Wednesday, September 18, 2013

An Unplanned Model for Climate Change

On a recent Sunday, Animal Caretaker Chris Russell checked the temperature of our Puget Sound Salt Water Tide Pool, as he does every morning. But today something was different. The temperature had risen to 19 degrees C (66° F) and there seemed to be no sign that our chiller was trying to fix it. The circuit had tripped. Resetting it proved to be a Band-Aid solution. The next day it had tripped again.

Pacific Science Center’s tide pool touch tank is a recirculating water system. Unlike waterfront aquariums, we do not use naturally occurring seawater, but instead formulate our water from a synthetic salt mixture. This gives us a more consistent product unaffected by rain, pollution, etc. However, we are at the mercy of our equipment. If our hand rinsing sink failed, and kids touched our water with soapy or lotion covered hands, we would notice an immediate decline in the health of our animals. When our protein skimmer goes on the fritz, we quickly lose water quality.

When our chiller stops working, it is an emergency.

Although Seattle’s weather is mild, fluctuating from occasional 90° days to weeks of freezing weather in winter, the water temperature of Puget Sound ranges from a low of 6.7° C (44° F) in winter to a high of 13.3° C (56° F) in summer. We maintain the water in our tide pool within this range of temperatures.

In a natural setting, the temperature of the water is influenced by the air around it, and by the temperature of the tributary rivers feeding the Sound. At Pacific Science Center, the warmth of human hands touching the water significantly changes our tide pool’s temperature. The many people who learn about our animals by touching them act as a sort of radiant heat source, so that the tide pool is often a couple of degrees warmer at the end of a busy day that it was that morning.

But the good old chiller is supposed to take it back down to the colder end of things overnight so it’s ready to go again the next day. Without its help, the water would eventually rise to room temperature!

At the warmer temperatures, the animals seemed relaxed and comfortable. The anemones were open, clear looking and glossy. The sea stars ate well, and several started spawning. The fish were more active than usual. All of this sounds great. Why not just keep the water warmer?

Of course, the longer-term impact of warmer water wouldn’t be as positive for the animals. Warmer water holds less dissolved oxygen and more algae growth. If too much algae flourishes, its decomposition strips yet more oxygen from the water and can lead to serious problems for the animals.

Lower oxygen levels harm the ability of animals to resist disease and pollution. So when waters warm, animals that appeared healthy may start succumbing to preexisting disease, or may develop problems from injuries that would normally be very minor. Animal’s behavior also changes as they seek more oxygenated water. In the wild, they might migrate to deeper water or to areas with pockets of trapped cold water, or populations might start trending further north. In the tide pool, animals would seek oxygen near the water’s surface, even though it was warmer. As normally deep-water creatures moved to the surface, competition for good spots would lead to more animals fighting and injuring each other.

Luckily for our tide pool, these problems did not have time to express themselves. Our chiller had a bad circuit.Once Douglas Hall, our electrician, replaced it, temperatures quickly returned to normal.

There is no such quick fix for the climate changes that are raising the temperatures in Puget Sound. But understanding the risks, from a mini-model such as our touch tank, can make it all the more clear why it’s important. Reducing carbon emission is the best way to slow the rise of sea temperature, but keeping beaches otherwise healthy and intact – free from polluting runoff or from overuse – is also critically important. Resilient animals will be best able to withstand, adapt, and survive in a rapidly changing environment. Intertidal life, with its tides, fresh water feed, and periodic predation by shore life, is by nature challenging. Human intervention should aim to minimize the added challenges we throw at these already hard working systems.

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