bertoni said:
So it is. It seems I've fallen victim to one of the classic blunders -- not so well known as "Never get involved in a land war in Asia" or "Never go in against a Sicilian when death is on the line", but
apparently this is a common trap even actual scientists are prone to falling into.
Following up on the topic at hand, I found
a seminal paper about calcification -- or more accurately, its abstract, as the paper itself is behind a paywall -- that appears to confirm my speculation about the link between cocos and dinos being protons released by calcification reactions. Though of course, it bears mentioning that the notion that the calcifying organisms are cocos is, itself, speculation...
And pretty wild speculation, at that, as "benthic coccolithophores" sounds like the next best thing to an oxymoron. But it's a big ocean, and cocos evolved from coastal, shallow water organisms... Maybe this is an ancient adaptation resurfacing -- maybe cocos survive mass extinctions (or exploit the resulting ecological chaos) by retreating to shallow, oxygenated waters and reclaiming a long-lost niche in the microphytobenthos. Foraminifera or perhaps bacteria look like more likely suspects on paper, but calcifying bacteria would turn the surface of a sand bed into cement, which DNA hasn't reported (...though Quiet_Ivy did report her sand bed crusting over at one point), while cocos are world-class calcifiers, and DNA can't bring alk and Ca up to normal levels even with the dials turned up to 11. I don't know much about foraminifera other than that they're kinda cool, so we really need solid evidence from an afflicted DT to find out if we're dealing with cocos or forams or what.
This is from the paper that originally tipped me to what's going on:
Community and environmental influences on reef coral calcification said:
CO2 diffusion through the boundary layer surrounding an aquatic autotroph can support photosynthetic rates of about 0.2 u mol per m^2 per second... Algae and corals often have photosynthetic rates that are several times that fast, indicating that they use mainly bicarbonate. However, bicarbonate utilization requires additional protons (H+ + HCO3- = CH2O + O2). The protons may derive from H2O and HCO3-, with a corresponding efflux of OH- and CO3-. Large OH- and CO3- effluxes imply alkalinization and therefore CO2 depletion at the absorptive surface. This process reduces photosynthetic efficiency because of the Michaelis kinetics of CO2 fixation by the enzyme Rubisco (ribulose bisphosphate carboxylase oxygenase). Calcification provides an alternative proton source and potentially allows autotrophs to avoid most of the alkalinization and CO2 depletion that otherwise accompanies HCO3- utilization. ...
Nutrients may also affect reef calcification rates. Highly calcareous autotrophs such as corals and coccolithophorids calcify faster when nutrients are scarce and thrive in nutrient-deficient waters. McConnaughey and Whelan (1997) therefore suggested that calcification assists nutrient uptake. ...it might therefore accumulate NO3- and H2PO4- at least three and 10-100 times more strongly. Extracellular acidification should also improve NH4+ uptake slightly and slow Fe2+ oxidation, aiding in assimilation. Calcification's potential for improving nutrient assimilation therefore appears to be substantial. Moreover, seawater pH and alkalinity should affect this physiology much as they affect HCO3 assimilation. Photosynthesis and calcification may therefore become correlated, as will calcification and pH, even if the autotroph calcifies mainly to obtain nutrients. ...
Nutrients may directly suppress calcification, as was observed, for example, by Marubini and Davies (1996), and nutrients may encourage fleshy algae that compete with the calcifiers and feed their predators. Through such mechanisms, nutrients may reduce reef calcification. On the other hand, nutrients stimulate photosynthesis by both calcareous and noncalcareous autotrophs. By raising pH and the alkalinity:acidity ratio, reef calcification may be stimulated... This represents a metabolic cost to the calcifiers and may reduce their competitiveness in nutrient-rich situations. ...
...photosynthesis increases the alkalinity:acidity ratio, which reduces how efficiently calcification generates CO2. More calcification is therefore needed to obtain a particular photosynthetic benefit. Fleshy algae can thereby stimulate calcification in nearby corals.
This paper predates the DDAM model, though not by much, so this may be the authors casting about in search of an explanation for things they've seen in the field that's about to come from another direction. Or it may be that in some tanks, the rapid growth normally taken to be evidence that corals are in robust good health is actually signaling chronic stress due to low CO2.
In any event, extrapolating from the relationship between fleshy algae and calcifying corals to illuminate the possible relationship between dinos and cocos, it looks like all the photosynthesis happening at the surface of DNA's sand bed should push the cocos to calcify more rapidly in order to obtain CO2. Plus, the elevated pH that facilitates calcification reduces the efficiency of rubisco, which means primary producers need even more CO2, which means the cocos have to calcify that much more to get it. Everything points to diminishing returns driving higher and higher levels of calcification, which fits with the "titanium wall" limiting DNA's params.
