Publications
Permanent URI for this collectionhttps://hdl.handle.net/1969.6/86487
Browse
Browsing Publications by Type "text"
Now showing 1 - 18 of 18
- Results Per Page
- Sort Options
Item A Restoration Suitability Index Model for the Eastern Oyster (Crassostrea virginica) in the Mission-Aransas Estuary, TX, USA(PLOS, 2012) Pollack, Jennifer Beseres; Cleveland, Andrew; Palmer, Terence A.; Reisinger, Anthony S.; Montagna, Paul A.Oyster reefs are one of the most threatened marine habitats on earth, with habitat loss resulting from water quality degradation, coastal development, destructive fishing practices, overfishing, and storm impacts. For successful and sustainable oyster reef restoration efforts, it is necessary to choose sites that support long-term growth and survival of oysters. Selection of suitable sites is critically important as it can greatly influence mortality factors and may largely determine the ultimate success of the restoration project. The application of Geographic Information Systems (GIS) provides an effective methodology for identifying suitable sites for oyster reef restoration and removes much of the uncertainty involved in the sometimes trial and error selection process. This approach also provides an objective and quantitative tool for planning future oyster reef restoration efforts. The aim of this study was to develop a restoration suitability index model and reef quality index model to characterize locations based on their potential for successful reef restoration within the Mission-Aransas Estuary, Texas, USA. The restoration suitability index model focuses on salinity, temperature, turbidity, dissolved oxygen, and depth, while the reef quality index model focuses on abundance of live oysters, dead shell, and spat. Size-specific Perkinsus marinus infection levels were mapped to illustrate general disease trends. This application was effective in identifying suitable sites for oyster reef restoration, is flexible in its use, and provides a mechanism for considering alternative approaches. The end product is a practical decision-support tool that can be used by coastal resource managers to improve oyster restoration efforts. As oyster reef restoration activities continue at small and large-scales, site selection criteria are critical for assisting stakeholders and managers and for maximizing long-term sustainability of oyster resources.Item Arctic Sea Ice Faunal Assemblage: First Approach to Description and Source of the Underice Meiofauna(InterResearch, 1982) Carey, Jr., Andrew G.; Montagna, Paul A.The ice meiofaunal assemblage in shallow Stefansson Sound off the northern coast of Alaska included Polychaeta, Nematoda. Rotifera and Crustacea. The crustaceans conlprised calanoid copepods, nauplii, 2 species of harpacticoids (Halectinosoma neglecturn and Pseudobradya sp.) shared with the benthos and a cyclopoid copepod (Cycloplna gracilis), probably a benthic epiphytic form. Much of the ice meiofaunal assemblage was dominated by larvae and juveniles. The ice taxa were sparse in numbers (100-1,000 tlmes less than the sediments) and depauperate in specles (e.g. 2 species of harpacticoids versus 28 in the sediments). The ice meiofauna appears to be derived from both sediments and water column. We hypothesize that during sprlng the undersurface of nearshore sea ice acts as a substrate for benthic recruitment and for nourishment of a highly selected fauna. However, the meiofauna is too sparse to be significant in the food web or energy budget in the protected nearshore Beaufort Sea.Item Assessment of Longitudinal Gradients in Nematode Communities in the Deep Northern Gulf of Mexico and Concordance with Benthic Taxa(Hindawi, 2012) Sharma, Jyotsna; Baguley, Jeffrey G.; Montagna, Paul A.; Rowe, Gilbert T.Meiobenthic nematode assemblages were examined at 16 stations along two transects on the eastern and western boundaries of the deep northern Gulf of Mexico (dNGOM) at depths of 212–3000 m. The highest abundance (297 individuals 10 cm−2) and number of genera (71) occurred at stations near the Mississippi River delta. Number of genera decreased with increasing depth, and showed differences in community composition between the east and west regions. The dominant family, Comesomatidae, was represented by Sabatieria that was present at most shallow stations but absent at greater water depths. A significant difference in nematode feeding morphology was observed between depth