation condition to reach higher production must be done. Native oleaginous yeast, Cryptococcus albidus, was isolated from soil by the nitrogen-limited medium and screened by Nile red staining. Yarrowia lipolytica DSM 8218 was used for lipid production as a standard strain. C. albidus was an excellent oleaginous yeast, and the lipid quantity, dry biomass and lipid productivity of this strain were 11.81 g/l, 19.65 g/l and 60.1 %, respectively, in shaking flask cultivation at 150 rpm and 25 °C in nitrogen-limited medium containing per liter 75 g glucose, 1 g (NH₄)₂SO₄, 1 g yeast extract, 3 g KH₂PO₄, 1.5 g MgSO₄.7H₂O, 0.15 g CaCl₂, 0.06 g MnSO₄.H₂O, 0.02 g ZnSO₄.7H₂O and 0.15 g FeCl₃.6H₂O with pH adjusted to 6.5. Fourier transform infrared spectroscopy was used for analyzing and confirming the production of microbial oil in this study.     

Acute and chronic toxicity of atrazine to estuarine fauna

Acute and chronic estuarine invertebrate and fish toxicity testes were conducted to evaluate possible consequences of measured concentrations of atrazine in estuarine areas. The 96-h LC50 values ranged from 0.094 mg per 1 for copepods to >30 mg per 1 for larvae of eastern oysters. Maximum acceptable toxicant concentrations of >0.08<0.19 mg per 1 and >1.9<3.4 mg per 1 were determined for mysid shrimp and sheepshead minnows, respectively in life cycle and early life cycle testes. The approximate application factor limits in both tests were 0.1–0.2. Use of an application factor of 0.1 with the most sensitive species tested acutely provides a no effect, concentration of approximately 0.009 mg per 1 for estuarine fauna. Therefore, the maximum reported measured concentration of approximately 0.002 mg per 1 atrazine in estuarine areas would not be suspected to adversely impact estuarine fauna.     

Isolation of <Emphasis Type="Italic">Bacillus cereus</Emphasis> from botanical soil and subsequent biodegradation of waste engine oil

Waste engine oil causes a vital environmental pollution when it spill during change and transportation and products of waste engine oil causes lethal effects to the living systems. Thus, abiotic and biotic approaches are being extensively used for removal of waste engine oil pollution. Therefore in present study, waste engine oil degradation was accomplished by a new bacterial culture, isolated from the soil by an enrichment technique. Morphological, biochemical and gene sequence analysis revealed that isolate was Bacillus cereus. Subsequently, biodegradation potential of B. cereus for waste engine oil was studied. Experimental variables, such as pH, substrate concentration, inoculum size, temperature and time on the biodegradation, were checked in mineral salt medium. The biodegradation efficiency of B. cereus was determined by gravimetry, UV–visible spectrophotometry and gas chromatography. In addition, waste engine oil was also characterized by GC–MS and FTIR for its major constituents, which showed total 38 components in waste engine oil, including hopanes, benzopyrene, long-chain aliphatic hydrocarbons, dibenzothiophenes, biphenyl and their derivatives. Results of successive biodegradation indicated that B. cereus was capable to degrade 1% of waste engine oil with 98.6% degradation potential at pH 7 within 20 days. Hence, B. cereus presents an innovative tool for removing the engine oil from the contaminated area.     

Predation by the ctenophoreMnemiopsis leidyi in Narragansett Bay,Rhode Island

The impact ofMnemiopsis leidyi as a predator was studied quantitatively to determine their feeding rates on mixed natural zooplankton. These studies showed that feeding rate was independent of food concentration, but a function of both temperature and size of ctenophore. The feeding rate (liters cleared per mg dry weight per day) ranged from about 0.01 for larger ctenophores at lower temperatures (10–15°C) to about 0.1 for smaller ctenophores at higher temperatures (20–25°C). Combining these results with ctenophore biomass estimates from three years of sampling, numerical estimates were made of zooplankton mortality due to ctenophore predation. The maximum summer cropping byM. leidyi was calculated to be an average of 5–10% per day for the bay as a whole. Although substantial, this predation pressure alone does not account for the observed summer decline of zooplankton.     

Well blowout rates and consequences in California Oil and Gas District 4 from 1991 to 2005: implications for geological storage of carbon dioxide

Well blowout rates in oil fields undergoing thermally enhanced recovery (via steam injection) in California Oil and Gas District 4 from 1991 to 2005 were on the order of 1 per 1,000 well construction operations, 1 per 10,000 active wells per year, and 1 per 100,000 shut-in/idle and plugged/abandoned wells per year. This allows some initial inferences about leakage of CO₂ via wells, which is considered perhaps the greatest leakage risk for geological storage of CO₂. During the study period, 9% of the oil produced in the United States was from District 4, and 59% of this production was via thermally enhanced recovery. There was only one possible blowout from an unknown or poorly located well, despite over a century of well drilling and production activities in the district. The blowout rate declined dramatically during the study period, most likely as a result of increasing experience, improved technology, and/or changes in safety culture. If so, this decline indicates the blowout rate in CO₂-storage fields can be significantly minimized both initially and with increasing experience over time. Comparable studies should be conducted in other areas. These studies would be particularly valuable in regions with CO₂-enhanced oil recovery (EOR) and natural gas storage. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Methane production and consumption monitored by stable H and C isotope ratios at a crude oil spill site,Bemidji, Minnesota

