Structure of the benthic macrofauna of an anthropogenic influenced area: Skhira Bay (Gulf of Gabès, central Mediterranean Sea)

Seasonal benthic species composition linked to coastal defense structures (CDS) in Kuala Nerus, Terengganu, Malaysia

Background

The natural hydrodynamic process of Kuala Nerus, Terengganu, has changed since the extension of Sultan Mahmud Airport runway in 2008. Consequently, severe coastal erosion has occurred in the area, particularly during the northeast monsoon season (NEM). Numerous types of coastal defense structures (CDS) have been constructed to protect the coastline. Despite the loss of esthetic values, the effect of CDS construction on marine organisms in the area remains unknown. Hence, this study aims to assess the ecological aspects of macrobenthic compositions at the CDS area of Kuala Nerus, Terengganu, based on the differences between the southwest (SWM) and northeast (NEM) monsoon seasons.

Methods

Macrobenthos were collected from the sediment in July (SWM) and December 2021 (NEM) using the Ponar grab at 12 substations from five sampling stations.

Results

The density of macrobenthos was higher in SWM (48,190.82 ind./m2) than in NEM (24,504.83 ind./m2), with phylum Mollusca recording the highest species composition (60-99.3%). The macrobenthos species had a low to moderate level of diversity (H' = 1.4-3.1) with the species were almost evenly distributed (J' = 0.2-0.8). Windward substations exhibited coarser grain sizes (38.56%-86.84%), whereas landward substations exhibited very fine grain sizes (44.26%-86.70%). The SWM season recorded a higher organic matter content (1.6%-6.33%) than the NEM season (0.4%-3.1%). However, metal concentrations in the surface sediment were within the safe range and permissible limits for both seasons, inferring that the macrobenthos composition was unaffected.

Discussion

This study demonstrated that the CDS associated with the monsoon system has controlled the hydrodynamics and nearshore sedimentary processes in the Kuala Nerus coastal zone, thereby affecting the macrobenthos population, in terms of richness and density. The ecological and energetic effects of the coastal structures in different seasons have resulted in a more significant result, with the SWM exhibiting a higher macrobenthos composition than the NEM.

Assessment of trace elements and fluoride originating from phosphogypsum in the sediment of Gulf of Gabes (southeastern Tunisia): what are the potential sources of accumulation and bioavailability?

To assess potential impacts of industrial activities on the pollution status of Gulf of Gabes, twenty sediment and water samples along with phytoplankton enumeration were achieved at different stations with specific features. Comparing trace element concentrations in sediment to applicable SQG standards, we were intrigued by an accumulation of Zn, Cr, Ni, and especially Cd, which exhibited relatively high content compared to these standards. Moreover, trace metal bioavailability was high in front of industrial discharge areas. The chemical speciation pointed out a high affinity of Pb, Zn, Cr, Mn, Ni, Co, and Fe for the residual fraction of the sediment. Bioavailability of trace elements was confirmed in surface sediment by the presence of a potential toxic fraction especially in front of industrial discharge areas. Toxicity assessment performed for the first time in the Gulf of Gabes through SEM and AVS models pointed to a high potential risk near both Ghannouch and Gabes Ports. Finally, the correlations between phytoplankton species and the labile fraction inferred potential phytoplankton bioaccumulation of Zn, Cu, and Cd both in the seawater and in the labile fraction.

Reef crab population changes after oil spill disaster reach Brazilian tropical environments

The oil spill that reached Brazilian Coast in 2019 was one of the most extensive disasters and its effects on distinct species are still under investigation. This study evaluated the effects of the oil spill on the crab Pachygrapsus transversus in four reef areas in Northeast of Brazil that are also under different levels of chronic anthropogenic impacts. Changes in population aspects were investigated including maturity, sex ratio, and relative growth considering periods before and after the oil spill. An acute decrease in the number of females captured in areas most affected by oil spill was evident and may be associated with the closure of burrows used for protection. Crabs from the most touristic area presented a decrease in the medium size of carapace and maturation compared to crabs from other less visited areas, which highlights the importance of studying the effects of impacts on marine fauna.

Ecological status assessment and non-indigenous species in industrial and fishing harbours of the Gulf of Gabès (central Mediterranean Sea)

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.

