Schematic of human impacts on ocean biogeochemistry either directly via fluxes of material into the ocean (colored arrows) or indirectly via climate change and altered ocean circulation (black arrows). The gray arrows denote the interconnections among ocean biogeochemical dynamics. Note that many ocean processes are affected by multiple stressors, and the synergistic effects of human perturbations is a key area for further research.

By Scott C. Doney Abstract: Climate change, rising atmospheric carbon dioxide, excess nutrient inputs, and pollution in its many forms are fundamentally altering the chemistry of the ocean, often on a global scale and, in some cases, at rates greatly exceeding those in the historical and recent geological record. Major observed trends include a shift in the acid-base chemistry of seawater, reduced subsurface oxygen both in near-shore coastal water and in the open ocean, rising coastal nitrogen levels, and widespread increase in mercury and persistent organic pollutants. Most of these perturbations, tied either directly or indirectly to human fossil fuel combustion, fertilizer use, and industrial activity, are projected to grow in coming decades, resulting in increasing negative impacts on ocean biota and marine resources. Marine Chemistry and Geochemistry Department, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA. E-mail: sdoney@whoi.edu The ocean plays a pivotal role in the global biogeochemical cycles of carbon, nitrogen, phosphorus, silicon, and a variety of other biologically active elements and chemical compounds (1, 2). Human fossil-fuel combustion, agriculture, and climate change have a growing influence on ocean chemistry, both regionally in coastal waters and globally in the open ocean (3–5) (Fig. 1). Some of the largest anthropogenic impacts are on inorganic carbon (6), nutrients (4, 7), and dissolved oxygen (8, 9), which are linked through and affect biological productivity. Seawater chemistry is also altered, some times quite strongly, by the industrial production, transport, and environmental release of a host of persistent organic chemicals (10) and trace metals, in particular mercury (11), lead (12), and perhaps iron (13). Marine biogeochemical dynamics is increasingly relevant to discussions of ecosystem health, climate impacts and mitigation strategies, and planetary sustainability. Human-driven chemical perturbations overlay substantial natural biogeochemical cycling and variability. Key scientific challenges involve the detection and attribution of decadal and longer trends in ocean chemistry as well as more definitive assessments of the resulting implications for ocean life and marine resources. …

The Growing Human Footprint on Coastal and Open-Ocean Biogeochemistry, Science 18 June 2010: Vol. 328. no. 5985, pp. 1512 – 1516 DOI: 10.1126/science.1185198