Tunisian Coast Research Articles

A fast and accurate method for specific detection and quantification of the bloom-forming microalgae Karlodinium veneficum in the marine environment.

Karlodinium veneficum is a toxic benthic globally distributed dinoflagellate which has direct impacts on human health and the environment. Early and accurate detection of this harmful algal bloom-forming species could be useful for potential risks monitoring and management. In the present work, a real-time PCR targeting the internal transcribed spacer ribosomal DNA region for the specific detection and absolute quantification of K. veneficum was designed. Then, the assay conditions were adjusted and validated. The developed qPCR was highly specific for the target species and displayed no cross-reactivity with closely related dinoflagellates and/or other microalgal species commonly distributed along the Tunisian coast. Its lowest detection limit was 5 rDNA copies per reaction, which is often considered satisfying. qPCR assay enumeration accuracy was evaluated using artificially inoculated environmental samples. The comparison of the cell abundance estimates obtained by qPCR assay with the theoretical estimates showed no statistically significant difference across a range of concentrations. We suggest that the qPCR approach developed in the present study may be a valuable tool to investigate the distribution and seasonal dynamics of K. veneficum in marine environments.

Improvement of Biomass and Phycoerythrin Production by a Strain of Rhodomonas sp. Isolated from the Tunisian Coast of Sidi Mansour.

Microalgae are photoautotrophic microorganisms known as producers of a large variety of metabolites. The taxonomic diversity of these microorganisms has been poorly explored. In this study, a newly isolated strain was identified based on the 18S rRNA encoding gene. The phylogenetic analysis showed that the isolated strain was affiliated with the Rhodomonas genus. This genus has greatly attracted scientific attention according to its capacity to produce a large variety of metabolites, including phycoerythrin. Growth and phycoerythrin production conditions were optimized using a Plackett–Burman design and response surface methodology. An expression profile analysis of the cpeB gene, encoding the beta subunit of phycoerythrin, was performed by qRT-PCR under standard and optimized culture conditions. The optimization process showed that maximum cell abundance was achieved under the following conditions: CaCl2 = 2.1328 g/L, metal solution = 1 mL/L, pH = 7 and light intensity = 145 μmol photons/m2/s, whereas maximum phycoerythrin production level occurred when CaCl2 = 1.8467 g/L, metal solution = 1 mL/L, pH = 7 and light intensity = 157 μmol/m2/s. In agreement, positive transcriptional regulation of the cpeB gene was demonstrated using qRT-PCR. This study showed the successful optimization of abiotic conditions for highest growth and phycoerythrin production, making Rhodomonas sp. suitable for several biotechnological applications.

Seasonal and spatial distribution of microplastics in sediments by FTIR imaging throughout a continuum lake - lagoon- beach from the Tunisian coast

Plastics pollution in marine environment has become an issue of increasing scientific concern. This work aims to study the temporal and spatial distribution of plastics in sediments from three different Tunisian ecosystems; Rimel Beach, Bizerta lagoon and Ichkeul lake. Sediment sampling was conducted in surface (2 cm) and depth (15 cm) during spring, summer and winter. Plastics debris were separated by size fractions: macro (>5 mm), meso (1–5 mm) and microplastics (<1 mm) to optimize the time necessary for their characterisation. Macroplastics and mesoplastics were identified using an IR Attenuated total reflectance (ATR) and microplastics with Imaging Fourier transform infrared spectroscopy (FTIR) spectroscopy after an optimized extraction protocol. Results indicate that, the lowest contamination degree with macroplastics was recorded in Ichkeul lake, 2 macro debris/m2 (marine protected area, national parc of Ichkeul). Mesoparticles were only detected in lagoon of Bizerte in large quantities (4900 item/kg of sediment in surface and 680 item/kg of sediment in depth) and were identified principally as paint products. For microplastics, the repartition was quite homogeneous between the three sites with an average abundance was 130.55 ± 65.61 items/kg for all seasons. The variations of microplastics abundances on the three sites could not be clearly related to the seasons. Whereas the polymer characterisation in the surface and depth sediments of the three studied areas were principally due to eight types of polymers (PVC, PET, PP, PE PS, Polyamide (PA) and polymeric methyl methacrylate (PMMA)) as reported in many other studies, surprisingly all MPs recovered in the study were smaller than 300 μm, >70 % being fragments. This study brings new results as regards to the state of plastic contamination in Tunisian coast and shows the importance of investigating different ecosystems in such studies.

