Abstract

Simple SummaryBenthic fauna is an important element of the aquatic trophic chain, the basic element of biomonitoring. Our research was aimed at demonstrating the sensitivity of benthic fauna to the diversified morphometry of a single lake on the example of Lake Wicko (southern coast of the Baltic Sea). Our results show that lake morphometry plays a major role as a structuring factor for macroinvertebrates communities. Two segments of the lake, different in size and depth, show decreasing differences in the trophic state, abundance, diversity and number of indicator species of benthic fauna with the depth gradient. The greatest differences in abundance were observed in the shallowest zone of the bottom (eulittoral), where the chironomids differed the most. In the sublittoral of both lake segments, a simplified structure of benthic communities was found. Differences between the two segments within the intermediate zone (infralittoral zones) were recorded for mollusks and large crustaceans and the Oligochaeta/Chironomidae abundance ratio. The feeding groups were dominated by shredders in the eulittoral and infralittoral of the deeper lake segment. We recommend testing benthic macroinvertebrates in lakes with different morphometrics individually for each depth zone.We investigated the response of benthic macroinvertebrates in the eulittoral, infralittoral, and sublittoral zones, in two segments of the freshwater Lake Wicko on the coast of the Baltic Sea. Our results showed that the morphometry of lakes plays a major role as a factor structuring the macroinvertebrates communities. Two parts of the lake, different in size and depth, show decreasing differences in the trophic state, abundance, diversity and number of indicator species of benthic fauna with the depth gradient. The most significant differences were observed between the littoral zones of both segments. Similar environmental conditions in the sublittoral zones corresponded to the simplified structure of the benthic macroinvertebrates communities. In the infralittoral zone, the most significant differences between the two segments, were recorded for mollusks and large crustaceans as well as the Oligochaeta/Chironomidae abundance ratio. In the sublittoral zone, the diversity of chironomids differed most strongly. Lower species diversity was found in the part of the lake with a slight depth decrease. Shredders reached significantly higher values in eulittoral and infralittoral of the deeper lake segment. Average Score Per Taxon increased with a depth gradient. We recommend testing benthic macroinvertebrates in lakes with different morphometrics individually for each depth zone.

Highlights

  • Natural changes of lakes and the associated gradual increase in eutrophication are major causes of ecological degradation in terms of aquatic biodiversity

  • The analysis of differences in physicochemical properties of water between the depth zones in both segments of Lake Wicko showed that the largest contrasts were in concentrations of Chl-a, Na+, and Cl- (p < 0.0001), which were significantly higher in the western segment of the lake

  • This study shows the possibility of using various metrics of benthic fauna for comprehensive assessment of trophic states of water bodies, with complex internal morphometrical structure, under the influence of eutrophication

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Summary

Introduction

Natural changes of lakes and the associated gradual increase in eutrophication are major causes of ecological degradation in terms of aquatic biodiversity. Shallow polymictic lakes reach an advanced stage of development because almost their entire water volume takes part in most of the energy processes and phenomena, along with a relatively large surface area of active bottom sediments Such processes are typical of coastal lakes connected with, or isolated from, the sea [2,3]. Benthic macroinvertebrates mediate trophic transmission from the first level of consumers in the detritus food chain to the upper levels of consumers, and predators [10] They produce a morphologically and behaviorally diversified range of mechanisms of exploitation of the available categories of trophic resources, in the form of coarse organic particles (CPOM, particles > 1.0 mm), fine organic matter (FPOM, particles > 0.45 μm and < 1.0 mm) and living organisms. Benthic macroinvertebrates can be subdivided into functional feedings groups (FFGs) [11]

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