Community structure of zooplankton and trophic status of some inland reservoirs in the low country intermediate zone of Sri Lanka

Abstract

Diversity and abundance of zooplankton in relation to nitrate-N and total phosphorus levels of 20 minor and medium scale reservoirs in the low country intermediate zone of Sri Lanka were studied in June-October 2013. Total phosphorus content ranged from 0.029 mg L -1 recorded in Wendaruwewa reservoir to 0.529 mg L -1 recorded in Karangamuwa reservoir and Nitrate-N content varied from 1.186 mg L -1 recorded in Adukkane reservoir to 5.625 mg L -1 recorded in Anukkane reservoir indicating that all reservoirs studied are eutrophic. During the present study, a total of 43 species of zooplankton, comprising 31 species of rotifers, 9 species of cladocerans and 3 species of copepods were recorded. Number of zooplankton species in any one reservoir, which ranged from 4 to 13, was significantly correlated with the nitrate-N content (p<0.05). The most widely distributed zooplankton species was Diacyclops nanus, which was present in 15 reservoirs. Abundance of zooplankton ranged from 4 individuals L -1 recorded for Alona monocantha and Chydorus parvus in Wendaruwewa and Metiyagane reservoirs respectively to 1017 individuals L -1 recorded for Filinia terminalis in Galewela reservoir. Margalef index which ranged from 0.532 in Adukkane reservoir to 2.096 in Dewahuwa reservoir, was significantly correlated with nitrate-N content of water (p<0.05). Pielou index ranging from 0.65 in Galewela reservoir to 0.92 in Polpitiya reservoir and Shannon-Weiner index ranging from 0.91 in Munamaldeniya reservoir to 2.13 in Dewahuwa reservoir were not significantly correlated with nitrate-N and total phosphorus levels of water (p>0.05). Keratella quadrata was present only in Anukkane reservoir where the nitrate-N content was the highest and therefore it may be considered as a bio-indicator of high levels of nitrate-N. Eutrophic conditions of theses reservoirs may possibly be due to runoff of nutrients from agricultural fields as these are located in an intense agricultural area. Therefore, it is necessary to take immediate action to control the overuse of inorganic fertilizer in this area so that contamination of water bodies with nutrients can be minimized.

Impact of physico-chemical parameters on composition and diversity of zooplankton community in Nozha hydrodrome, Alexandria, Egypt

“…Pearson correlation analysis indicated that Rotifera population had negative relation (p< 0.01, 0.05) with water temperature (most Rotifer species prefer cold water) (El-Bassat, 1995 andAboul Ezz et al, 2014), total hardness and total alkalinity (r= -0.323, -0.481 and -0.269), but the positive relations were found with nitrate and nitrite (r= 0.281 and 0.383). Similar correlations were recorded by Abdel Mola and Abd El-Rashid (2012), Khanam et al (2014), Menghong et al (2014) and Sangakkara and Wijeyaratne (2015). While Copepoda correlated negatively (p<0.05) with water temperature and total hardness.…”

“…Many zooplankton species disappear with eutrophication are mainly due to toxins produced by algal blooms especially by cyanabacteria blooms and also clogging of their filter feeding apparatus by algal cells (Sangakkara and Wijeyaratne, 2015). This may be attributed to the presence of less number of species of zooplankton in the hydrodrome, which is eutrophic.…”

Environmental factors contributing to the invasion of <em>Najas marina</em> L.in Madu Ganga estuary, a Ramsarwetland in Sri Lanka

“…Several crops including cinnamon, coconut, paddy and vegetable are cultivated in the riparian areas of this estuary. It is well known that the amount of fertilizer used in agricultural activities in many parts of Sri Lanka are very much higher than the required level, so that excess fertilizer are leached into water bodies increasing their nitrate-N and TDP levels (Sangakkara and Wijeyaratne 2015). Amarathunga et al (2010) reported that N. marina was not present in the upper reaches of the estuary where salinity is zero and also near to sea mouth where salinity is very high.…”

Evaluation of the water and sediment quality of a lotic water-body in the western coastal region of Sri Lanka using Rapid Bioassessment Protocol II (RBP II) of benthic macroinvertebrates

“…However, diversity indices of benthic macro invertebrate communities have been used in several studies in order to monitor the environmental conditions (Gamlath and Wijeyaratne 1997;Dahanayaka and Wijeyaratne 2006;Perera et al 2012;Idroos and Manage 2012;Madhushanka et al 2014). In addition, many studies have concentrated on assessment of physicochemical parameters in the aquatic systems of Sri Lanka in order to identify the source and sink areas of pollutants (Sangakkara and Wijeyaratne 2015;Wijeyaratne 2016). Commonly used biotic indices in RBP II technique are accompanied by multivariate approaches that provide information about the spatial and temporal variations of the environmental characteristics of the aquatic environment (Lewin et al 2013;Goldstein 2011).…”