Mount Rainier's Mountain Lakes as Early Warning Systems: 2013 Monitoring Brief

Hidden by cloud, mist and snow for much of the year, high mountain lakes are ideal places to watch for environmental change in the Pacific Northwest high country. They gather the effects of many stresses over a wide area — climate change, air pollution, visitors — into their chemistry and biology, making them something like living Petri dishes.

Blue Lake, Mount Rainier National Park. Image from the National Park Service

Pressures on the lakes

• Air pollution. Being so high, the lakes are especially exposed to nitrogen, ammonium, sulfur, mercury and other contaminants carried from the Puget Sound, Portland and Fraser Valley metro areas and from across the Pacific.
• Stocked fish. Many lakes in Mount Rainier, North Cascades and Olympic national parks were stocked with non-native fish, reshaping food webs and nutrient cycles.
• Climate change. Warmer air and water could shorten ice cover — and since the lakes are ice-free only part of the year, that would transform food webs, diversity and nutrients. Changes in glacier and snow melt could alter water flow too.
• Amphibians, key to lake food webs, face non-native predators and diseases, some possibly linked to climate change and visitors.

How the lakes are monitored

Mount Rainier's lakes have been studied since 1988. Long-term monitoring now covers Reflection, Louise, Mowich and Ethel lakes, plus six lakes in the North Coast and Cascades Network (NCCN) program — Blue, Allen, Upper Palisades, Upper Deadwood and two unnamed lakes.

Long-term monitoring lakes at Mount Rainier. Image from the National Park Service

Network lakes were randomly chosen from those that are entirely inside the park, 0.4–6.0 hectares in area, from 1,220 m up to the top of the subalpine zone, deeper than 2.5 m, not heavily fed by glaciers, reachable on foot in August–September, and without dense fish populations. Each is sampled once in mid-summer:

• water chemistry, chlorophyll, zooplankton, water clarity and depth profiles of oxygen, temperature, pH and conductivity at a buoy over the deepest point;
• year-round temperature loggers at surface, middle and bottom;
• water level, shoreline and snorkel surveys for amphibians, gill nets or hook and line for fish, aquatic insects, and the condition of the shoreline.

Crews measuring temperature and dissolved oxygen profiles. Image from the National Park Service

Early findings

Zooplankton. Mount Rainier's lakes had the most taxa (an average of 11.2), North Cascades 9.0 and Olympic the fewest (7.16). The water flea Holopedium gibberum, found in nearly every Rainier lake, turned up only at Rainier — evidence of regional differences.

Major zooplankton groups by park. Image from the National Park Service

Blue Lake, 2010: very dilute and clear — water clarity to 9.4 m, pH 5.68–5.69, low nutrients (total nitrogen 0.03–0.08 mg/L, total phosphorus 0.003–0.005 mg/L) and chlorophyll-a of 0.372 µg/L.

Dissolved oxygen, temperature and pH by depth, Blue Lake. Image from the National Park Service

Fish. Introduced fish live in four of the six network lakes and in about 30 lakes in the park: eastern brook trout, rainbow trout, cutthroat trout, prickly sculpin, and kokanee in Mowich Lake.

Setting gill nets to sample fish. Image from the National Park Service

Amphibians. Nine species use the park's lakes: northwest, long-toed, coastal giant and Van Dyke's salamanders; Cascades, Pacific tree and tailed frogs; the western toad; and the rough-skinned newt.

A northwest salamander seen on a snorkel survey in Lake Allen. Image from the National Park Service

Crescent Lake ice-out dates, 2005–2010. Image from the National Park Service

Depths of Lake Eleanor. Image from the National Park Service

Why it matters

The data will help managers understand the effects of air pollution and climate change, set criteria for restoring lakes harmed by non-native species, and spot the effects of backcountry visitors — and will serve as a baseline for predicting change.

Sources

Based on "Long-term Ecological Monitoring of Mountain Lakes, 2013," Mount Rainier Science Brief, by Barbara A. Samora and Rebecca A. Lofgren, Mount Rainier National Park, National Park Service; a work of the United States government in the public domain. Misspellings in the source ("Frasier Valley," "Onchorynchus") are corrected; its total dissolved solids figures repeat the total nitrogen values and are not given.