groups but not between the two transects at different longitudes. Patterns of nematode community structure are congruent with harpacticoid copepods. Overall, the higher abundance and diversity of nematodes in the north-central Gulf of Mexico is consistent with findings of other benthic taxa and reflects organic material loading from the Mississippi River driving deep sea communities in the Gulf. The east-west gradient in composition of nematode communities suggests that nematode assemblages have well-defined distribution patterns similar to other meiobenthic taxa in the GOM but they are not aligned in the bathymetric zones observed in macrofauna, megafauna and demersal fishes.Item Benthic metabolism in a natural coastal petroleum seep(InterResearch, 1986) Montagna, Paul A.; Bauer, James E.; Prieto, Maria C.; Hardin, Dane; Spies, Robert B.The rates of 3 processes known to be mediated by microbial metabolic activity were measured in the sediments of a shallow-water (18 m depth) natural petroleum seep and a nearby non- seep area near Santa Barbara, California. Measurements of oxygen flux, hydrocarbon degradation, and sulfate reduction were made in the sediments of 3 stations wlth varying amounts of petroleum seepage. At the seep, 1 station was at the margin of active seepage while the 2nd station (20m away) had moderate seepage. A 3rd non-seep station was 2.4 km away from the petroleum seep area. Total oxygen flux was not staustically different among the 3 stations studied. Rates of sulfate reduction and hydrocarbon degradation were greater at seep than non-seep sites. Within the seep area, greater rates of sulfate reduction and hydrocarbon degradation were found at the station of moderate seepage than at the margin of active oil and gas seepage. The greater rates of metabolism at the seep correlate with previous findings of higher amounts of ATP and macrolnfauna at the seep. We hypothesize that the higher abundances of infauna and concentrations of ATP at the seep are sustained by heterotrophlc bacterial degradation of petroleum and the consumption of those bacteria by infauna.Item Community response of deep-sea soft-sediment metazoan meiofauna to the Deepwater Horizon blowout and oil spill(InterResearch, 2015) Baguley, Jeffrey G.; Montagna, Paul A.; Cooksey, Cynthia; Hyland, Jeffrey L.; Bang, Hyun Woo; Morrison, Colin; Kamikawa, Anthony; Bennets, Paul; Saiyo, Gregory; Parsons, Erin; Herdener, Meredyth; Ricci, MorganThe Deepwater Horizon (DWH) blowout and oil spill of 2010 released an estimated 4.9 million barrels of oil into the Gulf of Mexico. Spill-related contaminants that sank to the seafloor pose risks to benthic fauna living within bottom substrates that are unable to avoid exposure due to their relatively sedentary existence. Metazoan meiofauna are abundant and diverse members of deep-sea soft-sediment communities and play important roles in ecosystem function. We investigated the deep-sea metazoan meiofauna community response to the DWH blowout and oil spill at 66 stations ranging from <1 km to nearly 200 km from the Mississippi Canyon Block 252 wellhead. Metazoan meiofauna abundance, diversity, and the nematode to copepod ratio (N:C) varied significantly across impact zones. Nematode dominance increased significantly with increasing impacts, and N:C spiked near the wellhead. Conversely, major taxonomic diversity and evenness decreased in zones of greater impacts that were in closer proximity to the DWH wellhead. Copepod abundance and the abundance of minor meiofauna taxa decreased where impacts were most severe, and at these severely impacted stations the abundance of ostracods and kinorhynchs was negligible. Increasing abundance and dominance by nematodes with increasing impacts likely represent a balance between organic enrichment and toxicity. Spatial analysis of meiofauna diversity and N:C at 66 stations increased our spatial understanding of the DWH benthic footprint and suggests expanded spatial impacts in areas previously identified as uncertain.Item Deep-Sea Benthic Footprint of the Deepwater Horizon Blowout(PLOS, 2013) Montagna, Paul A.; Baguley, Jeffrey G.; Cooksey, Cynthia; Hartwell, Ian; Hyde, Larry J.; Hyland, Jeffrey L.; Kalke, Richard D.; Kracker, Laura M.; Reuscher, Michael; Rhodes, Adelaide C. E.The Deepwater Horizon (DWH) accident in the northern Gulf of Mexico occurred on April 20, 2010 at a water depth of 1525 meters, and a deep-sea plume was detected within one