National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2012

Spatial and seasonal variability of primary production on the eastern Bering Sea shelf

Lomas, M.W., S.B. Moran, J.R. Casey, D.W. Bell, M. Tiahlo, J. Whitefield, R.P. Kelly, J.T. Mathis, and E.D. Cokelet

Deep-Sea Res. II, 65–70, 126–140, doi: 10.1016/j.dsr2.2012.02.010 (2012)

Spatial and seasonal variability in net primary production (NPP) is reported for the Eastern Bering Sea shelf in spring and summer 2008 and 2009. Euphotic zone integrated NPP in the spring, estimated from simulated in situ 14C-incubations, varied ∼30-fold across the northern and southern regions of the Inner, Middle, and Outer domains of the shelf. During spring, rates were lowest and similar in the North and South region of the Inner domain, while the highest rates were in the Southern region of the Outer domain as a result of extensive ice-edge phytoplankton blooms. Generally, phytoplankton integrated chlorophyll (Chl-a) standing stocks were dominated (>50%) by large (>5 μm) cells. With the exception of the southern Middle domain, integrated rates of NPP were consistently lower in summer than spring, while there was no consistent pattern in changes in integrated Chl-a. Conversely, phytoplankton growth rates (μ) were lower in spring (0.22±0.09 d−1) than summer (0.42±0.17 d−1), consistent with a seasonal shift from a biomass-controlled production system to a growth-rate controlled production system. Associated with this shift in control was a decrease in the size distribution of chlorophyll from ∼60% of the Chl-a>5 μm in the spring to ∼30% of the Chl-a>5 μm in the summer. Despite the widespread distribution of stations, these observations highlight the variable nature of NPP in the Bering Sea, which makes the estimation of seasonal or annual rates in any domain or across the entire shelf difficult, if not impossible, on direct observations alone. A vertically generalized productivity model (VGPM) was used to assimilate the more extensive underway dataset from two cruises to improve the spatial distribution of calculated NPP included in the regional estimates of NPP. The VGPM output captured ∼83% of the variance in measured 14C production, accurately estimated observed NPP (Model II regression slope±stdev.; 0.92±0.06), and allowed for a better constrained estimation of shelf-wide productivity due to higher data density in each region/domain. These results, when combined with published data on shelf-wide productivity suggest that the ecosystem response to climate change (whether an increase or decrease in productivity) would have to exceed a factor of two from mean conditions before being detectable from a comparable survey effort.

Feature Publications | Outstanding Scientific Publications

Contact Sandra Bigley |