title: Baseline Assessment of Net Calcium Carbonate Accretion Rates on U.S. Pacific Reefs.
abstract: This paper presents a comprehensive quantitative baseline assessment of in situ net calcium carbonate accretion rates (g CaCO3 cm(-2) yr(-1)) of early successional recruitment communities on Calcification Accretion Unit (CAU) plates deployed on coral reefs at 78 discrete sites, across 11 islands in the central and south Pacific Oceans. Accretion rates varied substantially within and between islands, reef zones, levels of wave exposure, and island geomorphology. For forereef sites, mean accretion rates were the highest at Rose Atoll, Jarvis, and Swains Islands, and the lowest at Johnston Atoll and Tutuila. A comparison between reef zones showed higher accretion rates on forereefs compared to lagoon sites; mean accretion rates were also higher on windward than leeward sites but only for a subset of islands. High levels of spatial variability in net carbonate accretion rates reported herein draw attention to the heterogeneity of the community assemblages. Percent cover of key early successional taxa on CAU plates did not reflect that of the mature communities present on surrounding benthos, possibly due to the short deployment period (2 years) of the experimental units. Yet, net CaCO3 accretion rates were positively correlated with crustose coralline algae (CCA) percent cover on the surrounding benthos and on the CAU plates, which on average represented >70% of the accreted material. For foreeefs and lagoon sites combined CaCO3 accretion rates were statistically correlated with total alkalinity and Chlorophyll-a; a GAM analysis indicated that SiOH and Halimeda were the best predictor variables of accretion rates on lagoon sites, and total alkalinity and Chlorophyll-a for forereef sites, demonstrating the utility of CAUs as a tool to monitor changes in reef accretion rates as they relate to ocean acidification. This study underscores the pivotal role CCA play as a key benthic component and supporting actively calcifying reefs; high Mg-calcite exoskeletons makes CCA extremely susceptible changes in ocean water pH, emphasizing the far-reaching threat that ocean acidification poses to the ecological function and persistence of coral reefs worldwide.
authors.affiliation: Joint Institute for Marine and Atmospheric Research, University of Hawaii, Honolulu, Hawaii, 96818, United States of America.
authors.forename: Bernardo
authors.initials: B
authors.lastname: Vargas-Ángel
authors.affiliation: 2525 Date St. Apt. 3101, Honolulu, Hawaii, 96826-5420, United States of America.
authors.forename: Cristi L
authors.initials: CL
authors.lastname: Richards
authors.affiliation: Ocean Associates, 1846 Wasp Blvd. Bldg., # 176, Honolulu, Hawaii, 96818, United States of America.
authors.forename: Peter S
authors.initials: PS
authors.lastname: Vroom
authors.affiliation: Bigelow Laboratory for Ocean Sciences, 60 Bigelow Dr., East Boothbay, Maine, 04544, United States of America.
authors.forename: Nichole N
authors.initials: NN
authors.lastname: Price
authors.affiliation: University of Guam Marine Laboratory, Mangilao, Guam, 96913, United States of America.
authors.forename: Tom
authors.initials: T
authors.lastname: Schils
authors.affiliation: Joint Institute for Marine and Atmospheric Research, University of Hawaii, Honolulu, Hawaii, 96818, United States of America.
authors.forename: Charles W
authors.initials: CW
authors.lastname: Young
authors.affiliation: Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Dr., La Jolla, California, 92093, United States of America.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Smith
authors.affiliation: Scripps Institution of Oceanography, University of California San Diego, 9500 Gilman Dr., La Jolla, California, 92093, United States of America.
authors.forename: Maggie D
authors.initials: MD
authors.lastname: Johnson
authors.affiliation: NOAA Pacific Islands Fisheries Science Center, Coral Reef Ecosystem Division, 1846 Wasp Blvd. Bldg. # 176, Honolulu, Hawaii, 96818, United States of America.
authors.forename: Russell E
authors.initials: RE
authors.lastname: Brainard
mesh_terms: D000818:Animals; D037421:Anthozoa / Q000378:metabolism*; D002113:Calcification, Physiologic / Q000502:physiology*; D002119:Calcium Carbonate / Q000378:metabolism*; D002254:Carbonates / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D057894:Coral Reefs; D062312:Islands; D010140:Pacific Ocean; D012623:Seawater
chemical_list: D002254:Carbonates; D002734:Chlorophyll; D002119:Calcium Carbonate; D000077194:Chlorophyll A