P. Licandro, D. V. P. Conway, M. N. Daly Yahia, M. L. Fernandez de Puelles, S. Gasparini, J. H. Hecq, P. Tranter, R. R. Kirby. A blooming jellyfish in the northeast Atlantic and Mediterranean. Biology Letters, 2010; 6 (5): 688 DOI: 10.1098/rsbl.2010.0150
This paper doesn’t quite fall under the evolution/development/paleontology tent, but as a jellyfish researcher, I can’t resist mentioning some of the more interesting (and sometimes disturbing) work coming out on these animals. It was a mere 600 million years ago when jellyfish were one of the only creatures swimming in the oceans, and some ecologists have worried if that is going to happen again. With the collapse of multiple fish stocks, as well as a warming and increasingly oxygen-poor ocean, the environment seems right for jellyfish to thrive. There have been a number of reports of large jellyfish blooms over the last decade, occasionally causing serious damage to farm-fishing industries and tourism (Purcell 2007, Doyle 2008). However, it is also known that jellyfish blooms are cyclical, so it is sometimes difficult to determine if large swarms of jellyfish are unusual or a natural phenomenon.
In a new recent paper published in Biology Letters, Licandro et al. try to get a hand on the problem using data from the Continuous Plankton Recorder. This instrument has been attached to ships and towed through the oceans since 1931, providing rough data on the abundance of plankton in the ocean. By looking for jellyfish tissue and nematocysts (stinging cells), they were able to see how the frequency of jellyfish has changed since 1958. Below is a chart showing jellyfish numbers (higher frequency = red) throughout the months (on the y axis) of each year (on the x axis). For example, in 1970 there was no evidence of jellyfish until about April, and they disappeared after July without ever reaching a high concentration:
This graph suggests that the jellyfish now persist throughout the year in the Northeast Atlantic, and they exist in higher numbers than usual. Licandro et al. think the cause might have to do with the warming of the oceans over the last decade. To the left is a map showing the change in jellyfish numbers, to the right is the change in the sea surface temperature (differences were measured as the mean differences between 1958–2001 and 2002–2007):
While the methods for using the Continuous Plankton Recorder haven’t changed since 1948, the methods use to analyze the data have. In the past, it would have been difficult, if not impossible to tell what types of jellyfish these nematocytes came from. With DNA testing Licandro et al. determined that the prime culprit is Pelagia noctiluca:
This is the same species that formed a 10-mile bloom of the coast of Ireland in 2007 and destroyed a 100,000 fish salmon farm! Unlike the jellyfish I study (the moon jelly Aurelia aurita), these animals can give humans a nasty sting, so an increase of these in the oceans isn’t something to look forward to.
This paper offers quantitative support to an idea that many scientists have grown concerned about, that changing ocean conditions are positively affecting the abundance of jellyfish to the detriment of other swimming sea creatures. It’s a worrisome idea if you care about seafood or biodiversity, but it’s not so bad if you study jellyfish…
References
Licandro, P., Conway, D., Daly Yahia, M., Fernandez de Puelles, M., Gasparini, S., Hecq, J., Tranter, P., & Kirby, R. (2010). A blooming jellyfish in the northeast Atlantic and Mediterranean Biology Letters, 6 (5), 688-691 DOI: 10.1098/rsbl.2010.0150
Purcell, J., Uye, S., & Lo, W. (2007). Anthropogenic causes of jellyfish blooms and their direct consequences for humans: a review Marine Ecology Progress Series, 350, 153-174 DOI: 10.3354/meps07093
