MEPS 620:33-46 (2019)  -  DOI: https://doi.org/10.3354/meps12960

ABSTRACT: Global ocean primary production (PP) is a function of both light and nutrient availability. The vertical distribution of nutrients in the euphotic zone differs in both time and space. As a result, the vertical distribution of PP varies as well. Differences in the vertical distribution of PP have not, however, been systematically studied. Here, we focus on the open ocean and use nutricline depth, D_NO3 (defined as the depth where [NO₃^-] = 1 µmol kg^-1), as a proxy for nutrient availability in the euphotic zone. Using our own and archived (WOD, HOT, BATS, CARIACO) data, we show universal relationships between D_NO3 and (1) depth of the deep chlorophyll maximum (DCM), (2) total water column PP and (3) vertical distribution of PP. When D_NO3 is located between ~20 and 90 m, the DCM and D_NO3 are juxtaposed. However, the DCM is located above nutriclines found at > ~90 m. The observed relationships between DCM and D_NO3 depths can be explained with a simple model including light and nutrient limitation. The global PP estimates indicate that ~25% of ocean PP occurs in the upper 10 m. Estimating total global ocean PP from surface optical characteristics and the relationship between vertical PP distribution and D_NO3 indicates that oligotrophic regions of the ocean may be more productive than usually assumed. The relationship shown here between water column PP and D_NO3 suggests that considering stratification characteristics in a future ocean is critical for predicting climate change effects on global PP.

KEY WORDS: Global primary production · Vertical distribution · Deep chlorophyll maximum · Nutricline

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Cite this article as: Richardson K, Bendtsen J (2019) Vertical distribution of phytoplankton and primary production in relation to nutricline depth in the open ocean. Mar Ecol Prog Ser 620:33-46. https://doi.org/10.3354/meps12960 Export citation Share:    Facebook - - linkedIn