Cold-water carbonate production in Canadian waters.

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This project studies cold-water carbonate sediments in Canadian waters, and the marine plants and animals that make those sediments. Cool-water carbonate sediments can accumulate in non-tropical environments such as temperate and even polar continental shelves. Most Canadian waters fall into the coldest-water carbonate realm, but cold-water carbonate sediments in Canada have received little previous study, unlike well-studied regions like the southern Australian shelf, the Mediterranean Sea, or the Northwestern European continental margin. Many of the organisms that make these sediments, such as calcareous algae, bryozoans, barnacles, and cold-water corals, may be ecologically important in creating or structuring habitat for other invertebrates and fishes. Like tropical reefs, these biologically produced habitats, and the carbonate sediments they make, accumulate in a fine balance between carbonate production by organisms, and carbonate loss through biological erosion and dissolution. This balance is most fragile in the polar carbonate realm, where cold waters are corrosive, promoting dissolution, and biological erosion is generally fast. Carbonate systems are subject to at least two important anthropogenic threats: ocean acidification, and physical damage from bottom-contact fishing. These recent anthropogenic threats may push cold-water carbonates into net erosion and carbonate loss, similar to the geological consequences of ecological decline on tropical coral reefs.This research will assess the importance of the cold-water or polar carbonate system in Canadian waters, characterizing its composition, and measuring the balance between gross carbonate production and carbonate loss through bioerosion, fragmentation, and dissolution. This research will determine how the balance between production and loss varies by location and depth in Canadian waters, as a function of regional oceanography. The variation in rates of carbonate production by various skeletal organisms, such as bryozoans, barnacles, calcareous algae, and cold-water corals will be assessed. Since carbonate loss by dissolution and bioerosion are important drivers of the balance, this research program will also characterize rates of bioerosion and dissolution of the most abundant carbonate skeleton types, and how those rates vary. Field experiments on carbonate loss through bioerosion and dissolution will be deployed at various depths in waters of both Newfoundland and British Columbia. BC experiments will be deployed at the NEPTUNE cabled oceanographic observatory gas hydrates site within the oxygen minimum zone, where we have observed abundant deep-sea corals.Finally, we will assess the impacts of ocean acidification on both carbonate production and carbonate loss. Growth and breakdown experiments under laboratory conditions simulating ocean acidification in the deep sea will predict the impact of anthropogenic increases in atmospheric carbon dioxide concentrations on cold-water carbonate production and carbonate destruction in deep water environments.This research program will clarify the geological, biological, and oceanographic importance of the cold-water carbonate realm in Canada, and highlight similarities and differences between non-tropical carbonates in Canada and other regions of the world. Knowing where in Canadian waters the most sensitive biota and greatest net carbonate production occur will be important for habitat conservation, particularly as decreasing sea ice coverage in the Arctic makes more areas accessible to commercial fishing. Predicting the sensitivity of polar carbonate producing organisms to ocean acidification, will help determine how fragile or resilient polar carbonate systems are with respect to global climate change.