Water quality affects the structure of copepod assemblages along the Sfax southern coast (Tunisia, southern Mediterranean Sea)

Abstract

The Sfax southern coast (Gulf of Gabes, Mediterranean Sea) has been under increased anthropogenic pressure for many years. In the present study we investigated the effects of this anthropisation on the spatial distribution of copepod assemblages in relation to the physicochemical features of seawater at 20 stations sampled on 19 March 2013. Copepods represented 73% of total zooplankton abundance. Small planktonic copepods (<1.45mm), including pollution-tolerant species (e.g. Oithona nana, Paracalanus parvus, Harpacticus littoralis and Tisbe battagliai), proliferated exclusively in stations of ~0.5-m depth characterised by high coastal anthropogenic inputs. The largest copepod species were dominated by Calanus helgolandicus (1.45–2.5mm) in the offshore zone in depths of ~3m. Substantial numbers of Oithona plumifera (7.5%) were found at depths between 0.5 and 3m. Copepod diversity was significantly higher in the southern zone, which is less affected by sewage, than in the northern zone, which was subjected to higher pressure (Shannon–Wiener index H′=1.5–2.5 and ≤1.5 bits individual–1). A shift in the planktonic copepod community between the two zones was linked to deterioration of water quality, with higher phosphorus levels, turbidity and chemical oxygen demand (COD) in the northern zone.

Spatial variation of summer microphytoplankton and zooplankton communities related to environmental parameters in the coastal area of Djerba Island (Tunisia, Eastern Mediterranean)

“…The zooplankton abundance was primarily characterized by the predominance of copepods in all the stations in the Western Area of the Djerba coasts. The dominance of copepods has already been reported in several studies in the Gulf of Gabes region: on the southern coast of Sfax (66 -82% of the total zooplankton; Ben Salem et al, 2015;Drira et al, 2018a;Drira et al, 2018b); on the northern coast of Sfax (61-82%; Rekik et al, 2011Rekik et al, , 2013Drira et al, 2018a); in Ghannouch and Zarrat (46 -83%; Baccar, 2014;Drira et al, 2018a); in offshore waters of the Gulf of Gabes (83%; Drira et al, 2014;Ben Ltaief et al, 2015); along the southern coast of Kerkennah Islands in summer (98%; Rekik et al, 2018a), in Kneiss Islands in summer (30-96%; Rekik et al, 2018b) and in Boughrara lagoon (62%-92%; Makhlouf-Belkahia et al, 2020). Among copepods, Calanoids were highly dominant (up to 79% of copepod abundance), which is very similar to what was observed by Drira et al (2018a) on the coast at Ghannouch (51% of total copepod abundance) and on the Sfax coast (43% of total copepod abundance).The high dominance of Paracalanus parvus in the Djerba copepod community in summer also corresponds to what was reported in Kneiss islands, Tunisia (Rekik et al, 2018b), in Kerkennah islands, Tunisia (Rekik et al, 2018a) and in Boughrara lagoon, Tunisia (Makhlouf-Belkahia et al, 2020).…”

Predator density modifies mosquito regulation in increasingly complex environments

“…Given limited tolerances to pollution in wholly aquatic invertebrates (e.g. copepods), this suggests an important predatory role of notonectids in suppressesing mosquito populations within patchy aquatic habitats at the landscape scale. Our results enhance understanding of environmental factors which alter the predatory effects of these important natural enemies of mosquitoes, and indicate interspecific differences within taxonomic groups.…”

Copepods as Indicators of Different Water Masses during the Northeast Monsoon Prevailing Period in the Northeast Taiwan

“…In the marine environment, zooplankter is exposed to and sensitive to physical, chemical, and biological factors [ 1 , 2 , 3 , 4 ]. Their population dynamics were shown to respond closely to seasonal temperature variations [ 5 , 6 , 7 ].…”