Biodiversity patterns of the coral reef cryptobiota around the Arabian Peninsula.

The Arabian Peninsula accounts for approximately 6% of the world's coral reefs. Some thrive in extreme environments of temperature and salinity. Using 51 Autonomous Reef Monitoring Structure (ARMS), a standardized non-destructive monitoring device, we investigated the spatial patterns of coral reef cryptobenthic diversity in four ecoregions around the Arabian Peninsula and analyzed how geographical and/or environmental drivers shape those patterns. The mitochondrial cytochrome c oxidase subunit I (COI) gene was used to identify Amplicon Sequence Variants and assign taxonomy of the cryptobenthic organisms collected from the sessile and mobile fractions of each ARMS. Cryptobenthic communities sampled from the two ecoregions in the Red Sea showed to be more diverse than those inhabiting the Arabian (Persian) Gulf and the Gulf of Oman. Geographic distance revealed a stronger relationship with beta diversity in the Mantel partial correlation than environmental distance. However, the two mobile fractions (106-500 µm and 500-2000 µm) also had a significant correlation between environmental distance and beta diversity. In our study, dispersal limitations explained the beta diversity patterns in the selected reefs, supporting the neutral theory of ecology. Still, increasing differences in environmental variables (environmental filtering) also had an effect on the distribution patterns of assemblages inhabiting reefs within short geographic distances. The influence of geographical distance in the cryptofauna assemblages makes these relevant, yet usually ignored, communities in reef functioning vulnerable to large scale coastal development and should be considered in ecosystem management of such projects.

Trace element levels in the muscles of three tern species (Aves: Laridae) from the western Arabian Gulf: environmental assessment and implications for conservation.

In the Arabian Gulf (called also Persian Gulf; hereafter 'the Gulf'), Jana and Karan Islands are recognized as one of the most Important Bird Areas in the region. Many migratory breeding seabirds, like the Greater Crested Tern Thalasseus bergii, White-cheeked Tern Sterna repressa and Bridled Tern Onychoprion anaethetus, depend on these islands during the breeding season. However, these aquatic wildlife species are suffering from intensified urban and industrial coastal development and various contamination events including wars and related oil spills. In this study, we used these three piscivorous top predator birds to analyse the levels of 19 trace elements (TEs; i.e. Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, Pb, Sr, V and Zn) in 15 muscular tissue samples from Jana and Karan Islands. PERMANOVA analysis showed no difference in contamination profile between sites nor between species probably due to their spatial and ecological proximity and therefore similar levels of exposure to TEs. Comparing these levels with existing literature, our results showed no particular concern for all elements, except for Al (maximum values recorded = 116.5 µg g-1 d.w.) and, in two samples, Ba (33.67 µg g-1 d.w.) and Pb (5.6 µg g-1 d.w.). The results can be considered as an initial step for supplementary evaluations with a larger number of samples and specified time intervals for the collection of specimens. This study provided baseline information on the pollution status of these two ecologically important sites which require a continuous biomonitoring programme.

A review on sea cucumber (Bengali: Somuddro Sosha) as a bioindicator of heavy metal contamination and toxicity.

This review paper exhibits the underexplored realm of heavy metal contamination and associated risks in sea cucumbers (SCs), which hold significant importance in traditional Asian marine diets and are globally harvested for the Asian market. The assessment focuses on heavy metals (HMs) presence in various SC species, revealing a global trend in HMs concentrations across anatomical parts: Fe > Zn > As > Cu > Hg > Pb > Mn > Cr > Ni > Cd. Specific species, such as Eupentacta fraudatrix, Holothuria mammata, Holothuria polii, Holothuria tubulosa, and Holothuria atra, exhibit heightened arsenic levels, while Stichopus herrmanni raises concerns with mercury levels, notably reaching 3.75 mg/kg in some instances, posing potential risks, particularly for children. The study sheds light on anthropogenic activities such as cultivation, fishing, and shipping, releasing HMs into marine ecosystems and thereby threatening ocean and coastal environments due to the accumulation and toxicity of these elements. In response to these findings, the paper suggests SCs as promising bioindicator species for assessing metal pollution in marine environments. It underscores the adverse effects of human actions on sediment composition and advocates for ongoing monitoring efforts both at sea and along coastlines.

