Changes in the abundance and distribution of sav along Florida’s springs coast: a comparison based on aerial photography acquired in 1992 and 1999

Do more oyster larvae settle in rough neighborhoods?: The influence of small-scale topography on oyster recruitment

M. Lisa Kellogg* and Rita B. J. Peachey. Dauphin Island Sea Lab, 101 Bienville Blvd., Dauphin Island, AL 36528, USA, and Department of Marine Sciences, LSCB 25, Univ. of South Alabama, Mobile, AL 36688, USA.

A series of field surveys, laboratory experiments and field experiments were used to determine if differences between natural oyster reefs and shell plantings in Mobile Bay, Alabama affect the recruitment rates of oyster larvae. Analysis of field surveys indicated that natural oyster reefs and shell plantings differ in their topographic complexity, shell orientation, and shell size distributions. ADV measurements taken over the two types of reefs demonstrate that natural reef topographies produce more turbulence and create thicker boundary layers than shell planting topographies. Differences in reef topography and local hydrodynamic regime have the potential to affect the delivery rates of particles such as oyster larvae to the surface of a reef from the overlying water column. To determine if more of the larvae passing over a reef are retained within the matrix of natural reefs, single-pass experiments were conducted using eyed pediveliger oyster larvae released upstream of the two reef types in a racetrack flume. Analysis of substratum samples indicated that more larvae were found within the matrix of natural oyster reef treatments than within shell planting treatments. Field studies of recruitment rates demonstrated that significantly more oyster larvae recruit to natural reef topography treatments. Thus, our studies indicate that the small-scale topography (1-30 cm) of oyster reefs can affect the rate of oyster recruitment. We believe that the increased rates of recruitment to natural reef topographies are due, at least in part, to a local hydrodynamic regime that favors the deposition of particles such as oyster larvae.

Influence of secondary metabolites from Caribbean sponges on bacterial surface colonization

Sarah R. Kelly* and Joseph R. Pawlik. Biological Sciences and Center for Marine Science, University of North Carolina at Wilmington, Wilmington, NC, USA.

Organic extracts from 8 Caribbean sponges were assayed for inhibitory effects on surface colonization of twenty-four marine bacterial isolates, four known marine invertebrate pathogens, and a common fouling bacterium. Each extract was tested for inhibition of bacterial attachment, growth and swarming. The 24 bacterial strains were isolated from the surfaces of the sponges, nearby substrata, or the surrounding seawater. Extracts from sponge species inhibited bacterial attachment. Sponge extracts had a minimal effect on growth, with only 5 sponges affecting a total of 6 strains. Twelve strains were inhibited from swarming by 4 sponge extracts. Overall the chemical effects of bacterial colonization by sponges may target attachment and be complemented by swarming and growth inhibition. This investigation presents evidence that non-toxic metabolites may influence bacterial epibiosis on the surfaces of marine sponges.


Ecological consequences of El-Niño Southern Oscillation to coral reef Foraminifera

F. Kelmo^1,2* and M. Attrill.^{1 1}Benthic Ecology Research Group, Plymouth Environmental Research Centre, Department of Biological Sciences, University of Plymouth, United Kingdom; ²Brazilian Research Council—Conselho Nacional de Desenvolvimento Cientifico e Tecnologico, CNPq—Brazil.

Reef-dwelling Foraminifera hold substantial potential as indicators of reef vitality. Although this group has been heavily investigated to date, most of the environmental studies have focused on rapid-assessment of anthropogenic stress. Such short-term investigations may be highly suitable for diagnosing acute impacts on very well-known reef systems (where they comprise limited sample sizes and a minimal number of species). However, their use has not been validated for assessing the long-term consequences of natural disturbances. We have undertaken a long-term investigation in order to verify any response of these organisms to a major, defined environmental disturbance, the 1997-1998 El-Nino Southern Oscillation (ENSO). In this paper we present the first quantitative results of a six years study which investigates variations in shallow water foraminiferan community composition from 1995 to 2000. Sediment samples were collected with a 50g core, annually, at four reef sites from Northern Bahia (Brazil) and all foraminiferans were extracted and identified. A total of 285 species were recorded from the area, including 26 species new to science. The densities of live-forams were significantly different (ANOVA, F=56.762, P<0.001) between pre- and post-ENSO years, and multivariate analysis suggested dramatic changes in community composition. BIOENV analysis identified mean temperature variance and UVR incidence as the main factors best explaining changes in the community, stress factors associated with the ENSO. Whilst ENSO appeared to have an overall detrimental impact on the foraminiferan community (in terms of total diversity and abundance), the disturbance has resulted in influx of several new species previously unrecorded in the survey.


Anti-predation strategies in marine worms: to hide or be distasteful, that is the question

C. E. Kicklighter* and M. E. Hay. Georgia Institute of Technology, Atlanta, GA, USA; e-mail [e-mail], [e-mail].

Chemical defenses are important predator deterrents for many organisms inhabiting predator-rich enviornments. While chemical, structural, and nutritional defenses against consumers are well studied for sessile species such as seaweeds and sponges, how a chemical defense may be used with other anti-predation strategies, such as behavioral avoidance and refuge use, has not been adequately addressed. To investigate this question, marine worms were examined for palatability to sympatric predators. Chemical traits, behavior, and refuge use were examined for the role they play in determining palatability and susceptibility to consumers. Our findings suggest that species exposed to predators are unpalatable and chemically defended, while species that utilize a spatial or structural refuge are more palatable. Moreover, for some refuging species, body parts that remain in a strong tube are palatable and lack deterrents while those in a weak tube are unpalatable. Regardless of tube strength, more exposed or more nutritionally rich body parts are more unpalatable and possess chemical or structural deterrents. Behavior is also an important anti-predation strategy. When contrasting palatable with unpalatable species that live in tubes, palatable species retract more quickly and completely into a tube and do so at a greater distance from a physical disturbance. These patterns suggest that (1) deterrent strategies vary with refuge use, refuge strength, and are allocated to body parts that are more nutritious or more likely to encounter predation and (2) there is variability in the use of avoidance versus deterrence strategies within a taxonomic group.