Suspended shellfish culture impacts on the benthic layer: a case study in Brazilian subtropical waters

Abstract

This study aimed to assess benthic impacts of suspended shellfish cultures in two marine farms located in South Bay, Florianópolis (SC, Brazil). The goal was to detect changes in the benthic layer and evaluate the influence of local conditions, such as hydrodynamics and geomorphology, on the degree of impact at each site. The method included analysis of three groups of oceanographic descriptors: hydrodynamic; morpho-sedimentological (bathymetry, grain size and organic content), and ecological (foraminiferal fauna). Data sets were analyzed using geostatistical and multivariate techniques. Ecological descriptors seemed to be more effective under different environmental conditions than sedimentological variables. Those that best identified culture-related biodeposits, were: dominance of Ammonia tepida; test size; and living: total population ratio. Only slight differences were observed within and outside the culture structures. However, a greater alteration was observed at the site with weaker hydrodynamics and located in shallower depths. The conclusion is that biodeposition at studied still causes little alteration in the local benthic environment. However, local factors such as hydrodynamics and geomorphology were shown to be important in minimizing these impacts. These are criteria that should be considered in site selection programs for the development of this productive activity.