After handing in my dissertation about the effects of hypoxia on jellyfish growth and behaviour, I was a little sad to say goodbye to my gelatinous friends. However, after doing some research I realized that there is no need to say goodbye – luckily microbes are everywhere and associated with everything, and so jellyfish are no exception. Bacterial communities have been first associated with ctenophores in Florida. Different ctenophore genera were found to contain a unique micro-biota (Daniels and Breitbart 2012), with Alphaproteobacteria, Gammaproteobacteria and Becteroidetes most abundant. There have also been several associations between scyphozoans and microbes. Biofilms with certain bacteria, induce planula larvae settlement in scyphozoan (Vibrio sp. found to induce metamorphosis of Cassiopea sp.). Jellyfish biomass is also highly bio-available to jellyfish associated and or free living heterotrophic bacteria, and bacteria thrive in the DOC released by live animals. Jellyfish could be therefore a suitable substrate for specific bacteria community.
A recent study (Hao et al. 2014) identified how planktonic bacterial communities respond to the dissolved organic matter released by two species of live jellyfish. This was done by a combination of ARISA fingerprinting and CARD-FISH analysis and the impacts on bacterial abundance were investigated by flow cytometry. The DOM released by live jellyfish stimulated bacterial communities and induced large changes in bacterial community composition. Gammaproteobacteria dominating the community conducted with Cyanea lamarckii, Bacteroidetes, decreased at the beginning and recovered at the end of the experiment. Gammaproteobacteria and Bacteroidetes dominating the community within Chrysaora hysoscella, were present in equal amounts throughout the experiment. Differences in bacterial community composition and succession indicate, that the DOM released by different jellyfish genera might consist of a variety of compounds, which are species specific. However there is need for chemical characterization of the DOM pools to establish a linkage between certain taxa and specific carbon compounds.
Although there is room for a lot more work, I think this is a great study in a very important topic! Here it was clearly shown that bacterioplankton communities are not only influenced by dead jellyfish biomass but also strongly impacted by DOM released from metabolic processes of live animals. Findings suggest that jellyfish derived organic matter may function as a newly discovered trophic pathway for organic matter from the benthic environment to pelagic food chains in marine ecosystems. Fundamental transformations in the biogeochemical functioning associated with jellyfish blooms, accompanying a channel of Carbon towards bacterial CO2 production and away from higher trophic levels can potentially alter the food web dramatically. There is concern of anthropogenic-induced increase of jellyfish blooms; this topic should therefore be given way more attention in the future.
Hao WJ, Wichels A, Fuchs B, Gerdts G (2014) Bacterial communities respond to the excretion of DOM relseased by live jellyfish. PhD Thesis, Universität Bremen.
Super interesting! Although the compounds in the DOM were possibly species specific, was the community exploiting them distinct from the kind of community which would presumably exploit the DOM released from other organisms such as Macroalgae?
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DeleteHi Tom, Not sure if I completely understand your question? They didn`t run any experiments with macro algae, however they did have a control treatment with no jellyfish in. I think it would be really interesting to compare the bacterial assemblages found associated with macro algae blooms and jellyfish blooms in nature. From a previous post I wrote at the start of the year I remember, that phytoplankton blooms can shift microbial communities from being dominated by Alphaproteobacteria to being dominated by Flavobacteria and Gammaproteobacteria, so yes it seems really similar to what is happening with jellyfish. However I think there needs to be more work done on the composition of the bacterial community associated with jellyfish DOM. There is a lot more work done on bacterial community changes associated with algae blooms, it is crazy that the shifts associated with live jellyfish hasn`t been looked into as much. In the case of milder winters it is more likely that jellyfish can survive the winter, gain even bigger sizes and therefore release more DOM the next year... As I said they will take over the world
DeleteHey Tabea- great you managed to get some jellyfish involved! I was wondering what type of DOM- is this like feacel matter (may seem a dim question!)? As you said, I agree it would be important to find out what exactly is the difference between the DOM pools from each species, as I guess you could then go on to investigate this in every marine organism? Were the bacterial communities actually in contact with the jellyfish i.e. on the surface or were they in the water column? Was this a lab based experiment? So what organisms actually feed on the bacteria then- thinking in the trophic food web context??? Thanks :)
ReplyDeleteHi Elyssa. Yes it is metabolic waste of the jellyfish. Yes it probably would be interesting to the the differences between the microbial communities associated with the DOM for every marine organism. Can you think of any other organism that could have such a large scale impact like jellyfish or algae blooms?
DeleteIn a different part of this PhD thesis Hao et al. are actually investigating in the bacterial communities ON the jellyfish. These differ between different parts of the Jellyfish and also between the life stages - loads of interesting stuff! In the bit I was talking about it was literally just about the bacterial communities found on the DOM that has accumulated at the bottom of the aquarium. Yes it was a lab based experiment, however I think it would be really interesting to try it in nature. Not sure if thats possible though! :)
To answer your last question: Jelly-DOM enhances bacterial metabolism (rather then growth) and there has been therefore an overall decline found in the efficiency of C transfer through the microbial loop during jellyfish blooms! In jellyfish-dominated food webs jellyfish repackage and reroute planktonic organic matter (coming from what they heave fed on) into a respiratory sink rather than being potentially reincorporated into and transferred up to the food web. If you want to know a bit more about it Condon et al. 2011 did a great study! Hope that helps! Let me know if you have any questions
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