The Diet and Feeding Habits of the Southern Stingray, Dasyatis americana, in Tropical Shallow Marine Habitats

The diet and feeding habits of the southern stingray, Dasyatis americana, were investigated through aerial surveys, land-based observations, and quantitative analysis of stomach contents. The field research was conducted in the Exuma Cays Land and Sea Park, central Bahamas. Systematic aerial surveys and the land-based observations were made to determine population density and feeding periodicity in terms of time or tidal phase. In August, 1989, systematic surveys were flown over two cays in the Park; a 12 km2 area around Waderick Wells Cay and a 21km2 area around Shroud Cay. Both survey areas were flown three times over different times of the day. Over the large area covered by the aerial surveys the population varied over time of day. A significantly higher density occurred in the morning for both grids and was lowest in the afternoon for both grids suggesting that the stingrays prefer to feed early in the day in the summer. The peak density was 2.07 stingrays per km2 for the Waderick Wells survey area and 1.87 per km2 for the Shroud survey area. A total of 117 hours of land-based observations were made over 4 months; with 28 to 31 hours of observations in April and May 1990 and January and July, 1991. The land-based observations indicated that the stingrays were actively feeding throughout the day, but showed some increase in feeding activity during the high tidal phase. The habitat utilization was recorded during the land-based observations and showed that the stingrays spent most of their time feeding in the soft sediment habitats, thus taking advantage of the soft sediment algal turf and sandy shoal habitats that dominate the shallow marine environments within the Park. Eighteen stingrays were collected in January, 1991 for stomach content analysis. Decapod crustaceans were the most important prey category, but the large number of prey types found in all of the stomachs indicates that the southern stingray is a generalist feeder. There were no empty stomachs and 77% of the stomachs had more than 20 prey items. Stomach fullness measures did not indicate any feeding periodicity. The southern stingray is a generalist feeder taking advantage of a broad range of prey types and opportunistic in its feeding habits, showing no strong feeding periodicity

Outplanting Technique, Host Genotype, and Site Affect the Initial Success of Outplanted Acropora cervicornis

Acropora cervicornis is the most widely used coral species for reef restoration in the greater Caribbean. However, outplanting methodologies (e.g., colony density, size, host genotype, and attachment technique) vary greatly, and to date have not been evaluated for optimality across multiple sites. Two experiments were completed during this study, the first evaluated the effects of attachment technique, colony size, and genotype by outplanting 405 A. cervicornis colonies, from ten genotypes, four size classes, and three attachment techniques (epoxy, nail and cable tie, or puck) across three sites. Colony survival, health condition, tissue productivity, and growth were assessed across one year for this experiment. The second experiment assessed the effect of colony density by outplanting colonies in plots of one, four, or 25 corals per 4 m2 across four separate sites. Plot survival and condition were evaluated across two years for this experiment in order to better capture the effect of increasing cover. Colonies attached with a nail and cable tie resulted in the highest survival regardless of colony size. Small corals had the lowest survival, but the greatest productivity. The majority of colony loss was attributed to missing colonies and was highest for pucks and small epoxied colonies. Disease and predation were observed at all sites, but did not affect all genotypes, however due to the overall low prevalence of either condition there were no significant differences found in any comparison. Low density plots had significantly higher survival and significantly lower prevalence of disease, predation, and missing colonies than high density plots. These results indicate that to increase initial outplant success, colonies of many genotypes should be outplanted to multiple sites using a nail and cable tie, in low densities, and with colonies over 15 cm total linear extension

Spatial heterogeneity of soil nutrients and plant species in herb-dominated communities of contrasting land use

Recent interest in spatial pattern in terrestrial ecosystems has come from an awareness of theintimate relationship between spatial heterogeneity of soil resources and maintenance of plant species diversity. Soil and vegetation can vary spatially inresponse to several state factors of the system. In this study, we examined fine-scale spatial variability of soil nutrients and vascular plant species in contrasting herb-dominated communities (a pasture and an oldfield) to determine degree of spatial dependenceamong soil variables and plant community characteristics within these communities by sampling at 1-m intervals. Each site was divided into 25 1-m 2 plots. Mineral soil was sampled (2-cm diameter, 5-cm depth) from each of four 0.25-m2 quarters and combined into a single composite sample per plot. Soil organic matter was measured as loss-on-ignition. Extractable NH4 and NO3 were determined before and after laboratory incubation to determine potential net N mineralization and nitrification. Cations were analyzed using inductively coupled plasma emission spectrometry. Vegetation was assessed using estimated percent cover. Most soiland plant variables exhibited sharp contrasts betweenpasture and old-field sites, with the old field having significantly higher net N mineralization/nitrification, pH, Ca, Mg, Al, plant cover, and species diversity, richness, and evenness. Multiple regressions revealedthat all plant variables (species diversity, richness,evenness, and cover) were significantly related to soil characteristics (available nitrogen, organic matter,moisture, pH, Ca, and Mg) in the pasture; in the old field only cover was significantly related to soil characteristics (organic matter and moisture). Both sites contrasted sharply with respect to spatial pattern of soil variables, with the old field exhibiting a higher degree of spatial dependence. These results demonstrate that land-use practices can exert profound influence on spatial heterogeneity of both soil properties and vegetation in herb-dominated communities

