Cheminių elementų bioakumuliacija Baltijos ir Arkties regionų jūros paukščių plunksnose

Vis dažniau susiduriama su sunkiųjų metalų ir kitų elementų tarša ne tik aplinkoje, bet ir gyvuosiuose organizmuose. Kadangi paukščių plunksnos gali būti kaip bioindikatoriai taršai tirti, šiame tyrime pasirinktos trys paukščių rūšys, kurių plunksnose buvo tiriamos sukauptos sunkiųjų metalų ir kitų elementų koncentracijos, taip įvertinant ir elementų bioakumuliaciją skirtingose buveinėse ir regionuose. Tyrimui pasirinktų vandens paukščių rūšių – ledinės anties, rudakaklio naro ir didžiojo kormorano – maitinimosi ir gyvenamosios teritorijos yra skirtingose geografiniuose regionuose. Ledinių ančių ir rudakaklių narų jaunikliai maitinasi Arkties regione, o didžiųjų kormoranų jaunikliai – Baltijos regione. Šio tyrimo tikslas buvo nustatyti ir palyginti skirtinguose regionuose besimaitinusių jūros paukščių plunksnų sunkiųjų metalų koncentracijas, taip įvertinant ir regionų užterštumą. Tyrimui surinkti plunksnų mėginiai iš 81 individo. Plunksnų mėginiai buvo apdoroti azoto rūgštimi ir vandenilio peroksidu, ir išmatuoti su indukuotai sužadintos plazmos spektrometru (ICP-MS). Rezultatai parodė, jog Baltijos regiono jūroje ir Kuršių mariose besimaitinančių didžiųjų kormoranų jauniklių plunksnos statistiškai reikšmingai skirėsi pagal Ar, Se ir Mn koncentracijas. Baltijos jūros kolonijos kormoranų plunksnose nustatyta didesnė elementų įvairovė. Analizuojant Arkties regiono paukščius, rudakaklių narų plunksnose buvo nustatytos aukštesnės Pb, Zn, Ni ir Hg koncentracijos negu ledinių ančių jauniklių plunksnose; taip pat aukštesnės δ 15N vertės rudakaklių narų plunksnose reprezentavo aukštesnį mitybinį lygmenį lyginant su ledinėmis antimis. Analizuojant sukauptas elementų koncentracijas pagal amžių ir lytį, ledinių ančių plunksnos nustatytas didžiausias skirtumas tarp patinų ir jauniklių. Lyginant taršą sunkiaisiais metalais pagal regioną, nustatyta jog didžiausia elementų įvairovė ir aukštesnės koncentracijos nustatytos Arkties regione, tai galėjo lemti skirtingos šių paukščių maitinimosi buveinės.

The growing pollution of heavy metals in the environment and living organisms is a matter of great concern. This particular study analyses the concentration of heavy metals and other elements accumulated in the feathers of three seabird species. Three species of seabird juveniles were selected for the study: long-tailed duck, red-throated diver, and great cormorant. These species feed and grow feathers in different regions and habitats. Both long-tailed ducks and red-throated divers breed in the Arctic, however, these birds have different feeding behaviour and habitats. Long-tailed ducks breed in freshwater lakes and feed on local benthic organisms and fish, whilst red-throated divers, breeding on freshwater lakes too, feed on the fish brought from the sea. The third species, great cormorant, from different colonies in the Baltic Sea region, in which birds feed in different bodies of water, were also selected for the study. The first colony from Nemunas Delta Regional Park feeds on fish from the Curonian Lagoon and the second from Seaside Regional Park colony forage in the Baltic Sea. By knowing where the juveniles of these birds grew and fed we analysed their feathers and can determine how much heavy metals and other elements these birds have accumulated. Therefore, the concentrations of heavy metals accumulated in the bodies of the birds may reflect the pollution in the environment, so by examining the bird feather we can compare levels of pollution between their feeding habitats. Feathers were selected for the study because of their easy retrieval without causing harm to the bird, and the known growing location. Feather samples of young cormorants were collected in the summer (June-July, 2021) in collaboration with the Ventės ragas Ornithological Station. The second part of the samples (representing the Arctic region) was collected from long tailed ducks and red- throated divers from bycatch in their wintering site in the Lithuanian Baltic Sea coastal waters. A total sample of feathers collected was from 81 individuals. The feather samples are first washed with distilled water, Milli Q water, acetone and again with Milli Q water to remove any environmental contamination. Feather samples are then crushed and dried in ceramic crucibles to prevent contamination from other metals in the environment. They are dried in a muffle for 12 hours at a temperature of 60 °C to constant weight. A sample of the weighted feathers is added to the mineralization flask and 5 ml of nitric acid and 2 ml of hydrogen peroxide are added, mineralized in a mineralizer and diluted in 50 ml PFA volumetric flasks with Milli Q water. A 200 μg/l gold stabilizer for mercury was added to each sample. After sample preparation measurements are performed with an inductively coupled plasma mass spectrometry (ICP-MS). Reference material (European Reference Material ERM®-CE278k) was used to ensure the quality of the analysis of samples. The results showed that the highest concentrations of Zn and Fe were found in the feathers of cormorants in the Baltic Sea region. A statistically significant difference was found in the concentrations of Ar, Se and Mn (p <0,05, Mann and Whitney U-test). In the Arctic region the feathers of long-tailed duck and red-throated divers had the highest concentrations of Zn and Fe. There was a statistically significant difference in Zn concentration, higher accumulated Zn concentration in redthroated divers than in long-tailed ducks (99,46 ± 10,15 mg·kg-1 and 90,59 ± 13,98 mg·kg-1; p <0,05, Mann and Whitney U-test). Statistical differences between bird species were also found in Hg, Ni and Pb concentrations and were higher in red-throated divers. Comparison of heavy metals and other elements accumulated in long-tailed duck feathers by age and sex of individuals showed that the most statistically significant differences were found between juveniles and males (p <0,05, Dunn's test). Concentrations of Cr, Cu, Fe, Mn, Ni, Pb, Zn and Se accumulated in feathers of male and young long-tailed ducks differed statistically significantly, except for Hg and As. The highest metals and other elements concentrations and δ15N values were found in long-tailed duck male feathers and the lowest in juvenile feathers. In the Arctic region, both freshwater and marine ecosystems have higher concentrations of heavy metals and other elements than in the Baltic Sea region, except for Se and Hg. Hg was found to be higher in the Curonian Lagoon, while Se - in the Baltic Sea. The bird feathers most certainly can reflect the heavy metals and other elements in the environment and to that extent it is important to carry out research and monitor the pollution of chemicals in the environment and in living organisms. It seems the feathers of birds can be used as an indicator in the study of heavy metal and other elements contamination, as the results show that concentrations of heavy metals and other elements vary from region to region.