Speculations on impacts

As previously discussed, the Dry Valleys already have minimal nutrient inputs and microbial activity, and thus much of the organic matter is present as a remnant of past functioning rather than being a product of consistent cycling through the ecosystem.  So, predictions of decreased primary productivity, microbial biomass and increased abiotic breakdown of organic matter may have huge implications for a system already exhibiting low carbon turnover.

A visual representation of how interactions within ecosystems differ when they host vascular plants (a) versus the Dry Valleys (b) and (c), which only contain algae and mosses (extracted from Wall, 2007).

The ozone hole over the Antarctic continent is a process that occurs for the most part in Austral spring.  The timing of this UV-B increase may be one of the most important problems for Dry Valley communities.  Organisms in this system spend much of their time, probably entirely during winter months, in in “ametabolic states” (much like hibernation). They shut down their biological processes and wait out the winter until summer comes to raise temperatures above freezing and allow the organisms to access to water by thawing lakes and glaciers. If they are exposed to more of thus sun’s radiation earlier in the year, before they are up and active (so springtime rather than summer), they would have less time to respond and thus less defense against harmful UV-B (Wall, 2007).

Effects of UV-B radiation on Antarctic biota will primarily be seen on the soil surface and within the first few cm of depth, and these changes will likely in turn be detrimental to animals down the food chain. However, as alluded to in the Antarctic Ecosystems background section, high winds in the valleys can be major transporters of both organic matter and soil animal dispersal.  Thus, when these animals that are typically in safe soil depths are being carried by wind, they could be vulnerable to UV-B radiation and damaged before they arrive in new soils. In this case they are unavailable to colonize the new territory and promote ecosystem functioning there (Wynn-Williams, 1994).


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