Response of Submerged Aquatic Vegetation to Water Depth in a Large Shallow Lake after an Extreme Rainfall Event

Abstract

Submerged aquatic vegetation (SAV) is an important part of lake ecosystems, and a proper SAV community structure is the key factor in keeping a clear-water state. Although the response of SAV to water depth has been widely studied in different aquatic environments, little is known about the response of the SAV community to changes in water depth of a large lake after an extreme rainfall event. To examine this question, 780 samples were collected from Lake Taihu, China, between 2013 and 2017 to analyze the variations in SAV and water depth. The water level of the lake ranged from 2.75 to 4.87 m, and the water depth at sampling sites ranged from 1.07 to 3.31 m. The SAV biomass at the sampling sites ranged from 0 to 17.61 kg/m2. The influence of water depth on SAV biomass and frequency of occurrence differed by seasons and by species. The adaptation of SAV species to increasing water depth is a key element for community dynamics, which in turn contributes to water level regulation. A new method was proposed to identify the optimal water depth for SAV biomass accumulation based on calculation of the cumulative probability and probability density.

Satellite Imageries and Field Data of Macrophytes Reveal a Regime Shift of a Tropical Lake (Lake Ziway, Ethiopia)

“…A shift in water level of shallow lakes disrupts ecosystem functioning and causes a change between clear and turbid stable states which in turn alter the distribution of macrophytes' growth form and diversity [15,24,42]. This is mostly observed in littoral habitats which can be easily affected by moderate water level fluctuations [17,96]. In Lake Ziway, a decreasing trend in macrophyte distribution was considerably associated with a decline in the surface water area, whereas the semi terrestrial vegetation and the mudflat distribution increased over the last 30 years.…”

“…Distribution and composition of macrophyte communities are influenced by nutrient load, and climatic and hydrological conditions such as spatial and temporal variations of water level [7,11,[15][16][17][18]. Lake water level changes provide an opening for seedling recruitment for perennial emergent aquatic plants [19][20][21].…”