Macroinvertebrates of Eichhornia crassipes (Pontederiaceae) roots in the alluvial floodplain of large tropical rivers (Argentina)

Abstract

Introduction: 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 Prochilodus lineatus and Gymnotus omarorum, which are relevant to subsistence fishing by local indigenous communities. Objective: In this study we describe the main traits of E. crassipes floating meadows, and analyze the abundance and composition of macroinvertebrate assemblages associated with their roots in two floodplain wetlands of the Paraná River (within the Ramsar site Wetlands Chaco) and of the Pilcomayo River (within the Pilcomayo River National Park). Methods: During spring and summer, the macroinvertebrates were collected in monospecific stands of E. crassipes with a net of 962 cm2 area and 500 µm mesh size. Leaf density, the biomass of leaves and roots, the length of leaves and roots, and the water quality were measured simultaneously. Results: Temperature, oxygen concentration, and nutrient content were significantly higher and electrical conductivity was lower in the Pilcomayo than in the Paraná floodplain. E. crassipes growing in the Pilcomayo floodplain had longer leaves and less root biomass than those found in the Paraná floodplain. The number of macroinvertebrates per 1 000 g root dry weight and per m2 was significantly different between both floodplains, but the taxon richness was similar. Non Metric Multidimensional Scaling analysis differentiated the abundance of 14 selected taxa between both floodplains, and showed a high correlation between the environmental variables and macroinvertebrate abundance. The most abundant taxonomic groups in the Paraná River floodplain were oligochaetes (Naididae), ostracods mainly Cytheridella ilosvayi and larvae of non-biting midges (Chironomidae). Two families, Hydrobiidae (Heleobia parchappii) and Chironomidae accounted for 49.3 % of the total abundance in the Pilcomayo floodplain. The prawns Macrobrachium jelskii and M. amazonicum, frequent in the Pilcomayo floodplain, were not found in the Paraná floodplain. Conclusions: The different environmental conditions in both floodplains affect the abundance, composition, and the dominance of macroinvertebrate assemblages; however, the total taxa richness was similar. The area occupied by E. crassipes in the floodplains of these rivers provides the habitat that contributes most to overall biotic diversity, which must be considered in management strategies.

Water Quality Analysis in a Subtropical River with an Adapted Biomonitoring Working Party (BMWP) Index

“…This area of the river has been modified to be a small reservoir and the flow is controlled by a gate adjacent to the union with the Lerma River. The higher BMWP value at this site, in contrast to the other indices, could be related to continuous flow (the gates were open in all seasons) and the presence of water hyacinths that contribute to overall biotic diversity because they offer different habitats for macroinvertebrates [60].…”

Linking hydrological connectivity with the richness and composition of aquatic invertebrates across the Paraná River floodplain, Argentina

“…During rising water, floating macrophytes are retained in the oxbow lakes by the riparian forest located in the sand bars and the roots act as filters for inorganic sediments supplied by the river (Poi de Neiff et al, 1994). In this section of the Paraná floodplain, the resetting processes mentioned for other rivers (Junk et al, 1989) where floating aquatic and semi-aquatic macrophytes are exported and provide organic matter and nutrients to the main channel communities, do not occur.…”

Lepidópteros acuáticos y semiacuáticos en Argentina: lista actualizada, distribución y hábitos de vida

“…Por ejemplo, la diversidad de algunas familias de lepidópteros relacionados a macrófitas acuáticas es pobre, ya que muchos taxones no están determinados a nivel genérico (Poi de Neiff, 2003;Poi de Neiff y Neiff, 2006;Poi et al, 2020). La mayoría de los estudios sobre taxonomía, biología básica y la historia de vida se llevan a cabo principalmente con especies de importancia agrícola, o para el control biológico de malas hierbas acuáticas (Center et al, 1999;Julien et al, 2001).…”

“…En general, el orden no es considerado como un componente de la comunidad acuática y ha sido constantemente excluido de los estudios sobre la ecología de los insectos relacionados con este ambiente, especialmente con las macrófitas a las cuales se relacionan la mayoría de las especies semiacuáticas (Lavery y Costa, 1972;Poi de Neiff, 2003;Poi de Neiff y Neiff, 2006;Graça y Solís, 2018;Poi, Neiff, Casco y Gallardo, 2020). Recientemente el interés por las especies semiacuáticas se ha incrementado, especialmente por la propuesta de usar algunos de sus miembros como agentes de control biológico de plantas acuáticas invasivas debido a los hábitos herbívoros de las larvas, las cuales pueden ser perforadoras, minadoras o defoliadoras…”