New records of desmids from Ropar wetland (a Ramsar Site) of Punjab, India

This study deals with exploration of freshwater desmids for the first time from Ropar wetland (Ramsar site) of Punjab (India) to assess their taxonomic aspects and bio-geographical distribution. During this study, samples of planktonic, epiphytic and epilithic desmids were collected from littoral zone and were observed under light microscope for their morphometric characteristics based identification. Total 21 desmids species belonging to 4 genera of 2 families (Closteriaceae and Desmidiaceae) were identified from the collected samples. Among them, Cosmarium with 11 species (C. awadhense, C. bioculatum, C. trilobatum, C. divergens, C. granatum, C. moniliforme, C. nitidulum, C. subtumidum, C. reniforme, C. undulatum and C. obtusatum) was found to be most abundant followed by Closterium with 7 species (C. acerosum, C. dianae, C. incurvum, C. leibleinii, C. lunula, C. pritchardianum and C. aciculare), Euastrum with 2 species (E. spinulosum and E. platycerum) and Staurastrum with 1 species (S. crenulatum). The geographic distribution of identified desmid taxa in India has been also recorded. All the desmid taxa identified during this study are new record for the Punjab state of India. The results of this study provide significant baseline data for the future taxonomic and ecological studies from the similar habitats.


Introduction
Globally, wetlands are recognized as one of the most biologically diverse and unique habitats for various plant and animal species (1). Wetlands are also considered as important aquatic environments that provides valuable ecosystem services by supporting high rates of primary production (1,2). In spite of their importance, most of the world's wetlands are under threat due to the increased human interference including deforestation, change in land use practices, domestic and industrial pollution etc. in their catchment areas and watershed (1,3). As a result the hydrology, hydraulic patterns and geomorphology of most of the wetlands have been influenced that directly impact their biodiversity and other ecosystem services (1,2). At the same time, it has been recognized that proper protective and conservation efforts have not been implemented for such important ecosystems due to lack of knowledge about their ecological values and benefits (2,5) Therefore, the assessment of biodiversity and its role becomes important for the better understanding of services and functions of wetlands (6,7). Algae, as main primary producers, play important role in functions of wetlands and can be the key indicators for their ecological conditions (2). Algae often are conspicuous feature of both estuarine and freshwater wetlands throughout the world (2). On the basis of cell structure algae are mainly two types: prokaryotic (Blue green algae) and eukaryotic (all other algal forms including desmids). Desmids are microscopic, unicellular, eukaryotic organism belong to class Zygnematophyceae (Phylum Charophyta) of algae (8)(9)(10). The cells of majority of the desmids taxa are transversally curved by constriction (sinus) into two symmetrical semi-cells connected by an isthmus (8,9). The desmids taxa consist symmetrical semi cells and isthmus with pores are known as true desmids (placoderm), whereas smooth walled taxa, without pores and a median constriction are termed as false desmids (saccoderm) (11,12). Desmids are vulnerable groups of aquatic organisms due to their sensitivity to the fluctuations in the environment. Thus, desmids are increasingly used as bioindicator for the monitoring and management of aquatic ecosystems (11,(13)(14)(15). Due to this, the taxonomic and floristic explorations of these organisms become important to understand their complex association with environment.

Study Area
Ropar wetland, manmade fresh water wetland, situated on river Sutlej at 31°01'N latitude and 76°30' E longitude in the Shivalik foothills covering an area of 13.65 sq. km (Fig. 1). This wetland came in to existence in 1952 after the construction of water barrage on river Sutlej at Ropar (Rupnagar district, Punjab). The main reason behind constructing this wetland was to store and divert water through canals for various purposes like irrigation, industrial and drinking water supply (50,51). This was considered as Ramsar site in year 2002, due to its vital role in providing habitat to number of threatened and endangered species of plants and animals (50). This area falls under semiarid zone and relatively less warm region of Punjab and it receives mean annual rainfall of 1518 mm (52). This wetland is very significant from ecological, economic and social heritage point of view. It also serves as significant staging and latent ground for migratory water fowl. The major threats for this wetland are weed invasion by Parthenium and Lantana, siltation, water pollution through anthropogenic activities and grazing etc. (53,54). Previous studies from this wetland have reported the declining status of its water quality and ecological conditions (51)(52)(53)(54). These water quality conditions may causes serious alterations in various abiotic and biotic components of this wetlands. As desmids are considered as good indicator and are sensitive to the fluctuations in water chemistry of any freshwater ecosystem. Thus, it becomes important to evaluate the diversity of desmids from this wetland that may be helpful in future for formulation of any management plan/program for its conservation and rehabilitation.

