The chronic effects of oil pollution on marine phytoplankton in a subtropical bay, China.

To evaluate the effects of crude oil water accommodated fraction (WAF) on marine phytoplankton community, natural phytoplankton collected seasonally from the Yueqing bay were exposed to eight groups of crude oil WAF for 15 days under laboratory conditions. Chlorophyll a and cell density were measured, and species of phytoplankton were identified every 24 h to reflect the change of phytoplankton community. The results showed that (1) High concentrations (≥ 2.28 mg l(-1)) of oil pollution would greatly restrain phytoplankton growth (p<0.001), decrease chlorophyll a content and cell density, whereas low concentrations (≤ 1.21 mg l(-1)) did not restrain its growth but rather promoted the phytoplankton growth. (2) The biodiversity, evenness, and species number of phytoplankton were all significantly influenced by crude oil WAF in all seasons (p<0.001). (3) The dominant species changes were different under different pollutant concentrations in different seasons. Different species had different tolerances to the oil pollution, thus leading to abnormal succession.