Int. J. of Aquat. Biol. (2015) 3(4): 208-217 ISSN: 2322-5270; P-ISSN: 2383-0956 Journal homepage: www.ij-aquaticbiology.com © 2015 Iranian Society of Ichthyology Original Article Development and application of wetland zooplankton index to assess the degree of eutrophication in Sri Lankan reservoirs Mudiyanselage Jayantha Sisirakumara Wijeyaratne*,1Sangakkara Mudiyanselage Ayanthi Indrachapa Sangakkara Department of Zoology and Environmental Management, University of Kelaniya, Kelaniya, Sri Lanka. Article history: Received 8 February 2015 Accepted 4 June 2015 Available online 2 5 August 2015 Keywords: Wetland zooplankton index Eutrophication Nitrate Phosphorus Abstract: Wetland Zooplankton Index (WZI) was developed for the low country intermediate zone of Sri Lanka using 20 reservoirs located between latitudes 7°20'22.081"N - 7°48'33.558"N and longitudes 80°1'44.55"E - 80°9'51.509"E. WZI ranged from 1.56 in Anukkane reservoir which is located in a low flat terrain in the midst of agricultural lands to 3.69 in Tampana reservoir which is located in a hilly area with a watershed mainly covered with forests. WZI showed a significant negative correlation with the Nitrate-N content (r = -0.797) and cumulative content of Nitrate-N and total phosphorus (r = -0.795) indicating that it can be used as an indicator of the degree of eutrophication of inland reservoirs in the low country intermediate zone of Sri Lanka. Introduction Sri Lanka is a country that has a culture entangled with ancient irrigation systems with many cascading reservoirs and canals. Due to these man-made reservoirs, Sri Lanka has a very high density of inland wetlands, which is about 4 ha for every km2 of land. About 12000 of these man-made wetlands are located in the dry zone and the intermediate zone of Sri Lanka (Jayasena et al., 2011). These play a significant role in economy by providing water for irrigation, livestock, fisheries, aquaculture and generation of hydropower. In addition, these water bodies supply drinking water as well as for domestic purposes (Imbulana et al., 2006). Eutrophic conditions have been reported in many reservoirs in Sri Lanka mainly due to uncontrolled and excessive use of agrochemicals (Imbulana et al., 2006). Major types of fertilizer used for agricultural activities in Sri Lanka are sulphate of ammonia, urea, rock phosphate, Muriate of potash, triple super phosphate and mixed fertilizers (Mubarak, 2000). Due to high costs of the chemical tests and the * Corresponding author: M.J.S. Wijeyaratne E-mail address: zoomjs@kln.ac.lk chemical waste generated by these methods, several alternatives are being used today to assess the water quality (Barra et al., 2012). These include the use of indicator organisms (Gannon and Stemberger, 1978; El-Shabrawy and Khalifa, 2002; Füreder and Reynold, 2004; Yantsis, 2009) and water quality indices (Chow-Fraser, 2006; Seilheimer et al., 2009). Wetland Zooplankton Index (WZI) is one of such indices (Lougheed and Chow-Fraser, 2002). Although some studies on the relationship between the abundance of some zooplankton species and water quality have been carried out (Kamaladasa and Jayatunga, 2007; Gammanpila, 2010), development and use of a WZI to indicate water quality of inland water bodies is a novel approach in Sri Lanka. Developing a WZI to find out whether it can be used to assess the eutrophic conditions of the reservoirs is highly appropriate in the present-day context as Sri Lanka is reported to have a high fertilizer consumption of 101.5 kg ha-1 (Mubarak, 2000). Therefore, the objective of the present study was to develop a WZI and to find out whether it can be used 209 Wijeyaratne and Sangakkara/ Wetland zooplankton index for Sri Lankan reservoirs to assess the degree of eutrophication in the reservoirs in the low