Reviews and syntheses: Calculating the global contribution of coralline algae to total carbon burial

Abstract

Abstract. The ongoing increase in anthropogenic carbon dioxide (CO2) emissions is changing the global marine environment and is causing warming and acidification of the oceans. Reduction of CO2 to a sustainable level is required to avoid further marine change. Many studies investigate the potential of marine carbon sinks (e.g. seagrass) to mitigate anthropogenic emissions, however, information on storage by coralline algae and the beds they create is scant. Calcifying photosynthetic organisms, including coralline algae, can act as a CO2 sink via photosynthesis and CaCO3 dissolution and act as a CO2 source during respiration and CaCO3 production on short-term timescales. Long-term carbon storage potential might come from the accumulation of coralline algae deposits over geological timescales. Here, the carbon storage potential of coralline algae is assessed using meta-analysis of their global organic and inorganic carbon production and the processes involved in this metabolism. Net organic and inorganic production were estimated at 330 g C m−2 yr−1 and 900 g CaCO3 m−2 yr−1 respectively giving global organic/inorganic C production of 0.7/1.8 × 109 t C yr−1. Calcium carbonate production by free-living/crustose coralline algae (CCA) corresponded to a sediment accretion of 70/450 mm kyr−1. Using this potential carbon storage for coralline algae, the global production of free-living algae/CCA was 0.4/1.2 × 109 t C yr−1 suggesting a total potential carbon sink of 1.6 × 109 tonnes per year. Coralline algae therefore have production rates similar to mangroves, salt marshes and seagrasses representing an as yet unquantified but significant carbon store, however, further empirical investigations are needed to determine the dynamics and stability of that store.

The regulation of coralline algal physiology, an in situ study of <i>Corallina officinalis</i> (Corallinales, Rhodophyta)

“…For example, Martin et al (2006) reported a seasonal range of 0.68 to 1.48 µmol C (g DW) −1 h −1 for the maerl-forming Lithothamnion corallioides off NW France. Currently, the contribution of coralline algae to global carbon cycles is not well constrained, particularly that of geniculate turfing species (El Haïkali et al, 2004;Van der Heijden and Kamenos, 2015). Given their comparatively high production identified here, our data indicate that geniculate corallines likely play a significant role in coastal carbon cycling, despite their presumably reduced overall benthic coverage compared to maerl-forming or crustose coralline algal species.…”

“…C. officinalis NP (assessed from daytime light treatment incubations) and R (assessed from daytime dark treatment and all night-time incubations) were calculated from the difference between initial and final incubation DIC concentrations as follows: where NP and R DAY/NIGHT are net production and respiration during the day or night, respectively (µmol DIC (g DW) −1 h −1 ); DIC is the change in dissolved inorganic carbon concentration during the incubation (µmol DIC kg −1 seawater); v is the incubation chamber volume (L); dw is the dry weight of C. officinalis incubated (g); t is the incubation time (h); and NG is the net calcification rate (µmol CaCO 3 (g DW) −1 h −1 ). NG was estimated using the alkalinity anomaly technique (Smith and Key, 1975;Chisholm and Gattuuso, 1991), whereby TA decreases by 2 equivalents for each mol of CaCO 3 precipitated. Light calcification (assessed from daytime light treatment incubations) and dark calcification (assessed from daytime dark and all night-time incubations) were thus calculated as follows:…”

“…It is therefore critical to constrain Corallina ecophysiology in relation to current environmental variability in order to aid projections under future climate scenarios (Nelson, 2009;Koch et al, 2013;Brodie et al, 2014;Hofmann and Bischof, 2014). It is also important to understand the present-day role of these dominant community members in coastal carbon cycles and how this may change into the future (van der Heijden and Kamenos, 2015).…”

Understanding the margin squeeze: Differentiation in fitness‐related traits between central and trailing edge populations of Corallina officinalis

“…One of the major groups effected by climate change is calcifying benthic macroalgae (Kroeker et al, 2013). They function as important ecosystem engineers and play a crucial role as an essential structural element in the majority of rocky coastal zones (Benedetti-Cecchi, 2006;Dayton, 1972;van der Heijden & Kamenos, 2015;Johansen, 1981;Jones, Lawton, & Shachak, 1994;Kelaher, Chapman, & Underwood, 2001;Nelson, 2009;Noël, Hawkins, Jenkins, & Thompson, 2009). They function as important ecosystem engineers and play a crucial role as an essential structural element in the majority of rocky coastal zones (Benedetti-Cecchi, 2006;Dayton, 1972;van der Heijden & Kamenos, 2015;Johansen, 1981;Jones, Lawton, & Shachak, 1994;Kelaher, Chapman, & Underwood, 2001;Nelson, 2009;Noël, Hawkins, Jenkins, & Thompson, 2009).…”

Scotland's forgotten carbon: a national assessment of mid-latitude fjord sedimentary carbon stocks

“…The quantification of C in fjordic sediments was identified as a priority by Syvitski et al (1987), but little progress has been made towards this goal until recently. Our work presented here utilises and extends the joint geochemistry and geophysical methodology developed by Smeaton et al (2016) by applying it to a number of mid-latitude fjords.…”