Ocean Acidification on the South Coast: Nature at Bat

March 23, 2015, ran in early April, 2015

Understanding ocean acidification is not simple, because the process of acidification is not simple. Neither is the rest of nature simple. Nature is more complex that we can imagine. We can over-harvest, mine, bomb, poison, pave and otherwise mess up this great world, do our very best to destroy the ecology that supports our lives, and yet, nature bats last.

There’s some predictability: If we pump greenhouse-warming gases into the atmosphere, the atmosphere will warm up. We are doing this. It is warming. Those gases are absorbed by water all over the world, because the balance of gases in the atmosphere is reflected by the balance of absorbed gases in the water. It’s a slow process, because there is a lot of water, which can hold a lot of carbonic acid and heat. That slow time lag between absorption and response has tricked many into thinking that what we do doesn’t matter to the global ecology.

Then there are down-welling and up-welling areas. There are areas of the oceans where cold salty water accumulates and drops down into the depths. Called ‘down-welling’ areas, these occur in the north Pacific, north Atlantic, south Indian Ocean and around Antarctica. Bottom flowing currents move the cold, salty water across the seafloor towards continents, where this water rises to the surface, called ‘upwellings’. There are upwelling areas all around the world. Some run all the time, others only with winds from certain directions. In the Pacific Northwest, upwelling usually occurs when winds are from the northwest in sunny, dry weather.

Upwelling in action:  Fog forms over cold water, comes ashore over the beaches, and dissipates over warmer land. On the horizon, blue water indicates the water there is warmer, not upwelled. This aerial is looking north over Ft Stevens across the Columbia Entrance to Cape Disappointment.  Photo by Kathleen Sayce

A summer day with active upwelling here on the South Coast is foggy with northwest winds. It’s sunny inland, it might even be sunny on Willapa Bay, but on the ocean beach it’s foggy. The fog is created when cold, old, very salty ocean water comes to the surface and cools the air. Onshore winds push the cold air onshore one, two, five, ten or twenty miles.

In the water, something more complex is going on when the acidic upwelled water reaches the surface. This water is typically thirty to fifty years old, and can be much older. It’s very salty. It’s high in some nutrients, and low in oxygen. As upwelled water rises to the surface, nutrients are taken up by phytoplankton that live only as deep as sunlight can penetrate into the water––usually less than fifty feet. Phytoplankton grow quickly in summer, tiny single-celled plants that can divide several times a day under good conditions. Those old nutrients are food for the phytoplankton.

Zooplankton can’t keep pace with the growth of plants. Not all phytoplankton cells are eaten, and when the excess cells die, they fall to the seafloor and decompose. This strips oxygen from the water column and seafloor, killing those animals that need oxygen to survive. Their bodies also decompose. More oxygen is tied up in each new wave of decomposition, forming a dead zone of low to no oxygen that expands as summer progresses.

A large dead zones appears each summer along the Pacific Northwest Coast; this year it persisted through winter. It typically extends from south Vancouver Island to northern California. Affected animals include crab, clams, fish, zooplankton, and more. Some fungi and bacteria thrive in low oxygen conditions, and they flourish in this dead zone, growing into huge carpets of mixed species––all thriving on no oxygen and high nutrients.

The second complexity is that this water is more acidic than it was a few hundred or even a few thousand years ago. Remember, what goes into the atmosphere is absorbed into water. With increasing amounts of carbon dioxide in the atmosphere, then in the water there is more and more carbonic acid, increasing the acidity of seawater.

The third complexity is that this cold, old upwelled water is low in calcium, and the local rivers are also low in calcium. For mollusks, calcium is essential to form shells. It also goes into solution (dissolves) easily in more acidic water, and as we have learned in the past ten years, more acidic water is not good for oysters and other bivalve larvae.

There’s always a weak point, a stage in a life cycle when each organism is most vulnerable to what appear to be tiny insignificant changes. For shellfish, this is as larvae, as they undertake the change from the free-swimming form to the shelled form, prior to settling down to become adults. At this stage, oysters and other bivalves grow their proto-shells. But in more and more acidic water, larvae can’t maintain shells, because the calcium dissolves out as fast as shell forms. The larvae linger for days to weeks, trying to make the change. Eventually they die.

But wait, you say, isn’t there deep, cold, low acid water off Hawaii? Hasn’t at least one oyster grower got a hatchery there, safe from the upwelled water? Yes. But oysters are not dominant species of food webs in the oceans of the world. Coccolithophores are a key animal, tiny calcium-shelled zooplankton that eat phytoplankton, and in turn are eaten by larger zooplankton and fish, which are eaten by larger fish, and on up the food web. Take coccolithophores out, and oceanic food webs aren’t just on a diet, they collapse. Fish populations go down; larger fish, birds and mammals that live on them are impacted too. Fishing fleets. Tribes. Food processors. Sport fishers. Oceanside restaurants selling fish and chips. Anyone who eats, catches, processes, and sells saltwater fish is affected.

So there you have it, a quick look at the complexity of ocean water chemistry, and the complexity of the ocean food web, and a hint at the coming changes in ocean ecology. There’s nature, standing near the plate, swinging the bat to warm up. She’s thinking about what she’ll do this time. She might bunt, and take out some nearshore ecosystems in a few key areas. Leave some other spots alone. Or swing for the fence, and crash major cocolith’ populations, along with sardines, anchovy and herring. If that happens, tuna, salmon, and other major fish populations go too, as these fishes are their key food sources. We simply don’t know what nature’s going to do in response to our plays, this time, or next time. We will have all the innings we can manage to stay in the game, but nature bats last. 

