World Aquaculture Magazine - June 2021

WWW.WA S .ORG • WORLD AQUACULTURE • JUNE 2021 31 is important to compare prices that can be obtained for different uses of valuable seaweeds. The present carbon tax scheme in Canada would offer CA$ 1.20/MT fresh weight (FW) of seaweeds (Chopin 2021b). Wild seaweed bed harvesters can get at least CA$ 60.64/MT FW. Seaweed farmers can access markets with prices from less than CA$ 0.127 to more than CA$ 127.03/kg FW for different applications. What would be the incentive for seaweed harvesters/farmers to harvest/grow seaweeds, then sell them at a ridiculous low price, only to see them sunk to the deep ocean floor, when they could sell them at much higher prices for other applications? Moreover, at the rate of progression envisioned by the present government of Canada for the carbon tax, it would take more than 108 years before the carbon tax matches one of the most inexpensive prices paid for seaweeds in Canada. Another point is, how, when and where would this massive seaweed biomass be stored? When asked of some of the seaweed zealots, this methodology remains evasively explained. Furthermore, the impact(s) and role(s) this biomass will have in deep ocean ecosystems — sinking a buoyant seaweed mass to the mesopelagic zone and even deeper and its associated ecosystem impacts —are simply unknown. (Apply the Precautionary Principle again!) An argument being floated around is that e-DNA studies are showing the presence of DNA of macroalgal origin “a little everywhere.” That may be, but this does not show accumulations of large amounts of seaweeds at the bottom of the ocean. We presume that, like any organic matter when decaying, pieces of seaweeds will sooner or later be mineralized and organic forms of carbon, nitrogen, phosphorus, etc., returned to their inorganic forms and be available again to the general cycle of life. This means that we are back to talking about transient sequestration and remembering once again the famous sentence of Antoine-Laurent de Lavoisier: “Nothing is lost, nothing is created, everything is transformed.” The bottom line is that seaweeds do not seem to be suitable candidates for large-scale permanent carbon sequestration at geological time scales. RealityCheck#4: Cultivating seaweeds at a large scale all around the planet. About 71 percent of the earth’s surface is covered with water, and if we consider nutrient concentrations and temperatures compatible with seaweed cultivation, we could come up with figures of “x” km 2 for cultivation to grow “y” MT of seaweeds, which would exceed many times present world seaweed aquaculture production. Based on decades of observing the seaweed world, we are of the opinion that decisions to grow seaweeds will be dictated mostly by societal, economic and regulatory reasons, as well as political will (or the lack of it), much more so than by models fed by academics with abiotic geospatial physico-chemical data. Like in the 1970s, a yet-to-be-proven technology-driven approach to market development is being proposed, rather than market-driven technology scaling. Scaling is a vital issue for the nascent seaweed industry in new aquaculture geographies. Seaweed aquaculture, like the aquaculture of shellfish and other invertebrates, is generally viewed positively by many in the new aquaculture geographies, particularly by the younger generation entering this sector, who considers it as sustainable and having positive impacts on the environment. This offers an opportunity to accelerate a new social contract for aquaculture (Costa-Pierce 2010). However, this scaling needs to be gradual for the seaweed biomass to be absorbed appropriately and sustainably by the seafood markets and those of other seaweed- derived applications. Another issue with these very ambitious projects is that the proposed seaweed species are often not endemic to the regions generously drawn on maps. Not only is there no guarantee that they will grow in these locations over very large latitudinal scales but the concept of introducing non-endemic species seems of no or little concern to the proponents. RealityCheck#5: Ifwe farm“x”km 2 of seaweeds, usually expressedas an equivalent surface area of a small country, wewill be able to feed theworld’s population. Large amounts of seaweed cultivation area cannot be continuous. Marine spatial planning is more necessary than ever to accommodate competing activities (e.g., navigable passages, channels, transit for other goods, communications, wind farms, fisheries, other types of aquaculture, recreational activities, etc.). In another respect, is the world population really ready to secure all its proteins, carbohydrates and lipids (not much) from seaweeds/ sea vegetables? We hope that a dietary shift towards more seafood consumption will occur but this will not happen overnight (seaweeds have been the next superfood for quite a while). Moreover, a balanced and nutritious diet comes from a diversity of food sources. RealityCheck#6:Growing toomany extractive species and removing toomany nutrients fromecosystems couldalso be aproblem. At the present time, the aquaculture of extractive species, like seaweeds and invertebrates, seems to have the wind in its sails, to be the “in” fad of the day. Non-governmental organizations (NGOs) and celebrities seems to have developed a sudden love for seaweeds and sea cucumbers like never before. A fewmonths ago, at a virtual conference from India, a speaker fromVietnammentioned that there was a need to balance shrimp farming by more seaweed farming. A speaker from the Philippines mentioned that in some regions the cultivation of seaweeds was very intensive, leading to the consideration of developing a schedule of fallowing periods, every year or two, to let the bays replenish their nutrient levels. We are, frankly, not surprised and thought it was a question of time before such a situation was acknowledged. In Madagascar, the new poster children of “benign aquaculture,” touted by several NGOs, are sea cucumbers. However, when looking at pictures of the densities of these creatures, one can only wonder how soon it will be before these deposit feeders will not have much to graze from the sediments and will need provision of supplemental feeds. The latest fashion is to talk about restorative or regenerative aquaculture. While we wonder what needs to be regenerated, and to what state (was there ever a climax state, or nirvana, of perfect nutrient balance and habitat for all without flux?), we also wonder if there will not be a point when regenerative aquaculture will need to be regenerated, due to a large imbalance of organisms at different trophic levels being anthropogenically created? Certainly, there is a point when too much of a good thing (yes, including seaweeds and invertebrates) can be harmful. ( C O N T I N U E D O N P A G E 3 2 )