Copepod egg production in the NW Mediterranean: effects of winter environmental conditions

Abstract

In the NW Mediterranean the highest abundance of phytoplankton is found during late winter, when temperatures are low. During summer, on the other hand, temperatures are high and phytoplankton abundance low, resulting in low copepod egg production rates (EPR). Despite the apparently better food conditions for copepod growth during winter, we lack information on copepod EPR during the cold season and on the possible effect temperature has on inhibiting this metabolic rate. To solve this uncertainty, a study was carried out to assess the effects exerted by the winter environmental conditions on the EPR of 3 representative planktonic copepod species of the NW Mediterranean (Centropages typicus, Clausocalanus lividus, Acartia clausi). The data were collected during 2 oceanographic cruises in March 1999 (Hivern-99) and January-February 2000 (Hivern-00) and the results compared to those of typical summer conditions. During the Hivern-99 cruise the phytoplankton abundance was very high (ranging from 1 to 1.5 µg > 5 µm chlorophyll a [chl a] l -1 ), indicating bloom conditions. During the Hivern-00, the phytoplankton bloom had not yet developed, evident by the chl a concentration of ~0.5 µg l -1. The recorded EPR during Hivern-99 were amongst the highest for the studied species, and the clearance rates deduced from them indicate a shorter (phytoplankton -copepods) food web during the winter phytoplankton bloom than for the rest of the year, when the planktonic trophic interactions take place through a longer microbial food web.KEY WORDS: Zooplankton · Copepod · Egg production · Centropages · Clausocalanus · Acartia · Mediterranean · Winter · Summer · Density front · Physical-biological coupling Resale or republication not permitted without written consent of the publisher

Plankton in the open Mediterranean Sea: a review

“…In winter, the autotrophic food was sufficient to support low zooplankton biomass, while heterotrophic food richer in proteins sustained the enhanced secondary production in spring, as indicated also by the increased ammonium excretion (Gaudy et al, 2003). A seasonal shift was also observed in the Catalan Sea, where copepods were strongly coupled with the autotrophic biomass during phytoplankton blooms (dominated by cells >5 µm) in March, and on heterotrophs in late spring and early summer, when autotroph abundance was lower (Calbet et al, 2002).…”

Inhibition of population growth in the copepods Acartia clausi and Calanus helgolandicus during diatom blooms

“…Reduced population growth in A. clausi was not due to a diminution in fecundity since egg production values in 1998 were elevated and comparable to peak EPR for this species in other Mediterranean coastal (Ianora & Buttino 1990) and offshore (Calbet et al 2002) in 1998) compared to 9827 females 100 m -3 in June 1998. Hence, TEP for the entire A. clausi population was 49 and 6 times lower during the diatom blooms in 1997 and 1998, respectively, compared to later in the year.…”

Annual cycle of early developmental stage survival and recruitment in the copepods Temora stylifera and Centropages typicus

“…Resale or republication not permitted without written consent of the publisher & Shibuno 1992), adult female size (Ban et al 2000, and quantity and quality of food (Kiørboe & Nielsen 1994, Saiz et al 1999, Kleppel & Hazzard 2000, Calbet et al 2002.…”