Final Report Summary - PALEOGENIE (PAst Links in the Evolution of Ocean’s Global ENvIronment and Ecology)
We started with the geological record of plankton – represented by invisible-to-the-naked-eye ‘nannofossils’. These, we analyzed, in unprecedented detail from the end of the Cretaceous (65 million years ago), when the Earth was hit by a giant asteroid, and for 13 million years after, following how plankton and marine ecosystems (the base of the food chain in the ocean) evolved and recovered from the catastrophe. We find, after about 2 Myr of exceptional ecosystem instability which saw a repeated pattern of species evolving, briefly ruling the ocean, and then going extinct again (as if a god kept re-rolling the dice), that a ‘healthy’ global carbon cycling was re-established with only relatively few different species of plankton (i.e. a ‘low species diversity’). It then took about 8 Myr for plankton diversity comparable to pre-extinction levels (or the modern ocean) to finally re-establish but to no apparent further affect (on the global carbon cycle). Ecosystem stability therefore seems not to be determined by sheer numbers of species, but rather, through the establishment and/or retention of some key individual taxa that fulfill specific and vital ecological and/or biogeochemical roles. In other words: ecological diversity does not seem to matter in the bigger picture (of global carbon cycling), just as long as the key players in the ecosystem are all present.
We then moved to the virtual world, and numerical models. We created a novel new ecosystem and added this to a computer representation of global carbon cycling and climate. We have found that this combined model was (pleasingly!) capable of reproducing many of the key features of plankton productivity in the ocean today. Then, for good measure, we allowed the plankton to evolve in the model. Having so many possible different plankton species appearing then got too numerically expensive to calculate, so we went back to our basic high school maths and the multiplication of matrices (but in a rather powerful and efficient way on supercomputer-power chips) to calculate how the ocean circulates and moves dissolved nutrients and plankton cells around. Combining brute computing power with an advanced marine ecosystem model then gave us a unique virtual world of interacting environment (nutrient recycling in the ocean interior and supply to the ocean surface) and life (plankton evolving or going extinct in response to their competitors and predators and changing food/nutrient availability) that we could play games (god) with.
Currently, we are bringing the new model and data together in a unique attempt to better understand how sensitive marine ecosystems are to global environmental change as well as how (or if) they recover. (Watch this space ...)