Climatic Oscillations and Copepod Interannual Variation Off Central Algeria (SW Mediterranean Sea)

The biodiversity of copepod populations was studied over a 4‐year period (2014–2017) in Bou Ismail and Algiers Bays through qualitative and quantitative monitoring. The results support three objectives: (i) the seasonality of copepod abundance subject to temperature, salinity, and food availability (Chl a concentrations) regulations; (ii) the trophodynamics of copepods as prey for gelatinous zooplankton and jellyfish; and (iii) the impact of climate on species abundance patterns. A total of 53 copepod species are recorded and encompass 3 orders (calanoida, cyclopoida and harpacticoida), 20 families, and 31 genera. These are either perennial with Atlantic characters (11 species), neritic (11 species) or bathymetric migrants (14 species). The rare species (Fi < 25%) are qualitatively important (22 species). The abundances are subject to geographical and temporal variability. The functioning of the ecosystems is regulated by characteristic populations, so‐called abundant species Temora stylifera , Oithona plumifera , Nannocalanus minor , Neocalanus gracilis , Subeucalanus elongatus, S . monachus , Centropages typicus , C . hamatus , Microcalanus pygmaeus , Mecynocera clausi , Agestus flaccus, A . limbatus , Oncaea mediterranea , Xanthocalanus mixtus , Triconia minuta ). By using a Principal Components Analysis, their increase is characterized by a seasonality that is strongly correlated with hydrological (temperature, salinity and chlorophyll a ), climatic (NAO index) variations, and is also involved in prey–predator relationships where 4 seasonal trends are described. Multimodal Growth Populations (MGP; Oithona plumifera and Temora stylifera ) have affinities for all seasons. Trimodal Growth Populations (TGP; N. minor and O. mediterranea ) have winter, spring, and summer affinities. Bimodal Growth Populations (BGP; in spring and summer for M. clausi and E. elongatus elongatus and in winter and spring for S. monachus ) . Unimodal Growth Populations (UGP; in spring for M. pygmaeus , N . gracilis , A. flaccus, A. limbatus , C. hamatus , C . typicus , X. mixtus and T. minuta ). The qualitative distributions of richness species and their occurrence did not show any seasonality.