DNA barcoding of commercially relevant marine fish species in Tunisian waters

AbstractDNA barcoding based on the cytochrome c oxidase subunit I (COI) gene in mitochondrial DNA has been adopted as a global biological identification system for animals due to its accuracy compared with other classical taxonomic methods. The objective of this study was to establish a reference library with generated barcodes. A total of 84 fish specimens belonging to 37 commercially important marine fish species, representing five orders, 14 families and 30 genera, were sampled along the Tunisian coast and barcoded for the first time, obtaining 637 bp sequences. The average Kimura 2-parameter (K2P) distances within species, genera and families were 0.52, 6.86 and 14.60%, respectively. The Maximum likelihood (ML) tree revealed distinct clusters in concurrence with the taxonomic status of the species. Our results confirmed the authentication of the barcode approach for the identification of the species examined and provide valuable information that would help ichthyologists to achieve better monitoring, conservation and management of fisheries in Tunisia.

The Sea Slug Doriopsilla areolata Bergh, 1880 (Mollusca, Gastropoda) in the Mediterranean Sea: Another Case of Cryptic Diversity

The Mediterranean Sea diversity is still far from being fully disclosed. Marine Heterobranchia are one of the most paradigmatic species-rich groups, with many recent systematic studies revealing the high density of new, cryptic, and endemic species occurring in the Mediterranean basin. In this study, sea slug Doriopsilla areolata, which was considered until today one of the most widespread nudibranchs worldwide, was investigated using a molecular approach to compare Mediterranean and Atlantic populations for the first time. The molecular analyses involved three different molecular markers, the two mitochondrial COI and 16S, and the nuclear H3 gene. The results revealed a complex of species within D. areolata that indeed consists of three potentially species, two of which are endemic to the Mediterranean Sea: Doriopsilla areolata, which is distributed in the Adriatic Sea (the type locality of the former species), D. rarispinosa, which occurs in the Western Mediterranean basin and along the Tunisian coast, and one additional Atlantic species here provisionally defined as Doriopsilla sp. 1. This study helps to unveil another case of cryptic diversity within Mediterranean Heterobranchia and to increase the knowledge on Doriopsilla genus diversity.

First record of Luidia atlantidea Madsen, 1950 (Echinodermata: Asteroidea: Paxillosida: Luidiidae) in the Sidi-Medjdoub areaMostaganem (West Algerian coast, Mediterranean Sea).

The genus Luidia is currently represented in the Mediterranean Sea by three species, namely Luidia ciliaris (Philippi, 1837), Luidia sarsii sarsii (Dben Koren in Dben, 1844) and Luidia atlantidea (Madsen, 1950) which is an Atlantic species recently reported from the Spanish and Tunisian coasts. Two individuals of Luidia atlantidea were collected as bycatch from small-scale fisheries in the region of Sidi-Medjdoub (Mostaganem, Algeria) at a depth of 53 m. The detailed study of the morphological and anatomical characters allowed us to formally identify the two individuals of Luidia atlantidea and therefore to report it for the first time in the Algerian West coast.

Echinocephalus caniculus n. sp. (Nematoda: Gnathostomatidae Railliet, 1895) from the lesser spotted dogfish Scyliorhinus canicula (L.) (Elasmobranchii: Scyliorhinidae Gill, 1862) off Tunisia, with a key to species of the genus Echinocephalus

Echinocephalus caniculusn. sp. (Nematoda, Gnathostomatidae Railliet, 1895) was isolated from the spiral valve of the lesser spotted dogfish Scyliorhinus canicula (L.) from the waters off Kalaat El Andalous, North East Tunisia. This new species is mainly characterized by a cephalic bulb armed with 31–39 transverse rows of uncinated hooks, a comparatively long oesophagus, short spicules and the presence of a gubernaculum. The new species differs from its congeners by having four cervical sacs of almost equal length, a higher oesophagus/body length ratio, the arrangement of the caudal papillae, the absence of a medioventral preanal organ and numerous scattered `pores´ limited to the lateral side of the posterior part of the body. This is the first report of a member of the genus Echinocephalus Molin, 1858 from the Tunisian coast, and a new host and locality record for the Gnathostomatidae. A key to the species of Echinocephalus is provided.

