Approaching questions of aquatic biogeochemistry from the perspective of �hotspots� and/or �hot moments� allows for integration of these results within the broad concepts of aquatic ecosystem function. One example is the role of sunlight in determining the structure of stream ecosystems, not only by controlling photosynthesis, a theme of the River Continuum Concept (RCC), but also by driving diverse photochemical processes. These photochemical processes can chemically transform nutrients, dissolved organic material and many trace constituents. From a biogeochemical perspective, the noonday sun irradiating a stream or river reach represents a �hot moment� that can have a sustained ecological effect. The changes occurring over a day-night cycle are superimposed upon seasonal changes in light regime and in hydrologic regime. Incorporating these dynamic processes into the broad scale of the RCC and into monitoring approaches may be useful in understanding the current effects of the substantial changes in water quality, land use and hydrologic regime.

Morning, noon, and night: DOM photochemistry and understanding the biogeochemical pulse of river ecosystems

248th National Meeting (2014)

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