[Coral-List] coral calcifiction paper

[Richard Dunne]

For measurement of solar radiation the authors chose sensors which 
record units of lux (a measure of human visual perception of 
brightness).  As far as I can tell these measurements were above water, 
presumably on a horizontal surface (they don't say), although if this 
was a buoy moving with wave motion then this would produce added 
variability in the readings. They then use this as one of their 
environmental inputs to their Structural Equation Modelling.

Lux cannot be converted to units of PAR (photosynthetically active 
radiation) or irradiance unless you also know the spectral composition 
of the light at the time of measurement. As regards photobiology and 
coral calcification, measurements in lux are thus pretty meaningless. 
Worse still the fact that underwater both the spectral power 
distribution and irradiance will have varied with depth and changes in 
water quality, the net effect is not encouraging if you are using this 
to see if there is a relationship between calcification and solar 
radiation.

The authors found that "the lack of correlation with light ......   are 
inconsistent with anticipated results". Quelle suprise! Rubbish in - 
rubbish out.

Richard P Dunne

On 10/11/2017 23:17, Douglas Fenner wrote:
> Environmental controls on modern scleractinian coral and reef-scale
> calcification.  Scientific Reports
>
> http://advances.sciencemag.org/content/3/11/e1701356?utm_campaign=toc_advances_2017-11-10&et_rid=17045989&et_cid=1656609
>
> Open-access
> Abstract
>
> Modern reef-building corals sustain a wide range of ecosystem services
> because of their ability to build calcium carbonate reef systems. The
> influence of environmental variables on coral calcification rates has been
> extensively studied, but our understanding of their relative importance is
> limited by the absence of in situ observations and the ability to decouple
> the interactions between different properties. We show that temperature is
> the primary driver of coral colony (*Porites astreoides* and *Diploria
> labyrinthiformis*) and reef-scale calcification rates over a 2-year
> monitoring period from the Bermuda coral reef. On the basis of multimodel
> climate simulations (Coupled Model Intercomparison Project Phase 5) and
> assuming sufficient coral nutrition, our results suggest that *P.
> astreoides* and *D. labyrinthiformis* coral calcification rates in Bermuda
> could increase throughout the 21st century as a result of gradual warming
> predicted under a minimum CO2 emissions pathway [representative
> concentration pathway (RCP) 2.6] with positive 21st-century calcification
> rates potentially maintained under a reduced CO2 emissions pathway (RCP
> 4.5). These results highlight the potential benefits of rapid reductions in
> global anthropogenic CO2 emissions for 21st-century Bermuda coral reefs and
> the ecosystem services they provide.
>
> Cheers,  Doug
>