Global warming as a driving factor for cyanobacterial blooms in Lake Karaoun, Lebanon

Abstract

18 pagesInternational audienceThe Middle East region suffers already from the gradual effects of climate change and will be among the most vulnerable regions in the future. As a result, productivity should undergo losses due to high temperatures, drought, floods and soil degradation which threaten food security of Levantine countries. Since water is the critical factor in the region, even slight changes in air temperature and rainfall patterns will have considerable impact. It has been proven that potential climate change may disrupt, on one hand, most ecosystems through changes in their physicochemical conditions, and on the other hand the species which are living in these ecosystems. Then, the biodiversity can be found challenging. In this study, the effects of climate change on population and phytoplankton communities of Lake Karaoun were investigated since 1992. The climate regime shifts have been shown to alter the lake ecosystem. In the past, Lake Karaoun was characterized by a highly diversified microflora dominated by diatoms and green algae. Recent climatic fluctuations, with culmination in 2008-2011 and temperatures exceeding 40˚C have upset this biodiversity. Blooms of cyanobacteria, specifically Microcystis aeruginosa and Aphanizomenon ovalisporum, have occurred and disturbed both the ecosystem and the functioning of the lake

An overview of diversity, occurrence, genetics and toxin production of bloom-forming Dolichospermum (Anabaena) species

“…A direct influence of global warming is rising water temperature. In 2008-2011, with temperatures exceeding 40 8C in Lake Karaoun, dominance in the phytoplankton community of diatoms and green algae shifted towards cyanobacterial blooms (Slim et al, 2014). The cyanobacteria are better adapted to higher temperatures than other phytoplankton, such as diatoms and green algae (Robarts and Zohary, 1987;Paerl and Huisman, 2008).…”

“…The heightened recent intensity and duration of Dolichospermum blooms (Singh et al, 2010Koreivienė and Kasperovičienė , 2011;Huber et al, 2012;O'Neil et al, 2012;Ciré s et al, 2013;Slim et al, 2014) have been accompanied by surface scums, reduced water transparency, anoxic conditions due to bacterial decomposition of the bloom biomass, and reduced diversity of natural phytoplankton (O'Neil et al, 2012). These effects have increased the financial burden of water treatment when associated with drinking water sources (Lee et al, 2000).…”

“…Recently, climate change dominated by global warming has been linked to the extension and intensification of cyanobacterial bloom events (Peeters et al, 2007;Ye et al, 2011;Huber et al, 2012;Paerl and Paul, 2012;Slim et al, 2014). A direct influence of global warming is rising water temperature.…”

“…From the combined effects of eutrophication and climate change, Dolichospermum blooms have experienced wider occurrence and distribution, prolonged duration and stronger intensity (Singh et al, 2010Koreivienė and Kasperovičienė , 2011;Huber et al, 2012;O'Neil et al, 2012;Ciré s et al, 2013;Slim et al, 2014). Dolichospermum blooms commonly occur between late spring and middle autumn, in some systems followed by Microcystis blooms (Cook et al, 2004;Wang et al, 2013).…”

“…The reported toxins produced by these species can be categorized by chemical structure into three different groups: cyclic peptides (microcystin), alkaloids (anatoxin-a, anatoxin-a(S), saxitoxin, and cylindrospermopsin) (Carmichael, 1986;Chorus and Bartram, 1999;Stü ken et al, 2009;AlTebrineh et al, 2010;Žegura et al, 2011;Singh and Dhar, 2013;Akcaalan et al, 2014;Corbel et al, 2014;Sanchez et al, 2014) and lipopolysaccharide. In recent decades, eutrophication in waters from anthropogenic activities, combined with global warming, have promoted Dolichospermum blooms to expand both in size and duration (Singh et al, 2010Koreivienė and Kasperovičienė , 2011;Huber et al, 2012;O'Neil et al, 2012;Ciré s et al, 2013;Slim et al, 2014). Occurrences of Dolichospermum species and their toxins in large quantities have been documented in numerous water bodies (e.g., Tsujimura and Okubo, 2003;Cook et al, 2004;John and Kemp, 2006;Karjalainen et al, 2007;Kravchuk, 2009;Ciré s et al, 2013;Wang et al, 2013;Callieri et al, 2014), and the incidences of public exposure through drinking water or recreational activities have become more serious (e.g., Bowling and Baker, 1996;Al-Tebrineh et al, 2012), making a review on Dolichospermum cyanobacteria timely.…”