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ABSTRACT The seasonal effects of nutrient loading from migratory waterfowl on water and the successive changes of the aquatic ecosystem based on each biomass of phytoplankton, zooplankton and submerged macrophytes were surveyed in Tsubasa Pond, Yonago Waterbird Sanctuary, Japan. The pond’s water quality gradually deteriorated with the influx of migratory waterfowl. The concentration of total nitrogen corresponded rapidly with waterfowl biomass. Peak concentrations of total phosphorus and chlorophyll a (Chl.a) were observed about one month later when the migratory waterfowl had flown away. After one month, the peak concentration of Chemical Oxygen Demand (CODMn) appeared. Thus, the water quality of the pond had gotten worst after the waterfowl had flown away. Then, decrease of Chl.a concentration and increase of zooplankton density were observed in spring. In summer, the population of a submerged macrophyte increased temporarily and water quality recovered. These results indicated that the primary producer in the bird sanctuary pond alternated from phytoplankton to submerged macrophyte in one year
Journal of Water and Environment Technology, Vol. 8, No.4, 2010 Address correspondence to Masako Nakamura, The United Graduate School of Agricultural Sciences, Tottori University, Email: himasako4713@yahoo.co.jp Received May 15, 2010, Accepted August 24, 2010. - 393 - Seasonal Changes of Shallow Aquatic Ecosystems in a Bird Sanctuary Pond Masako NAKAMURA*, Tohru YABE**, Yuichi ISHII**, Kaname KAMIYA***, Morihiro AIZAKI**** *The United Graduate School of Agricultural Sciences, Tottori University, 4-101 Koyama-Minami, Tottori-City, Tottori 680-8553, Japan **Environmental Biology Division, National Institute for Environmental Studies, 16-2 Onogawa, Tsukuba-City, Ibaraki 305-8506, Japan ***Nakaumi Waterbird International Exchange Fund Foundation, Yonago Waterbird Sanctuary, 665, Hikonashinden, Yonago-City, Tottori, 683-0855, Japan ****Faculty of Life and Environmental Science, Shimane University, 1060 Nishikawatsu-cho, Matsue-City, Shimane 690-8504, Japan ABSTRACT The seasonal effects of nutrient loading from migratory waterfowl on water and the successive changes of the aquatic ecosystem based on each biomass of phytoplankton, zooplankton and submerged macrophytes were surveyed in Tsubasa Pond, Yonago Waterbird Sanctuary, Japan. The pond’s water quality gradually deteriorated with the influx of migratory waterfowl. The concentration of total nitrogen corresponded rapidly with waterfowl biomass. Peak concentrations of total phosphorus and chlorophyll a (Chl.a) were observed about one month later when the migratory waterfowl had flown away. After one month, the peak concentration of Chemical Oxygen Demand (COD Mn ) appeared. Thus, the water quality of the pond had gotten worst after the waterfowl had flown away. Then, decrease of Chl.a concentration and increase of zooplankton density were observed in spring. In summer, the population of a submerged macrophyte increased temporarily and water quality recovered. These results indicated that the primary producer in the bird sanctuary pond alternated from phytoplankton to submerged macrophyte in one year. Keywords: migratory waterfowl, seasonal changes of water quality, shallow aquatic ecosystems. INTRODUCTION Waterfowl such as Anseriformes (geese, swans, and wild ducks), cormorants, egrets, coots, gulls and other seabirds have various impacts on water environment. Especially, the effects of waterfowl on water quality are important for aquatic ecosystem and there have been much studies on that (Gould and Fletcher, 1978; Bédard et al., 1980; Portnoy, 1990; Bales et al., 1993; Dobrowolski et al., 1993; Baxter and Fairweather, 1994; Manny et al., 1994; Marion et al., 1994; Enari and Shibasaki, 1995; Smith and Craig, 