EPA's Vessel General Permit and Small Vessel General

Ocean acidification caused by increasing amounts of carbon dioxide (CO2) in the Earth’s
atmosphere poses a more wide-spread threat because virtually every major biological function
has been shown to respond to acidification changes in seawater, including photosynthesis,
respiration rate, growth rates, calcification rates, reproduction, and recruitment (London 2005,
Smith 2008).
At the same time as these changes in regional weather patterns and ocean productivity are
expected to occur, the oceans are expected to being increasingly acidic. Over the past 200 years,
the oceans have absorbed about half of the CO2 produced by fossil fuel burning and other human
activities. This increase in carbon dioxide has led to a reduction of the pH of surface seawater of
0.1 units, equivalent to a 30 percent increase in the concentration of hydrogen ions in the ocean.
If global emissions of carbon dioxide from human activities continue to increase, the average pH
of the oceans is projected to fall by 0.5 units by the year 2100 (Royal Society of London, 2005).
Although the scale of these changes would vary regionally, this resulting pH would be lower
than the oceans have experienced over at least the past 420,000 years and the rate of change is
probably one hundred times greater than the oceans have experienced at any time over that time
interval. More importantly, it will take tens of thousands of years for ocean chemistry to return
to a condition similar to that occurring at pre-industrial times (Royal Society of London, 2005).
Marine species such as fish, larger invertebrates, and some zooplankton take up oxygen and lose
respired carbon dioxide through their gills. Increased carbon dioxide levels and decreased pH
would have a major effect on this respiratory gas exchange system because oxygen is much
harder to obtain from surface seawater than it is from air (primarily because concentrations of
oxygen are lower in water). The processes involved in supplying oxygen to the gills means that
more carbon dioxide is removed from these aquatic animals than is removed from air breathing
animals of a similar size. This more ready removal of carbon dioxide from body fluids means
that the level and range of CO2 concentration in the bodies of water-breathing animals are much
lower than is the case for air-breathing animals. As a result, large water breathing marine
animals are more sensitive to changes in the carbon dioxide concentration in the surrounding
seawater than are large air-breathing animals.
This has important implications because higher ambient levels of carbon dioxide would acidify
the body tissues and fluids of these species and affect the ability of their blood to carry oxygen.
Experimental studies have demonstrated that acidosis of tissues decrease cellular energy use,
lower respiratory activity, and lower rates of protein synthesis (Pörtner et al. 2000, Pörtner et al.
2004)(Pörtner et al 2000, 2004). These changes would reduce the performance of almost every
physiological process of larger animals including their growth and reproduction (Langenbuch
and Pörtner 2002, 2003). By itself, this effect of climate change poses severe risks for
endangered and threatened anadromous and marine species. In combination with changes in
seasonal temperatures, formation of snow pack in terrestrial ecosystems, upwelling phenomena,
and ocean productivity, ocean acidification would lead us to expect the status of endangered and
threatened anadromous, coastal, and marine species to trend toward increasing decline over the
next three or four decades.
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