Aquatic Macroinvertebrates Diversity in the Grijalva and Usumacinta Rivers, Mexico
Synopsis
Aquatic macroinvertebrates are important and abundant components of the aquatic ecosystem, they transfer energy to higher trophic levels and can be used as bioindicator of aquatic ecosystem condition. The diversity of macroinvertebrates was determined through multihabitat diurnal sampling in three sections and five sites per section in the Grijalva and Usumacinta rivers, covering dry, rainy, and northern wind seasons. 75,482 individuals were recorded corresponding to 79 families, 128 genera, and 140 species, six species of mollusks, 11 of insects, and four of crustaceans for the Grijalva, and 17 of mollusks, 44 of insects, and 9 of crustaceans for Usumacinta were exclusive. The invasive mollusks Tarebia granifera, Corbicula fluminea, and Melanoides tuberculata accounted for 89.8 and 60.1 % of the abundance for the Grijalva and Usumacinta rivers. The maximum diversity values were in Lacantún section (Usumacinta) (H’=4.49, J’=1.14, D=1 and Margalef 22.76), and seasonally in northern winds (H’=3.42, J’=0.85 and Margalef 15.19), meanwhile, dominance was in dry (D=0.93). The dominant trophic groups were scrapers (74 %) and filter feeders (11 %), with maximum values in the Ostitán section (Grijalva) in rainy season. The collectors (10 %) were present in four sections, with the maximum value in the Tres Brazos section (Usumacinta) in the dry season. However, environmental variation reflects changes in the diversity of macroinvertebrates due to the function of these tropical rivers and their dependence on natural variation, hydraulic connectivity, and flow regulation. It is the first study that addresses the diversity of macroinvertebrates (three taxonomic groups) in two of the largest rivers in the country with contrasting ecohydrological conditions.
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