1995; Gwiazda, 1996; Kitchell et al., 1999; Hahn et al., 2007; Nakamura et al., 2010). Anseriformes are typically migrating waterfowl to Japan in winter. They affect lake and pond ecosystems greatly because they have big bodies and form in large groups (Jefferies, 2000). Most Anseriformes are herbivorous and tend to feed in paddy fields in Japan (Takeichi and Arita, 1994; Yamamoto et al., 1999; Shimada, 2002). In case their feeding and roosting places are different, they are considered to work as transporters of nutrients from the feeding place to the roosting place. Thus, it is considered that Anseriformes play a role in the purification of feeding places (Gere and Andrikovics, 1992; Tamisier and Boudouresque, 1994; Yamamuro et al., 1998). On the other hand, they play a role in the eutrophication of roosting places. Indeed, eutrophication was Journal of Water and Environment Technology, Vol. 8, No.4, 2010 - 394 - found in Anseriformes roosting area, and it was considered to occur due to the addition of nutrients from migratory Anseriformes (Enari and Shibasaki, 1995; Ogawa et al., 1997; Pettigrew et al., 1998; Kitchell et al., 1999; Olson et al., 2005). However, most of these studies were carried out only during the period of stay of migratory Anseriformes. Only Olson et al. (2005) have performed a short period study after the Anseriformes flew away. In this study, the first objective is to clarify the seasonal effects of nutrient loading from waterfowl on water throughout the year in a bird sanctuary pond. The second is to discuss the successive changes of the aquatic ecosystem based on each biomass of phytoplankton, zooplankton and submerged macrophytes in the pond. MATERIALS AND METHODS Study Site This study was conducted in Tsubasa pond in Yonago Waterbird Sanctuary that is home to many Anseriformes, and is the largest place for wintering tundra swans (Cygnus columbianus) in western Japan. Yonago Waterbird Sanctuary, located in Tottori Prefecture, Japan (35º 26” N, 133º 172” E), was constructed after partial reclamation on Lake Nakaumi in 1994. The sanctuary consists of Tsubasa pond and surrounding a reed wetland (Fig. 1). The pond area is 17 ha with an average water depth of 60 cm, and a volume of 102,000 m 3 . Water temperature varied from 2ºC to 30ºC, and salinity varied from 3 psu to 8 psu. The inflow water to Tsubasa Pond is basically rainfall, and the outflow water to Lake Nakaumi is through the overflow of artificial drain ditch. Observation, Sampling and Analysis The number of waterfowl was counted identifying their species at the observation center shown in Fig. 1. Observations were conducted between two and four times in a month from March 1999 to September 2000, and the total number of observations was forty. The total waterfowl weight (TWW) in an observation was calculated as follows; TWW = Σ NB k × AW k (1) where, n is the number of species in an observation, while NB k and AW k are the number of birds of each species and the average weight of each species, respectively. It was found out that avian basal metabolism is proportional to the body weight (Nagy et al., 1999), and birds excrete at a rate of about 20% of basal metabolism (Kurechi and Otsu, 1983). Hence, in this study, the excretion was evaluated by using the body weight study. Water samples were collected at the pond shore as shown in Fig. 1 so as not to disturb the waterfowl migration. The samples were placed in polypropylene bottles, immediately cooled with ice and taken to the laboratory. After subsamples for total nitrogen (TN), total phosphorus (TP) and chemical oxygen demand (COD Mn ) measurements were taken, the remaining water sample was filtered through a glass fiber filter (GF/F, Whatman, USA). The solid samples remaining on filters were used for Chlorophyll-a (Chl.a) measurement. Samples for TN and TP concentrations were