Physical factors of differentiation in macrobenthic communities between atoll lagoons in the Central Tuamotu Archipelago (French Polynesia)

Abstract

Nine atolls were characterized in order to understand how physical factors control the species composition, diversity, and abundance of macrobenth~c (coral, mollusc, echinoderm, and algal) communities inside the lagoons. Only one region, the central part of Tuamotu Archipelago, French Polynesia, was considered, in order to minimise the variation due to regional factors between regions.The lagoons investigated showed a gradient of physical factors, providing various landscape configurations. The physical factors were surface area, abundance of pinnacles, degree of hydrodynamic aperture, and relative ~rnportance of passes In t h s degree of aperture. Macrobenthic communities were characterized by low diversity and strong dominance of a few mollusc or echmoderm species that generally occurred in lagoons without passes. Correlation analyses indicated that species richness increases with the surface area of the lagoon. Species richness of corals, echinoderms, and macroalgae was also higher in lagoons having numerous pinnacles. Canonical correspondence analyses revealed that the distribution and the relative abundance of coral, echinoderm, and macroalgae species were correlated to the relative importance of passes, whereas degree of aperture of the lagoon was also relevant for corals and molIuscs. The physical factors that control the processes of water exchange between ocean and lagoon, including passes, submerged reef flats, and spillways, influence the identity and the abundance of most macrobenthic species inside the lagoons.

Coral reef distribution, status and geomorphology?biodiversity relationship in Kuna Yala (San Blas) archipelago, Caribbean Panama

“…For instance, Adjeroud et al (2000b) have shown that the diversity of fish in Tuamotu atolls lagoons is well predicted by the size of the lagoon, but also by the type of geomorphological strata present in the atoll. Similar results were obtained for coral diversity in the same lagoons (Adjeroud et al 2000a).…”

“…However, in previous coral reef studies investigating diversity and spatial patterns (e.g., Galzin et al 1994;Fabricius and De'ath 2001;Bellwood and Hughes 2001;Beger et al 2003), remote sensing data have not been used and spatial information on reefs was consequently poorly estimated (e.g., surface area is crudely estimated by Bellwood and Hughes (2001)). These coral reef studies considered a limited number of positional (e.g., latitude, longitude, distance to center of diversity) or environmental predictors (e.g., surface areas, turbidity) while there is evidence that other local factors quantifiable from remote sensing images, such as presence of particular geomorphologic zones (e.g., pinnacles in lagoon), are also of importance (Adjeroud et al 2000a). Indeed, if very general rules can be highlighted when considering very large geographic gradients (Bellwood and Hughes 2001), the effects of positional or environmental factors on biodiversity cannot be neglected for regional or archipelago-scale analysis (Gaston 2000;Cornell and Karlson 2000;Adjeroud et al 2000a, Fabricius andDe'ath 2001).…”

Spatial patterns of benthic invertebrate assemblages within atoll lagoons: importance of habitat heterogeneity and considerations for marine protected area design in French Polynesia

“…This outcome is consistent with findings of recent studies that clearly demonstrated the importance of both local and regional factors in determining the diversity and structure of coral assemblages and the sensitivity of local coral richness to environmental variation across depth and habitat gradients (Cornell and Karlson 1996;Karlson and Cornell 1998;Rajasuriya et al 1998;Bellwood and Hughes 2001;Karlson et al 2004). The combination of the present study and Adjeroud et al's (2000) emphasizes the importance of nested spatial scales in structuring benthic invertebrate communities.…”

Dominant benthic mollusks in closed atolls, French Polynesia

“…Previous research has mentioned the lack of fauna biodiversity in closed lagoons compared to open ones (Adjeroud et al 2000b;Pante et al 2006). …”

“…Reka Reka is a very small atoll with a residual lagoon, 0.7 km 2 , with a depth of less than 1 meter, in which there are only some colonies of Porites and one mollusk, Cypraea moneta (Adjeroud 2000b). These two lagoons, for different reasons, are in the process of being filled in, such that they will eventually lose their lagoons; similar to four other small atolls in French Polynesia (Aki Aki, Nukutavake, Tepoto nord and Tikei).…”