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 A
biogeochemical perspective on the reactivity of dissolved organic matter in natural waters: from Antarctica to the Arctic
In natural waters, dissolved organic matter (DOM) is ubiquitous and is comprised of compounds derived from degradation of both plant and microbial precursor organic materials. A current trend is that DOM concentrations in lakes and streams are increasing in
north temperate regions and the Arctic, which is referred to as “browning” of natural waters, and reflects greater DOM runoff in watersheds. In addition to watershed DOM sources, DOM is produced by plants growing in the nearshore zone of lakes and rivers,
and by algae growing in the water column or on the streambed. With the earlier loss of ice-cover in the northern hemisphere, algal growth is starting sooner and algal DOM production is becoming a more important source of DOM. In turn, the concentration and
chemical quality of DOM influence the productivity of these aquatic ecosystems. For example, light absorption by the yellow-colored humic fraction of DOM controls the depth of the photic zone, where algae have enough light to grow, and acts as a sunscreen
controlling the UV stress due on aquatic biota. DOM is of interest to environmental engineers for several reasons. For example, the transport of trace metals and organic pollutants and the production of disinfection by products in drinking water treatment
can be controlled by interactions with DOM. Further, environmental engineers use similar methods for chemical characterization of DOM as biogeochemists and aquatic ecologists, although these research communities address different questions. This talk will
discuss how an understanding of ecological and biogeochemical processes in lakes and streams can provide useful complementary insight beyond chemical characterization to understand and manage current environmental engineering issues involving DOM. Examples
will be presented of studies conducted in diverse settings, such as the McMurdo Dry Valleys in Antarctica, the Okavango Delta in Botswana, and the arctic tundra in Alaska.
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