In:
Biogeosciences, Copernicus GmbH, Vol. 15, No. 8 ( 2018-04-23), p. 2467-2480
Abstract:
Abstract. Constraining coral reef metabolism and carbon chemistry dynamics are
fundamental for understanding and predicting reef vulnerability to rising
coastal CO2 concentrations and decreasing seawater pH. However, few
studies exist along reefs occupying densely inhabited shorelines with known
input from land-based sources of pollution. The shallow coral reefs off
Kahekili, West Maui, are exposed to nutrient-enriched, low-pH submarine
groundwater discharge (SGD) and are particularly vulnerable to the
compounding stressors from land-based sources of pollution and lower
seawater pH. To constrain the carbonate chemistry system, nutrients and
carbonate chemistry were measured along the Kahekili reef flat every 4 h
over a 6-day sampling period in March 2016. Abiotic process – primarily SGD
fluxes – controlled the carbonate chemistry adjacent to the primary SGD vent
site, with nutrient-laden freshwater decreasing pH levels and favoring
undersaturated aragonite saturation (Ωarag) conditions. In
contrast, diurnal variability in the carbonate chemistry at other sites
along the reef flat was driven by reef community metabolism. Superimposed on
the diurnal signal was a transition during the second sampling period to a
surplus of total alkalinity (TA) and dissolved inorganic carbon (DIC)
compared to ocean endmember TA and DIC measurements. A shift from positive
net community production and positive net community calcification to
negative net community production and negative net community calcification
was identified. This transition occurred during a period of increased
SGD-driven nutrient loading, lower wave height, and reduced current speeds.
This detailed study of carbon chemistry dynamics highlights the need to
incorporate local effects of nearshore oceanographic processes into
predictions of coral reef vulnerability and resilience.
Type of Medium:
Online Resource
ISSN:
1726-4189
DOI:
10.5194/bg-15-2467-2018
DOI:
10.5194/bg-15-2467-2018-supplement
Language:
English
Publisher:
Copernicus GmbH
Publication Date:
2018
detail.hit.zdb_id:
2158181-2
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