Spatial and Seasonal Distribution of Heavy Metal Pollution in Tropical Lagoon off the Gulf Of Guinea

The consistency of the aquatic environment at any point reflects basin lithology, anthropogenic input and climatic conditions. Spatial and seasonal distribution of heavy metal pollution in tropical Lagoon off the Gulf of Guinea was investigated between November, 2018 to October, 2019. Water samples were collected bi-monthly for heavy metal analysis and physicochemical parameters were measured in-situ every month. Results for physicochemical parameters were presumed to be ideal for marine life for both seasons as prescribed by the Federal Ministry of Environment. Salinity showed a significant negative correlation with temperature and a significant positive correlation with electrical conductivity (EC) during wet season. During the dry season, temperature showed a significant positive correlation with pH. As the temperature rises, molecular vibrations increase which results in the ability of water to ionize and form hydrogen ions and resulted into pH drop. The trend of heavy metal concentrations in the entire study area during the wet and dry season were in the order: Pb>Cu>Zn=Cr>Cd and Cu>Cr>Zn=Cd>Pb respectively. Nemerow’s Pollution Index (NPI) and Contamination Index (CI) were further used to evaluate pollution status of each metal in each sample station and contamination status of the entire sample stations respectively. The CI of the study area showed a decreasing order: Apapa > Iddo > Makoko > Ibeshe > Egbin and Ibeshe > Makoko > Iddo > Apapa > Egbin for wet and dry seasons respectively. Keyword: tropical Lagoon, Gulf of Guinea, Physicochemical, heavy metal, Nemerow’s Pollution Index, Contamination Index

Cyclical Patterns and a Regime Shift in the Character of Phytoplankton Blooms in a Restricted Sub-Tropical Lagoon, Indian River Lagoon, Florida, United States

This paper examines the character of phytoplankton blooms in a restricted sub-tropical lagoon along the Atlantic coast of central Florida. The results of the 23-year study (1997–2020) provide evidence for multiple types of variability in bloom activity, including cyclical patterns, stochastic events, and most prominently a regime shift in composition and intensity. Cyclical patterns (e.g., El Niño/La Niña periods) and stochastic events (e.g., tropical storms) influenced rainfall levels, which in turn impacted nutrient concentrations in the water column and the timing and intensity of blooms. In 2011, a major change occurred in the character of blooms, with a dramatic increase in peak biomass levels of blooms and the appearance of new dominant taxa, including the brown tide species Aureoumbra lagunensis and other nanoplanktonic species. Results of quantitative analyses reveal system behavior indicative of a regime shift. The shift coincided with widespread losses of seagrass community and reduced drift algae biomass. A combination of exceptionally low water temperatures in the winters of 2009/2010 and 2010/2011, hypersaline conditions associated with drought conditions, and high light attenuation caused by blooms appear to have contributed to the widespread and protracted decline in seagrass and drift macroalgal communities in the lagoon, leading to shifts in distribution of internal and external nutrient sources toward phytoplankton.