"Hot" news - seaweed burns in winter?

Debbie MacKenzie debimack at auracom.com
Mon Apr 8 11:42:50 EDT 2002

Dear coral list,

Regarding marine organisms suffering undue "heat" stress, we have an
interesting aberration in intertidal seaweeds in Atlantic Canada at this
time. Some of you may be familiar with "Ascophyllum nodosum," if not, it's
the dominant brown seaweed in this temperate zone. The plant is a fairly
large, very long lived perennial - and individuals can live for many
decades. Ascophyllum with lowered pigmentation appears yellow, although the
color of the plant when it is healthy is a deep olive green. Anyhow, in
areas with the lowest nutrient regimes (highest intertidal points, lowest
water flow rates) Ascophyllum is now dying off. The dead seaweed initially
appears red, then black, looking for all the world like something that has
been burned. Inquiries to phycologists have received the consistent answer
that these plants have been damaged by excessive degrees of "heat"....which
was semi-plausible until the burnt effect started to appear in the winter.

I've posted an article on this with pictures at:
http://www.fisherycrisis.com/seaweed3.html   , in which I've argued that
the immediate stress killing these seaweeds is more likely to be
dessication than heat (we have low temperatures, high winds and low
relative humidity at this time, although the weather is completely normal
for this season, it seems to be killing off these stressed seaweeds.) Due
to their longevity, spanning decades, it appears that some Ascophyllum
plants are now finding themselves situated in a hostile environment, at a
location that was once hospitable. Has the quality of the seawater
deteriorated in recent decades to the point that it will no longer sustain
seaweeds in these (very clean) locations where they once thrived? That's
what it looks like to me - and although I'm certainly open to entertaining
other explanatory ideas, I've not seen any yet.

I've posted this to the coral list because, as you know, I've been trying
to plant a little seed of doubt that all the changes that we think we're
seeing due to elevated temperatures are in fact entirely hinged on
"heat"...and also that marine nutrient cycling might not be all that it
used to be...

Debbie MacKenzie

For directions on subscribing and unsubscribing to coral-list or the
digests, please visit http://www.coral.noaa.gov, click on Popular on the
menu bar, then click on Coral-List Listserver.

More information about the Coral-list-old mailing list