Year of Award

2023

Document Type

Thesis

Degree Type

Master of Science (MS)

Degree Name

Resource Conservation

Department or School/College

W.A. Franke College of Forestry and Conservation

Committee Chair

Ashley Ballantyne

Commitee Members

Ben Colman, Sarah J. Halvorson

Keywords

Lakes, ecosystem metabolism, littoral, pelagic, ecosystem services, human perceptions

Subject Categories

Nature and Society Relations | Terrestrial and Aquatic Ecology

Abstract

Mountain lake ecosystems are critical in their roles in global biogeochemical cycling and providing vital ecosystem services, including freshwater resources, ecological habitats, and recreational opportunities. Ecological processes in mountain lakes, especially those occurring in the littoral, or near-shore zones, are linked to society and can be negatively influenced by human behavior, consequently threatening ecosystem services a lake provides. To investigate this problem, this study interrogates two inter-related issues. First, I assessed ecosystem metabolic services of biological activity that demonstrate a lake’s role in carbon cycling through sampling and monitoring a series of mountain lakes. During the summer of 2022, we selected three lakes – Lower Oregon Lake, Middle Oregon Lake, and Missoula Lake - located in Lolo National Forest that vary in terms of elevation, watershed, and bathymetry. We estimated metabolic processes based on in situ daily changes in measured dissolved oxygen, light, and temperature in both littoral and pelagic zones. Our findings strongly suggest spatial variability of gross primary productivity (GPP) and ecosystem respiration (ER) within mountain lakes linked to changes in physical and chemical variables across locations. Observed seasonal variations of GPP and ER may be induced by lake temperature stratification and mixing ultimately causing shifts in metabolic state. Notable differences in activity between zones within these lakes, as well as among lakes inhibit the ability to quantify whole-lake status based on single estimates. Though differences exist in relevant predictors, both littoral and pelagic zones are predominately influenced by chemical constituents compared to temperature. Second, we examined how summer-time visitors interact with these lakes and how they perceive the ecosystem services provided by these lakes. A public-intercept method was employed to capture visitors' perceptions related to lake utility, observed properties and changes, and human influence. Results from the surveys indicate that visitors have strong perceptions of cold temperatures, increased visitation, and a distinctive clear, pristine beauty of Montana lakes. Highly valued ecosystem services include recreation, habitat, and surface water uses. Perspectives of human impacts and societal responsibility are inconsistent, yet respondents recognized water temperature, algae presence, and water chemistry as important indicators of change in lake ecosystems. Survey data captured at the lakes suggests that perceptions correspond with the measurable biophysical data. Thus, our findings illustrate that ecosystem metabolism and human perceptions are inextricably linked. Visitors observed and identified ecological changes in these Montana lakes that are linked to the first part of the study; based on concerns of change that threaten valued services in local lakes, visitors express a need for initiatives for conservation Montana’s pristine mountain lakes.

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