"Hot" news - seaweed burns in winter?

[Ove Hoegh-Guldberg]

Except that colder than normal conditions will cause the identical
symptoms to those of elevated temperature (well established in the plant
physiological literature).  Given that warm disturbances like El Nino
events may also be accompanied/followed by periods of lower than normal
temperatures (which we have seen on the southern GBR in 1999 for example
- and, yes, coral bleaching in winter), the observation of "burning"
seaweeds in winter is not too disturbing.  What was the temperature
relative to the long term average?

Cheers,

Ove

-----Original Message-----
From: owner-coral-list at coral.aoml.noaa.gov
[mailto:owner-coral-list at coral.aoml.noaa.gov] On Behalf Of Debbie
MacKenzie
Sent: Tuesday, April 09, 2002 1:43 AM
To: coral-list at coral.aoml.noaa.gov
Subject: "Hot" news - seaweed burns in winter?

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...

cheers,
Debbie MacKenzie

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