Friday, July 31, 2015

What Fish Need is Bicycles - BPL

Title changed from Choking the Fish

While there has been considerable discussion of desorbing carbon dioxide from the warming oceans, less, to literally none, has been paid to the stuff that sea life breaths.  This, it turns out, could be of even more importance because oxygen concentrations in the ocean are not buffered in the same way that CO2 is as part of a complex series of chemical equilibria.

Oxygen behaves as a nearly ideal gas, whose concentration is controlled by Henry's Law and currents, the currents determining how well mixed it is, and among other things the depth profile.  For those who forgot, Henry's Law says that the concentration of gas well mixed into a liquid, C, is proportional to the partial pressure of the gas above the liquid, p,

C = k(T) p

where k(T) is a function of the temperature and the molecular identity of the gas.  For the purpose of this post, all one needs to know is that as temperature increases k(T) decreases, so the concentration of the gas in the liquid decreases also.  The van't Hoff equation can be used to calculate k(T).

ADDED: To provide an idea of how the maximum concentration of oxygen in water varies with temperature, the figure to the right shows the non-linear nature of the van't Hoff equation

In Science Deutsch, Ferrel, Seibel, Poertner and Huey, work out the consequences of a warming ocean on the ability of fish to breathe.
Warming of the oceans and consequent loss of dissolved oxygen (O2) will alter marine ecosystems, but a mechanistic framework to predict the impact of multiple stressors on viable habitat is lacking. Here, we integrate physiological, climatic, and biogeographic data to calibrate and then map a key metabolic index—the ratio of O2 supply to resting metabolic O2 demand—across geographic ranges of several marine ectotherms. These species differ in thermal and hypoxic tolerances, but their contemporary distributions are all bounded at the equatorward edge by a minimum metabolic index of ~2 to 5, indicative of a critical energetic requirement for organismal activity. The combined effects of warming and O2 loss this century are projected to reduce the upper ocean’s metabolic index by ~20% globally and by ~50% in northern high-latitude regions, forcing poleward and vertical contraction of metabolically viable habitats and species ranges.
There is an editor's summary which puts this a bit more forcefully
It is well known that climate change will warm ocean waters, but dissolved oxygen levels also decrease as water warms. Deutsch et al. combined data on metabolism, temperature, and demographics to determine the impact of marine deoxygenation on a variety of fish and crustacean species (see the Perspective by Kleypas). Predicted climate and oxygen conditions can be expected to contract the distribution of marine fish poleward, as equatorward waters become too low in oxygen to support their energy needs. Furthermore, even the more-poleward waters will have reduced oxygen levels.
Deutsch and co. looked at how the oxygen content would shift populations of cod, seabream, eelpout and rock crab.  They define a metabolic index Φ as the ratio of the available partial pressure of oxygen to the oxygen needed by a resting sea critter. When Φ = 1, about all a fish can do is float.  OTOH, for Φ < 1 the fish has to go somewhere else to be able to survive.  The figure below shows how this shifts under RCP 8.5 in 100 years from the generic 2000 to 2100.

To concentrate the mind, this is just a map of what happens because of a decreasing concentration of oxygen in the oceans, not changes in pH, pollution and other things.  This is also for the oceans, where there is a place to go.  Aquatic life in lakes and rivers can't for the most part pull up the moving van, and there are indications that the same sort of deoxygenation is happening there.  Consider the implications of "Globally significant greenhouse gas emissions from African inland waters" by Borges, et al.

ADDED:  Victor V at Variable Variability has more on how lakes are warming worldwide.  The implications for the things that live in them are not good unless fish are planning to grow legs.


Bernard J. said...

The combination of hypoxia and thermal tolerance is worth dwelling on.

During my transition from immunological to ecological research I worked on a project involving rainbow trout. The beasties were kept in a huge insulated cool room in what were effectively swimming pools, in an otherwise warm temperate climate. On several occasions the refrigeration equipment packed it in, and the ambient temperature rose from 13-14 °C to 18-20 °C.

At around 18 °C the level of dissolved oxygen really started to plummet, especially as the water was also full of distressed fish. It's astonishing how at around 17-18 °C the fish went from showing essentially no signs of discomfort, to being fillets destined for an unscheduled lab dinner after a few more °C increase.

