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)

Diego Copetti,Mariano Bresciani,Licia Guzzella,Raffaella Matarrese

doi:10.3390/w13162162

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.

Highlights

IntroductionCyanobacterial blooms are becoming increasingly frequent in lakes [1,2,3]; their increase is likely driven by different factors related to both global (e.g., atmospheric temperature increase) and local (e.g., nutrient loads) environmental modifications [4,5,6,7]
Cyanobacterial blooms are becoming increasingly frequent in lakes [1,2,3]; their increase is likely driven by different factors related to both global and local environmental modifications [4,5,6,7]
The results presented in this paper form an original contribution on how cyanobacteria blooms develop in multiple-uses reservoirs

Summary

Introduction

Cyanobacterial blooms are becoming increasingly frequent in lakes [1,2,3]; their increase is likely driven by different factors related to both global (e.g., atmospheric temperature increase) and local (e.g., nutrient loads) environmental modifications [4,5,6,7]. Mass development of cyanobacteria may determine different detrimental effects on the lake ecosystem, including a turbidity increase and oxygen depletion, with negative effects for macrophytes, invertebrates, and fish species [8]. Cyanobacteria are a natural component of the planktonic population [9], some cyanobacterial species can produce toxic peptides and alkaloids [10], whose presence can determine a reduction in the ecosystem services, such as drinking and irrigational supply, fishing, and bathing [3,11,12,13]. The filamentous and potentially toxic cyanobacterium Planktothrix rubescens has colonized many environments in Europe [14], often appearing in mesotrophic conditions during the recovery of the trophic state of the lakes [15,16,17]). A conspicuous presence of this species has been recently documented in Italy [19] with examples in northern [14,20,21], central [22,23], and southern [24,25] Italy

Results

Discussion

Conclusion