Water Quality Status Within The Anchorage Space of Tema Harbour, Ghana

Abstract

Marine pollution is attributable to anthropogenic introductions of contaminants above their natural background levels and being dispersed by ocean forcing. Assemblages of vessels within offshore platforms and seaport terminals could also be potential sources for marine water contamination. As such, nearshore perimeters of the Tema Port were assessed to review the vessel register and the seawater quality through Automatic Identification System (AIS), in-situ and laboratory analysis. The results of analysed satellite data suggested ~1,600 commercial vessels of over 50 flag states including Ghana were present in the West Africa territorial waters between 2016 and 2020. Bacterial load shows the following order: total heterotrophic bacterial [THB] (364-468 cfu/mL) > total coliform [TC] (26-73 cfu/100 mL) > faecal coliform [FC] (1-13 cfu/100 mL). Phytoplankton species abundances were in order Ceratium spp. (31.8%) >Protoperidinium spp. (30.1%) > Dinophysis spp. (9.3%) > Coscinodiscus sp. (7.3%) > Lingulodinium polyedra (6.9%) = Nitzschia sp. (6.9%). Water temperature ranged between 23.9 and 27.5 ^oC (surface to 25.4 m depth), salinity 36.03 ± 0.51‰, dissolved oxygen 6.54 ± 0.94 mg/L and pH 8.18 ± 0. 06. Phosphate, ammonia, Cd, As, and Pb levels were low (0.01 to 0.153 mg/L). Nitrate, silicate and Mg were relatively high (0.7 - 2.18 mg/L). Pearson correlation coefficient displayed 0.05 and 0.01 significant levels between total dissolved solids (TDS) and electrical conductivity and salinity, and dissolved oxygen and temperature and arsenic levels. Normalization physicochemical data suggested thermal stratification at 15 m depth. Nutrient and biological results indicated normal water quality conditions, however, relatively high levels of phytoplankton including harmful and toxic species suggested excess nutrient contamination in the study area. Further assessment is recommended to ascertain the link between phytoplankton and nutrient load at the anchorage space.