BIOMASS OF MACROPHYTE FUNCTIONAL GROUPS RESPOND DIFFERENTLY TO ABIOTIC AND MORPHOMETRIC FACTORS

SCHNEIDER, BERENICE; CUNHA, EDUARDO; MARCHESE, MERCEDES; THOMAZ, SIDINEI MAGELA

Maringá

Congreso; XV Congresso Brasileiro de Limnologia. Perspectivas evolutivas. (CBL 2015); 2015

Nucleo de Pesquisas em Limnologia e Aquicultura (NUPELIA)- Universidade Estadual de Maringá (UEM)

Macrophytes are important components of large river floodplains, affecting the structure and functioning of shallow freshwater ecosystems. Different macrophyte life forms use resources in a specific way, play different ecological roles and therefore, the factors that affect them also vary. The aim of this study was to assess the importance of abiotic factors and morphometric characteristics on the biomass of macrophyte functional groups in 23 waterbodies of the Middle Parana River floodplain. Surveys were conducted during low and high water levels. Macrophyte biomass contained within a 0.25 m² quadrat was collected, classified in life forms (emergent (E), epiphytic (Ep), free floating (FF), free submerged (FS), rooted submerged (RS), rooted floating leaves (RFL) and rooted floating stems (RFS)) and dried to constant weight. The biomass composition of functional groups differed between hydrologic periods and the degree of connectivity of the environments, while the biomass of the singular functional groups was related to connectivity (PERMANOVA). The strength of association between macrophyte biomass with other morphometric characteristics and abiotic factors varied from moderate to low depending of the functional group. Connectivity was negatively related with the biomass of E, FS and RS plants and positively with FF and RFS, indicating that this variable may suppress some life forms while favoring others. Depth was positively related with RFL and RFS and slope was with RFS indicating habitat availability. Among nutrients, negative associations were found for nitrate, phosphorus and organic matter with FF, RFS, RS and pooled biomass of all functional groups, which indicates remarkable nutrient uptake by macrophytes. Accordingly, BIOENV evidenced that among the environmental variables explaining the biomass composition, the subset including degree of connectivity, fetch, nitrate, ammonium and phosphorus presented the strongest correlation. In conclusion, the general results indicate that the biomass of macrophytes functional groups respond differently to the abiotic and morphometric factors, confirming our prediction of particular responses of life forms to environmental changes. In addition, despite no one can be singled out as the primer controller, we conclude that in the Middle Paraná River floodplain the hydrological period, connectivity and nutrients are the most important determinants of the biomass of macrophyte functional groups.