Volume 14, Number 37: 14 September 2011
In a recent study of the effects of seawater contamination on the tolerance of coral larvae to high sea surface temperatures, Negri and Hoogenboom (2011) discovered that a 50% reduction in the copper concentration of seawater resulted in a 3.5°C increase in the degree of heat that can be tolerated by coral larvae; and they report that a 50 to 80% reduction in dissolved inorganic nitrogen runoff may raise the threshold for high-temperature-induced coral bleaching by 2°C, as suggested by the work of Wooldridge (2009), thereby demonstrating that local actions to remedy local pollution problems can enable earth's corals -- and likely many other forms of marine life as well -- to much better withstand the life-threatening effects of global warming.
Kelly et al. (2011) describe analogous findings with respect to the life-threatening phenomenon of ocean acidification. They begin by noting that "several studies document acidification hot spots, patches of ocean water with significantly depressed pH levels relative to historical baselines occurring at spatial scales of tens to hundreds of square kilometers (Feely et al., 2008, 2010)," noting that "local studies in the Kennebec River plume in the Gulf of Maine (Salisbury et al., 2008), the Chesapeake Bay (Waldbusser et al., 2011), and the Manning River estuary in New South Wales, Australia (Dove and Sammut, 2007), illustrate that freshwater inputs, pollutants, and soil erosion can acidify coastal waters at substantially higher rates than atmospheric CO2 alone." And they add that "additional local phenomena -- such as sulfur dioxide precipitation (Doney et al., 2007), hypoxia (Kemp et al., 2005), eutrophication (Borges and Gypens, 2010; Waldbusser et al., 2011), and both emissions and runoff from acidic fertilizers (Dentener et al., 2006) -- can intensify these localized hot spots," which thus become places where marine life is more sensitive to the stress of both global warming (due to any cause) and the modest degree of whole-ocean acidification that is induced by the ongoing rise in the air's CO2 content.
Fortunately, the strength of these local stressors can be significantly reduced by local responses. The seven scientists write, for example, that something as simple as "returning crushed shell material to coastal habitats to approximate densities found in healthy clam populations can substantially increase pH and mitigate localized acidification impacts on clams (Green et al., 2009; Waldbusser et al., 2010)." They also indicate that implementing measures that reduce residential and agricultural runoff "can minimize beach and river contamination and algal blooms, while reducing pollutants that acidify the local coastal ocean."
Some of the remedial measures that they list in this category are "stormwater surge prevention (e.g., holding tanks), coastal and riparian buffers (areas of vegetation near land-water intersections), intact wetlands, and improved onsite water treatment facilities," which they describe as "effective measures to address watershed runoff and associated pollutants." And as a side effect, they state that controlling coastal erosion "could markedly benefit coastal ecosystems by reducing nutrient and sediment loading of water and protecting the physical integrity of the habitat itself."
In concluding this highly abbreviated report, it is clear that simple "good housekeeping habits" on the part of humanity can make a world of difference to the marine life of the planet's coastal waters; and that difference can play a huge role in helping such species to better cope with the modest amount of ocean acidification that has been produced by the CO2-emitting activities of man since the inception of the Industrial Revolution, as well as that which will yet be produced by all of the CO2 that will be emitted to the atmosphere by the activities of humanity throughout the remainder of the age of fossil fuels, as per the insightful analysis of Tans (2009).
Sherwood, Keith and Craig Idso
References
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