Nutrient Stock in the Aquatic Macrophytes Eichhornia crassipes and Pistia stratiotes in the Pantanal Brazil Abdo, M.S.A and Da Silva, C.J.

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1 Nutrient Stock in the Aquatic Macrophytes Eichhornia crassipes and Pistia stratiotes in the Pantanal Brazil Abdo, M.S.A and Da Silva, C.J. Universidade Federal de Mato Grosso, Instituto de Biociências, Brazil 1 Introduction The Pantanal wetlands, located in the floodplain of the Upper Paraguay River Basin (Brazil) are characterized by alternating rainy and dry seasons. The heavy rains increase the water level in the rivers and lakes, creating a fluctuation in their floodplains from the dry phase to aquatic phase. During the dry seasons, the water level decreases and the floodplains return to their dry state again. The annual flood pulse determines the ecological processes in these ecosystems, mainly in relation to the nutrient cycles. In these ecosystems, the aquatic macrophytes play an important role in the nutrient cycle, due to the large quantity of biomass they produce and their capacity to accumulate large concentrations of nutrients. The objective of this research is to evaluate the effect of the flood pulse in relation to the concentration of nitrogen and phosphorus in the water, the sediment and the aquatic macrophytes in one lake. Moreover, it also takes into account the influence of the breeding colonies which circle around the lake, in terms of the extra nutrient input. 2 Study Area The Ninhal Corutuba lake is located at left side of Cuiabá River. between coordinates S and W, Municipality of Barão de Melgaço, Mato Grosso State, Wetlands Pantanal, Brazil (Fig.1). 3 Methodology Data were collected from October 1995 to September Nitrogen and phosphorus concentrations in water, sediments and aquatic macrophytes were analysed according to GOLTERMAN et al. (1978), MACKERETH et al. (1978), ALLEN (1989) and ANDERSON & INGRAM (1996). Estimates of concentrations were based NOGUEIRA (1989), DA SILVA (1990) and ESTEVES (1998). 4 Results and discussions The highest level water (4.00 m) was registered in March, during the rainy season and the lowest (1.05 m) in September, in the dry season. In the rainy season, October to April, the volume of water accumulated by precipitation was 1.698,5 mm. By other side, the total volume of water lost due evaporation, in the dry season (May to September) was 1.109,3 mm (Fig. 2). The highest concentration of total nitrogen and phosphorus in the water (46.95 mgl -1 -N and 4.80 mgl -1 -P, respectively) and sediment (14.01 mgg -1 -N and mgg -1 -P) was get during dry season/low water period. In the rainy season/high water period, the concentration of nitrogen and phosphorus in water decreased to 3.18 mgl -1 -N and 3.68 mgl -1 -P, while in the sediment to 8.96 mgg -1 -N and 2.37 mgg -1 -P (Fig. 4). This condition is a result of diminished of water volume and water temperature, which also cause the decomposition of aquatic macrophytes and phytoplanctonic communities. Eichhornia crassipes accumulated a biomass medium of the 1, gm -2 DW in the rainy season high water period and gm -2 DW during the dry season period. The highest concentrations of organic nitrogen and phosphorus were found in rhizomes during the dry season, mgg -1 DW-N and 5.58 mgg -1 DW-P, respectively (Fig. 5). Pistia stratiotes also obtained a higher value of biomass in rainy season/high water period (1, gm -2 DW) then in the dry season/low water period ( gm -2 DW). Values of nitrogen and phosphorus organic were highest in the dry season, too. Rhizome accumulated the largest amount of organic nitrogen (29.33 mgg -1 DW-N) and leaves of organic phosphorus (4.88 mgg -1 DW-P) (Fig. 6). The stock of nitrogen and phosphorus in water and sediment were higher during the dry season (Tab. 1). Among the aquatic macrophytes, Eichhornia crassipes showed higher values of these nutrients, as it accumulated more biomass than P. stratiotes. The nitrogen stock in E. crassipes was much higher in low water period while the stock of phosphorus increased in high water period. The stock of nitrogen and phosphorus in Pistia stratiotes presented an increase during the high water period, due increase of biomass, necromass and flowers production (Tab. 2). P. stratiotes showed higher values of the total stock of nitrogen and phosphorus in all area covered by E. crassipes ( m 2 ) and P. stratiotes (3, m 2 ), during low water period. Leaves from this species accumulate a stock of 5.97 kg of nitrogen and 0.98 kg of phosphorus. The comparison of the nitrogen and phosphorus stocks 875