country (Elevation: <300 m msl) intermediate zone (Annual rainfall: 1,750-2,500 mm) of Sri Lanka. Materials and Methods This study was carried out in 20 reservoirs located in the low country intermediate zone of Sri Lanka between latitudes 7°20'22.081"N-7°48'33.558"N and longitudes 80°1'44.55"E-80°9'51.509"E (Table 1). The surface area of the reservoirs varied from 1 ha to 756.3 ha (Table 1). The low country intermediate zone was selected for this study as this area is a heavy agricultural area with paddy fields and coconut plantations. In addition, this area has a very high density of inland reservoirs. The reservoirs used in the present study except for two, namely Tampana and Kurunegala reservoirs provide water for irrigation purposes. Tampana and Kurunegala reservoirs are used to provide water for the households in the urban and suburban areas of Kurunegala town. Zooplankton of these reservoirs were sampled from June to October 2013 using "Patalas-Schindler" Plankton sampler of 10-L capacity. Sampling was carried out at least 5 m away from the aquatic vegetation and at least 3 m away from the shore as recommended by Lougheed and Chow-Fraser (2002). Samples were immediately preserved using 5% formalin based on Dhargalkar and Verlecar (2004). Zooplankton were identified under the optical microscope using the taxonomic keys provided by Fernando (1990). The abundance of each species was determined by sub-sampling using a Sedgewick rafter. At the time of sampling, water samples were also collected in dark plastic-bottles for the determination of nitrate-N and total phosphorus levels. The water samples were immediately preserved at the site by adding 0.5 ml of concentrated sulphuric acid and the nitrate and total phosphorus contents were determined using APHA (1998). On each sampling occasion, three samples were taken from each site. When the reservoirs were <20 ha in surface area, samples were taken from three sites, and when the reservoirs were 20-50 ha in surface area, samples were taken from five sites. The number of sample sites in each of the Kimbulwana (278 ha) and Bathalagoda (255 ha) reservoirs were eight. From Wendaru (92 ha) and Dewahuwa 756 ha) Reservoir number Name of the Reservoir Location Surface Area (ha) 1 Adukkane 80°08'14.233"E 7°31'28.100"N 2.9 2 Anukkane 80°07'14.380"E 7°30'43.170"N 9.1 3 Bathalagoda 80°26'50.246"E 7°31'59.222"N 255.2 4 Bodhimulla 80°05'51.912"E 7°31'35.360"N 3.9 5 Dewahuwa 80°32'26.782"E 7°48'33.558"N 756.3 6 Galewela 80°34'34.283"E 7°45'41.707"N 5.9 7 Galpihilla 80°09'30.015"E 7°20'52.894"N 1.0 8 Gaiyawa 80° 01'44.55"E 7°28'46.210"N 16.2 9 Kanogama 80°09'51.509"E 7°32'35.510"N 22.4 10 Karangamuwa 80°10'21.512"E 7°32'50.654"N 8.9 11 Kimbulwana 80°28'19.837"E 7°39'50.338"N 237.9 12 Kurunegala 80°21'43.271"E 7°29'36.949"N 48.0 13 Makandura 79°59'38.603"E 7°20'22.081"N 36.0 14 Metiyagane 80°10'59.642"E 7°23'37.450"N 5.2 15 Munamaldeniya 80°03'51.940"E 7°32'57.392"N 17.4 16 Polpitiya 80°11'90.675"E 7°31'40.407"N 11.2 17 Saragama 80°20'10.126"E 7°30'37.575"N 20.1 18 Tampana 80°24'25.140"E 7°26'55.036"N 1.5 19 Umangawa 80°10'50.130"E 7°32'01.440"N 3.0 20 Wendaru 80°22'30.099"E 7°27'55.695"N 92.0 Table 1. Location and the surface area of the reservoirs studied. 