Quantitative Observations of Cyanobacteria and Dinoflagellata in Reservoirs of Sri Lanka
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Ceylon Journal of Science 46(4) 2017: 55-68 DOI: http://doi.org/10.4038/cjs.v46i4.7468 RESEARCH ARTICLE Quantitative observations of Cyanobacteria and Dinoflagellata in reservoirs of Sri Lanka P.A.A.P.K. Senanayake1, 2 and S.K. Yatigammana3* 1Medical Research Institute, Colombo 08, Sri Lanka 2Postgraduate Institute of Science, University of Peradeniya, Peradeniya, Sri Lanka 3Department of Zoology, Faculty of Science, University of Peradeniya, Peradeniya, Sri Lanka Received: 14/06/2017; Accepted: 20/10/2017 Abstract:. Cyanobacterial and dinoflagellate blooms especially during the dry periods (Piyasiri, 1995; have a range of social, environmental and economic Pathmalal and Piyasiri 1995). When considering impacts due to their potential of toxin production the water resources of Sri Lanka, the country under extreme environmental conditions. Therefore, possesses over 10,000 operational reservoirs the present study aimed to understand the species where majority are important as irrigational and abundance, distribution and the relationship between species distribution and measured environmental recreational water bodies while a few are variables within the 45 reservoirs studied, covering important in hydroelectricity generation three major climatic regions of Sri Lanka (Wet, (Maddumabandara et al., 1995). Intermediate and Dry). Plankton samples were obtained using a 34µm plankton net. Both field and Cyanobacterial blooms have an array of laboratory analyses were conducted to obtain social, environmental and economic impacts limnological data of each reservoir. Multivariate (Chorus and Bartram, 1999). The production of statistical techniques were used to understand the toxic substances by a relatively small number of species distribution along measured environmental species that commonly occur in freshwater lakes gradients. Thirteen species of Cyanobacteria were and rivers can have a direct effect on human identified and seven of them were toxigenic. The Dry health (Hunter, 1992; Sethunge and Manage, Zone showed the highest diversity of Cyanobacteria including toxigenic species and the Wet Zone showed 2010). These “cyanotoxins” are usually either the lowest. While Cylindrospermopsis raciborskii was hepatotoxic or neurotoxic in pathology and have the dominant species recorded in 22% of the sampled been related to several cases of human sickness reservoirs, Pseudoanabaena limnetica was the least and death, as well as various occurrences of dominant. Only one species of Dinoflagellate, animal mortality (Falconer, 2005; Kuiper- Peridinium aciculiferum was identified from all the Goodman et al., 1999; Manage et al, 2009; climatic regions. Multivariate statistical analysis Manage et al., 2010). Cyanobacteria are revealed that temperature is the most important frequently present together with other environmental variable that determines the species photosynthetic organisms in mesotrophic waters, variation and abundance among the sites. the common genera being Microcystis, Keywords: Cyanobacteria, Cylindrospermopsis, Synechococcus, Anacystis, Gloeocapsa, dinoflagellata, environmental variables, toxigenic Agmenellum (syn. Merismopedia) as unicellular phytoplankton. and colonial types and Oscillatoria, Lyngbya, Spirulina, Ananbaena, Aphanizomenon, Nostoc, INTRODUCTION Cylindrospermopsis, Planktothrix, Calothrix, Rivularia and Gleoetrichia as filamentous types Cyanobacteria are the most ancient (Kulasooriya, 2011). photosynthetic phytoplankton of the planet Earth that shows an ubiquitous distribution The members of the Dinoflagellata live in (Kulasooriya, 2011). The input of nutrients from both fresh and sea water and many have the natural and anthropogenic sources creates ability to produce toxins. Majority of toxin eutrophic conditions, which lead to the producing species live in marine systems while development of algal blooms especially few freshwater dinoflagellates produce toxins Cyanobacteria in water. Such algal blooms have during unfavorable environmental conditions. been recorded in Sri Lankan freshwaters, Among the toxic dinoflagellates, Peridinium *Corresponding Author’s Email: [email protected] http://orcid.org/0000-0001-6002-8855 56 Ceylon Journal of Science 46(4) 2017: 55-68 polonicum, P. willei, P. volzii and P. aciculiferum evaluate the seasonal variations of the have been identified as common freshwater limnological variables (e.g. Perera et al., 2012; species (Niese et al., 2007). Among them, Yatigammna et al., 2013; Yatigammana and Peridinium aciculiferum, known to produce a Cumming, 2016) no studies have been conducted biological toxin, has already been recorded from to understand the relationship of environmental Sri Lankan drinking