The North Atlantic Spring Phytoplankton Bloom and Sverdrup's Critical Depth Hypothesis
D. A. Siegel,1*
S. C. Doney,2
J. A. Yoder3
More than 50 years ago, Harald Sverdrup developed a simple model
for the necessary conditions leading to the spring bloom of
phytoplankton. Although this model has been used extensively across a
variety of aquatic ecosystems, its application requires knowledge of
community compensation irradiance (IC), the
light level where photosynthetic and ecosystem community loss processes balance. However, reported IC values have varied
by an order of magnitude. Here, IC estimates are
determined using satellite and hydrographic data sets consistent with
the assumptions in Sverdrup's 1953 critical depth hypothesis.
Retrieved values of IC are approximately uniform
throughout much of the North Atlantic with a mean value of 1.3 mol
photons meter
2 day1. These community-based
IC determinations are roughly twice typical values found for phytoplankton alone indicating that phytoplankton account for approximately one-half of community ecosystem losses. This
work also suggests that important aspects of heterotrophic community
dynamics can be assessed using satellite observations.
1 Institute for Computational Earth System
Science and Department of Geography, University of California Santa
Barbara, Santa Barbara, CA 93106-3060, USA.
2 National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305, USA.
3 Graduate
School of Oceanography, University of Rhode Island, Narragansett, RI
02882-1197, USA.
*
To whom correspondence should be addressed. E-mail:
davey{at}icess.ucsb.edu
