Growth rates of dinoflagellates along the Karachi coast assessed by the size fractionation method

The in situ growth rates of dinoflagellates along the Karachi coast off Pakistan was studied by the size fractionated method during winter (February 2006) and summer (May 2007). The growth rate per day ranged from -2.87 to 2.3 d–1(20 species) in winter and from 1.20 to 1.95 d–1 (13 species) in summer. Growth rates (μmax d–1) of the dominant species were as follows: Prorocentrum gracile, Prorocentrum minimum, Prorocentrum arcuatum (1.0-1.10), Protoperidinium steinii (0.92), Gonyaulax spinifera (0.69), Dinophysis acuminata (2.3), Dinophysis caudata (0.92), Ceratium lineatum, Prorocentrum micans (1.95), Gyrodinium sp. (1.88), Ceratium furca (1.70), and Alexandrium ostenfeldii (1.34). The declining growth rates were observed for Pyrophacus stein (-1.10), Scrippsiella trochoidea (-1.61 to -0.82), Prorocentrum donghaiense (-1.94) and Karenia mikimotoi (-2.48). Our results suggest that a higher temperature induce an increase in dinoflagellate growth rates.