determined with a continuous-flow k = 1 n Journal of Water and Environment Technology, Vol. 8, No.4, 2010 - 395 - N Lake Nakaumi 0m 200m canal The observetion center ditch Tsubasa pond 36°E 133°N ■ 04km Japan Sea Lake Nakaumi 133°00″ 133°41″ 35°31″ Lake Shinjiko ■ ■ ■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ▼ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■■ ■ ■ ■ ■ ■■■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■■ ■ ■ ■■ ■ ■ ■ ■ ■ NN Lake Nakaumi 0m 200m 0m 200m canal The observetion center ditch Tsubasa pond 36°E 133°N ■ 36°E36°E 133°N133°N ■ 04km Japan Sea Lake Nakaumi 133°00″ 133°41″ 35°31″ Lake Shinjiko ■ ■ ■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ▼ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■■ ■ ■ ■ ■ ■■■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■■ ■ ■ ■■ ■ ■ ■ ■ 04km Japan Sea Lake Nakaumi 133°00″ 133°41″ 35°31″ Lake Shinjiko 04km Japan Sea Lake Nakaumi 133°00″133°00″ 133°41″133°41″ 35°31″35°31″ Lake Shinjiko ■ ■ ■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ▼ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■■ ■ ■ ■ ■ ■■■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■■ ■ ■ ■■ ■ ■ ■ ■ ■ ■ ■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ▼ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■■ ■ ■ ■ ■ ■■■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■■ ■ ■ ■■ ■ ■ ■ ■ ■■■ Fig.1 - Location of Yonago Waterbird Sanctuary and Tsubasa Pond, with water sampling point (●), Shaded area shows the land and dotted area shows the reed bed analyzer (AAII, Bran+Luebbe, UK) after alkaline peroxydisulfate digestion and peroxydisulfate digestion, respectively (APHA et al., 1998). Samples for COD Mn was measured by the potassium permanganate method (JISC, 1998) while Chl.a concentration was measured by the SCOR/UNESCO method with methanol extraction (Marker et al. 1980). Phytoplankton and zooplankton samples were collected twice a month from March to November 1999 from the water surface. Phytoplankton with unfiltered water were fixed with a glutaraldehyde solution. Samples of zooplankton were collected using a plankton net (NXX25) and fixed in the same manner as for phytoplankton. Plankton genera were identified and counted under a microscope (BH2-PFK-1, OLYMPUS, Japan) according to Mizuno (1977) and Akiyama (1996). The standing crop of dominant submerged macrophytes was surveyed every month from March to November 1999. The aboveground parts were collected, using a 15 cm × 15 cm quadrate, from four sites each month. Collected samples were dried at 80ºC for 48 hours and the dry weights were measured. RESULTS AND DISCUSSION Seasonal Change of TWW At Tsubasa Pond, a maximum of about 500 geese, 1,000 swans and 10,700 wild ducks migrated during the study period. Among the waterfowl observed in the study pond, the geese, swans, ducks, grebes, cormorants, herons, egrets, coots, snipes, plovers and gulls are generally known to excrete in water. The sum of the weight of each species during the surveillance period was calculated. Then, the 10 species of cormorants, geese, swans, and ducks, accounted for more than 98% of TWW during the surveillance period. Total weight of each species and its ratio to TWW for 10 dominant species are shown in Table 1. As a result of the observations, seasonal change of TWW in Tsubasa Pond was divided into four terms : term S 3 (March), migrating waterfowl flying to the north; term A (April - August), absence of migrating waterfowl using the pond; term S 1 (September), a large amount of migrating waterfowl arriving from the north; term S 2 (October - February), waterfowl using the pond as a wintering place. Thus, migratory waterfowl stayed Journal of Water and Environment Technology, Vol. 8, No.4, 2010 - 396 - Table 1 - Total weight of each species and its ratio to the sum of TWW for 10 dominant species. Average