Effects of anthropogenic disturbances of tropical soft-bottom benthic communities

Abstract

The benthic ecosystem of the lagoon surrounding Tahiti, the most populated island of French Polynesia, was investigated to assess the impacts of terrestrial runoff on these benthlc cornmunities. Five lagoonal zones based on population densities around the coast of Tahti were identified, and within each zone a transect from the fringing reef to the barrier reef was sampled, a total of 18 stations.Only large macrofauna collected on a 2 mm sieve were considered in this study. Multivariate analysis uslng total biomass and environmental factors showed that the stations formed 3 main groups which were related to sediment characteristics, including percentage of silt, organic matter and phaeop~g-ment levels. The distribution of the major feeding groups was related to the amounts of terrestrial inputs and distance from the shore. The stations on the barrier reef and those in zones adjacent to low population areas were not impacted by these terrestrial inputs. Deposit-feeding communities of capitellid polychaetes were dominant in the channel parts of the lagoon, which acted as decanting ponds. Chaetopterid polychaetes played an important role in recycling sediments of terrigenous origin in the fringing ecosystem. The patterns of diversity, density and biomass of the benthos around the lagoon revealed that some areas were impacted by moderate terrigenous inputs. It appears that the intermediate disturbance hypothesis explains the functioning of the parts of the benthic lagoonal ecosystem which are subjected to human impact. The organic enrichment by terrestrial inputs contrasts with food limitation that appears to occur in the non-dsturbed areas. Despite high organic loads, the benthic communities present at the harbour station were not depauperate, as bioturbation by burrowing alpheids and callianassids prevented anoxic conditions from developing.

Interrelationships of bacteria, meiofauna and macrofauna in a Mediterranean sedimentary beach (Maremma Park, NW Italy)

“…This is further indicated by the correlation of the variable r 1 with the macrofaunal pattern in Mar 2, as shown by the BIO-ENV analysis. Consequently, organisms probably prefer the upper layers of the midlittoral zone, where conditions are not so severe (Brown and McLachlan 1990;Fruin 2000). Considering the meiofaunal horizontal distribution on the beach, in Mar 1 and 3 the meiobenthic community showed a similar structure in the swash (Station 2) and in the lower midlittoral station (Station 3), while in Mar 2 the swash was closer to Station 1.…”

Ecology and distribution of soft-sediment benthic communities off Viti Levu (Fiji)

“…Soft-bottom benthic communities have been used to investigate the effects of anthropogenic inputs and perturbations on coastal marine ecosystems (Pearson & Rosenberg 1978, Keough & Quinn 1991, Frouin 2000. Our study provides an overview of the community structure in lagoons around Viti Levu and will act as a baseline to help future monitoring and conservation programmes.…”

Fringing Reefs of Reunion Island and Eutrophication Effects - Part 1: Long-Term Monitoring of Two Shallow Coral Reef Communities

“…Their abundance at Site-P appeared then to be linked to the abundance of primary producers as the bulk of detritus derives mainly from algae (Lewis, 1977). Similarly, Frouin (2000) found a significant difference in ACR and MAS soft-bottom communities. Conand & De Ridder (1990) and Mangion et al (2004) explained the high density of sea cucumbers in the P-back reef by a high amount of organic matter but also by the reproductive strategy of one of the dominant species, Holothuria atra.…”