Ocean Acidification

High-speed imaging reveals how oyster larvae’s dense shell helps them feed—and may offer clues to why ocean acidification threatens their survival

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Woods Hole, Mass. (September 16, 2026) — Eastern oyster larvae are only 100–300 micrometers long, but their dense calcium carbonate shells make them substantially heavier than the surrounding seawater. A new study led by the Woods Hole Oceanographic Institution (WHOI) shows that this excess weight allows gravity to drive the feeding currents the larvae use to bring food to their mouths, a finding that reveals a critical role for gravity in how these tiny animals feed and survive.

The study, published in Physical Review Fluids, challenges the long-standing assumption that larvae this small rely primarily on the drag produced by swimming to generate the feeding currents that carry food toward their mouths. While it may be true in the case of many small plankton, oyster larvae prove to be an exception, placing them in the same gravity-dominated feeding regime as much larger copepods and revealing an unexpected role for their shells in helping them feed. The key difference is that drag depends primarily on the larva’s movement through the water, but gravity depends on the difference in density between the larva and the surrounding seawater.

“This tells us that the shell is doing more than just protecting the animal,” explained Houshuo Jiang, a senior scientist at WHOI and sole author of the study. “It is actually helping the larva feed. That means anything that changes the shell could also change how the larva gets its food.”

Jiang captured the larvae’s feeding behavior using a high-speed microscale imaging system (HSMIS) developed in his laboratory. Rather than observing larvae under a conventional microscope, the system uses long-working-distance optics and a high-speed camera to record animals swimming freely in a larger volume of seawater. He also added tiny tracer particles to the seawater and used a technique called micro-particle image velocimetry to track how those particles moved around the larvae, allowing him to measure the invisible currents generated as the larvae feed.

“Usually, when you use a microscope, you need a lot of light, and if you put a lot of light on these tiny animals, you can heat the water and change their behavior,” Jiang said. “And conventional cameras are not fast enough to capture these very rapid movements. So we developed a system that uses a low-heat red LED and a high-speed camera that can record 2,000 frames per second. That lets us watch the larva in a larger volume of water without disturbing it and actually see how the water moves as it feeds.”

These findings offer a possible explanation for results from earlier experiments that raised bivalve larvae in space. In a 1999 study, scientists raised bivalves in microgravity and found that larvae reared without normal gravity tended to have lower feeding and growth rates and were in poorer condition than larvae kept under normal gravity. At the time, the physical reason for those differences was not clear.

“Thanks to high-speed imaging, we now see that gravity is essential for their feeding,” Jiang said. “If a larva is dealing with a stressor that affects its ability to build a dense shell, that could also affect the physical force that helps it feed. Understanding that connection gives us a better way to think about how environmental stressors can affect larvae at one of the most vulnerable stages of their lives.”

Oysters are particularly vulnerable to ocean acidification, which changes seawater chemistry and makes it harder to build calcium carbonate shells. This study’s findings suggest that if acidification alters shell formation enough to reduce a larva’s density relative to seawater, it could also weaken the gravity-driven feeding current it relies on to bring food to its mouth, potentially affecting young oysters.

Eastern oysters also face other challenges including pollution, disease, and overfishing. According to NOAA Fisheries’ Commercial Fishing Landings database, the commercial harvest of eastern oysters in the United States fell by about $15.2 million, or 7.2%, from 2023 to 2024.

“Ultimately, this could help us better understand what determines whether oyster larvae survive and become part of the adult population,” Jiang said. “That matters for fisheries and aquaculture because the number of larvae that survive each year helps determine the oysters available to harvest in the future. If environmental stressors affect both shell formation and feeding, we need to understand those effects to better predict how oyster populations will respond to a changing ocean.”

Global analysis finds rising ocean temperatures could reduce omega-3 fatty acids across marine food webs, with implications for seafood nutrition.

Ocean warming could reduce levels of omega-3 fatty acids in fish and other marine organisms, potentially affecting the nutritional value of seafood, according to a global study.

Researchers analyzed 489 experiments from 143 published studies involving 132 marine species, including algae, invertebrates and fish. The study, published in Global Change Biology, examined how warming and ocean acidification affect fatty acids throughout marine food webs. The researchers found that warming generally reduced omega-3 fatty acids, with larger declines occurring as temperatures increased.

“Our new study shows many fish and other seafood will become less rich in omega-3s over time, due to rising ocean temperatures as the climate changes,” the researchers wrote in an article for The Conversation. “In fact, we found omega-3 could drop by 50 percent under very high warming scenarios. This is very bad news for human health but also for the health of other animals in the food web.”

Marine algae produce EPA and DHA, two important omega-3 fatty acids, and sit at the base of marine food webs. Those nutrients move through the food chain as algae are eaten by other organisms, which in turn are consumed by fish and larger animals.

“If EPA and DHA levels get disrupted along the food chain, less of those crucial fatty acids are available for animals higher up – including humans,” the researchers wrote.

The effects varied among species and experiments, but the overall analysis found warming had a stronger effect on fatty acids than ocean acidification. “We found ocean acidification had less impact on fatty acids than warming, suggesting rising temperature is the dominant driver of this problem,” the researchers wrote.

The results should not be read as a prediction that omega-3 levels in seafood will fall by 50 percent across the board. The study combined results from controlled experiments, and responses varied among species and experimental conditions. The researchers called for more long-term studies under realistic environmental conditions to improve predictions of how climate change will affect the nutritional quality of marine organisms.

The findings could have implications for fisheries and aquaculture because omega-3 availability is important to both the nutritional value of seafood and the health of marine organisms. The study’s authors said anticipating climate-driven nutritional declines will be important for fisheries management, aquaculture and food security.

The researchers also pointed to better use of fish processing byproducts as one way to make more of existing sources of omega-3. With up to 80 percent of fish parts discarded during food processing, they suggested those parts could be used to produce omega-3-rich fish oil or as nutritional ingredients in aquaculture feed.

“Given the projected declines in nutrition into the future, these wasted fish parts could be better utilized,” the researchers said. “This might, for instance, include making fish oil products rich in omega-3 and other nutrients, or using these fish parts as nutritional aquaculture feed.

Read the full study here.