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Slone D.H.,U.S. Geological Survey | Reid J.P.,U.S. Geological Survey | Kenworthy W.J.,Center for Coastal Fisheries and Habitat Research
Marine Ecology Progress Series | Year: 2013

Turbid water conditions make the delineation and characterization of benthic habitats difficult by traditional in situ and remote sensing methods. Here, we develop and validate modeling and sampling methodology for detecting and characterizing seagrass beds by analyzing GPS telemetry records from radio-tagged manatees. Between October 2002 and October 2005, 14 manatees were tracked in the Ten Thousand Islands (TTI) in southwest Florida (USA) using Global Positioning System (GPS) tags. High density manatee use areas were found to occur off each island facing the open, nearshore waters of the Gulf of Mexico. We implemented a spatially stratified random sampling plan and used a camera-based sampling technique to observe and record bottom observations of seagrass and macroalgae presence and abundance. Five species of seagrass were identified in our study area: Halodule wrightii, Thalassia testudinum, Syringodium filiforme, Halophila engelmannii, and Halophila decipiens. A Bayesian model was developed to choose and parameterize a spatial process function that would describe the observed patterns of seagrass and macroalgae. The seagrasses were found in depths <2 m and in the higher manatee use strata, whereas macroalgae was found at moderate densities at all sampled depths and manatee use strata. The manatee spatial data showed a strong association with seagrass beds, a relationship that increased seagrass sampling efficiency. Our camera-based field sampling proved to be effective for assessing seagrass density and spatial coverage under turbid water conditions, and would be an effective monitoring tool to detect changes in seagrass beds. Copyright © 2013 Inter-Research.

Fourqurean J.W.,Florida International University | Manuel S.A.,Applied Ecology Section | Coates K.A.,Applied Ecology Section | Kenworthy W.J.,Center for Coastal Fisheries and Habitat Research | And 2 more authors.
Biogeosciences | Year: 2015

Striking spatial patterns in stable isotope ratios (isoscapes) and elemental ratios (stoichioscapes) of seagrass leaves and the water column nutrients indicate general P-limitation of both water column and benthic primary productivity on the Bermuda Platform, and they highlight the role of the Bermuda Islands as a source of N and P. We found consistent differences among the four seagrass species (Syringodium filiforme, Thalassia testudinum, Halodule sp. and Halophila decipiens) in the N, P, δ13C and δ15N of leaf tissues. The δ15N of seagrass leaves was especially variable, with values from -10.1 to 8.8 %, greatly expanding the reported range of values for all seagrass species globally. Spatial patterns from both the water column and the seagrass leaves indicated that P availability was higher near shore, and δ15N values suggest this was likely a result of human waste disposal. Spatially contiguous areas of extremely depleted seagrass 15N suggest unique N sources and cycling compared to other seagrass-dominated environments. Seagrass N : P values were not as far from the stoichiometric balance between N and P availability as in the water column, and there were no strong relationships between the water column N : P and the seagrass N : P. Such isoscapes and stoichioscapes provide valuable ecogeochemical tools to infer ecosystem processes as well as provide information that can inform food web and animal movement studies. © Author(s) 2015.

Watanabe W.O.,University of North Carolina at Wilmington | Alam M.S.,University of North Carolina at Wilmington | Ostrowski A.D.,University of North Carolina at Wilmington | Montgomery F.A.,University of North Carolina at Wilmington | And 3 more authors.
Aquaculture Reports | Year: 2016

