The ST suggested that mankind’s emission of CO2 was having profound effects today on shellfish in Northwest waters. I argued that the ST story was exaggerating the current impacts of CO2 increases and neglected a key point: that the short periods of lowered ph (a measure of acid/base ) were predominantly caused by natural variability. The truth is that mankind's CO2 emission is actually a very minor player in the current problems at local oyster larvae hatcheries.
The response of the Seattle Times to my blog was rapid and pointed. They put up a page on their glossy “Sea Change” web portal saying that my blog “ignores the science” (see above for a sample) and refused to allow me to submit a response that would also be available on their site.
Unfortunately, none of their response to my blog dealt with the scientific questions I raised, rather their defense was that they had talked to the experts. I had a nice conversation with Danny Westneat, one of the few ST staffers with a science background (B.S. Chemistry). But he wasn't interested in talking scientific details either. Just process.
Industrial aquaculture on Puget Sound: Thousands of plastic tubes for propagating geoducks
Not exactly a pristine setting.
Over the past weeks I have done extensive additional research, including talking to UW specialists in coastal oceanography and ocean acidification, as well as several individuals in the local shellfish industry. I have received nearly 50 emails and comments and more than a dozen calls. Many, including academic researchers and industry insiders, told me I got the facts right. The additional information I have secured has solidified my conclusion that the ST article strayed from key facts and avoided mentioning information that did not fit well with their “story.” The true story is far more complex and nuanced than the ST article suggests.
In this blog, I will go substantially beyond my previous note, with more technical detail and scientific evidence. You judge for yourselves where the truth lies.
The Seattle Times emphasized the “lethal” waters that were killing shellfish, particularly oyster larvae. But the truth is that native shellfish species living in our waters have been doing fine. In fact, even non-native species growing in our natural aquatic environment have been doing well.
The problem was limited to factory aquaculture of non-native species. Or to put it more exactly, limited to big tanks containing oyster larvae of non-native Pacific oysters from Japan. Oyster larvae that could not reproduce in our cold waters, with or without any extra CO2. The problems only occurred in these oyster larvae factories during short periods during summer when there was strong upwelling of coastal waters-when cold, high-CO2 waters located at depth were lifted towards the surface as a result of stronger than usual northerly winds.
To put it another way, the “lethal” waters described in the Seattle Times article are found here:
And NOT here:
That puts a different edge on the issue, doesn't it? As I will discuss later, the oyster larvae factories (located on Washington and Oregon coastal bays) no longer have a problem with oyster larvae death. The problem has been essentially solved. And let me say this again: the shellfish industry is using a non-native oyster species that can’t reproduce successfully here in the NW because our waters are too cold. That is why they have to artificially hatch the larvae in warmed waters in commercial plants.
Aragonite versus ph
Some of the Seattle Times critics of my blog complained that I did not talk about aragonite, a measure of the amount of carbonate ions in the water; the reason I did not do so was because the ST article did not talk about it. But let’s do so here.
The shells of oysters, clams, and the like are made up mainly of calcium carbonate (CaCO3) and are sensitive to the concentration of carbonate ions in the water. The reaction of CO2 with seawater reduces the availability of carbonate ions (CO3). At the same time, CO2 also decreases the ph. A measure of the availability of carbonate ions is the aragonite level (indicated by the Greek letter Omega). When the aragonite level is greater than one there is supersaturation of carbonate (good for shell formation), when less than one the water is undersaturated and it is harder for shellfish to build shells. As shown in many studies, there is a close relationship between ph and aragonite levels: as the ph of water goes down (less basic), the aragonite level declines. The paper by Barton et al. 2012 illustrates this very close relationship between ph and aragonite level during a summer month they studied (see below). No one is going to argue with that.
Ph and aragonite levels at Oregon's Netarts Bay, 01 June–03 August 2009. Notice how closely they follow each other.
An essential point I am making is that natural variability in acidity/ph (and thus aragonite level) in Northwest coastal waters is FAR, FAR larger TODAY than the contribution by human-injected CO2 in the atmosphere. The problem in the hatcheries were first noticed in 2006 during which the die-offs of oyster larvae only occurring during strong upwelling periods, when high pressure off the coast produces strong northerly winds that caused cool, low-ph water to rise towards the surface.
In 2009, a field experiment (published in Bartons et al 2012) took detailed measurements of water from Oregon’s Netarts Bay at one of the hatcheries (see figure above). As you can see from that figure, ph varied from nearly 8.2 to 7.6 (about .6 ph units). You will also notice there were huge daily swings of ph of around .4; this is due to photosynthesis during the day reducing the CO2 levels and thus increasing ph. This point is important…keep it in mind for later. The Barton et al paper and several others document the fact that the periods of lowest ph level are associated with times of strong upwelling.
So how much of the low ph is is associated with human-connected CO2? If the Seattle Times is right, then humans are making a substantial contribution to low ph and the "lethal" factory waters. We can calculate this.
