Hi Andrew, i currently trying to, in part answer, the same question, I writing a chapter for a book on climate change and aquaculture on coastal carbon stocks. So here is my take on the question. First in general, if you dont have it already, the book ocean acidification by Gattuso and Hansson, is a good andlatest general read on those aspects. More specifically your answer by my standpoint has 3 parts, physiological response to a range of independent variable, adaption and the type of adaption that evolutionary fitness criteria imparts. The latter im sure you are familiar with as this was addressed for coccoliths from work down at the MBA in Plymouth. The second, is about the genome variability and the time and possible adaption for selection that meets the ecosystems criteria for success, what ever that may be. The time for selection is mixed for chlamydomonas after 1000 s of generations in a lab experiment found nothing. However, to be fair it needs a population that has been subject to large variations in pH etc. for example upwelling regions. If you have info on this over the longterm, i would be grateful. The first, is the nature of the concentrating mechanism, whether it requires an external proton transferred into the cell producing calcium carbonate outside and extra pCO2 inside or the bicarbonate converted through the usual carbonic anhydrase. Either way, with lower pH comes higher pCO2 and if the light is sufficient, in which it may be lower from increased cloud cover, there is a excess of fixed carbon over nitrogen over its Redfield optimum. Or the lower supply of nitrogen from increased stratification will also produce or add to a highe carbon to nitrogen ratio. In other words autotrophs are plastic in their stochiometry but not consumers. Consequently, and in this way i m using stochiometric theory to predict that higher CN ratios will lead to more detrital proportions and lower consumer production. See Hessen et al reviews on this 2004, a series in Ecology 2004 on sequestration and stochiometry and Hessen and Andersen, 2008 in L&O.

This is what I have gathered for myself so far, if you have any info on upwelling acidification and changes over time on sequestration, i would be very grateful

Hi Andrew, i currently trying to, in part answer, the same question, I writing a chapter for a book on climate change and aquaculture on coastal carbon stocks. So here is my take on the question. First in general, if you dont have it already, the book ocean acidification by Gattuso and Hansson, is a good andlatest general read on those aspects. More specifically your answer by my standpoint has 3 parts, physiological response to a range of independent variable, adaption and the type of adaption that evolutionary fitness criteria imparts. The latter im sure you are familiar with as this was addressed for coccoliths from work down at the MBA in Plymouth. The second, is about the genome variability and the time and possible adaption for selection that meets the ecosystems criteria for success, what ever that may be. The time for selection is mixed for chlamydomonas after 1000 s of generations in a lab experiment found nothing. However, to be fair it needs a population that has been subject to large variations in pH etc. for example upwelling regions. If you have info on this over the longterm, i would be grateful. The first, is the nature of the concentrating mechanism, whether it requires an external proton transferred into the cell producing calcium carbonate outside and extra pCO2 inside or the bicarbonate converted through the usual carbonic anhydrase. Either way, with lower pH comes higher pCO2 and if the light is sufficient, in which it may be lower from increased cloud cover, there is a excess of fixed carbon over nitrogen over its Redfield optimum. Or the lower supply of nitrogen from increased stratification will also produce or add to a highe carbon to nitrogen ratio. In other words autotrophs are plastic in their stochiometry but not consumers. Consequently, and in this way i m using stochiometric theory to predict that higher CN ratios will lead to more detrital proportions and lower consumer production. See Hessen et al reviews on this 2004, a series in Ecology 2004 on sequestration and stochiometry and Hessen and Andersen, 2008 in L&O.

This is what I have gathered for myself so far, if you have any info on upwelling acidification and changes over time on sequestration, i would be very grateful

Hi John, it's the latter part of your response that I'm primarily concerned with at this stage. I'm working on the benthic food chain at the base, contrasting defensive biochemistry and 'secondary' metabolite production in a variety of algae growing in areas of long-term acidification at vent sites in the med with populations of the same species from nearby ambient non-acidified conditions. I'm working with folks at Aberystwyth here in the UK and at Palermo. My angle is studying effects of seawater conditions upon patterns of secondary metabolite production, both carbon dense and non-carbon dense, and grazer preference patterns correlating with these. Note the parens for 'secondary' and use of 'correlating'. ....

