A global compilation of coccolithophore calcification rates

Abstract

Abstract. The biological production of calcium carbonate (CaCO3), a process termed calcification, is a key term in the marine carbon cycle. A major planktonic group responsible for such pelagic CaCO3 production (CP) are the coccolithophores, single-celled haptophytes that inhabit the euphotic zone of the ocean. Satellite-based estimates of areal CP are limited to open-ocean waters, with current algorithms utilising the unique optical properties of the cosmopolitan bloom-forming species Emiliania huxleyi, whereas little understanding of the optical properties and environmental responses by species other than E. huxleyi are currently available to parameterise algorithms or models. To aid future areal estimations and validate future modelling efforts we have constructed a database of 2765 CP measurements, the majority of which were measured using 12 to 24 h incorporation of radioactive carbon (14C) into acid-labile inorganic carbon (CaCO3). We present data collated from over 30 studies covering the period from 1991 to 2015, sampling the Atlantic, Pacific, Indian, Arctic and Southern oceans. Globally, CP in surface waters (

Coccolithophore Growth and Calcification in an Acidified Ocean: Insights From Community Earth System Model Simulations

“…For instance, while satellite‐derived PIC provides a proxy for coccolithophore abundance, errors can arise from atmospheric correction and inclusion of other suspended minerals (see Balch et al, ). We also compare our results to the MAREDAT data set (MARine Ecosystem DATa; Figures a–c; Buitenhuis et al, ; O'Brien et al, ) and a recent global compilation of coccolithophore calcification rates (Figures d–e; Daniels et al, ). The MAREDAT data compilation, based on ∼11,000 individual field observations (spanning a time period of 1929 to 2008), derives monthly, depth‐specific estimates of total coccolithophore biomass at various points in the ocean.…”

“…The Daniels et al calcification data set includes 2765 field calcification measurements spanning a time period from 1991 to 2015. Major gaps in geographical coverage exist in both the Daniels et al () data set (e.g., western Pacific) and the MAREDAT data set (e.g., Southern Ocean). Furthermore, coccolithophore blooms are spatially variable from year to year (Hopkins et al, ), and both of these data sets are highly dependent on when calcification rates were recorded in situ.…”

“…We compare the MAREDAT and Daniels et al () observational data sets to model output during the growing season (June‐July‐August means in the Northern Hemisphere and December‐January‐February means in the Southern Hemisphere) at various depth intervals (maps divided into N/S Hemispheres by a black line to separate June‐July‐August/December‐January‐February means of data; Figure ). The MAREDAT observations are plotted for only the growing season months for each hemisphere, while all the calcification observations are included due to a known growing season bias in the data set (Daniels et al, ). In most regions modeled coccolithophore biomass is on the same order of magnitude as shown in MAREDAT.…”

“…In CESM‐cocco the coccolithophore PFT is the only source of CaCO 3 in the upper ocean. Observation‐based calcification estimates span an order of magnitude, ranging from 0.5 to 2.4 Pg C in CaCO 3 per year (Figure a; Balch et al, ; Daniels et al, ; Feely et al, ; Hopkins & Balch, ; Iglesias‐Rodriguez et al, ; Lee, ; Marañón et al, ; Milliman, ; Sarmiento et al, ; Smith & Mackenzie, ). CESM‐cocco estimates global upper ocean (top 150 m) calcification at present‐day CO 2 concentration to be ∼1.4 Pg C/year, falling squarely within this range (see turquoise bar in Figure ) and coinciding well with a recent satellite derived estimate of 1.42 Pg C/year by Hopkins and Balch ().…”

“…All values are in units of Pg C/year. References for observation‐based estimates are as follows: field calcification extrapolated (Marañón et al, ), Meta‐analysis (Smith & Mackenzie, ), satellite‐derived calcification 2007 (Balch et al, ), sediment traps (Iglesias‐Rodriguez et al, ; Milliman et al, ), alkalinity model (Sarmiento et al, ; Lee, ), alkalinity observations, and modeling (Feely et al, ), global calcification data set (Daniels et al, ), and new satellite derived calcification (Hopkins & Balch, ). (b) Mean calcification in the surface ocean (0–10 m) for various marine biomes (shown on map, with colors corresponding to colored dots next to biome names; Fay & McKinley, ); observations from Hopkins and Balch (; gray) are compared to CESM‐cocco calcification (turquoise).…”