The low ph periods only occur during periods of coastal upwelling. According to a highly quoted paper by Feely (Science 2008), the upwelled waters were last in contact with the atmosphere about 50 years. A local physical oceanographer told me 40 years, so let’s be conservative and assume 40 years ago (1971). Atmospheric CO2 levels were much lower then compared to now (400 ppm now, versus 325 then--see graph below to prove this). A number of studies (including Feely) have suggested that general pre-industrial levels of
open ocean ph were about .1 lower than today. Before industrial society, the CO2 level was about 280 ppm, about 45 ppm less than in 1971. So let's assume that the upwelled waters today were exposed to 1971 levels of CO2. So it is very reasonable to assume that the contribution of human-produced CO2 levels to the ph change today in upwelled waters is thus (45 /120)*.1 or .0375. Let’s round that up to .04.
Consider the implications of this. The lowest ph observed that (2009) summer (7.6), would have been 7.64 without human CO2. Doesn’t seem like such a headline grabber does it? To but it another way, human CO2 impact is 6.6 % (.04/.6) of the natural variability observed that summer.
To put this in further perspective. Imagine a heat wave in which the temperatures are 20F above normal one day. Imagine that CO2 increases explained 6.6% of that. This would be 1.32F. The heat wave was made slightly worse, but the heat wave would have happened with or without the CO2.
Later in the century the story will be different. In 50 years, human impacts on ocean acidification will be twice as large—still smaller than natural variability, but more significant.
And why did problems start in 2006? One potential reason: a source of natural variability in Pacific Ocean circulation, the Pacific Decadal Oscillation (PDO) had just switched into its cold phase after being in a warm phase since the late 1970s. 2006 was also a very strong upwelling year.
Joint efforts between scientists at Oregon State, the University of Washington, and NOAA PMEL helped solved the initial mystery of why the hatchery larvae were dying. The oyster larvae in the factory tanks did not do well during upwelling periods of low ph and low aragonite levels. And the solution was relatively easy. The hatcheries were pulling water in during the morning when ph was low. They changed their procedures to acquire water during the afternoon when ph was higher (natural photosynthesis during the day pulls CO2 out of the water) and that seemed to solve the problem. Some oyster larvae factories also enhanced the carbonate levels by adding some chemicals. So the Seattle Times is trying to make a headline story of a very small issue that has been alleviated by improved factory procedures.
The Puget Sound environment: a very different world
As noted in research such as Feely et al 2010 (Estaurine, Coastal, and Shelf Science, 88, 442-449) the ph and argonite level situation is very different in inland bodies of water like Puget Sound. They note that in the shallow surface waters of inland Washington there was no problem during the summer (e.g., August 2008) with the aragonite (calcium carbonate ions) being saturated or supersaturated everywhere (good for shellfish). The waters were not hitting the lower phs observed on the coast. This is to be expected considering that deep coastal waters with low ph can only get inland in the deeper subsurface waters. In the shallow inland waters, photosynthesis, warmer temperatures, and different water origin keep things fine for oysters and other shellfish. That is why the oyster larvae can be transferred to beds in Puget Sound to grow big and fat.
Furthermore, Feely et al and other papers document that there are other human-related factors in Puget Sound the can influence ph and oxygen levels, like nitrogen-rich effluent from farms, sewage, and other origins. Or the impacts of heavy precipitation and intense river outflows. Not so simple. Even more so than on the coast, human enhanced CO2 levels in the atmosphere is a very minor player in the ph and aragonite levels in Puget Sound and other inland waters.
Factory Shellfish Farming: Do they bring environmental risks?
The Northwest shellfish industry is big business: according to a NOAA website, this industry brings in an estimated 170 million dollars a year into the NW economy and employes more than 3000 people. Some of the environmental practices of this industry are of concern. For example, they have sprayed large amounts of the insecticide carbaryl on wetlands to kill burrowing shrimp and other industry pests (see their permit information here). This chemical is a likely human carcinogen (see EPA statement). To quote a letter by oyster expert John McCabe:
The destruction of two native crustacean species, the ghost shrimp,Callianassa sp., and the mud shrimp,Upogebia sp.,with the pesticide Carbaryl, for the sake of facilitating the production of the invasive species Crassostrea gigas (Japanese or Pacific oyster), has long been practiced on Willapa Bay
Some oyster farmers use carbaryl pesticide to kill burrowing shrimp on their oyster beds because the sediment the shrimp excavate smothers and buries oysters
Eelgrass, Willapa Bay
The Seattle Times article did not concern itself with the environmental impacts of the large shellfish industry? Why? I believe the reason is that it did not fit their "story" that human-enhanced CO2 in the atmosphere is the real villain.
And why did the Seattle Times focus on a very minor issue for oyster aquaculture (ocean acidification) and why did environmental activist groups jump on this story? I suspect many of them are determined to find an acute example today of the impacts of growing levels of CO2 in the atmosphere.
The truth is that anthropogenic increases in CO2 are only having subtle impacts on our regional weather today, the big changes and impacts will occur decades into the future. Both global warming and ocean acidification are very serious issues and by the end of the century their impacts will be substantial. But exaggerating and hyping the effects today are unacceptable. Citizens and policy makers deserve the facts, not exaggerations designed to elicit the proper response. Crying wolf in the end is counterproductive and undermines the credibility of science to promote the proper actions is unacceptable.
Hopefully, I have convinced you that this is a complex issue, one deserving of additional research. We are fortunate, that with the support of the State, the UW has initiated an Washington Ocean Acidification Center, and in concert with local colleagues at NOAA PMEL, they hopefully can further unravel the science.
From the Seattle Times web site. Not stretching things too much. Killing BILLIONS of oysters.
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