Understanding the Relationships between Plant Communities, Fish Communities, and Sediment Chemistry in Pristine Shallow Lake Wetlands, Red Lake, MN

Abstract

Over 90% wetland loss in many areas of the United States has triggered extreme concern for declining biodiversity and loss of ecosystem services. Studies assessing ecological characteristics of unaltered wetlands are critical to interpreting potential responses to anthropogenic changes and how ecosystem characteristics and services might respond to future climate dynamics. Previous research shows fish and plant communities play an important role in shallow lake ecology by creating stability within the clear state. Understanding these mechanisms in a pristine setting is important for successful conservation and restoration. Our objectives, part of a long term monitoring study (2009-2015), were 1) Evaluate patterns in multi-element concentrations of pore water along a gradient from upland areas through emergent vegetation to the open water of shallow lake wetlands 2) Assess seasonal changes of multi-element concentrations of pore water during the growing season of shallow lake wetlands 3) Measure the influence of fish communities species composition on plant communities species composition 4) Evaluate how sediment chemistry impacts plant communities. We evaluated pore water chemistry on two lakes using dialysis vials from June-October 2014. We selected 24 shallow lakes located within Red Lake Nation Indian Reservation, MN, USA to conduct the remaining objectives. At each lake we assessed fish community structure and abundance using fyke nets and experimental gill nets for a 24-hr period during July. Aquatic and emergent vegetation was assessed simultaneously by rake throws and Daubenmire frame, and sediment samples were collected by taking a surface grab sample. Sediment samples were taken in the open water and emergent vegetation zones. Pore water did not change across a gradient from upland to open water, but did change over the season from June to October. We found fish community composition did not change significantly from 2009 to 2015, but fish biomass significantly decreased from 2009 to 2015. No species-specific relationships between vegetation and fish existed, but species specific relationships existed between vegetation and sediment characteristics in both the open water and emergent vegetation zones. Results will be used as reference points for restoration and conservation, and serve for a better understanding of shallow lake state stability.