Distribution patterns of macrofaunal polychaete assemblages in a polluted semi-enclosed bay: Cienfuegos, Caribbean Sea

Spatial and temporal distribution patterns of polychaete assemblages were described in six subtidal sampling stations within Cienfuegos Bay, a Cuban semi-enclosed bay in the Caribbean Sea for 4 months (February and September 2006, February and May 2007). This bay is strongly polluted due to the accumulation of organic enrichment and heavy metals in sediments. Macrofaunal assemblages were impoverished and their distribution highly patchy across stations and months. Molluscs, arthropods and echinoderms were scarce, but small-size opportunistic polychaete species such as Polydora sp. and Streblospio benedicti were predominant. The synergistic effects of low hydrodynamics and hypoxia derived from organic enrichment probably explain the distribution patterns of macrofauna. Heavy metal contamination appears to have minor effects on fauna; low bioavailability of metals and tolerance of fauna can explain this hypothesis. Seasonal changes of macrofauna can be related to water stagnation in the wet (summer) period and concomitant increase of hypoxia. Clear symptoms of eutrophication related to organic enrichment and a depleted macrofauna suggest a threatened ecosystem where management actions have to be applied urgently.