sharkman6224 at my-deja.com
sharkman6224 at my-deja.com
Thu Jan 20 04:25:43 EST 2000
Richard at irchouse.demon.co.uk [mailto:Richard at irchouse.demon.co.uk]
>>A bit of the subject but I think that the lower diversity, cold water
>>areas of the world are more productive than the high diversity, warm
>>waters. This is probably due to the oxygen saturation issues.
An interesting point - if I may add some additional info. Polar waters
can be productive (Arctic = 365g C m-2 y-1 - similar in Antarctic but
patchy). However, dispite the greater tendency of gasses to diffuse at
low temperatures, the reduced photoperiod and low temperatures can
inhibit phytoplankton photosynthesis. Indeed, the instability of the
surface waters is important in the Antarctic. Here, wind-induced mixing
often carries phytoplankton below the crtitcal depth (the point at which
respiration = photosynthesis) causing death.
In the Arctic, the large input of freshwater results in an increased
production level (as seen where freshwater enters rivers all over the
For comparison, the two most productive ecosystems on the planet are
Tropical Rainforests (I don't have a figure to hand), and Coral Reef
Sytems (ca. 5000g C m-2 y-1)!
>>After all the great fisheries of the world tend to be in the cold
>>waters (Cod, Herring etc.) and the great whales move to the edges of
>>the ice shelf to feed.
The abundance of krill (and thus fish) to be found in Polar waters is
the result of nutrient upwelling! Due to the meeting of water masses
from surrounding oceans, circumpolar deep water, which is nutrient rich
(deepsea nitrates etc.) enters the antarctic ocean. This upwelling of
deep water around Antarctica produces the worlds largest expanse of
highly fertile open sea (Tait & Dipper, 1998). However, there is a
paradox, because of the patchiness of these upwellings there is
relatively low biomass!
Thus, although the Polar waters are productive, tropical coral reef
areas (such as those I referred to in my original posting) are still
overall more productive!
>>I am prepared to be wrong on this it is not my area!
Thanks for pointing out my flaw - I should have explained my terminology
Anyway, in an attempt to relate this to the Megalodon debate (of which I
sadly missed the original one!), I agree with the posting made the other
night (I forget the author's name...sorry!!) - from a biological stand
point it is illogical to think that the Megalodon still exists in the
oceans. It is most likely that when the whales migrated to the Poles,
the Megatooth couldn't follow. As pointed out in the last posting,
even if we assume that Megalodon possessed the Lamnoid Countercurrent
Heat Exchange System, it is still not likely to have been able to
withstand the temperatures that the "endothermic" (I use this word
cautiously as it's missleading!) could - we can see this by looking at
the lack of White Sharks in the Antarctic (despite the ubiquitous
Anyway, thanks for taking the time to read this posting and I hope
someone found it interesting - if I've made any errors or missed
anything important please feel free to correct me!
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