Sample Collection and Identification
Samples of planktonic, epiphytic and epilithic desmids were collected from littoral zone of study area (Fig. 2). Collected samples were preserved in formalin solution (4%) in wide mouth glass bottles and for further analysis were brought to the laboratory. The voucher specimens of collected samples were assigned with herbarium number (WUA) of Sri Guru Granth Sahib World University, Fatehgarh Sahib (Punjab). The temperature and pH of water were recorded on the spot with digital thermometer (Perfit, India) and digital pH meter (Hanna Instruments, India) at the time of sampling. For the identification of collected material, temporary slides were prepared by mounting sample in Glycerin to study the morphometeric characteristics using light microscope (Olympus CH20i). The species identification was done following standard literatures (55)(56)(57)(58)(59)(60)(61) and the geographic distribution of identified desmids taxa was analyzed from referred literature.

Results
In the present study, a total of 21 desmids taxa belonging to 4 genera (Closterium, Cosmarium, Euastrum and Staurastrum) of 2 families (Closteriaceae and Desmidiaceae) have been reported for the first time from Ropar Wetland, Punjab. The microphotographs of studied desmid taxa are given in Fig. 3 & Fig. 4.
The identification key and detailed taxonomic descriptions of identified taxa are given below:   Narrowly fusiform cells, 160-175 µm long, 13 µm wide; outer margin curved with gradually tapering to narrow inner margin; apices rounded and truncate, 4 µm broad; cell wall smooth, without any colour, with median girdle; chloroplast without ridges and having 3-5 pyrenoids in a medium series (Fig. 3, a).  [28].
Ecological notes: In association with mosses and green algae. pH 7.9, Temp. 19 °C.

Discussion
Present study is a first report from the study area and deals with the diversity of desmid from the Ropar wetland of Punjab, India. In this study, taxonomic position of observed desmid species was investigated on the basis of their phenotypic features and their distribution in India was also determined, the detailed limnological study has not been carried out during this work. A total of 21 taxa of desmids have been recorded during present investigation, earlier only three genera like Closterium, Cosmarium and Penium were reported only at genus level from Punjab (44,45,54). Thus, all the desmid taxa reported during this study are the first report from Ropar Wetland as well as from Punjab. Out of 21 taxa of desmids, fourteen taxa were belonging to family Desmidiaceae and seven taxa to family Closteriaceae. The genus Cosmarium exhibited high species diversity (11 species), followed by the genus Closterium (7 species) of the total diversity of study area. It has been observed that water of this wetland was slight alkaline (pH 7.7-8.0), which may cause low diversity of desmids in this wetland. According to previous reports (117,127) the acidic condition of water favors more growth of desmids in comparison to alkaline water.
The comparison of observation of present study with other available reports from India (9,12,(35)(36)(37)(38)(39)(40)(41)(42)(43) indicates low diversity of desmids in the study area. This may be due to different habitat nature and water quality conditions. As high desmid diversity has been observed from the wetlands habitat having abundant growth of macrophytes (128) and Sphagnum bog carpets (129). The desmid taxa, C. acerosum, C. dianae, C. moniliforme and E. platycerum were observed to be widely distributed in different water bodies of India (9,12,(35)(36)(37)(38)(39)(40)(41)(42)(43)128) and results of current study further advocate the cosmopolitan nature of distribution of these taxa. According to reports (130), C. acerosum is a high nutrient tolerant species which indicates the eutrophic nature of water. It was also reported that Closterium spp. were dominated in polluted water (131). From the results of present study, it is suggested that the continue bio-monitoring studies with holistic assessment of water quality conditions are required to develop strategies and water quality improvement programmes for this wetland.

Conclusion
In this study, the desmid flora of the Ropar wetland, Punjab (India) has been studied for the first time. All species recorded in this work are new records for study area as well as from Punjab. The habitat of this wetland does not support luxuriant growth of desmids due to alkaline nature of water. A high nutrient tolerant taxon i.e. C. acerosum has also observed during this study which may be the first indication towards the deterioration of water of this wetland.
The present study provides more information about the biological diversification of this wetland and will be helpful in future for further limnological analysis.