Aquachemistry and Rotifer Diversity in Lentic and Lotic Waters

Abstract

In the present study, the aquachemistry of one lotic and three lentic water bodies was investigated. As part of this I also examined density and diversity of rotifer species. The physico-chemical parameters of water such as temperature, pH, dissolved oxygen, TDS, electrical conductivity, total hardness, transparency and turbidity were evaluated. Correlation between rotifers and these parameters was also investigated. Sampling was done on monthly basis between 9.0 A.M. to 1.0 P.M. from October 2011 to September 2012. For rotifer collection from lotic water, 50 litre of water was passed through standard plankton net of 37 µm mesh size by towing the net horizontally for 2 to 3 minutes from a depth of 15-25 cm. From lentic water, 40 litre of water was collected in a plastic bucket and this water was passed through a sieve of 341 µm mesh size. Filtered water was filtered again through a sieve having 37µm mesh size. The contents of the sieve were washed in a small plastic tub. Rotifers were preserved in 4% formaldehyde solution in 50 ml plastic bottles. Rotifer species were counted in a Sedgewick-Rafter chamber at 60-100 x magnification by inverted OLYMPUS microscope. The body shape, morphological features and behaviour of the rotifers were observed for identification by using the keys of Hyman, 1951; Ward and Whipple, 1959; Pennak, 1978; Segers, 2007. In the present work, 115 rotifer species belonging to 27 genera and 15 families have been collected and identified from lentic and lotic waters. This is the largest number of rotifer species collected in Pakistan. Among 15 families, the maximum of 7 genera belonged to the family Brachionidae and followed by Notommatidae with 3 genara. Brachionus, Lepadella, Lecane and Trichocerca were the most diverse genera that found throughout the study period. Analysis of variance of lentic and lotic waters showed that water temperature, dissolved oxygen, TDS, electrical conductivity, total hardness, transparency and turbidity were statistically significant, while pH was non-significant. Lentic and lotic waters showed similar trends with respect to impact of water parameters on population density and diversity of rotifers. Rotifers reflected positive correlation with temperature, pH, electrical conductivity, total dissolved solids, total hardness and turbidity, while negative correlation with dissolved oxygen and transparency. From lotic water (Nandipur Canal), 28 rotifer species of 10 families and 14 genera were identified. The highest (42.3±13 ind/ml) mean population density was in June and lowest (12±5 ind/ml) in January. The most dominant species was Brachionus calyciflorus with 23.6±6.1 ind/ml mean density. Lecane ungulata had lowest (2.0±0.5 ind/ml) population density, found only in January and May. Rotifer diversity showed increasing trend from spring to summer being the the highest (23 species) in June and the lowest (12 species) in January. In study area 1, 59 rotifer species were present, belonging to 20 genera and 11 families. The highest (127±34 ind/ml) mean population density was in June and lowest (59.3±20 ind/ml) in January. Brachionus calyciflorus showed highest density (49.7±13.9 ind/ml), found throughout the study period. The lowest (5.3±1.8 ind/ml) population density was of Anuraeopsis fissa and found only in four months. Population density of rotifers was seen rising in summer and decreasing in winter. Diversity of rotifer species was maximum (48 species) in September and October and minimum (25 species) in January. In total 74 rotifer species were identified belonging to 14 families and 24 genera from study area 2. Month of June reflected the highest (128.7±40.ind/ml) mean population density and lowest density (64.9±22 ind/ml) in January. Brachionus havanaensis was the dominant species with 40±11.9 ind/ml mean population density, whereas Philodina roseola with lowest population density (3±1.2 ind/ml). June reflected the highest diversity (52 species) and lowest diversity (26 species) in January. Study area 3, revealed 45 rotifer species, belonging to 10 families and 12 genera. The mean population density of rotifers, extended from 97±26 ind/ml to 45.6±8 ind/ml being the highest in June and lowest in January. Brachionus havanaensis showed the highest (43.7±8.9 ind/ml) mean population density. Trichocerca porcellus showed lowest (3.6±1.1 ind/ml) mean population density and represented in June, July, August and September. Diversity of rotifer species was highest (38 species) in three months (August, September and October) and lowest (20 species) in January. In