Phytoplankton composition in the coastal Magnetic Island lagoon, Western Pacific Ocean (Australia)

1 - Coastal lagoons have traditionally been considered as transitional systems between continental and marine domains. The phytoplankton plays a key role in these aquatic environments, forming the base of the food web and having a substantial function in nutrient dynamics and in the carbon biogeochemical cycle.2 - Due to their short life cycle, planktonic algae respond quickly to environmental changes and they are thus a valuable indicator of water quality. It is essential to investigate the development of phytoplankton populations to understand the biological functioning and to detect changes in aquatic systems.3 - Phytoplankton studies in the Australian estuaries and lagoons are relatively scarce. This study has provided a broad perspective and preliminary information on taxonomic structure of phytoplankton guilds for the Magnetic Island Lagoon (Queensland, Australia). This work may provide valuable information of interest to later ecological studies.4 - In the whole sampling a total of 143 taxa were identified. In terms of species richness, diatoms (Bacillariophyceae, Coscinodiscophyceae, Fragilariophyceae) and dinoflagellates (Dinophyceae) were the most important groups. In taxonomic terms, diatoms were the major contributor to the phytoplankton composition (~ 70%) whereas Dinophyceae were moderately abundant (~23%). Diatoms are a very important component in estuarine and shallow coastal wetlands and they are increasingly being utilized as indicators of environmental change.