It's something that is difficult to convey without watching the process occurring, with all the attendant angst arising from the invested research work and the ability of high-tech equipment to monitor the progress to catastrophic failure over what is a subtle change in environmental parameters.

It's instances such as these, in addition to mapping natural distributions of many species, that make me aware of how tenuous are the existences of our biosphere's inhabitants in their respective bioclimatic envelopes. Sadly, I suspect that too many humans will learn this lesson when it's far too late to have the refrigeration fixed.

Tom said...

You're joking, not choking. Do the math.

Victor Venema said...

The oceans are warming slowly because they have such a large heat content, lakes are normally shallow in will respond much faster to warming.

Oceans are surrounded by water that warms less (more of the additional heat goes to evaporation, rather than to warming the water or air) and thus also warm less. What my post is about is that lakes and rivers seem to be warming faster than the air in their region, which is surprising.

However, I am not sure fish need legs. Fish that have survived in lakes for ages must have some way to reproduce in other lakes. For example by airlifting their eggs on the feet of water birds.

Barton Paul Levenson said...

What fish need is bicycles!

Sorry, I couldn't resist.

Mitch said...

Don't forget the streams--fishing for trout, salmon, steelhead, sturgeon curtailed after 2 pm in Oregonbecause of high stream temperatures and strees on fish

John said...

Of course it's great to tackle this issue using Henry's Law, and the van't Hoff equation.

But there is a simpler way:

Ask any topical fish hobbyist !!

The maximum amount of oxygen dissolved in warm water is less than the maximum amount of oxygen dissolved in cold water.

If the water temperature in the aquarium gets too high, the fish slow down and stay at the surface, gasping for air. Just ask your friendly neighborhood fish fancier about this well-known fact.

I suppose that to the climate change deniers, this proves that the aquarium owners are also part of the vast conspiracy to hide the truth about global warming...

Fernando Leanme said...

Rcp8.5 isn't feasible. I would do the figure showing something like an RCP6.3 or slightly lower.

By the way, just in case you aren't aware, USA crude oil and condensate production has peaked in the first semester of 2015. So has the non OPEC stream. The OPEC stream has increased as Saudi Arabia and supposedly Iraq fight for maarket share and try to slow down production elsewhere.

Oil prices have ranged between $50 and $60 per barrel, a price range which is clearly unsustainable for non OPEC as well as OPEC nations (OPEC nations are either suffering a lot, like for example Venezuela, or drawing funds from savings to survive the cash flow shortfall). Ten years ago $55 per barrel was enough to cause a production surge, but today it's causing a severe production slow down. This confirms we are gradually running out of oil, and cases like RCP8.5 are pure fiction.

Victor Venema said...

Fernando Leanme said: "Rcp8.5 isn't feasible."

It is nice that you think that your political movement is losing, but RCP8.5 is still the scenario of the people who claim that CO2 is life, that we cannot lift people out of poverty without centralised coal power plants, that warming is positive, that any modernisation of the energy system would lead to a a fall back to the middle ages rather than to more prosperity and health.

Most of the CO2 emissions in that scenario come from coal and lignite. Oil is much too expensive. Still it is encouraging to see Saudi Arabia as the lowest cost producer dump its oil, fearing they would otherwise not be able to sell it any more because renewable energy becomes too cheap.

Sam said...


It is highly unlikely that Saudi are "dumping their oil" because they're worried about electric cars and solar. To understand their actions one must instead look at their experiences in the late 70s, when Saudi Arabia very nearly exited the oil extraction game while trying to prop up the oil price by making production cuts. They got very badly burned, and it probably left a scar. No way they'd take the same course of action in the face of another price collapse.

Mitch said...

In a complex situation, look for multiple pathways that lead in the same direction. I think the Saudis are aware that oil is likely to be a stranded asset. At the same time, they also want to maintain their market share. Also, they want to reduce the amount of oil use in their own economy. So, they lower the price to drive out expensive oil and increse market share, and they also PV their own economy to bring that oil onto the export market. Peak oil happens when other resources can provide the same energy at comparable or cheaper prices, not when we run out of oil.

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