Changes in Copepod Community Between Two Contrasting Samplings in a Highly Polluted Mediterranean Coastal Zone (Sfax Bay, Tunisia)

Changes of taxonomic composition, morphology (total length) and reproductive mode of copepod assemblages between the cold and warm periods were studied in the Southern coast of Sfax, in relation with environmental factors and pollution degree (heavy metal concentration). Salinity, temperature and heavy metal concentration seem to be the most important factors influencing the total length during both sampling periods. A total of 23 different copepod species were identified during the survey period. The copepod abundance was higher in cold (74%; 9.78 ± 10.04 × 103 ind m-3) than in warm (67%; 7.11 ± 8.81 × 103 ind m-3) periods. This result could be attributed to an increase of temperature and salinity in August, which favors the development of smaller copepod species. During the cold season, larger adult broadcaster of calanoids species (total length between 0.98 and 1.22 mm) such as Acartia (Acartia) danae (Giesbrecht) (Tl = 1.22 mm), Paracartia grani (Sars) (Tl = 1.12 mm) and Paracartia latisetosa (Krichagin) (Tl = 1.06 mm) were associated to low temperature and salinity. During the warm period, smaller egg-carrying species of harpacticoids (total length between 0.18 and 0.3 mm) such as Harpacticus littoralis (Sars), Tisbe furcata (Baird) and Tigriopus sp. (Norman) were associated with high temperature and heavy metal pollution. H. littoralis displayed a very high abundance of ovigerous females (Nfo = 12.8 × 103 ind m-3, representing 87.2% of total number of females) with high number of eggs per sac (E = 26 ± 2 egg sac-1).