month. Oil contacted and persisted in parts of the bottom of the deep-sea in the Gulf of Mexico. As part of the response to the accident, monitoring cruises were deployed in fall 2010 to measure potential impacts on the two main soft-bottom benthic invertebrate groups: macrofauna and meiofauna. Sediment was collected using a multicorer so that samples for chemical, physical and biological analyses could be taken simultaneously and analyzed using multivariate methods. The footprint of the oil spill was identified by creating a new variable with principal components analysis where the first factor was indicative of the oil spill impacts and this new variable mapped in a geographic information system to identify the area of the oil spill footprint. The most severe relative reduction of faunal abundance and diversity extended to 3 km from the wellhead in all directions covering an area about 24 km2. Moderate impacts were observed up to 17 km towards the southwest and 8.5 km towards the northeast of the wellhead, covering an area 148 km2. Benthic effects were correlated to total petroleum hydrocarbon, polycyclic aromatic hydrocarbons and barium concentrations, and distance to the wellhead; but not distance to hydrocarbon seeps. Thus, benthic effects are more likely due to the oil spill, and not natural hydrocarbon seepage. Recovery rates in the deep sea are likely to be slow, on the order of decades or longer.Item Dwarf surfclam Mulinia lateralis (Say, 1822) populations and feeding during the Texas brown tide event(National Shellfisheries Association, 1993) Montagna, Paul A.In 1990, there was an unusual brown tide bloom of an aberrant Chrysophyte sp, in Baffin Bay and Laguna Madre near Corpus Christi, Texas. Coincident with the bloom was a dramatic loss of shellfish in Baffin Bay and Laguna Madre, The dominant clam, Mulinia lateralis. disappeared for about two years. Wc performed a series of experiments to determine if disappearance of M. lateralis was related to negative feeding interactions with the brown tide organism, Radioactive tracers were used to compare feeding rates on brown tide, Isochrysis galbana, DUllalielia tertioleera. and Heterocapsa pygmeae. At low cell concentrations « I,000 cells' ml" I), M. lateralis grazing rates (ccll . h-I) increased with concentration and were similar among the microalgal species. At higher concentrations, grazing rates on lsochrysis were inhibited, but remained the same for the other microalgal species. Assimilation efficiency by M. lateralis was lowest on Heterocapsa, and was about the same for the three other species of algae. The high grazing and assimilation rates of brown tide by M. lateralis indicate that the loss of the clam population was not likely caused by a negative trophic effect of the brown tide. Other bloom factors, e.g. reproductive effects or toxic effects, may have contributed to the concomitant loss of the clam population and the occurrence of brown tide. It is also possible that non-bloom factors, e.g. natural population variability increased predation pressure, could have caused the population loss. The reduced populations of filter feeders could have been partially responsible for conditions conducive for the brown tide bloom.Item Global Patterns and Predictions of Seafloor Biomass Using Random Forests(PLOS, 2010) Wei, Chih-Lin; Rowe, Gilbert T.; Escobar-Briones, Elva; Boetius, Antje; Soltwedel, Thomas; Caley, M. Julian; Soliman, Yousria; Huettmann, Falk; Qu, Fangyuan; Yu, Zishan; Pitcher, C. Roland; Haedrich, Richard L.; Wicksten, Mary K.; Rex, Michael A.; Baguley, Jeffrey G.; Sharma, Jyotsna; Danovaro, Roberto; MacDonald, Ian R.; Nunnally, Clifton C.; Deming, Jody W.; Montagna, Paul A.; Lévesque, Mélanie; Weslawski, Jan Marcin; Wlodarska-Kowalczuk, Maria; Ingole, Baban S.; Bett, Brian J.; Billett, David S. M.; Yool, Andrew; Bluhm, Bodil A.; Iken, Katrin; Narayanaswamy, Bhavani E.A comprehensive seafloor biomass and abundance database has been constructed from 24 oceanographic institutions worldwide within the Census of Marine Life (CoML) field projects. The machine-learning algorithm, Random Forests, was employed to model and predict seafloor standing stocks from surface primary production, water-column integrated and export particulate organic matter (POM), seafloor relief, and bottom water properties. The predictive models explain 63% to 88% of stock variance among the major size groups. Individual and composite maps of