Effects of oil pollution on protist communities in experimental ecosystems

Abstract

To assess the effects of crude oil and dispersant on marine planktonic protists, an outdoor mesocosm experiment was carried out over a period of nine days. In the mesocosm with oil plus dispersant, high concentration of total petroleum hydrocarbon(TPH) were soon found in the bottom layer. Total bacteria abundances increased for the first two days. The abundance of heterotrophic flagellates increased rapidly in association with the increase in bacterial cells. Microalgal cells (diatoms and dinoflagellates) decreased clearly within first two days. The planktonic protist ecosystems were affected less adversely in the mesocosms treated with crude oil alone than with dispersant. An indoor microcosm experiment was also carried out in order to investigate the effect of oil pollution on marine attached protists. Microbial assemblages including ciliates on acrylic plates dipped in 35 L-liter cubic container filled with WAF (Water Accommodated Fractions of crude oil) were monitored during 10 days and compared with the communities in the control. Significant differences of water temperature, salinity, dissolved oxygen, and pH were not shown between the control and the oil microcosm. Ciliate abundances typically increased in the oil. In the ciliates, sessilid group increased and sustained the community in the oil while euplotid group, especially Euplotes spp., was diminished. Conthurnia spp. and Pseudhydrocarbon(TPH) were soon found in the bottom layer. Total bacteria abundances increased for the first two days. The abundance of heterotrophic flagellates increased rapidly in association with the increase in bacterial cells. Microalgal cells (diatoms and dinoflagellates) decreased clearly within first two days. The planktonic protist ecosystems were affected less adversely in the mesocosms treated with crude oil alone than with dispersant. An indoor microcosm experiment was also carried out in order to investigate the effect of oil pollution on marine attached protists. Micr