Прояв крайового ефекту в структурі заростей макрофітів при зміні гідрологічного режиму

Abstract

У роботі розглянуто зміни структурних характеристик та видового різноманіття макрофітів Кілійської дельти Дунаю при зміні екологічних умов як прояв крайового ефекту. Встановлено, що крайовий ефект достовірно проявляється при переході від лотичних умов (рукави дельти) до лентичних (непроточної водойми-кути). Показано, що в каналах, які з’єднують ці водотоки та водойми, формуються угруповання макрофітів з найбільшим видовим різноманіттям. У виключно лотичних умовах, навіть в місцях розгалуженнях рукавів, та на різних відстанях від таких розгалужень прояв крайового ефекту статистично не доведено. Екологічна структура угруповань макролітів є практично незмінною в межах кожного окремого водотоку на всій його протяжності.

This paper considers the changes in the structural characteristics and macrophyte underwood species diversity of the Kiliya Danube Delta as a detection of the edge effect when the environmental conditions are changing. A total of 27 species of water vascular plants were identified. Moreover, filamentous algae were found but their species and genus were not determined. Biodiversity changes were evaluated using the Shannon Index which integrates species richness and their uniformity in the group. The significance of the results was assessed by testing the null hypothesis which is to verify the absence of changes in the average values of the sample using the Student's t test. Transitional watercourses (channels) have the highest indicators of information diversity where the manifestation of the edge effect is more distinct. There were statistically significant differences between the Shannon index in the end of the branch and the channel, as well as between the channel and the beginning of the water body, at the level of p = 0.05 which indicates the strength of the edge effect in the sample. It is established that the edge effect is reliably displayed in the transition from lotic (delta branches) to lentic conditions (non-flowing reservoirs – "corners"). It is displayed in the form of increasing biological diversity, decreasing in the role of monodominant groups and also in increasing floating pleistophytes quantity. Also in the channels which connect a flowing stream and waterbody is the highest species diversity and the highest Shannon index. Under lotic conditions even in the places of branch ramification and at different distances from such branches, the manifestation of the edge effect is not statistically proven. Therefore, we cannot prove the existence of edge effect in these objects despite the fact that we observe a tendency to increase species diversity at the beginning and end of the watercourse. The ecological structure of macrophyte groups is practically unchanged within each individual watercourse along its entire length. The Ochakivsky branch is dominated by groups of high-grass helophytes and floating pleistophytes, in Starostambulsky by groups of highgrass helophytes and rooted gidatophytes, and in the Vodtochny by low-grass gelophytes and floating pleistophytes.