predicted global seafloor biomass and abundance are generated for bacteria, meiofauna, macrofauna, and megafauna (invertebrates and fishes). Patterns of benthic standing stocks were positive functions of surface primary production and delivery of the particulate organic carbon (POC) flux to the seafloor. At a regional scale, the census maps illustrate that integrated biomass is highest at the poles, on continental margins associated with coastal upwelling and with broad zones associated with equatorial divergence. Lowest values are consistently encountered on the central abyssal plains of major ocean basins The shift of biomass dominance groups with depth is shown to be affected by the decrease in average body size rather than abundance, presumably due to decrease in quantity and quality of food supply. This biomass census and associated maps are vital components of mechanistic deep-sea food web models and global carbon cycling, and as such provide fundamental information that can be incorporated into evidence-based management.Item In situ measurement of meiobenthic grazing rates on sediment bacteria and edaphic diatoms(InterResearch, 1984) Montagna, Paul A.A radioactive tracer technique was used to measure meiofaunal grazing on bacteria and diatom communities in natural sediments. Radioactive '4C-glucose and 14C-bicarbonate were used to label heterotrophs (bacteria) and autotrophs (diatoms), respectively. The labeled compounds were added to undisturbed sediment cores and incubated for 4 h at in situ temperatures. After incubation, radioactivity was determined for the sediment (microbes) and the major meiofaunal taxa. To quantify meiofaunal grazing on microbes, a 3-compartment model was used where: available label is not limiting, microbial uptake is linear, and meiofaunal uptake is hyperbolic. The formula to calculate meiofaunal grazing rate (k) is: k = 2f/t, where f = fraction of meiofaunal radioactivity (DPM) relative to microbial radioactivity at time t. Although microbial actlvity was greater in summer than winter, there were no differences between meiofaunal grazing rates in winter and summer Total meiofaunal ingestion of microbes was dominated by polychaetes. Preliminary results suggest that, on the average, 3 % of the bacteria and 1 % of the diatom communities were removed per hour Thus turnover times of approximately 30 h for bacteria and 6.5 d for diatoms are apparently sufficient to maintain the microbial community in steady state under the meiofaunal grazing regime. This meiofaunal grazing pressure (60 pg bacterial C and 27 pg diatom C ingested 10 cm-2 h-') probably represents a significant stimulatory effect on the microbial community.Item Incorporation of brown tide into an estuarine food web(InterResearch, 1997) Street, G.T.; Montagna, Paul A.; Parker, P.L.In Laguna Madre, Texas, USA, a monospecific brown tide bloom began in January 1990 and was still persisting at the time of this writing. Immediately following the start of the bloom, abundance, biomass and diversity of benthos declined, and have remained low for 6 yr. One explanation for the decline is that the brown tide organism is a poor food source. To determine whether the brown tide was incorporated into the estuarine food web, benthic invertebrates and fish were studied 14 mo after the bloom onset using stable carbon isotope ratios. Fish and benthos were collected from 2 areas, a seagrass habitat in Laguna Madre, and a muddy bottom habitat in the adjacent Alazan Bay. The muddy bottom fauna had a strong brown tide signature, indicating the incorporation of brown tide or brown tide detritus into the food web. The higher-biomass seagrass-fauna had heavier isotope values, reflecting incorporation of seagrass carbon in addition to brown tide. The top predators, Sciaenops ocellatus and Pogonias cromis, have different niches, but were able to switch food sources and thrive during the brown tide bloom. Brown tide appears to be able to support an estuarine food web, but at the expense of benthic diversity. The loss of benthic diversity could be due to allelopathy or the inability of some species to assimilate brown tide. Habitats with extensive seagrass beds maintain higher productivity and diversity than muddy habitats. However, seagrass habitats are endangered because brown tide reduces light levels, inhibits seagrass growth, and is causing seagrass decline.Item Live controls for radioisotope tracer food chain experiments using