Benthic Habitat Characterization for the South Florida Ocean Measurement Facility (SFOMF)

This report summarizes the distribution and relative abundance of two stony coral species (Acropora cervicornis and Acropora palmata) currently listed as threatened under the US Endangered Species Act (ESA) (Federal Register/Vol. 71, No. 129/Thursday, July 6, 2006 / Rules and Regulations, http://www.gpo.gov/fdsys/pkg/FR-2006-07-06/pdf/06-6017.pdf) and seven additional stony coral species which have been petitioned for listing as endangered or threatened under the ESA (Agaricia lamarcki, Dendrogyra cylindrus, Dichocoenia stokesii, Montastraea annularis, Montastraea faveolata, Montastraea franksi, and Mycetophyllia ferox) (Federal Register/Vol. 75, No. 27/Wednesday, February 10, 2010/Proposed Rules, http://www.nmfs.noaa.gov/pr/pdfs/fr/fr75-6616.pdf). This report also summarizes the abundance and distribution of small recreational vessel anchors observed within the study area for this survey effort. This effort was guided by the NOAA Fisheries Service’s recommended survey protocol (http://sero.nmfs.noaa.gov/pr/pdf/RecommendedSurveyProtocolforAcropora.pdf). This protocol was designed for surveying the distribution and abundance of Acropora spp. utilizing a 2-tiered survey approach. The protocol recommends data collection at 1 sampling site per every 10,000 m² within the project area. The first tier is a rapid assessment of the site to locate any occurrences of Acropora spp. The second tier is a more comprehensive effort designed to provide greater detail on colony abundance, size, and condition. If five or more Acropora colonies are identified during the tier 1 effort, a tier 2 effort is conducted. The seven candidate species were also included in the tier 1 sampling effort. No tier 2 effort was conducted for the seven candidate species. The number of small recreational vessel anchors seen during the tier 1 effort was also included. The project area included eight coral reef habitats found in depths less than 30m (Walker et al. 2008). These habitats included, from nearshore to offshore: colonized pavement-shallow, ridge shallow, inner linear reef, middle linear reef, colonized pavement-deep, outer linear reef, spur and groove, and aggregated patch reefs. Within these habitats in the project area, 376 sites were sampled (tier 1 sites). No Acropora palmata colonies were identified during this effort. Acropora cervicorniswas identified within 45 of the 376 tier 1 sites. A majority of these sites were within the nearshore habitats (colonized pavement-shallow, ridge-shallow, and inner linear reef) in depths less than 10m. Of these 45 sites, 29 had more than five colonies identified and were included in the tier 2 effort. All seven candidate species were identified at the tier 1 sites within the project area during the effort: Dichocoenia stokesii (344 sites), Montastraea faveolata (291 sites), Agaricia lamarcki (155 sites), Montastraea annularis (85 sites); Montastraea franksi (74 sites), Mycetophyllia ferox (24 sites), and Dendrogyra cylindrus (4 sites). D. stokesii was abundant in all habitats with more than five colonies identified in 228 sites. The middle reef supported the highest abundance of M. faveolata. More than five colonies of M. faveolatawere identified in 188 sites, and 11 sites had more than 50 colonies identified. A. lamarkicolonies were identified at nearly all of the colonized pavement-deep, outer reef, spur and groove, and aggregated patch reef; no colonies were identified in the nearshore colonized pavement-shallow and ridge-shallow habitats. Fifty sites had more than five colonies identified, and 29 sites had more than 10 colonies identified. Fourteen sites supported more than five colonies of M. annularis, and four sites in the middle linear reef habitat had more than 10 colonies identified. M. franksi colonies were identified in all habitats except the ridge shallow habitat; more than five colonies of M. franksi were identified in 15 sites, and the middle linear reef supported the highest abundance of colonies. More than five colonies of D. cylindricus and M. feroxwere not identified in any of the 376 tier one sites during the survey. Anchors were counted at 149 of the 376 tier 1 sites. Anchors were observed in all eight habitats. The maximum number of anchors seen at one site was eight, and 65 sites had two or more anchors

Determining the Extent and Characterizing Coral Reef Habitats of the Northern Latitudes of the Florida Reef Tract (Martin County)