Hurdles and opportunities in implementing marine biosecurity systems in data-poor regions.

Managing marine nonindigenous species (mNIS) is challenging, because marine environments are highly connected, allowing the dispersal of species across large spatial scales, including geopolitical borders. Cross-border inconsistencies in biosecurity management can promote the spread of mNIS across geopolitical borders, and incursions often go unnoticed or unreported. Collaborative surveillance programs can enhance the early detection of mNIS, when response may still be possible, and can foster capacity building around a common threat. Regional or international databases curated for mNIS can inform local monitoring programs and can foster real-time information exchange on mNIS of concern. When combined, local species reference libraries, publicly available mNIS databases, and predictive modeling can facilitate the development of biosecurity programs in regions lacking baseline data. Biosecurity programs should be practical, feasible, cost-effective, mainly focused on prevention and early detection, and be built on the collaboration and coordination of government, nongovernment organizations, stakeholders, and local citizens for a rapid response.

Bioaccumulation of trace elements and hydrocarbons in chondrichthyans of the western Arabian Gulf: Environmental and human health risk assessment and implications for conservation.

This is a first attempt to assess the levels of trace elements, PAHs, and TPHs in six elasmobranch species (Carcharhinus dussumieri, C. sorrah, Chiloscyllium arabicum, Gymnura poecilura, Sphyrna lewini, S. mokarran) from the Arabian Gulf. The chemical analysis showed that the concentrations of contaminants differed significantly between liver and muscle samples with both pelagic and benthic species and all families. For all species, contaminant concentrations were significantly higher in the liver than in the muscle. While muscle contaminant concentrations differed significantly with respect to species' lifestyles and families, those of liver showed no significant differences between pelagic and benthic species, neither between the four families nor between the six species. None of the analysed contaminants exceeded the internationally recognized standards in all studied species. These results enrich the knowledge on the bioaccumulation of contaminants in elasmobranchs and allow to assess the environmental status of the Arabian Gulf.

Economic losses related to the reduction of Posidonia ecosystem services in the Gulf of Gabes (Southern Mediterranean Sea).

In the early XXth century, the Gulf of Gabes in SE Tunisia used to host the most extended Posidonia oceanica seagrass beds in the Mediterranean basin and was a highly productive hotspot of benthic species. Since the 70's, >500 million t of wet toxic phosphogypsum discharges from a fertilizer industrial complex have led to the gradual loss of ∼90 % of its initial surface. This drastic shrinkage is accompanied by significant value losses originated from the direct and indirect-use services of which the most important ones are small scale fisheries and carbon storage function. Using market valuations of a number of services we estimate economic losses at 105 million € in 2014 (∼915€/ha), i.e., around 115 % of the added value of the gabesian fertilizer factories for the same year. Value losses should increase in the near future in relation with the COP26 agreements which boosted the open carbon credit market. Without actions to reduce negative production externalities caused by the fertilizer industry in the Gulf of Gabes it would not be possible to recover Posidonia ecosystems in this region leading to further economic, ecologic, and cultural losses.

PET plastics as a Trojan horse for radionuclides.

Mismanaged plastic waste interacts with secondary environmental pollutants, potentially aggravating their impact on ecosystems and human health. Here we characterized the natural and artificial radionuclides in polyethylene terephthalate (PET) bottles collected from the industrial littoral discharge of a phosphate fertilizer plant. The activity concentrations in littered bottles ranged from 0.47 (208Tl) to 12.70 Bq·kg-1 (226Ra), with a mean value of 5.30 Bq·kg-1. All the human health risk assessment indices (annual intake, annual effective dose, and excess lifetime cancer risk) estimated for radionuclides associated with ingestion and inhalation of microplastics were below international safety limits. Our results demonstrated that PET can be loaded with natural and artificial radionuclides, and potentially act as a carrier to transfer radionuclides to humans, posing a new potential health risk. Increased use, mismanagement and fragmentation of plastic waste, and continued interaction of plastic waste with radioelements may lead to enhanced radiation exposure in the future.