meiofauna(InterResearch, 1983) Montagna, Paul A.malin poisoned samples are inadequate for measuring the amount of label to be subtracted as control values for certain food chain studies that employ radioactive tracers. In some studies, tracer is added just before incubation to label 'food' during the feeding study. Commonly, parallel, poisoned incubations are used to distinguish between biotic and abiotic label incorporation. But, a poisoned control does not account for label that could enter a consumer via active transport, epicuticular microfloral uptake, or grazing on labeled, non-food particles. Experiments were performed to test if label uptake is greater in live non-grazing than dead organisms. Marine benthic meiofauna incoporate from 3 to 133 times more tracer when they are alive and not grazing than when they are formalin killed. These results suggest that control experiments with live animals be performed to measure all processes by which label can enter consumers in food chain experiments.Item Long-term trends in the response of benthic macrofauna to climate variability in the Lavaca-Colorado Estuary, Texas(InterResearch, 2011) Pollack, Jennifer Beseres; Palmer, Terence A.; Montagna, Paul A.Long-term trends in the response of benthic macrofauna to hydrological conditions were examined in the Lavaca-Colorado Estuary, Texas. Four stations representing a range of salinities in the Lavaca-Colorado Estuary were sampled quarterly for benthic macrofauna and hydrography from April 1988 to October 2008. The relationship between climate variability and local salinity patterns and benthic populations was investigated using the Oceanic Niño Index (ONI), North Atlantic Oscillation (NAO), and North Pacific Index (NPI). Mean salinity declined during the 20 yr study period. Observed changes in salinity were related to river discharge and the ONI because there were more El Niño events in the first half of the study period relative to the second half. Benthic macrofaunal abundance was significantly correlated with salinity, the ONI and the NAO, indicating that global climate variability and the resulting effects on local salinity patterns are important factors shaping benthic macrofaunal communities. There was no significant linear trend in temperature over time, and negative correlations between individual taxa and temperature were likely due to seasonality. While drivers other than physical hydrological factors can obviously affect benthic macrofaunal communities, strong connections between global climate signals, precipitation, and local salinity patterns provided the most plausible mechanistic connection between climatic variability and benthic macrofaunal response in the estuary. An increasingly unstable climate may lead to potentially strong effects in estuarine ecosystems because stability is known to affect diversity and productivity. The vulnerability of estuarine ecosystems to the effects of climate variability will be exacerbated as human population growth and water resource development continues to increase the demand for and stress on coastal and marine resources.Item Role and Value of Nitrogen Regulation Provided by Oysters (Crassostrea virginica) in the Mission-Aransas Estuary, Texas, USA(PLOS, 2013) Pollack, Jennifer Beseres; Yoskowitz, David; Kim, Hae-Cheol; Montagna, Paul A.Suspension-feeding activities of oysters impart a potentially significant benefit to estuarine ecosystems via reduction of water column nutrients, plankton and seston biomass, and primary productivity which can have a significant impact on human well-being. This study considered nitrogen regulation by eastern oysters Crassostrea virginica in the Mission-Aransas Estuary, Texas, USA, as a function of denitrification, burial, and physical transport from the system via harvest. Oyster reefs were estimated to remove 502.5 kg N km−2 through denitrification of biodeposits and 251.3 kg N km−2 in burial of biodeposits to sediments. Nitrogen is also physically transported out of the estuary via harvest of oysters. Commercial harvest of oysters in the Mission-Aransas Estuary can remove approximately 21,665 kg N per year via physical transport from the system. We developed a transferable method to value the service of nitrogen regulation by oysters, where the potential cost equivalent value of nitrogen regulation is quantified via cost estimates for a constructed biological nutrient removal (BNR) supplement to a wastewater