210 Int. J. Aquat. Biol. (2015) 3(4): 208-217 reservoirs, samples were taken from six and ten sites, respectively. Sampling sites were selected to cover the entire water body. WZI for each reservoir was calculated using the following equation of Lougheed and Chow-Fraser (2002). Where, Yi =Abundance of species i, Ti = Tolerance value (1-3) of species i, Ui = Optimum value (1-5) of species i and n = number of zooplankton species in the reservoir. The values for WZI ranged from 1.0, indicative of low water quality (high eutrophication) to 5.0, indicative of high quality (low eutrophication) (Lougheed and Chow-Fraser, 2002). Tolerance values (T) indicate tolerance or the niche breadth of a species. Species that have a narrow range of distribution were given a low tolerance score as recommended by Lougheed and Chow-Fraser (2002). In the present study, if a species was present in less than 33% of the studied reservoirs, i.e., ≤ 7 reservoirs, a T value of 1 was assigned. For the species that were found in 8-13 reservoirs, i.e., 33- 67% of the studied reservoirs, T value of 2 was assigned and for the species that were found in more than 13 reservoirs, i.e., in more than 67% of the studied reservoirs, the assigned T value was 3. To assign U values, three clusters of reservoirs were identified based on nitrate-N and total phosphorus contents. Clustering was done based on Bray Curtis similarity using Primer 5.0 software package. Reservoirs with comparatively low nitrate-N and total phosphorus contents were grouped in cluster 1 and reservoirs with comparatively high nitrate-N and total phosphorus contents were grouped in cluster 3. The reservoirs with comparatively intermediate nitrate-N and total phosphorus levels were grouped in cluster 2. The assigning of U values for different zooplankton species is summarized in Table 2. The product-moment correlation coefficients of WZI with the nitrate-N level, total phosphorus level and cumulative values of nitrate-N and total phosphorus were calculated. When the correlation coefficients were significantly different from zero, linear regression algorithms were developed taking WZI as the independent variable. Results Table 3 gives the mean ± standard error of the mean (SEM) and the range of the nitrate-N and total phosphorus values of the reservoirs studied. The highest nitrate-N content was recorded at Anukkane Reservoir (5.624 ± 0.072 mg L-1) while the lowest nitrate-N content was recorded at Adukkane Reservoir (1.186 ± 0.013 mg L-1). Total phosphorous levels varied from 0.003 ± 0.002 mg L-1 recorded in Bodhimulla Reservoir to 0.529 ± 0.036 mg L-1 recorded in Karangamuwa Reservoir The separation of reservoirs into clusters based on Cluster/clusters of reservoirs where a particular zooplankton species is present U value assigned 1 5 1 and 2 4 1 and 3 3 2 3 1, 2 and 3 3 2 and 3 2 3 1 (Cluster 1- Comparatively low nitrate-N and total pPhosphorus level; Cluster 2 - Intermidiate nitrate-N and total phosphorus level; Cluster 3 – Comparatively high nitrate-N and total phosphorus level). Table 2. Summary of the allocation of U values for different zooplankton species. 211 Wijeyaratne and Sangakkara/ Wetland zooplankton index for Sri Lankan reservoirs the nitrate-N and total phosphorus contents is shown in Figure 1. Three clusters of reservoirs were identified at 61% similarity level. The reservoirs with relatively low nitrate-N and total phosphorus levels positioned in cluster 1. Only three reservoirs were grouped in this cluster. Reservoirs with relatively moderate levels of nitrate-N and total phosphorus were grouped in cluster 2. There were 7 reservoirs in this cluster. In cluster 3, reservoirs with relatively high levels of nitrate and total phosphorus were included. There were 10 reservoirs in this cluster (Fig. 1). A total of 31 species of rotifers, 3 species of copepods and 9 species of cladocerans were identified in the samples (Table 4). The optimum values (U) assigned to different zooplankton species are also given in Table 4. Two species of rotifers namely Brachionus donneri and Testudinella elliptica were found only in the reservoirs of cluster 1. Therefore, a U value of 5 was assigned to them. One species of copepods, 3 species of cladocerans and 7 species of rotifers were found only in the reservoirs of cluster 3 and a U value of 1 was assigned to them. Two