Stable isotopic ratios of C and H in dissolved CH₄ and C in dissolved inorganic C in the ground water of a crude-oil spill near Bemidji, Minnesota, support the concept of CH₄ production by acetate fermentation with a contemporaneous increase in HCO₃⁻ concentration. Methane concentrations in the saturated zone decrease from 20.6 mg L⁻¹ to less than 0.001 mg L⁻¹ along the investigated flow path. Dissolved N₂ and Ar concentrations in the ground water below the oil plume are 25 times lower than background; this suggests that gas exsolution is removing dissolved CH₄ (along with other dissolved gases) from the ground water. Oxidation of dissolved CH₄ along the flow path seems to be minimal because no measurable change in isotopic composition of CH₄ occurs with distance from the oil body. However, CH₄ is partly oxidized to CO₂ as it diffuses upward from the ground water through a 5- to 7-m thick unsaturated zone; theδ¹³C of the remaining CH₄ increases, theδ¹³C of the CO₂ decreases, and the partial pressure of CO₂ increases.Calculations of C fluxes in the saturated and unsaturated zones originating from the degradation of the oil plume lead to a minimum estimated life expectancy of 110 years. This is a minimum estimate because the degradation of the oil body should slow down with time as its more volatile and reactive components are leached out and preferentially oxidized. The calculated life expectancy is an order of magnitude estimate because of the uncertainty in the average linear ground-water velocities and because of the factor of 2 uncertainty in the calculation of the effective CO₂ diffusion coefficient.     

Bivalve contribution to benthic metabolism in a California Lagoon

Populations of suspension feeding bivalves constitute a metabolically important component of the benthos in Colorado Lagoon, Long Beach, California. Oxygen and nutrient flux were measuredin situ at monthly intervals over a two-year period. Estimates of bivalve metabolism were based on regressions of oxygen and ammonium flux on a measure of clam biomass adjusted allometrically. The introduced bivalve,Mercenaria mercenaria, occurs at maximum densities exceeding 400 per m². Based on mean densities (143 per m²), bivalves contributed more than 50% of the 77 mg O₂ per m² per hr mean annual oxygen uptake and the 191 μM per m² per hr mean ammonium release. Although bivalve biomass was not correlated with other inorganic nutrient flux, on an annual basis the sediments were a source of phosphate (26 μM per m² per hr annual average, range 5 to 50) and a small sink for nitrate and nitrite. Net primary production, ammonium flux, and phosphate flux showed great annual variability while respiration was relatively constant. Total community oxygen uptake was not correlated with temperature. Long term incubations revealed no obvious rhythms having a period between four hours and four days. The benthic flux of ammonium and phosphate was calculated to supply more than the annual requirement of Lagoon phytoplankton.     

Influence of salinity on atrazine toxicity to a Chesapeake Bay copepod (Eurytemora affinis) and fish (Cyprinodon variegatus)

The objective of this study was to determine the influence of a range of salinities (5%., 15%., and 25%.) on the acute toxicity of atrazine to nauplii of the copepodEurytemora affinis and larvae of the sheepshead minnow,Cyprinodon variegatus. Ninety-six-hour LC50 values for the copepod were 0.5 mg 1^?1, 2.6 mg 1^?1, and 13.2 mg 1^?1 at salimities of 5%., 15%. and 25%. respectively. A comparison of LC50 values between adjacent salinities showed a statistical difference between 15%. and 25%. but not between 5%. and 15%.. Atrazine was more toxic toE. affinis at the lowest salinity. The 96-h LC50s for the sheepshead minnow were 16.2 mg 1^?1, 2.3 mg 1^?1, and 2.0 mg 1^?1 at salinities of 5%., 15%., and 25%., respectively. There was a statistical difference between LC50 values at 5%. and 15%. but not between 15%. and 25%.. In contrast toE. affinis results, atrazine was more toxic toC. variegatus at the highest salinity. The toxicity data from these species suggest that development of estuarine water quality criteria is warranted.     

The effects of hydrocarbons on the setting of the American oyster,Crassostrea virginica,in intertidal habitats in Southeastern North Carolina

Effects of petroleum covered substrate on intertidal oyster spat (Crassostrea virginica) set were measured at three intertidal elevations in a southeastern North Carolina estuary.Mercenaria mercenaria shells were coated with Bunker C crude oil or a 40∶1 mixture of gasoline: 2-cycle engine oil and placed intertidally for seven 13-d periods. Spat densities were significantly lower on oil treatments versus control and gas-treated shells in the high intertidal zone. This was principally attributed to an increased sediment coat on oiled shells. Maximum spat size was smaller on oil-treated shells at all elevations when compared to gas and control shells, indicating that setting may be delayed on oiled shell. For all experimental 13-d periods in the low intertidal zone and for three periods in the mid-tidal zone, barnacle densities (primarilyBalanus improvisus andB. eburneus) were significantly greater on oiled shells than on control shells.     

