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Fig. 1: Relative abundances ofpotential pollution bioindicatorsspecies, presented as percentagesof total sponge abundance (numberof individuals), at stations locatedat different distances from twomain pollution sources in thenorth-western Cuba (Havana Bayand Almendares River). MarielBay is not significantly polluted.in non-polluted reef areas, which makes it inconsistent as apotential bio-indicator.López-Victoria and Zea (2004) showed that the abundanceof Cliona caribbaea is not related to pollution in San AndrésArchipelago, Colombia. Indeed, this species did not occur atsites close to the organically polluted Quibú River and thenearby sewage outfall, but only in more distant sites (Marcosand Alcolado, unpublished observations).Other sponge species have been associated with factorsother than pollution, namely sedimentation and wave stress(Table 1). Particularly, Aplysina cauliformis is apparentlytolerant to strong waves, as can be deduced from its dominancein coral reef sites exposed to more frequent tropical storms(keys Juan García and Cantiles, southwestern Cuba). This canbe due to its branching morphology, flexibility and elasticity,similar to what was suggested by Wulff (1995) for Aplysinafulva, also branching and with rather similar consistency.The suggested usefulness of the presence or abundanceof some sponges as environmental indicators has beenbased much on expert observation and on inferencesrelated to distance from known pollution sources, waveand wind exposure, visual evidence of varying intensity ofsedimentation, etc. For that reason, to validate these resultsand make further progress, more evidence is necessary,obtained both from well designed experiments and frommultivariate analysis in which factors are directly measuredon appropriate temporal and spatial scales. Additionally,more sites in the Wider Caribbean, suffering various degreesof pollution, tropical storm frequency, exposure to waves anddominant winds, etc., are worth being researched to test thegenerality of the mentioned findings. It would be of particularinterest to determine if Clathria venosa feeds on bacteria withemphasis on enteric taxa, as does Clathria prolifera (Ellis andSolander, 1786) according to Claus et al. (1967).Community indicesIn agreement with other authors (Muricy 1989, Carballo etal. 1996, among others), Alcolado and Herrera (1987) foundthat species richness and Shannon´s heterogeneity index H’were lower at more polluted sites (Fig. 2). Pielou’s equitabilityindex J’ was also lower in the more polluted sites close to themouth of Almendares River (Fig. 2).Given that a condition of significant stress can be inferredonly when the dominance of some of the mentioned indicatorspecies (Table 1) is coupled with low values of speciesrichness or species heterogeneity (Alcolado et al. 1994),these univariate indices have to be taken into account as animportant complement for environmental monitoring.The summing up of the numerical percentages ofindividuals belonging to species that are tolerant to the samekind of stressor (e.g., pollution, sedimentation, turbulence,etc.) could be useful as another potential community indexfor monitoring purposes, as done by Alcolado (1981) withgorgonians to infer relative turbulence intensity, and byHerrera-Moreno (1991), also with gorgonians, to infer relativeorganic pollution level.The usefulness and conceptual validity of diversity indiceshas been controversial (Hurlbert 1971, Peet 1974). However(without disregarding potential pitfalls), the herein exploreddiversity indices can be used and tested pragmatically andheuristically for bio-monitoring purposes in the context ofenvironmental management, not specifically for advancing