[Coral-List] Fw: ADMAT - Sea Urchins eating iron cannons and granite blocks...

Bill Allison allison.billiam at gmail.com
Fri Jan 11 12:37:39 EST 2013

That an interesting investigation Dennis. I see a lot of such behaviour
with seagrass blades in growth position used in addition to loose debris
and assumed it also contributes to stability vs wave action in shallow
water. Related to solar radiation:
Adams, N. L. (2001). "UV radiation evokes negative phototaxis and covering
behavior in the sea urchin Strongylocentrotus droebachiensis." MEPS 213:
Intertidal and subtidal Strongylocentrotus droebachiensis (Müller) often
hide among rocks or cover themselves with debris, including macroalgae,
mussel shells, and pebbles. Similar reactions in other species of sea
urchins have been interpreted as a response to bright sunlight. This study
examined the response of S. droebachiensis specifically to ultraviolet
radiation (UVR). In laboratory studies using artificial irradiation, S.
droebachiensis exposed to UVR (290 to 400 nm) and photosynthetically active
radiation (PAR, 400 to 700 nm) sought shade and covered themselves
significantly more frequently than those exposed only to PAR. In outdoor
aquaria, individuals were exposed to ambient solar radiation that was
filtered to create 4 treatments (dark, PAR, PAR + UVA, or PAR + UVA + UVB)
and observed for 6 h as total solar irradiance changed with time of day.
Sea urchins covered themselves with significantly more material when
exposed to PAR + UVA + UVB than in all other treatments, and in response to
total irradiance. The amount of covering by sea urchins exposed to PAR +
UVA (320 to 400 nm) varied over the course of the day, but were typically
less than those exposed to UVB (295 to 320 nm). These sea urchins covered
themselves more than those exposed to PAR alone or held in the dark. Sea
urchins exposed to PAR alone did not differ in the amount of covering from
those held in the dark, regardless of time of day. The amount of covering
correlated significantly with UVB and UVA irradiance independently, but not
PAR irradiance. This study does not rule out that multiple cues may cause
the covering response, but it demonstrates that S. droebachiensis seeks
shelter and covers itself in response to UVR, primarily UVB wavelengths or
a combination of UVA and UVB, presumably to avoid UV-induced damage.

On Fri, Jan 11, 2013 at 10:54 AM, Dennis Hubbard <dennis.hubbard at oberlin.edu
> wrote:

> Interesting observations. I spent two field seasons on Easter Island and
> observed what looks like *Diadema* boring into the lava substrate (oriented
> both vertical and horizontal). This is all the more interesting as the wave
> energy is so high on this side of the island that corals cannot recruit.
> Basalt is softer than granite, but harder than limestone. Steel is another
> issue.... wow!
> On the observation of their covering themselves, this sounds similar to the
> bahavior of *Tripneustes* in the Caribbean. Way back when I was still at
> West Indies Lab, one of our students tackled the question of why they
> covered themselves with trash. I'm a geologist, so this is outside my job
> description but my sense is that this is typically attributed to defense as
> an urchin covered with grass litter will blend in better.
> Anyway, the student cut up a sheet of polarizing material to approximate
> seagrass and put it into an in-situ enclosure with urchins. The urchins
> picked up the polarizing strips just like grass - I guess you work with
> what you have available. The interesting thing is that urchins are made of
> high-magnesium calcite that nucleates in one direction only: the c-axis of
> crystallographic growth. It turned out that the urchins were oprienting the
> strips perpendicular to that axis, in effect cross-polarizing the light.
> The result would have been a total blocking of light. The student concluded
> that this "uber-shading" reflected a strategy to reduce heat (or some other
> factor directly related to light) rather than affecting camouflage or just
> looking "new wave".
> Nature never ceases to surprise us.
> Dennis
> On Fri, Jan 11, 2013 at 4:49 AM, boc <boc at aquafact.ie> wrote:
> > Hello to all.
> >
> > I live on the west coast of Ireland where our local small urchin,
> > Paracentrotus lividus which occurs over much of the southwest and west
> > coasts, creates pits in intertidal pools on limestone pavement in which
> > they
> > then live. They cover themselves in pieces of shell under which
> Amphipholis
> > squamata can be found. Never thought urchins would work their way through
> > granite and steel though!
> >
> > BOC
> >
> > -----Original Message-----
> > From: coral-list-bounces at coral.aoml.noaa.gov
> > [mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of David Evans
> > Sent: 10 January 2013 20:49
> > To: coral-list at coral.aoml.noaa.gov; rookerj at tamug.edu
> > Cc: maritime_archaeology at yahoo.co.uk
> > Subject: [Coral-List] Fw: ADMAT - Sea Urchins eating iron cannons and
> > granite blocks...
> >
> > Hello All,
> >
> > Happy New Year!
> >
> > I was made aware of an interesting observation from a Marine Archaeology
> > list. I thought it would be useful to pass it on here for any further
> > input.
> > Dr. Simon Spooner of the Anglo~Danish Maritime Archaeological Team
> > www.admat.org.uk ) posted this observation on the Sub-Arch List server (
> > SUB-ARCH at ASU.EDU ) about bio-eroding sea urchins ( Reb Rock Boring Sea
> > Urchin  *echinometre lucunter*) on a shipwreck off the Dominican
> Republic,
> > boring holes into granite blocks and iron canon cargo at the wreck site..
> He
> > was asking if anyone has experience encountering something similar. I
> will
> > post an excerpt here:
> >
> > .... a shipwreck off Monte Cristi in the Dominican Republic...
> >
> > .... we noted an interesting biologic factor and wanted to know if anyone
> > on
> > the list has encountered such on their surveys.
> >
> > During the survey we noted that some of the granite blocks (over 60 of
> them
> > part of the cargo) which were in the shallows, less than 3 meters depth,
> > water temp arround 80 deg F, had holes "drilled" in them. In addition
> iron
> > cannons which appear to have been new cannons with the touche-holes not
> > drilled, also had holes in them. We have proved that these holes were
> made
> > by a particular type of sea urchin, the Reb Rock Boring Sea Urchin or
> > Echinometre Lucunter.
> >
> > -->Has anyone conducted a survey where they have encountered this,
> > -->either in cargo or on iron cannons?<--
> >
> > [additionally: "ADMAT is intending to return to the wreck site this
> summer
> > and i hope we can get some further research on these things as there are
> a
> > number of interesting questions they throw up, like how long to burrow a
> > hole and how fast to they breed?"]
> >
> > Many thanks
> > Simon
> > Dr. Simon Q. Spooner, BSc, MRICS, PhD, MIfA.
> > maritime_archaeology at yahoo.co.uk
> > Anglo~Danish Maritime Archaeological Team www.admat.org.uk
> >
> > \\\\\\\\\\\\\\ END EXCERPTS///////////
> >
> > I was sure some folks on the NOAA Coral list may have some input.
> >
> > Thanks!
> >
> > David J. Evans
> >
> > Bending Light
> > www.refractum.blogspot.com
> > davidjevans1818 at yahoo.com
> > _______________________________________________
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> > Coral-List at coral.aoml.noaa.gov
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> >
> >
> > _______________________________________________
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> >
> --
> Dennis Hubbard
> Dept of Geology-Oberlin College Oberlin OH 44074
> (440) 775-8346
> * "When you get on the wrong train.... every stop is the wrong stop"*
>  Benjamin Stein: "*Ludes, A Ballad of the Drug and the Dream*"
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"... the earth is, always has been, and always will be more beautiful than
it is useful."
William Ophuls, 1977. The Politics of Scarcity

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