Production of tropical larvaceans in Kingston Harbour, Jamaica: Are we ignoring an important secondary producer?

Abstract

The larvacean community was observed during an 18 month period at the mouth of eutrophic Kingston Harbour, Jamaica. During this period, larvaecans averaged 3607 m-3 with a biomass of 2.2 mg ash-free dry weight m-3 (32.6 mg AFDW m-2) in a community dominated by Oikopleura longicauda. There were no relationships between larvacean biomass and any size fraction of chlorophyll, suggesting that other factors must normally regulate larvacean communities. The evidence indicates that this regulation is by predation. Annual production by larvaceans was 586 kJ m-2 year-1 (29.3 g AFDW m-2 year-1); production of houses could represent an added 300-600 kJ m-2 year-1. While copepod biomass was 10 times higher than that of the larvaceans during the same period, copepod growth rates were only one-third those of larvaceans. Thus, larvacean annual production is at least 30% that of the copepods, due to their rapid growth rates, and at least 50% that of the copepods when house production is considered. The contribution of larvaceans to plankton production has been underappreciated historically when only their biomass is considered.