The variability of Hg concentration and composition of marine phytoplankton

Abstract

Mercury is a toxic element. It undergoes biomagnification in the marine trophic chain, which is why it is significant to identify the factors influencing its bioaccumulation on the first level of the trophic chain. At present, the input of heavy metals to the southern Baltic is being reduced. On the other hand, the parameters influencing mercury remobilisation in the environment are a subject to a long-time trend associated with climate changes. Examples include growing number of heavy rain events causing surges or floods, and increased frequency of storm winds leading to increased coastal erosion as well as overall temperature increase. The present studies were carried out in the coastal zone of the Gulf of Gdańsk (southern Baltic) for 18 months at two stations (Chałupy and Osłonino) located in the Puck Lagoon, and for 12 months in Gdynia. Climate changes influence the abundance and species composition of phytoplankton, which in consequence has an effect on Hg accumulation and magnification in the trophic chain, and in the human body as a result. Extreme phenomena such as land erosion or floods resulted in an additional inflow of nutrients, but also toxic substances, into the coastal zone. The bioconcentration factor (BCF) increased almost four times after abrasion of cliff. That was conducive to the growth of microflora, as well as increased Hg accumulation. The highest bioconcentration of Hg in phytoplankton was observed when the Mesodinium rubrum (spring and autumn) and Diatomophyceae (winter) prevailed in biomass. The BCF was then almost tenfold higher than during the rest of the year.

Mercury Cycling in the Gulf of Gdańsk (Southern Baltic Sea)

“…Due to the fact that mercury accumulates and biomagnifies in the marine trophic chain, aquatic organisms should also be considered as Hg reservoir. The median of the Hg concentration in phytoplankton in the coastal zone of the Gulf of Gdańsk was 51 ng g −1 [25]. The values depended both on the quantity and species composition of phytoplankton and on mercury sources in the Gulf [25,26].…”

“…The median of the Hg concentration in phytoplankton in the coastal zone of the Gulf of Gdańsk was 51 ng g −1 [25]. The values depended both on the quantity and species composition of phytoplankton and on mercury sources in the Gulf [25,26]. The mean phytoplankton biomass in the Gulf of Gdańsk was assumed to be 85 mg m −3 [26,45] and the volume of the water to a depth of 20 m (where phytoplankton occurs most abundantly) was 10.9 km 3 [4].…”

“…Information about Hg in marine organisms was obtained from the literature [25][26][27][28][29][30][31][32][33]. The Hg concentration in phytoplankton was measured by Bełdowska and Kobos between 2011 and 2013 [25,26]. Phytoplankton samples were collected with 20 μm nets and then stored at −20°C until analysis.…”

“…Samples were then stored at −20°C until analysis. Detailed information about sampling and storage methods can be found in the publications [25][26][27].…”

“…The amount of Hg bound to the phytoplankton was estimated by multiplying the median of the Hg concentration in phytoplankton in the coastal zone of the Gulf of Gdańsk [25] by the mean phytoplankton biomass in the Gulf [26,45] and the volume of the water to a depth of 20 meters (where phytoplankton occurs most abundantly).…”