Biodiversity and spatio-temporal variability of copepods community in Dakhla Bay (southern Moroccan coast)

Abstract

This is the first study on zooplankton in Dakhla Bay that focused on the assessment of the spatial and temporal variations in copepod communities and the relationship with the environmental variables during three oceanographic surveys conducted in winters 2012, 2013 and 2016. The zooplankton community was diverse and dominated by copepods representing more than 80% of total zooplankton. Thirty copepod species were identified with Acartia clausi, Euterpina acutifrons and Oithona nana the most common and abundant species. Ten species were ranked as dominant species and their abundance accounted for more than 85% of the total abundance of copepods. The highest copepods abundance was recorded in February 2012 and February 2013 whose averages were 1258 ± 2897 and 4164 ± 5604 ind m−3, respectively, while the lowest abundances were recorded in 2016 (average 293 ± 380 ind m−3). The diversity of the copepod community of Dakhla Bay varied between 0.96 and 2.80 bits individual−1 and the species richness showed a positive gradient from the upstream to the downstream area following the inverse gradient of salinity, particularly in 2013. CCA results revealed a strong relationship between copepod species and studied environmental parameters (temperature, salinity and chlorophyll-a) and justified the apparition of some species such as Acartia tonsa, Calocalanus pavo and Nanocalanus minor in 2016 where highest temperatures were recorded.