Temporal and spatial variability of free-living nematodes in a beach system characterized by domestic and industrial impacts (Bandar Abbas, Persian Gulf, Iran)

Intertidal nematode assemblages along three beaches with different types of anthropogenic activity were collected in the northern part of the Persian Gulf, near Bandar Abbas (Iran). Forty-two genera of free-living nematodes belonging to 17 families were identified. Daptonema, Ptycholaimellus, and Promonhystera were the most abundant taxa in the area. The nematode assemblage structure was negatively affected by polychlorinated biphenyls (PCBs) and total organic matter (TOM), with an impact gradient from the polluted Power Plant (PP), over Khur Gursuzan (KG), to the cleaner 'Resalat' site (RE). The PP sites, characterized by industrial infrastructures, were mainly impacted by PCBs, while Khur Gursuzan (KG) is under the influence of domestic discharges, with high sedimentary TOM levels. However, PCBs and TOM seem closely associated and they likely lead to compounding effects on the fauna. Among the bioindicator genera found, Spirinia, Chromadorina, and Terschellingia may be recognized as resistant taxa to PCBs, while Daptonema, Sabateria, Promonhystera and Ptycholaimellus are opportunists able to exploit organic load, and Oncholaimus and Pomponema appeared sensitive genera being characteristic to unpolluted sediments. As expected, the spatial effects between the stations and concomitantly the different types of anthropogenic impacts played a much more important role than seasonal variability and related changes. This confirms that anthropogenic impact can be a major control factor at Persian Gulf beaches. Nematode female:male ratios were in favor of the females, especially in the sediments impacted by PCBs, corroborating the hypothesis that stressful conditions sustain the increasing female frequency in nematode populations. In terms of the ecological quality (EcoQ) status, genus percentages indicated lower EcoQ at PP and highest at RE. In contrast, Shannon-Wiener diversity (H') did not detect variations of EcoQ status at the three locations, while the Maturity Index did not indicate the presence of stressful conditions at PP, but it did at KG. It is possible that MI performs better when considering organic pollution compared to PCB contamination. However, we do not recommend its use in intertidal or transitional areas that are characterized by strong natural variations of the physical and chemical variables.