Ologe Lagoon is one of Lagos, Nigeria’s five major lagoons, which provide essential ecosystem services such as agriculture, fishing, transportation, salt and sand mining, tourism, and industrial development. There are concerns, however, that the lagoon’s water may not be safe for the ecosystem functions it offers. As a result, the physicochemical properties, heavy metal concentrations, and microbial loads of water samples from the lagoon, as well as their health risks, were examined in this study. Physicochemical analysis showed that calcium, chloride, nitrates, sulphate, dissolved oxygen, acidity, alkalinity, total dissolved solid, and total suspended solid were present within the World Health Organization permissible limits, but not so for phosphate and temperature. The heavy metal analysis revealed that the water had non-permissible levels of iron, cadmium, chromium, nickel, manganese, and copper, but lead was normal. The microbiological examination showed abnormal bacteria counts, while coliform and fungus were not detected. The average daily oral and dermal exposure to cadmium, chromium, and nickel were higher than the recommended daily intake, but iron, lead, and copper were within the limits. The hazard quotient of oral and dermal exposure to cadmium, dermal exposure to chromium, and oral exposure to manganese were higher than the recommended limit (> 1). The carcinogenic risks of Cd, Cr, and Ni were also greater than the acceptable limit. The results obtained indicate that Ologe Lagoon’s water is unsafe for the lagoon’s ecosystem functions. Relevant agencies should ensure that waste is treated before being discharged into the lagoon.

The paper provides data on spatial distribution of petroleum hydrocarbons, heterotrophic and hydrocarbon-oxidizing bacteria in water and bottom sediments as well as on heavy metals in bottom sediments at different sites in the zone of fresh and saline water mixing, with the salinity range 1–18 ‰ during spring low water and high water. Physical and chemical characteristics of the bottom sediments are given. The highest hydrocarbon-oxidizing bacteria percentage of the heterotrophic bacterioplankton count in the indicated areas was found in April, with the maximum of 55 % determined in the transition zone waters. The share of hydrocarbon-oxidizing bacteria in the heterotrophic bacteria abundance in the water was larger than that in the bottom sediments. The highest concentrations of chloroform-extractable substances and petroleum hydrocarbons were detected in the marine zone bottom sediments, and their lowest concentrations were found in the river zone. During the period under study, the petroleum hydrocarbon input (in almost equal volumes) was constant, which is indicated by the hydrocarbon percentage of chloroform-extractable substances, which on average was 31 % for the marine zone, 29 % for the transitional zone, and 32 % for the river zone. In contrast to the river and transition zones, the concentration of chloroform-extractable substances observed in the marine zone bottom sediments was constant.

Comparative analysis of microbiological indicators (heterotrophic and hydrocarbon-oxidizing bacteria) in bottom sediments and biochemical parameters (level of oxidized proteins (OP) and lipid peroxidation (LPO), superoxide dismutase (SOD), catalase (CAT), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) activities) in hepatopancreas of mussel Mytilus galloprovincialis (Lam.) from three Sevastopol bays - Laspi, Kazach’ya, Streletskaya (the Black Sea) was carried out. The results obtained allowed to identify certain differences between the studied areas and characterize their ecological state. The maximum abundance of heterotrophic and hydrocarbon-oxidizing bacteria was found in the most polluted Streletskaya Bay (95,000 and 250 cells/g respectively), the minimum - in the conventionally pure Laspi Bay (2,500 and 1.5 cells/g respectively). Parameters of prooxidant-antioxidant system (level of OP and LPO, SOD and CAT activities), as well as ALT activity in the hepatopancreas of mussels from Streletskaya Bay were found higher as compared to those in other tested areas. Most significant differences (more than twofold) in SOD activity, LPO content and basic ketone forms of OP levels were found between Laspi and Streletskaya bays. The results obtained indicate the severe pollution and less favorable living conditions for aquatic organisms in Streletskaya Bay, as well as demonstrate the high level of biochemical adaptation of mussels to complex environmental pollution. The studied parameters can be applied in the ecological monitoring of the coastal sea water areas.