Vulnerability assessment of oligo-mesotrophic habitats of Lake Svityaz to recreational load using satellite imagery

Abstract

Lake Svityaz is the largest and deepest lake of natural origin in Ukraine. It forms a unique complex of aquatic habitats, considered of high value for conservation within the Shatsk National Nature Park as well as the entire West Polesie Transboundary Biosphere Reserve. Meanwhile, due to its tourist attractiveness, the lake suffers from significant anthropogenic impact. Constantly increasing recreational load leads to decline in resistance and resilience of the lake ecosystem.

The main purpose of our research was to detect and analyze transformations of vulnerable freshwater oligo-mesotrophic habitats of Lake Svityaz and examine effectiveness of using multi-temporal satellite images to estimate impact of recreation on the lake's littoral.

Using Landsat satellite imagery series (June-August) over the 30-year period (1985-2015) and seasonal series of Sentinel-2 imagery for 2016-2017 a set of habitat maps was obtained. Previously developed two level algorithm for plant habitats recognition utilizing multispectral satellite and seasonal data was applied [1, 2]. Analysis of the acquired thematic maps is shown that the main types of oligo-mesotrophic habitats are well recognized on the satellite images owing to the high transparency of the lake water. Main spatial and temporal patterns of macrophyte aquatic vegetation transformations of C.1.1-C.1.2 oligo-mesotrophic boreal habitats affected by organized and uncontrolled recreation are identified. It is revealed that direct mechanical impact caused by recreants leads to integrity destruction of aquatic plant communities, loss of Chara and alluvial-dependent macrophyte species and to structure simplification of species communities. It also results in degradation of macrophyte thickets and loss of endangered and vulnerable freshwater habitats formed to a depth of 1.5 m. Permissible recreational load for the lake's littoral is estimated. Assessment results may provide conservation managers, municipal officials and researchers with substantial information on the lake's threatened habitat vulnerability to recreational load.

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