SUPPLYING NUTRIENTS TO SEAFOOD THROUGH TIME

In his classic essay "Seafood through time," Richard Bambach identified a series of changes in late Mesozoic marine faunas and ascribed them to evolutionary events on land, specifically the rise of flowering plants. Bambach reasoned that increases in the abundance and mechanical strength of top predators (Vermeij's Mesozoic marine revolution), the mean size of marine invertebrates, and their mean rates of energy consumption all required expansion of the nutritional support for marine life. In Bambach's view, the necessary nutrients were supplied by angiosperm-facilitated increases in erosional run-off from continents. Bambach's proposal that biological innovations engendered biological responses is attractive, but is angiosperm radiation the only event we need to worry about, or even the right event? And might Mesozoic changes in the physical structure of continents and oceans have influenced marine evolution as much or more than land plants? For example, continental weathering reflects elevation, not just vegetation, so increases in marine biomass could reflect physical as well as biological events on land. Angiosperm expansion into two specific coastal habitats, mangroves and sea grass beds, might well have exerted a differentially strong influence on shelf and platform faunas. Moreover, algal macrobenthos diversified to support new and productive shelf ecosystems, including kelp forests. And in the open ocean, far from the direct influence of continental run-off, primary production shifted from cyanobacteria (Chl a) and green algae (Chl a+b) to three groups of chlorophyll a+c-bearing phytoplankon: the dinoflagellates, prymnesiophytes, and diatoms. The three clades radiated at different times and in different environments, but collectively they fomented a Mesozoic marine revolution of primary producers. The extent to which changing oceanographic conditions facilitated this radiation remains uncertain. Whatever its causes, primary production in shelf seas changed during the Mesozoic and Cenozoic in ways that paralleled and undoubtedly influenced faunal evolution. Understanding the intertwined effects of biological innovation and environmental change on seafood through time provides a worthy challenge for accelerating research in geobiology and Earth system sciences.