M. Søndergaard, Anders Nielsen, L. Johansson, T. Davidson
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引用次数: 0
Abstract
ABSTRACT Lakes that undergo temporary stratification in summer do not fit into the classic categorisation of polymictic or dimictic lakes, but how common are they and what are the effects of stratification on the development of anoxia? We used monthly and bimonthly (twice per month) temperature and oxygen profile data from 436 Danish lakes (area range 1–3954 ha, maximum depth range 1.3–45 m) and defined a stratification indicator based on the temperature difference between the upper and lower 2 m of the water column. The stratification indicator had values between −1.6 and 17.7 °C and was significantly and strongly related to lake maximum depth and significantly but less strongly related to lake area. The indicator was highly variable, especially in lakes with maximum depths between 4 and 10 m, where intermediate indicator values suggest one or several mixing events during summer. The dissolved oxygen concentration in summer at the bottom was often <1 mg/L, even when the difference between top and bottom temperature was as low as 0.5–1.0 °C. Temporarily stratifying lakes with frequent mixing events over the summer are probably common in temperate lowland areas but are easily overlooked in routine monitoring programs. Temporary stratification has pronounced implications for the oxygen concentrations and potentially also for the biota and interactions between sediment and water.
期刊介绍:
Inland Waters is the peer-reviewed, scholarly outlet for original papers that advance science within the framework of the International Society of Limnology (SIL). The journal promotes understanding of inland aquatic ecosystems and their management. Subject matter parallels the content of SIL Congresses, and submissions based on presentations are encouraged.
All aspects of physical, chemical, and biological limnology are appropriate, as are papers on applied and regional limnology. The journal also aims to publish articles resulting from plenary lectures presented at SIL Congresses and occasional synthesis articles, as well as issues dedicated to a particular theme, specific water body, or aquatic ecosystem in a geographical area. Publication in the journal is not restricted to SIL members.