Biological Pump - Anthropogenic Changes

Anthropogenic Changes

Changes in land use, the combustion of fossil fuels, and the production of cement have led to an increase in CO₂ concentration in the atmosphere. At present, about one third (approximately 2 Gt C y−1) of anthropogenic emissions of CO₂ are believed to be entering the ocean. However, the biological pump is not believed to play a significant role in the elevation in CO₂. This is because the biological pump is primarily limited by the availability of light and nutrients, and not by carbon. This is in contrast to the situation on land, where elevated atmospheric concentrations of CO₂ may increase primary production because land plants are able to improve their water-use efficiency (= decrease transpiration) when CO₂ is easier to obtain. However, there are still considerable uncertainties in the marine carbon cycle, and some research suggests that a link between elevated CO₂ and marine primary production exists.

However, climate change may affect the biological pump in the future by warming and stratifying the surface ocean. It is believed that this could decrease the supply of nutrients to the euphotic zone, reducing primary production there. Also, changes in the ecological success of calcifying organisms caused by ocean acidification may affect the biological pump by altering the strength of the hard tissues pump. This may then have a "knock-on" effect on the soft tissues pump because calcium carbonate acts to ballast sinking organic material.