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Impacts of geography, taxonomy and functional group on inorganic carbon use patterns in marine macrophytes
Author(s) -
Stepien Courtney C.
Publication year - 2015
Publication title -
journal of ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.452
H-Index - 181
eISSN - 1365-2745
pISSN - 0022-0477
DOI - 10.1111/1365-2745.12451
Subject(s) - macrophyte , total inorganic carbon , ecology , mesocosm , abiotic component , environmental chemistry , biology , carbon dioxide , chemistry , nutrient
Summary Carbon uptake in terrestrial plants functions under near‐constant source carbon dioxide ( CO 2 ) concentrations and isotopic ratios, but aquatic macrophytes operate in a more complex system where environmental fluxes and biotic interactions undermine assumptions of constant CO 2 concentration and 13 C/ 12 C. Many marine macrophytes not only passively access CO 2 for photosynthesis, but also actively concentrate CO 2 and bicarbonate ( HCO 3 − ) using carbon concentration mechanisms ( CCM s). These processes change macrophyte carbon fractionation signatures ( 13 C/ 12 C) and elevate seawater pH as high as 10.4 in mesocosm pH assays, in which the pH value reached is termed pH*. I assembled a global data set of 2027 marine macrophyte δ 13 C and pH assay values for 664 species to assess (i) how macrophyte δ 13 C varies with the abiotic parameters such as sea surface temperature ( SST ), latitude and habitat, and the organismal traits of taxonomic and functional group membership and (ii) how species δ 13 C is related to CCM presence or absence, as determined by a pH drift assay. Across 613 macrophyte species, collection site distance from the equator was negatively related to species δ 13 C, while collection site variance in SST was positively related to species δ 13 C. Macrophyte tissue δ 13 C differed among oceans as well as in intertidal versus subtidal habitats. Species from phylum Rhodophyta had the lowest δ 13 C, and functional group was related to δ 13 C, largely due to higher δ 13 C in calcifying species. Analysis of 141 species with paired pH*–δ 13 C data found that these metrics of CCM presence are not independent. As species δ 13 C increases so does the probability of species pH* > 9.0, a threshold value of CCM presence in pH assays. Synthesis . CCM s revealed species patterns in communities at every scale investigated, from local emersion gradients to oceanic and global gradients. Trends in macrophyte δ 13 C values indicate that macrophytes rely more on CO 2 further from the equator, but have increased use of HCO 3 − at sites with high temperature variance, patterns that may be driven by species turnover rather than intraspecific variation. Patterns in species CCM s will be crucial to understanding how macrophyte communities respond to ocean acidification‐induced changes to SST and variability.