treatment plant. The potential annual engineered cost equivalent of the service of nitrogen regulation and removal provided by reefs in the Mission-Aransas Estuary is $293,993 yr−1. Monetizing ecosystem services can help increase awareness at the stakeholder level of the importance of oysters beyond commercial fishery values alone.Item Sampling Design and Enumeration Statistics for Bacteria Extracted from Marine Sediments(American Society for Microbiology, 1982) Montagna, Paul A.The spatial and temporal distributions of marine bacteria were studied at both a muddy and a sandy subtidal site in North Inlet, S.C. The sampling design was hierarchical, since subsampling (by a dilution series) of the sediments was necessary to count bacterial cells using acridine orange epifluoresence microscopy. The cell count data fit a log-normal distribution. The abundance of bacteria was 1011 g−1 (dry weight) of mud and 109 g−1 (dry weight) of sand. Variance component analyses demonstrated that variation due to the subsampling procedures was always statistically significant. Thus the common practice of counting 20 fields from one filter preparation is inadequate for estimating the true bacterial population variance in marine sediments. It is recommended that replication of the subsampling level be performed. Standardization of data (by dry weight of sediment) decreased sampling variance at the mud site but not at the sand site, implying that bacteria are more homogeneously distributed in sand than in mud.Item Temporal and spatial patterns of anthropogenic disturbance at McMurdo Station, Antarctica(Institute of Physics, 2010) Kennicutt II, Mahlon C; Klein, Andrew; Montagna, Paul A.; Sweet, Stephen; Wade, Terry; Palmer, Terence A.; Sericano, Jose; Denoux, GuyHuman visitations to Antarctica have increased in recent decades, raising concerns about preserving the continent's environmental quality. To understand the spatial and temporal patterns of anthropogenic disturbances at the largest scientific station in Antarctica, McMurdo Station, a long-term monitoring program has been implemented. Results from the first nine years (1999–2007) of monitoring are reported. Most physical disturbance of land surfaces occurred prior to 1970 during initial establishment of the station. Hydrocarbons from fuel and anthropogenic metals occur in patches of tens to hundreds of square meters in areas of fuel usage and storage. Most soil contaminant concentrations are not expected to elicit biological responses. Past disposal practices have contaminated marine sediments with polychlorinated biphenyls (PCBs), petroleum hydrocarbons, and metals in close proximity to the station that often exceed concentrations expected to elicit biological responses. Chemical contamination and organic enrichment reduced marine benthic ecological integrity within a few hundred meters offshore of the station. Contaminants were detected in marine benthic organisms confirming bioavailability and uptake. PCBs in sediments are similar to suspected source materials, indicating minimal microbial degradation decades after release. Anthropogenic disturbance of the marine environment is likely to persist for decades. A number of monitoring design elements, indicators and methodologies used in temperate climates were effective and provide guidance for monitoring programs elsewhere in Antarctica.Item Temporal variability and the relationship between benthic meiofaunal and microbial populations of a natural coastal petroleum seep(Yale Peabody Museum, 1987) Montagna, Paul A.; Bauer, James E.; Toal, Jon; Hardin, Dane; Spies, Robert B.Previous studies of the Isla Vista petroleum seep in the Santa Barbara Channel found much higher abundances of macrofauna and concentrations of adenosine triphosphate (ATP) in sediments near petroleum seepage compared to those from nonseep areas. To further assess the possible effect of petroleum on organisms at the base of benthic food webs, population abundances of meiobenthos and their suspected microbial food (bacteria and diatoms) were measured biweekly for one year at three stations with differing petroleum exposure. Determinations of suspended particulate matter and the abundance and gut contents of juvenile fishes were also made at seep and nonseep stations.Nematodes and bacteria had higher abundances in areas of active petroleum seepage than in areas of moderate seepage (within 20 m) or no seepage (1.4 km away). Bacterial