Seasonal patterns of microplastics in surface sediments of a Mediterranean lagoon heavily impacted by human activities (Bizerte lagoon, Northern Tunisia).

In this paper, we investigated seasonal variations in concentrations of microplastics (MPs) in surface sediments of a lagoon heavily impacted by human activities, located in northern Tunisia (the Bizerte lagoon, southern Mediterranean Sea). Analyses of 112 sediment samples collected from 28 stations between May 2019 and February 2020 revealed significant seasonal variation in concentrations of total MPs, with the highest levels recorded in August 2019 (109.6 ± 59.8 items kg-1 DS (dry sediment)) and the lowest in February 2020 (33.2 ± 22.0 items kg-1 DS). In terms of polymer types, polyethylene particles were the most abundant throughout the year, followed by polypropylene, polyvinyl chloride, and polyethylene terephthalate. Spatial variations in total MP concentrations were found to depend on several environmental factors, including proximity to the coastline, level of anthropogenic pressure, location inside the lagoon, and presence/absence of vegetation. The upper 5-cm surface sediment layer of the lagoon was found to contain ~ 9.96 × 1010 MP particles, equal to ~ 248.97 t of plastic. Similar patterns of microplastic composition and structure were found throughout the year, revealing the same plastic pollution hotspots during all seasons. This indicates that sources of plastic pollution are land-based and originate from coastal urban, industrial, and agricultural areas, as well as from major freshwater streams. The findings of the present work can help to develop an efficient environmental management plan aiming to reduce and/or stop the spread of plastic pollution and its impacts on the socially and economically important ecosystem of the Bizerte lagoon.

Essential fish habitats of demersal fish in the western Arabian Gulf.

Information about habitats occupied by aquatic organisms while completing critical stages of their lives, called essential fish habitats, is crucial for their sustainability. In this work, we determine essential fish habitats (nursery and spawning grounds) of several fish species inhabiting Saudi territorial waters in the western Arabian Gulf using data from multiple surveys (2013-2016), geostatistics, and indicator species analysis. We built geostatistical maps of spatial distributions of juvenile and mature fish and examined the strength of association of each species to its observed nursery and spawning areas. Fish nursery areas were generally located in nearshore locations while spawning areas were located in offshore waters. The patterns of nursery and spawning grounds were highly varied among species, supporting a hypothesis of habitat-species heterogeneity: different species use different locations as nursery and spawning grounds. This information can be used as a roadmap for future evidence-based spatial planning and ecosystem-based management.

Rare earth elements characterization associated to the phosphate fertilizer plants of Gabes (Tunisia, Central Mediterranean Sea): Geochemical properties and behavior, related economic losses, and potential hazards.

This is the first study on the behavior and industrial fluxes of rare earth elements (REE) in the coastal fertilizer plants of Gabes (south-eastern Tunisia), the economic losses related to their wastes, and their environmental and human health hazards. The concentrations of 16 REE were assessed in phosphate rock (PR), phosphogypsum (PG) and phosphogypsum foam (PGF) samples, collected from Gabes plants. REE concentrations ranged from 0.23 (for Sc in PG) to 309.33 mg kg-1 (for Ce in PGF). Ce was the most abundant in the three matrices, with concentrations ranging between 80.40 (in PG) and 309.33 mg kg-1 (in PGF). PGF was the most enriched with REE (1075.32 mg kg-1). The annual flow of REE from the fertilizer factories to the marine environment may reach 1523.67 t. The economic losses related to the discharge of phosphogypsum REE in the Gulf of Gabes (GG) was estimated at ~58 million US$ y-1. The potential hazards of discharged REE on the local environment and human health were also evaluated and discussed. These findings show the need for the development of a new industry exploiting REE from phosphogypsum wastes (short term) and phosphate ores (long term) which should lead to reduce its high environmental and human health footprint and to potential economic gains.

Surface sediment enrichment with trace metals in a heavily human-impacted lagoon (Bizerte Lagoon, Southern Mediterranean Sea): Spatial distribution, ecological risk assessment, and implications for environmental protection.