species of cladocerans and 12 species of rotifers were found only in the reservoirs of cluster 2 and 3 and were assigned a U value of 2. No zooplankton species was found in the reservoirs of both clusters of 1 and 2. Hence, a U value of 4 was not assigned to any species. Balance 16 species were in the reservoirs categorized either under cluster 2 or both in cluster 1 and 3 or in all three clusters and therefore, they were assigned a U value of 3 (Table 4). The Tolerance value (T) assigned to each zooplankton species are also given in Table 4. Only 1 species namely Diacyclops nanus was present in more than 66.6% of the reservoirs studied. Therefore, a T value of 3 was assigned to this species. T value of 2 was assigned only to 4 species namely Diaptomus nadus, Filinia terminalis, Hexarthra mira and Trichocerca cylindrica. All other species were found in less than 33.33% of reservoirs studied and therefore those species were assigned a T value of 1. Reservoir Nitrate - N (mg L-1) Total Phosphorus (mg L-1) 1 Adukkane 1.186 ± 0.013 (1.199-1.173) 0.046 ± 0.004 (0.05-0.042) 2 Anukkane 5.624 ± 0.072 (5.696-5.552) 0.086 ± 0.008 (0.094-0.078) 3 Bathalagoda 2.403 ± 0.370 (2.773-2.033) 0.075 ± 0.007 (0.082-0.068) 4 Bodhimulla 3.886 ± 0.215 (4.101-3.671) 0.003 ± 0.002 (0.005-0.001) 5 Dewahuwa 3.416 ±0.227 (3.643-3.189) 0.060 ± 0.012 (0.072-0.048) 6 Galewela 4.936 ± 0.038 (4.974-4.898) 0.190 ± 0.022 (0.212-0.168) 7 Galpihilla 2.548 ± 0.076 (2.472-2.624) 0.042 ± 0.008 (0.05-0.034) 8 Gaiyawa 3.923 ± 0.133 (4.056-3.79) 0.104 ± 0.01 (0.114-0.094) 9 Kanogama 2.626 ± 0.100 (2.726-2.526) 0.071 ± 0.009 (0.080-0.062) 10 Karangamuwa 3.452 ± 0.442 (3.894-3.01) 0.529 ± 0.036 (0.565-0.493) 11 Kimbulwana 4.213 ± 0.256 (4.469-3.957) 0.147 ± 0.006 (0.153-0.141) 12 Kurunegala 2.620 ± 0.344 (2.964-2.276) 0.164 ± 0.018 (0.182-0.146) 13 Makandura 1.570 ± 0.390 (1.96-1.180) 0.065 ± 0.011 (0.076-0.054) 14 Metiyagane 4.574 ± 0.345 (4.919-4.229) 0.065 ± 0.009 (0.056-0.074) 15 Munamaldeniya 4.213 ± 0.094 (4.307-4.119) 0.068 ± 0.007 (0.075-0.061) 16 Polpitiya 2.294 ± 0.687 (2.981-1.607) 0.309 ± 0.019 (0.328-0.290) 17 Saragama 3.344 ± 0.108 (3.452-3.236) 0.038 ± 0.008 (0.046-0.030 18 Tampana 1.932 ± 0.074 (2.006-1.858) 0.046 ± 0.006 (0.052-0.040) 19 Umangawa 2.765 ± 0.193 (2.958-2.572) 0.057 ± 0.004 (0.061-0.053) 20 Wendaru 2.294 ± 0.241(2.535-2.053) 0.030 ± 0.005 (0.035-0.025) Table 3. Mean ± SEM values of nitrate-N levels and total phosphorus levels of the reservoirs studied. Ranges are given within brackets. 212 Int. J. Aquat. Biol. (2015) 3(4): 208-217 The values for WZI calculated for the 20 study sites are given in Table 5. The highest WZI was obtained for Tampana (3.69) while the lowest WZI was obtained for Anukkane (1.56). WZI showed a significant negative correlation with nitrate-N content (r = -0.797; P = 0.00) while they were not significantly correlated with the total phosphorus content (r = 0.11; P = 0.64). Nevertheless, WZI Species Cluster present U value No. of reservoirs present T value Copepoda Acanthocyclops vernalis 3 1 2 1 Diacyclops nanus 1, 2 and 3 3 15 3 Diaptomus nadus 1, 2 and 3 3 10 2 Cladocera Alona monocantha 3 1 1 1 Chrydorus eurynotus 2 and 3 2 2 1 Chydorus parvus 1, 2 and 3 3 4 1 Diaphanosoma brachyurum 2, 3 2 3 1 Diaphanosoma singhalense 2 3 1 1 Karualona karua 3 1 1 1 Leptodora kindti 2 3 1 1 Moinodaphnia macleayi 3 1 1 1 Pseudosida szalayi 2 3 1 1 Rotifera Asplanchna priodonta 3 1 1 1 Brachionus angularis 2 3 1 1 Brachionus budapestinensis 2 and 3 2 2 1 Brachionus caudatus 1, 2 and 3 3 6 1 Brachionus donneri 1 5 1 1 Brachionus falcatus 2 and 3 2 3 1 Brachionus forficula 2 and 3 2 5 1 Brachionus patulus 2 and 3 2 3 1 Brachionus rubens 2 and 3 2 2 1 Brachionus urceus 3 1 2 1 Coelopus tenuior 1 and 3 3 2 1 Eothinia elongata 2 and 3 2 3 1 Euchlanis dilatata 