Lafayette, LA, United States
Lafayette, LA, United States

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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.


Ramsey Elijah E.,U.S. Geological Survey | Rangoonwala A.,IAP World Services Inc. | Rangoonwala A.,Five Rivers Services LLC | Suzuoki Y.,ASci Corporation | Jones C.E.,Jet Propulsion Laboratory
Remote Sensing | Year: 2011

The National Aeronautics and Space Administration's airborne Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) was deployed in June 2010 in response to the Deepwater Horizon oil spill in the Gulf of Mexico. UAVSAR is a fully polarimetric L-band Synthetic Aperture Radar (SAR) sensor for obtaining data at high spatial resolutions. Starting a month prior to the UAVSAR collections, visual observations confirmed oil impacts along shorelines within northeastern Barataria Bay waters in eastern coastal Louisiana. UAVSAR data along several flight lines over Barataria Bay were collected on 23 June 2010, including the repeat flight line for which data were collected in June 2009. Our analysis of calibrated single-look complex data for these flight lines shows that structural damage of shoreline marsh accompanied by oil occurrence manifested as anomalous features not evident in pre-spill data. Freeman-Durden (FD) and Cloude-Pottier (CP) decompositions of the polarimetric data and Wishart classifications seeded with the FD and CP classes also highlighted these nearshore features as a change in dominant scattering mechanism. All decompositions and classifications also identify a class of interior marshes that reproduce the spatially extensive changes in backscatter indicated by the pre- and post-spill comparison of multi-polarization radar backscatter data. FD and CP decompositions reveal that those changes indicate a transform of dominant scatter from primarily surface or volumetric to double or even bounce. Given supportive evidence that oil-polluted waters penetrated into the interior marshes, it is reasonable that these backscatter changes correspond with oil exposure; however, multiple factors prevent unambiguous determination of whether UAVSAR detected oil in interior marshes. © 2011 by the authors.


Ramsey III E.,U.S. Geological Survey | Werle D.,AERDE Environmental Research | Suzuoki Y.,ASci Corporation | Suzuoki Y.,Japan Space Imaging Corporation | And 3 more authors.
Journal of Coastal Research | Year: 2012

Storm-surge flooding and marsh response throughout the coastal wetlands of Louisiana were mapped using several types of remote sensing data collected before and after Hurricanes Gustav and Ike in 2008. These included synthetic aperture radar (SAR) data obtained from the (1) C-band advance SAR (ASAR) aboard the Environmental Satellite, (2) phased-array type L-band SAR (PALSAR) aboard the Advanced Land Observing Satellite, and (3) optical data obtained from Thematic Mapper (TM) sensor aboard the Land Satellite (Landsat). In estuarine marshes, L-band SAR and C-band ASAR provided accurate flood extent information when depths averaged at least 80 cm, but only L-band SAR provided consistent subcanopy detection when depths averaged 50 cm or less. Low performance of inundation mapping based on C-band ASAR was attributed to an apparent inundation detection limit (>30 cm deep) in tall Spartina alterniflora marshes, a possible canopy collapse of shoreline fresh marsh exposed to repeated storm-surge inundations, wind-roughened water surfaces where water levels reached marsh canopy heights, and relatively high backscatter in the near-range portion of the SAR imagery. A TM-based vegetation index of live biomass indicated that the severity of marsh dieback was linked to differences in dominant species. The severest impacts were not necessarily caused by longer inundation but rather could be caused by repeated exposure of the palustrine marsh to elevated salinity floodwaters. Differential impacts occurred in estuarine marshes. The more brackish marshes on average suffered higher impacts than the more saline marshes, particularly the nearshore coastal marshes occupied by S. alterniflora. © 2012, the Coastal Education & Research Foundation (CERF).


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 (


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).


