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Mangrove Forests Can Reduce Acidification of Coastal Sea Water

Paper Reviewed
Sippo, J.Z., Maher, D.T., Tait, D.R., Holloway, C. and Santos, I.R. 2016. Are mangroves drivers or buffers of coastal acidification? Insights from alkalinity and dissolved inorganic carbon export estimates across a latitudinal transect. Global Biogeochemical Cycles 30: 753-766.

In providing some background for their study, Sippo et al. (2016) write that "the relative proportions of alkalinity and dissolved CO2 [CO2*] within the dissolved inorganic carbon (DIC) exported from mangroves is unknown; and, therefore, the effect of mangrove DIC exports on coastal acidification remains unconstrained." So to thus provide what has long been missing in this regard, they "measured dissolved inorganic carbon parameters over complete tidal and diel cycles in six pristine mangrove tidal creeks covering a 26 latitudinal gradient in Australia and calculated the exchange of DIC, alkalinity, and [CO2*] between mangroves and the coastal ocean."

This work revealed the existence of "a mean DIC export of 59 mmol m-2 d-1 across the six systems. And the five Australian scientists state that "if the Australian transect is representative of global mangroves, upscaling our estimates would result in global DIC exports of 3.6 ± 1.1 Tmol C yr-1, which accounts for approximately one third of the previously unaccounted for mangrove carbon sink." Concurrently, Sippo et al. additionally report that "alkalinity exchange ranged between an import of 1.2 mmol m-2d-1 and an export of 117 mmol m-2d-1 with an estimated global export of 4.2 ± 1.3 Tmol yr-1, which they say is "equivalent to ~14% of global river or continental shelf sediment alkalinity fluxes."

Consequently, and in light of these data-based calculations, Sippo et al. go on to conclude that "mangrove-derived alkalinity exports may be one of the largest sources of alkalinity to the tropical coastal ocean and provide a localized buffering effect against coastal acidification." And that should be extremely good news for many marine plants and animals.

Posted 21 November 2016