In the first experiment the effects of rotifer enrichment and feeding frequency on larval performance of red porgy Pagrus pagrus were studied. Larvae (2 days post-hatching = 2 dph) were fed s-type rotifers (∼20 rotifers/mL) enriched with one of the four different treatment media: Rotifer Diet (microalgae Nannochloropsis oculata and Tetraselmis chuii), DHA Protein Selco, Algamac 3000 (Schizochytrium sp.) and Algamac + ARA (arachidonic acid). Larvae were fed daily at full ration or twice daily at half ration. Larval growth and survival (mean = 22.8%) were satisfactory through 16 dph under all treatments; however, resistance to hyposaline challenge (Survival Activity Index = SAI) was positively correlated (P < 0.01) with DHA concentration of rotifers, and SAI appeared highest in the Algamac + ARA treatment. In the second experiment the effects of Artemia enrichment on larval performance were compared from 18 dph through pre-metamorphosis (33 dph). Larvae were fed Artemia (0.5-3.0/mL) enriched with two different media Algamac 3000 and DC DHA Selco, or unenriched Artemia (control). Both media improved DHA levels in Artemia and growth and survival (36.7-54.6%) of larvae, while larvae fed unenriched Artemia showed poor growth and survival (5.2%). In the third experiment a University of North Carolina Wilmington microbound diet (MBD) and two commercial microdiets (Gemma Micro and Otohime) were evaluated. The MBD contained different protein sources (i.e., menhaden, squid and krill meal, soy protein concentrate) and attractants. Beginning 16 dph, live feeds and microdiets were co-fed to three treatment groups of larvae: (1) Gemma, (2) MBD, and (3) Otohime. Larval performance on the UNCW-MBD was comparable to the commercial microdiets, with no significant differences in larval survival, DHA, or total n-3 PUFA content through 32 dph. Results delineate more effective rearing protocols for larviculture of Atlantic red porgy juveniles. © 2016 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.

Able K.W.,Rutgers University | Sullivan M.C.,The Richard Stockton College of New Jersey | Hare J.A.,National Oceanic and Atmospheric Administration | Bath-Martin G.,National Oceanic and Atmospheric Administration | And 2 more authors.
Fishery Bulletin | Year: 2011

Summer flounder (Paralichthys dentatus) is one of the most economically and ecologically important estuarine-dependent species in the northeastern United States. The status of the population is currently a topic of controversy. Our goal was to assess the potential of using larval abundance at ingress as another fishery independent measure of spawning stock biomass or recruitment. Weekly long-term ichthyoplankton time series were analyzed from Little Egg Inlet, New Jersey (1989-2006) and Beaufort Inlet, North Carolina (1986-2004). Mean size-at-ingress and stage were similar between sites, whereas timing of ingress and abundance at ingress were not similar. Ingress primarily occurred during the fall at Little Egg Inlet and the winter at Beaufort Inlet. These findings agree with those from earlier studies in which at least two stocks (one north and one south of Cape Hatteras) were identified with different spawning periods. Larval abundance at Little Egg Inlet has increased since the late 1990s and most individuals now enter the estuary earlier during the season of ingress. Abundance at Little Egg Inlet was correlated with an increase in spawning stock biomass, presumably because spawning by larger, more abundant fish during the late 1990s and early 2000s provided increased larval supply, at least in some years. Larval abundance at ingress at Beaufort Inlet was not correlated with spawning stock biomass or with larval abundance at ingress at Little Egg Inlet, further supporting the hypothesis of at least two stocks. Larval abundance at Little Egg Inlet could be used as a fisheryindependent index of spawning stock size north of Cape Hatteras in future stock assessments. Larval occurrence at Beaufort Inlet may provide information on the abundance of the stock south of Cape Hatteras, but additional stock assessment work is required.

Jarvis J.C.,Virginia Institute of Marine Science | Jarvis J.C.,The Richard Stockton College of New Jersey | Moore K.A.,Virginia Institute of Marine Science | Kenworthy W.J.,Center for Coastal Fisheries and Habitat Research
Marine Ecology Progress Series | Year: 2012

Eelgrass Zostera marina L. populations located near the species southern limit in the western North Atlantic were assessed monthly from July 2007 through November 2008. We identified (1) dominant life history strategies and local environmental conditions in southern Z. marina populations, (2) quantified differences in reproductive phenology between populations and different local environmental conditions, and (3) compared reproductive strategies to established annual and perennial life history paradigms. Observed populations expressed both life history strategies with one Z. marina population completely losing aboveground biomass and reestablishing from seeds (annual model) while another population retained aboveground biomass throughout the year (perennial model). A third life history strategy, characterized here as a mixed-annual population, was also observed after some seedlings were found to reproduce both sexually and asexually during their first year of growth thereby not conforming to any currently established life history paradigm. Development of multiple life history strategies within this region may be in response to stressful summer water temperatures associated with the southern edge of the species' range. We suggest that neither annual nor perennial life history strategies always provide a superior mechanism for population persistence as perennial populations can be susceptible to multiple consecutive years of stress, and annual populations are unable to fully exploit available resources throughout much of the year. The mixed-annual strategy observed here represents another possible life history model which may provide the mechanism necessary for Z. marina populations to persist during times of environmental transition. © Inter-Research 2012.

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