Integration of In Situ and Remote Sensing Measurements for the Management of Harmful Cyanobacteria Blooms. A Lesson from a Strategic Multiple-Uses Reservoir (Lake Occhito, South Italy)

Abstract

Harmful cyanobacteria blooms (HCBs) are one of the main water quality threats affecting reservoirs. Guidelines suggest integrating laboratory, real-time in situ, and remote sensing data in the monitoring of HCBs. However, this approach is still little adopted in institutional measuring programs. We demonstrated that this integration improves frequency and spatial resolution of the data collection. Data were from an intense HCB (Planktothrix rubescens), which occurred in a south Italy multiple-uses reservoir (Lake Occhito) between 2008 and 2009 and regarded both the lake and the irrigation network. Laboratory and in situ fluorometric data were related to satellite imagery, using simple linear regression models, to produce surface lake-wide maps reporting the distribution of both P. rubescens and microcystins. In the first node of the distribution network, microcystin concentrations (4–10 µg L−1) reached values potentially able to damage the culture and to accumulate during cultivation. Nevertheless, our study shows a decrease in the microcystin content with the distance from the lake (0.05 µg L−1 km−1), with a reduction of about 80% of the microcystin concentrations at the furthest tanks. Recent improvements in the spatial resolution (i.e., tens of meters) of satellite imagery allow us to monitor the main tanks of large and complex irrigation systems.

Impounding Reservoirs, Benefits and Risks: A Review of Environmental and Technical Aspects of Construction and Operation

“…Water-quality tests concern, among other things, water transparency, oxygen conditions, acidification, salinity, occurrence of bioindicator organisms, as well as the content of heavy metals and organic or biogenic substances, including above all the concentrations of various forms of nitrogen and phosphorus, which leads to eutrophication of waters. Artificial reservoirs are vulnerable to changes in water quality that may adversely affect the function of the facility, particularly in the case of recreational or potable water storage reservoirs [96][97][98][99][100][101][102][103][104][105][106][107][108]. Research confirms the high sensitivity of the ecological status of reservoirs to land use in their catchment, with growth in built-up or agricultural areas significantly contributing to increased concentrations of undesirable elements [96,97,110].…”

“…Internal sources of pollution can be accumulated bottom sediments releasing, among other things such as phosphorus in the pelagic zone [99] or the phenomenon of seasonal stratification causing mobility of negatively impacted elements and deoxygenated bottom waters [100,113]. Water blooms caused by cyanobacteria are widespread in various climate zones, causing public dissatisfaction; however, due to the complexity of the issue and the lack of a single determining factor, the search for a solution to the problem requires the active participation of the scientific community and a synergy of different research methods [101,102]. Furthermore, in addition to field studies, the use of appropriately selected and calibrated IT models is important in the water-quality-monitoring process.…”

“…C4.1-Reservoir water quality [96][97][98][99][100][101][102][103][104][105][106][107][108] The analyses concern 3 very large and 14 large reservoirs in Asia, 3 large and 5 small reservoirs in Europe and 1 large reservoir in South America. In addition, publications [101,108] review based on a large dataset.…”