Coralline Algae Tells Time

Scientists now have a way to accurately measure the thin layers in coralline algae to help determine historic temperature changes in the ocean. The discovery involves using a small laser to "vaporize the calcium-carbonate skeletons of coralline bands, and then measure the magnesium — a key indicator of temperature — in each one. The more magnesium inside each layer, the higher the ocean temperature during that growth cycle." "In each layer, we can now find out how much magnesium is in the (plant) for every month of its history," says Walter Adey. "It is amazingly precise and it's changed the whole game." Walter Adey? Where have we heard that name before? Hmm.. isn't he the Dynamic Aquaria, ATS guy? Way to go Walter.


Photo Credit: HANDOUT PHOTO, Walter Adey

Source:
East Coast organism offers wealth of climate data, researchers say

Related:
http://www.3reef.com/forums/algae/algal-turf-scrubbing-gets-boost-76577.html

 

This is very interesting maybe we are getting closer to understanding how the ocean Eco system really works, we might have a chance in turning coral reef loses around.

good article Matt

 

Is this quote correct? I'm thinking neither of the two bolded are true... or maybe it's a matter of definition?

Coral, however, only grows in the tropics. Elsewhere — in areas such as the Labrador Sea between Greenland and Canada, where coral reefs don't exist,


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Also, doesn't this presume that Mg/Ca concentrations haven't changed in X years? I'm not saying they have, but do we know they haven't? I wouldn't think they have in the past 100 years, but over the last 10000, I dunno, maybe. I'm thinking that in my tank, to a large degree, Mg and Ca are interchangeable.

Hypothetically, if my tank were 50 years old - I would say I probably have more Mg fluctuation that I do heat... Would this sort of test be able to tell the difference between a heat fluctuation and a Mg fluctuation? Or does it simply presume any Mg flux is directly attributed to only a heat flux?


I get heat impacts Mg concentrations, but it's not the only thing that does. On a big enough time line, so do meteorites, continental shift, etc. as Mg is released. Also, I wouldn't assume Mg release (coral decay?) and Mg consumption (coral growth) are necessarily 1:1. Also, seeing the type of time scale we're talking about ultimately, I wouldn't feel that being able to verify the past 50 years worth of data proves it is correct a thousand years back...

Just trying to understand, not saying I'm right or the article is wrong.

 

According to wikipedia: "Ocean salinity has been stable for billions of years, most likely as a consequence of a chemical/tectonic system which removes as much salt as is deposited; "

If it has been ascertained that salinity has been relatively stable for that long, one could assume magnesium concentrations remain relatively stable also.

I think that the article is based on the presumption that Coralline algae deposits magnesium at a constant rate at a given temperature. With that in mind, and a constant, stable source of magnesium, the major variable is ocean temperature.

Atmospheric temperature is something that has not been well recorded past 150 years, so I imagine ocean temperature is something that has been recorded even less as much. Using proxies becomes a way to reconstruct temperature data. With the oldest Coralline found being only 800 years old, it still doesn't give scientists much data to work with, but will at least allow them to narrow the gap in modern history.

I'm interested to know what the trends in Ocean temperature look like compared to atmospheric temperature; and I also wonder if this will help scientists case for/against global warming...

 

yes well, wikipedia is full of errors. It's hardly the last word on anything.

What I want to know is if we actually know this has been stable or something we are assuming based on soft evidence.

I agree, though, *if* this has been shown to be true, then yes, the temp would be the variable. I just question it's been shown to be true.

I'm not saying it isn't true, mind you. Just questioning it.

I agree it is logical the planet replenishes mg at same rate it depletes it, but that's not proof...

Although, I would think other factors would influence Coralline growth other than temp and available elements. Like, has an urchin ever crawled over that spot? Who knows.

 

Excellent point. The variable is going to be temp IMO. All other varibles have probably remained pretty stable in fluctuations, but not temp.

 

yes, you may be right...

but I think the question remains, do minute differences in concentrations of ions in seawater affect the rate at which coralline precipitates magnesium?

If so, then temperature may not be the only variable. Other variables, as we all know can be pH, dissolved oxygen and CO2 amounts as well... A scientist studying the proposed effect of coralline growth as it relates to temperature would have to know how all of these variables ALSO affect magnesium concentration. My guess is that they have taken this into account, but if they haven't then maybe they are missing part of the puzzle.

Here is an interesting article I found:

http://www.waterencyclopedia.com/Mi-Oc/Ocean-Chemical-Processes.html

and an excerpt:

there may be many more variables than I even mentioned... Just in my reading on this site, ocean salinity seems more complex than I previously thought...

 

I'm fairly sure I read somewhere that coralline is known to precipitate a magnesium to calcium ratio that directly reflects the ratio of the ions in the water. Lemme go look.

EDIT: Found it.

"Interestingly, coralline algae that normally packs a large amount of magnesium into their calcium carbonate deposits (>4 mole percent magnesium carbonate, or >1% magnesium by weight) has been shown to incorporate less magnesium when the magnesium content of the water is reduced. The amount incorporated is directly proportional to the magnesium concentration. "