It seems clear that even if ostis don't eat cocos (unlikely, given the nature of the enemy), they stand to benefit substantially by partnering with them, and that raises the question of what cocos get out of the deal. Obviously, they get a secure, calcification-friendly home, and if they're growing and reproducing quickly enough to stay ahead of predation by dinos and other organisms, they must also be getting a steady food supply. Cocos don't have gaps in their armor like dinos do to allow them to eat solid food (it's thought that one of the reasons some cocos are naked and others go through naked phases is to permit heterotrophic feeding) so they're dependent on dissolved nutrients, but they are thought to be able to access dissolved organic carbon, a nutrient pool that is for all practical purposes unavailable to other primary producers.
BTW, I poked around on Google Scholar for a while trying to turn up some papers linking calcification and bicarb photosynthesis in the microphytobenthos, but I came up totally dry. Maybe I just didn't think of the right keywords, but the closest I got was a paper from 2001 on the algal symbionts of radiolaria (which have siliceous armor) and planktonic foraminifera (many species of which have calcareous armor). Interestingly, in both cases the dominant photosymbionts were dinos, though other algae were also present.
Bacteriologists seem to be comfortable with the synergy between photosynthesis and calcification being split between separate organisms and the benefits shared, no doubt because they've spent years studying calcifying cyanobacterial mats and crusted-over desert sands. Given that dinos like to steal DNA from bacteria, perhaps they stole the genes to tap into this virtuous circle, and that's why they're dominant on foraminifera and radiolaria (...though I know nothing about silica deposition, so I don't know if it facilitates bicarbonate photosynthesis as calcification does) and how they mess with alk in some aquaria. But I don't know as anybody has seen evidence of, let alone investigated, that sort of coupling among eukaryotic microorganisms.
I'll try my luck with Google Scholar again and see if anything turns up.
Community and environmental influences on reef coral calcification
http://www.aslo.org/lo/toc/vol_45/issue_7/1667.pdf
For more insight into coral calcification, biology, and structure:
Geochemical Perspectives on Coral Mineralization
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.322.3234&rep=rep1&type=pdf
The chapter from
Evolution of Primary Producers in the Sea that covers coccolithophores:
Origin and evolution of coccolithophores: from coastal hunters to oceanic farmers
http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.431.2251&rep=rep1&type=pdf
Just because I like to geek on this stuff, note that one of the authors of
Community and environmental influences on reef coral calcification is Walter H. Adey, inventor of the algae scrubber. And in any discussion of calcification, Ted A. McConnaughey totally rates a name check, too.
psu.edu is Penn State, incidentally -- Google Scholar keeps steering me back there, so I'm guessing they've got a pretty good marine biology program.
--
taricha said:
A point on the "dirty" method that I haven't seen discussed much:
If elevated N and P are the definition of "dirty" then it may be harder to do than people think.
There was another lengthy dinoflagellate thread in which I believe the goal was to try to get rid of dinos by manipulating nutrient levels, particularly N, to get green algae to outcompete them. As you surmised, it didn't work, at least not consistently.
FWIW, I put this on the table about a month ago, as I don't know if it has been tried by anyone in either thread:
34cygni said:
Quiet_Ivy said:
I was keeping NO3 at 5ppm, the spike to 15 was a mistake. Phos at about .05 I was dosing NaNo3 at about 3ppm *daily*, and a (land plant based) P fertilizer weekly. Currently nitrate is still about 15 which is very odd. P undetectable.
Have you tried playing the stoichiometry card to encourage your phyto? I don't have the numbers for nannochloris, but IIRC a "typical" N
ratio for green and red phyto is around 30:1 to 50:1, so holding your N
ratio in that range may be helpful when dosing. Note that Redfield stoichiometry = 1.53 x ( NO3 ppm / PO4 ppm ) --
it's explained here -- so a 50:1 N
ratio would not be 2.5 ppm NO3 and 0.05 ppm PO4, for example, but closer to 1.5 ppm NO3 and 0.05 ppm PO4, as 1.53 x ( 1.5 / 0.05 ) = 45.9, or a roughly 46:1 ratio, and a 30:1 ratio would be about 1 ppm NO3 to 0.05 ppm PO4, while 5 ppm NO3 is about 150:1.
Dinos suck at absorbing nitrogen directly from the water column, but that's not to say they can't do it if there's enough around.
