More Types of Bacteria In Tropical Waters

ResearchBlogging.orgBeware when you go on tropical holiday. Species richness of bacteria is higher in those waters. For many organisms on land (birds, mammals, snails, plants, insects, and more) diversity increases as one progresses toward the equator. For many marine groups, snails for example, the same patterns applies. This is referred to often as the LSDG or the latitudinal species diversity gradient.

What drives this pattern? The hypotheses are numerous but typically the two favorites are primary productivity and temperature. On one hand a bigger pie allows for more slices. On the other hand temperature speeds up reactions scaling up to ecological interactions and evolutionary processes that may promote higher diversity. A recent study lead by Fuhrman documents the LSDG for the first time in marine microbes. Diversity was higher in tropical waters in the Pacific and Atlantic. One might have predicted that the LSDG would be absent in bacteria with extremely high abundances and great dispersal abilities that would swamp genetic intertia for speciation.

Perhaps more interesting is that the patterns for bacteria are driven by temperature not productivity. Bacteria was equally rich in low and high productivity waters but equally warm. Cold waters despite productivity level were equally low.

Admittedly I am torn. The last author of the study is my former post doctoral advisor. A study demonstrating that temperature does not drive LSDG’s in some other groups, deep-sea mollusks and cructaceans, was published by my Ph.D. advisor. He did this by simply and elegantly showing that LSDG’s exist in the deep sea where temperature varies just a few degrees C (the deep is equally cold and dark despite location).

What to do? What to do? These studies together probably indicate that LSDG’s are likely driven by factors that are taxon specific.

Fuhrman, J.A., Steele, J.A., Hewson, I., Schwalbach, M.S., Brown, M.V., Green, J.L., Brown, J.H. (2008). A latitudinal diversity gradient in planktonic marine bacteria. Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0803070105

Rex, M.A., Stuart, C.T., Hessler, R.R., Allen, J.A., Sanders, H.L., Wilson, G.D. (1993). Global-scale latitudinal patterns of species diversity in the deep-sea benthos. Nature, 365(6447), 636-639. DOI: 10.1038/365636a0

Dr. M (1801 Posts)

Craig McClain is the Executive Director of the Lousiana University Marine Consortium. He has conducted deep-sea research for 20 years and published over 50 papers in the area. He has participated in and led dozens of oceanographic expeditions taken him to the Antarctic and the most remote regions of the Pacific and Atlantic. Craig’s research focuses on how energy drives the biology of marine invertebrates from individuals to ecosystems, specifically, seeking to uncover how organisms are adapted to different levels of carbon availability, i.e. food, and how this determines the kinds and number of species in different parts of the oceans. Additionally, Craig is obsessed with the size of things. Sometimes this translated into actually scientific research. Craig’s research has been featured on National Public Radio, Discovery Channel, Fox News, National Geographic and ABC News. In addition to his scientific research, Craig also advocates the need for scientists to connect with the public and is the founder and chief editor of the acclaimed Deep-Sea News (, a popular ocean-themed blog that has won numerous awards. His writing has been featured in Cosmos, Science Illustrated, American Scientist, Wired, Mental Floss, and the Open Lab: The Best Science Writing on the Web.

3 Replies to “More Types of Bacteria In Tropical Waters”

  1. So the long-winded question we should be asking ourself’s is “what is it that increases as you get nearer the equator and influences factors contributing towards evolution, but is not temperature or productivity of environment?”.

    How about UV radiation?

  2. How about temperature and and productivity? UV is unlikely to be a factor to organisms leaving on the deep-sea floor

  3. I think its the Coriolis Force man. Since the earth is spinning so fast it concentrates things in the center, which is near the equator. Its like when you swirl water with floaties in it. All the floaties concentrate in the middle. We’re like those floaties! It totally makes sense

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