Palynofacies,organic geochemical analyses and hydrocarbon potential of some Upper Jurassic-Lower Cretaceous rocks,the Sabatayn-1 well,Central Yemen

The current work investigates the hydrocarbon potentiality of the upper Jurassic–lower Cretaceous rocks in the Marib-Shabwah Basin, Central Yemen, through the Sabatayn-1 well. Therefore, palynological and organic geochemical analyses were carried out on 37 ditch cutting and 12 core samples from the well. Palynofacies analysis of the Madbi (late Oxfordian–early Tithonian) and Nayfa (Berriasian–Valanginian) Formations sediments indicates deposition of their organic-rich shale, calcareous shale and marl in middle to outer shelf environments under dysoxic–anoxic conditions, containing mainly kerogen of types II to III. However, the shales of the lower Sabatayn (Tithonian) Formation were deposited in an inner shelf environment of prevailing dysoxic–suboxic conditions, and show kerogen types III to II. Regional warm and relatively dry palaeoclimate but with local humid conditions developed near the site of the well is thought to have prevailed during deposition of the studied well sediments. The geochemical analyses of the Madbi Formation show higher total organic carbon content (TOC) than the overlying Sabatayn and Nayfa formations: it is varies between 1.2 and 7, and with average 4 wt% TOC, and the obtained S2 values (～3–10, average 7 mg HC/g rock) indicates that the Madbi Formation is mainly good source rock. It shows a good petroleum potential of 4–11 mg HC/g dry rock, and the Rock-Eval pyrolysis indicates mainly kerogen types II to III (oil to gas prone) of hydrogen index values (132–258, and only one sample from Lam Member is of 360 and average 215 mg HC/g TOC). The thermal maturation parameters as T _max (425–440 °C), production index (average 0.13 mg HC/g rock) and thermal alteration index (2 to 2+) reflected that this formation is present at margin of maturation to early mature stage oil window. So, the Lam Member (upper part) of the Madbi Formation is considered the main hydrocarbon (oil and gas) source rock in the Marib-Shabwah Basin. Accordingly, we predict that the Meem Member is an active source for gas and oil accumulations in the overlying sandstone reservoir of the Sabatayn Formation in the Sabatayn-1 well.     

TheUrquiola oil spill,La Coruña,Spain: Impact and reaction on beaches and rocky coasts

The supertankerUrquiola grounded, exploded, and burned at the entrance to La Coruña harbor (Spain) on May 12, 1976. A total of 100,000 tons of Persian Gulf crude oil was lost, of which about 30,000 tons washed onto shoreline environments. From May 17 to June 10, 1976, the impact and interaction of oil on fine-sand, coarse-sand, and gravel beaches and on sheltered and exposed rocky coasts was monitored in detail. At 32 localities, the beach was profiled, trenched, extensively sampled, and photographed. Another 67 stations were examined for surficial oil coverage and distribution. The surficial distribution of oil on the beaches was influenced primarily by wave activity, tidal stage, and oil quantity. Heaviest accumulations formed along the high-tide swash line. Within beach sediments, oil was present at distinct oiled sediment layers, which were often deeply buried. The depth of burial was related to wave energy and sediment type. Deepest burial (1 m) was on a high-energy, coarse-sand beach (M_z=0.82φ). Burial on fine-sand beaches was less than 30 cm. The thickness of oiled sediment depended on sedimentary characteristics, the quantity of oil present, wave action, and capillary forces. Oil-soaked sediment, as much as 65-cm thick, occurred on coarse-grained beaches. On fine-sand beaches, oiled sediment was limited to thicknesses of 10 cm or less. On rocky shores, oil distribution was determined primarily by wave energy. Along high-energy, cliffed, or steeply dipping rocky areas, wave reflection kept the oil approximately 5 m offshore and contamination was minimal. In low-energy, sheltered areas, oil readily accumulated, causing apparent environmental damage.     

Macrophyte detritus in the winter diet of the estuarine mysid,Neomysis americana

Neomysis americana, a common prey item in the diet of estuarine fish, is seasonally abundant in saltmarsh tidal creeks of North Inlet, South Carolina. Visual examination of mysids collected in winter revealed only diatom tests in their guts, with nearly all of the ingesta unidentifiable. Immunological diet analysis provided strong evidence that proteins fromSpartina alterniflora detritus were present in the guts of field-collected mysids. Laboratory determinations of weight-specific ingestion rates for male and female mysids fed particulateS. alterniflora were best described by a curvilinear quadratic function. Ingestion rates ranged from zero to 0.116 mg C ingested per mg C body weight per hr, or greater than 200% of body carbon per day if continuous feeding is assumed. These high ingestion rates may indicate low assimilation efficiency, but ifN. americana’s assimilation efficiency is similar to that of other mysid species, then this mysid may represent an efficient trophic link between saltmarsh macrophyte production and higher trophic levels. The occurrence ofSpartina detritus in the guts of winter mysids suggests that detritivory may be important during periods of scarce food.