A model of larval dispersion coupling wind-driven currents and vertical larval behaviour:application to the recruitment of the annelid Owenia fusiformis in Banyuls Bay, France

Abstract

ABSTRACT. We present a mathematical model of larval dispersal into a coastal zone dominated by wlnd-driven currents: larvae are considered as active particles tracked by the 3-D (3-dimensional) velocities calculated by a physical model sophisticated enough to give a good representation of the 3-D structure of wind-driven currents. As a n application, we model the larval recruitment of the annelid Owenia fusiformis in Banyuls Bay, France, located at the southwest extremity of the Gulf of Lions. The currents are generated by the permanent offshore Liguro-Provencal circulation and by time-varying winds, the s\vunmlng behav~our of larvae is assumed to be only vertical, the spawning zones are in 2 adjacent bays and the pelagic phase lasts about 4 wk. Larvae are assumed to be successfully recruited if they settle after pelagic morphological changes on the substratum suitable to their benthic development. Larvae which do not belong to the successful recruitment either settle too young on the suitable substratum or go out of the suitable substratum. The model shows that the fate of the larvae tracked by the currents appears to b e determined early in the pelagic phase by being trapped in low current zones. Simulations allow the deduction of the advection losses for different winds the proportion of larvae reaching the adult habitat is 60% at maximum for downwelling conditions and 15 O/o at minimum for init~a l u p w e h n g conditions. Our results indicate too that under the most frequent wind cond~tions no mixing occurs between populations of the 2 adult habitat zones which are 1.6 km apart from each other and that no successful recruitment occurs from larvae coming from bays located at the north of the considered coastal zone. Only combinations of changing wind conditions could permit arrival of larvae from Paulilles Bay to Banyuls Bay. The interest of such individual-based models consists not only in increasIng our understanding of the link between spatial and temporal dynamics of meroplanktonic populations but also in allowing us to explore the potential effects of habitat alterat~on on those populations.

Stage-specific distribution of barnacle larvae in nearshore waters: potential for limited dispersal and high mortality rates

“…If the potential for limited larval dispersal and high mortality rates inferred from our data are a general feature of similar coastal regions, then populations of sedentary benthic invertebrates with planktonic larvae may be disconnected at small spatial scales, as suggested by recent observational (McQuaid & Phillips 2000, Porri et al 2006) and modeling studies (Verdier-Bonnet et al 1997). Future efforts to model the relationship between coastal oceanography and benthic population dynamics must shift from an emphasis on mesoscale processes to a better description of inner-shelf variability and its effect on dispersal and self-recruitment.…”

Limited wind-driven dispersal of intertidal mussel larvae: in situ evidence from the plankton and the spread of the invasive species Mytilus galloprovincialis in South Africa

“…The mathematical model of Verdier-Bonnet et al (1997) predicts that, under the most common wind conditions near Banyuls in France, populations of polychaets with larvae in the water for 4 wk would show little exchange between bays < 2 km apart. Todd et al (1998), working with allozymes, found that populations of a nudibranch with pelagic lecithotrophic larvae were closed on surprisingly small spatial scales.…”

Possible effects of downwelling on the recruitment of coral reef fishes to the Eilat (Red Sea) coral reefs

“…These currents are usually driven by wind, which is one of the three principal agents controlling the movement of larval fish and invertebrates on the continental shelf (Epifanio and Garvine 2001). Evidence indicates that these currents might affect the recruitment of invertebrates such as crabs (Blanton et al 1995;Wing et al 1995;Shanks 1998), clams (Weissberger and Grassle 2003;Ma 2005;Shanks and Brink 2005), sea urchins (Wing et al 1995), annelids (Verdier-Bonnet et al 1997), and others, although the association with the vertical current might be weak (e.g., Shanks 1998). However, only a few studies have explained the differences found in the recruitment intensity of fish as due to upwelling or downwelling flow (Reiss and McConaugha 1999;Miller and Shanks 2005), and none of these have referred to coral-reef fishes.…”