Key Drivers for Copepod Assemblages in a Eutrophic Coastal Brackish Lake

Neila Annabi-Trabelsi,Yousef Al-Enezi,Genuario Belmonte,Gamal El-Shabrawy,Madhavapeddi N. V. Subrahmanyam,Habib Ayadi,Mohamed E. Goher,Mohammad Ali

doi:10.3390/w11020363

Abstract

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.

Highlights

Eutrophication is recognized as a global environmental issue and one of the most severe hazards for aquatic ecosystems [1,2] where it leads to significant changes in the community structure and ecosystem functioning [3,4]
In many Mediterranean coastal lakes, the eutrophication level is enhanced by the general absence of tide excursions, other than by anthropogenic pressures such as those arising from intensive use of fertilizers in the surrounding
Coastal lakes are susceptible to invasive non-indigenous species (NIS) whose settlement is generally favored in polluted and/or physically degraded situations [10,11]

Summary

Introduction

Eutrophication is recognized as a global environmental issue and one of the most severe hazards for aquatic ecosystems [1,2] where it leads to significant changes in the community structure and ecosystem functioning [3,4]. It is responsible for large increases in the biomass of primary producers, severe reductions in diversity, and declines in water quality [5,6]. Among the most commonly known planktonic invaders are copepods and cladocerans [12]

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