A one ocean model of biodiversity

The history of life is written in the ocean, and the history of the ocean is written in DNA. Geologists have shown us that hundreds of millions of years of ocean history can be revealed from records of a single phylum in cores of mud from abyssal plains. We are now accumulating genetic tools to unravel the relationships of hundreds of phyla to track this history back billions of years. The technologies demonstrated by the Census of Marine Life (CoML) mean that the ocean is no longer opaque or unknowable. The secrets of the largest component of the biosphere are knowable. The cost of understanding the history of ocean life is not cheap, but it is also not prohibitive. A transparent, open ocean is available for us to use to understand ourselves. This article develops a model of biodiversity equilibration in a single, physically static ocean as a step towards biodiversity in physically complex real oceans. It attempts to be quantitative and to simultaneously account for biodiversity patterns from bacteria to whales focusing on emergent properties rather than details.Biodiversity reflects long-term survival of DNA sequences, stabilizing “ecosystem services” despite environmental change. In the ocean, mechanisms for ensuring survival range from prokaryotes maintaining low concentrations of replicable DNA throughout the ocean volume, anticipating local change, to animals whose mobility increases with mass to avoid local change through movement. Whales can reach any point in the ocean in weeks, but prokaryotes can only diffuse. The high metabolic costs of mobility are offset by the dramatically lower number of DNA replicates required to ensure survival. Reproduction rates probably scale more or less inversely with body mass. Bacteria respond in a week, plankton in a year, whales in a century.We generally lack coherent theories to explain the origins of animals (metazoans) and the contributions of biodiversity to ecosystems. The One Ocean Model suggests that mobile metazoans paved the way for their own energetic life styles by decreasing the amount of primary production sinking to feed the benthic anaerobic prokaryotes. Increasing metazoan mobility and diversity ensured that less and less production sank and accelerated development of the aerobic oceans they require. High biodiversity among middle-sized organisms stabilizes the system, but rapid environmental changes can decrease diversity in a positive feedback loop ending in mass extinction events and the return of the anaerobes. The oceans have gone through this cycle several times. Global warming may be a mild flu compared to “the revenge of the microbes”.