It’s over six years now since I wrote the post Sick seas 1: acidifying oceans based on Alanna Mitchell’s book Seasick: the hidden ecological crisis of the global ocean. I had intended to do a series of eight or nine on aspects of ocean health, each based on a chapter in Mitchell’s book.
Back then I related how researcher Joan Kleypas and colleagues were doing some ‘back of the envelope’ calculations on the effect on CO2 on the chemical composition of oceans at a meeting in Boston in 1998, when they “realised they were looking at a marine Armageddon”.
Kleypas ran into the bathroom outside the committee room and threw up.
Some calcifiers would go extinct, and as a consequence some other life forms would vanish. Plankton as one form of calcifier are at the bottom of the food chain and incidentally produce about half the oxygen in the atmosphere (the review linked above says over 70%).
Kleypas and her colleagues found other scientists reluctant to accept the true vulnerability of the oceans, but eventually the acidifying oceans story was accepted.
Later Jo Chandler’s Feeling the heat reports on a Canadian study that estimated a 40% decline in phytoplankton over the last century, much of that since 1950.
Climate Progress reports on a study of the effects of ocean acidification on more than 150 species of marine life:
They found that at atmospheric carbon concentrations of 500 to 650 parts per million — levels that are predicted by 2100 — corals, echinoderms, mollusks and fish were negatively impacted, though crustaceans such as crabs and lobsters were relatively unaffected. When atmospheric carbon concentrations rose above 650 ppm, all groups studied were harmed.
The study also found that ocean acidification is likely to affect sea life in multiple ways — fish might become hyperactive or confused, causing them to be less fearful of predators, and their metabolism could also change.
Graham Readfearn reports on an experiment at Heron Island which found that with expected emissions by 2100 the reef will be on the slippery slope to slime. An earlier study led by the Australian Institute for Marine Sciences found that since 1985 the reef has lost more than half its coral cover.
The decline of fisheries
Mitchell also devotes a chapter to the work on Boris Worm, Heike Lotze and others who are concerned about human impact on fisheries. Worm was the lead author of a scientific paper, later known as “the 90 per cent paper” or “the crazy paper” which became notorious because it happened to mention, almost as a footnote, that all commercial fisheries could be depleted by 2048. Lotze works on the reconstruction of historical marine and shore systems. She found that the Waddell Sea, off Denmark and Germany, and indeed the continental rivers were teeming with life 1000 years ago. Worm and his colleague Ransom Myers found that on average 80% of fish populations vanish within 15 years of the commencement of modern industrial fishing and that to quote Mitchell:
“every single large predatory fish across the global ocean fell by 90 per cent in the fifty years after industrialised fishing began.”
Worm has been thoroughly worked over by commercial fishing interests and others who think he’s alarmist. This paper puts the controversy in some context and tells us:
The chief protagonists Boris Worm and Ray Hilborn met for a National Public Radio interview and decided that a public controversy served the interests of neither the scientific community nor the public. They invited about 20 prominent scientists and dozens of graduate students to join in a collaborative project facilitated by the National Center for Ecological Synthesis and Analysis (NCEAS), with the aim of compiling new datasets to reach a consensus view of the state of the world’s fisheries. The resulting analysis showed that although 63% of assessed fisheries are below the biomass that would produce maximum sustainable yield, harvest rates are now at or below sustainable levels in 7 of 10 well-studied ecosystems. These lower harvest rates should promote rebuilding to biomass to levels that would support maximum sustainable yield.
It took humans roughly 50,000 years to deplete the planet’s large land animals, 5000 years to exhaust most of the planet’s coastal environments, 500 years to fish out the continental shelf, 50 years to impoverish the open ocean and about 5 years to run through the creatures of the deep ocean.
He’s concerned that fishing authorities don’t use true historic data as their starting point and he’s concerned about tipping points beyond which recovery becomes impossible. Also, overall, he can’t find anyone in charge!
This article also expresses concern.
Jellyfish über alles
Tipping points are also the concern of Lisa-ann Gershwin talking to Robyn Williams on The Science Show:
When I began writing this book, I had the idea that contributing to public understanding would be kind of groovy. At the time I had a naive gut feeling that all was still salvageable and that by really ‘getting it’, we would still have time to act. I even thought that we could hand our children a better world, with all the perks we enjoy plus a bit of extra wisdom gleaned along the way.
But I think I underestimated how severely we have damaged our oceans and their inhabitants. I now think that we have pushed them too far, past some mysterious tipping point that came and went without fanfare, with no red circle on the calendar and without us knowing the precise moment it all became irreversible. I now sincerely believe that it is only a matter of time before the oceans as we know them and need them to be become very different places indeed. No coral reefs teeming with life. No more mighty whales or wobbling penguins. No lobsters or oysters. Sushi without fish.