We don't have data on anything like your Chlamydomonas, but my colleague Jason Hall-Spencer is working on biofilms, he's on RG and may have interesting info for you. Mike Cunliffe at the MBA is also working on this, and I know that the Brownlee group may have info for you too.

So my interest is in whether there are taxonomic patterns in ccms that will affect the way the stoichiometric changes you refer to result in allocation of carbon and nitrogen to growth, secondary metabolite production etc. I guess I'm an ecologist trying to use this Q as a way of speeding up access to info on ccms in the three major algal clades, there's only so much algal phys I can read before getting jaded! I'll check out those reviews, I'm also interested in anything like ccms that would distinguish angiosperms from algae in their metabolic responses to OA.

I do have data on the CHN and phenols in 4 species of algae and a seagrass from a clean vent site in the Med which are joint IPR with colleagues in Aber, I'd be happy to share these once our MS is in submission if that would interest you? We're working on the ms at present.

Cheers

Andy

Kenneth,

My question was aimed at the level of biochemical/physiological differentiation between different algal groups in terms of the mechanisms they use to acquire carbon, our knowledge of these is growing rapidly but it's not my specific field. As you will see from my discourse with John G my concern is not with cycling of carbon into the inorganic or 'sequestered' state, but rather with the consequences of OA for the links between algae and heterotrophs.

As far as 'acidification' is concerned, I quite accept that the oceans are alkaline, but ocean acidification seems to be the (mis)nomer of choice in the field globally, and technically we're adding an agent to the oceans that, in tremendously over-simple terms, dissolves to form a weak acid.... However, acidification is technically a noun, not a verb, so yes, you are quite right; all we need to do now is get NOAA, NSF, NERC, ARC, IUCN etc etc to change their terms!

Sounds interesting, I'm sure you have a general handle on the physilogy of seagrass carbon concentrating mechanisms. nevertheless, are you familiar with a paper, the name escapes me, it looks at the low pH conditions of the caneozoic time of seagrass moving to aquatic ecosystems, in which it was suggested that low ph was necessary to compete with macroalage for reasons of the seagrass physiology. It then goes onto say that current trends may see seagrass competing more successfully for macrophyte niches.

I am familiar with the vent literature of course. My concern with what I have seen so far is that the studies do not constrain the interpretation with other factors than pH. I

Eg what is the difference in nutrient supply, sulphide toxicity, topdown control etc.

The other concern is pseudoreplication. Ideally you need to compare the vent site with a number of control sites to see if variance in effect lies outside natural variability. However, in this case the difference is so severe to discount any probs there.

I guess what I am trying to say that vent comparisons are not the perfect comparison because there are other independent variables that do not covary with a fall in pH in a more usual environment. Although i was fascinated inthat the vent environment did not affect the bryozoans. This is important for my work on seagrass longterm attractors (thesis should be in UTAS eprints by now Natural and Anthropogenic regime variance of a seagrass ecosystem : A late Anthropocene paeo-recontruction). In brief there was evidence of top down control on water born algae as food for bryozoans, controlled by self organisation of seagrass patchiness, that allowed enough exposed area for seagrass to take up light and nitrogen. The epiphytes were only covariant and can be eaten unlike the resistant to grazing of. The calcareous epibiont community.

The above studies are in contrast to a nice piece of paleowork on Flinders reef, Australia, reported in Science. The reefs pH fluctuated by 0.4 in acidity over 50 year cycles due to changes in residence time from wind strength (IPO frequency). Their found no effect on the corrals whatsoever, some sort of adaption.

So saying all that imam jealous of you study. A few years ago on our sail around most of the world with my partner Diana and our cat sailed around that part of the world. It was during the time of the latest volcanic eruption of Etna . The hatch was open we wondered why we we covered with ash when woke up Lol.

Keep in touch.

John Barry Gallagher , prefer Barry

anyone interested in this question should see:

Raven, J.A., Beardall, J., Giordano, M., Maberly, S.C., 2011. Algal and aquatic plant carbon concentrating mechanisms in relation to environmental change. Photosynth Res 109, 281-296.

and

Raven, J.A., Beardall, J., Giordano, M., Maberly, S.C., 2012, Algal Evolution in Relation to Atmospheric CO2: Carboxylases, Carbon Concentrating Mechanisms and Carbon Oxidation Cycles. Phil Trans Royl Soc Lond B 367, 493-507

Thanks to John Raven.