Tonight, my great and good friends of the Secret Science Club are presenting a topical lecture by marine ecologist and zoologist Dr Christopher Harley of the University of British Columbia at Vancouver, who made the headlines recently when he discovered the mass die-off of tidal organisms due to the recent PNW heatwave. Dr Harley's website is a good resource for coastal ecology.
Dr Harley began his lecture by thanking Margaret and Dorian for a chance to step back from frantically cataloging the damage done by the heat wave, with the assistance of his student. He titled his lecture 'Well that Stunk', describing the die-off as a pungent event... if someone had dumped a wheelbarrow of mussels on your front lawn, and they rotted for a few days, you'd get some idea of the stench. This was an unprecedented event in the PNW. A friend of his described it as the new smell of climate change
Why should we be concerned about climate change? There are a lot of things we care about that are effected by it? Dr Harley cited such organisms as red sea urchins and abalones, which are valuable commodities. Kelp and sea grass are secondarily important- they provide habitats for organisms and protect the coasts from wave erosion. He also cited the wonderful biodiversity in the tide pools of the Pacific- he was hooked into marine biology by hermit crabs. As a human, he gets a charge out of nature, and will work to preserve it.
Rocky shores, and marine benthic systems in general, are ideal for studying the effects of climate change. These coastal organisms already live at the limits of their environments. The interactions of the organisms in this environment are important- organisms such as mussels and barnacles compete for space, sea stars clear mussels to provide niches for barnacles. The combination of environmental and predatory factors results in patterns- there are usually bands of shellfish beds, kelp beds, and grassy areas. These bands can be studied to determine changes, such as temperature changes.
There is a zone where the horn of plenty algae thrives, typically between a layer where the barnacles thrive and where the mussels and grazers thrive. The algae can be moved higher up where the barnacles are, but it will die of lack of hydration. Moved lower, the grazers will devour it. Studying the upper limit of the horn of plenty on Tatoosh island, it was discovered that the limit was stable until about 1993, then dropped, stabilizing at a lower level around 2000. Successive summers of excessive temperatures caused this change. Around 2005, the limit lowered again due to heat exposure. Is the limit dropping, or is it being squeezed, possibly to nothing?
In the 1950s, a marine botanist named Tom Widowson measured the different bands of organisms on the coast. Dr Harley obtained his doctoral thesis to obtain old data, he joked that the thesis "smells like old knowledge", Dr Harley was put into contact with Dr Widowson, who game him Google map coordinates for all of his research sites. He was able to correlate the upper limit of the barnacles and the upper and lower limits of mussels with temperatures, and found that the upper limits of both barnacles and mussels were lower, but the lower limit of the mussels didn't change much, so the habitat of the mussels has been squeezed to about half of its former extent.
Climate change has been going on for a long time, and organisms have been responding to it. Without the data of scientists such as Dr Widowson, these changes might not have been apparent. Climate change is well underway, what can we expect next? Organisms can be brought to labs, and temperatures can be manipulate to see what temperatures will kill them. Dr Harley prefers field work, he studies organisms in a system. One study involves the use of black and white tiles to manipulate temperatures on a micro level (white reflecting light, black absorbing it). On a larger scale, heat can be provided by propane camp heaters, which are suspended over seaweed beds to raise temperatures. In another study, propane turkey fryer kits were used to warm up tide pools.
In general, these experiments warm areas three degrees Celsius, the extent to which the climate is predicted to be warmer by the end of the century. What should we expect to see happen to these organisms in eighty years. With the heat wave in June, Dr Harley wasn't prepared for the die-off. On the first day, he was on a science outreach boat trip, and on visiting a beach, didn't think to photograph the mussel beds. On the second day, he smelled it before he saw it, and knew that a tragedy was unfolding. On the third day, he went out with a grad student, and the conditions were unsafe for working under sunny conditions. While the air temperatures spiked to over 100F, exposed organisms on coastal rocks baked. Temperatures were 28C above normal, high temperature records were shattered. In Lytton, BC, the all-time temp record was shattered by 8 degrees- these records are usually shattered by fractions of degrees. On the coast, rock temperatures were measured at 52.5C (126.5F). On the black mussel shells, he obtained temperatures of 134F (56.7C).
Dr Harley did not foresee this occurrence. He walked, crunching on dead organisms, over the cemetery of an ecosystem he loves. He showed a gallery of the slain- mussels, crabs, whelks, clams. Barnacles (he joked that they look like James Bond villain lairs, being 'little volcanoes with trapdoors that reveal the feet, not doomsday devices) suffered incredibly. Mussels were the poster children of the die-off. Dr Harley showed a picture of dead mussels, still full of meat. Thermal images showed temperatures ranging up to 56.7C (134F).
