Thursday, 10 November 2016

Huxley's Bathybius – an early example of an organic aggregate

In a 1983 paper, the oceanographer Tony Rice offers an explanation for the appearance of Bathybius haeckelii, thought to have been a living organism by T.H.Huxley [1]. Rice writes [2]:

In the 100 years or so since Huxley's Bathybius was relegated to the status of an interesting but embarrassing error, knowledge of deep-sea biology has increased enormously, for many thousands of samples both from mid-water and from the deep-sea floor have been collected and examined. Consequently, although the deep ocean is still the least well-understood environment on earth because of its relative inaccessibility, some basic facts about its biological processes are now well-established...
.. With the exception of the minor local input from the activities of chemo-autotrophic bacteria, the food supply on which all deep sea animals are ultimately dependent originates in the near surface layers. In temperate waters, at least, the surface productivity is very seasonal, being highest in spring and summer when the phytoplankton is growing rapidly, and very low during the winter months. Although some of this material reaches the sea floor in the form of large, fast-sinking carcasses of fishes and whales, the main supply probably arrives as small particles, including the bodies of small plants and animals and faecal pellets, which may take many weeks to sink through the water column.

We now know that the sinking material also contains large numbers of flocs and other aggregates bound by the exudates of both bacteria and algae [3]. It is these that give the appearance of fluff that can be found over the ocean floor and which are difficult to collect in dredges, but which are clearly visible in sediment traps [2].

All this is a bit technical.

In the simplest terms, what Huxley observed was a large floc that contained components from near-surface organisms; the conclusion of contemporary scientists being that it was a precipitate of calcium sulphate, caused by preservation of a sample of sea bed in alcohol. This put an end to questions about the organic matter that was also present and the our seeming need to focus on organisms, rather than on total organic matter, was also a problem. We continue this focus, rather than taking the whole package of living and dead organic matter into account.

Let me give an example. What do you see when you look at this image from NOAA [4]?

Most will see an interesting creature – a whiplash squid – and wonder about its biology and mode of life. What about all the white dots in the rest of the picture, illuminated like the particles visible in the beam of a cinema projector? Don't  these raise questions?

While we know more about these particles and aggregates than we did when Tony Rice wrote his article, we still tend to ignore them in favour of our interest in organisms. It is true that the organic matter present in oceans, and other water bodies, is largely dependent on organisms for its production [3], but we must always consider the whole organic, and inorganic, package when trying to understand the biology of water bodies. What a pity that way of thinking didn't start with Huxley's observations on Bathybius.  

[2] A.L.Rice (1983) Thomas Henry Huxley and the strange case of Bathybius haeckelii; a possible alternative explanation. Archives of Natural History 11:169-180.

[3] Roger S. Wotton (2005) The essential role of exopolymers (EPS) in aquatic systems. Oceanography and Marine Biology: An Annual Review 42:57-94.

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