Limestone outcrops, fossil clams and calcium

Written February 16, 2014, published in late February, 2014

Waters that flow to the Pacific Ocean from the Coast Range, Cascades and Columbia River basin tend to be low in calcium. Columbia River waters are high in some heavy metals, several nutrients, any number of pollutants and several radioactive isotopes. These are not a surprise. With numerous dams, cities, thousands of acres of irrigated farmland, mining, and other activities upriver, and parent rocks from seafloor basalts and the Columbia Plateau flood basalts, opportunities for all these compounds and elements to enter the water is very good. But why so little calcium?

Calcium accumulates in oceans as calcium carbonate in shells when water conditions are basic, with a pH above 7.0, which is considered neutral. One of the three most common biopolymers on the planet (cellulose and chitin are the other two), calcium carbonates are formed by several groups of invertebrates into durable, protective outer walls to shield softer bodies.

Common invertebrate groups that make carbonate shells include mollusks, barnacles, corals and brachiopods. Vertebrates also use calcium carbonate to make bones which support bodies internally instead of protecting them externally. Calcium is important to plants, which use it to form healthy cell walls, and produce fruit. It's mobile in water, which is another way to say it washes out of the soil easily.

Mollusks are one of the most successful body types on the planet, and include snails, clams, oysters, limpets, slipper shells, and several shell-free forms. Species in this large and very diverse phylum live in almost all wet to damp habitats on earth, including deep in the ocean, in shallow saltwater and in freshwater, on land and trees. In some species, the external shell is reduced or absent, as with land-living slugs, as well as squid and octopus. More about land-living mollusks later, which include snails, jumping slugs, voracious garden-living slugs from around the world, and others.

Numerous small fossil clams can be seen as circles to ovals on this limestone rock, photographed at an old quarry on Bear River. The fossil clam in the middle of this image is 20 mm long. Photograph by Kathleen Sayce

Carbonates form masses of limestone when shells accumulate in channels, or grow together in large reefs, and then later are heated, subjected to pressure, and turn from individual shells into rocks. The more heat, pressure and time, the harder the rocks that form, going from fairly soft limestones to quite hard marble over millions of years. In geologic time, this area was a enclosed and increasingly shallow sea from around 55 mya (millions of years ago), to around 10 mya, as the Cascades and then Coast Range/Willapa Hills rose. There was a lot of volcanic activity, lava flows, flood basalts, ash falls, which buried the reefs and shell beds under layers of other rocks, often under very acidic conditions.

There's one thing calcium carbonates can't resist (sorry for the pun), and that is acid. Air or water with a pH of less than 7.0 is acidic, and gets more acidic as pH goes from 7 towards 1; if the pH is above 7, then it is alkaline. Acids break down the carbonates, release calcium and carbon dioxide in the carbonates, and dissolve the material, no matter if the carbonate is an oyster shell, a marble statue, or a limestone wall. When conditions are acidic, as is often the case during volcanic activities, or with high levels of pollution (think 'acid rain'), or with ocean acidification, then limestones or shells dissolve more quickly. All that volcanic activity in geologic time helped dissolve limestones when the reefs were young; the present climate of long wet winters with acidifying conditions also promotes dissolving.

A few outcrops remain in the Willapa Hills from those extensive reefs of millions of years ago. Tom Horning, geologist, who lives in Seaside, Oregon took me to see a small limestone outcrop on the Bear River a few months ago. I wanted to see the shells and distinctive color of the local limestone, which is a muddy yellow, very different from black-gray-brown basalts, the most common local rocks. We walked down to the river through a recent clearcut, and found the remains of a limestone quarry on the banks of Bear River. With Tom's help, I was able to photograph several patches of clam shells. This outcrop is less than one hundred feet wide along the river bank, and was mined decades ago to make cement. A bit of it still remains visible, a long gouge out of the hillside where the rocks are softer, yellowish in color, and if the moss and soil are scraped away, where fossil clams shells can be seen.

It's one thing to read a geology map and fossil books, and learn that extensive reefs were found in the shallow sea over our area in the Eocene to Miocene periods. Or to learn that oceans were so alkaline then that the water had a pH of 10 to 14, which is very alkaline. It's something else to hold a rock in your hand as a relict of those past eons. In generally acidic conditions on land or in water, limestones survive when they are protected from those acids, well elevated above fresh or saltwater, protected from rainfall by other sediments. In low calcium conditions today, we see the past, where a long parade of acids wore away those reefs and shell beds.

It matters now how much calcium is where on local lands and in waters, because our estuaries are acidifying along with the Pacific Ocean. Local scientists are studying how to boost calcium around shellfish beds, to protect young clams and oysters, and enhance growing conditions for fish and other species. We already know that upwelled water from the deep ocean is acidic and low in oxygen. If it's also low in calcium, then the mollusk larvae in our estuaries have a triple whammy to face in their first few days of life: low pH, not enough oxygen, not enough calcium to build or rebuild their new shells.

Willapa Bay's waters can oxygenate well with the tidal cycle, and if the water can be buffered with additional calcium, then the young oysters and clams may make it past the critical first couple of weeks, and have a chance of surviving. We can't solve ocean acidification for the Pacific Ocean, or the world. But perhaps we can buffer it for our shellfish industry. Finding the right way to do this starts with knowing all the local calcium sources.