water reservoirs conditions and phytoplankton especially, toxin (Yatigammana and Perera, 2017; Yatigammana producing species. Therefore, the factors et al., 2011; Sethunge & Pathmalal,2010; Idroos affecting the distribution of phytoplankton et al., 2017). including toxic algae is not completely understood in Sri Lankan waters. Since However freshwater harmful algal blooms environmental variables which indicate the are generally caused by pelagic Cyanobacteria climatic changes do not occur independently of (Carmichael 2001; 2008). It has been suggested each other, but simultaneously (O‟neil et al., that increasing temperature could benefit 2012), it is important to consider how the Cyanobacteria, both directly and indirectly via interactions of those variables could affect spatial increased thermal stratification (Paerl and distribution of organisms to understand what Huisman, 2008). Nevertheless, it is widely environmental variables are the most important accepted that harmful algal blooms are in explaining the variation of species. As multifaceted events, typically caused by the Cyanobacteria and Dianoflagellata are also combination of multiple environmental factors capable of predicting environmental changes, occurring simultaneously (Heisler et al., 2008). understanding of their distribution in reservoirs The governance of Cyanobacteria in aquatic located in different climatic regions should help ecosystems is frequently linked with CO2 understand what environmental variables are availability (Shapiro, 1990; Caraco and Miller, important in describing species variation under 1998), high temperatures (Bouvy et al., 2000; different environmental conditions. Huszar et al., 2000; Figueredo and Giani, 2009; Soares et al., 2009a), high pH (Reynolds and Hence, this study is focused on i) studying Walsby, 1975; Briand et al., 2002) and high and comparing water quality parameters of concentrations of nutrients (especially selected reservoirs in three major climatic phosphorus) (Watson et al., 1997). Furthermore, regions of Sri Lanka (Wet, Intermediate and Dry some Cyanobacteria show decreased cell division Zone); ii) assessing the relationship between rates in response to lower pH conditions (Shapiro species diversity, abundance and measured and Wright, 1990; Whitton and Potts, 2000; environmental variables within the study Czerny et al., 2009). Though many eukaryotic reservoirs; iii) identifying potential causes for phytoplankton cannot tolerate changes in environmental conditions which promote the salinity, a number of Cyanobacterial species have growth of toxgenic species; iv) proposing the euryhaline ability. Therefore changes in suitable remedial measures. salinity may influence community composition as well as potential toxin concentrations and MATERIALS AND METHODS distribution (Laamanen et al., 2002; Orr et al., 2004; Tonk et al., 2007). Site selection During recent times, there has been much Study sites were selected considering the age, concern in the processes influencing the growth climatic region, catchment characteristics, of phytoplankton communities mainly in relation morphometry, biological composition and known to physico-chemical factors (Akbay et al., 1999; algal outbreaks within the recent five years. Peerapornpisal et al., 1999; Elliott et al., 2002). Considering the reservoir density forty five (45) However, most of the studies on Sri Lankan reservoirs from the three major climatic regions reservoirs have been focused on the composition of Sri Lanka (Wet, Intermediate and Dry Zone) and diversity of planktonic algae (e.g. were selected including five (05) from Wet Zone, Abeywickrama, 1979; Rott 1983; Silva, 2013). fourteen (14) from Intermediate Zone and twenty In addition to a few studies carried out to six (26) from the Dry Zone (Figure 1). P.A.A.P.K. Senanayake and S.K. Yatigammana 57 Figure 1: Locations of the 45 study reservoirs in Sri Lanka. The country is divided into three main climatic regions: the Dry Zone, the Intermediate Zone and Wet Zone. Sample collection Steps were taken to complete the biological analysis as early as possible with a maximum Collection of water samples for the biological delay of 48 hrs. Samples were observed using a and limnological analysis was done from July, research microscope (Olympus CX 31) equipped 2015 to March, 2016. For the chemical analysis with phase contrast optics. The species were samples were collected from 0.3m below the air- identified to the lowest possible taxonomical water interface close to the middle and at least level using standard identification guides (e.g. from four other sites identified from each Bellinger and Sigee (2010), Abeywickrama reservoir. (1979)). Relative abundance of each taxon was Collection of Biological data calculated using the following equation to understand the abundance of Cyanobacteria