Deciphering fish species interactions for climate change insights
IMAGE: ONE OF THE 11 SITES WHERE EDNA SAMPLING WAS CONDUCTED (TOP LEFT; ROCKY SHORE IN MERA IN CHIBA, JAPAN). THE COLLECTED EDNA SAMPLES WERE ANALYZED USING A DNA SEQUENCER TO OBTAIN EDNA TIME-SERIES DATA (BOTTOM LEFT). THIS DATA WAS THEN ANALYZED USING CUTTING-EDGE TIME-SERIES ANALYSIS METHODS TO ESTIMATE FISH-FISH INTERACTIONS (RIGHT FIGURE; ARROWS INDICATE INTERSPECIFIC INTERACTIONS). view more
CREDIT: HKUST
A team led by the Hong Kong University of Science and Technology (HKUST) has developed a technique to study how different fish species interact with each other in a coastal region, a breakthrough that helps explain the complex relationships among marine species and how global warming impacts fish populations.
By analyzing minute traces of fish DNA from samples of seawater, the team combined the use of environmental DNA – known as eDNA – and advanced statistical analysis to not only detect the presence of fish species, but also reveal how the species interact with each other.
The use of eDNA to monitor biodiversity has surged in popularity in recent years, particularly for detecting aquatic organisms like fish. As animals move through their environment, they shed fragments of genetic material, such as skin cells, waste products, and other body fluids. By extracting these traces of DNA from samples of water, soil, or air, scientists can determine the presence and diversity of species with high accuracy.
But previous eDNA studies have mostly been limited to detecting the presence or absence of certain species. To get a better understanding and monitoring of ecosystems, it is necessary to estimate the quantity of fish species and detect the interspecific interactions, or interactions among species.
The team, led by Prof. Masayuki USHIO, Assistant Professor of the Department of Ocean Science at HKUST and Dr. Masaki MIYA at Natural History Museum and Institute, Chiba, Japan, developed a new technique to achieve the abovementioned purpose by analyzing high-frequency time-series data from fish eDNA, making it possible to comprehensively monitor interactions among species.
Interspecific interactions, such as prey-predator, competitive, and mutualistic relations, have a significant impact on ecosystem dynamics. The research paves the way for scientists to contribute to more accurate assessment of the ecosystem status and future predictions of its dynamics.
The researchers set 11 study sites along the coast of the Boso Peninsula in Chiba Prefecture, Japan, where they conducted biweekly water sampling for two years. They extracted eDNA from the collected samples and analyzed fish communities using a method which generated the eDNA-based high-frequency time series of fish communities in coastal ecosystems. Then, they detected and quantified the strength of fish-fish interspecific interactions in the communities by analyzing the high-frequency eDNA time-series data using cutting-edge time-series analysis methods.
Among their important findings 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 findings were recently published in international academic journal eLife.
“By integrating state-of-the-art techniques from different scientific fields, we showed that eDNA analysis can estimate not only ‘what’ and ‘how many’ species are present, but also ‘who interacts with whom’”, Prof. Ushio says.
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, he said the research could help scientists and policymakers better understand how climate change is impacting fish populations, including commercially important and rare species.
“This information can be used to develop better conservation strategies to protect these species and ensure the long-term sustainability of oceans. For example, to conserve a rare species, it may be important to also protect a fish species that has a significant impact on the rare species,” he says.
The team will soon explore new technologies, such as automated water sampling systems and seawater sampling with underwater drones, to make eDNA analyses more efficient and effective, to further our understanding of how organisms interact with each other in nature, such as how pathogens impact fish populations.
They also plan to use advanced DNA sequencing technology to investigate eDNA sequences in more detail, such as with long-read sequencing.
“By utilizing these new technologies and collaborating with experts from different fields, we can continue to advance our understanding of how climate change impacts marine ecosystems, and develop better ways to protect them,” he says.
JOURNAL
eLife
ARTICLE TITLE
Temperature sensitivity of the interspecific interaction strength of coastal marine fish communities
ARTICLE PUBLICATION DATE
11-Jul-2023
The incredible journey of clownfish larvae: Mini athletes, maximum performance
Scientists study how thyroid hormones coordinate the transformation of anemonefish larvae into adults and support their survival in the wild
Peer-Reviewed PublicationIMAGE: CLOWNFISH LARVAE AT 6 DAYS POST HATCHING MEASURING 4 MM. view more
CREDIT: DR. NATACHA ROUX
Marine fish larvae can be compared to athletes who must perform if they want to survive. The success of their journey, and transformation from larvae to adults, a process known as metamorphosis, is crucial for the sustainability of fish species.
Imagine you are a tiny transparent fish larva, measuring around 2 millimeters. Right after you hatch, you find yourself lost in a huge blue environment - the ocean, where your journey starts. For several days or weeks, you will have to constantly swim in unknown surroundings, find food for energy, escape predators, develop your sensory systems to orientate yourself, and achieve your main goal - finding a home, a nice habitat close to the coast in which you will be able to settle.
