(This is Part 2 of the Ocean Acidification Causes, Effects, & Examples: Top 10 List, which had to be split in order to load properly. Click through to that article to read the introduction, and items 1 through 4 of the list.)
Increase In Red Tide Events
A likely co-occurrence with increasing ocean acidification will be increasingly common red tide events. That is, increasingly common and extensive blooms of the various dinoflagellates responsible for “red tides.”
An increase in these events will of course see an increase in the accumulation of associated toxins (domoic acid, saxitoxin, brevetoxin) in marine animals — and thus an increase in the marine mass mortality events that accompany this. Also, paralytic and neurotoxic shellfish poisoning will become more common as well.
To provide some background for those unfamiliar with red tides — they are essentially just algal blooms of a select number of phytoplankton species. When in mass bloom, they generally color the water they are in red, orange, or brown. These blooms typically occur in coastal areas, where they often kill large numbers of large marine animals — including various fish species, and manatees, as well as coastal birds. These mortalities are the results of the accumulation of toxins produced by the phytoplankton in the water, and in the animals living in it.
Anoxia (oxygen scarcity) is another dangerous effect of these blooms, which sometimes results in mass mortality events.
The exact factors that cause these red tides, or algal blooms, are not known for sure, but agricultural and wastewater runoff seem to be associated with increasingly common and extensive blooms — nitrates and phosphates being necessary for their growth. They also seem to be becoming more common as relevant waters continue to warm.
Collapse Of Commercial Fisheries
Ocean acidification will likely cause significant problems for many, if not most, of the world’s commercial fisheries. Overall fishery productivity is very likely to decline as the ocean continues to acidify — both as a direct result of changes to ocean chemistry, and as a result of food chain collapses.
In most parts of the world, calcifying organisms, such as the phytoplankton discussed at the start of this article, form the base of marine food chains/webs. With significant declines or displacement these webs stand to get shredded or to collapse.
To use Arctic fisheries as an example, the base of the Arctic marine food web is primarily made of pteropods and brittle stars — both of which are ill-equipped to deal with ocean acidification. Without waters supersaturated with carbonate pteropods can’t create their shells from the argonite produced through dissolved calcium and carbonate ions. As far as brittle stars go, their eggs die within only a few days when exposed to the waters expected with only moderate ocean acidification.
This matters because everything from large plankton, to seabirds, to various types of fish, to whales, rely on these animals. If pteropods and sea stars see their numbers decline significantly then the whole ecosystem is likely to change significantly, and commercial fisheries are likely to collapse.
To shift over to the situation in the US now — the majority of the country’s multi-billion dollar fishing sector is reliant upon ecosystems that feature calcifying organisms as their base. More directly, there are a number for animals that are directly valuable commercially that will decline as a result of ocean acidification — including king crabs, American lobsters, scallops, and Ocean Quahog, amongst others.
In addition to increased mortality, growth seems to be stunted by increasing ocean acidification — meaning that the weight and value of catch is reduced directly as well.
These changes are already well under way it should be noted. Research in Northern Europe, for instance, has found that in regional areas of relatively acidic waters that around 15% of species populations had already vanished. And, probably more importantly, that the vast majority of those remaining were declining and/or already very limited in numbers.
Considering the number of people who are reliant upon seafood for nutrition and/or for their livelihood, this effect of ocean acidification will no doubt have a profound geopolitical impact as well.
Great Barrier Reef
The Great Barrier Reef, the biggest coral reef system in the world, is gravely threatened by ocean acidification. The reef system saw an extensive and unprecedented mass coral bleaching just this year, and it’s an open question how much linger it will survive in anything like its current form.
As the Great Barrier Reef covers an area of around 133,000 square miles (344,400 square kilometers), and is composed of more than 2,900 individual reefs (and 900 islands), the loss of the reef system would represent a huge loss in biodiversity, and also in associated environmental services.
