On the successful use of a simplified model to simulate the succession of toxic cyanobacteria in a hypereutrophic reservoir with a highly fluctuating water level

Abstract

Slim, et al.. On the successful use of a simplified model to simulate the succession of toxic cyanobacteria in a hypereutrophic reservoir with a highly fluctuating water level. Environmental Science and Pollution Research, Springer Verlag, 2017, 24 (26), pp.20934-20948. 10.1007/s11356-017-9723-9. hal-01592944 1 This article was published as: Ali Fadel, Bruno Lemaire, Brigitte Vinçon-Leite, Ali Atoui, Kamal Slim, et al. (2017). On the successful use of a simplified model to simulate the succession of toxic cyanobacteria in a hypereutrophic reservoir with a highly fluctuating water level. Environmental Science and Pollution Research, 24 (26), pp.20934 -20948. DOI : 10.1007/s11356-017-9723-9 On the successful use of a simplified model to simulate the succession of toxic cyanobacteria in a hypereutrophic reservoir with a highly fluctuating water level AbstractMany freshwater bodies worldwide that suffer from harmful algal blooms would benefit for their management from a simple ecological model that requires few field data, e.g., for early warning systems. Beyond a certain degree, adding processes to ecological models can reduce model predictive capabilities. In this work, we assess whether a simple ecological model without nutrients is able to describe the succession of cyanobacterial blooms of different species in a hypereutrophic reservoir and help understand the factors that determine these blooms. In our study site, Karaoun Reservoir, Lebanon, cyanobacteria Aphanizomenon ovalisporum and Microcystis aeruginosa alternatively bloom. A simple configuration of the model Dyresm-Caedym was used: both cyanobacteria were simulated, with constant vertical migration velocity for Aphanizomenon ovalisporum, with vertical migration velocity dependent on light for Microcystis aeruginosa and with growth limited by light and temperature and not by nutrients for both species. The model was calibrated on two successive years with contrasted bloom patterns and high variations in water level. It was able to reproduce the measurements: it showed a good performance for the water level (root mean square error (RMSE) lower than 1 m, annual variation of 25 m), water temperature profiles (RMSE of 0.22 -1.41 °C, range 13-28 °C) and cyanobacteria biomass (RMSE of 1 -57 µg Chl a L -1 , range 0-206 µg Chl a L -1 ). The model also helped understand the succession of blooms in both years. The model results suggest that the higher growth rate of Microcystis aeruginosa during favourable temperature and light conditions allowed it to outgrow Aphanizomenon ovalisporum. Our results show that simple model configurations not only can be sufficient for theoretical works when few major processes can be identified, but also for operational applications. This approach could be transposed on other hypereutrophic lakes and reservoirs to describe the competition between dominant phytoplankton species, contribute to early warning systems or be used for management scenarios.

Lake surface temperature retrieval from Landsat-8 and retrospective analysis in Karaoun Reservoir, Lebanon

“…Monitoring of water temperature was mainly performed on a single point S D near the dam in 2016. 33 With no measurements available on a spatial scale (except for 2017) and given the effect of water temperature on its biota distribution, 34 synoptic estimations of water surface temperature are valuable for this ecosystem.…”

Sustaining the ecological functions of the Litani River Basin, Lebanon

“…The level of N and P in the Qaraoun reservoir is increasing and the development of cyanobacteria became a real problem for aquatic life, swimmers, and animals. During the dry season, the concentration of these cyanobacteria is often above 200 µg/l (Fadel et al, 2017), much higher than the concentration of 10 µg/l, recommended by the World Health Organization (WHO). These cyanobacteria were shown to produce cyanotoxins that can threaten both human health and the reservoir ecosystem (Fadel et al, 2014).…”

A modelling approach to simulate Chlorophyta and Cyanobacteria biomasses based on historical data of a Brazilian urban reservoir

“…The ecological models have been applied, mainly, coupled with hydrological models on a basin scale (Munar et al, 2018;Tambara et al, 2017;Silva et al, 2016), for the understanding of the spatial-temporal distribution of cyanobacteria and climate change (Fadel et al, 2019;Rigosi et al, 2014), as well as to understand the succession of toxic cyanobacteria (Chia et al, 2018;Fadel et al, 2017;Vinçon-Leite et al, 2017;Burford et al, 2016).…”