While you do all this, you also face growth and massive body changes as part of your metamorphosis, enabling you to become a miniature adult ready to face a new coastal environment.
How do these larvae manage the different changes that occur in their bodies during their journey? An international team of scientists have investigated the role of thyroid hormones in the coordination of the metamorphosis in a well-known marine species, the clownfish, Amphiprion ocellaris.
They have discovered a strong interaction between metabolic processes in cells – processes that help convert food into energy - and thyroid hormones during the metamorphosis of clownfish. As clownfish journey from the open ocean to coral reefs in search of a home, these interactions, which occur both in captivity and in the wild, allow thyroid hormones to coordinate changes in energy needs with available environmental resources.
The article titled “The multi-level regulation of clownfish metamorphosis by thyroid hormones” was published in the journal Cell Reports. OIST scientists Dr. Natacha Roux, Prof. Vincent Laudet, Dr. Saori Miura, Mr. Yuki Tara, Mr. Mathieu Reynaud and Dr. Agneesh Barua, collaborated on the article, together with researchers from universities in France, Taiwan and the USA.
Additionally, the researchers found that thyroid hormones were not only involved in the triggering of the metamorphosis process itself, but also have a major role in coordinating the transformation of various organs and processes that occur during metamorphosis. These processes include color vision, digestion, ossification - the process of creating new bone material by cells called osteoblasts, pigmentation, the metabolism of the larvae, and its ability to produce energy from food which changes with time as the food they consume also changes.
“It’s like a switch; we can turn on specific genes and turn them off,” Dr. Natacha Roux, a researcher in the Computational Neuroethology Unit at OIST and lead author of the article explained. “The idea was to turn off a specific gene that is known to regulate metabolism and see if it was going to impact on metamorphosis or not. We also accelerated the metamorphosis of some clownfish to check for changes in appearance.”
“We added small molecules to the water in glass containers with clownfish larvae that speed up their metamorphosis and regulate their metabolism. The fish take it in as they breathe, it binds to specific proteins in cells called receptors and changes something,” Professor Vincent Laudet, head of OIST’s Marine Ecology and Evolutionary Developmental Biology unit said. “We wanted to know if you change the metabolism do you change the metamorphosis or not, or are the two things totally separate? In fact, they are not at all separate which means the timing of metamorphosis is critical for the survival of the larvae.”
Importantly, the journey of marine fish larvae in the open ocean and the metamorphosis process are very energy demanding. Therefore, it is critical that metamorphosis occurs at the right moment both ecologically and physiologically. Fish populations can only be renewed if young larvae successfully face all these challenges and metamorphose correctly before reaching a new coastal population.
This study applies not only to marine fish but also to other animals, as metamorphosis is a common process regulated by thyroid hormones. In fact, when human babies are born, medical doctors measure thyroid hormones immediately because these hormones are instrumental for human development in early life, similar to how they affect the development of clownfish.
Creators: Natacha Roux, Vincent Laudet and Merle Naidoo
A breeding pair of clownfish in the wild sheltered by a sea anemone. In this mutualistic relationship, the clownfish provides food to the sea anemone and the anemone provides protection for the clownfish.
CREDIT
Dr. Manon Mercader
Clownfish larvae were put into glass containers and exposed to molecules that accelerate their metamorphosis and regulate their metabolism.
CREDIT
Dr. Natacha Roux
A breeding pair of clownfish i [VIDEO] |
JOURNAL
Cell Reports
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Animals
ARTICLE TITLE
The multi-level regulation of clownfish metamorphosis by thyroid hormones
Multiple ecosystems in hot water after
marine heatwave surges across the
Pacific
IMAGE: CALIFORNIA SHEEPHEAD view more
CREDIT: CHRIS HONEYMAN
(Santa Barbara, Calif.) – Rising ocean temperatures are sweeping the seas, breaking records and creating problematic conditions for marine life. Unlike heatwaves on land, periods of abrupt ocean warming can surge for months or years. Around the world these ‘marine heatwaves’ have led to mass species mortality and displacement events, economic declines and habitat loss. New research reveals that even areas of the ocean protected from fishing are still vulnerable to these extreme events fueled by climate change.
A study published today in Global Change Biology, led by researchers at UC Santa Barbara, found that while California’s network of marine protected areas (MPAs) provide many social and ecological benefits, they are not resilient to the effects of ocean warming. MPAs are locations in the ocean where human activities such as fishing are restricted to conserve and protect marine ecosystems, habitats, species and cultural resources. The study, part of a 10-year review of California’s MPA network conducted at UCSB’s National Center for Ecological Analysis & Synthesis (NCEAS), found that marine heatwaves impact ecological communities regardless of whether they are protected inside MPAs.
