Plankton biodiversity in a landscape of shallow water bodies (Mediterranean coast, Spain)

A large spatial heterogeneity was detected in La Safor, a coastal area with different kinds of small and shallow water bodies. The area exhibits a sharp gradient in eutrophication (0.004–20 mgP l−1; 0.6–457 μg Chl a l−1) and varied water body features (morphology: size, depth; hydrology; vegetation, etc.). These factors result in a high diversity of aquatic habitats within the area. One hundred and twenty eight species of microalgae were identified in the 32 sampling stations studied (in the wet and dry periods). The phytoplankton richness varied between 1 and 21 species, the Shannon-Wiener index range was 0–3 bits, the index of floral originality (IFO) range was 0.1 – 0.6. A total number of 126 species of zooplankton were identified. The zooplankton specific richness ranged from 4 to 26 species, the diversity index and IFO were 0.9–3.7 and 0.1–0.6, respectively. A PCA allowed the ordination of different water body types as a function of total phosphorus, flux of water, water transparency, presence of macrophytes and oxygen. Plankton richness, diversity index, equitability and IFO showed weak relationships to the trophic gradient. The global planktonic biodiversity was higher than expected for such an anthropogenically affected ecosystem. The different, above mentioned conditions contributed to the limitation of biodiversity loss often observed in eutrophic conditions.