Last summer I attended the Marine Invertebrate Zoology course at Friday Harbor Labs (FHL) on San Juan Island. I was lucky enough to meet Claudia Mills, “the grand duchess of jellyfish”, and a recent article published by KCTS 9 about Claudia got me thinking about one of my favorite topics- jelly blooms.
Claudia has been observing jelly populations off the docks of Friday Harbor Labs for the past 35 years. She has observed a decrease in the number of jellies, but is still finding the same diversity of jellies. This was surprising, given the increased press over the years about “alien” jellies “taking over the oceans” with their “slime” as jelly blooms apparently increase.
What is a jelly bloom?
A jelly bloom happens when a very large number of jellies appear in the same place. They often occur where two ocean currents collide. Jelly blooms usually last for a short period of time, but in some cases can last multiple years.
What causes a jelly bloom?
There have been many hypotheses for what can cause jelly blooms, such as overfishing, ocean warming, ocean acidification, pollution, algal blooms and recently “ocean sprawl” in the recent Frontiers in Ecology article. Research suggests that jellyfish will opportunistically fill the niche that is usually occupied by fish in a healthy ocean ecosystem when the ecosystem degrades due to pollution, acidification or other factors. Richardson et al. provides a good review of possible causes of jelly blooms in this article. Another possibility is “shifting baselines”. Because we don’t have historical data to compare today’s jelly populations with, it appears that jelly blooms are increasing.
Jelly Blooms in the Media
The media has often sensationalized jelly blooms by citing them as “invasions” and “attacks” like this BBC article, and even citing jelly blooms as evidence that “the meek are indeed inheriting the earth” in this OnEarth article (insulting!). On Claudia’s website she says that the summary of this OnEarth article “…states ‘Swarms of jellyfish are invading coasts around the world. It’s an epidemic, and it’s coming soon to a beach near you’ in spite of my cautions that this may not be strictly true.’ ” Claudia isn’t the only scientist who isn’t sure that jellyfish are on the rise- Claudia is a part of the research group Jellyfish Data Initiative (JEDI). JEDI published an article in BioScience in February 2012 after compiling 500,000 records of data to examine patterns in jelly blooms stating findings that suggest 20-year cycles in jelly populations, as opposed to increased jelly blooms worldwide.
It is true that jelly blooms can be problematic. Jellies can clog water intake pipes and fishing nets and cause costly damages. In order to definitively say that ocean degradation is the cause of jelly blooms and that jelly blooms are increasing worldwide, more research is needed. Not all jelly populations behave the same- some populations of jellies have declined such as Spirocodon and Polyorchis penicillatus due to habitat loss.
Q: What is a group of jellies called?
A: A smack!
I long for the day when I can say “Hey, I just saw a smack of jellies!”.
I would like to think that if the oceans were overtaken in the future by giant jellies in some crazy scifi movie way, that I would respect our jelly overlords. Maybe its karma for most people seeing invertebrates as meek, boring and primitive…
Listen to NPR story “Jellyfish Take Over an Over-Fished Area”
National Geographic Jelly Pictures