Negative image of plankton from the North Sea.

Observing plankton: microorganisms and our changing oceans

1 November 2016

As a budding environmental scientist, Dr Karen Chan (Croucher Fellowship 2012) thought she would go the ‘usual’ route of whales and dolphins. A college internship saving dolphins in the Mekong River in Cambodia put that dream to rest. “It’s very sad, and makes you feel incredibly helpless when you can’t save them. It takes a special strength to do that day in and day out, but I had to find another way to be involved with conservation,” she says.

Chan found this way in a coastal ecology professor’s casual explanation about how barnacle larvae drift into the ocean for an unknown amount of time, eventually returning with a totally different shape. “Well, wouldn’t you want to know what happened during that time?” she asks.

To answer questions like this, Chan studies ocean conditions, from acidification, salinity, heavy metal presence, and other measures of climate change. The ultimate question deals with how fluctuation in native environments helps animals adapt to environmental stressors, which is where Chan’s invertebrates come into play. 

“Hong Kong is an interesting place for this work because of the high levels of human activity, freshwater input, and variation in environment,” she explains. 

Animals like sea urchins, snails, and oysters collected from the field are put into future scenarios in the lab, such as more saline or warmer water, to understand which stressor has what impact on the animals. 

For example, sea urchins, a traditional model species in development biology for their importance as grazers and ecosystem engineers, usually clone themselves when stressed. In more acidic environments, they often fail, ending up with conjoined larvae. Down the road, Chan hopes that this research will help inform better policy for marine conservation and resource management, but recording species’ locations and preferences is still underway.

Microbeads in the ocean

Chan’s lab also tackles contemporary issues such as microplastics. Microbeads, popular in beauty products, were recently banned in the US and other countries because of the dangerous effects on marine animals ingesting them, but no similar study or initiative is underway in Hong Kong. 

The project originally emerged from an undergraduate student at the lab who had been following the policy and industry developments against microbeads. It started small, seeing how many plastic beads were in daily products in Hong Kong (answer: tens of millions). 

Dr Karen Chan

Then the lab turned to their trusty litmus test, conducting plankton sampling which determined that they do indeed find and eat the beads, turning the question into one of the long-term effects on marine life. 

“This is a new question for us even compared to the studies that have already been done on microplastics,” Chan says, “We know they’re eating them, we know what happens to them in the short-term, but as adaptive animals, we’re now asking what the lasting effect on their development might be.” 

The testing is broadened for this project, including sea urchins and snails, which are endangered species in Hong Kong. Preliminary findings show that if snails eat plastic as babies but not as juveniles, they get smaller and grow slower. The lab is currently testing out the hypothesis that the plastic’s chemicals are absorbed in a certain way, or that the snail’s filter feeding habit means they pump more water because of higher particle content, and therefore do not eat as much.

Another aspect of Chan’s work is a biodiversity survey of the eastern waters of Hong Kong, partially supported by the government. Her team runs a monthly plankton survey at two sites to understand community composition, how the community changes over space and time, and identify commercially viable organisms such as shrimp. 

Large water samples are collected and studied under microscopes in the lab, with some unexpected surprises, such as a jellyfish which has been adopted as the lab pet. “Even though Hong Kong is small and urbanised, there’s a lot of marine diversity. We never know what we’ll get in a sampling, and it helps us appreciate the impact of the work we do.”


The lab’s fourth project studies the biomechanical evolution of marine invertebrate larvae and what factors contribute to changes in shape. Adult invertebrates have a drastically different shape from their larval forms, driven mostly by adaptation for survival, and therefore follow distinct evolutionary patterns. 

Different animals have specific larval shapes, and holds important keys to their evolutionary history and function. Looking at more than 100 species of barnacles, the lab found that frontal horns, only present in the larvae stage, change in aspect ratio according to whether they need to eat. 

The frontal horn is surgically removed from barnacle larvae to view development from a morphological perspective—without x feature, does y function still take place. Traditionally, the horn was considered just a gland, but Chan’s team argue that it increases drag, allowing things to stick and enable easier feeding. 

