Anthropogenic Inputs Affect Phytoplankton Communities in a Subtropical Estuary

Abstract

In the past few decades, with the rapid economic development of China and Vietnam, the marine ecological environment of Beibu Gulf is facing increasing pressure. To understand the impact of anthropogenic inputs on marine ecology, high-performance liquid chromatography (HPLC) was used to study phytoplankton in this paper. We examined the influence of anthropogenic inputs on phytoplankton biomass and community structure in a subtropical estuary. Anthropogenic inputs had significantly increased the nutrient concentration in the estuary between 2010 and 2015. We observed that phosphorus limitation has been greatly relieved in 2015. However, the biomass of dominant phytoplankton was lower in 2015 than in 2010, possibly due to the expansion of oyster farming in the estuary. The coverage of oyster rafts was estimated to be 26.3 km2. The presence of dense oysters may significantly reduce the phytoplankton biomass. The proportion of Diatoms decreased while some nano- and pico-phytoplankton (like Cryptophytes and Prasinophytes) increased, which indicated that oysters changed not only the biomass but also the size of phytoplankton communities. This study improved our understanding of anthropogenic inputs on phytoplankton communities in subtropical estuary.