Multiple regression analysis to assess the role of plankton on the distribution and speciation of mercury in water of a contaminated lagoon.

Spatial and seasonal variation of mercury species aqueous concentrations and distributions was carried out during six sampling campaigns at four locations within Laranjo Bay, the most mercury-contaminated area of the Aveiro Lagoon (Portugal). Inorganic mercury (IHg(II)) and methylmercury (MeHg) were determined in filter-retained (IHg PART , MeHg PART ) and filtered (<0.45 μm) fractions (IHg(II) DISS , MeHg DISS ). The concentrations of IHg PART depended on site and on dilution with downstream particles. Similar processes were evidenced for MeHg PART , however, its concentrations increased for particles rich in phaeophytin (Pha). The concentrations of MeHg DISS , and especially those of IHg(II) DISS , increased with Pha concentrations in the water. Multiple regression models are able to depict MeHg PART , IHg(II) DISS and MeHg DISS concentrations with salinity and Pha concentrations exhibiting additive statistical effects and allowing separation of possible addition and removal processes. A link between phytoplankton/algae and consumers’ grazing pressure in the contaminated area can be involved to increase concentrations of IHg(II) DISS and MeHg PART . These processes could lead to suspended particles enriched with MeHg and to the enhancement of IHg(II) and MeHg availability in surface waters and higher transfer to the food web. [ABSTRACT FROM AUTHOR]