World Oceans Day is celebrated this year on June 8 with the theme of Catalyzing Action for Our Ocean & Climate. Although the honorary day is June 8, the theme is multi-year. As the World Oceans Day website puts it: “We currently face one of the greatest threats ever to our blue planet and all its inhabitants: the climate crisis. It is all too clear that we need a healthy ocean for a healthy climate, and vice versa, and we need significantly stronger local, national, and international action from both government and corporate leaders. Now."
June is also the month when Maine Coast Sea Vegetables was born 53 years ago (the exact day is lost with the tides). It seems appropriate, then, to consider how seaweed is affected by the climate crisis, and how in turn seaweed affects climate and the oceans. Most importantly, this is a time to reflect upon what action we can take as individuals and communities to address the climate crisis. Can seaweed be part of the solution?
Small individual actions collectively add up to big impacts. Something as simple as idling a vehicle adds tons of CO2 to the atmosphere when done by millions of people. If we all start with small actions, such as not idling our vehicles, larger actions, such as switching to electric vehicles, seem more possible. Support renewable energy. Drive less and buy less stuff. Use less plastic. Install a heat pump in your home. Each action we take as individuals influences other people in a positive way to collectively bring about positive change.
What we choose to eat can also make a difference, good or bad. Every pound of beef we consume comes with a larger carbon footprint than a pound of poultry, Seafood and vegetarian diets have even smaller carbon impacts. This is one reason why incorporating seaweed into our diets can be part of the solution.
Scientists report that since 2005, the Gulf of Maine (GoM) has experienced some of the rapidest warming observed in any of the world’s oceans. Andrew Pershing, who previously served as chief scientific officer for the Gulf of Maine Research Institute and is now VP for Science at the World Meteorological Organization, has written several influential articles on this topic. In a 2021 review article authored by Dr. Pershing and other scientists, they describe the GoM as a distinctive subarctic ecosystem despite being well south of the subarctic region. As anyone who has ever plunged into the ocean from Acadia’s Sand Beach can attest, the GoM can be shockingly cold even in August!
Unfortunately, this distinction is under threat as the ocean currents feeding the GoM and responsible for its famously cold temperatures shift and become warmer. As this occurs, cold water species such as the northern shrimp (Pandalus borealis), Atlantic cod (Gadus morhua), and Calanus copepods move north or out of the GoM, while warmer water species such as the black sea bass (Centropristis striata), Atlantic mackerel (Scomber scombrus), and longfin squid (Doryteuthis pealeii) occur in greater numbers and spend more time there. Even Maine’s iconic lobster fishery could move further north. Lobsters have flourished as the GoM has warmed, but when the temperature increases beyond about 20.6°C (69°F) they become stressed and seek colder water. Recruitment of lobster larvae could also suffer.
Warming oceans also affect seaweed distribution and abundance. Over the past 20 years, the GoM south of the Penobscot River has shifted from kelp dominated communities to turf macroalgae habitats. Vertically growing brown kelp species such as sugar kelp (Saccharina latissima), winged kelp (Alaria esculenta), and oarweed (Laminaria digitata) are being replaced by turf-like red species such as Polysiphonia spp. and Neosiphonia spp. Dasysiphonia japonica, one of at least 15 invasive species now occurring in the GoM, is rapidly moving northward, along with at least two native warm-water red algae (Agardhiella subulata and Gelidium crinale).
A close-up view of the red filamentous turf algae that is proliferating in the Gulf of Maine. Courtesy of Shane Farrell
Similar changes are observed in many of the world’s other oceans, often having profound effects on marine ecosystems. When kelp forests change over to turf algae habitats, species abundance and richness can be lost. For now, these changes have not much impacted northern areas where dulse, sugar kelp, and Alaria are harvested, while rockweed and bladderwrack, the main seaweeds harvested from the southern GoM, thrive in warmer water. However, by 2100 it's projected that under a business-as-usual scenario where little is done to reduce carbon emissions, many of the species MCSV sells will have moved north and become less abundant in the GoM.
Earth’s atmosphere now contains more CO2 than at any time in the past 740,000 years, and at the present trajectory of human emissions will soon exceed anything experienced in tens of millions of years. Oceans, which cover about 70% of earth, have so far buffered the planet from the worst effects of this dramatic change in atmospheric composition. They absorb about 30% of the CO2 released by human emissions and 95% of the excess heat generated by those emissions. Ultimately, though, every system has its limits, and we are now seeing signs that the oceans are reaching those limits.
Warmer water holds less CO2 than colder water, so as the oceans warm, they can’t absorb as much CO2. CO2 is also acidic. Surface ocean waters have an average pH of 8.1, which is on the alkaline side of the scale. However, at the current rate of human CO2 emissions, ocean pH could drop to 7.8 by the turn of the century. A pH of 7.8 is still alkaline and a drop of 0.2 may not seem like much, but the pH scale is logarithmic and a decline of 0.1 pH units represents approximately a 30% increase in acidity. Corals and shellfish that make skeletons and hard shells by combining calcium and carbonate from seawater are already being impacted.
