Macrophyte response to the protection and restoration measures of four water bodies

Abstract

Macrophytes are a good long-term indicator of quality of aquatic ecosystems and are essential for the proper functioning of the entire lake ecosystem. Submerged vegetation is considered to be indicative of an improvement of the ecological status of these lakes. Here, we analyzed the distribution, structure, and diversity of vegetation communities in four eutrophic water bodies (postglacial lakes: Slawskie and Uzarzewskie and man-made lakes: Maltanski Reservoir and Turawa Średnia Reservoir) after the application of restauration and protections measures. The restoration measures included biomanipulation, phosphorus inactivation, hypolimnion aeration, or injection of nitrate-rich waters to the hypolimnion. All of them were sustainable and did not cause drastic changes in the ecosystem. Between 9 and 17 macrophyte communities were found in the examined water bodies. The largest effects were observed after the simultaneous use of three lake restoration techniques which led to the appearance of 17% charophytes. Pronounced effects leading to the higher contribution of elodeids to the macrophyte community were achieved in the lake in which two methods were applied. Least effective was the method focused on hypolimnion restoration in a small lake, which did not cause the reappearance of submerged vegetation. Spontaneous recovery achieving good status is also possible in a large lake in case of applying the thorough conservation measures. An intensive growth and diversity of macrophytes was a result of the improvement in the water quality as a consequence of undertaken protective activities and/or restoration measures. However, the re-colonization of submerged macrophytes during restoration process is not obvious and the feed-back mechanisms may delay a response of the ecosystem. The vegetation of the studied lakes was unstable, showing high variability in individual years of research, which indicates that these ecosystems are still under reconstruction and not reach equilibrium state yet.