Chemical bioactivity of sponges along an environmental gradient in a Mediterranean cave

Xavier Turon,Ruth Martí,Maria J Uriz

doi:10.3989/scimar.2009.73n2387

Abstract

SuMMarY: The bioactivity of the most abundant sponges from three communities in a Mediterranean cave was assessed by Microtox ® assay in two seasons, spring (June) and autumn (november). We quantified bioactivity as a proxy for the investment in production of biologically active substances, and we related sponge bioactivity to growth form, growth rates, and physical contacts of each species with other species. We established a threshold for classifying a species as bioactive based on a comparison between the results of the Microtox ® and the sea urchin embryo toxicity bioassay. a total of 30 spe cies were included in the study, of which 50% were bioactive in some community or season. Significant ecological (between communities) and seasonal variation in mean bioactivity was found. When sponge bioactivity was related to sponge growth shape, it was found that the encrusting species tended to be more toxic than the non-encrusting ones. There was a negative relationship between bioactivity and sponge growth, suggesting a trade-off in energy allocation to defence and to other biological functions. Furthermore, a negative correlation was found between bioactivity and positive associations with other species. These results highlight the important role of chemically-mediated interactions in cave communities.

Highlights

Studies of the chemical ecology of marine organisms have consistently shown that sponges are among the main producers of biologically active substances (Amade et al, 1987; Uriz et al, 1992; Newbold et al, 1999)
SUMMARY: The bioactivity of the most abundant sponges from three communities in a Mediterranean cave was assessed by Microtox® assay in two seasons, spring (June) and autumn (November)
When sponge bioactivity was related to sponge growth shape, it was found that the encrusting species tended to be more toxic than the non-encrusting ones

Summary

Introduction

Studies of the chemical ecology of marine organisms have consistently shown that sponges are among the main producers of biologically active substances (Amade et al, 1987; Uriz et al, 1992; Newbold et al, 1999). Rarely, an allelopathic function has been documented (Porter and Targett, 1988; Turon et al, 1996a; Thacker et al, 1998; Engel and Pawlik, 2000). This has been analysed in more depth in sponges in which exudation of active metabolites has been proven (Thompson, 1985; Walker et al, 1985). The multifunctional nature of some secondary metabolites of sponges has been reported (Becerro et al, 1997a; Thacker et al, 1998; Newbold et al, 1999), which gives an idea of the multiple roles that they may play in nature by mediating relationships among marine organisms

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Conclusion