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Lafayette, LA, United States

Sibrell P.L.,U.S. Geological Survey | Tucker T.W.,IAP World Services Inc.
Water, Air, and Soil Pollution | Year: 2012

Phosphorus (P) releases to the environment have been implicated in the eutrophication of importantwater bodies worldwide. Current technology for the removal of P from wastewaters consists of treatment with aluminum (Al) or iron (Fe) salts, but is expensive. The neutralization of acid mine drainage (AMD) generates sludge rich in Fe and Al oxides that has hitherto been considered a waste product, but these sludges could serve as an economical adsorption media for the removal of P from wastewaters. Therefore, we have evaluated an AMD-derived media as a sorbent for P in fixed bed sorption systems. The homogenous surface diffusion model (HSDM) was used to analyze fixed bed test data and to determine the value of related sorption parameters. The surface diffusion modulus Ed was found to be a useful predictor of sorption kinetics. Values of Ed<0.2 were associated with early breakthrough of P, while more desirable S-shaped breakthrough curves resulted when 0.2 Source

Ramsey E.,U.S. Geological Survey | Rangoonwalaj A.,IAP World Services Inc. | Thomsen M.S.,Edith Cowan University | Thomsen M.S.,National Environmental Research Institute of Denmark | Schwarzschild A.,University of Virginia
International Journal of Remote Sensing | Year: 2012

We have developed methods to determine the visible (VIS) to near-infrared (NIR) spectral properties of thalli and epiphytes of bloom-forming and green macro-phyte Ulva curvata in back-barrier lagoons in Virginia, USA. A 2% increase in NIR thalli reflectance from winter to summer (ca. 9.5%) matched the drop in summer NIR transmittance (ca. 90%). In contrast, summer and winter VIS reflectance (reaching 6%) were nearly identical while winter transmittance (ca. 85%) was 10-20% higher. NIR absorption remained at 5% but VIS absorption increased by 10-20% from winter to summer. Replicate consistency substantiated the high transmittance difference indicating thallus composition changed from summer to winter. Epiphytes increased thallus reflectance ( Source

Persson J.,University of Oslo | Fink P.,University of Cologne | Goto A.,Tohoku University | Hood J.M.,University of Minnesota | And 2 more authors.
Oikos | Year: 2010

Homeostasis of element composition is one of the central concepts of ecological stoichiometry. In this context, homeostasis is the resistance to change of consumer body composition in response to the chemical composition of consumer's food. To simplify theoretical analysis, it has generally been assumed that autotrophs exhibit flexibility in their composition, while heterotrophs are confined to a constant (strictly homeostatic) body composition. Yet, recent studies suggest that heterotrophs are not universally strictly homeostatic. We examined the degree to which autotrophs and heterotrophs regulate stoichiometric homeostasis (P:C, N:C, N:P, or %P and %N). We conducted a quantitative review and meta-analysis using 132 datasets extracted from 57 literature sources which examined the dependence of organismal stoichiometry on resource stoichiometry. Among individual datasets, there was a wide range of responses from strictly homeostatic to non-homeostatic. Even within heterotrophic organisms, varying levels of homeostasis were observed. Comparing the degree of homeostasis between organisms based on large-scale habitat types using meta-analysis indicated some significant differences between groups. For example, aquatic macroinvertebrates were significantly more homeostatic in terms of P:C than terrestrial invertebrates. Our meta-analysis also confirmed that, with regard to N:P, heterotrophs are significantly more homeostatic than autotrophs. Furthermore, our analysis indicated that the homeostasis parameter 1/H, despite being a potentially useful predictive metric, has to be utilized with caution since it oversimplifies some important aspects of the responses of organisms to elemental imbalances. This critical evaluation of stoichiometric homeostasis contributes to a better understanding of many food-web interactions, which are commonly driven by elemental imbalances between consumers and their resources. © 2010 The Authors. Source

Jonas J.L.,IAP World Services Inc. | Jonas J.L.,Colorado State University | Buhl D.A.,U.S. Geological Survey | Symstad A.J.,U.S. Geological Survey
Ecology | Year: 2015

Better understanding the influence of precipitation and temperature on plant assemblages is needed to predict the effects of climate change. Many studies have examined the relationship between plant productivity and weather (primarily precipitation), but few have directly assessed the relationship between plant richness or diversity and weather despite their increased use as metrics of ecosystem condition. We focus on the grasslands of central North America, which are characterized by high temporal climatic variability. Over the next 100 years, these grasslands are predicted to experience further increased variability in growing season precipitation, as well as increased temperatures, due to global climate change. We assess the portion of interannual variability of richness and diversity explained by weather, how relationships between these metrics and weather vary among plant assemblages, and which aspects of weather best explain temporal variability. We used an information-theoretic approach to assess relationships between long-term plant richness and diversity patterns and a priori weather covariates using six data sets from four grasslands. Weather explained up to 49% and 63% of interannual variability in total plant species richness and diversity, respectively. However, richness and diversity responses to specific weather variables varied both among sites and among experimental treatments within sites. In general, we found many instances in which temperature was of equal or greater importance as precipitation, as well as evidence of the importance of lagged effects and precipitation or temperature variability. Although precipitation has been shown to be a key driver of productivity in grasslands, our results indicate that increasing temperatures alone, without substantial changes in precipitation patterns, could have measurable effects on Great Plains grassland plant assemblages and biodiversity metrics. Our results also suggest that richness and diversity will respond in unique ways to changing climate and management can affect these responses; additional research and monitoring will be essential for further understanding of these complex relationships. © 2015 by the Ecological Society of America. Source

Krauss K.W.,U.S. Geological Survey | From A.S.,IAP World Services Inc. | Doyle T.W.,U.S. Geological Survey | Doyle T.J.,U.S. Fish and Wildlife Service | Barry M.J.,The Institute for Regional Conservation
Journal of Coastal Conservation | Year: 2011

The Ten Thousand Islands region of southwestern Florida, USA is a major feeding and resting destination for breeding, migrating, and wintering birds. Many species of waterbirds rely specifically on marshes as foraging habitat, making mangrove encroachment a concern for wildlife managers. With the alteration of freshwater flow and sea-level rise trends for the region, mangroves have migrated upstream into traditionally salt and brackish marshes, mirroring similar descriptions around the world. Aside from localized freezes in some years, very little seems to be preventing mangrove encroachment. We mapped changes in mangrove stand boundaries from the Gulf of Mexico inland to the northern boundary of Ten Thousand Islands National Wildlife Refuge (TTINWR) from 1927 to 2005, and determined the area of mangroves to be approximately 7,281 hectares in 2005, representing an 1,878 hectare increase since 1927. Overall change represents an approximately 35% increase in mangrove coverage on TTINWR over 78 years. Sea-level rise is likely the primary driver of this change; however, the construction of new waterways facilitates the dispersal of mangrove propagules into new areas by extending tidal influence, exacerbating encroachment. Reduced volume of freshwater delivery to TTINWR via overland flow and localized rainfall may influence the balance between marsh and mangrove as well, potentially offering some options to managers interested in conserving marsh over mangrove. © 2011 Springer Science+Business Media B.V. (outside the USA). Source

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