Seasonal Variations in the Use of Profundal Habitat among Freshwater Fishes in Lake Norsjø, Southern Norway, and Subsequent Effects on Fish Mercury Concentrations

This study is based on monthly sampling of fish from grates mounted at an industrial water intake, located at a depth of 50 m in Lake Norsjø (Southern Norway) during the year 2014, to investigate seasonal variations in the use of the profundal habitat and subsequent variations in total Hg-concentrat...

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Bibliographic Details
Published in:Environments
Main Authors: Tom Robin Olk, Tobias Karlsson, Espen Lydersen, Asle Økelsrud
Format: Article in Journal/Newspaper
Language:English
Published: MDPI AG 2016
Subjects:
profundal habitat
Hg
Tot-Hg
stable isotopes
biomagnification
Salvelinus alpinus
Coregonus lavaretus
Osmerus eperlanus
Environmental technology. Sanitary engineering
TD1-1066
Norway
Online Access:https://doi.org/10.3390/environments3040029
https://doaj.org/article/1a8ec67e04334c5cb51af2802baa28bd
Description
Summary:This study is based on monthly sampling of fish from grates mounted at an industrial water intake, located at a depth of 50 m in Lake Norsjø (Southern Norway) during the year 2014, to investigate seasonal variations in the use of the profundal habitat and subsequent variations in total Hg-concentrations in profundal fish. Data on various fish present in a cold and dark hypolimnion of a large, deep, dimictic lake within the upper temperate zone of the Northern Hemisphere are rare. While predominant species such as A. charr (Salvelinus alpinus) and E. smelt (Osmerus eperlanus) were continuously present in this habitat, whitefish (Coregonus lavaretus) occupied this habitat primarily during wintertime, while other common species like brown trout (Salmo trutta), perch (Perca fluviatilis) and northern pike (Esox lucius) were almost absent. Besides stomach analyses (diet) and biometry, stable isotope analyses (δ15N and δ13C) and total mercury (Tot-Hg) analyses were carried out on the caught fish. The δ13C signature and stomach analyses revealed a combined profundal-pelagic diet for all three species, A. charr with the most profundal-based diet. Length was the strongest predictor for Hg in whitefish and A. charr, while age was the strongest explanatory variable for Hg in E. smelt. A. charr was the only species exhibiting seasonal variation in Hg, highest during winter and spring.

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