The survey of ectoparasites on two species of Triakids (Mustelus mustelus and M. punctulatus) sharks from Tunisian coasts

Between 2018 and 2020, 696 fish belonging to two species of sharks from the Family Triakidae (Mustelus mustelus and M. punctulatus) were collected from the coasts of Tunisia and inspected for parasites. Six copepod taxa (Perissopus dentatus Steenstrup & Lütken, 1861, Eudactylinella alba Wilson, 1932, Kroyeria lineata Van Beneden, 1853, Nesippus orientalis Heller, 1865 and Lernaeopoda galei Krøyer, 1837, Kroyeria sp.), four isopod species (Anilocra physodes (Linnaeus, 1758), Emetha audouini (H. Milne Edwards, 1840), Ceratothoa parallela (Otto, 1828) and Ceratothoa oestroides (Risso, 1816)) and two monogenean species (Erpocotyle sp1. And Erpocotyle sp2) were collected. A large number of global host records was reported, including the occurrence of E. audouini on M. mustelus and of Erpocotyle sp.2 on M. punctulatus. The study of the diversity of parasites per host species revealed that M. mustelus had a higher parasitic richness compared to M. punctulatus. In this study, it was provided for the first records on ectoparasites on Triakidae sharks from Tunisian coasts and their infection indices.

Occurrence and antibiotic resistance of Vibrio parahaemolyticus isolated from the Tunisian coastal seawater.

Vibrio parahaemolyticus is a gram-negative bacterium ubiquitous in seawater or estuarine water throughout the world. It is a major cause of seafood gastroenteritis complications. In this study, the presence of V. parahaemolyticus was investigated in 66 seawater samples collected during 2018 from 15 stations spread along the Tunisian coast using selective media including CHROMagar Vibrio media. The results show that only eight samples contained V. parahaemolyticus. However, while Vibrio alginolyticus was detected in all samples; both Vibrio cholerae and Vibrio vulnificus were not found. Nine of the presumed V. parahaemolyticus colonies were purified on tryptic soy agar from eight positive samples then identified by the API 20E biochemical test and confirmed by the presence of a specific target toxR gene. The detection of virulence genes, thermostable direct haemolysin (tdh) and thermostable-related haemolysin (trh), by the polymerase chain reaction (PCR) showed the presence of only two trh-positive isolates. The assessment of antibiotic susceptibility of the V. parahaemolyticus isolated revealed a complete resistance to colistin, amikacin, penicillin and cefotaxime and a total sensitivity to chloramphenicol, nitrofurantoin and sulfamethoxazole-trimethoprim with a multiple antibiotic resistance index (MAR) ranging from 0.4 to 0.5.

The Mediterranean limpet Patella caerulea (Gastropoda, Mollusca) to assess marine ecotoxicological risk: a case study of Tunisian coasts contaminated by metals.

Participants in the coastal socio-economy of the Mediterranean Sea, such as industries, aquaculture, urban populations, conglomerates, and tourists, create intense anthropogenic pressures on marine ecosystems (such as the release of trace metals). This raises concerns about their impact on the surrounding environment and on marine organisms, including those collected for human consumption. This study introduces the possibility of using Patella caerulea (Linnaeus 1758), indigenous to the Mediterranean Sea, as a biosentinel of marine pollution. This study proposes coupling environmental (bioaccumulation) and toxicological (redox homeostasis) measures of bioavailability with genetic variability (COI mtDNA) assessments. Concentrations of six trace metals (cadmium, copper, iron, lead, nickel, and zinc) were measured in surface seawater and in P. caerulea individuals collected from four coastal stations on the Tunisian coast where different levels of metal contamination have occurred. The quantified biomarkers involved the determination of antioxidant defense enzymes, catalase (CAT), glutathione peroxidase (GPX), superoxide dismutase (SOD), and the measurement of lipid peroxidation indicated by malondialdehyde (MDA) levels. Our study identified critical levels of metal contamination among locations in the Gulf of Gabes. Concomitantly, the induction of antioxidant biomarkers (especially SOD and GPX) was observed, highlighting the potential of P. caerulea to acclimate to stressful pollution conditions. Molecular analysis of COI (mtDNA) revealed low discrimination between the four P. caerulea populations, highlighting the role of marine currents in the Mediterranean Sea in the dispersal and passive transportation of limpet larvae, allowing an exchange of individuals among physically separated, P. caerulea populations.