2 and 3 2 5 1 Filinia terminalis 2 and 3 2 8 2 Hexarthra mira 2 and 3 2 8 2 Kellicottia longispina 3 1 1 1 Keratella earlinae 1 and 3 3 2 1 Keratella lenzi 2 3 1 1 Keratella quadrata 3 1 1 1 Lecane curvicornis 2 and 3 2 4 1 Monostyla bulla 1, 2 and 3 3 6 1 Polyarthra dolichoptera 3 1 1 1 Polyarthra vulgaris 2 and 3 2 6 1 Rattulus tigris 3 1 1 1 Rotaria citrine 2 3 1 1 Testudinella elliptica 1 5 1 1 Testudinella patina 1 and 3 3 2 1 Trichocerca cylindrica 1, 2 and 3 3 10 2 Trichocerca dixon-nuttalli 2 3 1 1 Trichocerca similis 3 1 1 1 Trichotria pocillum 2 and 3 2 2 1 Table 4. Optimum values (U) and tolerance values (T) assigned for the zooplankton species recorded in the present study. 213 Wijeyaratne and Sangakkara/ Wetland zooplankton index for Sri Lankan reservoirs showed a significant negative correlation with the cumulative content of nitrate-N and total phosphorus Figure 1. Clusters of reservoirs based on nitrate-N and total phosphorus levels [Cluster1- Comparatively low nitrate-N and Total phosphorus levels; Cluster 2- moderate nitrate-N and total phosphorus levels; Cluster 3- Comparatively high nitrate-N and total phosphorus levels]. Figure 2. Simple linear regression algorithm between WZI and nitrate-N levels of the reservoirs studied with 95% confidence band. Figure 3. Simple linear regression algorithm between WZI and cumulative levels of nitrate-N and total phosphorus of the reservoirs studied with 95% confidence band. 214 Int. J. Aquat. Biol. (2015) 3(4): 208-217 contents (r = -0.795; P = 0.00). Because of the significant correlation of WZI with nitrate-N and cumulative value of nitrate-N and total phosphorus, the linear regression algorithms were developed using WZI as the independent variable and these are as follows (P = 0.00). Nitrate-N (in mg L-1) = 9.35 – 2.31 WZI (R2 = 66.4) Nitrate-N + Total Phosphorus (in mg L-1) = 9.55 – 2.34 WZI (R2 = 66.1) The 95% confidence band for these two algorithms are given in Figures 2 and 3, respectively. Discussion Zooplankton respond rapidly to the changes in environmental conditions (Schindler, 1987). However, they have been hardly used in Sri Lanka to study the environmental conditions of aquatic habitats (Kamaladasa and Jayatunge, 2007; Gammanpila, 2010). Although some individual species of zooplankton are used as indicator organisms of water quality (Slȧdeĉek, 1983; Perbiche-Neves et al., 2013), studies on the use of zooplankton communities as a whole to indicate water quality are sparse (Lougheed and Chow-Fraser 2002, Yantsis 2009). All the reservoirs used in this study are located in a cascading system (Jayasena et al., 2011) and except for Tampana and Kurunegala reservoirs, the land-use in their watersheds contain many paddy field and coconut lands. Hence, storm water from these agricultural fields and excess water for wet paddy cultivation lands ultimately flow into these reservoirs. The watershed of Tampana and Kurunegala reservoirs are mostly covered with forests and urban residential areas, respectively. Sri Lanka is among the highest fertilizer users in South Asian region (Mubarak, 2000). In addition, the Kurunegala District where most of these reservoirs are located is accounting for the highest extent of agricultural production (DCS, 2013). According to World Bank statistics, fertilizer consumption in Sri Lanka was measured as 257.93 kg ha-1 of arable land in 2009. The most used fertilizers are nitrogenous, potash and phosphate fertilizers, including ground rock phosphate (Trading Economics, 2013). Farmers use fertilizer excessively in fields due to lack of knowledge. Large amounts of nutrients especially nitrate and phosphates are added to these inland water bodies due to agricultural runoff resulting in high nitrate-N and total phophorus levels. According to the nitrate-N and