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Caffrey J.M.,University of West Florida | Hollibaugh J.T.,University of Georgia | Bano N.,University of Georgia | Haskins J.,Elkhorn Slough National Estuarine Research Reserve
Aquatic Microbial Ecology | Year: 2010

We examined short-term variability in sediment microbial processes and biogeochemistry in response to decreased irradiance accompanying an upwelling event. Potential nitrification, extractable nutrients, solid phase iron and pore water sulfide concentrations were measured several times at 3 locations in Elkhorn Slough, California, USA. Benthic fluxes of nitrate+nitrite, ammonium, phosphate, sediment oxygen consumption and denitrification from N 2/Ar flux were also measured. Fog that was associated with upwelling in Monterey Bay reduced photosynthetically active radiation in Elkhorn Slough, which led to increased duration of water column hypoxia. Solid phase Fe 3+ concentrations and potential nitrification rates declined while pore water sulfide increased over this period. While potential nitrification rates from this study are lower than rates from estuaries that do not experience hypoxia or anoxia, nitrifiers in Elkhorn Slough appear to be capable of adjusting to changing environmental conditions, specifically of tolerating low levels of sulfide. The nitrifying assemblage was similar to the community of ammonia-oxidizing bacteria and ammonia-oxidizing archaea that was previously reported from this system. Eutrophic shallow estuaries like Elkhorn Slough are delicately poised such that their sediment biogeochemistry responds quickly to relatively small changes in the light environment. © Inter-Research 2010. Source

Fork S.K.,Elkhorn Slough National Estuarine Research Reserve
Environmental Entomology | Year: 2010

Biological invasions by nonnative plant species are a widespread phenomenon. Many studies have shown strong ecological impacts of plant invasions on native plant communities and ecosystem processes. Far fewer studies have examined effects on associated animal communities. From the perspective of a reserve's land management, I addressed the question of whether arthropod assemblages on two nonnative plant species of concern were impoverished compared with those assemblages associated with two predominant native plant species of that reserve. If the nonnative plant species, Conium maculatum L., and Phalaris aquatica L., supported highly depauperate arthropod assemblages compared with the native plant species, Baccharis pilularis De Candolle and Leymus triticoides (Buckley) Pilger, this finding would provide additional support for prioritizing removal of nonnatives and restoration of natives. I assessed invertebrate assemblages at the taxonomic levels of arthropod orders, Coleoptera families, and Formicidae species, using univariate analyses to examine community attributes (richness and abundance) and multivariate techniques to assess arthropod assemblage community composition differences among plant species. Arthropod richness estimates by taxonomic level between native and nonnative vegetation showed varying results. Overall, arthropod richness of the selected nonnative plants, examined at higher taxonomic resolution, was not necessarily less diverse than two of common native plants found on the reserve, although differences were found among plant species. Impacts of certain nonnative plant species on arthropod assemblages may be more difficult to elucidate than those impacts shown on native plants and ecosystem processes. © 2010 Entomological Society of America. Source

Watson E.B.,University of California at Davis | Pasternack G.B.,University of California at Davis | Gray A.B.,University of California at Davis | Goni M.,Oregon State University | Woolfolk A.M.,Elkhorn Slough National Estuarine Research Reserve
Estuarine, Coastal and Shelf Science | Year: 2013

