Some aspects of the biogeography and ecology of intertidal and shallow subtidal marine gammaridean amphipods of Mauritius (Indian Ocean)

Appadoo, Chandani (1997) Some aspects of the biogeography and ecology of intertidal and shallow subtidal marine gammaridean amphipods of Mauritius (Indian Ocean). Masters thesis, Memorial University of Newfoundland.

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Abstract

Sixty-nine species of marine gammaridean amphipods were reported from 34 sites (486 samples with 34,441 specimens) of varying exposure in the intertidal/shallow-subtidal zones of Mauritius (19° 59' E-20°32' E; 57°18' S-57°47' S, Indian Ocean) in April-July, 1995. Two sites, Souillac, a wave exposed site on the south coast, and Trou aux Biches, a sheltered site on the north-west coast were sampled most intensively. -- Sand, coral rubble, debris, seagrass and algal substrates were sampled both qualitatively and quantitatively (10 cm x 10 cm quadrat). The occurrence and abundance of amphipods on algal substrates were studied in detail. -- Forty-one of the 69 species are new records for the island and 19 of these are undescribed. One hundred and thirty species are now known from Mauritius and of these 32% appear to be endemic. Many Mauritian amphipod species are widely distributed in the Indo-Pacific. About 50% of the amphipod species are shared with Madagascar (the closest large land mass). -- Amphipod species showed varying patterns of occurrence on sand, seagrass, coral rubble and algal substrates with some being specialists and others generalists. The frequency of occurrence of 35 amphipod species on 17 algal taxa showed that some species occurred on only a few, while others were more ubiquitous. Mean abundance of individuals per 10 cm x 10 cm quadrat was significantly different for 7 of the amphipod species on 12 algal taxa analysed at Souillac. At Souillac, only the mean number of individuals per quadrat for Hyale grandicornis was significantly different among algal morphological categories with the highest mean number occurring on foliose forms. Only mean numbers of individuals of Hyale grandicornis and Mallacoota subcarinata were significantly different among algal toughness categories. -- The amphipod assemblages on algal substrates were compared in terms of total abundance and species diversity. The amphipod community on Ulva lactuca at an exposed and sheltered site were not significantly different in total numbers; species richness, however, was higher at the exposed location. Cluster analysis showed that exposed sites have different amphipod assemblages than protected/moderately exposed sites.

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