Distribution, abundance and ecology of the sponge Spheciospongia vagabunda (Phylum: Porifera, Class: Demospongiae) in a shallow lagoon of Mauritius.

Abstract

The distribution, abundance and physico-chemical parameters affecting the sponge Spheciospongia vagabunda were studied in a shallow lagoon (Albion) of Mauritius.  Visual censuses were conducted along the 2 Km lagoon and GPS coordinates around sponge assemblages (patches) were noted.  Sponge abundance and ecological parameters were assessed by random throws of quadrats and physico-chemical parameters, including water depth; salinity, pH, and turbidity were noted.   A distribution map of Spheciospongia vagabunda was constructed on Google Earth.  Two distinctive sponge patches with the largest patch averaging 15350 m² were identified.  Spheciospongia vagabunda in Albion were mostly anchored in the sand which is an unlikely substratum for Poriferans.  Some sponges were also observed next to the seagrass Syringodium filiforme.  Statistical analysis (t-test) showed that there was a significant difference among sponge size between both sponge assemblages (t = 3.01; p < 0.05).  One-way ANOVA analysis indicated that physico-chemical parameters of surrounding water did not influence the sponge abundance within the lagoon.  Spheciospongia vagabunda were mostly distributed in shallow regions (3.3 sponge/m² at a depth of 1.18 m).  This study adds to the lack of knowledge on Mauritian sponges and also acts as a baseline study for further monitoring of these benthic animals in the Albion lagoon.