Influence of some enviromental factors on the structure and distribution of the rocky shore macrobenthic communities in the Bay of Gibraltar: preliminary results.

Abstract

The Bay of Gibraltar contains a high biological diversity which is conditioned by a suite of both biotic and abiotic factors of natural origin.However, the Bay is also subjected toa variety of anthropic impacts which have a considerable effect on the marine biota. The rocky littoral is particular!y useful in environmental monitoring programmes as it is easily accessible and amenable to sampling, and the sessile nature ofthe majority of the species make long-term monitoring relatively simple.

In this study we compare data obtained for a number of environmental variables using a range of statistical methods to the community data obtained at six sites inside the Bay and two sites immediately outside, one to the East and another to the West. The results of these preliminary analyses indicate that, within the range of environmental parameters measured, small and intermediate-scale natural variables such as microtopography and exposure to wave action are important. However, within the Bay, the effects of urban and agricultura) effluents and associated variables assume a greater role in the structuring of these intertidal communities.

La Bahía de Gibraltar contiene una alta riqueza biológica que se ve condicionada por factores bióticos y abióticos de origen natural. Sin embargo, la Bahía también sufre una gran variedad de actividades antrópicas que afectan a la biota marina de manera considerable. El litoral rocoso es relativamente accesible y sencillo de muestrear, y es un ecosistema muy útil para estudiar el posible efecto de estas alteraciones, pues las especies son generalmente sésiles y la composición y estructura de sus comunidades reflejan su historia.