Earlier this spring, a team of research technicians from the Hakai Institute (Hakai) and the University of British Columbia (UBC) made the trip over to Mayne Island to install a set of settlement plates in a rocky area of the intertidal zone. The site on Mayne Island is one of six sites established this year across the Salish Sea, and is part of an 18-month long pilot study to investigate how rocky intertidal communities are responding to our changing climate.

Why is this important?

By nature, the intertidal zone is a highly dynamic environment.  Interfacing land and sea, this important section of shoreline is exposed to constant and extreme fluctuations in physical and chemical variables – including salinity, humidity, and temperature – as the tides rise and fall throughout the day. As a result, the organisms that make up intertidal communities have evolved over millions of years to withstand the constant changes inherent to their environment. Like all living things, however, these communities have their limits.  In recent years, heat waves and cold snaps have made the news, as century-long records have been broken time and time again. As our climate changes, these extreme weather events are expected to become more frequent and more intense across our coast, and their effects are widespread. As tides fall and shorelines are exposed to the outside air, organisms in the intertidal are left unprotected by the buffered environment provided by the ocean. While some creatures, such as crabs and snails may seek refuge in cool, moist crevices, sessile organisms (organisms that are unable to freely move about), such as barnacles, mussels, oysters, and seaweeds, rely solely on their ability to tolerate their environment. This inability to retreat to safety means that many intertidal organisms are vulnerable to extreme temperature events, which are an increasingly common reality.

How are we studying thermal tolerance?

To better understand how intertidal communities are responding to these events, scientists at Hakai and UBC have developed an experiment using artificial settlement plates designed to manipulate temperature. At each of the six sites selected for this experiment, eight pairs of black and white tiles are installed in the mid-intertidal zone of rocky shorelines. In the center of each of these tiles is a small epoxied square where organisms may settle during their larval stages and grow into adults. The different coloured tiles will heat up at different rates, with the black tiles ranging from 2-6°C warmer than the white tiles, and temperature data will be recorded by a series of small data loggers found inside of the tiles. Community partners and technicians from Hakai and UBC will work together over the 18-month study period to capture images and record coverage of species on the tiles. This will allow researchers and communities to gain a better understanding of the effects of warming on invertebrate settlement and succession, and how our local intertidal communities may shift as our climate changes. The Black and White Tile experiment is part of a larger project, Sentinels of Change, driven by communities and scientists across the Salish Sea to study local biodiversity, and how our coasts are changing alongside our climate. If you would like to get involved or learn more, please feel free to reach out to the Sentinels team at sentinels@hakai.org, or visit the Sentinels of Change website!

Settlement plates for the Black and White Tile experiment installed in the rocky intertidal at the site on Mayne Island, BC.
A diagram illustrating the construction and components of a pair of settlement plates in the Black and White Tile experiment

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