[Coral-List] How can we "bleach proof" transplanted coral nurseries? (Scott Wooldridge)

Sean Beckwith stbeckwith at mail.usf.edu
Fri Aug 25 15:34:55 EDT 2017


Thank you for that message; it provides some great ideas and some important
questions.  Regarding co-transplanting, it seems that it would make good
sense to co-transplant macro-algae such as Halimeda that do precipitate a
lot of CaCO3.  The buffering effect of additional calcareous sediment
produced by Halimeda may be beneficial, particularly in the winter as
seagrasses die-back (and therefore draw down less CO2), pH levels are at
their lowest (most acidic), and dissolution occurs in micro-environments.

I guess I'm a little confused by this sentence:  "Note: seaweed precipitate
no (or little) CaCo3 (= source of CO2 to seawater)"

Particularly, regarding CaCO3 (i.e., calcareous organisms) as a source of
CO2...  Calcification lowers pH by freeing up H+ ions; likewise, the
dissolution of CaCO3 (dissolving sediments, skeletons, shells, etc.)
increases pH and removes CO2.  And, photosynthesis increases pH (and Total
Alkalinity slightly), while respiration lowers pH (and TA, slightly).  For
corals, ultimately it comes down to how good an environment is for
calcification, and this depends on the two-way balance between net
calcification/dissolution and net photosynthesis/respiration.

Back to the point of whether CaCO3 is a net souce of CO2 to seawater...  If
calcification is dominant, then this is a net source of CO2 to the
seawater.  However, organisms are happily calcifying.  If dissolution is
dominant, then this results in a net decrease of CO2 in the seawater.  If
you're at such a low pH that calcium carbonate is dissolving, though, and
breaking down to carbonic acid and mostly to aqueous CO2, then wouldn't all
of the corals be non-existent by this point?  Additional points to
consider... seaweeds and seagrasses also produce some amount of CO2 through
their respiration (net positive production of CO2 at night); in winter,
additional CO2 is created through the respiration of micro-organisms
decomposing the portions of leaves, etc. that die back.

Absolutely, there must be a benefit to co-transporting seaweeds with
corals.  Corals downstream of seagrass beds have shown resistance to ocean
acidification.  I would think that both calcareous and non-calcereous
seaweeds could prove to be beneficial.

Thank you again for the post and for the links,

*Sean Beckwith, M.S.*
Geological Oceanography
University of South Florida - College of Marine Science
stbeckwith at mail.usf.edu

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