Question about effect of tsunami on marine life

[Nancy]

What is the effect of a tsunami on marine life? Does it greatly disturb costal marine life - what about further out in the ocean?

We hear so much about the effect on people and property along the shore but never about the effect on the shore and its creatures, or on ocean inhabitants.

Nancy

 

[Steve O'Shea]

I don't know Nancy; I think it would be extremely, immediately disruptive (devastating) to coastal/intertidal life, but not-so-much that further offshore (at a guess 30+m depth); subsequent effects will likely include waters laden with earth and debris retreating, dumping tons of sediment at greater depth, smothering everything.

From memory, something I taught earlier on, a thin veneer of sediment 4mm deep deposited on the seabed in a coastal region around Auckland (New Zealand) caused complete annihilation of all infauna over a 7-day period. 4mm isn't a lot of sediment!

It's a tragic state of affairs, what has just happened. We had an 8.1 earthquake south of NZ a couple of days ago, but the tsunami was something like 20cm; to get two major earthquakes of this magnitude so close together is frightening!

 

[tonmo]

I would imagine that along with the giant waves themselves, the massive vibrations from the 9.0 earthquake would have shocked and devastated marine life quite a bit on its own.

One of these articles stated that tsunamis can travel up to 500km per hour. That's got to have quite an effect on currents, etc.!

 

[Snafflehound]

Waves on Coasts

Like ordinary waves, tsunamis have the greatest effects on coastlines. Out in the open ocean one may not even notice when a tsunami wave passes by.

 

[Phil]

I think it would be extremely, immediately disruptive (devastating) to coastal/intertidal life, but not-so-much that further offshore (at a guess 30+m depth); subsequent effects will likely include waters laden with earth and debris retreating, dumping tons of sediment at greater depth, smothering everything.

I would have thought that these conditions are perfect for fossil formation. Rapid deposition of silt and sediment onto the seafloor burying anything carried along with the retreating tidal waters or living at depth makes these conditions ideal. Animal and plant remains can be buried in oxygen-deficient silt at depths where bacteria may not survive and predators are unable to pick at carcasses. I'd imagine that such assemblages would be very jumbled in such strata and very mixed as to the animals and/or plants they contain.

There are extensive examples of these 'Tsunami Beds' recorded from the Gulf of Mexico, in places many metres thick, where the meteorite allegedly impacted 65mya probably causing the death of the dinosaurs. (Though these particular beds are not very fossiliferous).

 

[Colin]

We have work mates in Sri Lanka right now along with friends in Thailand, I hope they are okay.

I imagine that a lot of destruction will happen to coral reefs surrounding these land masses and islands. But this has been going on for millions of years and the animals and plats will be able to bounce back.

 

[tonmo]

We have work mates in Sri Lanka right now along with friends in Thailand, I hope they are okay.

Me too. The loss of human life in this catastrophe is unfathomable.

 

[cthulhu77]

watching cnn last night was horrific...watching people drown...horrible. simply horrible.

 

[atticus_finch]

IMHO, a major mitigating factor in human pursuit of knowledge of inner space (eg. the oceans), as well for outter space (eg. the universe) is our definition of space. IMHO, we are all too ready to assume that space means emptiness; that when matter is not observible empirically to the human eye, it denotes emptiness. IMHO, this is not the case. Both inner- and outter space are full of matter, and forces which move matter. We must desist from this approach if there is any hope of true knowledge. It has always been my view that life within the oceans is more complex and interesting than terrestial life. It holds the key for understanding of life, both inner- and outter.

JMO.. ~a.f.

 

[TPOTH]

*dredging memories from physics lessons*

The impact of a tsunami offshore is likely to be nil, iirc the product of depth and amplitude is a constant (Google could help us here) so above the abyssal plains (or any area 4000+m deep) the tsunami will have only a 1-2 meters amplitude (hence the reason why boats are safer at sea than in the narbour in times of tsunami)... actually you could hardly feel it. No more than a very "long" wave.
When approaching the coast, the depth decreases dramatically and thus the amplitude increases creating huge devastating waves.

I'm wondering if the Indonesian village on stilts i did my MSc project in is still standing The impact of the reef life must be huge as well. However I'm thinking that reefs and marine life as a whole have been around for a looong time so it feels unlikely that the tsunami/earthquake would wipe them out. Along the same line of thought, it's possible that recovery time after those events is extremely long (see bottom trawling impact) and thus in the light of human lifespan, marine ecosystems could be seen as annihlated....

TPOTH

 

[Emperor]

I have been pondering the connection with the spate of whale beachings at the end of November.

There is some suggestion that the quake in Tasmanian may have unlocked the plate sor been a precursor:

http://www.eians.net/2004/12/27/27did.html

I suspect the 20 odd days between the beachings in Tassie and NZ and the quakes is too great a lag time but I thought I'd throw it out there.

On the technical front the tsunami is a pressure wave through the water (imagine an aquatic Newton's Cradle) until it hits shallow water and then it builds up into a wave (some reports suggest the sea retreated 200 metres as the wave built). I'm unsure what the effects of the passing wave in deep water is but (as has been said) its impact will largely be coastal. I would iamgine reefs got pounded badly not good for their ecosystems but they may have caused waves to break offshore saving lives (I suspect the Maldives did OK, despite their low heights, because of the reefs).

