Background
Euphausiids are small pelagic shrimplike crustaceans of the order Euphausiacea that are said by the authors to constitute "an important component of the pelagic realm," where they "graze directly on phytoplankton and provide a food source for a range of predators including birds, seals, baleen whales and many commercially important fish species," citing Verity et al. (2002).

What was done
Using a generalized additive model, Letessier et al. assessed the influence of a suite of physical, chemical and biological variables on euphausiid species abundance. More specifically, they used environmental changes based on the IPCC A1B climate scenario to make predictions of future species abundance changes in the Pacific and Atlantic Oceans, which they sub-divided into cells having east-to-west lengths of 300 km and north-to-south lengths of 200 km.

What was learned
The three UK researchers report that "the main drivers of species abundance, in order of decreasing importance, were sea surface temperature (SST, explaining 29.53% of species variability), salinity (20.29%), longitude (-15.01%, species abundance decreased from West to East), distance to coast (10.99%) and dissolved silicate concentration (9.03%)."

What it means
In a future world, such as that envisioned by the IPCC in terms of temperature, Letessier et al. say their results suggest that "the present broad patterns apparent in species abundance (low in high latitudes, high in intermediate latitudes and intermediate in the tropics) will become less pronounced in a warming ocean," and that, eventually, "species abundance will be enhanced within intermediate-to-high latitudes (30°N to 60°N and 30°S to 60°S) and diminished in the tropics (20°N to 20°S)," which changes are "consistent with changes already observed to be occurring in terrestrial systems in Europe and America," citing Rosenzweig et al. (2008), as well as with "already-observed changes in zooplankton assemblages in the North Atlantic (i.e., communities shifting north)," as reported by Beaugrand et al. (2002), Beaugrand and Ibanez (2004) and Richardson and Schoeman (2004). And considered in their entirety, such shifts in euphausiid species abundance may well be viewed as positive developments, especially in light of the three scientists' finding that both the Atlantic and Pacific Oceans "will on average see an increase in species abundance per cell."

References
Beaugrand, G. and Ibanez, F. 2004. Monitoring marine plankton ecosystems. II: long-term changes in North Sea calanoid copepods in relation to hydro-climatic variability. Marine Ecology Progress Series 284: 35-47.

Beaugrand, G., Reid, P.C., Ibanex, F., Lindley, J.A. and Edwards, M. 2002. Reorganization of North Atlantic marine copepod biodiversity and climate. Science 296: 1692-1694.

Richardson, A.J. and Schoeman, D.S. 2004. Climate impact on plankton ecosystems in the Northeast Atlantic. Science 305: 1609-1612.

Rosenzweig, C., Karoly, D., Vicarelli, M., Neofotis, P., Wu, Q., Casassa, G., Menzel, A., Root, T.L., Estrella, N., Seguin, B., Tryjanowski, P., Liu, C., Rawlins, S. and Imeson, A. 2008. Attributing physical and biological impacts to anthropogenic climate change. Nature 453: 353-357.

Verity, P.G., Smetacek, V. and Smayda, T.J. 2002. Status, trends and the future of the marine pelagic ecosystem. Environmental Conservation 29: 207-237.