Co-correspondence among aquatic invertebrates, fish, and submerged aquatic plants in shallow lakes

Fish and aquatic plants influence aquatic invertebrate assemblages in shallow temperate lakes, but estimating their relative influence is difficult because invertebrates respond to multiple factors operating simultaneously at various temporal and spatial scales. Co-correspondence analysis (CoCA) may prove useful for clarifying community relationships. We sampled assemblages in 104 shallow lakes in 5 study areas across 4 ecological regions of Minnesota, USA. We used CoCA to test for patterns among aquatic invertebrates, submerged plants, and fish. After controlling for influences of fish with CoCA, we used direct gradient analysis to assess influences of study area, lake state (turbid or clear), and watershed size on the abundance of zooplankton and macroinvertebrates. CoCA indicated high co-correspondence between fish and macrophytes across study areas, with weaker associations among zooplankton, macroinvertebrates, and fish. After removing the effects of fish, zooplankton and macroinvertebrates showed different relationships to environmental variables. Lake state and study area explained significant remaining variance in zooplankton, whereas study area and relative abundance of macrophytes explained remaining variance in macroinvertebrates. Among-lake patterns in submerged macrophytes were associated with fish presence and abundance. Invertebrates were related to lake state, fish abundance, and extent of submerged aquatic plants, and patterns differed between zooplankton and macroinvertebrates and among study areas. Species-level relationships among invertebrates, fish, and macrophytes were weaker than community-level patterns described in previous studies. This result suggests that community-scale influences of fish and submerged macrophytes on aquatic invertebrates may be strong and may mask species-level relationships in shallow lakes.