Marancik K.E.,National Oceanic and Atmospheric Administration | Marancik K.E.,IAP World Services Inc. | Richardson D.E.,National Oceanic and Atmospheric Administration | Lyczkowski-Shultz J.,National Oceanic and Atmospheric Administration | And 2 more authors.
Fishery Bulletin | Year: 2012

Little is known about the seasonality and distribution of grouper larvae (Serranidae: Epinephelini) in the Gulf of Mexico and Atlantic Ocean off the coast of the southeast United States. Grouper larvae were collected from a transect across the Straits of Florida in 2003 and 2004 and during the Southeast Area Monitoring and Assessment Program spring and fall surveys from 1982 through 2005. Analysis of these larval data provided information on location and timing of spawning, larval distribution patterns, and interannual occurrence for a group of species not easily studied as adults. Our analyses indicated that shelf-edge habitat is important for spawning of many species of grouper-some species for which data were not previously available. Spawning for some species may occur year-round, but two peak seasons are evident: late winter and late summer through early fall. Interannual variability in the use of three important subregions by species or groups of species was partially explained by environmental factors (surface temperature, surface salinity, and water depth). A shift in species dominance over the last three decades from spring-spawned species (most of the commercial species) to fall-spawned species also was documented. The results of these analyses expand our understanding of the basic distribution and spawning patterns of northwest Atlantic grouper species and indicate a need for further examination of the changing population structure of individual species and species dominance in the region.


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.


Boustany R.G.,U.S. Geological Survey | Boustany R.G.,U.S. Department of Agriculture | Michot T.C.,U.S. Geological Survey | Moss R.F.,IAP World Services Inc.
Wetlands Ecology and Management | Year: 2010

A mesocosm study was conducted to determine the effects of variable salinity and light on Vallisneriaamericana Michx. (wild celery) and associated algal community components in the lower St. Johns River, Florida. Fifteen centimeter diameter intact plant plugs were collected from the LSJR in March 2001 and transported to mesocosm facilities in Lafayette, Louisiana. A factorial experimental design was used consisting of three salinity levels (1, 8, and 18 ppt), three light levels (0, 50, and 90% shading), and three replicate mesocosms of each for a total of 27 mesocosms. The experiment consisted of a 4-week acclimation period followed by a 5-month treatment period. V. americana responded negatively to increased salinity. Although V. americana survived 8 ppt salinity, growth was limited. At 18 ppt, almost all V. americana aboveground biomass had perished within 10 weeks, but when salinity was lowered back to 1 ppt, approximately 20% of the aboveground biomass recovered within the following 10 weeks. At midtreatment harvest, light did not affect V. americana biomass directly (P = 0. 8240), but by final harvest (20 weeks) light affected belowground biomass (P < 0. 0014). Both salinity and light affected algal growth. Macroalgae dominated 1 ppt salinity treatments in ambient light, but phytoplankton dominated 8 and 18 ppt salinity treatments in ambient light. Algal communities were greatly inhibited by 90% shading. While salinity directly impacted V. americana growth and survival, light effects were less direct and involved algal community associations. © Springer Science+Business Media B.V. 2009.


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


Doyle T.W.,U.S. Geological Survey | Krauss K.W.,U.S. Geological Survey | Conner W.H.,Clemson University | From A.S.,IAP World Services Inc.
Forest Ecology and Management | Year: 2010

Tidal freshwater forests in coastal regions of the southeastern United States are undergoing dieback and retreat from increasing tidal inundation and saltwater intrusion attributed to climate variability and sea-level rise. In many areas, tidal saltwater forests (mangroves) contrastingly are expanding landward in subtropical coastal reaches succeeding freshwater marsh and forest zones. Hydrological characteristics of these low-relief coastal forests in intertidal settings are dictated by the influence of tidal and freshwater forcing. In this paper, we describe the application of the Sea Level Over Proportional Elevation (SLOPE) model to predict coastal forest retreat and migration from projected sea-level rise based on a proxy relationship of saltmarsh/mangrove area and tidal range. The SLOPE model assumes that the sum area of saltmarsh/mangrove habitat along any given coastal reach is determined by the slope of the landform and vertical tide forcing. Model results indicated that saltmarsh and mangrove migration from sea-level rise will vary by county and watershed but greater in western Gulf States than in the eastern Gulf States where millions of hectares of coastal forest will be displaced over the next century with a near meter rise in relative sea level alone. Substantial losses of coastal forests will also occur in the eastern Gulf but mangrove forests in subtropical zones of Florida are expected to replace retreating freshwater forest and affect regional biodiversity. Accelerated global eustacy from climate change will compound the degree of predicted retreat and migration of coastal forests with expected implications for ecosystem management of State and Federal lands in the absence of adaptive coastal management.

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