Seasonal variation in abundance and feeding rates of the first stages of copepods in a temperate sea

Abstract

An understanding of the role of copepod populations in marine ecosystems and carbon fluxes is limited by the scarcity of information on small copepods and developmental stages (nauplii and copepodites). Here, we present a study that includes the whole copepod population in the Cantabrian Sea, with special emphasis on copepodites and copepods <200 µm and nauplii. Total copepod abundance and feeding rates of phytoplankton by nauplii, copepods and copepodites belonging to the size fraction < 200 µm were measured during an annual cycle in 3 stations off Cud- illero (southern Bay of Biscay). Nauplii were the most abundant group in the metazooplankton, with densities ranging between 1 and 48 ind. l -1 . The highest abundances were found during late summer and autumn. Feeding rates on phytoplankton showed a significant increase with chlorophyll a con- centration in the water, and a saturation response at around 240 µg C l -1 . Specific ingestion rates ranged from 0.04 to 2.05 µg C µg -1 nauplii C d -1 and 0.04 to 3.38 µg C µg -1 copepod C d -1 . Nauplii and copepods < 200 µm, respectively, ingested 0.2 to 7.1% and 0.1 to 4.9% of total chlorophyll a in the water column daily.