total phosphorous levels, all the reservoirs used in the present study are eutrophic (Nürnberg, 1996). Many negative environmental and social impacts have been reported in some Sri Lankan reservoirs due to eutrophication (Wijesundara et al., 2012; Ariyawansa et al., 2012; Azmy et al., 2012). Hence, it is important to assess the degree of eutrophication in inland fresh water bodies in order to take suitable mitigation measures to reduce further eutrophication and improve the water quality. The WZI recorded in the present study are within the range recorded by Lougheed and Chow-Freser (2002) for Laurentian Great Lakes basin although the water bodies are under contrasting ecological extremes. The U values for different zooplankton species were assigned in the present study using a simple method of clustering the reservoirs based on the nitrate-N and total phosphorus levels where as Name of the Reservoir WZI Adukkane Wewa 3.07 Anukkane Wewa 1.94 Bathalegoda Reservoir 3.30 Bodhimulla Wewa 3.13 Dewahuwa Reservoir 3.00 Galewela Wewa 2.99 Galphilla Wewa 3.11 Gaiyala Wewa 2.97 Kanogama Wewa 3.38 Karangamuwa Wewa 3.25 Kimbulwana Wewa 3.13 Kurunagala Wewa 3.77 Makandura Wewa 3.45 Metiyagane Wewa 3.39 Munamaldeniya Wewa 3.02 Polpitiya Wewa 3.00 Saragama Wewa 3.52 Thampana Reservoir 4.33 Umangawa Wewa 3.12 Wedaru Wewa 3.06 Table 5. The values for WZI of the reservoirs studied.zooplankton species. 215 Wijeyaratne and Sangakkara/ Wetland zooplankton index for Sri Lankan reservoirs Lougheed and Chow-Fraser (2002) used partial canonical correspondence analysis. WZI closer to 1 indicates high degree of eutrophication while the values closer to 5 indicate least degree of eutrophication. The highest WZI value was recorded for Tampana reservoir (3.69) which indicates least eutrophication. This reservoir has a comparatively low nitrate-N level of 1.932 mg L-1 and total phosphorus level of 0.046 mg L-1. The watershed of this water body, which is located in high elevation contains many forest areas and therefore does not receive agricultural runoff. The lowest WZI (1.56) was recorded for Anukkane which is located in a flat terrain surrounded by agricultural lands. The highest nitrate value was recorded in this reservoir. This low WZI indicates high degree of eutrophication probably due to addition of large amount of nutrients from the agricultural fields in the watershed. The algorithms developed in the present study may be used to estimate the nitrate-N level and cumulative level of nitrate-N and total phosphorus in the inland reservoirs in this region of the country using the WZI. 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(2015) 3(4): 208-217 ISSN: 2322-5270; P-ISSN: 2383-0956 Journal homepage: www.ij-aquaticbiology.com © 2015 Iranian Society of Ichthyology چکیده فارسی توسعه و کاربرد شاخص زئوپالنکتون تاالب برای ارزیابی درجه یوتریفیکاسیون در منابع آبی سریالنکا و س. م. آ. سانگاککارا *م. ج. س. ویجیارانته کالنیا، سریالنکا.، دانشگاه کالنیا، و مدیریت محیط زیست گروه جانورشناسی چکیده: منبع آبی که در 02میانی سریالنکا با استفاده از سرزمینی برای ناحیه( Wetland Zooplankton Index=WZIتاالب ) زئوپالنکتون شاخص ، توسعه داده ندواقع شده بود E - 80°9'51.509"E"44.55'1°80 جغرافیایی و عرض N - 7°48'33.558"N"22.081'20°7طول جغرافیایی واقع شده های کشاورزی که در یک منطقه کم ارتفاع در میانه زمین، Anukkane برای منبع آبی 65/1از WZI ، مقادیرشد. براساس نتایج یک WZI، متغیر بود. نتایج واقع شده استای با پوشش جنگلی ای با حوضهکه در ناحیه تپه Tampanaبرای منبع آبی 56/3تا است ( نشان داد که بیانگر این موضوع r= -766/2) کل ( و محتوای تجمعی نیترات و فسفرr= -767/2همبستگی منفی را با محتوای نیترات ) ورد ممیانی سریالنکا سرزمینی ناحیهمنابع آبهای داخلی در برای ارزیابی عنوان شاخص درجه یوتریفیکاسیون تواند بهمی WZIباشد که می استفاده قرار بگیرد. .فسفر، نیترات، یوتریفیکاسیون ، تاالب زئوپالنکتون شاخص :کلمات کلیدی