The reef system, which can actually be seen from outer space and is located off the coast of Queensland (Australia) in the Coral Sea, is essentially the largest structure made by lifeforms of any kind now on the earth (created by billions of coral polyps).
Ocean acidification represents just one amongst a great many environmental stressors causing problems for the reef, but it’s a notable one and the stressors are generally cumulative in their effects.
The warming of the world’s oceans is very likely the primary stressor, but ocean acidification, agricultural and wastewater runoff (increasingly pathogenic waters), tourism (a ~$3 billion a year industry), commercial fishing, shipping, oil spills, and periodic population booms of crown-of-thorns starfish (caused by overfishing of starfish predators), amongst other factors.
Research has found that the Great Barrier Reef has suffered a greater than 50% decline since 1985 — two-thirds of this loss has apparently occurred since just 1998.
Increasing levels of pollution and declining water quality is a major contributor to coral stressing, and thereby coral bleaching. Around 80% of the land adjacent to the Great Barrier Reef is intensively used for sugar cane operations and for cattle/beef operations — this highly intensive use of the land results in heavy soil erosion, and also heavy runoff of applied herbicides, pesticides, and synthetic fertilizers.
These introduced chemicals and nutrients pose major health problems for most corals, both directly and with regard to blooms of pathogenic microorganisms and phytoplankton (which feed crown-of-thorns starfish larvae). Mining runoff is another problem in some regions.
This situation is exacerbated by the fact that many of the region’s coastal wetlands have been more or less destroyed over the last 100 years — greatly reducing filtering of runoff, and deposition of sediment.
While commercial fishing is a major problem both with regard to the removal of keystone species, and also with regard to habitat destruction, shipping is a major problem as well. Partly simply as a result of routine damage caused by the passage of large ships, and partly as a result of shipwrecks. Many of those reading this will probably remember that a coal carrier by the name of Shen Neng 1 ran aground on Douglas Shoals back in 2010, and in the process released up to four tonnes of oil into the surrounding waters. Nearby reefs were extensively damaged by this event.
(The image below is of crinoids not corals, part of the broader coral reef environment.)
To give an idea of how important the Great Barrier Reef is biologically I’ll provide a basic overview here of the lifeforms that live there:
– At least 30 species of whales, porpoises, and dolphins — including the humpback whale, the dwarf minke whale, and the Indo-Pacific humpback dolphin.
– The dugong, a close relative of the manatees, and one of the only types of Sirenia still in the world, lives in (relatively) large numbers there.
– Over 1,500 species of fish live on the reef — including red bass, various types of snapper, the clownfish, the red-throat emperor, and various coral trout.
– Roughly 49 species are known to mass spawn on the reefs.
– 17 species of sea snakes live on the Great Barrier Reef.
– 6 species of sea turtles live there — including the leatherback sea turtle, the loggerhead sea turtle, the green sea turtle, the flatback turtle, the hawksbill turtle, and also the Olive Ridley.
– 15 species of seagrass form beds in the immediate vicinity — thereby providing fish habitat and food for turtles and dugongs.
– Saltwater crocodiles are known to live in associated mangrove forests and salt marshes near the reef, and to occasionally visit it.
– Roughly 125 species of sharks, skates, stingrays, and chimaera, live on the Great Barrier Reef.
– Around 5,000 species of mollusks are known to live on the reef — including various cone snails, and the giant clam.
– 9 species of seahorse are known to live there.
– 49 species of “pipefish” are known to live there.
– At least 7 species of frogs inhabit the associated coral/reef islands.
– 215 species of birds are known to nest and/or roost on associated islands and to visit the reef for various reasons. This includes the white-bellied sea eagle. At least 1.4 to 1.7 million birds are known to use reef islands as breeding sites.
– Reef islands are known to support at least 2,195 species of plants. These plants are mostly propagated by birds.
– There are probably between 300 to 500 species of bryozoans living on the reef.
– There are likely more than 330 species of ascidians living in the Great Barrier Reef system.
