Changing UV warming

Land use and climate change

Atmospheric circulation

Mixing

Land use and climate change

Mixing

Mixing

CDOM

Reduced UV exposuie

Reduced productivity

Altered II Changes in N, S. 1 decomposition, H & metals cycling |

Figure 1. Schematic illustrating factors that influence the effects of solar UVR on aquatic ecosystems. Aquatic biogeochemical cycles are affected by increased UVR caused by stratospheric ozone depletion and its interaction with other co-occurring environmental changes such as global warming and land use change. Changes in precipitation chemistry are caused by UV-induced photoreactions in cloud droplets and changing climate affects the frequency and intensity of precipitation which in turn affects UV penetration and UV-induced processes in freshwaters and the sea (see text for additional explanation). Key: ROS reactive oxygen species, principally hydrogen peroxide; DMS dimethyl sulfide; COS, carbonyl sulfide; CO carbon monoxide; C02 carbon dioxide; CDOM chromo-phoric dissolved organic matter, the primary UV absorbing substance in aquatic environments; DOC dissolved organic carbon.

version of organically bound nitrogen into biologically available inorganic N; conversion of refractory organic matter into lower molecular weight, biologically available organic compounds; photoinduced changes in the optical properties of DOM; and changes in the redox state of the upper ocean and freshwaters through formation of peroxides and changes in transition metal speciation.

The cycles of various elements are discussed separately in this chapter, but it should be emphasized that biogeochemical cycles are tightly interwoven and are subject to significant feedback interactions. This paper is not intended to provide a detailed review of the burgeoning research in this area, but rather to provide the reader with a glimpse of the exciting studies that are taking place and the types of measurement approaches and concepts that are being applied. Wherever possible, recent reviews are cited to provide more background to this chapter. Excellent overviews of global biogeochemical cycles are available [1,2], and several useful reviews related to topics considered here have recently been published [3-12].

0 0

Post a comment