Zonation patterns of benthic communities in an upwelling area from the western Medierranean (La Herradura, Alboran Sea)

Emma Cebrián,Enric Ballesteros

doi:10.3989/scimar.2004.68n169

Abstract

Species composition and distribution of marine benthic communities from La Herradura (Alboran Sea, western Mediterranean) are described to characterise its rocky and sedimentary bottoms bionomically. Rocky bottoms were studied by means of several underwater transects and soft bottoms with fixed stations along a bathymetric gradient. The study of the floristic and faunistic composition of the rocky benthic communities highlights depth as the main axis of variation. Factorial Correspondence Analysis segregates deep-water communities below 25 m depth (circalittoral communities) from shallower communities (axis I), and communities thriving between 5 and 25 m depth (lower infralittoral communities) from communities thriving close to the surface (shallow infralittoral communities) (axis II). The study of the sedimentary bottoms also suggests that depth, together with physical sedimentary properties, is the main axis of variation in species distribution. Floristic and faunistic records show the particular composition of La Herradura benthic communities, compared to Mediterranean and Atlantic ones. Mixing of Mediterranean and Atlantic waters, together with deep water upwelling episodes typical of this area, probably determine the peculiar composition of the benthic communities.

Highlights

The Alboran Sea is located at the westernmost part of the Mediterranean and has its own physical and biological traits (Gil, 1988)
Submerged vegetation patterns have been studied in several localities of the Alboran Sea (Giaccone, 1972; González, 1994), species composition of some circalittoral communities has been described (Templado et al, 1986; Templado et al, 1993; Maldonado, 1992, 1993), and the knowledge of the main invertebrates thriving in its waters is compiled in Ocaña et al (2000), there are no available data on macroalgae and macrofauna species composition and distribution of communities along depth gradients in shallow (0-50 m) waters, with the exception of two transects described in Cebrian et al (2000)
In the present study we describe the species composition and the zonation patterns of benthic communities thriving in the rocky and sedimentary bottoms of the village of La Herradura, whose coastal waters are regularly affected by deep water upwellings (Lanoix, 1974; Rodríguez, 1990; Templado et al, 1993), and we compare the structure of the studied communities and their spatial distribution with similar studies performed in other western

Summary

Introduction

The Alboran Sea is located at the westernmost part of the Mediterranean and has its own physical and biological traits (Gil, 1988). The combination of all these hydrological features together with the pronounced biogeographical differences between the Atlantic Ocean and the Mediterranean Sea (Conde, 1989; Pérès, 1985; González and Conde, 1993; Maldonado and Uriz, 1995; Cebrian et al 2000) should affect benthic communities and their zonation patterns. Submerged vegetation patterns have been studied in several localities of the Alboran Sea (Giaccone, 1972; González, 1994), species composition of some circalittoral communities has been described (Templado et al, 1986; Templado et al., 1993; Maldonado, 1992, 1993), and the knowledge of the main invertebrates thriving in its waters is compiled in Ocaña et al (2000), there are no available data on macroalgae and macrofauna species composition and distribution of communities along depth gradients in shallow (0-50 m) waters, with the exception of two transects described in Cebrian et al (2000)

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Conclusion