Reproductive biology of the blue swimming crab Portunus segnis (Forskål, 1775) (Brachyura: Portunidae) in the Gulf of Gabes (southeastern Tunisia, central Mediterranean Sea)

The blue swimming crab Portunus segnis (Forskål, 1775) (family Portunidae) is one of the earliest Lessepsian invaders of the Mediterranean Sea and has been recorded for several decades in various Mediterranean areas. However, its presence on the southeastern Tunisian coast is very recent. This study describes the reproductive biology of the species in the Gulf of Gabes, including sex ratio, ovarian maturation, size at sexual maturity, spawning season and fecundity. Samples for biological investigation were collected from the commercial catches of trawlers and artisanal fishing units, from January to December in 2018. A total of 2 762 specimens, ranging from 19 to 158 mm carapace width (CW) and 0.638 to 356.109 g body weight (BW), were analysed. Females outnumbered males by 1.3 to 1 (1 581 vs 1 181 individuals). Sexual maturity was classified into five stages for females and three stages for males, based on visual observation of the colour and shape of the gonads. Spawning occurred three times during the year, with the first peak in May, the second in July, and the third—the most intensive peak—in October–November. Size at sexual maturity was 93.1 mm CW for males, and 93.6 mm CW for females. Females carried 142 242–2 640 080 eggs on their abdomen, with a positive linear relationship between fecundity and CW. The data presented in this study should be useful not only to detect variations in the reproductive cycle of P. segnis between regions but also to ensure sustainable management of the new fishery for the species in Tunisian waters.

First insight of genetic diversity, phylogeographic relationships, and population structure of marine sponge Chondrosia reniformis from the eastern and western Mediterranean coasts of Tunisia.

Despite the strategic localization of Tunisia in the Mediterranean Sea, no phylogeographic study on sponges has been investigated along its shores. The demosponge Chondrosia reniformis, descript only morphologically along Tunisian coasts, was chosen to estimate the influence of natural oceanographic and biogeographic barriers on its genetic differentiation and its Phylogeography. The cytochrome oxidase subunit I (COI) gene was amplified and analyzed for 70 Mediterranean Chondrosia reniformis, collected from eight localities in Tunisia. Polymorphism results revealed high values of haplotype diversity (H d) and very low nucleotide diversity (π). Thus, these results suggest that our sponge populations of C. reniformis may have undergone a bottleneck followed by rapid demographic expansion. This suggestion is strongly confirmed by the results of neutrality tests and “mismatch distribution.” The important number of haplotypes between localities and the high genetic differentiation (F st ranged from 0.590 to 0.788) of the current C. reniformis populations could be maintained by the limited gene flow Nm (0.10–0.18). Both haplotype Network and the biogeographic analysis showed a structured distribution according to the geographic origin. C. reniformis populations are subdivided into two major clades: Western and Eastern Mediterranean. This pattern seems to be associated with the well‐known discontinuous biogeographic area: the Siculo‐Tunisian Strait, which separates two water bodies circulating with different hydrological, physical, and chemical characteristics. The short dispersal of pelagic larvae of C. reniformis and the marine bio‐geographic barrier created high differentiation among populations. Additionally, it is noteworthy to mention that the “Mahres/Kerkennah” group diverged from Eastern groups in a single sub‐clade. This result was expected, the region Mahres/Kerkennah, presented a particular marine environment.

Impact of a sea breeze event on geochemical behavior of aerosols at a Mediterranean coast (Northern Tunisia)

The aim of this study is to identify the impact of a sea-land breeze circulation on the ventilation of air masses over the Mediterranean Tunisian coast (Boukornine area) during the summer period. Our results show the Mediterranean Sea has an important effect on the chemical characteristics of atmospheric aerosols by the advection of particles from the sea to the coastal site. Indeed, the daytime sea breeze as well the nighttime land breeze limit the ventilation of air masses by the redistribution of aerosols. Besides, it was found that higher concentrations of sodium, chlorine and sulfur over the examined area are associated with the sea-land breeze recirculation while the crustal constituents stay practically constant with some fluctuations due to local effect. The contribution of sea-breeze in Boukornine area was more important than those recorded in other sites in Tunisia. This study proves the high influence of topography which increases the effect of sea-breeze.

