Do Submerged Macrophytes Influence the Response of Zooplankton and Benthic Ostracoda to NaCl Salinity Gradients in Shallow Tropical Lakes?

Abstract

Both the increasing salinity levels and the decline of submerged macrophytes represent growing concerns in global freshwater ecosystems, posing a threat to water quality and various aquatic organisms. However, there is a limited understanding of the interactive effects of salinity and submerged macrophytes on zooplankton and benthic Ostracoda in tropical zones. To address this knowledge gap, we conducted a controlled experiment spanning 6 months, comparing the biomass of zooplankton (including copepods, cladocerans, and rotifers) and benthic Ostracoda in mesocosms with three levels of salinity, at the presence or absence of submerged macrophytes. Our results showed that in tropical zones, both zooplankton and benthic Ostracoda biomass exhibited a noteworthy decrease in response to increasing salinity, but the presence of submerged macrophytes did not have a significant influence on the zooplankton biomass. However, the presence of submerged macrophytes had a positive effect on the benthic Ostracoda biomass. Interestingly, submerged macrophytes had a strong interaction with salinity on the Ostracoda biomass, which increased with macrophyte presence under intermediate salinity conditions (2 g/L). In summary, our study sheds light on the interplay between salinity, submerged macrophytes, and the biomass of zooplankton and benthic Ostracoda in tropical freshwater ecosystems.