The spatial distribution of environmental factors and the response of net-phytoplankton in the Laizhou bay during wet-season in 2017

To better understand the distribution of environmental factors and the response of phytoplankton in the Laizhou bay, a comprehensive survey contained 31 stations about surfer sea temperature (SSS), surfer sea salinity (SST), nitrite (NO₂-N), nitrate (NO₃-N), ammonium (NH₄-N), dissolved inorganic nitrogen (DIN), phosphate (PO₄-P), silicate (SiO₃-Si) and net-phytoplankton abundance and species diversity (H′) was conducted in August 2017. In the present study, obvious spatial distribution differences of environmental factors were observed with high SST, nutrients while low SSS located in southwest coast of the Laizhou Bay, especially at Xiaoqing River estuary. The terrestrial inputs such as the Xiaoqing River and its vicinity were the main factors influencing the distributions of SSS and nutrients. The low NH₄-N value at the Xiaoqing River estuary was mainly attributed to the NH₄-N reduction in the Xiaoqing River. High phytoplankton abundance and low H′, showing obvious spatial distribution differences, were mainly observed at the Xiaoqing River estuary. Four different phytoplankton groups were observed according to the community structures difference indicating an obvious response of phytoplankton to environmental factor variations. Phytoplankton abundance showed significant negative correlation with SSS and Si/N (p<0.05) while positive with NO₃-N, NH₄-N and DIN. Significant negative correlations were observed between H′ and SST, DIN (p<0.05). The phytoplankton community structure were mostly influenced by the environmental combination of NO₃-N、NH₄-N、DISi、Si/N and single factor of DISi.