The shallow (1.5 m) Pulicat Lagoon in India supports a variety of migratory ... associated with India's lagoonal ecosystem are ... on existing natural resources.
# Springer 2005
Wetlands Ecology and Management 13: 69–72, 2005.
Factors influencing flamingo (Phoenicopterus roseuis) distribution in the Pulicat Lagoon ecosystem, India D. Asir Ramesh and S. Ramachandran Integrated Coastal Zone Management Training Program, Institute for Ocean Management, Anna University, Chennai-25, India; *Author for correspondence (e-mail: asiramesh@yahoo.com; phone: 91-44-22200158) Received 7 December 2002; accepted in revised form 10 July 2003
Key words: Bird density, Flamingo, Lagoonal systems, Population distributions, Water depth
Abstract The shallow (1.5 m) Pulicat Lagoon in India supports a variety of migratory birds (125 species), especially flamingos and storks. Flamingo populations in this area are dominated by Phoenicopterus roseuis, and they are densely distributed in shallow areas and fringes of the lake where the water level is below 40 cm. Eighteen flamingo groups are distributed around the lagoon with 750 individuals per group. Flamingo populations are greatest in places where fish, algal, and benthic faunal biomass are highest. Physiological adaptations and morphology of flamingo are important criteria for selecting feeding locations.
Introduction Birds are an important and major migratory biological component of coastal wetlands. Coastal lagoons support significant migratory bird populations and provide nesting, breeding, and resting grounds for these birds. Avian population density and diversity depend on available food and shelter resources. India has two major coastal lagoons, Chilka and Pulicat lagoons, and these lagoons attract a variety of migratory bird populations. The most important common migratory birds associated with India’s lagoonal ecosystem are herons, storks, flamingos, and pelicans. Of the over 2094 kinds of birds occurring on the Indian subcontinent, 344 are migrants, coming mostly from the Northern Eurasian region. Pulicat Lagoon covers more than 250 km2. Lake size and abundance of invertebrates are the main factors contributing to the distribution of bird populations (Hurlbert 1991). Water depth is also important, because it regulates the bird’s feeding capacity
over the benthic fauna (except diving birds) (Erwin et al. 1994). Vegetation distribution is also an important criterion for avian distribution and diversity in coastal wetlands (Mulyani and DuBowy 1993), with areas of seagrass and seaweeds being potential sites of greatest benthic faunal distribution. Bird populations globally are threatened by habitat alteration due to anthropogenic activities and natural changes. In India, natural changes include decreasing water depths due to uplifting processes, and anthrophogenic activities include the conversion of lagoons into industrial land (agriculture and aquaculture come under the Industries Act). During the No Impact Zone Studies on the Pulicat Lake ecosystem (funded by Department of Ocean Development, Government of India), Phoenicopterus roseuis was found to be distributed sporadically in the more shallow areas of the lake. The objective of the current study was to determine the reason for density and distributional variations of P. roseuis within the lagoon.
70 Methods
Results
Pulicat Lake is an extensive brackish water coastal lagoon with extensive marshes and fresh-to brackish-water swamps to the north. Pulicat Lagoon is the second largest saltwater lagoon in India and is located between 13 250 –13 550 N and 80 030 –80 190 E; 45 km north of Madras in the Nellore district of Andhra Pradesh and extending into the Chengalpattu district of Tamilnadu. Total area of the lake during 1999 was 281 km2 (Landsat1999 imagery). Inputs to the lake include the Arani and Kalangi rivers. Presently, there is only one outlet at the southern end of the lake, whereas during the 1980s, there were three outlets (one on the northern, middle, and southern sides of the lake). The reduction in outlets is an indication of sea level fall in this region. Annual rainfall in this area is 1100 mm/yr (10 yr average). Salinity in the lake ranges between between 27 and 44 ppt. Maximum salinity concentrations occur in tidal pools within the marshy area. Water temperatures of this system range between 25 C and 35 C. Water quality of the lake, including physical, chemical, and biological parameters, have been reported by Ramachandran et al. (1999). Pulicat Lake’s surrounding villagers live in close harmony with the birds, and the birds are adjusted to the traditional activities of fishing, agriculture, salt manufacturing, etc. Other important migratory birds in this area include pelicans, painted storks, open-billed storks, gray herons, cormorants, white ibises, spoonbills, egrets, reef herons, spot-billed ducks, shovellers, pintails, and sandpipers. Pulicat Lake was divided into four regions based on existing natural resources. Algae, zooplankton, meiofauna, prawn, and fin-fish data of the four regions were arrived at by averaging 10 replicated samples over the 3 years of study. Group counting and photography were used in counting the number of birds in flocks of migratory birds. Group counting was done by counting the number of birds distributed in 10 m2 quadrats. In addition, Panasonic digital video images were taken, and the number of standing birds covered in each frame were counted. Correlations between the various biological groups (algae, zooplankton, meiofauna, prawn, and fin-fish ) and the total number of flamingos in each region were examined to determine if there were any relationships.
