Approximately half of all photosynthesis in the world takes place in the oceans.
Approximately 50% of the world's photosynthesis occurs in the oceans, a remarkable statistic given that oceanic biomass accounts for only about 1% of the planet's total. This substantial contribution to global photosynthesis is primarily driven by marine phytoplankton, microscopic organisms that perform photosynthesis similarly to terrestrial plants. [^1]
How Scientists Know This
Satellite Remote Sensing
Satellites equipped with sophisticated sensors measure chlorophyll concentrations in the oceans. Chlorophyll, a pigment present in phytoplankton, is vital for photosynthesis. By analyzing chlorophyll levels, scientists estimate the level of photosynthetic activity in the oceans. Notable satellite instruments like NASA's SeaWiFS (Sea-viewing Wide Field-of-view Sensor) and MODIS (Moderate Resolution Imaging Spectroradiometer) on the Aqua satellite play crucial roles in monitoring ocean productivity. [^2]
Oceanographic Surveys and Sampling
Research vessels and autonomous devices such as Argo floats collect water samples from various ocean depths and locations. These samples are analyzed for chlorophyll concentrations, nutrient levels, and other indicators of phytoplankton activity. These field surveys are essential for calibrating and validating satellite data, providing more detailed information on photosynthetic rates and biomass distribution in diverse marine environments. [^3]
Ecological and Biogeochemical Models
In addition to direct measurements, scientists use complex ecological and biogeochemical models to estimate global photosynthesis rates. These models integrate satellite data, oceanographic survey data, and findings from laboratory studies. They consider numerous factors influencing photosynthesis, such as light availability, nutrient concentrations, and water temperature. These models enable researchers to simulate different scenarios and better understand how changes in environmental conditions may affect oceanic photosynthesis. [^4]
Sources
[^1] National Ocean Service. (n.d.). How much oxygen comes from the ocean? NOAA. https://oceanservice.noaa.gov/facts/ocean-oxygen.html (Accessed on 08/17/2024)
[^2] NASA Earth Observatory. (n.d.). The ocean’s carbon balance. NASA. https://earthobservatory.nasa.gov/features/OceanCarbon (Accessed on 08/17/2024)
[^3] Roemmich, D., Johnson, G. C., Riser, S., Davis, R., Gilson, J., Owens, W. B., Garzoli, S. L., Schmid, C., & Ignaszewski, M. (2009, June). The Argo program: Observing the global ocean with profiling floats. Oceanography. https://doi.org/10.5670/oceanog.2009.36
[^4] Fennel, K., Mattern, J., Doney, S., Bopp, L., Moore, A., Yu, L., & Wang, B. (2022, September). Ocean biogeochemical modelling. Nature Reviews Earth & Environment. https://doi.org/10.1038/s43586-022-00154-2