Human activities are impacting ecosystems on a global scale; Vitousek et al. (1997a) asserted that no ecosystem on the Earth’s surface is free of human influence. The land, atmosphere, and hydrosphere have all been altered to varying degrees. Up to 50% of the Earth’s land area has been transformed or degraded (Vitousek et ai., 1997a). As a result of stratospheric ozone depletion, intensities of biologically damaging ultraviolet radiation (UVB) at 20°N latitude between April and August now exceed the June 1969 (summer solstice) maximum (Shick et al., 1996). Carbon dioxide concentration in the atmos- phere has increased by nearly 30% since the beginning of the Industrial Revolution (Schimel et ai., 1995), with potential influences ranging from climate changes to altered ocean chemistry. Human activities have effectively doubled the annual transfer of nitrogen from the atmospheric pool of N2 to biologically-available fixed nitrogen (Schnoor et al., 1995; Vitousek et al., 1997b). Much of this fixed nitrogen, along with nitrous oxides from fossil-fuel burning (e.g., Prinn et al., 1990), is washed by the rains into aquatic systems.
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- Larger Foraminifera as Indicators of Coral-Reef Vitality
- Springer US
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