You Ask, I Answer

A great response from the readers to last week’s Pose a Question post. Here are some answers.

  • Chris asks, “There have been several terrestrial mass extinction events. Did those same events cause similar results in the deep sea, or does the deep sea has its own such events.” Unfortunately, little explicit research for a majority of the deep-sea fauna addressing this question has ever been conducted, except possible for forams and ostracods.  Obviously this reflects the lack of fossil record for these other groups.  Because a majority of deep-sea systems are reliant on ocean surface production for food, one can envisage any disruption of phytoplankton production during an extinction event being detrimental to deep-sea fauna.  This is one of reasons why hydrothermal vent communities, not dependent on this process, are thought to be buffered against these events.  In addition from McClain et al. (2006)…

    The current understanding of the deep sea is that much of its fauna died out in the mid-Cenozoic Era and was replaced by shallow-water immigrants (Gage, 2004). During the period of 30-40 Ma, bottom temperatures throughout much of the deep sea decreased by up to 10 C concurrent with an ocean-wide disoxyia/anoxia event. The mass extinction was followed by a colonization of species from coastal sources. Hypothesized shallow-water origins include polar regions; the Mediterranean Ocean, other regions where the water column is isothermal; or multiple shallow-water areas (Wilson, 1999; Gage, 2004). [For example] Gastropoda, is proposed to have only recently (c. 30 Ma) immigrated to the deep sea from multiple coastal centres (Clarke, 1962). Although…some deep-sea taxa appear to be ancient with high levels of in situ speciation (Wilson, 1999), the predominant direction of migration for many organisms is into deeper water (Jacobs & Lindberg, 1998)

  • Ellie queries, “Is “tell me a bunch more about Nudibranchs” too general?” Yes, but I will say Nudibranchs are commonly found in the deep sea, often in deep coral meadowsOnly a single species is described from a hydrothermal vent.

  • Ellie also proposes, “And if it is, how about info on how deep deep is. What’s the deepest point and have we touched down there yet? What’s the deepest a human has gone. An unmanned submersible? And a compare those to scale with layers of the earth and the atmosphere.” For the purpose of DSN, I define the deep sea as those environments below 200m.  The deepest part of the ocean, and deepest part in the earth’s crust, is Marianas Trench at 10,911m (6.78 miles).  In 1960, Picard and Walsh reached this spot in the Trieste.  JAMSTECS’s Kaiko, an unmanned ROV, repeatedly has visited the deepest part of the trench.  Surprisingly, because of the equatorial bulge you are closer to the earth’s core when you in the Artic abyssal plain (~4,500m; 3,947 miles from the core) than in the Marianas Trench (3,955,9 miles).

  • Ellie also requests, “Are deep seeps located in the deep sea? I don’t know at what depths they’re usually found, but if they are I have plenty more questions about them.”  Methane seeps are also found in shallow water, but are a common feature of deep-sea systems.

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 (http://deepseanews.com/), 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 “You Ask, I Answer”

  1. Is it too late to post more questions? I only saw a little bit about seeps on a Discovery program and upon further investigation what I meant to ask about were brine pools. The idea of lakes in the ocean is fascinating. The program said that if animals touch them they fall in and die and that we have a hard time penetrating them. Do we know if anything lives in the pools. Where would you recommend I go for some lay person reading and/or viewing? Thanks!

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