Egg production of the copepod Acartia tonsa in Florida Bay: role of fatty acids in the nutritional composition of the food environment

Abstract

The relationship between copepod egg production (EP) and nutritional constituents of the seston was investigated in a variety of environments in Florida Bay. Seston samples were col- lected for analyses of protein, carbohydrate, lipid, and specific fatty acid concentrations, and egg pro- duction rates of the planktonic calanoid copepod Acartia tonsa were measured during 'non-bloom' conditions in January and May of 1998 near Rankin Key, during a diatom-dominated bloom in January of 1999 near Flamingo, and during a flagellate-dominated bloom in October of 1999 near Rabbit Key. Fatty acid concentrations were also measured in copepod adults and eggs off Rabbit Key. Egg production rates from Rankin Key were low (2.7 to 2.8 eggs female -1 d -1 ) compared with rates from the 'bloom' sites (25.0 to 56.3 eggs female -1 d -1 ). Concentrations of nutritional constituents in the seston were low off both Rankin Key and Flamingo, but significantly higher off Rabbit Key. Adult copepods contained high proportions of omega-3 fatty acids (18:3ω -3, 20:5ω -3, and 22:6ω -3), but of these only 18:3ω -3 was present in the eggs. Although EP varied independently of the concentrations of proteins, carbohydrates, lipids, and most fatty acids, it varied directly with the concentration of the 18:3ω -3 fatty acid.