weights of each species were the average of minimum and maximum weight data (Wild Bird Society of Japan, Ehime Branch, 1995; Higuchi et al., 1996) Species name Scientific name A sum of each sp ecies weight (kg) Ratio of species to TWW (%) Tundra Swan Cygmus columbianu s 34,242 34.7 Pochard Ayth ya ferina 16,305 16.5 Tufted Duck Aythya. fuligula 11,701 11.9 Pintail Anas acuta 10,410 10.5 Great Cormorant Phalacrocorax carbo 7,543 7.6 Mallard Anas platyrhyncho s 7,259 7.4 Wigeon Anas penelo pe 2,930 3.0 White-fronted Goose Anser albifrons 2,689 2.7 Spot-billed Duck Anas poecilorh yncha 2,274 2.3 Teal Anas crecca 1,509 1.5 1999 2000 MSAMJ J AS OND JFM AMJJA Total waterfowl weight (kg) AS 1 S 2 S 3 S 3 A S 1 0 2500 5000 7500 10000 Month 1999 2000 MSAMJ J AS OND JFM AMJJAMSAMJ J AS OND JFM AMJJA Total waterfowl weight (kg) AS 1 S 2 S 3 S 3 A S 1 AS 1 S 2 S 3 S 3 A S 1 AS 1 S 2 S 3 S 3 A S 1 0 2500 5000 7500 10000 Month Fig.2 - Seasonal change of TWW in Tsubasa Pond. Shaded area indicates a period when migratory waterfowl were staying in the pond mainly in the pond at S 2 . The seasonal change of TWW is shown in Fig. 2. TWW was 5,000 kg at the beginning of the study period. It decreased rapidly in March 1999 (term S 3 ) because most waterfowl had flown to the north. It was below 400 kg in May 1999, during term A. TWW increased in September 1999, in term S 1 , with the arrival of the migratory waterfowl and sometimes reached to about 7,500 kg in term S 2 . Since March 2000, it decreased rapidly and was less than 400 kg in April 2000, which was term A again. Seasonal Changes in Water Quality The seasonal changes in water quality are shown in Fig. 3. TN concentration of 3.0 mg/L was observed at the beginning of the study period, in term S 3 , and decreased Journal of Water and Environment Technology, Vol. 8, No.4, 2010 - 397 - TN concentration (mg l -1 )COD concentration (mg l -1 ) Chl.a concentration (μg l -1 ) a) TN b) TP c) COD d) Chl.a 0 25 50 75 100 1999 2000 MAMJJA SOND JFM AMJJA S TP concentration (mg l -1 ) S 3 A S 1 S 2 A S 3 S 1 A S 1 S 2 A S 3 S 1 0.0 0.1 0.2 0.3 0.4 0.5 0 1 2 3 4 5 6 0 40 80 120 160 1999 2000 MAMJJA SOND JFM AMJJA S Month Month TN concentration (mg l -1 )COD concentration (mg l -1 ) Chl.a concentration (μg l -1 ) a) TN b) TP c) COD d) Chl.a 0 25 50 75 100 1999 2000 MAMJJA SOND JFM AMJJA S 1999 2000 MAMJJA SOND JFM AMJJA S TP concentration (mg l -1 ) S 3 A S 1 S 2 A S 3 S 1 A S 1 S 2 A S 3 S 1 S 3 A S 1 S 2 A S 3 S 1 A S 1 S 2 A S 3 S 1 A S 1 S 2 A S 3 S 1 A S 1 S 2 A S 3 S 1 0.0 0.1 0.2 0.3 0.4 0.5 0 1 2 3 4 5 6 0 40 80 120 160 1999 2000 MAMJJA SOND JFM AMJJA S Month 1999 2000 MAMJJA SOND JFM AMJJA S Month Month Fig.3 - Seasonal changes in water quality of Tsubasa Pond. Shaded area indicates a period when migratory waterfowl were staying in the pond during term S 3 to a low value of 0.7 mg/L in July, in term A. TN concentration increased rapidly to a maximum value of 5.8 mg/L which was observed in December 1999, during term S 2 . Then it started to decrease in the latter part of term S 2 (Fig. 3-a). TP concentration of 0.33 mg/L was observed at the beginning of the study period, in term S 3 , and subsequently decreased to 0.05 mg/L in July (term A). In terms S 1 and S 2 , TP concentration increased and showed a maximum value of 0.38 mg/L in March 2000, in term S 3 (Fig. 3-b). COD Mn concentration of 12.6 mg/L was observed at the beginning of the study period, in term S 3 and showed little fluctuation. In the latter part of term S 2 and S 3 , COD Mn concentration increased and showed a maximum value of about 100 mg/L in April 2000, in term A (Fig. 3-c). Chl.a concentration of 95.9 mg/L was observed at the beginning of the study period, in term S 3 , and decreased to about 10 mg/L in June 1999, in term A. Chl.a concentration showed a peak in the beginning of term S 2 and then it increased