Abstract
A one-year study (July 2003 – June 2004) to explore the spatial and temporal variability of potentially harmful dinoflagellates was carried out in the central coastal waters of Tanzania. During the course of the study a green dinoflagellate, Noctiluca scintillans, which has cosmopolitan distribution, was encountered for the first time in the coastal waters of Tanzania. It demonstrated a clear temporal distribution with high biomass (up to 30 cells/l) during the northern monsoon period and showed significant negative correlation with temperature and salinity. Noctiluca scintillans was possibly introduced by ballast waters or currents and became established for at least one season, but later disappeared due to the physical-chemical environment and/or competition or predation from other organisms in the water column. The need for a monitoring programme for potentially harmful micro-algae, and introduced alien species in Tanzanian coastal waters, is justified.
Highlights
The dinoflagellate Noctiluca scintillans (MacCartney) Ehrenb. is characterized by having large, up to 2,000 μm, bladder shaped vegetative cells associated with an oral pouch in which are located the tentacle and one emergent flagellum (Lucas, 1982)
Nutrient values along the Tanzanian coast are low as a result phytoplankton blooms, apart from those of the nitrogen fixing cyanobacterium Trichodesmium species, have not been documented
With the apparent increase in pollution and eutrophication in the coastal waters of Tanzania (Mohammed, 2002), it is likely that such blooms may occur in the future
Summary
The dinoflagellate Noctiluca scintillans (MacCartney) Ehrenb. is characterized by having large, up to 2,000 μm, bladder shaped vegetative cells associated with an oral pouch in which are located the tentacle and one emergent flagellum (Lucas, 1982). Vertical movements of Noctiluca in the water column are due to active ionic regulation of the specific gravity. But may form symbiotic association with a photosynthetic green flagellate, Pedinomonas noctilucae (Sweeney, 1976). When the endosymbiont is present, Noctiluca can apparently thrive photosynthetically without the need for phagotrophic food uptake. Noctiluca scintillans is known to have a cosmopolitan distribution and is found in all temperate, subtropical and tropical coastal waters (Elbrächter and Qi, 1998). In the Indian Ocean, blooms of Noctiluca scintillans have been reported from Indian waters Adnan (1989) provided a review of the green Noctiluca blooms in Jakarta Bay, Indonesia In the Indian Ocean, blooms of Noctiluca scintillans have been reported from Indian waters (e.g. Subrahmanian, 1985; Devassy, 1989), in Hong Kong waters (Ho and Hodgliss, 1992), far offshore from the equatorial Indian Ocean (Taylor 1976), and more recently in the Indian waters again (Eashwar et al, 2001; Dharani et al, 2004). Adnan (1989) provided a review of the green Noctiluca blooms in Jakarta Bay, Indonesia
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