What Are the Relationships between Plankton and Macroinvertebrates in Reservoir Systems?

Abstract

Macroinvertebrates and plankton play crucial roles in reservoir food webs; however, their relationships have received limited attention. This study investigates the associations between plankton and macroinvertebrates in fifty selected reservoirs. During the spring season, significant concordances were observed in species richness between phytoplankton and zooplankton, as well as between zooplankton and macroinvertebrates. In contrast, during the summer season, the concordance in species richness between phytoplankton and macroinvertebrates was higher compared to other assemblages. Although macroinvertebrates showed a strong connection with phytoplankton in terms of species richness in both seasons, the congruencies were not statistically significant. Partial least squares regression (PLSR) analysis revealed that the densities of phytoplankton, Chlorophyta, Cyanophyta, and protozoans significantly influenced the total macroinvertebrate density in both seasons. Additionally, the densities of mollusks and aquatic insects were affected by the densities of Chlorophyta and Cyanophyta, while the density of oligochaetes was influenced by the density of Chlorophyta. These findings indicated that phytoplankton and zooplankton serve as primary food sources for macroinvertebrates, highlighting the close relationship between plankton and macroinvertebrates in reservoir systems. Moreover, the results of formative measurement models indicated a strong association between zooplankton and macroinvertebrates during the spring, whereas phytoplankton and macroinvertebrates exhibited a close association during the summer. The substantial concordance in density between phytoplankton and zooplankton revealed by the formative measurement models confirmed that assemblages with similar body sizes exhibit stronger concordance compared to those with significant differences in body size.