“MPAs in California and around the world have many benefits, such as increased fish abundance, biomass and diversity,” said Joshua Smith, who led the study while he was a postdoctoral researcher at NCEAS . “But they were never designed to buffer the impacts of climate change or marine heatwaves.”
Smith and co-authors from all over the world were part of an NCEAS working group formed to synthesize decades of long-term ecological monitoring data from California’s diverse ocean habitats. The group, co-led by Jenn Caselle, a researcher with UCSB’s Marine Science Institute, and Kerry Nickols, a professor from Cal State University Northridge who now works with the non-profit Ocean Visions, aimed to provide actionable scientific results to California’s policy makers and natural resource managers, as part of a statewide Decadal Evaluation of the MPA network. Their analyses spanned the largest marine heatwave on record, which rolled through the Pacific Ocean toward California from 2014-2016. The monster marine heatwave was formed from an environmental double-whammy – unusual ocean warming nicknamed “The Blob,” followed by a major El Niño event that prolonged the sweltering sea temperatures. The marine heatwave blanketed the West Coast from Alaska to Baja and left a wake of altered food webs, collapsed fisheries, and shifted populations of marine life among various other consequences.
As MPA managers around the world face increasing climate shocks, the extent to which MPAs can buffer the worst of these events has become an important question. The working group scientists asked how the ecological communities in California’s protected areas fared after such a severe and prolonged heatwave: Would the communities shift and if so, how? Would they ‘bounce back’ when the marine heatwave subsided? Could the marine protected areas protect sensitive populations or facilitate recovery?
To find answers to their questions, they synthesized over a decade of data collected from 13 no-take MPAs located in a variety of ecosystems along the Central Coast: rocky intertidal zones, kelp forests, shallow and deep rocky reefs. The team looked at fish, invertebrates and seaweed populations inside and outside these areas, using data from before, during and after the heatwave.
They also focused on two of these habitats, rocky intertidal and kelp forests, at 28 MPAs across the full statewide network to gauge whether these locations promoted one particular form of climate resilience — maintaining both population and community structure.
“We used no-take MPAs as a type of comparison to see whether the protected ecological communities fared better to the marine heatwave than places where fishing occurred,” said Smith, now an Ocean Conservation Research Fellow at Monterey Bay Aquarium.
The results are somewhat sobering, though not altogether unexpected.
“The MPAs did not facilitate resistance or recovery across habitats or across communities,” Caselle said. “In the face of this unprecedented marine heatwave, communities did change dramatically in most habitats. But, with one exception, the changes occurred similarly both inside and outside the MPAs. The novelty of this study was that we saw similar results across many different habitats and taxonomic groups, from deepwater to shallow reefs and from fishes to algae.”
The implication of these findings, according to Smith, is that every part of the ocean is under threat from climate change. “MPAs are effective in many of the ways they were designed, but our findings suggest that MPAs alone are not sufficient to buffer the effects of climate change.”
The key question now is what will happen in the future? At the time of this study using data through 2020, the ecological communities have not returned to their former, pre-heatwave state. According to the paper, these ecological communities shifted toward a “pronounced decline in the relative proportion of cold-water species and an increase in warm water species.” For example, increases in the abundance of the señorita fish (Oxyjulis californica), a subtropical species with warm water affinity and previously rare in central California, had an outsized influence on the shift of communities. Whether these species persist in their new locations remains to be seen.
“This study makes it clear why long-term monitoring of California’s MPAs is so critical,” said Caselle. “Some of these time series are longer than 25 years at this point and the data are critical to understanding and readying human communities for the changes occurring in our marine communities.” Continued study will show if future shifts in marine communities occur at different rates or to different base states in MPAs compared to fished areas.
Despite the limited ability of MPAs to resist the grip of the marine heatwave, they do confer benefits, not the least of which is the ability to study the complex effects of climate change in areas not impacted by fishing. As areas of minimal human interference that are regularly monitored, they present opportunities to study the response of marine ecosystems to shifting conditions and potentially tailor management techniques accordingly. Moreover, as Smith stated, “the ecological communities in MPAs are still being protected, even if they are different as a result of the heatwave. Given that marine heatwaves are anticipated to increase in frequency and magnitude into the future, swift climate action and nature-based solutions are needed as additional pathways to enhance the health of our oceans.”
Kerry Nickols adds, “With the devastating impacts of climate change already apparent, it is very important that we are upfront about climate solutions - as long as we are burning fossil fuels and warming the globe marine ecosystems will be at risk, even if they are protected from fishing.”
This paper is the first in a series led by the NCEAS working group. Forthcoming articles examine human engagement across the California MPA network, the effect of MPAs on fish populations and fisheries, and a synthesis of marine protected areas that work for people and nature.
A garibaldi fish and a diver
Kelp Bass
Kelp Bass
CREDIT
Chris Honeyman
Chris Honeyman
JOURNAL
Global Change Biology
