Effects of Eutrophication on Plankton Abundance and Composition in the Gulf of Gabès (Mediterranean Sea, Tunisia)

Abstract

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.

Spatio-Temporal Variations of Zooplankton and Correlations with Environmental Parameters around Tiaowei Island, Fujian, China

“…The Oithona species occurs in almost any marine environment, which is possibly due to its euryhaline and eurythermal characteristics [44,45]. Hence, Oithona was the main contributor to the copepod abundance in temperate and subtropical seas, which corroborates with the present study [14,45].…”

“…However, the composition of zooplankton species is susceptible to environmental changes, and they can respond quickly to rapid environmental changes, including physicochemical, biological and microbiological parameter changes [11,12]. For instance, zooplankton communities can be used as indicators to evaluate the potential influence of eutrophication [13][14][15], acidification [16,17], global warming [6,18,19] and even ultraviolet radiation [20]. In particular, the abundance and compositions of phytoplankton and Copepoda are used as ecological indicators to investigate the effect and early process of eutrophication in a localized area [14].…”

“…For instance, zooplankton communities can be used as indicators to evaluate the potential influence of eutrophication [13][14][15], acidification [16,17], global warming [6,18,19] and even ultraviolet radiation [20]. In particular, the abundance and compositions of phytoplankton and Copepoda are used as ecological indicators to investigate the effect and early process of eutrophication in a localized area [14]. Hence, zooplankton was chosen to monitor the impact of environmental change and industrial construction.…”

“…Meanwhile, these copepods are widely distributed in the East China Sea and Taiwan Strait [33][34][35][36][37], suggesting regional distribution characteristics and a local community structure of zooplankton. The dominance of copepods in the zooplankton community was well-documented in various estuaries across the world in both tropical and temperate regions [14,38,39], indicating that their composition can be an important bio-indicator for environmental monitoring. Among copepods, Oithona copepods showed the largest abundance in the zooplankton community in this research.…”

The Spatial Distribution of Copepod Functional Traits in a Highly Anthropized Mediterranean Coastal Marine Region

“…These conditions may also expose Oncaea to pollutants originating from urban areas. In fact, both Oncaea and Oithona species, thanks to their adaptation strategies, in particular their low metabolic rate and ability to feed on a wide range of prey [86,95], are copepods tolerant or insensitive to pollution [2,96,97].…”