rapidly. Then, it showed a maximum peak of 153 mg/L in March 2000, in term S 3 (Fig. 3-d). (mg/L) (mg/L) (mg/L) (µg/L) Journal of Water and Environment Technology, Vol. 8, No.4, 2010 - 398 - 0 25 50 75 100 0 20000 40000 60000 80000 Chl.a zoo plankto n submerged macrop hyte Chl.a concentration（µg/L） Zooplankton density (ind./L） Submerged macrophyte（mg DW/m 2 ） 1999 MMJJASONA a 0 25 50 75 100 0 20000 40000 60000 80000 Chl.a zoo plankto n submerged macrop hyte Chl.a concentration（µg/L） Zooplankton density (ind./L） Submerged macrophyte（mg DW/m 2 ） 1999 MMJJASONAMMJJASONA aa Fig.4 - Seasonal changes of Chl.a concentration, zooplankton density and aboveground biomass of a dominant submerged macrophyte in Tsubasa Pond between March and November 1999 Seasonal Changes of Plankton and Submerged Macrophyte The genera of Anabaena, Merismopedia, Oscillatoria, Melosira, Cyclotella, Navicula, Gyrosigma, Chlamydomonas, Synura and Euglena were observed during the study period. The dominant genera were Euglena in March and Cyclotella in October. Eight genera of zooplankton and protozoa such as Difflugia, Arcella, Stylonychia, Brachionus, Keratella, Monostyla, Asplanchna and Mesocyclops were observed. A high density of zooplankton was observed at the end of April and May, and the dominant genera were Keratella and Difflugia, respectively. One of the submerged macrophytes, Potamogeton pectinatus, dominated and covered in the pond during summer and autumn. The other submerged macrophytes, Najas marina, Zannichellia palustris, Ruppia maritima and Chara sp., were also observed in summer (Kamiya and Kunii, 2001). Seasonal changes of Chl.a concentration, zooplankton density and aboveground biomass of a dominant submerged macrophyte, P. pectinatus, are shown in Fig. 4. The concentration of Chl.a increased rapidly in March, and zooplankton density showed peaks in April and June. The zooplankton density increased rapidly after the decrease in Chl.a concentration. The aboveground biomass of P. pectinatus was observed first in May and covered the pond’s surface between July and August. The biomass showed a peak in August. Effects of Waterfowl on Water Quality and Successive Seasonal Changes of Shallow Aquatic Ecosystem Relative values of water qualities and some ecosystem components in Tsubasa Pond were calculated using monthly average data and the values are shown in Fig. 5. The TN observed to have their perks in term S 3 and A, respectively. When the worst water quality was observed in term S 3 after the waterfowl flew away, a peak was observed in the order of TP and COD Mn . In term A, when Chl.a concentration decreased rapidly, zooplankton proliferated. Subsequently in this term, water quality was maintained in a better condition for submerged macrophytes and P. pectinatus prospered temporarily. It was considered that the primary producer changed from phytoplankton to submerged Journal of Water and Environment Technology, Vol. 8, No.4, 2010 - 399 - TWW TN TP Chl.a COD Submerged macrophyte zooplankton 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 0 25 50 75 10 0 Relative value (-) S 3 AS 3 A S 1 S 2 AMA SOMJJ NDJ F M Month TWW TN TP Chl.a COD Submerged macrophyte zooplankton 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 0 25 50 75 100 0 25 50 75 10 0 0 25 50 75 10 0 Relative value (-) S 3 AS 3 A S 1 S 2 S 3 AS 3 A S 1 S 2 AMA SOMJJ NDJ F M Month Fig.5 - Relative values of water quality parameters and some ecosystem components in Tsubasa Pond (term S 3 : March, term A: April - August, term S 1 : September, term S 2 : October - February) macrophyte between term S 3 and A. Then sunlight easily seemed to reach the pond bottom with a decrease of plankton biomass. The shallowness of the whole pond might have caused such a dynamic change of primary producer. The pond alternated between submerged-macrophytes-dominant