Although several studies previously assessed the contents of trace metals in the sediments of the heavily human-impacted lagoon of Bizerte (northern Tunisia), multi-analytical approaches have not been, so far, used to assess the ecological risks in this water body. This study attempts to provide a comprehensive ecological risk assessment related to the enrichment of the lagoon sediments with seven metals (As, Cd, Cr, Cu, Hg, Pb, and Zn). Significant spatial variations were found in the metal concentrations in sediments, in relation to the degree of coastal human activities and hydrodynamics. This was confirmed with the results of the three pollution indices, Cf, PLI, and Igeo. Concordant results were found with most of the indices used to assess the ecological risks (PERI, PEL, ERL, ERM, M-ERM-Q, TU), indicating higher risks in the southern part of the lagoon. These findings can help to improve the environmental management plan of the socio-economic important lagoon of Bizerte.

Strengths and weaknesses in the long-term sustainability of two sympatric seabreams (Argyrops spinifer and Rhabdosargus haffara, Sparidae).

Argyrops spinifer and Rhabdosargus haffara are two sympatric seabream species making important contributions to fisheries landings in the western Arabian/Persian Gulf. We identified the strengths and weaknesses in the long-term sustainability of A. spinifer and R. haffara stocks by integrating multiple sources of data, including fisheries catch and effort statistics, life history traits, scientific trawl surveys and historical length frequency distribution. Four strengths were identified in A. spinifer: wide distribution of juveniles, positive association to the network of de facto fishing exclusion areas created by hundreds of oil-gas facilities, early maturation and the existence of large and old individuals. A. spinifer suffers from two potential weaknesses: slow growth rate and higher exploitation pressure on the small-sized individuals. R. haffara, on the other hand, has a strength of having a short life span and a fast growth rate, characteristics that make it robust to unfavourable conditions. R. haffara suffers from two weaknesses: the lack of association to the oil and gas facilities, and the preference for nearshore shallow waters with stronger negative anthropogenic impacts. Identified strengths and weaknesses of these two sparids provided a preliminary assessment about their long-term sustainability, as well as a roadmap about how to develop different management strategies to meet specific objectives.

A baseline quantitative assessment of deep-sea benthic fauna of the Gulf of Aqaba (Northern Saudi Arabia, Red Sea).

The Gulf of Aqaba (hereafter 'the Gulf') is a narrow, semi-enclosed, warm, high saline, and oligotrophic water body. This baseline study provides the first quantitative data on deep-sea (207-1281 m depth) benthos of the Gulf. Fifty-five benthic species (predominantly polychaetes) with a density of 160-670 ind. m-2, species richness of 11-25, and Shannon-Wiener diversity (H') of 3.14-4.17 bits. ind.-1 were recorded from nine stations. The density and H' of benthos of the Gulf are comparable with those of the Red Sea, while both are lower than those reported from the Arabian Sea and the Mediterranean Sea. The good-high ecological status of benthic communities indicates the absence of major stress in the deep-sea habitats of the Gulf. As large-scale urbanization is proposed in the Saudi coastal areas of the Gulf, this study is expected to provide a baseline dataset for future environmental impact assessments.

Long-term ecological changes in fishes and macro-invertebrates in the world's warmest coral reefs.

The Arabian Gulf is a natural laboratory for examining the consequences of large-scale disturbances due to global warming on coral reef ecosystems because of its extreme temperature regime. Using a coral reef monitoring time series extending from 1985 to 2015, we examined the long-term ecological changes in fish and macro-invertebrate communities as these habitats suffered heat shocks. We used a GLMM modelling framework to obtain clean annual signals in community indicators from noisy data. We also visualized temporal change in the taxonomic composition of fishes and macro-invertebrates. A phase shift from predominantly reef-building corals to barren grounds occurred between 1996 and 2000. Macro-invertebrates responded rapidly, and most of associated indicators recovered to pre-shift levels in 15 years. Fishes generally had lagged responses to the phase shift and had shifted to a new state with lower abundance, as well as different species composition. Increased levels of herbivory first by macro-invertebrates, mostly sea urchins, and then fishes, could have suppressed macro-algae expansion and consequently led to the dominance of barren ground. When the phase shift occurred, most of the 14 fish families declined in abundance while macro-invertebrate groups increased. Fish families able to utilize non-coral habitats appeared more resilient to the disturbances and subsequent coral degradation. Unlike other regions, we observed high resilience of the coral-dependent butterflyfishes to coral loss, possibly due to local migration from other less-impacted coral reefs. We hypothesized a top-down control mechanism mediated by predation by fishes has contributed to shaping the temporal and spatial patterns of the macro-invertebrates. Our results also revealed differences in spatial preferences among fishes and macro-invertebrate groups, which could be used to set priorities and develop effective conservation and management strategies.

