Sponge bioerosion accelerated by ocean acidification across species and latitudes?

Abstract

In many marine biogeographic realms, bioeroding sponges dominate the internal bioerosion of calcareous substrates such as mollusc beds and coral reef framework. They biochemically dissolve part of the carbonate and liberate so-called sponge chips, a process that is expected to be facilitated and accelerated in a more acidic environment inherent to the present global change. The bioerosion capacity of the demosponge Cliona celata Grant, 1826 in subfossil oyster shells was assessed via alkalinity anomaly technique based on 4 days of experimental exposure to three different levels of carbon dioxide partial pressure (pCO 2 ) at ambient temperature in the coldtemperate waters of Helgoland Island, North Sea. The rate of chemical bioerosion at present-day pCO 2 was quantified with 0.08-0.1 kg m -2 year -1 . Chemical bioerosion was positively correlated with increasing pCO 2 , with rates more than doubling at carbon dioxide levels predicted for the end of the twenty-first century, clearly confirming that C. celata bioerosion can be expected to be enhanced with progressing ocean acidification (OA). Together with previously published experimental evidence, the present results suggest that OA accelerates sponge bioerosion (1) across latitudes and biogeographic areas, (2) independent of sponge growth form, and (3) for species with or without photosymbionts alike. A general increase in sponge bioerosion with advancing OA can be expected to have a significant impact on global carbonate (re)cycling and may result in widespread negative effects, e.g. on the stability of wild and farmed shellfish populations, as well as calcareous framework builders in tropical and cold-water coral reef ecosystems.

Combined Effects of Experimental Acidification and Eutrophication on Reef Sponge Bioerosion Rates

“…Results regarding higher rates at increased pCO 2 are comparable to previous studies on other clionaid species (C. orientalis and C. celata) (Wisshak et al, 2012(Wisshak et al, , 2013(Wisshak et al, , 2014Fang et al, 2013a). Sponges and other borers are assumed to benefit from eutrophication (Holmes, 2000;Carballo et al, 2008).…”

“…Estimates of chemical and mechanical bioerosion for C. caribbaea are comparable to those calculated for C. orientalis under a range of CO 2 concentrations (Fang et al, 2013a;Wisshak et al, 2013Wisshak et al, , 2014. This is consistent with the membership of C. caribbaea to the Cliona viridis-complex (Schönberg, 2002).…”

“…Our chemical rates ranged from 0.06 to 0.15 mg cm −2 day −1 from present day to business-as-usual pCO 2 levels. Estimates by Fang et al (2013a) ranged from 0.08 to 0.3 mg cm −2 day −1 while rates by Wisshak et al (2014) ranged from 0.02 to 0.26 mg cm −2 day −1 . Mechanical rates from Fang ranged from 0.12 to 0.16 mg cm −2 day −1 whilst our results ranged from 0.23 to 0.5 mg cm −2 day −1 (in E1).…”

“…Although the negative effects of OA on production of CaCO 3 (calcification) by corals are widely documented (Gattuso et al, 1998;Kleypas and Langdon, 2006;Hoegh-Guldberg et al, 2007;Ries et al, 2009;Pandolfi et al, 2011;Dove et al, 2013), its impact on biologically induced carbonate dissolution and mechanical destruction have been understudied (Zundelevich et al, 2007;Fang et al, 2013a;Wisshak et al, 2014;Enochs et al, 2015;Schönberg et al, 2017) and has so far not been quantified in combination with eutrophication.…”

Effects of pCO2 on the interaction between an excavating sponge, Cliona varians, and a hermatypic coral, Porites furcata

“…Members of the 'Cliona viridis species complex' are known to be particularly efficient bioeroders, as this group of sponges harbor symbiotic zooxanthellae that both accelerate boring rates and necessitate direct spatial competition with corals for light (Hill 1996). Studies demonstrating that erosional processes are affected by decreasing pH (Duckworth and Peterson 2012) and increasing pCO 2 (Wisshak et al 2012;Fang et al 2013, Wisshak et al 2014) are important for understanding how future changes will affect substrate erosion; however, a direct evaluation of the spatial interactions and competitive outcomes occurring between these ecologically important species must also be undertaken.…”