[Coral-List] concurring with Forest

[Charles Birkeland]

For decades, ecologists have been evaluating the hypothesis that diversity supports stability. This is still being debated, but it is most often accepted. When considered at the higher levels of taxa (phyla and classes), coral reefs are possibly the most diverse of ecosystems. And yet as diverse as they are, when coral reef communities experience the deposition of scrap metal in areas relatively far from human settlements and exposed to massive water exchange with the open ocean (e.g., Kingman Reef, Rose Atoll), they can purportedly collapse into a system of black slime of prokaryotes. On the other hand, while in harbors or lagoons with a number of shipwrecks and with longer residency time of enclosed water (e.g., Pago Pago, American Samoa; Apra Harbor, Guam; Chuuk Lagoon and Beqa Lagoon), the surrounding coral communities persist or even benefit from the three-dimensional metal structures. As Forest mentioned, and I concurred in my previous missive, iron-limitation or other matters of context might be key factors determining differences among the reef systems’ responses to scrap metal. As suggested by Forest, coral reefs on basaltic islands might be less vulnerable to scrap metal than are those on atolls. But whether the difference is solely a result of relative availability of iron, or whether it is a combination of factors far away from human populations, it does call attention to the fact that the diverse coral reef systems are not resistant or stable and can be drastically affected by the availability or surplus of a few key nutrients. This whole matter is reviewed nicely in the ISRS Briefing Paper 3.  How can such a diverse system be so unstable with the input of any of these nutrients?


The prokaryotes are possibly directly affected by the iron, and the eukaryotic biota, no matter how diverse, are overwhelmed by the prokaryotes out of control. Paleontologist Peter Ward explained in his Medea hypothesis how, in the geological past, prokaryotes occasionally had global population growth out of control, altered the atmosphere and ocean chemistry, and caused mass extinctions of the more complex eukaryotes. He then listed a number of characteristics of the behavior of human populations that make humans the only species of eukaryote that behaves like prokaryotes. It is tempting to develop analogies between the prokaryotes with iron (or combination of substances and conditions) from scrap metal overwhelming the diverse coral reef community and humans with fossil fuels overwhelming the diverse biosphere, but I will refrain.


Chuck