Manasquan Reservoir Aquatic Plant and Cyanobacteria Management Plans

The Manasquan Reservoir is a 770-acre pump-storage impoundment that is owned and operated by the New Jersey Water Supply Authority (NJWSA). The reservoir experienced eutrophication as evidenced by cyanobacteria blooms. Additionally, the non-native hydrilla (Hydrilla verticillata) and fanwort (Cabomba caroliniana) have become established throughout the reservoir’s 204-acre littoral zone. Recognizing the potential severity of problems attributable to either reoccurring cyanobacteria blooms or the continued spread of invasive macrophytes, the NJWSA sought to develop a comprehensive management plan to be implemented in a proactive manner to protect and manage the reservoir’s water quality and minimize the recreational impacts attributable to invasive aquatic plants.

As part of this three-year (2018 – 2020) work effort, Princeton Hydro designed and implemented an extensive aquatic plant management plan including a bathymetric survey; design and implementation of a point-intercept based sampling methodology utilizing rake tosses; additional survey of spatial extent of macrophytes with SCUBA divers; and sediment core collection and analysis for monoecious hydrilla tubers. All plant data collected as part of this study was georeferenced in the field and assembled into a geo-referenced database showing the distribution, extent, and change in time of hydrilla and other aquatic plants throughout the three-year monitoring period. Additionally, Princeton Hydro conducted several water quality monitoring events throughout the 2018 growing season.

The project has documented the presence, extent, and abundance of all aquatic plants in the reservoir with particular focus on hydrilla and fanwort. To complete the project, all data was integrated into the functional Manasquan Reservoir Plant and Algae Management Plan, aiming to eradicate or manage certain species of plants to improve the ecological integrity of the reservoir while optimizing raw water quality for consumptive end use. Princeton Hydro continued to monitor water quality within Masaquan Reservoir throughout 2019.