Characterization of microplastics in the surface waters of an urban lagoon (Bizerte lagoon, Southern Mediterranean Sea): Composition, density, distribution, and influence of environmental factors.

Compared to open sea environments, there is still limited knowledge about microplastic levels in semi-enclosed systems such as coastal lagoons. This work aims to assess the levels of MPs in the waters of an urban lagoon (Bizerte lagoon, northern Tunisia) and to study the effects of environmental factors on their distribution and abundance. Average concentration of total MPs was found to be 453.0 ± 335.2 items m-3. The upper 25 cm water layer of the lagoon is most likely to contain ~16.99 × 109 MPs items (which correspond to a total mass of 42.47 t). Fibers were the primary MPs types encountered, and most of MPs particles identified were white and clear-colored. Polyethylene and polypropylene were the predominant polymer types in Bizerte lagoon. Among the various potential plastic sources of MPs, unmanaged domestic plastic wastes are likely to be the major source of plastic pollution in the lagoon. Several environmental factors appeared to influence the distribution and density of MPs in the lagoon waters. These information contribute to better understand the dynamics of MPs in lagoons and to develop environmental management actions.

Microplastics in edible mussels from a southern Mediterranean lagoon: Preliminary results on seawater-mussel transfer and implications for environmental protection and seafood safety.

This study assesses the microplastics (MPs) levels in mussels (Mytilus galloprovincialis) and seawater from a southern Mediterranean lagoon (Bizerte lagoon, Northern Tunisia) and discusses the potential effects of its consumption on human health. Polyethylene was the most abundant in mussels and seawater, followed by polypropylene and cellophane. The lowest and highest average MPs concentrations were recorded in the lagoon channel and southern area of the lagoon, respectively, for both mussels (2.6 ± 1.7-12.0 ± 1.4 items mussel-1) and seawater (0.2 ± 0.1-0.7 ± 0.2 items L-1). Mussels in areas highly polluted with fibers and polyethylene were found to have higher potential to ingest and/or adhere higher numbers of these particles. The annual dietary intake of MPs by Tunisians through the consumption of local mussels was estimated at 4.2 items capita-1 year-1. Even though MPs are not biodegraded and can be excreted by humans, their potential human health risks are discussed in this paper.

Economic impact of human-induced shrinkage of Posidonia oceanica meadows on coastal fisheries in the Gabes Gulf (Tunisia, Southern Mediterranean Sea).

In early XXth century, the Gulf of Gabes (SE Tunisia) used to host the most extended Posidonia oceanica seagrass beds in the Mediterranean Sea, and a highly productive hotspot of benthic/demersal biodiversity. Sponge harvesting and seabed trawling provoked a first step of seagrass degradation. Subsequently, phosphogypsum releases from Gabes Industrial Complex, since mid-1970s, accelerated the decline of the remaining patches. A sharp reduction of coastal fisheries landings took place with the establishment of the last industrial plant units in 1985. The decrease in coastal commercial species landings was found to be directly correlated with P. oceanica decline. The trophic web system switched from a 'benthic-dominated' to a 'pelagic-dominated' system. The economic loss related to coastal fisheries was estimated at ~60 million € in 2014 and the 1990-2014 cumulated loss exceeded 750 million €. This first economic valuation of the only direct-use consumptive value of the coastal fishing service provided by P. oceanica in Gabes Gulf is a first step towards the assessment of the environmental cost of the negative externalities caused by the local phosphate industry. It may be used as a preliminary decision-making aid to consider alternative industrial solutions.

