The relative importance of salinization in lowland stream zooplankton: Implications of the ecosystem nutrient status

GUTIERREZ, MARÍA FLORENCIA; ANDRADE, VICTORIA SOLEDAD; FLORES-MENDEZ, DANIEL NINO; FRAU, DIEGO; LICURSI, MAGDALENA; NEGRO, LEANDRO

THE SCIENCE OF TOTAL ENVIRONMENT

Elsevier

Año: 2023 vol. 912

0048-9697

Salinization of aquatic systems is predicted to increase due to climate and land use changes.Nevertheless, community responses may be different according to the ecosystem characteristicsand contextual scenarios. Small flowing waters are particularly vulnerable to salinization, whichmay impact on the biodiversity and ecosystem processes, but this remains unclear. We conducteda study in 42 lowland streams characterized by overall high nutrient levels along a salinitygradient between 2 and 160 g L-1 to analyze changes in zooplankton structural and functionalmetrics, and the grazing effects of zooplankton on phytoplankton affecting the energy transfer.Generalized additive models revealed that the analyzed metrics were relatively influenced bysalinity, with factors related to trophic conditions playing an important role as well. Totalabundance and biomass decreased along the salinity gradient while increasing at intermediatesoluble reactive phosphorous concentrations (SRP) in the former and with a linear increase in theSRP in the latter case. Taxonomic richness decreased with salinity and dissolved inorganic nitrogen, with species replacement toward saline-tolerant ones according to the compositionaland optimums analyses. In opposite, functional richness did not display any specific trend withinthe environmental gradients. This explains why zooplankton compositional changes were notreflected into shifts in the grazing pattern on phytoplankton, which was in turn driven by SRPand dissolved oxygen concentrations. Further research is a critical requirement in these poorlystudied ecosystems for planning mitigation actions to the co-occurrence of eutrophication andsalinization in a fast changing world.