Microcystis Bloom in an Urban Lake after River Water Diversion—A Case Study

To improve the water quality of Lake Yuehu, a water diversion from the Han River was conducted in July 2008. However, an unexpected Microcystis bloom occurred in the lake after water introduction. Water and sediment samples were collected from Lake Yuehu and the variation of chemical and biochemical parameters, as well as the phytoplankton community, were analyzed during the water diversion to assess its effect and to clarify the mechanism leading to the Microcystis bloom. The nitrogen (N) concentration was increased and phosphorus (P) concentration decreased in Lake Yuehu after receiving water from the Han River, which had a high loading of N and a low loading of P. These conditions may benefit the growth and dominance of non-N2 fixing Microcystis, as it may not have suffered from P limitation during our study because it did not produce extracellular phosphatase, which worked as an indicator of P deficiency, as evidenced by the in situ enzyme-labelled fluorescence. Notably, the sediment Fe (OOH)~P content significantly decreased in Lake Yuehu; this pulsed release of P from the sediment might have sustained the Microcystis bloom. Based on our results, algal blooms may occur as a consequence of conducting water diversion projects to improve water quality.

Biological and Chemical Investigations of Water Quality and Contamination Study After a Suspicious Algal Bloom in a Coastal Lagoon, Jeddah, Saudi Arabia

The General Authority of Meteorology and Environmental Protection (GAMEP) started an investigation about suspicion of microcystis bloom with toxin production in lagoon near Obhour, Jeddah. Water samples were collected from different spots covering all lagoon directions. The samples were analyzed for salinity, coliforms, toxin producing microalgae using MPN, and microscopic examination. LC/MS-MS analysis was used to identify and quantify the extra-cellular microcystins (MCs) in the lagoon water. The results revealed complete absence of the toxic algae or its secreted toxins. The results revealed the presence of Dunaliella salina with rich ?-carotene production responsible for brown or pink color in the lagoon.