Oh and a random ceph link (sort of) tsunami can also be known as seiche waves (although these tend to be smaller) and sieche is French for cuttlefish

-----------------
And if anyone wants to donate anything to the relief effort:


Care
www.care.org
www.careinternational.org.uk/donate/donate.php

Red Cross/Crescent
www.redcross.org/article/0,1072,0_312_3870,00.html
www.redcross.org/donate/donate.html
www.ifrc.org

Oxfam
www.oxfam.org.uk/what_we_do/emergencies/country/asiaquake/
www.oxfam.org.uk/what_you_can_do/give_to_oxfam/donate/asiaquake1204.htm

 

[Steve O'Shea]

I suspect the 20 odd days between the beachings in Tassie and NZ and the quakes is too great a lag time but I thought I'd throw it out there.

Emps, a VERY interesting connection!! Mesonychoteuthis is known from the Macquarie region, and Gonatus is also abundant at this locals (retained in trawls - pers com. George Jackson some years ago). I had been quietly thinking away that one of the last places that these whales had been feeding had been this far south (off Macquarie Island), but I didn't know enough about the whales migratory patterns to know whether this was possible (and was going to look into this in coming weeks).

What would really clinch this for me would be to identify some benthic octopus beaks in the stomachs of these whales, but there is none - not one - zip even! The octopus fauna of the Macquarie region is quite different from that off New Zealand (especially cirrates), but the only octopus thus far found in the stomachs is Haliphron atlanticus (aka Alloposus mollis). I still cannot figure this out - how an animal (whale) can have a mix of Antarctic and subtropical/tropical (Haliphron) species in the stomach - from which direction had it been migrating (North to South or South to North). The alternative is that Haliphron is more abundant in or proximal to New Zealand waters (particularly South of New Zealand) than was earlier recognised (but we've only just recorded the adult from here, based on a single specimen). Moreover, the Haliphron beaks in these stomach contents are not large - nowhere near the size of the adult recorded from here - and as subadults/juveniles are usually far more common (in trawls, and dictated by population dynamics) I would have expected them in collections by now. So, where have the whales been feeding? [Perhaps migrating North from the Antarctic into southern Tasmanian/Australian waters, then East to New Zealand where they stranded???]

A colleague here has been taking tissue samples from these stranded whales; I'll trundle on over and have a word with him when uni starts up again next year to see whether genetic markers are telling him anything about the whale migratory patterns. It would be sensational if someone had been marking these things with satelite tags so that the actual migratory path could be determined (and for the male and female this is likely to be quite different).

 

[atticus_finch]

TPOTH, Emporer, Mr. O'Shea: thanks for informative posts.

 

[Colin]

Sky news had been trying to make a link between the whale beachings and earthquakes too, but i missed the main feature...

I cant find it on their webpage :?

 

[Emperor]

Ok more rather random rambling:

More on the Macquarie Islands quake (a masive earthquake itself with one major aftershock - 8.1 on the Richter scale) on the 24th December (although it has largely been lost in the news):

An earthquake on a remote Antarctic archipelago home to 850,000 King Penguins was the strongest on earth in four years, seismologists say.

The quake hit 400km (250 miles) off the Macquarie Islands on Friday, measuring 8.1 on the Richter scale.

http://news.bbc.co.uk/1/hi/world/asia-pacific/4123927.stm

Also:
http://www.planetark.com/dailynewsstory.cfm/newsid/28721/story.htm

Although there is a lot of debate (and no clear answers) about animals and earthquakes:

http://news.nationalgeographic.com/news/2003/11/1111_031111_earthquakeanimals.html

it is believed the land animals sensed something and got out of the way:

Wildlife officials in Sri Lanka expressed surprise Wednesday that they found no evidence of large-scale animal deaths from the weekend's massive tsunami - indicating that animals may have sensed the wave coming and fled to higher ground.

http://seattlepi.nwsource.com/national/apasia_story.asp?category=1104&slug=Quake Sri Lanka Animals

Now rumbles or noise (like infrasound which elephants can detect) can also be detected by us so it isn't clear what (if anything) they are detecting but it is thought quartz grains when sheared can release some charge and even glow so...........

There is some discussion on the whale beaching links here:

This blames oil prospecting but also notes a further beaching on the 27th (nice little time line of events):
http://www.independent-media.tv/item.cfm?fmedia_id=10211&fcategory_desc=Environment

[edit: I should say the above also has good diagrams of quake epicentres, etc.]

On the sperm whales beached on Tasmania on the 27th (also links this to the oil prospection):
http://www.globalsurfnews.com/news.asp?Id_news=15276
http://www.abc.net.au/tasmania/news/200412/s1272918.htm

The last one has this:

A zoologist says it is possible there is a link between tidal surges from the Indonesian earthquake and tsunami and the whale deaths.

University of Tasmania zoologist Mark Hindell says tidal surges from seismic activity may have contributed to the latest deaths.

"It is possible, in fact there was a small amount of seismic activity just before the last strandings as well, but we also get many, many strandings when we don't get any seismic activity," he said.

"So it's very difficult to tease out hard and fast rules for this sort of thing."

It would be interesting to see what/where/when that oil prospection was the beaching/earthquake link may be there. I would also imagine this prospection would also impact other less visible denizens of the deep (hasn't there been a thread on that somewhere else?).

[edit: Yep the seismic squid thread is here:

www.tonmo.com/phpBB/viewtopic.php?t=3049

There are probably a number of ways you can join the dots here.]