Showing papers by "Claire B. Paris published in 2006"

Scaling of Connectivity in Marine Populations

Abstract: Defining the scale of connectivity, or exchange, among marine populations and determining the factors driving this exchange are pivotal to our understanding of the population dynamics, genetic structure, and biogeography of many coastal species. Using a high-resolution biophysical model for the Caribbean region, we report that typical larval dispersal distances of ecologically relevant magnitudes are on the scale of only 10 to 100 kilometers for a variety of reef fish species. We also show the importance of the early onset of active larval movement mediating the dispersal potential. In addition to self-recruitment, larval import from outside the local area is required to sustain most populations, although these population subsidies are very limited in particular systems. The results reveal distinct regions of population isolation based on larval dispersal that also correspond to genetic and morphological clines observed across a range of marine organisms.

A bio-oceanographic filter to larval dispersal in a reef-building coral

Abstract: Gene flow was shown to be limited between western and eastern Caribbean populations of the reef-building coral, Acropora palmata. However, some mixing was detected among populations near Puerto Rico. Our genetic analyses categorize A. palmata samples from the east coast of the Dominican Republic with the western Caribbean population, suggesting a filter to gene flow east of the Dominican Republic. To test the hypothesis of a present day bio-oceanographic filter occurring between Puerto Rico and the Dominican Republic (i.e., in the Mona Passage), we used a Lagrangian stochastic model (LSM) of larval dispersal, coupling coral life history characteristics with physical forcing. The model operated at two spatial scales: Caribbean-wide and focusing on the Mona Passage area. Results from the Caribbean-wide study showed no significant virtual larval exchange between the two populations. The small-scale model indicated that virtual larvae do not readily traverse the Mona Passage during the corals' reproductive season. Larvae released from Mona Island, in the center of the passage, are retained in the lee within topographically steered eddies, which act, together with the larval competency period, as a de facto filter to dispersal. Combined, our findings reveal the location of a seasonal filter to gene flow and its mechanism.

Environmental forcing and larval fish assemblage dynamics in the Lima River estuary (northwest Portugal)

Abstract: This study investigated the potential control of selected abiotic parameters on an estuarine larval fish assemblage from the Lima River. Surveys were done fortnightly during spring tides, from April 2002 until April 2004, at 11 stations distributed along the estuary from the mouth to 7 km upstream. The surveys consisted of subsurface plankton tows of 5-min duration using a 1-m diameter, 500-μm mesh net and coupled with vertical profile measurements of temperature, salinity, dissolved oxygen, pH and turbidity. The Lima River estuary exhibited seasonal vertical stratification of salinity during the winter period, when salinity sharply increased with depth and a layer of fresh water was sometimes present at the surface. Temperature was always vertically stratified. Cooler water was typically found near the bottom of the water column, except during winter, when a thermal inversion occurred. A seasonal decrease in abundance and diversity of the larval assemblage was observed during winter, when fish larvae were almost absent from the plankton collections. Canonical correspondence analysis (CCA) results showed that the first axis represented a temporal gradient and the second axis represented a spatial gradient. Seasonal variations on temperature and precipitation were responsible for the temporal differences on the fish larval assemblages. This study reinforced the concept that interannual climate and hydrodynamic variations have a strong influence on estuarine ichthyoplankton and, consequently, on the recruitment of marine coastal fish populations.