Effects of Water Level Increase on Phytoplankton Assemblages in a Drinking Water Reservoir

Abstract

Excessive water level fluctuation may affect physico-chemical characteristics, and consequently ecosystem function, in lakes and reservoirs. In this study, we assessed the changes of phytoplankton assemblages in response to water level increase in the Danjiangkou Reservoir, one of the largest drinking water reservoirs in Asia. The water level increased from a low of 137 m to 161 m in 2014 as a part of the South-North Water Diversion Project. Phytoplankton assemblages were sampled four times per year before, during and after the water level increase, at 10 sites. Environmental variables such as total nitrogen as well as phytoplankton biomass decreased after the water level increase. Non-metric multi-dimensional scaling analysis indicated that before the water level increase, phytoplankton assemblages showed distinct seasonal variation with diatom dominance in both early and late seasons while such seasonal variation was much less evident after the water level increase.Month and year (before and after) explained 13% and 6% of variance in phytoplankton assemblages (PERMANOVA, p < 0.001) respectively, and phytoplankton assemblages were significantly different before and after the water level increase. Both chlorophytes and cyanobacteria became more abundant in 2015. Phytoplankton compositional change may largely reflect the environmental changes, such as hydrodynamics mediated by the water level increase.

Effect of Water Column Stability on Surface Chlorophyll and Time Lags under Different Nutrient Backgrounds in a Deep Reservoir

“…Environmental factors such as nutrients, light, and hydrodynamic conditions [1][2][3] impact the general composition of phytoplankton through their synergistic effects. High concentrations of nutrients are critical for the formation of algal blooms but are not always the determining factor [4].…”

Water Quality Restoration of a Drinking Water Outlet Area in a Eutrophic Reservoir Using Hypolimnetic Oxygenation in Southwest China

“…Recent studies have shown that water level fluctuations have a great influence on the phytoplankton composition [44]. Phytoplankton compositional changes may greatly reflect environmental changes, such as changes in hydrodynamics mediated by water level increases [45]. Therefore, long-term monitoring of the phytoplankton evolution in the AHR was conducted while artificially controlling of the water levels.…”

Cambios y tendencias en la limnología de un sistema de embalses andino: 10 años de estudio de los ecosistemas del complejo Punchiná-San Lorenzo-Calderas

“…Al igual que lo registrado en el embalse Punchiná, en San Lorenzo el fitoplancton no fue afectado por las temporadas climáticas de sequía y lluvia, pero cuando estas últimas se incrementaron en gran magnitud durante el fenómeno de La Niña, la estructura fitoplanctónica sufrió alteraciones significativas y disminuyó su número de individuos (glm ajustado a gamma inverso; densidad aic = 1107,6; p = 6,97e -7 ), de taxones y su diversidad en general (figura 124). En embalses colombianos y del trópico en general existen muy pocos estudios sobre los efectos de los fenómenos enso sobre la comunidad algal (Hernández-Roa, 2014;Pineda et al, 2019); sin embargo, en otros sistemas se ha reportado también la disminución de la diversidad durante las fuertes lluvias causadas por el fenómeno de La Niña (Doan-Nhu et al, 2016) y un descenso de la biomasa algal por el incremento del nivel del agua (Pan et al, 2018), debido al efecto de dilución.…”