Kelp growing inside a climate-controlled growth flume. Credit: Varoon Pornsinsiriruk / Martone Lab
by Kristine Ho
A new scientific instrument now in operation at UBC could help us further our understanding of the oceans and climate change. Called climate-controlled growth flumes, these cabinet-sized instruments look like clear, water-filled aquarium tanks connected to a control box by two large arms, and are currently used by Dr. Patrick Martone and his lab to study kelp.
“We’re really interested in kelp development – how kelp grow, and how different factors in the environment affect their growth,” said Martone, a professor in UBC’s Department of Botany and a principal investigator on a number of projects with the Hakai Coastal Initiative. His lab, the Martone Lab, studies various aspects of seaweed ecology, physiology and evolution, conducting most of their research along the B.C. coast but also in other countries, including the United States, Japan, Chile and Taiwan.
“Using these climate-controlled growth flumes allows us to answer questions about kelp that we couldn’t out in the field,” said Martone. As their name suggests, the flumes provide a controlled environment for kelp growth where scientists can experimentally manipulate flow conditions and other environmental factors, while keeping other aspects of the environment constant. Through this, scientists can determine what causes kelp to grow in certain ways, and can also create environmental conditions that mimic the projected future state of our oceans, allowing them play out “what if” scenarios for situations like climate change.
There are only six climate-controlled growth flumes in the world, all found in Martone’s lab at UBC. Developed by Martone and a local engineering firm, Coanda, the flumes were funded by two different Canadian Foundation of Innovation (CFI) grants, while their ongoing operation is funded by CFI and an NSERC Discovery Grant.
The birth of the flumes
Martone’s idea to develop the flumes came from a study he was conducting years ago in California. After transplanting seaweeds from the field into a water table in the lab, he noticed that the specimens started to grow very differently.
“I knew that the lab environment was extremely different from their ocean environment, but I couldn’t figure out which environmental factor was inducing this change in growth form,” said Martone, noting that after being transplanted into the water table, the seaweeds received less light, stayed at a constant temperature, and experienced virtually no water motion.
“This may seem trivial, but shape change in growing seaweeds confuses ecologists and taxonomists, and can also be key to the survival of seaweeds in moving water. And we know little about that process.”
Experiments conducted “in the field”, or outside of a controlled laboratory setting, are influenced by a variety of factors. For example, kelps growing naturally in the ocean are affected by fluctuating temperatures, varied light levels during different times of day, changing pH levels, water flow or speeds in different locations, animal grazing, and much more.
“That is why I was determined to design an experiment where I could manipulate one environmental factor, like light or flow, but keep all other factors constant. In particular, the ability to manipulate flow speed and direction is huge. Not many aquaria are able to provide realistic flow conditions, making these growth flumes functionally unique,” Martone said.
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Footage of kelp in a climate-controlled growth flume, in real time and slow-motion. Credit: Liam Coleman / Martone Lab. |
The climate-controlled growth flumes allow researchers to do just that. By programming the flume with very specific instructions, they can create their desired environmental conditions, such as having oscillating flow, or having temperature in the flume increase over the course of a week, and more. The researchers can control these different factors independently to experimentally investigate what causes seaweed to grow or respond in certain ways, something that can be difficult or impossible to accomplish in the field given scientists have little control over naturally-occurring environmental conditions.
Putting the flumes to the test: How temperature affects bull kelp morphology and survival
One of the things Martone and his lab have investigated with these flumes so far is how temperature might affect the ability of bull kelp to change their morphology, or their shape, in areas with high and low water flow. Past research has shown that kelps are very adept at changing their blade shape to help them survive under different environmental conditions, but if increased temperatures interfere with this ability, kelp may fare worse under increasingly hotter waters from climate change, if not directly then indirectly.
“We know that in current- or wave-exposed areas with high flow, bull kelp tend to grow narrow and flat blades to reduce drag, making it less likely that their blades will get torn off,” Martone explained. “In areas with slow flow, however, such as in wave-protected areas, they usually grow broader blades with more ruffles. Broad blades maximize the amount of light they get, and ruffles induce flapping to help stir up stagnant water at the blades’ surface, helping with nutrient and gas exchange.”
To first understand how bull kelps’ growth is affected by temperature, Martone, his graduate student Liam Coleman and undergraduate student Varoon Pornsinsiriruk created the first thermal performance curve for the species, a graph that maps the ideal temperature for kelp growth and also the threshold temperature at which kelp growth starts to decline. The curve demonstrated that bull kelp have a broad thermal optimum, meaning the species can resist very warm temperatures overall.
Next, Martone and his lab wanted to find out if increased temperature would affect the ability of seaweeds to adapt their shapes to environments with different water flows, since seaweeds’ ability to change their shapes is crucial to their survival. To study this, they grew bull kelp blades in flumes with different combinations of water speeds and temperatures, and observed changes in the kelp’s shape.
What the researchers found was that higher temperatures might actually interfere with a kelp’s ability to change its blade shape. When temperatures were increased, all kelp tended to grow thin and narrow, even for kelp in flumes with slower-moving water which would have benefited from growing broader blades. This has important implications for climate change and warming oceans.
“While our thermal performance curve shows bull kelp can still grow in warmer conditions, we’re finding that kelp growing in wave-sheltered areas with slower water flow may still suffer. Higher temperatures interfere with their ability to grow broad blades, therefore making it harder for them to effectively exchange gas and nutrients,” Martone explained. “However, it seems that wave-exposed kelp populations, or those in fast-moving water, will be fine even if temperatures rise, because their thin blades are already suited to their environment.”
He added that if wave-sheltered areas become even hotter than wave-exposed areas due to lack of water movement, this could exacerbate the effect.
“Despite having spent so much time thinking about the ability of kelps to change shape to resist drag, our results suggested that, as the water warms, we should pay closer attention to kelp survival in calm areas,” said Martone. “Although we don’t fully understand the mechanism of shape change, we now know that water temperature affects it.”
Future plans for the flumes
These experiments are important not only for understanding how rising ocean temperatures might affect kelp, which are crucial species that provide habitat and food in many marine environments, but they also have direct applications to the growing industry of seaweed aquaculture. Understanding ideal temperatures for kelp growth and what affects seaweed morphology is useful for determining how to farm seaweed quickly and under conditions that will create a desirable shape and texture.
Another project Martone is planning to start soon involves tracking kelp development over time, starting with spores. Through this, he can determine how much of the developmental process is fixed and, conversely, how much of it depends upon environmental factors.
“We’ve also had some interest from invertebrate scientists to grow sea stars, crabs, or snails with seaweeds in these flumes for their own research,” Martone said. “All this really speaks to the versatility and potential for these flumes to investigate questions about climate change, ecology, physiology, developmental biology, and more.”
Tags: Climate change, Faculty, Fieldwork, Hakai Coastal Initiative, Hakai Institute, kelp, NSERC, Ocean ecology, Research