– At least 400 species of corals a known to live in the Great Barrier Reef (both hard and soft corals). The majority of these corals breed in mass spawning events related to seasonal, lunar, and diurnal, cycles. The corals present are fairly varied, with the soft corals belonging to at least 36 different genera.
– At least 500 species of seaweed and marine algae are known to live on the reef. This includes 13 species of the genus Halimeda — notable for being ecosystem engineers that create huge calcareous mounds up to 100 meters or more wide.
Oyster Hatchery Collapse In Oregon
While ocean acidification has yet to have truly disastrous effects on commercial fisheries, owing to particular patterns of ocean circulation in the Pacific Northwest commercial oyster hatcheries are already beginning to experience significant setbacks.
What happens is that colder waters, that are more acidic than regional surface waters currently are, upwell near the coasts from the deeper parts of the Pacific Ocean, and move into various regional estuaries, bays, and fjords. As a result, coastal waters where oysters are commercially farmed in Oregon, Washington, and British Columbia, are now acidic enough that oyster larvae often can’t form shells. Meaning, that whole generations of oysters (and other shellfish) in the region can’t come into existence, they are simply dying and dissolving into the ocean.
Since the problem was first recognized roughly a decade ago, commercial hatcheries have scrambled and come up with some solutions that will work for now — mostly simply buffering the water that the larvae grow in with sodium bicarbonate.
While this solution will likely remain commercially viable for hatcheries for some time (the scale needed for hatcheries isn’t that great), with ocean acidification set to continue, and to actually accelerate, for the foreseeable future, the businesses involved are at this point likely living on borrowed time.
The situation with regard to regional wild oysters, for instance, is pretty dire at this point — wild oyster reproduction has been consistently failing in many bays and coastal regions of the Pacific Northwest, for many years now. While most oysters are actually rather long lived if not killed and/or eaten, the fact that reproduction is consistently, completely failing due to current levels of ocean acidification makes it pretty clear that their long term prospects in the region aren’t good.
So-called climate engineering is often brought up in debates as a potential solution to anthropogenic climate change, and also to ocean acidification. How viable is climate “engineering” though? Does the use of the word “engineering” imply that controlling a system as truly enormous, and full of myriad complex interactions as the planet’s climate system is as simple as building a car? (A process that people have essentially near-complete control over.)
A great many of those involved in relevant fields have publicly come out against climate engineering in recent years, owing to the fact that while the global climate system can certainly be altered by humans, controlling or “engineering” it to any great degree is likely another matter.
Such attempts would likely be incredibly expensive, and not at all cost-effective, it should also be noted.
And what about “unintended consequences?”
To take the idea of fertilizing the oceans with massive quantities of iron to stimulate photosynthesis in phytoplankton as an example — while the potential is possibly there to lower surface-level acidity in the ocean through such an approach, deep ocean acidity could well be greatly increased as a result, and this deep ocean acidity would of course find its way back to the surface eventually anyways. And, more importantly, to use such an approach on a scale massive enough to truly have an impact would be prohibitively expensive. The formation of massive dead zones (ocean anoxic zones) is also a likely side effect of such an approach.
All of that said, people being the rather desperately psychologically unwell creatures that they now are, climate engineering seems very likely to be attempted in various corners of the world over the next century — as the harsher effects of climate change and ocean acidification begin bearing down on the world’s agricultural, industrial, social, and political systems.
As a bookend to this list, I’ll highlight some of the strange animals that went extinct as a result of, or in conjunction with, the major ocean acidification events of the Great Dying (end-Permian mass extinction event).
Of particular note is that the giant sea scorpions (Eurypterids) completely disappeared; the last of the marine arthopods known as trilobites finally went extinct; the spiny sharks (acanthodians) went extinct shortly after the mass extinction; the last of the giant-dragonflies/griffinflies (Meganisoptera) went extinct; and the previously dominant, mammal-like suborder of therapsid synapsids known as Gorgonopsia disappeared completely.
