The model, described in the May 1st issue of Proceedings of the National Academy of Sciences, predicts an increase in the global number of phytoplankton between the year 2050 and 2060, including a rise up to 2% annually as ocean ecosystems evolve to compensate for projected declines in surface plankton . The model’s findings are important because they are based on a simulation that predicts a global population increase of 1,150,000 metric tons the equivalent of 10 million metric tons of seafood annually in the first decade of the period of global change. This is an increase nearly 10 times the number projected in our current projections for 2050 (which are based on more stable growth rates). In the model’s current form, this phytoplankton increase is likely to happen even faster in the future.
The study shows that ocean systems are not immune to climate change. As shown below, the model predicts changes in surface nutrient levels due to atmospheric carbon dioxide. In the long run, phytoplankton will take over the biomass of the food web, resulting in a decline in ecosystem biodiversity. At the same time, the model also suggests that phytoplankton can be compensated for a decline in a different planktonic food source, known as benthic foraminifera; the new model indicates that this is possible. As the phytoplankton biomass grows, the model’s simulated ocean nutrients gradually increase, while the nutrient-rich surface waters increase their carbonate burden. As shown in the graph above, phytoplankton have higher relative abundance and more carbonate capacity than the marine foraminifera, causing them, in theory, to take over the ocean. An imbalance on the ocean’s carbon cycle has already been revealed, and suggests some of the key factors causing imbalance are altered oxygen patterns, temperature and oxygen uptake.
The model used on the study shows that oceans, with their intricate and complex mechanisms for regulating benthic foraminifera, could be targeted by ocean producers. If a high concentration of organic material is carried to the bottom of the ocean, anaerobic processes degrade the organic matter. The ocean, with its intricate and complex mechanisms for regulating benthic foraminifera, could be targeted by ocean producers. One of the key factors affecting oceanic foraminifers’ interactions with the ocean as a whole (and phytoplankton especially) is the amount of phytoplankton. In a typical low-latitude ocean, the phytoplankton biomass tends to grow as the temperature increases, with a range of maximum to minimum values. A similar range for the ocean’s phytoplankton will increase in the future as changes in temperature and availability of nutrients increases. The model’s simulation of growth in the ocean biomass follows a similar pattern; the lowest productivity occurs after a decrease in the phytoplankton biomass; after a change in these two factors, the phytoplankton biomass slows but not substantially, until the phytoplankton biomass is sufficient. In a large-scale environment, carbon dioxide, which affects the phytoplankton, could also be a factor affecting growth. The oceanic foraminifera could be highly exposed to carbon dioxide due to changes in the ocean’s respiration rate. If the increased uptake of CO2 was large enough, it would further cause the ocean to lose its ability to function in an aqueous state.
To see an animation of the current, simulated sea level, and the changes in the Earth system, visit: http://www.nasa.gov/spaceimages/details.php?id=PIA18386
This work was supported by funding from the National Science Foundation and the UCI Ocean Institute and the UCI Department of Earth and Life Sciences. Further information on this work is available at: http://dx.doi.org/10.1073/pnas.190795711
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