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Post by Joe Botting on Apr 24, 2015 11:51:53 GMT -5
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Post by ammocarbsteve on Apr 25, 2015 4:01:31 GMT -5
Joe.... Congratulations and a big pat on the back to yourself and your colleagues who worked on this....I can see how much has gone into putting this together and theres some fantastic fossils finds included...Well worth the wait and a good read thanks....
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Post by Joe Botting on Apr 25, 2015 7:55:31 GMT -5
Thank you Steve. It's actually been quite fascinating seeing how some of our colleagues cannot accept the possibility that arthropods were not the dominant group. We've come across assumptions that arthropods must somehow not have been preserved, which is why there is such an extensive discussion about it in the paper. The thing is, we simply don't know enough about Ordovician soft-bodied communities to be sure what was going on, but there was definitely a general shift towards sessile suspension-feeders during the GOBE. It's all quite intriguing, but we're really interested to see what the academic reaction is going to be like...
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Post by ammocarbsteve on Apr 25, 2015 10:45:41 GMT -5
Joe.... As your probably aware there could be many reasons or external environmental factors and differences that could result in some fluctuations in the dominant species within the same layers of a fossil record...You will have to inform us of any feedback you guys get from this....
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Post by Joe Botting on Apr 25, 2015 11:23:06 GMT -5
Joe.... As your probably aware there could be many reasons or external environmental factors That is of course true, Steve, but we're not dealing with a single bed - it's a couple of hundred metres of section with roughly the same ecological balance. When you modify the raw data to take into account things like differential preservation in low sedimentation rates then the entire deposit can be understood as slight variations of essentially the same community. What we're really interested in is whether there were any systematic shifts away from arthropods and towards sponges in the wider global ecosystem at this time. So far, virtually all the exceptionally-preserved Ordovician faunas in Wales are sponge-dominated, which suggests that there may have been a regional shift in that direction; the question that remains unresolved is whether it was more widespread. The only other exceptionally-preserved Ordovician communities were either shallow-water (where spicules tend to dissolve), dysaerobic (Beecher's and Soom), or with strange ecology (as we're now discovering for the Fezouata). In other words, we need more Lagerstatten... and differences that could result in some fluctuations in the dominant species within the same layers of a fossil record...You will have to inform us of any feedback you guys get from this.... |
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Post by ammocarbsteve on Apr 29, 2015 13:44:54 GMT -5
Joe.... I think what I was getting at is are there any significant environmental factors that could allow sponges to flourish and at the same time arthropods to struggle.... Looking at modern sponge culture certain factors have to be right for optimum sponge growth, salinity of the water, PH of the water, dissolved oxygen levels and water column temperature and also water clarity and flow of water bringing food in the form of bacteria or micro algae all play a part... I suppose were describing ideal external factors for any sea dwelling creature to flourish so maybe not that easy to tie it down... Its an interesting question for sure....
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Post by Joe Botting on Apr 30, 2015 6:05:23 GMT -5
Joe.... I think what I was getting at is are there any significant environmental factors that could allow sponges to flourish and at the same time arthropods to struggle.... Looking at modern sponge culture certain factors have to be right for optimum sponge growth, salinity of the water, PH of the water, dissolved oxygen levels and water column temperature and also water clarity and flow of water bringing food in the form of bacteria or micro algae all play a part... I suppose were describing ideal external factors for any sea dwelling creature to flourish so maybe not that easy to tie it down... Its an interesting question for sure.... Gotcha. Yes, the precise conditions that favour one group over another are sometimes very subtle; sometimes we don't really understand them in the modern world, even. One of the main factors, though, is the interaction between substrate, oxygenation, and the form that nutrients are in. Today, sponges dominate many hard-substrate environments, but especially where most of the available nutrients are in the form of suspended particles - for example, along the sides of oceanic trenches, or on certain rocky shores. If the subsurface of the sediment is anoxic (or made of rock), then buried nutrients are less accessible, and the emphasis shifts towards suspension-feeders. At that point the more subtle factors come in, and sponges, sea squirts, crinoids and the like vie for dominance. Sometimes we see individual sponge species that thrive in one spot but not the surrounding area, and we still don't know why; it may be related to exact temperature or salinity (etc.) profiles, though, especially as living demosponges are effectively symbiotic colonies of sponges with diverse bacterial floras. There is also the aspect of sponges and mobile detritivores influencing each other directly: if the former are abundant, then their spicules start to fill the sediment, making it harder to dig through, and much harder to digest. In shallow water, these spicules can actually stabilise the sand and allow other organisms to colonise (we see this in the Builth Inlier), but in deep water the effect may be more towards impeding burrowing worms and arthropods. So much to explore...!  |
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Post by ammocarbsteve on May 2, 2015 5:37:48 GMT -5
Joe.... Yes thats what I was trying to get at... Although these 'ideal' conditions will inevitably change quite significantly to allow different groups to thrive and dominate in particular considering the time factors involved in laying these sediment layers down... Thats why its intriguing that the sponges dominated this exposure... Many questions to ponder....
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Post by pleecan (Peter Lee) on May 21, 2015 21:30:21 GMT -5
Excellent! A big congratulations to you Joe and Lucy! Well done!!! PL
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Post by Joe Botting on May 26, 2015 4:09:15 GMT -5
Thanks Peter! We've had a bit of nice feedback so far, but silence from most quarters. It'll be interesting to see the response when it starts getting cited... IF it starts getting cited! ;D
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