When carbon is absorbed by seawater it becomes part of a complex marine carbon cycle. Some becomes trapped in cold water and sinks deep to the ocean floor to be locked away for millennia, while some is incorporated into marine life. Carbon is foundational to life and makes up about 45-50% of the dry biomass of every life form. Phytoplankton, at the base of the marine food web, are carbon cycling factories, converting it into sugars and other molecules, including essential marine lipids, through photosynthesis. Phytoplankton get eaten by other organisms and the carbon and nutrients they contain cycle through the food web. In the process, some of the assimilated carbon is excreted or respired, and some makes its way back into the atmosphere. Like a living creature, the ocean both absorbs and emits carbon. On balance, though, the oceans absorb far more carbon than they emit.
Photosynthetic marine plants and ecosystems, such as mangrove forests, seagrasses, tidal marshes, and kelp beds also capture significant carbon. Seaweed’s part in the marine carbon cycle in particular has attracted much attention as of late as a potential solution to the problem of human carbon emissions. However, the science on this topic remains unclear. Seaweed enthusiasts and popular media often interchangeably use terms like ‘carbon sequestration,’ ‘carbon storage,’ ‘carbon assimilation,’ ‘carbon fixation,’ and ‘carbon burial’ with apparently little regard for meaning and implication. Seaweed does all these things but its carbon sequestration potential, defined as the rate of removal of atmospheric CO2 for >100 years (UNFCC, 2022), is not well understood.
Lack of certainty has not stopped companies from proposing to grow and then sink kelp on a gigantic scale as a climate solution. These companies hope to profit from the carbon credit market. The idea is that companies could offset their carbon emissions by purchasing credits from companies that capture and store carbon emissions. Schemes range from giant CO2 sucking machines to reforestation to growing kelp. The theoretical carbon removal potential of kelp was calculated by the Energy Futures Initiative as being one billion to ten billion tons of carbon dioxide per year. However, as MIT Technology Review put it in a 2021 article authored by James Temple, Companies hoping to grow carbon-sucking kelp may be rushing ahead of the science.
Human capacity for hope and innovation fortunately knows no bounds, but the idea of growing vast tonnages of kelp and then sinking it to the ocean bottom gives many people pause. The ecological impact of such an endeavor is unknown and its logistics raise many questions. Where will it be grown? What about the structures, such as the lines and thousands of buoys, needed to grow all that kelp? Seaweed doesn't necessarily sink all that easily. How do we ensure it actually sinks and how do we measure the proportion that does not sink, decomposes, or gets eaten by something else? In order for carbon credits to achieve their aim, the carbon has to be sequestered, or locked away, for at least 100 years. When kelp decomposes or gets eaten, the carbon it contains gets released back into the atmosphere.
A better climate solution might be to use seaweed, not sink it. This may seem counter-intuitive at first. Whenever we use seaweed, whether by eating it or by using it as animal feed, as medicine, for fertilizer, or as a material or ingredient in thousands of products, in most cases the carbon it contains is released into the atmosphere well before 100 years has gone by. Wouldn’t it be better to leave seaweed in the ocean, where it’s doing the most good?
Obviously, as a company selling wild-harvested sea vegetables, Maine Coast Sea Vegetables doesn’t share that view, and fortunately, we’re not alone. There is plenty of evidence that using seaweed as food, medicine, and other things is good for the planet and good for the ocean. As a crop, kelp and other seaweeds require far fewer inputs than conventional terrestrial crops, while also benefiting the sea. When we eat sea vegetables, we take pressure off our already over-loaded terrestrial farming systems, some of which have large carbon footprints and almost all of which require dwindling fresh water resources along with fossil fuel fertilizers and other chemicals. Sea vegetables, on the other hand, have a neutral to negative carbon footprint, require little to no fresh water, and are not supplemented with fertilizer, pesticides, or herbicides. This is true for both wild-harvested and farmed sea vegetables.
In addition, numerous studies show that macroalgae beds help maintain or increase local pH values, thus countering the acidifying effect of CO2 on seawater. Of course, when seaweed is harvested that benefit diminishes, but the premise of encouraging people to include wild and farmed sea vegetables in their diet is still sound. This is because increased demand for sea vegetables will encourage more farmers to grow it, and more seaweed farms should lead to healthier oceans.
Seaweed is valuable as much more than food, of course, and just about every use is good for the earth and its’ oceans. It can be made into a biodegradable alternative to some petroplastics, for example, which as discussed in a previous blog post are a major threat to the oceans. Seaweed is also harvested around the world for agricultural applications, including here in Maine, where it has a long heritage of being used as fertilizer. Scientific advancements have made such use more targeted and efficient by developing seaweed extracts with plant biostimulant properties that increase crop yield and vigor, while reducing the need for fossil fuel fertilizers. According to the Union of Concerned Scientists, fertilizer manufacturing requires immense energy inputs, and producing the ammonia needed for fertilizer generates more CO2 than any other industrial chemical reaction. Anything that can lessen the use of fossil fuel derived fertilizers is a good thing.
As with any natural resource, seaweed must be sustainably harvested by humans without harming the environment. Sustainability is a core intention of the Maine Coast Sea Vegetable mission and one shared by our fellow members of the Maine Seaweed Council. Seaweed has enormous regenerative capacity and many species grow back so long as the entire plant isn't harvested. As we celebrate World Ocean’s Day, let us also celebrate seaweed and promote its use. Incorporating more seaweed into our daily lives, whether as whole food, seasoning, tea, or soap is good for the planet and the sea. In this simple fashion we can all act on behalf of our climate and the oceans.
