Hydrophysical and Hydrochemical Controls of Cyanobacterial Blooms in Coursey Pond, Delaware (USA)

Abstract

Noxious cyanobacterial blooms are common in many ponds in the mid‐Atlantic Coastal Plain. In Delaware, blooms normally occur between July and October, yet no in‐depth analyses of the causes and predictors exist. A study using commercially available, high‐frequency, continuous, and automated biogeochemical sensors at Coursey Pond, Delaware, a pond known for perennial summer blooms, was conducted to investigate how hydrophysical and hydrochemical conditions affect bloom dynamics. Cyanobacterial abundance (based on the in vivo phycocyanin fluorescence and phycocyanin/chlorophyll fluorescence ratios) increases during periods of high water temperatures (up to 32°C), low discharge through the pond (mean hydraulic residence time ≥5 d) with evaporative concentration of dissolved solids, and decreasing NO3− concentrations (reaching <0.1 mg L−1, the detection limit). These conditions lead to the uptake and depletion of bioavailable N in the pond surface waters and provide a competitive advantage for temperature‐tolerant and N‐fixing cyanobacteria. Irrigation water use within the watershed can exceed pond discharge during drier summer months, enhancing bloom‐forming conditions. Bloom intensity varies due to storms but persists until mid‐October to mid‐November when temperatures cool, daylength decreases, and discharge and NO3− concentration recovers. Changes in these easily monitored physical and chemical parameters can serve to anticipate the onset, intensity, persistence, and the eventual dissipation of cyanobacterial blooms at Coursey Pond and similar ponds elsewhere. Therefore, the use of sensors and high‐frequency data has the potential to assist in forecasting and management of blooms. Core Ideas Cyanobacteria blooms are common in small flow‐through ponds in the mid‐Atlantic Coastal Plain. Available biogeochemical sensors can characterize bloom onset, intensity, and dissipation. Residence time, temperature, and NO3− concentration are robust predictors of bloom intensity. Storms temporarily disrupt blooms by flushing, but blooms reestablish once stormflow ceases. Irrigation within the watershed increases pond residence time, thus promoting blooms.

Predicting microcystin concentration action-level exceedances resulting from cyanobacterial blooms in selected lake sites in Ohio

“…Specific conductance had a positive effect on one of the inland lake models. During the summertime, elevated specific conductance is associated with low lake levels and stagnation, which are conditions that favor cyanobacterial growth (Andres et al 2019 ). The inclusion of specific conductance as a negative variable in Lake Erie models is harder to explain, but it could simply reflect the temporal patterns of cyanobacteria (highest late summer) and specific conductance (lowest late summer).…”

Coagulation as an effective method for cyanobacterial bloom control: A review

“…Because of their steric effect, hydrophilic effect and electrostatic repulsion effect, cyanobacterial blooms can easily form stable biological particles. Cyanobacterial blooms form foul-smelling floats that restrict light transmission and deprive oxygen from water bodies, affecting the survival of aquatic organisms (Andres et al, 2019). In addition, cyanobacterial toxins (e.g., microcystins [MCs], nodularin, and cylindrospermopsin) produced in cyanobacterial blooms damage the circulatory, digestive and immune systems of aquatic animals (Moustaka-Gouni & Sommer, 2020), and pose a serious threat to human health, causing rashes and liver damage (Ji et al, 2016).…”

Storm-driven hydrological, seasonal, and land use/land cover impact on dissolved organic matter dynamics in a mid-Atlantic, USA coastal plain river system characterized by 21 T FT-ICR mass spectrometry

“…Artificial reservoirs (i.e., millponds, artificial lakes, stormwater retention water bodies), another class of major anthropogenic interventions influencing riverine processes, may also disrupt the pulse-shunt process. Dams in millponds and artificial lakes coupled with frequent irrigation can decrease water flow rates and retain stormwaters, leading to extended water residence times (Friedl and Wüest, 2002;Andres et al, 2019). While storm events can pulse terrestrial materials (i.e., DOM and nutrients) and slightly shorten water residence times in these artificial reservoirs, the storm-derived shunt effects may be muted relative to those observed in free-flowing streams.…”

“…While storm events can pulse terrestrial materials (i.e., DOM and nutrients) and slightly shorten water residence times in these artificial reservoirs, the storm-derived shunt effects may be muted relative to those observed in free-flowing streams. The prolonged water residence times in millponds and artificial lakes create a lentic habitat that fragments the river continuity (Friedl and Wüest, 2002) and allows for very high primary productivity with associated microbial activity (Mansour et al, 2018), particularly during warmer months [i.e., spring and summer; (Oliver et al, 2016;Andres et al, 2019)]. These artificial reservoir systems, therefore, likely (1) contain more algal-influenced DOM than those of free-flowing river systems, (2) export large quantities of algal OM after storms that has accumulated in the interim, and (3) receive ample inputs of nutrients with storms that promote even higher primary production rates.…”

“…This study investigates the integrated roles of LULCs, storm/ precipitation-driven changes in river discharge, and time of year on the concentration and molecular composition of DOM in the Murderkill River (MR), a typical mid-Atlantic coastal plain river system. Artificial lakes and remnants of historical millponds are also important components of the MR system that act as stormwater retention water bodies leading to very long water residence times (Andres et al, 2019). Absorption and fluorescence spectroscopy of DOM were used along with 21 T Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) to evaluate DOM composition, sources, and dynamics in the MR.…”