How are fish adapting to ocean warming?
The team, led by Dr Masayuki Ushio, Assistant Professor of the Department of Ocean Science at the Hong Kong University of Science and Technology (HKUST) and Dr Masaki Miya at the Natural History Museum and Institute, Chiba, Japan, has developed a new technique to quantify the interactions between different fish species, known as interspecific interactions. These interactions are thought to be key to understanding and predicting the dynamics of ecological communities. The findings have been published in eLife.
Croucher News caught up with Ushio to find out more. He told us that the team used environmental DNA (eDNA) and advanced statistical analysis to detect the presence of fish species and reveal how they interact with each other. Ushio, talking to Croucher News, explained that eDNA would be present, along with many invisible microorganisms, in any sample of seawater. “Imagine a swimming pool”, he said. “It’s going to be full of human DNA. In a similar way, the ocean is full of the DNA of the fish and other creatures who live there.”
Previous eDNA studies have mostly been limited to detecting the presence or absence of certain species. However, this new technique estimates the quantity of fish species and detects the interactions between species by analysing the high-frequency eDNA time-series data using cutting-edge time-series analysis methods. These interspecific interactions, such as prey-predator, competitive, and mutualistic relations, have a significant impact on ecosystem dynamics.
The researchers set up 11 study sites along the coast of the Boso Peninsula in Chiba Prefecture, Japan, where they conducted biweekly water sampling for two years. “I didn’t get out too much on the boats myself,” laughed Ushio. “After years of land-based research, I guess I am still finding my sea legs!”
Ushio has been in Hong Kong for about a year and has found that the city has lived up to his expectations as a great place to do science. “The support you get from the wider team here at UST is just excellent”, he told us.
One of the important findings from their research was that water temperature can have both positive and negative effects on how different fish species interact with each other. They also found that different fish species can react differently to changes in temperature, shedding light on how global warming can impact the complex relationships between fish species in coastal areas. “The big surprise for me was that warming does not always mean more interaction - sometimes it seems to give rise to less”, Ushio told Croucher News.
The framework can be used to study interactions between different types of organisms, not just fish. This includes microbes, crustaceans, and other invertebrates. For example, scientists could use the technique to study how different organisms interact in aquaculture systems. It could also help identify potential harmful pathogens that could impact commercially important fish species.
In the long run, this research could help scientists and policymakers better understand how climate change is impacting fish populations, including commercially important and rare species.
“To achieve these ambitions, scalability is really important,” Ushio told us. “To help with that, we are exploring new technologies, such as automated water sampling systems and seawater sampling with underwater drones, to make eDNA analyses more efficient and effective.”
They also plan to use advanced DNA sequencing technology to investigate eDNA sequences in more detail, such as with long-read sequencing. “I’d love to be able to give accurate predictions of the likely impact of a warming ocean on different species. This is really important for us to be able to develop better conservation strategies to protect these species and ensure the long-term sustainability of oceans,” said Ushio.
And the team is aware of the growing sense of urgency around climate change: “The oceans seem to be warming even faster than expected. I think as scientists we feel the pressure to deliver useful results at this time of increasing climate anxiety.”