Investigations in Pacific Northwest Glacier Biological Communities
North Cascades National Park
Paula L. Hartzell, Biology Department
Clark University, Worcester, MA
Glaciers hold about 75% of the world's freshwater supply and cover approximately 10% of the earth's land surface. In the Pacific Northwest of North America, glaciers supply up to one third streamflow during the dry season, yet are experiencing an average terminal retreat greater than 25 m per year. The organisms that live on these glaciers offer high potential for biotechnological applications through adaptations to frequent freeze-thaw and high levels of ultraviolet light exposure. Few of these cryobionts have been described, and their biomass and biodiversity undocumented.
During the 2002 and 2003 field seasons, Hartzell collected over 1500 microbial and macroinvertebrate samples from 23 glaciers across the Pacific Northwest, including glaciers in Montana, Alberta, British Columbia, Alaska, Washington and Oregon. Multidisciplinary analysis includes microbial and macroinvertebrate identification, density, and biomass assessment, with comparisons between habitat type, glaciers, and regions. GIS technology is employed in spatial analysis of ecological and glaciological data. Additional morphological and molecular analysis is underway for the model organism, glacier ice worms (Mesenchytraeus solifugus).
Microbial communities appear to be dominated by unicellular algal species, but bacteria, fungi, multicellular algae, and protozoa also form a significant part of the assemblages. Microbial community structure and density vary by depth, substrate, as well as geographically, and may be correlated with macroinvertebrate density. Microbial densities appear to range between 0 to more than 350 per ul, with densities more commonly around 1.5 organisms/ul. For a glacier with an outflow of 28 cubic meter/second, the glacier is contributing over 42 billion organisms/second downstream in the summer!
Both microbial and macroinvertebrate densities are most strongly effected by time of day, with migration through snow and ice part of the diurnal routine. Substrate (snow, firn, ice, pool, slow stream, fast stream) appears to be a critical factor in both microbial and macroinvertebrate assemblage, providing proper substrate and probably chemistry. Slope and aspect do not appear to be important factors in relation to macroinvertebrate density. There does appear to be geographic differences in macroinvertebrate assemblages, particularly east to west (more than north to south), as well as by glacier type surface (dominantly ice, firn, avalanche, or loose snow). Smaller glaciers appear more likely to experience local extinctions, although this has not been proven conclusively.
Molecular analysis based on nuclear 28S and mitochondrial Cox1 DNA, places glacier ice worms monophyletically as an early branch of Tubificina. Molecular as well as morphological data is being used to trace the history and population dynamics of this taxa, an excellent model for the effects of isolation and fragmentation. Preliminary analysis suggests that there a more complex history, and/or more gene flow, between populations than previously believed. We were also surprised to find that the most diverged populations are those in British Columbia, compared to populations in Alaska and Washington. We will be working out the reasons behind this apparent paradox.
Module laboratory research has allowed independently motivated undergraduates to plan their own projects, be trained in standard laboratory techniques, and present their findings in written and oral presentation. The project has provided leadership and planning opportunities for graduate students, under the guidance of faculty, in existing laboratory facilities provided by Clark University. When laboratory work is complete, study data will be used to infer relationships between biological communities, habitats, and geographic location; to quantify glacier retreat and predict future status; to identify existing biodiversity; and to make recommendations for prioritization of future management and research needs.
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