Trophic Relationships of Macrofauna within a Jamaican Seagrass Meadow and the Role of the Echinoid Lytechinus Variegatus (Lamarck)
Abstract:Macrobenthic invertebrates and fish fauna were sampled in a seagrass meadow of Thalassia testudinum König in Kingston Harbour, Jamaica. Gastropods were the dominant epiphyte grazers while the echinoid Lytechinus variegatus (Lamarck) was the major consumer of seagrass blades. Crustaceans were the most diverse group of detritivores though nemerteans, sipunculids and ophiuroids were numerically dominant. Bivalves were the dominant group of suspension feeders. Omnivorous species included nereid polychaetes and a variety of decapod crustaceans of which the xanthid crab Panopeus occidentalis (Saussure) was the most abundant. Drilling gastropods were the dominant carnivores. Only one fish Sparisoma radians (Cuvier and Valenciennes) was herbivorous, feeding exclusively on fresh Thalassia blades. Fourteen species were classified as omnivorous consuming fresh and/or detrital blades or algae. Crustaceans were the main food source for both omnivorous and carnivorous fish with caridean shrimps and crabs occurring in the diet of 87% of the species. Gut content analysis of L. variegatus showed they consumed both fresh and detrital Thalassia blades. In feeding experiments on fresh Thalassia adult urchins (45–52 mm test diameter) consumed 155 mg dry wt˙urchin–1˙day–1. There was no seasonal variation in feeding rates. Absorption efficiencies for organic matter ranged from 64–71% for urchins consuming a mixture of fresh and detrital blades and egesting a mixture of faecal chunks and pellets. The L. variegatus population has an important double role in trophodynamics; not only are the echinoids major grazers on seagrass but their faeces are a potential food source for detritivores.
Document Type: Research Article
Publication date: 1995-05-01
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