Dr Harley noted patterns. Near his house, the carnage was relatively light- only about 20% of the mussels died. It was a north-facing beach with small mussels. One of the worst hit areas was a mussel bed on Galliano Island. The angle of incoming sunlight played a role in the die-off, with 90 degree angle sunlight being particularly deadly. Mussels in the shade were safe. The coastal seaweed was also affected, rockweed (bladderwort) was killed. The rockweed provides habitats for other organisms.
How extensive was the die-off? Dr Harley and his team is expanding the scope of the initial study, along with scientists in Washington, indigenous foragers, seafood harvesting companies. The Strait of Georgia, and Puget Sound were hit hard. San Juan Island was relatively unscathed. Inland waterways without access to cold water were hit hardest. There are a lot of gaps, so information has to be collected.
How many animals died? Dr Harley showed a picture of 100 dead barnacles, easily fitting in the palm of his hand. He calculated the amount of good barnacle habitat in the Strait of Georgia, and determined how many dead barnacles could have died, perhaps ten billion dead barnacles. With the mussels, snails, worms, and crabs that live in these habitats, Dr Harley is certain that billions of animals died.
Was there any good news? Hermit crabs might be one of the few winners in the short term- they are mobile enough to avoid dangerous conditions, they had a real estate boom, they are scavengers so they feasted, and they are subject to temperature sensitive parasites which might have died. Other species, such as sea grass, certain clams and oysters, and sea anemones, did okay. Some mussels had refuges, sea stars did okay.
What are the ripple effecs of the die-off? Migrating birds like the surf scoter rely on mussels, will they have enough this winter when they fly through? What abut juvenile salmon that need cover? Without filter feeders, will water quality be impacted?
What are the long-term prospects for the BC coast? Fast growing species with good dispersal, such as barnacles and mussels, may recover in a few years. Rockweed may take longer. The problem is that heat waves will be more common. Species from warmer waters will have a hard time dispersing up the coastline, but invasive species from Asia will thrive. The ecosystem may soon look more like Southern Japan than California.
What can we do? We can pressure politicians to fight global warming. We can make choices to conserve energy? Local conservation efforts can be formed, allowing better chances for regeneration.
The lecture was followed by a Q&A. The first question regarded food shortages. Local indigenous groups will face serious food insecurity risks due to die-offs. Droughts on the prairies would be more dangerous on a global scale. Which is more ecologically dangerous? Changes in average temperature or changes in highs? Changes in average temperature should effect growth. Max temperatures are more significant in mass death events. Eelgrass and kelp are prime habitats for larval organisms, anything which adversely effects them pose dangers to the food web.
Dr Harley stated that working with physiologists is helpful- he is working with researchers studying Dengue fever and notes that the information he obtains studying the rocky coast has utility to studying the African savannah.
What can citizen scientists do? Simply taking photos can help scientists determine the limits of where organisms live. There are more citizens than scientists. People have been contacting him about preservation efforts, such as cloth tents to shade mussel beds, or using pumps on boats to mist coastal areas- these efforts just aren't practical for protecting wide stretches of coastline.
Why not seed species from the south by hand? This is being done with forests- southern genotypes are warmth adapted. Marine larvae are more mobile, so this hasn't been discussed as much. This assisted migration is risky, such as the introduction of cane toads to Australia.
Climate change is providing selection pressure, on an evolutionarily significant scale, which will most likely result in lower genetic diversity. Dorian joked about a 'planet of the hermit crabs' situation.
Some bastard in the audience asked about ocean acidification- he has studied this subject for years, using turban shell snails as a subject- the shells have yearly growth rings, and the snails are growing slower in acidified conditions. Oyster larvae are sensitive to ocean acidification, which worries oyster farmers. The acidification and temperature change could form a one-two punch. The die-off has ensured that his grant money in the foreseeable future will fund warming research.
Another question involved the benefits to invasive species from global warming- most boats coming into British Columbia arrive from warmer ports, so warming gives them an advantage. Also, if native organisms are continually shocked by disasters, they are less resistant.
Another questioner asked about the dangers of seafloor mining- there are manganese nodules on the ocean floor which can be dredged up. This poses danger to poorly known ecosystems such as glass sponge reefs. Can it be done in an environmentally responsible way? This requires a lot of study.
The final question was, how screwed are we climactically? Can coastal ecosystems recover? He recounts students coming up to him with tears in their eyes. The oceans will go on without us, but they won't look like they do now. Coral reefs are forming in the Carolinas, the Mediterranean is looking more like the Red Sea. Ecosystems are resilient, warmth adapted organisms will expand their ranges. Dr Harley is hopeful, but things are changing fast, and it would be nice to apply the brakes.
Dr Harley's lecture was entertaining and informative, and it was most certainly topical. Kudos to Dr Harley, and Dorian and Margaret for another fantastic Secret Science Club presentation. Here is a news presentation which encapsulates the heart of this lecture:
It was a sobering lecture, delivered by an engaging lecturer, which is a perfect example of the Secret Science Club experience.