How does rising atmospheric CO2 affect marine organisms?

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Lowly Plants Turning Back Landward Advances of Rising Seas
Baustian, J.J., Mendelssohn, I.A. and Hester, M.W. 2012. Vegetation's importance in regulating surface elevation in a coastal salt marsh facing elevated rates of sea level rise. Global Change Biology 18: 3377-3382.

The authors write that "as sea level rises, coastal wetlands have the ability to maintain their position in the intertidal zone through the accumulation of both organic and inorganic materials," citing the studies of Redfield and Rubin (1962), Hatton et al. (1983), Morris et al. (2002), Nyman et al. (2006) and McKee (2011). And they indicate that this ability is largely governed by the production of roots, rhizomes and shoots belowground that can "maintain, and even increase, marsh surface elevation (Nyman et al., 1993; Turner et al., 2001; Cherry et al., 2009)," while reporting that "the density of stems aboveground can influence sedimentation on the marsh surface," citing Gleason et al. (1979), Morris et al. (2002) and Li and Yang (2009).

What was done
In further study of the subject, Baustian et al. measured elevation change and surface sediment accretion over a four-year period in recently subsided, unvegetated Louisiana (USA) marshes - caused by prior drought-induced marsh dieback - in pairs of planted (with the dominant salt marsh macrophyte Spartina alterniflora) and unplanted plots, comparing soil and vegetation responses in these plots with paired reference plots that had neither experienced dieback nor subsidence.

What was learned
The three U.S. scientists determined that "surface accretion rates were lowest in the unplanted plots at 2.3 mm/year, but increased in the presence of vegetation to 16.4 mm/year in the reference marsh and 26.1 mm/year in the planted plots."

What it means
In the concluding sentence of their paper, Baustian et al. declare that their results "show that under certain real-world circumstances S. alterniflora can cope with increased flooding, and therefore may be able to survive the stresses of future sea level rise."

Cherry, J.A., McKee, K.L. and Grace, J.B. 2009. Elevated CO2 enhances biological contributions to elevation change in coastal wetlands by offsetting stressors associated with sea-level rise. Journal of Ecology 97: 67-77.

Gleason, M.L., Elmer, D.A., Pien, N.C. and Fisher, J.S. 1979. Effects of stem density upon sediment retention by salt marsh cord grass, Spartina alterniflora Loisel. Estuaries 2: 271-273.

Hatton, R.S., DeLaune, R.D. and Patrick Jr., W.H. 1983. Sedimentation, accretion, and subsidence in marshes of Barataria Basin, Louisiana. Limnology and Oceanography 28: 494-502.

Li, H. and Yang, S.L. 2009. Trapping effect of tidal marsh vegetation on suspended sediment, Yangtze Delta. Journal of Coastal Research 25: 915-924.

McKee, K.L. 2011. Biophysical controls on accretion and elevation change in Caribbean mangrove ecosystems. Estuarine, Coastal and Shelf Science 91: 475-483.

Morris, J.T., Sundareshwar, P.V., Nietch, C.T., Kjerive, B. and Cahoon, D.R. 2002. Responses of coastal wetlands to rising sea level. Ecology 83: 2869-2877.

Nyman, J.A., DeLaune, R.D., Roberts, H.H. and Patrick Jr., W.H. 1993. The relationship between vegetation and soil formation in a rapidly submerging coastal marsh. Marine Ecology Progress Series 96: 269-279.

Nyman, J.A., Walters, R.J., DeLaune, R.D. and Patrick Jr., W.H. 2006. Marsh vertical accretion via vegetative growth. Estuarine, Coastal and Shelf Science 69: 370-380.

Redfield, A.C. and Rubin, M. 1962. The age of salt marsh peat and its relation to recent changes in sea level at Barnstable, Massachusetts. Proceedings of the National Academy of Sciences USA 48: 1728-1735.

Turner, R.E., Swenson, E.M. and Milan, C.S. 2001. Organic and inorganic contributions to vertical accretion in salt marsh sediments. In: Weinstein, M. and Kreeger, K. (Eds.), Concepts and Controversies in Tidal Marsh Ecology, Kluwer Academic Publishing, Dordrecht, the Netherlands, pp. 583-595.

Reviewed 20 March 2013