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Taboada, FG, Barton AD, Stock CA, Dunne J, John JG.  2019.  Seasonal to interannual predictability of oceanic net primary production inferred from satellite observations. Progress in Oceanography. 170:28-39.   10.1016/j.pocean.2018.10.010   AbstractWebsite

Seasonal to interannual predictions of ecosystem dynamics have the potential to improve the management of living marine resources. Prediction of oceanic net primary production (NPP), the foundation of marine food webs and the biological carbon pump, is particularly promising, with recent analysis suggesting that ecosystem feedback processes may lead to higher predictability of NPP at interannual scales than for physical variables like sea surface temperature (SST). Here, we assessed the potential predictability of oceanic NPP and SST across seasonal to interannual lead times using reduced dimension, linear dynamical spatio-temporal models (rDSTM). This approach combines empirical orthogonal function (EOF) analysis with vector autoregressive (VAR) modeling to simplify the analysis of spatio-temporal data. The rDSTMs were fitted to monthly NPP and SST anomalies derived from 20 years of remote sensing data (1997-2017), considering two alternative algorithms commonly used to estimate NPP (VGPM and Eppley-VGPM) and optimally analyzed SST fields (AVHRR OISST). The local decay of anomalies provided high predictability up to three months, and subsequent interactions with remote forcing significantly extended predictability beyond the initial anomaly decay. Indeed, interactions among spatial modes associated with the propagation of major climate modes, particularly the El Nifio-Southern Oscillation (ENSO), extended the predictability horizon above one year in some regions. Patterns of enhanced NPP predictability matched the location of oligotrophic gyres and transition regions between ocean biomes, where fluctuations in biome boundaries generate large biogeochemical perturbations that leave lasting imprints on NPP. In these areas, the predictability horizon for NPP was longer than for SST, although SST was more predictable over large areas of the equatorial and northeast Pacific. Our results support the potential for extending seasonal to interannual physical climate predictions to predict ocean productivity.

Van Oostende, N, Dussin R, Stock CA, Barton AD, Curchitser E, Dunne JP, Ward BB.  2018.  Simulating the ocean's chlorophyll dynamic range from coastal upwelling to oligotrophy. Progress in Oceanography. 168:232-247.   10.1016/j.pocean.2018.10.009   AbstractWebsite

The measured concentration of chlorophyll a in the surface ocean spans four orders of magnitude, from similar to 0.01 mg m(-3) in the oligotrophic gyres to > 10 mg m(-3) in coastal zones. Productive regions encompass only a small fraction of the global ocean area yet they contribute disproportionately to marine resources and biogeo-chemical processes, such as fish catch and coastal hypoxia. These regions and/or the full observed range of chlorophyll concentration, however, are often poorly represented in global earth system models (ESMs) used to project climate change impacts on marine ecosystems. Furthermore, recent high resolution (similar to 10 km) global earth system simulations suggest that this shortfall is not solely due to coarse resolution (similar to 100 km) of most global ESMs. By integrating a global biogeochemical model that includes two phytoplankton size classes (typical of many ESMs) into a regional simulation of the California Current System (CCS) we test the hypothesis that a combination of higher spatial resolution and enhanced resolution of phytoplankton size classes and grazer linkages may enable global ESMs to better capture the full range of observed chlorophyll. The CCS is notable for encompassing both oligotrophic (< 0.1 mg m(-3)) and productive (> 10 mg m(-3)) endpoints of the global chlorophyll distribution. As was the case for global high-resolution simulations, the regional high-resolution implementation with two size classes fails to capture the productive endpoint. The addition of a third phytoplankton size class representing a chain-forming coastal diatom enables such models to capture the full range of chlorophyll concentration along a nutrient supply gradient, from highly productive coastal upwelling systems to oligotrophic gyres. Weaker 'top-down' control on coastal diatoms results in stronger trophic decoupling and increased phytoplankton biomass, following the introduction of new nutrients to the photic zone. The enhanced representation of near-shore chlorophyll maxima allows the model to better capture coastal hypoxia along the continental shelf of the North American west coast and may improve the representation of living marine resources.

McGinty, N, Barton AD, Record NR, Finkel ZV, Irwin AJ.  2018.  Traits structure copepod niches in the North Atlantic and Southern Ocean. Marine Ecology Progress Series. 601:109-126.   10.3354/meps12660   AbstractWebsite

Realised niches describe the environmental and biotic conditions that a species occupies. Among marine zooplankton, species traits, including body size, dietary mode (herbivore, omnivore, or carnivore), and diapause strategy are expected to influence the realised niche of a species. To date, realised niches are known for only a small number of copepod species. Here we quantify the realised niches of 88 copepod species measured by the Continuous Plankton Recorder (CPR) in the North Atlantic and Southern Ocean using Maximum Entropy (MaxEnt) modelling. We estimate the univariate mean niche, niche breadth of copepods for several important environmental variables, and assess the relative effects of several key zooplankton traits on the mean niche. Sea surface temperature (SST) contributed the most information to the description of niches on average across all species, with the rank importance of the remaining variables varying between regions. In the North Atlantic SST, depth, salinity and chlorophyll niches separated omnivores and herbivores from carnivores while in the Southern Ocean niche differences across dietary modes were found for chlorophyll and wind stress only. Diapausing copepods were found to occur in colder temperatures compared with non-diapausing taxa, likely because of their capacity for accumulating lipids. A strong negative body size-niche breadth relationship was found only for diapausing copepods, suggesting that larger multi-year generation species are more reliant on a specific temperature range to successfully reach diapause. Our analysis demonstrates strong connections between copepod traits and their realised niches in natural populations.