Phytoplankton and Copepoda were investigated in the industrialized Gabès coast (Mediterranean Sea, Tunisia) to understand consequences of the Eutrophication Grade on the community composition. In the past 40 years, intensive agrochemical activities have developed in Gabès, discharging wastewater along the coast. In parallel, Gabès City has experienced a rapid demographic expansion (population: 131,000) that further increased sewage discharged into the sea. The present study was carried out in the Gulf of Gabès in March 2014. The abiotic analysis of seawater showed high concentrations of nutrients and eutrophication in all the studied fifteen stations. A growing eutrophic gradient was revealed from Zarrat to Gannouche. During this study, 42 phytoplankton taxa and 24 Copepoda taxa were identified. Bacillariophyta were the most abundant group, ranging from 67.7% to 89.2% of total phytoplankton specimens. Chaetoceros costatus, Euglena acusformis, and Thalassiosira sp. showed a positive correlation with Eutrophication Index (profited of nutrient availability). Therefore, the Shannon–Weaver diversity index of phytoplankton and Copepoda showed negative correlations with Eutrophication Index. The relatively high H′ values for phytoplankton suggest that the eutrophicated waters of Gulf of Gabès are not a hostile environment for them. Among Copepoda, Oithona similis, and Euterpina acutifrons seem to be insensible species to eutrophication.

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Spatial and temporal variations of reproduction variables of the two cyclopoid copepods Oithona nana Giesbrecht, 1893 and Oithona similis Claus, 1866 were evaluated monthly from September 2007 to August 2008 in four ponds at different salinities in the solar saltern of Sfax, Tunisia, under hypersaline conditions. Along the salinity gradient the abundance of O. nana and O. similis declined from 14,900 ± 15,200 ind. m-3 (A1) to 6,800 ± 7,200 (C31) and from 13,800 ± 17,100 ind. m-3 (A1) to 3,700 ± 5,800 (C31), respectively. The findings showed that the abundance of these Oithona species, particularly the ovigerous females, was positively correlated with the abundance of Diatomeae, and negatively correlated with salinity. The egg production rate (EPR), the egg diameter, the clutch size, as well as the cephalothorax length of mature females, were all negatively correlated with salinity and positively correlated with the abundance of Diatomeae. Along the existing salinity gradient, the EPR decreased from 4.7 ± 0.39 (A1) to 3.2 ± 0.13 (C31) eggs female-1 day-1 and from 5.19 ± 0.46 (A1) to 3.66 ± 0.05 (C31) eggs female-1 day-1 for O. nana and O. similis, respectively, and this could mainly be attributed to the hypersaline conditions. The positive relationship between the abundance of Diatomeae with all traits shows, that these may be a vital component of the diet for the investigated species. The reduction of body size of Oithona along the salinity gradient demonstrates that such a character could mainly be due to a network of causes, related with the confinement and not only to salinity.

The copepod assemblages and abiotic parameters were investigated at 11 stations in a large coastal lake (Lake Manzalah, Nile Delta) from 2009–2010 in order to verify any impacts of eutrophication and salinity on the copepod species composition. The environmental conditions and the copepod assemblages appeared to have changed in comparison with previous studies, possibly because of increasing eutrophication and invasions of non-indigenous species (NIS). The aim of the present study was the identification of species which can be used as ecological indicators of high trophic status. Among the nine copepod species of Lake Manzalah, Acartia tonsa, Mesocyclops ogunnus, and Apocyclops panamensis were reported for the first time. Acartia tonsa, a well-known NIS for the Mediterranean, numerically dominated the copepod assemblages in some portions of the lake. The distribution of Acanthocyclops trajani and Thermocyclops consimilis was insensible to eutrophication because they can stand high levels of nutrients and hypoxia. Compared with previous reports, the copepod assemblage of Lake Manzalah was richer in species. The invasions of NIS, in addition to the heterogeneous progress of eutrophication in the lake, created an environmental mosaic with many species in total, but with single areas suitable for only a small number of them.

The distribution and abundance patterns of amphipods associated withSargassumspecies were studied on a spatial scale along Kuwait’s coastal waters. Macroalgae, in particularSargassumspp., are known to host a high biodiversity of marine fauna, particularly amphipods, when compared to non-Sargassum(“clear”) areas. Amphipods are an important component in the food web, being consumed by different stages of fish.Sargassumwas sampled from four different stations in Kuwait’s waters to determine the amphipod species composition and density. Physicochemical parameters were measured at the time of sampling at each station, focusing on turbidity, as this can promote variation in the faunal distribution between areas, and it was the only non-biological factor showing a distinctive pattern between stations in this study. The objectives of this study thus were to describe the amphipod biodiversity inSargassumcommunities and to measure the difference in diversity betweenSargassumand clear areas, while concurrently taking into account the effect of turbidity. The most abundant amphipods represented werePontocratessp. (cf.arenarius(Spence Bate, 1858)),Ericthoniussp. (cf.forbesiiHughes & Lowry, 2006),Maxillipius rectitelsonLedoyer, 1973, andPodocerus mamlahensisMyers & Nithyanandan, 2016. Among the measured physicochemical parameters, only turbidity had a significant effect on the biodiversity of amphipods (,) with a negative relationship based on the general linear model test. The effect ofSargassumand non-Sargassumareas on amphipod diversity was statistically not significant (,). Also, there was no interaction between turbidity andSargassum/clear areas (,). However, the diversity was observed to be higher inSargassumareas of all stations as compared to their clear counterparts, except in Khairan during January 2016, where the situation was the opposite. The abundance was highest in low turbidity, particularly at Salmyia station, compared to the high turbidity conditions at the stations at Failaka and Green Island. The species composition differed as well, the number of species found being the highest in theSargassumarea of Salmyia Station and the lowest at Failaka Island (highest turbidity). Only Salmyia Station (low turbidity) contained 27 species in itsSargassumarea, of which only few were present at other stations in both areas. Turbidity affected the diversity of amphipods, and diversity was higher inSargassumareas at all stations except Khairan in January 2016, but that difference was not significant.