Mercury concentrations in Antarctic zooplankton with a focus on the krill species, Euphausia superba

Mercury dynamics at the base of the pelagic food web of the Gulf of Gdańsk, southern Baltic Sea

Planktonic organisms, which have direct contact with water, serve as the entry point for mercury (Hg), into the marine food web, impacting its levels in higher organisms, including fish, mammals, and humans who consume seafood. This study provides insights into the distribution and behavior of Hg within the Baltic Sea, specifically the Gulf of Gdańsk, focusing on pelagic primary producers and consumers. Phytoplankton Hg levels were primarily influenced by its concentrations in water, while Hg concentrations in zooplankton resulted from dietary exposure through suspended particulate matter and phytoplankton consumption. Hg uptake by planktonic organisms, particularly phytoplankton, was highly efficient, with Hg concentrations four orders of magnitude higher than those in the surrounding water. However, unlike biomagnification of Hg between SPM and zooplankton, biomagnification between zooplankton and phytoplankton was not apparent, likely due to the low trophic position and small size of primary consumers, high Hg elimination rates, and limited absorption.

Interspecific Variations in the Internal Mercury Isotope Dynamics of Antarctic Penguins: Implications for Biomonitoring

Mercury (Hg) biomonitoring requires a precise understanding of the internal processes contributing to disparities between the Hg sources in the environment and the Hg measured in the biota. In this study, we investigated the use of Hg stable isotopes to trace Hg accumulation in Adélie and emperor penguin chicks from four breeding colonies in Antarctica. Interspecific variation of Δ199Hg in penguin chicks reflects the distinct foraging habitats and Hg exposures in adults. Chicks at breeding sites where adult penguins predominantly consumed mesopelagic prey showed relatively lower Δ199Hg values than chicks that were primarily fed epipelagic krill. Substantial δ202Hg variations in chick tissues were observed in both species (Adélie: -0.11 to 1.13‰, emperor: -0.27 to 1.15‰), whereas only emperor penguins exhibited the lowest δ202Hg in the liver and the highest in the feathers. Our results indicate that tissue-specific δ202Hg variations and their positive correlations with % MeHg resulted from MeHg demethylation in the liver and kidneys of emperor penguin chicks, whereas Adélie penguin chicks showed different internal responses depending on their exposure to dietary MeHg. This study highlights the importance of considering intra- and interspecific variations in adult foraging ecology and MeHg demethylation when selecting penguin chicks for Hg biomonitoring.

The non-selective Antarctic filter feeder Salpa thompsoni as a bioindicator of mercury origin

Hg is considered as the most toxic metal in the environment. Sources of Hg in the environment include burning fossil fuels, burning waste, and forest fires. The long residence time of the gaseous form in the atmosphere allows mercury to be transported over long distances. The pelagic tunicate Salpa thompsoni is an important component of the Antarctic environment. Over the past few decades an expansion of this species to the higher latitudes has been noted, mainly due to the ongoing climate change. The study material consisted of samples of S. thompsoni individuals, collected in the waters surrounding Elephant Island (Western Antarctic). Total mercury and five of its fractions were determined. Whole organisms were analyzed as well as internal organs: stomachs, muscle strips, and tunics. Obtained results showed that the highest concentrations of mercury in salps were observed in stomachs. With the Hg fraction results, it can be concluded that the main route of exposure of S. thompsoni to Hg is presumably absorption from the food-filtered organic and non-organic particles. Moreover, the process of transformation of simple soluble forms into organic forms of Hg in stomachs and intestines and its distribution to other tissues was observed.