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Silver Spring, MD, United States

Tipping P.W.,U.S. Department of Agriculture | Martin M.R.,USFWS | Bauer L.,Center for Coastal Monitoring and Assessment | Pierce R.M.,Alan Plummer Associates Inc. | Center T.D.,U.S. Department of Agriculture
Aquatic Botany | Year: 2012

Populations of the floating macrophyte, . Salvinia minima Baker, were assessed over a 39-month period at four sites in southern Florida in order to elucidate the abiotic and biotic factors that influenced their density. These factors included the abundance of other plant species, changes in water depth, water quality, and herbivory by insects. Abiotic factors like temperature, pH, DO, and conductivity varied among sites and, more importantly, over time. The same was true for . S. minima biomass, coverage, and condition. Principal component analysis identified four components which together explained 64% of the variability in . S. minima biomass. The first component correlated strongly with herbivory from . Cyrtobagous salviniae Calder and Sands and . Synclita obliteralis (Walker) as well as the abundance of the duckweed . Spirodela polyrrhiza (L.) Schleid. Temperature effects were strongly represented in the second principal component. A stepwise regression model that best predicted . S. minima biomass incorporated conductivity, insect herbivory, and interspecific plant abundance. Broader dry vs. wet season influences were apparent and linked to temperature, water depth, and conductivity that covaried with . S. minima biomass. Sites where water depth changed the most had the least . S. minima. Insect herbivory did not increase under more stagnant conditions when plant populations were less mobile. Overall, . S. minima populations cycled in southern Florida in response to a shifting array of abiotic and biotic factors. The relative importance of these factors was less clear although the influences of herbivory, temperature, and the presence of other plants were significant. © 2012. Source

Simmonds S.E.,University of California at Los Angeles | Kinlan B.P.,Center for Coastal Monitoring and Assessment | Kinlan B.P.,Consolidated Safety Services Inc. | White C.,California Polytechnic State University, San Luis Obispo | And 3 more authors.
Marine Ecology Progress Series | Year: 2014

Using calcified structures as natural geochemical tags to estimate levels of population connectivity is becoming increasingly common. However, the technique suffers from several logistical and statistical problems that constrain its full application. Foremost is that only a subset of potential sources is sampled, often compounded by under-sampling within locations at an overly coarse spatial scale. This introduces unknown error and prevents the creation of a rangewide connectivity matrix. To address this issue, we analyzed the natural geochemical tags of embryonic statoliths in the whelk Kelletia kelletii (Forbes, 1850). We sampled from 23 sites over the entire geographic range in 2004 and 2005 from Monterey (California, USA) (36°N) to Isla Asunción, (Baja California, Mexico) (27°N). We then used geospatial statistics (kriging) to make continuous along-coast maps of embryonic statolith chemistry. This allowed us to estimate chemistry at unsampled locations. We used this new continuous assignment method to estimate the spatial error associated with assignment by the classic method of discriminant function analysis (DFA). Then, we compared the performance of the 2 methods at classifying unknown embryonic statoliths. We found large spatial errors often associated with DFA assignments, even when traditional DFA accuracy assessments indicated the method was performing well. The continuous method provided an improved assessment of uncertainty in assignments. It outperformed the DFA method in classifying unknown embryos to the vicinity of their true source. Geospatial statistics also provided useful information on other range-wide variables, such as adult reproductive abundance. As a proxy for larval supply, such information can aid future assignments of recruits. Our combined analyses help inform sampling designs and motivate the development of a new approach for population connectivity studies. © Inter-Research 2014. Source

Whitall D.,Center for Coastal Monitoring and Assessment | Pait A.,Center for Coastal Monitoring and Assessment | Ian Hartwell S.,Center for Coastal Monitoring and Assessment
Marine Environmental Research | Year: 2015

Land based sources of pollution have the potential to negatively impact coral reef ecosystems. Many coral systems, including environmentally sensitive marine protected areas, do not have assessments of their chemical contaminant status (magnitude and extent). Without a status assessment, it is impossible to measure change in a system. This study presents surficial sediment data from Coral and Fish Bays (St. John, US Virgin Islands (USVI)). Portions of these bays are included in Virgin Islands National Park, and Virgin Islands Coral Reef National Monument. A suite of analytes (PCBs, PAHs, pesticides, heavy metals, butyltins) was quantified and compared against other regional data and against previously published sediment quality guidelines (SQG). Contamination from toxic contaminants in the system was generally low when compared to other similar studies and potential toxicity thresholds (SQG). Exceptions to this were copper and total chlordane which exceeded the Effects Range Low (ERL) sediment quality guideline, indicating possible sediment toxicity. This assessment will be useful to coastal managers for tracking environmental change, and ensuring that this marine protected area remains relatively free from toxic contamination. © 2015. Source

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