Abstract
Port Biological Baseline Surveys (PBBS) are standardized surveys of the indigenous and non-indigenous marine biodiversity within harbour activities. They provide a baseline for monitoring changes in the structure and function of harbour communities. This study conducted in 12 fishing and industrial harbours from January to December 2018 was the first initiative of a Port Baseline Survey aimed to assess the impact of biological invasions in harbours of the Gulf of Gabès (GG), Tunisia. A total of 174 macrobenthos species were recorded, belonging to eight phyla, with a dominance of crustaceans (32%), molluscs (31%) and polychaetes (20%). Among these species, 57 were non-indigenous species (NIS) for Tunisian waters, while 27 species were recorded for the first time in GG harbours, and three decapods (Dyspanopeus sayi, Hippolyte prideauxiana and Pilumnus minutus) and one amphipod (Hamimaera hamigera) were newly recorded from Tunisian waters. Two main categories of harbours are distinguished according to their macrobenthic communities and environmental conditions. The industrial harbours yield higher richness and abundance of NIS than the fishing harbours. The ALEX metric is used to evaluate the biological invasion status of the Gulf of Gabès harbours and shows that their status ranges from unaffected in fishing harbours to extremely affected in industrial harbours. Three biotic indices (AMBI, BO2A and BENTIX) are applied to assess the ecological status of harbours, which varies from moderate to good. ALEX and the other biotic indices are significantly correlated with harbour characteristics, maritime traffic and edaphic factors (organic matter and chemical contamination). The present study provides a data baseline for the implementation of environmental policies and management plans in the future.
Highlights
Harbours are considered as one of the most disturbed coastal ecosystems due to the increase in anthropogenic pressures (Chan et al 2016; Dauvin et al 2017; Chatzinikolaou et al 2018; Romanelli et al 2019; Dimitriou et al 2020)
Salinity is higher in summer and autumn, with high values being recorded in SFF (41.5± 0.05) and GAF (41.2± 0.01). pH shows a spatial variation during the sampling period, with low values in industrial harbours (F= 12.03; p< 0.01)
Many Non-Indigenous Species (NIS) are newly reported for the Gulf of Gabès (GG) and have become established in the industrial ports owing to the continual increase of harbour activities
Summary
Harbours are considered as one of the most disturbed coastal ecosystems due to the increase in anthropogenic pressures (shipping activities, pollution and dredging) (Chan et al 2016; Dauvin et al 2017; Chatzinikolaou et al 2018; Romanelli et al 2019; Dimitriou et al 2020). Several studies have been carried out to identify the biota present in harbours to allow proper monitoring programmes of these marine environments This strategic step needs to be preceded by a thorough and synergic study of the biological components of the ecosystems concerned (Mandal and Harkantra 2013; Lehtiniemi et al 2015). Marine bioinvasions have become one of greatest global threats to the diversity and integrity of indigenous communities These invasions are considered as drivers of irreversible impacts in host environments while affecting the diversity and the stability of native habitats (Spagnolo et al 2019). The number of NIS recorded in the Mediterranean Sea has been increasing, which affects habitats and ecosystem functioning (Katsanevakis et al 2014, 2016)
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