Harmful Marine Phytoplankton Community in Shirazi Creek, Kenya

Abstract

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 Kenyan 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 of bivalve 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 LG 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 of fish 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.

Gut Content Analysis and Selective Feeding Behavior of the Asiatic Hard Clam Meretrix meretrix (Linnaeus, 1758) in Marudu Bay

“…The organic molecules casing found on the external layer of Coscinodiscus, known as the "perifrustular envelope," serve as a cue for high-quality food items for bivalves (Beninger & Decottignies, 2005). In contrast, the clam selectively rejected Chaetoceros, which has poor nutritional content and siliceous spines structure that can entangle at the gills of bivalves (Martínez-Fernández et al, 2006;Ochieng et al, 2015). Reduction in food quality triggers a higher level of sorting efficiencies in bivalves (Hawkins et al, 1996;Pouvreau et al, 2000).…”

The Incidence of Marine Toxins and the Associated Seafood Poisoning Episodes in the African Countries of the Indian Ocean and the Red Sea

“…Countries with monitoring programs of marine environments related to control of seafood poisoning are listed in Table 2. A few of these programs have noted the presence of MTs (Figure 14) and HAB species [dinoflagellates, cyanobacteria, diatoms], some of which [HAB species] were detected/confirmed by microscopic techniques and some confirmed by partial 16 S rRNA genes analysis [12,13,298,299,300,301,302,303,304,305,306,307,308,309,310,311,312,313,314,315,316,317,318,319,320,321,322,323].…”

“…; dinoflagellates: Alexandrium sp., Dinophysis sp., D. caudata, Gambierdiscus sp., G. toxicus, Gonyaulax sp., Gymnodinium sp., Gyrodinium sp., Ostreopsis sp., Peridinium sp., Prorocentrum sp., Ceratium sp., C. fusus, C. furca, Noctiluca sp., N. scintillans , Protoperidinium sp., Scrippsiella sp. and S. trochoidea [301,310]. Cyanobacteria were also reported: Lyngbya sp., Oscillatoria sp., Fischerella epiphytica , Anabaena sp., Nodularia spumigena , Umezakia natans , Aphanizomenon flos-aquae, Microcystis aeruginosa and Trichodesmium sp.…”