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Primary Productivity in a Southern Chilean Fjord
Reference
Sepulveda, J., Pantoja, S., Hughen, K., Lange, C., Gonzalez, F., Munoz, P., Rebolledo, L., Castro, R., Contreras, S., Avila, A., Rossel, P., Lorca, G., Salamanca, M. And Silva, N.  2005.  Fluctuations in export productivity over the last century from sediments of a southern Chilean fjord (44S).  Estuarine, Coastal and Shelf Science 65: 587-600.

What was done
The authors present "the first reconstruction of changes in surface primary production during the last century from the Puyuhuapi fjord in southern Chile, using a variety of parameters (diatoms, biogenic silica, total organic carbon, chlorins, and proteins) as productivity proxies."  They note that the fjord is located in "a still-pristine area," which they say is "suitable to study changes in past export production originating from changes in both the paleo-Patagonian ice caps and the globally important Southern Ocean."

What was learned
Sepulveda et al. report that the productivity of the Puyuhuapi fjord "was characterized by a constant increase from the late 19th century to the early 1980s, then decreased until the late 1990s, and then rose again to present-day values."  For the first of these periods (1890-1980), they additionally report that "all proxies were highly correlated (r > 0.8, p < 0.05)," and that "all proxies reveal an increase in accumulation rates."  From 1980 to the present, however, the pattern differed among the various proxies; and the researchers say that "considering that the top 5 cm of the sediment column (~10 years) are diagenetically active, and that bioturbation by benthic organisms may have modified and mixed the sedimentary signal, paleo-interpretation of the period 1980-2001 must be taken with caution."  Consequently, there is substantial solid evidence that, for the first 90 years of the 111-year record, surface primary production in the Puyuhuapi fjord rose dramatically, while with lesser confidence it appears to have leveled out over the past two decades.

What it means
In spite of climate-alarmist contentions that the "unprecedented" increases in mean global air temperature and CO2 concentration experienced since the inception of the Industrial Revolution have been bad for the biosphere, Sepulveda et al. present yet another case of an ecosystem apparently loving the new conditions.  For more such examples, see Productivity in our Subject Index.

Reviewed 25 January 2006