Cetaceans, Climate Change and Ocean Acidification

A Topic Overview by Cloe Waterfield, Twentyfifty, for Conscious Breath Adventures
November 2009

How will cetaceans be affected by climate change? It is now accepted that our use of fossil fuels is contributing to a warming planet. What does that mean for sentinel species such as the great whales? Will the humpback whales (Megaptera novaeangliae), breeding and calving on the Silver Bank of the Dominican Republic be affected? At the recent meeting of the Society for Marine Mammology in Quebec (October 2009) it was noted that “The Board of Governors of the Society of Marine Mammalogy is deeply concerned about the direct and indirect effects of climate change on marine mammals.” Conscious Breath Adventures is working with Twentyfifty, to bring you food for thought on this issue.

Since the beginning of the industrial revolution, we’ve added about 30% more carbon dioxide (CO2) to the atmosphere, primarily from burning fossil fuels. It is thought that CO2 levels (387 ppm) are the highest they have been for 200 million years. As CO2 traps the sun’s heat, global temperatures rise. The National Oceanic and Atmospheric Administration (NOAA) report, for 2009, surface ocean temperatures 0.92oF greater than the century average. The increases are greater on land and since the mid 19th century, global average temperatures have risen about 1.44oF.

Perhaps more importantly however, is that the oceans take up approximately a third of this extra CO2 a year. When CO2 dissolves into seawater we get carbonic acid which disassociates into hydrogen and bicarbonate ions. The extra hydrogen ions are slowly making the waters more acidic. Over the last century we’ve seen a 0.12 unit decrease in ph (which might sound small, but as the ph scale is logarithmic it equates to about 30% more hydrogen ions). Hydrogen ions quickly combine with any remaining carbonate ions to form bicarbonates. That limits the availability of carbonate for marine organisms that build their skeletons from calcium carbonate or aragonite.

Science shows a direct relationship between atmospheric CO2 concentration and ocean ph. By 2050, with CO2 levels expected to reach 450-500 ppm, the chemistry of the ocean will be so under saturated in carbonate ions that, for reefs and many marine creatures, it may well be the beginning of the end, a huge change in marine ecosystems as we know them.

The Royal Society of the United Kingdom concluded in its study of ocean acidification, “Without significant action to reduce CO2 emissions into the atmosphere, this may mean that there will be no place in the future oceans for many of the species and ecosystems that we know today.”

There is a direct correlation between ocean ph and atmospheric CO2 concentration, irrespective of global temperature and other greenhouse gases. Even if we reduce the temperature, if we do not curb CO2 emissions, these changes can still be expected. The magnitude and broad effects on marine systems is less well understood, most work in this relatively new field of study has been published post-2004.

But what does this mean for whales and dolphins? Current major threats to cetaceans include noise pollution, ship strikes, continued hunting and entanglement in fishing gear (bycatch alone is estimated to be responsible for the deaths of at least 300,000 cetaceans per year, nearly 1,000 every day). Climate change adds a number of additional elements, for example; range shifts related to warming waters, especially for already restricted species, increased shipping traffic (particularly for Arctic species), the concomitant noise pollution and the effect a more acidic ocean may have on prey species. Indeed, ocean acidification, the other CO2 problem, might be the gravest threat to marine species yet.

Many of the great whales feed on aggregations of plankton like the copepod Calanus finmarchicus in the Arctic or Krill (Euphausia superba) in the southern hemisphere, those aggregations themselves are typically related to specific environmental conditions. These animals build their shells or tests from calcium carbonate which they extract from seawater. As carbonate ions become less available, populations may be locally depleted. Couple that with competition from fisheries for these species (mostly to provide fish feed for aquaculture) and we can see that finding enough food at the right time in established feeding grounds may not be as straightforward as we move into the mid-part of the century.

For humpback whales, with worldwide distribution, relatively large populations (listed as vulnerable by the IUCN, with around 12,000 in the North Atlantic), and diets comprised largely by fish not solely planktonic species, the effects may not be as immediate as for range and prey restricted polar species. However, as a migratory species, traveling long distances to summer breeding grounds, any mismatch in the timing of peak food abundance may have negative effects.

If whales were forced to use alternate breeding and calving grounds (if diets were not adequate to support the travel distance, for example) this might mean using areas not legally protected like the Silver Bank. Scientists have also shown that sound will travel faster and farther in a more acidic ocean, exacerbating noise pollution. Humpbacks, known for their intricate and elaborate communication may be affected by this phenomenon.

So what can we do? We need to reduce our dependence on fossil fuels and stabilize atmospheric CO2 concentrations. This entails a sea change in the way we power society. Do we think it’s achievable? Absolutely; most of us would do anything for our kids and hopefully that includes saving the oceans for them. Procrastination, however, is no longer an option.

For sources for this overview and further reading, please see:

Burns, W.C.G, 2008 in Saving Biological Diversity: Balancing Protection of Endangered Species and Ecosystems, Askins, R.A.; Dreyer, G.D.; Visgilio, G.R.; Whitelaw, D.M. (Eds.), chapter available at: http://www.terrain.org/articles/21/burns.htm

Cao, L., Caldeira, K., Jain, A.K., 2007, Effects of carbon dioxide and climate change on ocean acidification and carbonate mineral saturation, Geophys. Res. Letters, Vol. 34, L05607

Elliott, W. and Simmonds, M. 2007. Whales in Hot Water? The Impact of a Changing Climate on Whales, Dolphins and Porpoises: A call for action. WWF-International, Gland Switzerland / WDCS, Chippenham, UK, available at www.panda.org/species

Orr et al. (2009) Research Priorities for Ocean Acidification available from: www.ocean-acidification.net

NOAA, 2009, http://www.noaanews.noaa.gov/stories2009/20090814_julyglobalstats.html

Rieser, A. 2009, Whales, whaling, and the warming oceans, in 20-Ton Canaries: The Great Whales of the North Atlantic - Symposium at Boston College Law School, Boston College Environmental Affairs Law Review, Vol. 36(2); i - 496, 178 pp.