In their place, we shall see blue-green algae, emerald green algae, golden algae, flashing blue algae, red tides, brown tides, and jellyfish. Lots of jellyfish. The seas were dying for us to notice their distress, but we collectively chose to overlook the red flags. Of course, we didn’t need to listen, we know better: we are Homo sapiens…the wise man.
Throughout the history of life on Earth, major macroevolutionary events, such as mass extinctions and periods of intense evolutionary diversification, have been linked to global-scale changes in environmental conditions. Even relatively small changes in climate have driven major ecosystem change through sea-level fluctuations leading to the opening of straits or the emergence of isthmuses. Today’s overfishing, pollution, and greenhouse gas emissions are comparable to the intense global warming, acidification, hypoxia, and mass extinctions through history…all at once.
It is unlikely that all life in the oceans will disappear, or that photosynthesis will simply cease; it is, however, likely that our marine ecosystems will undergo radical simplification. This is already occurring in many locations around the world. Diatoms are being out-competed by flagellates. Large copepods are being replaced by small copepods. Fish-dominated systems are flipping to jellyfish-dominated systems. High-energy food chains are being replaced by low-energy food chains. Jeremy Jackson explains it best.
By fishing down our food webs and initiating trophic cascades, we are removing the large predators—the things with teeth. Ocean acidification is dissolving the hard parts of corals, molluscs, echinoderms, and crustaceans, sparing only the soft squishy species. And hypoxia is killing off even the species we can’t bring ourselves to care about.
Jackson has been quoted a lot lately in the popular press for his view that we are creating a ‘rise of slime’. And he appears to be right. For a glimpse of what our oceans may look like in the future—and maybe not all that far, in my lifetime and yours—jellyfish evolved in a world devoid of predators, and their only competitors were each other. Long before plants and animals became abundant, the seas were anoxic or hypoxic. About 2 billion years of low oxygen—only 10% of today’s levels—oxygen shot up around 750–800 million years ago. The oldest unambiguous jellyfish fossils are from the Ediacaran period about 565 million years ago.
The Ediacaran ocean had small phytoplankton, such as cyanobacteria and flagellates, whereas diatoms didn’t evolve for another 400 million years. Big predators, such as fish and whales, didn’t evolve until much later when a higher energy food chain was possible, 300 million years ago for fish and 100 million years ago for whales. Diatoms had become abundant by the time marine mammals evolved, but the Ediacaran ecosystem appears to have been based primarily on jellyfish-type ecology. The climate and the ecosystem were jellyfish heaven, in which they ruled the seas for nearly 100,000,000 years as top predators.
The ancient seas were dominated by flora and fauna similar to those that today’s seas appear to be shifting toward. No spectacular coral reefs. No vast filtering mussel beds. No sharks slicing through the water, just jellyfish, lots of jellyfish. It might seem outlandish and farcical to think that jellyfish could rule the seas, but they’ve done it before, and now we have opened the door for them to do it again. Jellyfish are weeds. They are opportunists, and when they have the opportunity, taking over is probably, to some extent, just what jellyfish do.
If you are waiting for me to offer some great insight, some morsel of wisdom, some words of advice…okay then…
Those are the last few paragraphs of her book Stung. As she told us here the jellyfish are taking over, like it or not. After previous mass extinction events it has taken 3-4 million years for coral reefs to recover. Once diversity goes leaving jellyfish and algae it may take 3 to 400 million years to rebuild.
How do the jellyfish succeed?
They eat fish eggs, they eat larvae and the eat the plankton that the larvae eat. They thrive in warm water, in water with low oxygen, they move around with bilge water, and when disturbed they emit mucous which can kill a salmon farm in half an hour. They sting with a tiny harpoon that flings out at 40,000 times the force of gravity. Jellyfish can clog cooling equipment, disabling power plants, clog desalination plants and ship engines.
In a second program Gershwin told Williams that we need to investigate ways of slowing them down. Taste-wise they are like a cross between cucumber and rubber bands, but if we could find a use for them we are really good at depopulating species. It looks as though we’ve really torn it this time and we don’t know the full implications.
This article from UCSB Department of Geography tells of eating jellyfish, mainly in SE Asia, but only 12 out of about 85 species.
Der Spiegel tells us that 124 fish and 34 other animal species, such as turtles, consume jellyfish. More power to them!
Red – increase (high certainty); Orange – increase (low certainty); Green – stable/variable; Blue – decrease; Grey – no data