Recent studies of estuarine sediment deposits have focused on grain size spectra as a tool to better understand depositional processes, in particular those associated with tidal inlet and basin dynamics. The key to accurate interpretation of lithostratigraphic sequences is establishing clear connections between morphodynamic changes and the resulting shifts in sediment texture. Here, we report on coupled analysis of shallow sediment profiles from a closed estuarine lagoon in concert with recent changes in lagoon morphology reconstructed from historic sources, with a specific emphasis on the ability of suite statistics to provide meaningful insights into changes in sediment transport agency. We found that a major reorganization in lagoon morphology, dating to the 1940s, was associated with a shift in sediment deposition patterns. The restricted inlet was associated with deposition of sediments that were finer, less negatively skewed, and less leptokurtic in distribution than sediments deposited while the lagoon had a more open structure. These shifts are associated with a change in transport process from fluvial (through-flow) to closed basin (trapping). We also found other chemostratigraphic changes accompanying this shift in sediment texture, reflecting changes in organic matter source, wetland species composition, and an increase in sediment organic content, as presumably coarse, well-ventilated floodplain sediments tend to result in mineralization rather than sequestration of organic matter. In conclusion, we found that grain size analysis, in concert with the suite statistics technique, reflected changes in coastal configuration supported by historic maps and photos, however, we also recognize that this analysis was more informative given further context through additional sedimentary analyses. These findings provide a basis for the interpretation of particle size distribution in lithostratigraphic sequences associated with bar-built estuaries, where understanding natural and anthropogenically-modified inlet dynamics may help shape conservation management where concerns exist with respect to fish passage, water quality, and sediment transport. © 2013. Source

Wasson K.,Elkhorn Slough National Estuarine Research Reserve
Wetlands | Year: 2010

The goal of this investigation was to inform restoration strategies by determining which factors are most important in limiting Olympia oyster (Ostrea lurida) distribution and abundance at a Pacific coast estuary, Elkhorn Slough in central California, where Olympia oysters are currently extremely rare but were formerly abundant. An array of mensurative experiments and correlative analyses were used to examine the role of potential limiting factors. Absence of oysters was associated with symptoms of eutrophication, including elevated nutrient concentrations and turbidity. Oysters were also absent from all sites where water control structures resulted in minimal tidal exchange. Predation and competition did not appear to play a major role in surveyed oyster populations above Mean Lower Low Water but at lower elevations oysters were heavily fouled by non-native species. In most sites oysters were found only on large artificial substrates; survival on small natural hard substrates was apparently precluded by burial by fine sediments. Restoring more natural ecosystem processes by reducing nutrient and sediment inputs, increasing tidal exchange to areas behind water control structures, and preventing establishment of new non-native species would benefit Olympia oysters as well as support broader ecosystem-based management goals. © 2010 Society of Wetland Scientists. Source

Anderson B.,University of California at Davis | Phillips B.,University of California at Davis | Hunt J.,University of California at Davis | Largay B.,Elkhorn Slough National Estuarine Research Reserve | And 2 more authors.
Environmental Toxicology and Chemistry | Year: 2011

The California, USA, central coast is one of the most productive agricultural areas in the world, and numerous stakeholders are working there to implement conservation practices to reduce contaminated runoff. Practices include vegetated treatment systems (VTS) designed to promote contaminant reduction and breakdown. The current study evaluated the effectiveness of a vegetated drainage ditch incorporating a sedimentation basin, a vegetated section, and a Landguard organophosphate-A (OP-A) enzyme dosing system. The VTS was constructed on a working farm and was designed to remove organophosphate and pyrethroid pesticides, the primary pesticides causing toxicity in Salinas Valley watersheds. The present study was conducted during five separate irrigation events on tailwater runoff containing mixtures of pesticides and suspended sediments. Water samples were collected at four stations within the system, and these were subjected to chemical analyses and tested for toxicity to Ceriodaphnia dubia. All inflow samples were highly toxic to C. dubia, and this was largely because of diazinon. Treatment of diazinon-contaminated runoff was only partially effective using aquatic vegetation. All diazinon remaining after vegetated treatment was effectively removed after treatment with the Landguard OP-A enzyme. Chemical analysis of the VTS water samples showed that pyrethroid and organochlorine pesticide concentrations in water were greatly reduced in the sedimentation section of the ditch, and these pesticides were further reduced in the vegetated section of the ditch. The overall conclusion from these analyses is that the VTS was effective at reducing the more hydrophobic organochlorine and pyrethroid pesticides from water. The water-soluble pesticide diazinon was not sufficiently removed during the VTS residence times observed in this study; however, residual diazinon was effectively removed using Landguard OP-A. © 2011 SETAC. Source

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