Medusa scintillans Macartney 1810
Noctiluca miliaris
Morphological Characteristics :
Very large in size. Strongly buoyant. Balloon-shaped cell with a striped tentacle. The cytoplasm is mostly colourless, except for the presence of minute carotenoid globules around the periphery of the cell. Sometimes, the organism is bioluminescent and phagocytic.
Size of Specimen :
200-2000 mm (radius)
Distribution :
Cosmopolitan. The main red tide causative organism in the South China Sea. Very obvious seasonal patterns : the first peak at early March to May, the second peak at late October to November of each year. Has caused more than 60 red tides in Hong Kong and Dapeng Bay since the late eighties.
Major Limiting Factors :
Red tide positively correlated with inorganic phosphates, silicates and inorganic nitrogen; negatively correlated with chlorophyll-a and dissolved oxygen. Favoured by temperature (18-25°C). Sometimes also favoured by the availability of other phytoplanktons as feed.
Toxicity :
Non-toxic although may cause seawater pink or reddish brown in colour. Sometimes caused fishkill by oxygenation depletion. The ammonia content of the vacuole irritate fish and the skin of human beings.
