Ecology

Pulsing Populations of Jellies

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Science  18 Jan 2013:
Vol. 339, Issue 6117, pp. 251
DOI: 10.1126/science.339.6117.251-a
CREDIT: THINKSTOCK

One strand of evidence for the deterioration of Earth's oceans is the perception that the seas are becoming overwhelmed by jellyfish. In fact, there has been little global analysis of jellyfish populations and the jellyfish ocean perception as made on the basis of a few scattered reports. Condon et al. undertook a meta-analysis using linear and logistic mixed models and effect-size analysis on data ranging from 1790 to 2011. There are many limitations to the available data: The older records are sparse, and the majority of more recent data are from the North Atlantic and Mediterranean. Although strong 20-year oscillations were revealed by the analysis, in fact only a weak upward trend has been observed since 1970. The authors acknowledge that this could be a false negative, but unless more data are collected from more sites, the jury is still out on whether jellyfish will take over the increasingly anthropogenically affected oceans.

Proc. Natl. Acad. Sci. U.S.A. 10.1073/pnas.1210920110 (2012).

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