Molecular signature of phylogenetic relationships and demographic history of Tunisian Mactra stultorum: Evidence from mitochondrial and nuclear DNA data

The genetic structure of Mactra stultorum is inferred from partial sequence of a mitochondrial cox1gene and of the internal transcribed spacer region ITS1. The samples with two colors of shell (white and brown) were collected from three sites belonging to the Tunisian coasts: Kalaât El Andalous (KA) and Soliman (SM) and Gabes (GM)). The phylogenetic trees obtained from the 2 markers are similar and subdivided samples into 3 distinct clades; clade (1) regrouped GM, clade (2) regrouped KS (KS contains samples from SM and KAa) and clade (3) is formed by KAb. Using the external sequences from genbank, it can be suggested that M. stultorum from the three clades KS, GM and KAb are three subspecies. The two sympatric M. stultorum from KA (KAa and KAb) appear to be genetically isolated showing a high genetic distance and no common haplotypes where the shell color serves for segregating marker. A total of 29 and 18 haplotypes were detected in the examined cox1 and ITS1 regions, respectively. Our study revealed higher levels of genetic diversity for ITS1 compared to cox1. For both markers, significant clinal changes in haplotypes frequencies between the north and the south populations supported by the absence of common haplotypes were observed. The demographic history of M. stultorum populations has been assessed using neutral tests and mismatch distribution for cox1 marker. A unimodal curve of the Mismatch’s distribution and negative significant neutral tests suggested a recent sudden demographic expansion for GM.

Review article: Extreme marine events revealed by lagoonal sedimentary records in Ghar El Melh during the last 2500 years in the northeast of Tunisia

Abstract. The Tunisian coast has been affected in the past by many events of extreme marine submersion (storms and tsunamis). A high-resolution study along two sediment cores taken from the lagoon of Ghar El Meleh was performed to identify the different paleoextreme events and to reconstruct the paleoenvironmental changes in the northeastern part of Tunisia during the Late Holocene. A very high-resolution sedimentological analysis (granulometric and geochemical) was applied to these cores. These cores were also dated with isotopic techniques (137Cs, 210Pbex, 14C), and the outcomes reveal five phases of paleoenvironmental changes in this lagoonal complex and identify two sediment layers that are in connection with two major historical marine submersion events. The first layer is mentioned as E1 and seems to fit with the great tsunami of 365 cal CE. This event was marked by an increase in the coarse sediment, and it is correlated for the first time with the immersed city of Neapolis in the northern Gulf of Hammamet discovered in 2017 by the same tsunamis of 365 cal CE. The other sandy layer, referred to as E2, was dated from 1690 to 1760 cal CE and is marked by one specific sedimentological layer attributed to a marine submersion event. This layer could be associated with the 1693 tsunami event in southern Italy or an increase in extreme storm events.

Isopod assemblages in the Bizerte lagoon (SW Mediterranean Sea): composition, structure and environmental relationships

The spatial and temporal distribution, abundance, and structure of isopod assemblages in Bizerte Lagoon (SW Mediterranean Sea) were studied at 22 stations selected from seagrass and macroalgae sampled during four seasons in 2017. A total of 6808 individuals and 17 species of isopods belonging to 5 suborders, 7 families and 12 genera were identified. Six new species were recorded on Tunisian coasts. In addition, and compared to previous studies, nine isopod species were collected for the first time in this lagoon. Analysis of the trophic structure revealed that most stations are strongly dominated by herbivore-deposit feeders (78.3%), followed by deposit-suspension feeders (13.6%) and carnivores (8.01%). Three isopod assemblages were identified (G1, G2 and G3). The distribution of isopod assemblages is influenced by the nature and structure of the substrates. The seasonal variations in the isopod community patterns at 22 stations showed maximum abundance and diversity during spring, whereas the lowest ones were recorded during winter.

On the marine erosion of ancient archaeological remains of the Tunisian coasts et the risks of an acceleration of their degradation

Des recherches géoarchéologiques menées le long du littoral tunisien de 1987 à 1997, par une équipe pluridisciplinaire dont nous avons fait partie, avaient permis de faire des observations sur les sites côtiers d’âge antique. Il en ressort que ces derniers sont en majorité exposés à une érosion marine, parfois sévère.Un retour sur la situation, par un réexamen d’une partie des sites classés en cours d’érosion, montre une continuation du phénomène avec parfois des signes de son accélération. L’exploitation de documents de différentes dates, notamment des photos réalisées avec des angles de prise de vue comparables, et leur confrontation au terrain révèle des vitesses de retrait du rivage parfois rapides.Cette contribution est aussi l’occasion de donner une première évaluation d’un travail de protection qui vient d’être consacré à l’un des sites menacés. Elle attire l’attention sur les méfaits des travaux d’une ingénierie lourde non suffisamment avertie des contraintes du milieu d’intervention ou soucieuse de ses spécificités.

