Occurrence of toxic cyanobacterial blooms for the first time in Lake Karaoun, Lebanon

Abstract

The increasing occurrence of cyanobacterial bloom in freshwaters worldwide is of great importance because of public health risks. In addition, they are very likely to have negative impact on ecological and economic aspects. In this study, the seasonal succession of phytoplankton population in Lake Karaoun in Lebanon was monitored from May 2009 to June 2011. The physicochemical parameters of lake water were then monitored for 1 year, from June 2010 until June 2011, to correlate the physicochemical parameters with the phytoplankton population in the lake. Our results showed, for the first time in Lebanon, that the eutrophied Lake Karaoun has been under the invasion of toxic cyanobacterial blooms since May 2009. The cyanobacterial bloom was persistent from late spring (May) until late fall (December) for 2 consecutive years. The high water temperature in the summer season is the main factor that has been affecting the growth of the cyanobacteria. The most frequently encountered bloom‐forming species were Microcystis aeruginosa and Aphanizomenon ovalisporum, which were either present individually or coexistent. The obtained results showed that during the period of cyanobacterial bloom, a deterioration of water quality defined by low levels of dissolved oxygen, total dissolved solids, and electric conductivity was reported. During cyanobacterial bloom period, the concentration of the orthophosphate–P (PO4‐P) was very minimal. The measured high value of chlorophyll‐a concentration during cyanobacterial bloom period (48.6 μg/L) was attributed to high photosynthetic activity. Cyanobacterial blooms can cause a variety of water‐quality problems in Lake Karaoun in addition to human health risk.

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

“…Humphries and Lyne (1988) found that high rising velocities of Microcystis aeruginosa could concentrate them near the surface, and favour scum formation and thus losses from wind-driven advection to the edges. Visible scums at the edges of Karaoun Reservoir were previously reported by Atoui et al (2013).…”

Patterns of succession between bloom-forming cyanobacteria Aphanizomenon flos-aquae and Microcystis and related environmental factors in large, shallow Dianchi Lake, China

“…et Flah. and Planktothrix agardhii (Gomont) Anagnostidis et Komárek (Teubner et al, 1999), Anabaena circinalis Rabenh or Cylindrospermopsis raciborskii (Woloszyńska) Seenayya et Subba Raju and Microcystis aeruginosa Kützing (Soares et al, 2009), Cylindrospermopsis raciborskii and Aphanizomenon ovalisporum Forti (Messineo et al, 2010), Aphanizomenon or Anabaena and Microcystis (Tsukada et al, 2006), and Microcystis aeruginosa and Aphanizomenon ovalisporum (Atoui et al, 2013). Many factors influence the competition and succession among different cyanobacterial genera, such as nitrogen, phosphorus, the ratio of total nitrogen to total phosphorus, water temperature, light intensity, thermal stratification, allelopathic effects, grazing, competition, etc., and they play a role in succession either individually or synergistically (Scheffer & Carpenter, 2003).…”

Modelling the surface circulation and thermal structure of a tropical reservoir using three‐dimensional hydrodynamic lake model and remote‐sensing data

“…Understanding the physical processes that occur inside the reservoir and its driven forces is crucial for the management and optimization of these systems, especially those utilized for drinking water and power generation. The water circulation and mixing process can be related with phytoplankton dynamics (Vidal et al 2010), iron and manganese release (Tundisi et al 2004), phosphorus dynamics (Komatsu et al 2006), cyanobacteria bloom (Atoui et al 2012), and greenhouse gas emissions (Rudorff et al 2011).…”