Harmful Marine Phytoplankton Community in Shirazi Creek, Kenya

摘要

Globally, coastal creek waters represent important aquaculture zones for shellfish culture, commercially important fin-fishes larvae and crustaceans due to their richness in phytoplankton community. The harmful phytoplankton community in K_0nyan coastal waters causes mortalities to aquatic organisms both in the wild and culture areas. Therefore, as a result of the high economic values attached to these resources and taking into consideration that Shirazi creek waters has been used for the culture ofbivalve oysters as early as 1990s; its investigation for the presence of harmful phytoplankton community became necessary. Surface water samples were monthly collected from September, 2013 to August, 2014 at five fixed different stations. The harmful marine phytoplankton species were microscopically identified and counted. Sixteen potentially harmful marine phytoplankton species, with mean cell concentration of abundance ranged from 10±1-210±11 cells L~(-1), were found in the creek. Ten out of the total identified species were those capable of producing potent toxins to humans. Three were the main cause for the indiscriminate killing offish and invertebrates during blooms as a result of oxygen depletion. The remaining three species were harmful to fish and invertebrates through damaging or clogging of gills. The present study registered increase in the number of these potentially harmful phytoplankton species compared to the previous investigations. However, the study highlights on possible threat from future bloom occurrences as a result of increased eutrophication owing to climate change.