One-and-a-half degrees doesn’t sound like much.
But when it comes to climate change projections, 1.5 degrees C above pre-industrial global temperatures is considered the point of no return — when unseasonable heat, droughts, wildfire and marine heat waves become regular aspects of runaway, feedback-looping climate change.
In climate change, small changes can have a big impact.
In the oceans, as in climate and life, little things also make an outsized difference.
Made up of small marine organisms that drift with the currents, phytoplankton (photosynthesizing algae), zooplankton (small animals), and bacterioplankton (microbes that degrade organic matter) are the basis of the ocean food chain.
Phytoplankton are also the lungs of the ocean, producing about half the world’s oxygen. The organisms’ sheer numbers produce and release oxygen into the atmosphere and transport about nine trillion kilograms of carbon from the atmosphere to the depths of the ocean every year.
Research suggests that rapid ocean warming could force tropical plankton to move toward the cooler poles, pushing aside plankton species native to those latitudes. This could overturn marine ecosystems throughout the oceans, and cause plankton blooms and die-off zones where insufficient oxygen in the water suffocates marine critters.
Small things matter.
Recent research published in the journal Functional Ecology of the British Ecological Society shows that most of the world’s ocean plankton could cross a threshold under climate change where instead of soaking up carbon dioxide, they start doing the opposite. That’s because of how warming affects their metabolism.
Because carbon dioxide is a greenhouse gas, that in turn could drive up temperatures further — a positive feedback loop that could lead to runaway change, where small amounts of warming have their own outsized impact.
Among the zooplankton, krill are an important food source for many marine animals. Humpback, grey and other baleen whales feed on them, as do ocean-going salmon. This makes the small, shrimp-like animals important also for the southern resident killer whales that feed on 91原创 salmon in our waters.
In B.C., krill are fished in large quantities as a feed supplement for both fish farms and aquariums.
Although small, krill are so numerous, they, too, can influence atmospheric carbon levels. One 2019 study found that krill can remove up to 12 billion tonnes of carbon from the Earth’s atmosphere every year. They do this by eating phytoplankton and pooping out carbon-rich pellets that sink to the seafloor.
Small things matter.
It’s not yet certain what climate change will mean for krill, but it’s believed that the loss of sea ice, marine warming and ocean acidification will reduce krill growth, development and hatchling rates, dampening the carbon-stowing capacity of these tiny animals.
Another form of zooplankton, pteropods, also known as “sea butterflies” or sea snails, live in the ocean all over the world. Living near the ocean’s surface and growing to the size of a pea, pteropods are eaten by everything from krill to whales and juvenile 91原创 salmon.
For the past decade, the animal has been thought to be a living early signaller for advancing ocean acidification, one of the effects of global warming.
Like most other shelled marine critters, pteropods create their shells by drawing calcium carbonate out of sea water. But unlike in most other shelled organisms, the form of calcium carbonate in pteropod shells is almost twice as soluble in seawater, therefore likely to show the consequences of ocean acidification before many other marine species will.
But University of Victoria PhD student Matt Miller is questioning that.
He recently demonstrated that a protective coating of proteins, called the periostracum, protects pteropod shells from acid.
To test the coating’s protective nature, he intentionally damaged a small area of the periostracum on pteropods from the Salish Sea, then incubated the pteropods in either acidic or alkaline sea water.
“Our study has found that the shell is actually protected by the periostracum — only areas of the shell where the periostracum was damaged showed any signs of dissolution,” he says of the results, which were published in the ICES Journal of Marine Science. This, he says, is strong evidence that the periostracum protects the shell from dissolution in acidic conditions.
This is not to say increasingly acidic oceans won’t harm the animal — just that it may not be the canary in the coal mine that scientists had believed.
Small things matter.
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