Evaluating the Performances of Interval Starting Accessibility Drying (ISAD) through Protein and Total Polyphenol Contents of Blue Crabmeat (Portunus segnis)

Blue crab (Portunus segnis) proliferation on Tunisian coasts started in 2014/2015. It has heavily impacted the balance of other species, local biodiversity, and fishing activity. Limiting these drawbacks may be achieved through ways promoting crabmeat. For this purpose, two different drying modes were tested: Conventional convective drying (CCD) and interval starting accessibility drying (ISAD) under 45 °C and relative humidity of 40%. Several air velocities were assayed under CCD: 1.5, 2.5, 3.5, and 5 m.s−1. Two different ISAD tests were run with different time-related conditions: drying period of 15 s and tempering period of 15 or 60 s. Drying modes and operating conditions performances were compared through proteins and total polyphenol contents (TPCs) evolution during the treatment. Important polyphenol and protein losses were observed between raw and processed crabmeat. Airflow velocities have a significant effect on crabmeat quality preservation. ISAD method under 15 s/60 s allowed the best preservation of these quality parameters. TPC and proteins losses and kinetics during drying under CCD or ISAD were modelled and correlations were established between the quality parameters, the residual water content at all drying times, and the evaporation rate.

Potential of three local marine microalgae from Tunisian coasts for cadmium, lead and chromium removals

Metal elements are widely used in various industrial activities and are considered as common water source contaminants. Thus, the development of cost-effective, simple design and efficient processes for trace metal elements removal from contaminated water sources is of great interest. The effects of cadmium, lead and chromium on growth, biomolecules accumulation and metabolic responses of Amphora coffaeiformis, Navicula salinicola and Dunaliella salina isolated from Tunisian coasts were tested. The bioremediation capacities of the three microalgae strains and the mechanisms involved in ions metal removal were also investigated. N. salinicola and D. salina seem to be better tolerating to Cr, while A. coffaeiformis and N. salinicola showed high resistance to Pb. The expression profile analyses by qRT-PCR of the antioxidant defense-related genes revealed that Cd, Pb and Cr treatments induce the up-regulation of catalase and superoxide dismutase coding genes for A. coffaeiformis and D. salina. Regarding N. salinicola, the catalase coding gene seems to be overexpressed after Cd, Pb and Cr exposure while only Cd and Cr induce superoxide dismutase gene overexpression. Moreover, the phytochelatin synthase (a metal chelator synthesis-related gene) was up-regulated in N. salinicola, A. coffaeiformis and D. salina after Cr exposure and also in A. coffaeiformis and D. salina after Cd exposure. While Pb treatments induce overexpression of phytochelatin synthase coding gene only for D. salina.Studied strains showed promising metal removal efficiencies for both Pb and Cr ions metals reached 95% for D. salina. Ion metal removal mechanisms study revealed that intracellular bioaccumulation process is used by D. salina for Cr up-taking. However, both intracellular and extracellular removal mechanisms are involved for Pb and Cr removal using A. coffaeiformis, N. salinicola and for Pb removal using D. salina. FTIR analysis demonstrated that several functional groups as carboxyl, hydroxyl, amino, phosphate and sulfate may participate in the bioadsorption process.

Assessment of trace element accumulation on the Tunisian coasts using biochemical biomarkers in Perinereis cultrifera

Our study aimed to evaluate the effect of trace element pollution in the polychaete Perinereis cultrifera (Grube, 1840) from two Tunisian coasts (the port of Rades, S1; and the Punic port of Carthage, S2). To this end, we used an approach based on proximate composition, biomarker responses and trace element bioaccumulation. Our results showed a decreasing order of metals concentrations (Zn&gt;Cu&gt;Cd&gt;Pb) in P. cultrifera from S1 and S2. The accumulation of Cd, Cu and Zn was significantly higher in S1 than in S2, especially in summer. Lipid, protein and glycogen content also changed significantly between S1 and S2 in relation to trace metal accumulation and environmental conditions. The results revealed a higher level of thiobarbituric acid in P. cultrifera from S1 than from S2. In addition, the enzymatic and non-enzymatic antioxidant defence system (catalase, glutathione-S-transferase, superoxide dismutase, glutathione and metallothionein) was enhanced and acetylcholinesterase activities decreased in P. cultrifera in S1 in comparison with S2. A principal component analysis showed that P. cultrifera from S1 exhibited a clear disruption of oxidative stress responses and trace element bioaccumulation among seasons. Overall, these findings revealed the sensitivity of those organisms to environmental conditions.