Ocean Acidification – Ecosystem Services Impacts IV: Supporting Services – the Nitrogen Cycle

This post is a continuation of the previous three posts. I will review supporting ecosystem services that are being impacted by ocean acidification (OA). Supporting ecosystem services affected by ocean acidification was challenging to understand, but writing this post helped me understand it better.

According to the United Nations Environment Programme, supporting services include “nutrient cycling and primary production which underlie the delivery of all the other services but are not directly accessible to people” (UNEP 2005). Specifically, according to Cooley, nutrient cycling is performed by coastal food webs, as well as coral reefs.

First it should be understood that the primary impact of OA on nutrient cycling is its impact on the carbon cycle. The drop in pH is reducing the calcium carbonate saturation, a compound that crustaceans, corals, and mollusks use to build their shells and exo-skeletons. Though this information is covered in previous posts, we may be curious to understand what other forms of nutrient cycling is impacted by ocean. According to blog-site the Scientific American, a CO2 induced acidity increase can disrupt the marine nitrogen cycle.

Nitrate, a form of nitrogen, is a nutrient needed by many plants and marine microorganisms to survive. Nitrate is created after certain microorganisms perform nitrification, where ammonium is converted to nitrate. According to the Scientific American, several studies indicate that a pH reduces the rate of nitrification, thus affecting various sorts of marine life. In one study, four separate ocean locations were sampled, and compared with unaffected control groups. The outcome of the study indicated that ocean acidification slowed nitrification between 8 to 38 percent.

Ocean nitrogen cycle and nitrification

 

The oceanic nitrogen cycle. Nitrfication is a conversion of Ammonium (NH4+) to Nitrate (NO3)

According to Beman (who performed this study, and published in December 21, by the Proceedings of the National Academy of Sciences, 2011): “less nitrification would make fewer nitrates available to the plants and organisms that use them to make vital proteins, making it more difficult for them to thrive. This in turn means less food would be available to the animals that eat those nitrate-using organisms,” impacting entire food webs.

While we just became experts on calcifiers impacted by OA, this new found knowledge just opened a whole new can of worms. Research should further investigate to what extend ecosystem services are impacted by the reduced rate of nitrification as a result of OA.

Source: United Nations Environment Programme (2005): http://www.unep.org/ecosystemmanagement/Introduction/tabid/293/language/en-US/Default.aspx

Source: Sarah R. Cooley et al. (2009), Ocean Acidification’s Potential to Alter Global Marine Ecosystem Services

Source: Scientific American: http://blogs.scientificamerican.com/observations/2010/12/20/ocean-acidification-may-disrupt-the-marine-nitrogen-cycle/

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