clear-water state and phytoplanktons-dominant turbid-water state in one year. It was found that there is a difference in the case of catastrophic changes reported by Scheffer et al. (2001) and this study, i.e. in a bird sanctuary pond aquatic ecosystem changes cyclicly. ACKNOWLEDGMENTS We would like to thank the staffs and the volunteers of Yonago Waterbird Sanctuary, especially K. Kirihara, for counting the waterfowl. Special thanks are forwarded to Professor S. Otani of the Faculty of Education, Shimane University, for his assistance in the determination of phytoplankton. We thank K. Fujioka, T. Kuwabara, A. Takahashi and the other 1999 - 2001 graduates of Environmental Ecology Engineering Laboratory, Faculty of Life and Environmental Science, Shimane University for conducting the sampling and chemical analyses. Also, we are indebted to General Manager N. Nakajima, Senior Researcher M. Tamaoki and the other members of Environmental Biology Division, National Institute for Environmental Studies for improving our English and for making valuable comments on drafts. Journal of Water and Environment Technology, Vol. 8, No.4, 2010 - 400 - REFERENCES APHA, AWWA and WEF (1998) Standard Methods for the examination of water and wastewater, 20th edition, APHA, Washington. Akiyama M. (ed) (1996). Algae in Lakes Shinjiko and Nakaumi, Research Circle of Algae in Lakes Shinjiko and Nakaumi, Shimane. (in Japanese) Baxter S. G. and Fairweather G. P. (1994). Phosphorus and nitrogen in wetlands with and without egret colonies, Australian Journal of Ecology, 19, 409-416. Bales M., Moss B., Phillips G., Iirvine K. and Stansfield J. (1993). The changing ecosystem of a shallow, brackish lake, Hickling Broad, Norfolk, U.K. II. Long-term trends in water chemistry and ecology and their implications for restoration of lake, Freshwater Biology, 29, 141-165. Bédard J., Therriault C. J. and Bérubé J. (1980). Assessment of the importance of nutrient recycling by seabirds in the St. Lawrence Estuary, Canadian Journal of Fisheries and Aquatic Sciences, 37, 583-588. Dobrowolski A. K., Kozakiewicz A. and Leźnicka B. (1993). The role of small mammals and birds in transport of matter through the shore zone of lakes, Hydrobiologia, 251, 81-93. Enari K. and Shibazaki T. (1995). Water pollution by waterfowl migration and the purification measures, Enviromental Technology, 24(7), 392-396 (in Japanese). Gere G. and Andrikovics S. (1992). Effects of waterfowl on water quality, Hydrobiologia, 243/244, 445-448. Gould J. D. and Fletcher R. M. (1978). Gull droppings and their effects on water quality, Water Research, 12, 665-672. Gwiazda R. (1996). Contribution of water birds to nutrient loading to the ecosystem of mesotrophic reservoir, Ekologia Polska, 44(3-4), 289-297. Hahn S., Bauer S. and Klaassen M. (2007). Estimating the contribution of carnivorous waterbirds to nutrient loading in freshwater habitats, Freshwater Biology, 52, 2421-2433. Higuchi H., Morioka H., Yamagishi S. (ed) (1996). The encyclopedia of animals in Japan, Vol.3, Birds 1 (in Japanese), Heibonsha, Tokyo. Jefferies L. R. (2000). Allochthonous inputs: integrating population changes and food-web dynamics, Tree, 15(1), 19-22. JISC (1998). JIS K 0102:1998 Testing methods for industrial wastewater. JSA, Tokyo. Kamiya K. and Kunii H. (2001). Influence of waterfowl herbivory on the brackish submerged macrophyte (Potamogeton pectinatus L.), Bulletin of Water Plant Society, 72, 33-35 (in Japanese). Kitchell F. J., Schindler E. D., Herwig R. B., Post M. D., Olson H. M. and Oldham M. (1999). Nutrient cycling at the landscape scale: The role of diel foraging migrations by geese at the Bosque del Apache National Wildlife Refuge, New Mexico, Limnology and Oceanography, 44(3), 828-836. Kurechi M. and Otsu M. (1983). Estimate of the carrying capacity of the wintering geese in Japan (1) Energy