Abstract
Chlorophyll biomass in the surface ocean is regulated by a complex interaction of physiological, oceanographic, and ecological factors and in turn regulates the rates of primary production and export of organic carbon to the deep ocean. Mechanistic models of phytoplankton responses to climate change require the parameterization of many processes of which we have limited knowledge. We develop a statistical approach to estimate the response of remote-sensed ocean chlorophyll to a variety of physical and chemical variables. Irradiance over the mixed layer depth, surface nitrate, sea-surface temperature, and latitude and longitude together can predict 83% of the variation in log chlorophyll in the North Atlantic. Light and nitrate regulate biomass through an empirically determined minimum function explaining nearly 50% of the variation in log chlorophyll by themselves and confirming that either light or macronutrients are often limiting and that much of the variation in chlorophyll concentration is determined by bottom-up mechanisms. Assuming the dynamics of the future ocean are governed by the same processes at work today, we should be able to apply these response functions to future climate change scenarios, with changes in temperature, nutrient distributions, irradiance, and ocean physics.
Highlights
The ocean is one of the most important reservoirs of inorganic carbon and its ability to act as a long-term sink for CO2 is affected by phytoplankton through the flux of photosynthetically fixed carbon from the surface into the deep ocean, termed the biological pump
The standing stock of phytoplankton biomass is a primary determinant of the rates of primary production and export of carbon out of the surface ocean [1]
There is accumulating evidence that phytoplankton biomass and community composition are changing in response to climate change [2,3,4,5]
Summary
The ocean is one of the most important reservoirs of inorganic carbon and its ability to act as a long-term sink for CO2 is affected by phytoplankton through the flux of photosynthetically fixed carbon from the surface into the deep ocean, termed the biological pump. Physiologically detailed mechanistic models incorporate the growth response of several biogeochemically defined groups of phytoplankton to the availability of light and several different potentially limiting nutrients balanced by loss terms such as sinking and grazing by different classes of predators [9,10,11,12]. These physiologically mechanistic models can simulate relatively rapid changes in phytoplankton growth rate, community composition and chlorophyll biomass. Ongoing work on all these fronts yields a continually evolving view of phytoplankton and their interaction with the marine environment
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