Macrobenthic communities in the tidal channels around the Gulf of Gabès, Tunisia

A yearlong seasonal survey was carried out during 2016-2017 at 26 stations representing four tidal channels of the north-western part of the Gulf of Gabès (Tunisia). The area studied (characterized by a maximum tidal range of 2.3 m) was subjected to diverse anthropogenic pressures: from the phosphate industry and its metallic pollution, unauthorized bottom trawling in shallow water (known locally as 'Kiss'), and organic pollution from the nearby urbanized areas. A total of 23,506 invertebrates representing 311 taxa were collected. Dominant taxa were the polychaetes with 51.4% of the individuals collected and 39.3% of the taxa, the amphipods (18.6% and 15.5%), the tanaids (12.3% and 2.6%), and the molluscs (11.5% and 18.3%). The mean annual abundances varied widely from one channel to another: from 300 to 3700 ind·m^-2. The stations located in deeper waters exhibited greater variability. Measurements of abundance revealed seasonal changes with maximum values in winter, spring, and lower numbers in summer. Each tidal channel was characterized by specific features in the fauna. The macrofauna were dominated by the polychaete Cirratulus cirratus (mainly in spring) and the amphipod Microdeutopus anomalus (mainly in winter), whilst both of the tanaids, Apseudopsis gabesi (the first sighting reported for the area) and A. mediterraneus, were found to be abundant in winter in at least one of the four channels. Species are mainly deposit feeders, herbivorous and omnivorous. The analyses on spatial and temporal changes of the macrofauna population revealed variations according to the composition of the fauna increasing or falling along the channels and as a function of seasonal changes. In spite of a high level of anthropogenic activities, the Ecological Status (ES) assessment (applying the AMBI and M-AMBI indices) attributed High or Good ES for 10 stations, Moderate ES for 11 stations and five stations showed a poor ES at least during one season. Sampling subtidal stations in the future to survey long-term degradation of such ecosystems of the coastal environment of the Gulf of Gabès in Tunisia is proposed.

A biological clean processing approach for the valorization of speckled shrimp Metapenaeus monoceros by-product as a source of bioactive compounds

The efficiency of the proteolytic strain Anoxybacillus kamchatkensis M1V in the fermentation of speckled shrimp by-product was investigated for the recovery of a deproteinized bioactive hydrolysate. The biological activities of the resulting hydrolysate were also examined by applying several antioxidant and enzyme inhibitory assays. The strain M1V was found to produce high level of protease activity (2000 U/mL) when grown in media containing only shrimp powder at 25 g/L. The crude protease displayed a significant deproteinization capabiliy, with the best efficiency (48%) being recorded for an enzyme to substrate (E/S) ratio of 30 U/mg. Following the deproteinization, chitin was recovered and the authenticity was confirmed by Fourier-transform infrared spectroscopy (FTIR) analysis. On the other hand, the obtained hydrolysate showed a significant enzymatic inhibitory potential against acetylcholinesterase, tyrosinase, amylase, and angiotensin I convertase, and a strong antioxidant activity. Graphical Abstract.

Response of benthic macrofauna to multiple anthropogenic pressures in the shallow coastal zone south of Sfax (Tunisia, central Mediterranean Sea)

Anthropogenic activities including coastal industries, urbanization, extensive agriculture and aquaculture as well as their cumulative impacts represent major sources of perturbation of marine coastal systems. Macrobenthic communities are useful ecological indicators for monitoring the health status of marine environments (or polluted environments). The present study reports, for the first time, the response of benthic macrofauna sampled during two years survey (2015-2016) to multiple anthropogenic pressures on the coastal zone south of Sfax (Tunisia). A total of 12 stations were monitored seasonally at locations downstream from the main potential sources of disturbance. 106 macrobenthos taxa, belonging to six animal phyla and 70 families, were identified with a dominance of polychaetes (42%), crustaceans (35%) and molluscs (18%). We used an ANOVA test and cluster analysis to identify spatial gradient linked to environmental and anthropogenic factors, including depth, sedimentary texture and anthropogenic activities (i.e. phosphogypsum discharges).The macrofauna present lowest species number and abundance on stations undergoing anthropogenic inputs, which are extremely polluted by heavy metals (Cd, Cu, F and N) and excess of organic matter. Univariate parameters reveal a general trend of increasing species diversity with increasing distance from the pollution source. The polluted stations are strongly dominated by carnivores, and selective deposit feeders, and more closely linked to the availability of trophic resources than to anthropogenic constraints. The seasonal changes in macrobenthic abundance, diversity indices and community structure are mainly linked to the biological cycle (e.g. recruitment events) of the dominant species. Biotic indices (AMBI and BO2A) classified the coastal zone south of Sfax as moderate and good ecological status. This study suggests that initiating a long-term monitoring programme would improve our understanding of the temporal changes of macrobenthic communities of this ecosystem, contributing to the assessment of effective management and conservation measures in this disturbed area.