Regulating Services of Bivalve Molluscs in the Context of the Carbon Cycle and Implications for Ecosystem Valuation

Abstract

The role of marine bivalves in the CO 2 cycle has been commonly evaluated as the balance between respiration, shell calcium carbonate sequestration, and CO 2 release during biogenic calcification; however, this individual-based approach neglects important ecosystem interactions that occur at the population level, e.g. the interaction with phytoplankton populations and benthic-pelagic coupling, which in turn can significantly alter the CO 2 cycle. Therefore, an ecosystem approach that accounts for the trophic interactions of bivalves, including the role of dissolved and particulate organic and inorganic carbon cycling, is needed to provide a rigorous assessment of the role of bivalves as a potential sink of CO 2. Conversely, the discussion about this potential role needs to be framed in the context of non-harvested vs. harvested populations, given that harvesting represents a net extraction of matter from the ocean. Accordingly, this chapter describes the main processes that affect CO 2 cycling and discuss the role of non-harvested and harvested bivalves in the context of sequestering carbon. A budget for deep-fjord waters is presented as a case study.

A biotechnological expansion of shellfish cultivation could permanently remove carbon dioxide from the atmosphere

“…If we assume that the shell represents 50% of the animal's mass, then the total shellfish-shell produced was 88 million tonnes over 8 years; which is an average of 11 million tonnes of shell per year. Filgueira et al (2019) arrive at a similar value for bivalve molluscs alone. I quote: "Taking into account the global annual production of cultured bivalves is ≈14 x10 6 tons, including clams, cockles, oysters, mussels and scallops (www.fao.org reporting 2015 data) and assuming an average contribution of shell to total body weight of 50% (general ballpark figure given that this varies greatly between species), shell represents a residue (potential byproduct) of ≈7 × 10 6 tons, of which 95% is calcium carbonate.…”

“…The rest derives from CO2 generated by the animal's food through the TCA cycle. The fractions derived from these two sources differ widely (McConnaughey & Gillikin, 2008;Filgueira et al, 2019). Knowing when calcification draws mainly on CO2 from food or depends on inorganic carbon from ambient air or water is a crucial consideration for studies of nutrition, ecology, conservation and cultivation but it is not relevant to this discussion.…”

“… Filgueira et al (2019) make the closest approach but they conclude that the "0.45 g CO2 sequestered by the shell of each cultured mussel in Norway is hardly significant taking into account that a regular car produces more than 100 g CO2 per km". Personally, I would expect more than one mussel in a serving; say, at least 20.…”

“…Remember, the CO2 is permanently sequestered, but you'll be hungry again the next day; and, presumably, so will your neighbours. Filgueira et al (2019) conclude "although this is far from solving a global problem, everything counts. In addition, it is important to re-emphasize that this comes at no cost or effort given that bivalves are cultured to produce food."…”

Perspectives on Bivalves Providing Regulating Services in Integrated Multi-Trophic Aquaculture

“…The use of bivalves in IMTA development might be characterized as being in its infancy, as bivalves are being studied for their ability to directly capture of organic particulates from farm sites and also in the larger scale of relative nutrient extraction at the bay level without specific requirements on proximity to a farm and nutritional connectivity (Chopin 2013). Other potential benefits provided by bivalves in IMTA are improved perception of sustainable production by the public (Yip et al 2017), extraction of pathogens and salmon lice from finfish aquaculture (Molloy et al 2011(Molloy et al , 2014Bartsch et al 2013;Webb et al 2013), their role in the carbon cycle with consequences for CO 2 sequestering and climate change ; see also Filgueira et al 2019) and new socio-economic approaches to motivate industry to adopt IMTA (Shi et al 2013;Hughes and Black 2016). .1 Farming mussels in association with salmon farms in the Bay of Fundy, (a) aerial shot of a salmon farm in the Bay of Fundy with 4 rafts of mussels on the down-stream end, (b) a mussel raft showing the arrangement of mussel lines hanging within an empty fish cage collar and the suspension system using floats, (c) close-up of the mussel lines showing the mussel socks hanging down from the top line that is supported by the buoys, (d) close-up of one of the mussel socks hanging from the top line on one of the rafts.…”