Anthropogenic-induced acceleration of elemental burial rates in blue carbon repositories of the Arabian Gulf.

Along the past century, the Arabian Gulf has experienced a continuous and fast coastal development leading to increase the human pressures on the marine environment. The present study attempts to describe the historical changes of trace elements in the sediments of vegetated coastal habitats in the western Arabian Gulf. 210Pb-dated sediment cores collected from seagrass, mangrove and saltmarsh habitats were analyzed to evaluate historical variations in concentrations and burial rates of 20 trace elements (Al, As, Ba, Ca, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, P, Pb, S, Sr, V and Zn). The highest correlations (Spearman correlation coefficients ≥0.51) were found between crustal elements (Al, Fe, Co, Cr, K, Na, Mg, Mn, Ni, V, and P), suggesting a common crustal source in the Gulf. The increased concentrations of these crustal elements in modern marine sediments of the Arabian Gulf seem to be linked to increased mineral dust deposition in the area. Over the last century, both elemental concentrations and burial rates increased by factors of 1-9 and 1-15, respectively, with a remarkably fast increase occurring in the past six decades (~1960 - early 2000). This is most likely due to an increase in anthropogenic pressures along the Gulf coast. Our study demonstrates that sediments in vegetated coastal habitats provide long-term archives of trace elements concentrations and burial rates reflecting human activities in the Arabian Gulf.

Life history traits and temporal trends of abundance of the orange-spotted trevally (Carangoides bajad) from Saudi waters of the Gulf.

In this study we lay the groundwork for sustainability-oriented fisheries management, by estimating parameters the life history of orange-spotted trevally Carangoides bajad as well as trends of abundance in coral-reef habitats. We observed a new record of maximum size of 720 mm fork length. Carangoides bajad is a moderately long-lived (14 years) and slow-growing (K = 0.085 year-1 ) carangid species, closer to a K-selection species, with higher vulnerability to fishing and lower rates of recovery when the population level is low. Growth and biological composition in terms of length and age categories do not differ between the sexes, but females become mature faster. Reproductively active months (May-August) overlapped with those from Emirati waters further south. The abundance index showed a pronounced drop during 1990-1993, possibly in connection with habitat deterioration during the Gulf War (1990-1991) oil spill. The index increased gradually from 1994 and has fluctuated close to the reference level of 1985 up to the present. Considering the findings of large-sized and old-age individuals and abundance index from coral reefs close to its level three decades back, the C. bajad stock in the western part of The Gulf appears to be in healthy exploitation status despite growing harvesting rates.

DNA barcoding of marine fishes from Saudi Arabian waters of the Gulf.

We used the cytochrome oxidase subunit I (coI) gene DNA to barcode 117 endemic Gulf and cosmopolitan Indo-West Pacific fish species belonging to 54 families and 13 orders. Novel DNA barcodes were provided for 18 fish species (Trachinocephalus sp., Nematalosa sp., Herklotsichthys lossei, Upeneus doriae, Trachurus indicus, Apogonichthyoides taeniatus, Verulux cypselurus, Favonigobius sp., Suezichthus gracilis, Sillago sp., Brachirus orientalis, Pegusa sp., Lepidotrigla bispinosa, Lepidotrigla sp., Grammoplites suppositus, Hippichthys sp., Paramonacanthus sp. and Triacanthus sp.). The species delimitation analysis, conducted with Poisson tree processes- Bayesian PTP (PTP-bPTP) and nucleotide-divergence-threshold (NDT) models), found 137 and 119 entities respectively. Overall, NDT method, neighbour-joining species tree and the prior taxonomic assessment provided similar results. Among the 54 families considered, only 10 (Ariommatidae, Ephippidae, Leiognathidae, Nemipteridae, Plotosidae, Pomacanthidae, Pomacentridae, Priacanthidae and Rachycentridae) showed the occurrence of molecular diagnostic pure characters. The DNA barcoding database developed during this study will help ichthyologists to identify and resolve the taxonomic ambiguities they may encounter with the fishes occurring in The Gulf and throughout the region.