Ecological Impact of Restoration on Water Quality and Macrophyte Diversity in Lake Manzala, Nile Delta

Shallow lakes shift rapidly worldwide from clear-water to turbid-water conditions and degradation, with poor water quality. Coastal wetlands play a crucial role in supporting biodiversity, leading to the resilience of coastal ecosystems. Therefore, rehabilitation of Egyptian wetlands has been of prime importance in Egyptian considerations since 2017, as they are important fish sources, contributing more than 60 % of the total protein provider. The objective of this research is to measure the effectiveness of the governmental development plan, particularly Lake Manzala, which is the largest wetland and most productive of all. This research attempts to follow the abundance of aquatic plant biodiversity, along with water quality, as tools to investigate the real development process sustained. This is done through investigation of water quality and macrophyte long-term variability, before and after developmental work, which can help mitigate the degradation. The investigation showed positive signs of improvement of water quality in Manzala water during the post-development phase, as it transitioned from a poor to a moderate state. Extinctions of native species and/or excessive growth of macrophytes cause the biological diversity to decline. The free-floating vegetation, Salvinia, Nympheae, and other populations are facing threats and were classified as critically endangered a long time ago due to loss of healthy habitats. Therefore, they have never been recorded in this investigation. On the other hand, the free-floating vegetation, water hyacinths (Eichhornia crassipes) and water cress (Pistia stratiotes) remained in front of the heavily polluted drains from 2010 until 2022. Some submerged vegetations disappeared; others showed new records during the investigation periods. After the rehabilitation project, the community structure showed the presence of two free-floating species, four floating herbs, six submerged vegetation, four emergent halophytes and one filamentous green alga. Keywords: Lake Manzala, wetland restoration, water quality, macrophytes, biodiversity