2 (Fig. 7) during low water period, between water (2, m 2 ), sediment ( m 2 ), E. crassipes ( m 2 ) and P. stratiotes ( m 2 ), showed that the water column accumulated the higher quantity of nitrogen (16.91 kg = 44.54%) and phosphorus (2.32 kg =35.53%), followed by aquatic macrophytes. Studies made by DA SILVA (1990), in Pantanal wetlands by NOGUEIRA (1989), in oxbow lakes, revealed that the sediment was the main compartment for nitrogen and phosphorus storage. 5 Conclusion The evaluation of nitrogen and phosphorus stored in water column, sediment and aquatic macrophytes indicates that the nutrients cycles (nitrogen and phosphorus) are controlled mainly by food pulse (i.e., by water renovation), followed by biologic components, aquatic macrophytes and aquatic bird breeding colonies which function as a important source of these nutrients in Corutuba lake. 6 Bibliography ALLEN, S.E Chemical Analysis of Ecological Materials. Second Edition. Blackwell Scientific Publications, London, p. ANDERSON, J.M., INGRAM, J.S.I Tropical Soil Biology and Fertility - A Handbook of methods. Second Edition., Information Press, Eynsham-UK- Cab International. 221 p. CARMOUZE, J.P O metabolismo dos Ecossistemas Aquáticos: Fundamentos teóricos, métodos de estudos e análises químicas. São Paulo. Ed. Edgard Blücher. FAPESP. 253p. DA SILVA, C.J A influência da variação do nível da água sobre a estrutura e funcionamento de uma área alagável do Pantanal Matogrossense (Pantanal de Barão de Melgaço, Município de Santo Antonio do Leverger e Barão de Melgaço-MT). São Carlos, UFSCar. 251 p. (Tese de Dourado). ESTEVES,F.A Fundamentos de Limnologia. Rio de Janeiro, 2º Edição - Rio de Janeiro. Interciências. 602 p. Golterman. H.L., Clymo, R. S., OHNSTAD, M. A. M Methods for Physical and Chemical Analysis of Fresh Waters. 2 ed. Oxford, Blackwell, 215p. (IBP Handbook 8) MACKERETH, F.J.H.; HERON, J., TALLING, J.F Water Analysis: Some revised methods for limnologists. Cumbria, Freshwater Biological Association. 120p. (Scientific Publication nº 36). NOGUEIRA, F. M. B Importância das macrófitas aquáticas Eichhornia azurea Kunt e Scirpus cubensis na ciclagem de nutrientes e nas principais caracteristicas limnológicas da Lagoa do Infernão (SP). São Carlos, S.P. 147 p. (Dissertação) 876

3 Fig. 1: Localization of study area in the Pantanal and South American region. 877

4 Fig. 2: Water level in the Ninhal Corutuba lake, precipitation and evaporation value from Agrometeorological Station in Sto. Antonio de Leverger. October 1995 to September Fig. 3: Monthly medium in the total nitrogen and phosphorus in water surface of Ninhal Corotuba lake, Barão de Melgaço, MT. From October 1995 to September Fig. 4: Total nitrogen and phosphorus in sediment in the Ninhal Corotuba lake, Barão de Melgaço, MT. Rainy month (April) and dry month (September) in

5 Fig. 5: Nitrogen and phosphorus organic in sheaths, blade, stem, roots, rhizome and necromass of the Eichhornia crassipes in the Ninhal Corotuba lake, Barão de Melgaço, MT. Rainy month (March and April) and dry month (August and September) in Fig. 6: Nitrogen and phosphorus organic in leaves, roots, rhizome, flowers and necromass of the Pistia stratiotes in the Ninhal Corotuba lake, Barão de Melgaço, MT. Rainy month (March and April) and dry month (August and September) in Fig. 7: Total store of nitrogen and phosphorus in water, sediment and aquatic macrophytes, Eichhornia crassipes and Pistia stratiotes in the Ninhal Corotuba lake, Barão de Melgaço, MT. Dry season in

6 Tab. 1: Nitrogen and phosphorus stock in water and sediment of the breeding colonies Corotuba lake, during rainy and dry season of Tab. 2: Stock of nitrogen and phosphorus organic in structures of Eichhornia crassipes and Pistia stratiotes in breeding colonies Corotuba lake, in low and high water period of

7 Editors Reinhard Lieberei 1, Helmut K. Bianchi 2, Vera Boehm 1, Christoph Reisdorff 1 1 Universität Hamburg, Institut für Angewandte Botanik, Ohnhorststr. 18, Hamburg, Germany 2 GKSS-Forschungszentrum Geesthacht GmbH, Max-Planck-Straße 1, Geesthacht Germany Layout Printing Helmut K. Bianchi, GKSS, Karsten Bittner, Documedia, Geesthacht, Germany GKSS-Forschungszentrum Geesthacht GmbH, Geesthacht, Germany ISBN X Lieberei, R., Bianchi, H-K., Boehm, V., Reisdorff, C., (eds.) 2002: Neotropical Ecosystems, Proceedings of the German-Brazilian Workshop, Hamburg GKSS-Geesthacht. The publishers give permission to copy single contributions from the Proceedings for personal use exclusively. Copies may be passed on only with the correct specification of the source. The research cooperation has been carried out under the auspices of the German - Brazilian Govemmental Agreement on the Cooperation in Scientific Research and Technological Development. The issuance of the Proceedings and the production of the CD-ROM was sponsored (Code ) by the Federal Ministry of Education and Research The responsibility for the contents of the contributions is solely the authors'.