Historical Ecology - N in oceans past
Eutrophication is considered one of the greatest threats to the world's oceans.
Yet, we know very little about the timing of eutrophication in the oceans, and what sources of nutrient pollution have been involved over time. My opinion is that nutrient loading began when land-clearing was widespread. As most marine systems are N-limited, it likely took many decades of N loading to "saturate" entire ecosystems. In some ways, benthic and pelagic marine systems can be viewed as a sponge, capable of assimilating and storing large quantities of nitrogen, and tightly recycling it among biota. In this way, biology can "mask" chemistry, essentially locking up nutrients in biomass. Such a process can prevent the detection of dissolved nitrogen in seawater, even though the process of eutrophication has already begun. If we only rely on concentration measurements then we may not detect increasing nitrogen concentrations until the ecosystem has reached an overloaded state.
1. DM Baker, L Weigt, M Fogel, N Knowlton (2013) Ancient DNA from coral-hosted Symbiodinium reveal a static mutualism over the last 172 years. PLoS ONE 8(2): e55057. DOI 10.1371.journal.pone.0055057 (link)
2. DM Baker, K Webster, K Kim (2010) Caribbean octocorals record changing carbon and nitrogen sources from 1862-2005. Global Change Biology, 16(10), 2701-2710.