Macroinvertebrates of Eichhornia crassipes roots in the alluvial floodplain of great rivers, Argentina

POI DE NEIFF, A. S.G.; GALLARDO, L. I.; CASCO, S. L.

Congreso; Congreso Aquatrop; 2018

Universidad San Francisco (Quito)

Eichhornia crassipes is a dominant aquatic plant of neotropical-river floodplains and is invasive in warm waters of different continents. Plants provide food and habitat for fish, especially for Gymnotus carapo, which is relevant to subsistence fishing of local indigenous communities. We analyzed abundance and richness of invertebrate assemblages associated with Eichhornia crassipes roots in floodplain wetlands of the Paraná River (within the Ramsar site Wetlands Chaco) and of the Río Pilcomayo National Park. During spring and summer, 40 samples were collected in the floating meadows with a net of 500µ mesh size. The water quality and five plant morphological traits was measured. Temperature and nutrient content were higher in the Pilcomayo than in the Paraná floodplain. Although leaf density did not differ significantly between both floodplains, the relation petiole length / root length was lower in the Paraná than in the Pilcomayo floodplain. The number of invertebrates per g. root dry weight was significantly different between both floodplains, but the number per m2 and the taxon richness did not differ. Different species dominated in each floodplain: prawns (Macrobrachium jelskii and M. amazonicum), snails (Littorinina guaranitica), amphipods (Hyalella curvispina) and cladocerans (Simocephalus vetulus) were frequent and abundant in the Pilcomayo floodplain, whereas Oligochaeta (Naididae), Chironomidae larvae and cladocerans (Grimaldina brazzai) were dominant in the Paraná floodplain. In this floodplain, amphipods and prawns were often rare or absent in relation to dense cover of E. crassipes and oxygen depletion in summer. Our data suggest that the river water quality is determinant of the growth forms of water hyacinth, and, both affect the abundance and composition of macroinvertebrates. E. crassipes provide unique habitat that contributes to overall biotic diversity, which should be considered in the management strategies.