How calorie-rich food could help marine calcifiers in a CO ₂ -rich future

Abstract

Increasing carbon emissions not only enrich oceans with CO 2 but also make them more acidic. This acidifying process has caused considerable concern because laboratory studies show that ocean acidification impairs calcification (or shell building) and survival of calcifiers by the end of this century. Whether this impairment in shell building also occurs in natural communities remains largely unexplored, but requires re-examination because of the recent counterintuitive finding that populations of calcifiers can be boosted by CO 2 enrichment. Using natural CO 2 vents, we found that ocean acidification resulted in the production of thicker, more crystalline and more mechanically resilient shells of a herbivorous gastropod, which was associated with the consumption of energy-enriched food (i.e. algae). This discovery suggests that boosted energy transfer may not only compensate for the energetic burden of ocean acidification but also enable calcifiers to build energetically costly shells that are robust to acidified conditions. We unlock a possible mechanism underlying the persistence of calcifiers in acidifying oceans.

Calcifiers can Adjust Shell Building at the Nanoscale to Resist Ocean Acidification

“…[ 19 ] Indeed, shell organic matrix (e.g., some proteins) can help stabilize amorphous calcium carbonate (i.e., precursor of crystalline calcium carbonate) and hence facilitate shell building or shell repair so that less porous shells can be produced under ocean acidification. [ 20,21 ] Since production of shell organic matrix is energy‐demanding, [ 22 ] the ability of the calcifying snails to construct less porous shells may be indirectly mediated by the consumption of energy‐enriched food under future pH conditions, [ 7 ] which in turn increases the energy budget to improve the shell‐building process. [ 23 ] At the nanoscale, we discovered that calcifiers could adjust the nanostructure of shells in response to the altered environmental pH conditions.…”

“…The method used to measure the mechanical resilience of shells was described in a previous study. [ 7 ] Briefly, the hardness ( H ) and elastic modulus ( E ) of shells were determined by nanoindentation (IBIS, M/S Fisher‐Cripps Laboratory, Australia) using a diamond Berkovich tip. Load‐controlled indentation with a maximum load of 50 mN was performed on the nacreous layer of polished shell surface of the outer lip.…”

“…Whilst these concerns have been derived from careful laboratory research on unadapted individuals, there is growing evidence from natural environments revealing that some calcifiers appear to resist the corrosive effect of acidified seawater on their shells. [ 5–7 ] A key challenge, therefore, is to understand the effects of ocean acidification in natural environments, which are subject to ecological and evolutionary processes that may buffer or reverse the short‐term negative effects of ocean acidification on calcifiers previously documented in laboratory experiments. [ 2,3 ] Studying calcifiers that have multiple generations living in naturally CO 2 ‐acidified environments offers a unique opportunity to incorporate this complexity into observations about the adjustability of shell building to ocean acidification.…”

Molecular mechanisms of biomineralization in marine invertebrates

“…Experiments have shown that unlimited food supplies help molluscs to overcome the increased energetic costs associated with changing conditions, and this will certainly be true in other phyla (Sanders et al, 2013;MacKenzie et al, 2014). Increased food consumption will be needed to fuel both higher metabolic rates in warming seas and increased costs of skeletal maintenance, if adaptation requires the increased production of proteinaceaous components (Palmer, 1992;Leung et al, 2019;Telesca et al, 2018Telesca et al, , 2019. These increased costs could also result in the reallocation of energy budgets (energetic trade-offs), which may affect future performance, including reproductive output (e.g.…”

How the Pacific Oyster Responds to Ocean Acidification: Development and Application of a Meta-Analysis Based Adverse Outcome Pathway

“…Indirect effects can, however, alter the direct effect of ocean acidification on shell structure. That is, where energy-rich food is available under ocean acidification, calcifiers can build shells that are thicker, more crystalline, and more mechanically resilient (Leung et al, 2019). Where such resources are not available, these responses not possible, and shells impaired, the increased mortality at the individual level can then lead to a decline in the size of the overall population.…”