As a brief overview of each:
Giant Sea Scorpions – The sea scorpions (eurypterids) weren’t actually all giants, though one genus (Jaekelopterus) did feature species that grew to be more than 8 feet long (~2.4 meters). They lived primarily in the warm, shallow waters of seas and lakes, and were often top predators. They survived from roughly 470 to 252.17 million years ago — meeting their end during the turmoil of the Great Dying.
Previous to their extinction, the family possessed a global distribution. Notably, despite later dominance of shallow seas, lakes, and estuaries, one of the earliest of the type was fully marine.
The largest species of the family were in the aforementioned Jaekelopterus genus, which had its greatest distribution around ~390 million years ago. It is the largest arthropod known to have ever existed, and grew to be at least 8.2 feet long. Two species are known, one associated with freshwater, and one with estuaries. These fossils were found in Northern Europe and in Wyoming, respectively.
Trilobites – Trilobites (Trilobita) were a group of marine arthropods that first appeared (in the fossil record) around 521 million years ago and persisted until the end-Permian mass extinction, around 250 million years ago. They were one of the most common types of life during much of this time period but a very slow, drawn-out decline during the Devonian — following the extinction of all orders except for Proetids, and the accompanying loss of variety.
Altogether, there were at least 17,000 different species of trilobites and they appear to have lived practically everywhere in the world at some point or other. Some appear to have been scavengers, some to have been predators, some filter feeders, and some involved in symbiotic relationships with sulfur-consuming bacteria — so a wide variety of lifestyles. It’s not clear if any lived as parasites.
Spiny Sharks – The spiny sharks (acanthodians) weren’t true sharks, though they often resembled them. They actually predate them though, so they seem to have gotten to the morphology in question before the sharks did. The earliest acanthodian fossils predate sharks by some 50 million years.
When they emerged bony fish had yet to conquer the oceans, and acanthodians seem to have successfully filled similar niches. They finally died out completely during the end-Permian extinction event.
Giant Dragonflies – The giant dragonflies (Meganisoptera), alternatively known as griffinflies, were an order of very big flying insects that lived from the Late Carboniferous to the Late Permian. The last species of the order seem to have died out during the end-Permian mass extinction event. While some species within the order were only a bit bigger than the largest modern dragonflies, some were many times larger — particularly Meganeuropsis permiana, which died of well, before the end of the Permian. That species grew to feature wingspans at least 28 inches in length (71 centimeters). As modern dragonflies are, the Meganisoptera appear to have been predators.
Gorgonopsia – The Gorgonopsia were a suborder of therapsid synapsids, that, as with their close relatives, are considered to have been “stem mammals” (not direct ancestors of modern mammals though). So while in some ways seeming reptilian, they also featured traits similar to those of mammals — these include: pillar-like rear legs, differentiated tooth shape, a particular approach to ear-bone formation, and a vaulted palate (in the mouth), amongst others.
Notable qualities of theirs would have been: their good eyesight, their powerful sense of smell, and their great speed of movement.
Gorgonopsians are particularly notable as they were highly successful… For a short time period. They were essentially the largest carnivores of the late-Permian time period — with the biggest, Inostrancevia, being the size of a large bear.
The image that’s featured above isn’t of Inostrancevia, but is notable because of just how familiar it looks to modern eyes — the similarity to some modern mammalian predators, such as the jaguar, is striking.
As with mammals, Gorgonopsians may well have had a full coat of “fur”, but evidence is sparse (coprolites with remnants of fur) so there’s some debate.
The earliest gorgonopsians, which seem to have emerged in the Middle Permian (before going completely extinct by the end-Permian mass extinction), appear to have been no larger than a mid-sized dog, before then aggressively expanding into empty niches (mostly those left by the then extinct dinocephalians that had previously dominated).
It’s interesting that gorgonopsia represents the only theriodont line to go extinct during the Great Dying — with most smaller (physically) theriodont lines being relatively unaffected by the mass extinction.