Appearance of plankton and its correlation with water quality in the stabilization ponds at a sea‐based dredged sludge disposal site

Abstract

Field observations of water and organisms were performed in the stabilization ponds at a solid disposal site between 1983 and 1987 to plan measures against wastewater pollution at Sites II and III in the North Section of the Osaka North Port Sea‐Based Solid Waste Disposal Site. The number of phytoplankton cells varied 10³ to 10⁵ (cells)mL^‐1 and phytoplankton grew rapidly in spring and autumn. Principal dominant species were Skeletonema eostatum, Chlorella sp. and Chlamydomonas spp. Zooplankton ranged 10 to 10⁵ individuals (10L)^‐1 and were more numerous in the spring to summer. Brachionus plicatilis was dominant. COD_Mn of the stabilization ponds had a high correlation coefficient with p‐COD_Mn namely, phytoplankton cells and showed a high value during the growth period of phytoplankton in spring and autumn. These observation results showed that suppression or elimination of phytoplankton would be suitable to lower COD_Mn of effluent at disposal sites.