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The influence of pore‐water advection, benthic photosynthesis, and respiration on calcium carbonate dynamics in reef sands
Author(s) -
Rao Alexandra M. F.,
Polerecky Lubos,
Ionescu Danny,
Meysman Filip J. R.,
de Beer Dirk
Publication year - 2012
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 - 10.4319/lo.2012.57.3.0809
Subject(s) - benthic zone , pore water pressure , calcium carbonate , diel vertical migration , advection , oceanography , environmental science , chemistry , geology , physics , geotechnical engineering , organic chemistry , thermodynamics
To investigate diel calcium carbonate (CaCO 3 ) dynamics in permeable coral reef sands, we measured pore‐water profiles and fluxes of oxygen (O 2 ), nutrients, pH, calcium (Ca 2+ ), and alkalinity (TA) across the sediment‐water interface in sands of different permeability at Heron Reef, Australia. Background flushing rates were high, most likely as a result of infaunal burrow irrigation, but flux chamber stirring enhanced pore‐water exchange. Light and pore‐water advection fueled high rates of benthic primary production and calcification in sunlit surface sediments. In the light, benthic photosynthesis and calcification induced surface minima in Ca 2+ and TA and peaks in pH and O 2 . Oxygen penetration depth in coarse sands decreased from ∼ 1.2 cm during the day to ∼ 0.6 cm at night. Total oxygen uptake (TOU) in dark chambers was three to fourteen times greater than diffusive uptake and showed a direct effect of pore‐water advection. Greater sediment oxygen consumption rates were observed in higher permeability sands. In the dark, TA release was not stimulated by increasing TOU because of a damping effect of pore‐water advection on metabolic CaCO 3 dissolution efficiency. On a daily basis, CaCO 3 undergoes net dissolution in Heron Reef sands. However, pore‐water advection can reverse the CaCO 3 budget and promote CaCO 3 preservation under the most energetic conditions.