Nine sandy beaches along the Ecuadorian coast were sampled for epi-, hyper- and endobenthos on four occasions (August 1999, November 1999, February 2000 and May 2000). Spatial and temporal patterns within and in between these three benthic groups were investigated, as well as abiotic factors possibly structuring the communities. Within the endo- and hyperbenthos, five geographically distinct communities could be observed, which were different for both groups. Endobenthic communities were primarily distinguished based on differences in abiotic factors such as gravel content, chlorophyll a, salinity and beach morphology. Within the defined communities, temporal patterns could subsequently be distinguished. Hyperbenthic communities on the other hand, mainly seemed to be structured by seasonal trends. Abiotic factors however, were not as a decisive factor as for the endobenthos. Within the epibenthos, there could only be made a clear distinction between anthropogenically and non-anthropogenically influenced beaches, based on total densities and species richness. A comparison of the endo-, hyper- and epibenthos, shows that the endobenthos is characterised by the highest total densities (on average 745 ind./m² per sample), whereas the hyperbenthos showed the highest species richness (on average 15 higher taxonomic groups or 43 morphospecies per sample). The epibenthos was characterised by the lowest total densities (on average 0.04 ind./m² per sample) and an average species richness equal to that of the endobenthos (5 species per sample). The extremely low total densities of the epibenthos require some caution when interpreting the data. Dominant taxa varied considerably per beach and per sampling period. Combining the three benthic groups into “macrobenthos” gave a total 111 observed taxa, with an average of 28 taxa per beach. The only pattern found within the macrobenthos was the grouping of two beaches that are under anthropogenic influences of tourism and waste water dumping, thereby concluding that human disturbance cannot be ignored when investigating the benthos of Ecuadorian sandy beaches. When studying Ecuadorian surf zone systems more in detail, for example within the framework of the effect of climate changes on the benthos, one should bear in mind that (1) different benthic groups show different spatial and temporal patterns, (2) temporal patterns are not the same between beaches and (3) the structuring function of environmental variables and the impact of human disturbance can differ considerably between the benthic subgroups. |