The principal migratory bird species visiting the Pulicat Lake ecosystem is P. roseuis (flamingo). The average flamingo population density in this area is 182-individuals/km2 for a total population of 50,000 flamingos. Distribution of flamingos varied in relation to the different regions of the lake. The central portion of the lake averaged eight flocks of flamingos during the study and a total population of 12,000 birds. On the southern and northwestern sides of the lake, 6 and 12 flocks were recorded, respectively, with an average total population of 2000 and 2200, respectively. Flamingoes arrive at the lake during October, coming from Great Rann of Kutch (breeding places) and leave during April. Flamingo population densities are positively correlated with algal density (C ¼ 0.4593), zooplankton (C ¼ 0.6519), meiobenthos (C ¼ 0.9123), macrofauna (C ¼ 0.9636), fin-fish (C ¼ 0.6528), and prawn (C ¼ 0.8435). Algal density and benthos are significantly higher on the landward margins of the lake, and this is where the greatest number of Phoenicopterus sp. are found. Eighteen algal species have been recorded from the algal mats, including Halophila sp. and Halodule sp. The algae filter nutrients from the water and support the animal population by providing shelter and food. A total of 88 zooplankton species were recorded from this area. Meroplankters dominate (51%) the zooplankton catch and are an important food of the flamingos. Eighty-nine species of meiofaunal organisms were recorded from the lake, they also represent an important food for flamingoes. Polychaetes and nematodes are the dominant meiofaunal groups, followed by isopods and amphipods. Large numbers of fish larvae are distributed throughout the lake due to the shallowness and calmness of the lagoon. Distributional variation of animals and algae within the lake is presented in Table 1.
Discussion Flamingoes are the most important migratory bird in Indian coastal wetlands and are physiologically adapted to utilize shallow saltwater areas and lagoons. Flamingos can excrete excess salt through salt glands in their nostrils, and they can manage
71 Table 1. Quantitative biological resources of Pulicat Lake, India. Components
SS
CS
NES
NWS Unit
Phytoplankton 28,600 32,850 Macroalgae 139 450 Productivity Zooplankton Meiofauna
985 53 1080
Macrofauna Fin-fish
220 67
Prawn Migratory birds
80 2
1,40,400 16,800 Cells/liter 230 85 g wet weight/m2 1131.5 1387 789 g C/m2/yr 82 88 12 Number/liter 2800 2100 520 Number/ 10 cm2 482 350 180 g/m3 120 140 40 g wet weight/m2 132 109 40 g wet weight/m2 12 5 2 Number/ 10 m2
SS ¼ south side, CS ¼ central side, NES ¼ northeastern side, NWS ¼ northwesternside.
their body heat by curling their leg from the water (www.wkonline.com). Flamingos wade in shallow marshy areas and filter feed by stamping their webbed feet to stir up food from the bottom. They sweep their heads from side to side on the bottom with their bills hanging upside-down and facing backward in the water to capture prey. Their fringed tongue lamellae filter out food, and water is passed back out of the bill. Gut content analysis of this species indicate that blue–green and red algae, diatoms, larval and adult forms of small insects, crustaceans, molluscs, and small fishes make up the main diet of flamingos. Multiple regression analysis ( ¼ 0.05) relating bird use and habitat characteristics showed that bird species richness increased with the species richness of submerged vegetation, and is negatively correlated with emergent or exposed vegetation (Mulyani and DuBowy 1993). The shallow, calm areas of the lagoon have a high diversity and richness, whereas the high stress zone (southern and northwestern sides of the lagoon where agriculture, aquaculture, saltpan production, industrial development, shell mining, and shell processing activities are common) has the lowest diversity and density (Lehman and Tunnell 1993). Meroplankton constituted an important component of the zooplankton community in the lagoon (Philips et al. 1995). Lagoons function as important nursery areas for certain marine organisms (Andrade 1989), and they play an important role in the export of
planktonic biomass to adjacent marine waters (Ambrogi et al. 1989). Dense meiofaunal populations have been reported in organic-rich sediment areas (Tsutsumi et al. 1990). Meiofauna is high in density where the tidal influence is maximal (Ansari et al. 1984). Shallow coastal areas have high value as feeding grounds and nursery areas for many commercially important fish species (Isaksson and Phil 1992). Depth and sediment structure seem to be the main factors that control the composition and quantity of macrobenthic crustacean fauna (Garnacho and Aguirrezabalaga 1992). Scylla sp. populations are higher in seagrass and algal bed areas (Chandrasekaran and Natarajan 1994). Algal mats are suitable feeding and nursery grounds for crabs. Organic-rich mud, regular tidal flushing, and algal beds are also attractive to prawn populations. Acknowledgements The authors thank the ICMAM Project Directorate of the Department of Ocean Development (DOD), Government of India, for funding the No Impact Zone Studies on the Pulicat Lake ecosystem. References Andrade J.P. 1989. The flatfishes of the Ria Formosa, southern Portugal: results of a three-year survey. In: Ros J. (ed.), Topics In Marine Biology, Proceedings of the 22nd European Marine Biology Symposium 53(2–3), 671–676. Ansari Z.A., Ingole B.S. and Parulekar A.H. 1984. Macrofauna and meiofauna of two sandy beaches at Mombasa, Kenya. Indian Journal of Marine Science 13(4): 24–32. Ambrogi R., Ferrari I. and Geraci S. 1989. Biotic exchange between river, lagoon and sea: the case of zooplankton in the Po Delta. In: Ros J. (ed.), Topics In Marine Biology, Proceedings of the 22nd European Marine Biology Symposium, 53(2–3), pp. 601–608. Chandrasekaran V.S. and Natarajan R. 1994. Seasonal abundance and distribution of seeds of mud crab Scylla serrata in Pichavaram mangrove, Southeast India. Journal of Aquaculture in the Tropics 9(4): 343–350. Erwin R.M., Hatfield J.S., Howe M.A. and Klugman S.S. 1994. Water bird use of salt marsh ponds created for open marsh water management. Journal of Wildlife Management 58(3): 516–524. Garnacho E. and Aguirrezabalaga F. 1992. Spatial and temporal changes of macrobenthic crustacean community structure along a depth gradient in a sub littoral marine soft bottom exposed area. In: Proceedings of the First European
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