Primary Productivity

Marine primary production

Total chlorophyll (mg/m3) in the North Pacific, 1908 to 2008
Graph: marine primary production in the North Pacific. Click for graphic description (new window).
Note: trend (line) and average annual values (points) were estimated through statistical modeling. Dashed line represent parts of the trend based on limited data and hence with lower confidence.
Source: adapted from Boyce et al., 201016

Satellite measurements of ocean colour have shown variable decade-scale trends in marine primary production, including a short-term increase in primary production in the Arctic Ocean from 1998 to 2008.17, 18 A recent study16 extended the record by also using longer-term measurements of water transparency and chlorophyll concentrations. This study concluded that, over the past 110 years, primary production has declined in most of the world’s ocean regions.16 High-latitude regions, including the North Pacific, showed the greatest long-term declines. The global decline in the amount of phytoplankton is estimated at 1% per year, with a total decline of 40% since 1950. Shorterterm trends were related to climate oscillations, while the long-term declines were most strongly related to increasing sea-surface temperatures – which leads to less mixing of ocean waters, reducing the nutrient supply for phytoplankton. The exceptions are the Arctic and Antarctic oceans, where the causes of the observed long-term decreases in primary production are less clear, but may be related to increased wind intensity.16

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