High spatial heterogeneity of two planktonic cnidarian species related to the variability of a shelf-slope front at short time scales

Elena Guerrero,Ana Sabatés,Covadonga Orejas,Josep Maria Gili,Anna Marrodán

doi:10.3989/scimar.04452.03a

Elena Guerrero, Ana Sabatés + Show 3 more

Open Access

https://doi.org/10.3989/scimar.04452.03a

Copy DOI

Abstract

We investigated the variability in the mesoscale distribution of the siphonophore Muggiaea atlantica and the hydromedusa Aglaura hemistoma in relation to the rapid spatial oscillations of the shelf-slope front off the Catalan coast (NW Mediterranean). Three extensive surveys were carried out in spring at ten-day intervals. High variability in the position of the front resulted from the advection of low-salinity waters originating in the Gulf of Lions, mainly from the Rhône River runoff. High spatial variability in the distribution of the two species was closely related to the shifting positions of the front. Both species occurred on its inshore side in much higher abundances than on its offshore side, where they were scarce or absent. The front acts as a barrier limiting offshore displacement of these two cnidarians. Statistical analyses showed that bottom depth and salinity, as independent variables, were indicators of the signature and position of the front, explaining most of the variance in the distribution and abundance of the two species.

Highlights

Shelf-slope fronts separating low-salinity coastal waters from high-salinity open-sea waters are common along continental shelves (Wang et al 1988, Houghton1997)
Gelatinous zooplankton are abundant in pelagic communities, playing an important role in food-web dynamics due to their great trophic impacts and rapid population growth, which sometimes results in seasonal blooms (Graham et al 2001, Pagès et al 2001)
Our goal was to investigate how the variability of hydrodynamic structures determines the mesoscale distributions of planktonic cnidarians

Summary

Introduction

Shelf-slope fronts separating low-salinity coastal waters from high-salinity open-sea waters are common along continental shelves (Wang et al 1988, Houghton1997). To the accumulation and active growth of microalgae and zooplankters (Sabatés et al 1989, Fernández et al 1993, Mann and Lazier 2006). These phenomena determine the distributions and abundance of many groups of zooplankton Gelatinous zooplankton are abundant in pelagic communities, playing an important role in food-web dynamics due to their great trophic impacts and rapid population growth, which sometimes results in seasonal blooms (Graham et al 2001, Pagès et al 2001). Explicit evidence for this bio-physical coupling is scarce (e.g. Pagès and Gili 1992, Graham et al 2001, Pavez et al 2010)

Objectives

Methods

Results

Discussion

Conclusion