Jeremy Jackson, director of the Scripps Center for Marine Biodiversity and Conservation, cites the synergistic effects of habitat destruction, overfishing, ocean warming, increased acidification and massive nutrient runoff as culprits in a grand transformation of once complex ocean ecosystems. Areas that had featured intricate marine food webs with large animals are being converted into simplistic ecosystems dominated by microbes, toxic algal blooms, jellyfish and disease.

Dead zones in the coastal oceans have spread exponentially since the 1960s and have serious consequences for ecosystem functioning. The formation of dead zones has been exacerbated by the increase in primary production and consequent worldwide coastal eutrophication fueled by riverine runoff of fertilizers and the burning of fossil fuels.

The onset of major glaciations in the Northern Hemisphere about 2.7 million years ago was most probably induced by climate cooling during the late Pliocene epoch. These glaciations, during which the Northern Hemisphere ice sheets successively expanded and retreated, are superimposed on this long-term climate trend, and have been linked to variations in the Earth's orbital parameters.

Oceanic anoxic events (OAEs) were episodes of widespread marine anoxia during which large amounts of organic carbon were buried on the ocean floor under oxygen-deficient bottom waters. OAE2, occurring at the Cenomanian/Turonian boundary (about 93.5 Myr ago), is the most widespread and best defined OAE of the mid-Cretaceous.