Climate change has recently been implicated in poleward shifts of many tropical species including corals; thus attention focused on higher-latitude coral communities is warranted to investigate possible range expansions and ecosystem shifts due to global warming. As the northern extension of the Florida Reef Tract (FRT), the third-largest barrier reef ecosystem in the world, southeast Florida (25–27° N latitude) is a prime region to study such effects. Most of the shallow-water FRT benthic habitats have been mapped, however minimal data and limited knowledge exist about the coral reef communities of its northernmost reaches off Martin County. First benthic habitat mapping was conducted using newly acquired high resolution LIDAR bathymetry and aerial photography where possible to map the spatial extent of coral reef habitats. Quantitative data were collected to characterize benthic cover and stony coral demographics and a comprehensive accuracy assessment was performed. The data were then analyzed in a habitat biogeography context to determine if a new coral reef ecosystem region designation was warranted. Of the 374 km2 seafloor mapped, 95.2% was Sand, 4.1% was Coral Reef and Colonized Pavement, and 0.7% was Other Delineations. Map accuracy assessment yielded an overall accuracy of 94.9% once adjusted for known map marginal proportions. Cluster analysis of cross-shelf habitat type and widths indicated that the benthic habitats were different than those further south and warranted designation of a new coral reef ecosystem region. Unlike the FRT further south, coral communities were dominated by cold-water tolerant species and LIDAR morphology indicated no evidence of historic reef growth during warmer climates. Present-day hydrographic conditions may be inhibiting poleward expansion of coral communities along Florida. This study provides new information on the benthic community composition of the northern FRT, serving as a baseline for future community shift and range expansion investigations

Spatial heterogeneity of soil nutrients and plant species in herb-dominated communities of contrasting land use

Recent interest in spatial pattern in terrestrial ecosystems has come from an awareness of theintimate relationship between spatial heterogeneity of soil resources and maintenance of plant species diversity. Soil and vegetation can vary spatially inresponse to several state factors of the system. In this study, we examined fine-scale spatial variability of soil nutrients and vascular plant species in contrasting herb-dominated communities (a pasture and an oldfield) to determine degree of spatial dependenceamong soil variables and plant community characteristics within these communities by sampling at 1-m intervals. Each site was divided into 25 1-m 2 plots. Mineral soil was sampled (2-cm diameter, 5-cm depth) from each of four 0.25-m2 quarters and combined into a single composite sample per plot. Soil organic matter was measured as loss-on-ignition. Extractable NH4 and NO3 were determined before and after laboratory incubation to determine potential net N mineralization and nitrification. Cations were analyzed using inductively coupled plasma emission spectrometry. Vegetation was assessed using estimated percent cover. Most soiland plant variables exhibited sharp contrasts betweenpasture and old-field sites, with the old field having significantly higher net N mineralization/nitrification, pH, Ca, Mg, Al, plant cover, and species diversity, richness, and evenness. Multiple regressions revealedthat all plant variables (species diversity, richness,evenness, and cover) were significantly related to soil characteristics (available nitrogen, organic matter,moisture, pH, Ca, and Mg) in the pasture; in the old field only cover was significantly related to soil characteristics (organic matter and moisture). Both sites contrasted sharply with respect to spatial pattern of soil variables, with the old field exhibiting a higher degree of spatial dependence. These results demonstrate that land-use practices can exert profound influence on spatial heterogeneity of both soil properties and vegetation in herb-dominated communities

Thermal Stress-Related Spatiotemporal Variations in High-Latitude Coral Reef Benthic Communities

High-latitude coral reef communities have been postulated as the first areas to undergo reorganisation under climate change. Tropicalisation has been identified in some high-latitude communities and is predicted in others, but it is unclear how the resident benthic taxa are affected. We conducted a long-term (2007–2016) assessment of changes to benthic community cover in relation to thermal stress duration on the Southeast Florida Reef Tract (SEFRT). Thermal stress events, both hot and cold, had acute (thermal stress duration affected benthic cover that year) and chronic (thermal stress duration affected benthic cover the following year) impacts on benthic cover. Chronic heat stress was associated with declines in cover of the reef-building coral families Acroporidae, Montastraeidae, Meandrinidae, Mussidae and Siderastreidae, which coupled with the absence of cold stress and rising annual temperatures boosted macroalgae cover. Cover of smaller, weedy coral families, Poritidae, Agariciidae and Astrocoeniidae, was either unaffected or positively related to heat stress duration and rising mean temperature. Thermal stress was related to spatiotemporal variations in benthic cover on the SEFRT, likely enhanced by local stressors, such as elevated nutrients and sedimentation. Coral and octocoral cover declined within four of six sub-regions, sponge cover increased in half of the sub-regions, and macroalgae cover increased in four sub-regions during the study. Under current conditions, increased macroalgae and weedy coral cover are anticipated to inhibit reef recovery