Correlation between pollution and decline of Scleractinian Cladocora caespitosa (Linnaeus, 1758) in the Gulf of Gabes

Abstract

During an expedition in 2014 in the Gulf of Gabes that aimed to evaluate the impact of the pollution of the phosphate industry on the marine environment, numerous dead coral fragments were retrieved from several stations along a 18 km long transect in front of the industry complex of Gabes. Detailed taxonomy of these coral fragments shows clearly that all fragments belong to the species Cladocora caespitosa (Linnaeus, 1758). Quantitative analysis of the coral fragments indicates a positive correlation with stations characterized by positive bathymetric anomalies. We suggest the presence of probable small-scaled (up to 4 m high) biogenic (palaeo-) build-ups composed mainly of coral colonies and bryozoans. Radiocarbon dating of three coral fragments show ages as old as 1897, 1985 and 1986 AD and suggests the presence of living C. caespitosa as close as 6 km to the phosphate treatment industry of Gabes at least until 1986 AD. This latter age coincides with the construction of the ammonium phosphate production plant, in 1979, in the Gulf of Gabes with an increase of the natural phosphate production. The higher impact of pollution on the marine environment in the inner part of the Gulf of Gabes likely induced the decline of C. caespitosa. This is well in agreement with enhanced siltation processes suggested by the sedimentary facies and grain-size analyses presently characterizing the Gulf of Gabes nowadays.

Impact of industrial phosphate waste discharge on the marine environment in the Gulf of Gabes (Tunisia)

“…The decline of the coral Cladocora caspidosa in the inner part of the Gulf of Gabes during the last 30 years [ 28 ]. Presently living C .…”

“…Consequence of the large production of PG is a severe heavy metal contamination of seawater and sediments (e.g., [ 24 – 28 ]), which has a strong impact on the marine fauna by bioaccumulation effect since elementary phosphorus can be assimilated in sediments in various phases [ 29 – 31 ].…”

Spatial distribution and contamination assessment of heavy metals in marine sediments of the southern coast of Sfax, Gabes Gulf, Tunisia

“…Most of recent studies aiming at the assessment of marine environment quality in GG revealed an enrichment of surface sediments with a wide range of pollutants especially in heavy metals, showing a potential degradation of sediments quality (Serbaji et al, 2000;Ayadi et al, 2014;Gargouri et al, 2011;Ghannem et al, 2011;Houda et al, 2011;El Zrelli et al, 2015;Rabaaoui et al, 2015). It also resulted in the appearance of red tides (Hamza and el Abed, 1994), the disappearance of some marine species (El Kateb et al, 2016), unbalance in different local benthic communities (Rabaoui et al, 2015) and malformations in different benthic foraminifera species (Ayadi et al, 2016). However, none of the studies in the southern coast of Sfax have reported the distributional patterns of heavy metals according to the granulometric and mineralogical characteristics of the surface marine sediments.…”

Living (stained) foraminifera in the Lesser Syrtis (Tunisia): influence of pollution and substratum

“…The adverse environmental conditions in the Gulf of Gabes are well documented (e.g., El Zrelli et al, 2015;El Zrelli et al, 2017;El Kateb et al, 2016;El Kateb et al, 2018b and references therein). The research of El Zrelli et al (2017) highlighted that the order of heavy metal concentrations in sediments follows Zn>Cd>Cr>Pb>Cu>Hg and that at least Zn and Cd derive from phosphogypsum.…”

“…Resultant heavy metals bioaccumulation in marine fauna is documented (Rabaoui et al, 2014;Messaoudi et al, 2009). The decline of the coral Cladocora caespitosa in the region (El Kateb et al, 2016) and of macrobenthic faunas (Zaouali, 1993;Pérez Domingo, Castellanos & Junoy, 2008;El Lakhrach et al, 2012) can be also attributed to the pollution.…”