productivity (based on the frequency of dividing cells) was 340% greater in sediments from areas of active seepage compared to those from a nonseep station. Sediments within the seep, but away from active seepage, had rates of bacterial productivity 15 times greater than a nonseep comparison site. Densities of harpacticoid copepods and their probable principal food, diatoms, were not affected by petroleum seepage. Suspended organic matter caught in settling traps was not different between seep and nonseep stations. In addition, there was no evidence that predation pressure by juvenile fish on meiofauna was different between stations.The higher bacterial biomass and productivity in areas of petroleum seepage are consistent with the hypothesis that petroleum carbon is available for assimilation by sediment bacteria. The enhanced level of microbial carbon associated with the petroleum seep is available for consumption by benthic invertebrates and could explain the higher abundances of macrofauna and meiofauna found there.Item Utilization of estuarine organic matter during growth and migration by juvenile brown shrimp Penaeus aztecus in a South Texas estuary(InterResearch, 2000) Riera, P.; Montagna, Paul A.; Kalke, R.D.; Richard, P.The trophic dynamic links of migratory juvenile brown shrimp Penaeus aztecus were investigated along the South Texas coast from the Aransas Pass to Corpus Christi and Nueces Bay and to the nursery ground in the Nueces Delta. Shrimps and their potential food sources were measured for δ13C and δ15N ratios between December 1995 and July 1996. During this period, shrimp length increased from 10 to 11 mm, when the animals entered Corpus Christi Bay as larvae, to 80-90 mm, when they returned to Mexico Gulf as sub-adults. Brown shrimp exhibited spatial and temporal δ13C variation (from -25.2 to 12.5”), indicating a high diversity of food sources throughout their migration. From δ13C values, the main sources used as food sources by juvenile brown shrimp in the Rincon Bayou marsh were Spartina alterniflora and S. spartinae detritus and benthic diatoms. δ13C and δ15N values showed that organic matter inputs carried by the river inflow can also contribute significantly to the feeding of migratory brown shrimp. In these marsh habitats, shrimp isotopic ratios changed rapidly, suggesting high tissue turnover rates. The study showed that coastal marshes after restoration through the introduction of freshwater inflow may provide feeding habitats favorable for growth and development of juvenile brown shrimp.Item Vertical distribution of microbial and meiofaunal populations in sediments of a natural coastal hydrocarbon seep(Yale Peabody Museum, 1989) Montagna, Paul A.; Bauer, James E.; Hardin, Dane; Spies, Robert B.We studied the vertical distribution of microbes and meiofauna in natural hydrocarbon seep sediments to determine if there was a relationship between profiles of benthic trophic structure and the unique biogeochemical conditions present at the seep. Three stations in the Santa Barbara Channel represented a gradient of natural petroleum seepage, from very active, to moderate, to none. Seasonal differences were examined by sampling in the three major oceanographic seasons, upwelling (April), mixed (July), and Davidson (December). Densities of microbes and meiofauna were highest in July, and decreased in winter. All population sizes decreased with increasing depth in the sediment. Harpacticoids and Chl a were practically restricted to the surface sediments. Harpacticoids and Chl a were more dense (number per unit volume or strata of sediment) and abundant (number per unit area of sediment or sum of the strata) at the comparison site than at the seep sites. Density and abundance of nematodes, bacteria cell counts, and bacterial biomass were greater at the station with the most active seepage rates. Bacterial biovolumes appeared constant among sediment depths and stations, but cell biovolumes were larger in July. The data are consistent with the hypothesis that organic enrichment via petroleum utilization is responsible for increased abundances of bacteria and nematodes at the seep. There were strong correlations between densities of harpacticoids and microalgae, and densities of nematodes and bacteria. These links indicate that seeping petroleum might have an enhanced effect on the detrital (bacterial based) food web, but a toxic effect on the grazing (microalgal based) food web.