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Changes in accumulation of organic matter and stable carbon and nitrogen isotopes in sediments of two Slovenian mountain lakes (Lake Ledvica and Lake Planina), induced by eutrophication changes
Author(s) -
Vreca Polona,
Muri Gregor
Publication year - 2006
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.2006.51.1_part_2.0781
Subject(s) - eutrophication , isotopes of nitrogen , total organic carbon , sediment , trophic state index , environmental chemistry , δ13c , organic matter , sedimentary organic matter , environmental science , isotopes of carbon , trophic level , nitrogen , nitrate , lake ecosystem , dissolved organic carbon , denitrification , deposition (geology) , δ15n , biogeochemical cycle , stable isotope ratio , ecosystem , geology , ecology , nutrient , chemistry , geomorphology , biology , physics , organic chemistry , quantum mechanics
We measured accumulation rates of organic carbon (OC) and total nitrogen (TN) and stable carbon (δ 13 C org ) and nitrogen isotopes (δ 15 N) in the sediments of two mountain lakes (Lake Ledvica and Lake Planina, northwest Slovenia). Marked variations of these parameters were observed in both sediments. OC accumulation rates ranged from 4 to 23 g m −2 yr −1 in Lake Ledvica, whereas in Lake Planina they were one order of magnitude higher and increased substantially in the upper sediments. δ 13 C org and δ 15 N decreased upward in Lake Ledvica, from ‐25.5‰ to ‐28.4‰, and from +2.1‰ to ‐3.4‰, respectively. In contrast, substantial variations in the δ 13 C org profile, ranging from ‐30.9‰ to ‐37.4‰, but a quite uniform δ 15 N profile of approximately +1.8‰, was observed in Lake Planina. Elemental and isotopic changes of bulk sedimentary organic matter in the lakes were related to changes in the past trophic state of the lakes and their watersheds, inferred by natural development of the lake ecosystems, anthropogenic activities, as well as earthquakes and forest fires. Observed changes and differences in the δ 13 C org and δ 15 N records could be attributed to global changes in isotopic composition of atmospheric CO 2 and nitrate in atmospheric deposition, as well as to differences in organic matter, dissolved inorganic carbon, and dissolved inorganic nitrogen sources at various altitudes. Although Lakes Ledvica and Planina are remote mountain lakes, the sediment records showed severe eutrophication in Lake Planina, whereas in Lake Ledvica eutrophication is still moderate, thus reflecting a high sensitivity of these ecosystems to any external inputs.