LANDSCAPE STRUCTURE OF THE WESTERN COAST OF SEVASTOPOL

The information about the landscape structure of the western coast of Sevastopol. Landscape studies (summer 2020) were conducted by detailed study of key sites using landscape profiling. In the landscape structure of the study area identified 8 bottom natural complexes (BCN). The capes at a depth of 0.5-5 m are characterized by underwater slope landscapes with boulder and boulder heaps and bedrock outcrops dominated by Carpodesmia crinita and Treptacantha barbata. Between the capes at these depths, underwater slope landscapes formed by sandy sediments, devoid of benthic vegetation, where individual clumps are also dominated by Carpodesmia crinita and Treptacantha barbata. An underwater coastal slope composed of coarse-clastic sediments dominated by Treptacantha barbata, and with alternating pebble-gravel with battered shell sediments dominated by Phyllophora crispa, was recorded at a depth of 5–10 m. A weakly sloping plain composed of gravel-sandy sediments with broken shells, dominated by Phyllophora crispa, can be traced at a depth of 10–15 m. The formation of its landscape structure is influenced by both the natural features of the coastal zone and economic activities in the adjacent territory.

Silica Storage, Fluxes, and Nutrient Stoichiometry in Different Benthic Primary Producer Communities in the Littoral Zone of a Deep Subalpine Lake (Lake Iseo, Italy)

Benthic vegetation at the land-water interface is recognized as a filter for silica fluxes, which represents an important but under-investigated subject. This paper aims to analyze stocks and fluxes of biogenic (BSi) and dissolved (DSi) silica in relation to nitrogen (N) and phosphorus (P) in the littoral zone of a deep lake. Specifically, we evaluated how different primary producers can influence BSi retention and DSi release. The study was performed from April to October in 2017, in three different benthic communities: submerged aquatic vegetation (SAV) and microphytobenthos (MPB), both occurring in soft bottom sediments, and epilithic macro- and microalgae (EA) on rocky substrates. The main result was that SAV and MPB were a DSi source and a N and P sink with the DSi efflux from SAV nearly three times as much as in MPB patches. These findings corroborate the hypothesis that SAV mediates the DSi transport from pore water to the water column. Conversely, EA communities were a DSi sink and a N and P source. Overall, these results highlight the fact that the littoral zone of lakes plays a key role in regulating aquatic Si cycling, which is likely to depend on the health status of SAV communities.

Catchment land use predicts benthic vegetation in small estuaries

Many estuaries are becoming increasingly eutrophic from human activities within their catchments. Nutrient loads often are used to assess risk of eutrophication to estuaries, but such data are expensive and time consuming to obtain. We compared the percent of fertilized land within a catchment, dissolved inorganic nitrogen loads, catchment to estuary area ratio and flushing time as predictors of the proportion of macroalgae to total vegetation within 14 estuaries in south-eastern Australia. The percent of fertilized land within the catchment was the best predictor of the proportion of macroalgae within the estuaries studied. There was a transition to a dominance of macroalgae once the proportion of fertilized land in the catchment exceeded 24%, highlighting the sensitivity of estuaries to catchment land use.