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  • 16-02-2008 02:11PM
    #1
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 94,362 Mod ✭✭✭✭


    As to why no sharks are in deep water, Dr. Priede had a simple explanation: they were outcompeted by bony fishes. Sharks had been around for hundreds of millions of years when the deep oceans became oxygenated about 70 million years ago.

    "There was a race to colonize the deep sea," he said, one that was quickly won by the bony fishes because, among other advantages, they developed very efficient ways to use oxygen and maintain buoyancy. "These bony fishes down there are so good at what they do," he said, "they just took over."

    wow - macroscopic life on the the ocean floors for only the last 70m years, I'll need to look this up
    wonder if the deoxygenation was primordial or ocean current related ??
    nothing to do with the KT event as that was more recend ?


Comments

  • #2
    Canis_major
    Registered Users, Registered Users 2 Posts: 32 ✭Canis_major


    Hmm i think that the deep ocean was host to an oxic environment quite a while before that, macroscopic multicellular life initially evolving in deep marine ecosystems is a popular interpretation of some earliest animal body fossils.
    have a look at

    http://www.sciencemag.org/cgi/content/abstract/1135013v1
    I'm pretty sure the deep oceans became oxygenated in and around cambrian times

    I do think however its a very interesting point you've made regarding the role of changing sea chemistry and evolution. In recent palaeo talks i've attended the flip between a microbial world and the dominance of animals was facilitated by oxygen permeating into the seas/atmosphere and allowing complex bodyplans to exist. The chemical composition changed significantly over time as well but i can remember the exact details off the top of me head

    As for the sharks, they'd still have a fairly high 02 need to be there in the 1st place.
    Check out Vampyroteuthis infernalis or vampire squid, they live in the oxygen minimum zone of the ocean (600-900m) where pretty much nothing else large lives
    .


  • #3
    Capt'n Midnight
    Moderators, Recreation & Hobbies Moderators, Science, Health & Environment Moderators, Technology & Internet Moderators Posts: 94,362 Mod ✭✭✭✭Capt'n Midnight


    Canis_major wrote:
    Hmm i think that the deep ocean was host to an oxic environment quite a while before that, macroscopic multicellular life initially evolving in deep marine ecosystems is a popular interpretation of some earliest animal body fossils.
    well for most earth's history the sea was brown from all the dissolved iron, IIRC about 1.5-2 billion years ago the cyanobacteria released O2 and the iorn percipitated and formed most of todays iorn ore deposits.

    just found it strange that the deep oceans have only been oxygenated for 3.5% of the time since the there was enought oxygen to drop the iron out of solution


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