requirement of White-fronted Geese Anser albifront, Bulletin of Applied Ornithology Contents, 3, 3-5 (in Japanese). Manny A. B., Johnson C. W. and Wetzel G. R. (1994). Nutrient additions by waterfowl to lake and reservoirs: predicting their effects on productivity and water quality, Hydrobiologia, 279/280, 121-132. Marion L., Clergeau P., Brient L. and Bertru G. (1994). The importance of avian-contributed nitrogen (N) and phosphorus (P) to Lake Grand-Lieu, France, Journal of Water and Environment Technology, Vol. 8, No.4, 2010 - 401 - Hydrobiologia, 279/280, 133-147. Marker A. F. H., Nusch A. E., Rai H. and Riemann B. (1980). The measurement of phyotosynthetic pigments in freshwaters and standardization of method : conclusions and recommendations, Archiv für Hydrobiologie Ergebnisse der Limnologie, 14, 91-106. Mizuno T. (1977). Illustrations of the freshwater plankton of Japan, Revised Edition (in Japanese), Hoikusha Publishing, Osaka. Nagy A. K., Girard A. I. and Brown K. T. (1999). Energetics of free-ranging mammals, reptiles, and birds, Annual Review of Nutritional, 19, 247-277. Nakamura M., Yabe T., Ishii Y., Kido K. and Aizaki M. (2010). Extreme eutrophication in a small pond adjacent to a forest colonized by Great Cormorants (Phalacrocorax carbo), Japanese Journal of Limnology, 71(1), 19-26 (in Japanese). Ogawa H., Kobayashi S., Nakayama K., Jin K., Igarashi S., Mikami H., Sakata K. and Tsuzuki T. (1997). Uric acid concentration originated from waterfowl in the water of Lake Miyajimanuma, Report of the Hokkaido Institute of Public Health, 47, 112-114 (in Japanese). Olson H. M., Hage M. M., Binkley D. M. and Binder R. J. (2005). Impact of migratory snow geese on nitrogen and phosphorus dynamics in a freshwater reservoir, Freshwater Biology, 50, 882-890. Pettigrew T. C., Hann J. B. and Goldsborough G. L. (1998). Waterfowl feces as a source of nutrients to a prairie wetland: responses of microinvertebrates to experimental additions, Hydrobiolgia, 362, 55-66. Portnoy W. J. (1990). Gull contributions of phosphorus and nitrogen to a Cape Cod kettle pond, Hydrobiologia, 202, 61-69. Scheffer M., Carpenter S., Foley A. J., Folke C. and Walker B. (2001). Catastrophic shifts in ecosystems, Nature, 413, 591-596. Shimada T. (2002). Daily activity pattern and habitat use of Greater White-fronted Geese wintering in Japan: factors of the population increase, Waterbirds, 25(3), 371-377. Smith S. J. and Johnson R. C. (1995). Nutrient inputs from seabirds and humans on a populated coral cay, Marine Ecology Progress Series, 124, 189-200. Takeichi Y. and Arita I. (1994). Choice of daily flight routes and distributions of feeding areas of Tundra Swans in Lake Nakaumi and Nogi Plain, Eco-planning Reseach Annual Report, 2, 55-65 (in Japanese). Tamisier A. and Boudouresque C. (1994). Aquatic bird populations as possible indicators of seasonal nutrient flow at Ichkeul Lake, Tunisia, Hydrobiologia, 279/280, 149-156. Wild Bird Society of Japan, Ehime Branch (ed) (1995). Illustrated Book of Wild Birds in Ehime Prefecture, Habataki, Revised Edition (in Japanese), The ehime shinbun, Ehime. Yamamoto H., Ohata K. and Yamamoto Y. (1999). Habitat selection of ducks wintering in agricultural landscapes: a preliminary study for establishing a stable wintering duck population at Katano-kamoike, STRIX 17: 127-132 (in Japanese). Yamamuro M., Oka N. and Hiratsuka J. (1998). Predation by diving dacks on the biofouling mussel Musculista senhousia in a eutrophic estuarine lagoon, Marine Ecology Progress Series, 174, 101-106. . Wildlife Refuge, New Mexico, Limnology and Oceanography, 44(3), 82 8 -83 6. Kurechi M. and Otsu M. (1 983 ). Estimate of the carrying capacity of the wintering geese. freshwater reservoir, Freshwater Biology, 50, 88 2 -89 0. Pettigrew T. C., Hann J. B. and Goldsborough G. L. (19 98) . Waterfowl feces as a source of nutrients