Feeding and production of zooplankton in the Catalan Sea (NW Mediterranean)

Zooplankton are key components of the structure and functioning of marine planktonic food webs. They are the main link of planktonic primary production towards top pelagic consumer levels (fish), and play a relevant role on the nutrient recycling in the water column and on the export of particulate matter out of the photic zone. In this paper, we review the present knowledge on the feeding and production of zooplankton in the Catalan Sea (NW Mediterranean), with special emphasis on copepods. Feeding of zooplankton in the Catalan Sea appears typically food limited, with average daily rations on a yearly basis in the order of 48% body C d−1. Heterotrophic prey constitute a relevant fraction of their diet, as an alternative to the scarce phytoplankton in the area. From a structural point of view, the trophic impact and control of their prey populations are low on standing stocks but, at certain times, zooplankton can exert a meaningful effect on their prey production. Regarding zooplankton production, the available estimates of growth rates in the area are based on the egg production rate of copepods. Egg production rates appear to be limited, especially in summer. Tentative estimates of copepod production in the area are in the order of 20-40 mg C m−2 d−1. In conclusion, this review confirms that the oligotrophic character of the NW Mediterranean constrains the feeding activity and production of zooplankton.