This is observed by putting a high-speed video lens on the tiny surgically de-horned larvae swimming about in a carefully recreated environment, documenting every slight particle disruption. Chan is quick to reassure that “no baby barnacles are harmed in the process,” and that their horns are (painstakingly) reattached afterwards.

Focusing on the most overlooked marine invertebrate larvae may seem like an odd choice, but Chan points out that their crucial presence in most marine ecological systems remain uncharted waters. Many animal diets rely on plankton, so their movements also impact how populations change. 

Protecting the food source is a first step for conservationists, who need to know when and where to find larvae to pick a site best sourced for animals. This helps protect spaces more thoughtfully than just drawing lines on a map, and encourages more comprehensive public policy. Chan mentions the Channel Islands project, which mapped habitats, studied organisms’ reproduction cycles, oceanographic studies on plankton larval migration, and produced an ecological connectivity map.

Plankton plasticity also allows them to adapt under various circumstances, but there are very few experiments that have found definite proof of adaptation, though Chan’s work has seen different responses and the negative impact of recent climate change stressors. 

“The good news is that selective pressure will lead to evolutionary adaptation, but the bad news is that the marine ecosystem will never be the same because no two organisms respond in the same way,” she says. 

Studying a highly available and adaptive organism like plankton can yield valuable insights on how they interact with their environment, how they move, what kind of signals they transmit, what they eat and who eats them, and then looking at how to manage human behaviour on these ecosystems.

Oceanography studies the idea of dispersal, and is interdisciplinary by nature. Chan asks ecological, evolutionary questions and solves them by using imaging, engineering tools, math, and chemistry. 

“Take just one project, how sound affects developing larvae: I work with an acoustician for different sound wavelengths, a physicist for numerical simulations, and engineers to mimic water movement. Breaking down the walls means using more than one technique,” she notes. Outside the lab, she and her colleagues work with people on the ground for more direct applications, including NGOs, policymakers, the public, and others.


Though scientists are trained to be impartial, it can be difficult in some matters, and Chan welcomes the new trend of scientists as advocates as a necessary change. “Part of what I teach is the science of climate change, but how I approach and present that is equally important,” she says. 

More interest in and support for understanding the impact of climate change is reflected in her research wish list. This includes a closer look on larvae function, “a simple but surprising life stage”. Also high up is a catalogue of Hong Kong plankton and a mechanistic understanding of their reaction to climate change, which they have been adapting to for aeons, to develop a baseline for measuring future change.

Public perception of climate change is also slowly changing with the advent of extremely hot summers and strange weather patterns, but Chan notes that most people have yet to think of it within the context of how daily life impacts and is impacted by such changes. 

Policy-wise, Hong Kong must also strike a balance between environmental conservation and much-needed development. Establishing a baseline by using organisms who have managed to adapt can help achieve that balance and measure impact.

The Hong Kong scientific community is busy laying the groundwork for a more collaborative approach down the line. Briefly, this plan consists of three steps: looking at stressors together and separately and building more integrated mimic systems; understanding the response mechanisms and translating this to other stress responses; and integration of the public and policymakers into the action and prevention conversation. 

“We’re doing a lot of community outreach, but for any difference to happen we need more engagement and buy-in, which is why scientist-advocates are so important,” Chan explains. “Staying in the lab and doing research just isn’t enough in environmental science today—we need to engage with the community and stakeholders.” 

There are encouraging steps being taken, as with the new Biological Diversity Strategic Plan due in the next few months, which has seen increased buy-in from the public and policymakers. Growing up in Hong Kong, Chan has fond memories of family hikes and beach outings, and credits this closeness with nature for her career in environmental science. “Our island has such rich biodiversity, and I hope more people see the value in preserving and cherishing it. Every little change we can make can contribute to bigger ones—much like plankton.” 

Dr Karen Chan received her BSc with first class honours from the University of Hong Kong in Environmental Life Science in 2006. She then moved to Seattle to pursue her MSc and PhD in Oceanography at the University of Washington under the supervision of Dr Daniel Grunbaum. Her dissertation research focus on the consequences of ocean changes for ecological functions of marine invertebrate larvae. Chan received a Croucher fellowship in 2012 to study at Woods Hole Oceanographic Institution.

To view Chan's personal Croucher page, please click here.