This promises to be a pretty big article and has already been picked up by a number of other popular news outlets, including Nature, Scientist Live, Science Daily, and a host of others...
What the frakkin fruk is a global carbon budget?? What does it matter?? Why should I care?? How are echinoderms involved, anyway???
Carbon, Carbon Cycles & etc...
Carbon is an important element to living organisms and all organic things on the planet. It cycles through living and unliving things, but it is used and reused in all organic systems.
If the "Force" from Star Wars was real, it would be carbon. It binds, us and ties all living things together. Where it gets built up or "sequestered" can be an important consideration for understanding these global cycles.
Carbon cycles through the atmosphere, into the oceans, through organisms, and so on... There are bigger, better websites, like this one, and of course, Wikipedia that more thoroughly outline the details of the carbon cycle. This is the broader idea which encompasses the whole notion of "carbon footprint" (= how much greenhouse gas created by an organization, event, or product),
A SUBSET of the global carbon cycle, of course, occurs in the Oceans. And we can see a diagram of how Carbon cycles through the marine realm...
But let's take a CLOSE-UP look at a specific part of the Marine Carbon Cycle....about "Decomposition & Mineralisation".
....and so, it is here with "Decomposition & Mineralisation" where the Echinoderm story begins....
Echinoderms (& Other organisms) Enter the Fray!
Echinoderms are essentially MADE out of a mineral called calcium carbonate (CaCO3), also known as limestone, chalk and several other names. The crucial part of this mineral is the carbonate, which is made out of carbon and oxygen. Thus, echinoderm bodies act as kind of a "bank" for carbon on the deep-sea bottom!
It sequesters or stores carbon as part of the process of recycling it back into the water column and beyond! But up til' now, the contribution of carbon to this system was poorly understood.
When echinoderms die (i.e. decompose), their bodies fall apart (i.e., disarticulate) and those carbonate pieces fall into and are buried into the sea bottom and begin the "carbon cycling" process.
Lebrato et al. found that on a global scale, echinoderms have a PRODUCTION rate of approximately .861 Pg of CaCO3 (Pg=petagrams=1 billion metric tons!) per year!! So echinoderms produce just short of of 1 billion metric tons of calcium carbonate a year!!
The amount of echinoderm carbonate, which is right now, present on ocean bottoms aka the "Standing stock" is about 2.11 Pg of CaCO3 from organisms on the continental shelves, slopes and abyssal depths (1000+ m).
Apparently, more then 80% of global calcium carbonate production from echinoderms comes from animals that occur between 0 and 800 meters!! With the highest amounts attributed to the shelf and upper slope.
The greatest amount of standing stocks included ophiuroids (i.e., brittle stars)....
asteroids (aka starfish or sea stars)
and sea urchins...LeBrato et al. calculated "standing stocks" (i.e., the amount present today) from all around the world with different species making up the overall CaCO3 standing stocks in different parts of the world. Much variation exists.
Apparently, more then 80% of the substantial CaCO3 stocks were found in shallower then 800 m depths, especially from 0 to 500 m.
To refine the number above, echinoderms "sequester" or "capture" about 0.1 gigatons of carbon per year. This is apparently MORE then is "captured" by benthic foraminifera but less when compared against what is "captured" by pelagic (those that live in the open ocean) organisms, which capture about 0.4 to 1.8 gigatons.
By comparison, human activities produce about 5.5 gigatons of carbon every year.
Perhaps most critical is that the authors have found that there are regions around the world where the minerals used to form calcium carbonate are undersaturated (i.e., not as rich in the minerals needed to from calcium carbonate).
The authors attribute this directly to ocean acidification with the gravest concern of what should happen when this reaches the richest "standing stock" areas (i.e., where the bulk of echinoderms occur).
So, we are now JUST learning about the importance of carbon (in the form of calcium carbonate) that is "built up" on the sea bottoms (i.e., the benthos). What happens if this cycle is interrupted? Will the loss of carbon (in the form of calcium carbonate) sequestered on the sea bottoms result in ecological changes or worse??
Time will tell...but for now, we now how important it is to look at echinoderms on the deep-sea bottoms....