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A multistressor model of carbon acquisition regulation for macroalgae in a changing climate
Author(s) -
Dudgeon Steve,
Kübler Janet E.
Publication year - 2020
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.1002/lno.11470
Subject(s) - bicarbonate , photosynthesis , ocean acidification , total inorganic carbon , context (archaeology) , productivity , carbon dioxide , carbon cycle , climate change , environmental science , carbonate , primary production , atmospheric sciences , carbon fibers , ecology , chemistry , environmental chemistry , biology , botany , ecosystem , paleontology , materials science , macroeconomics , organic chemistry , composite number , economics , composite material , geology
It is widely hypothesized that noncalcifying macroalgae will be more productive and abundant in increasingly warm and acidified oceans. Macroalgae vary greatly in the magnitudes and interactions of responses of photosynthesis and growth to multiple stressors associated with climate change. A knowledge gap that exists between the qualitative “macroalgae will benefit” hypothesis and the variable outcomes observed is regulation of physiological mechanisms that cause variation in the magnitudes of change in primary productivity, growth, and their covariation. In this context, we developed a model to quantitatively describe physiological responses to coincident variation in temperature, carbonate chemistry and light supply in a representative bicarbonate‐using marine macroalga. The model is based on Ulva spp., the best understood dissolved inorganic carbon uptake mechanism among macroalgae, with data enabling synthesis across all parameters. At boundary layer pH < 8.7 most inorganic carbon is taken up through the external carbonic anhydrase (CA ext ) mechanism under all conditions of photosynthetic photon flux density, temperature, and boundary layer thickness. Each 0.1 unit decline in pH causes a 20% increase in the fraction of diffusive uptake of CO 2 thereby lessening reliance on active transport of bicarbonate. Modeled downregulation of anion exchange‐mediated active bicarbonate transport associated with a 0.4 unit decline in pH under ocean acidification is consistent with enhanced growth up to 4% per day without increasing photosynthetic rate. The model provides a means to quantify magnitudes of change in productivity under factorial combinations of changing temperature, p CO 2 , and light supply anticipated as climate changes.