Sponges photosynthesize and contribute to coral reef productivity
A University of Amsterdam study found sponges photosynthesize and supply 11% of gross primary productivity on Curacao reefs, adding a new reef carbon source.
Photo by Benjamin Young on Pexels
Researchers at the University of Amsterdam’s Institute for Biodiversity and Ecosystem Dynamics (IBED) reported on July 1, 2026, that sponges can photosynthesize, like plants, and add to the productivity of tropical coral reefs. The finding, published in the journal Functional Ecology, shows that sponge photosynthesis is not a rare trait but a measurable contribution to how much energy and food a reef produces. On reefs around the Caribbean island of Curaçao, half of the sponge species tested accounted for 11% of gross primary productivity.
Sponges are usually described as filter feeders that consume other organisms. The study, “Sponges are celebrated heterotrophs but also key primary producers on changing coral reefs,” argues they also make their own food through symbiotic microbes, which changes how reef energy budgets should be counted.
What sponge photosynthesis adds to coral reefs
Sponges host tiny symbiotic microbes, some of which are photosynthetic. Those microbes use sunlight to produce food and release oxygen. The trait had been tested before, but only on a few species. The IBED team widened the sample and scaled the measurements up to the whole reef.
Michelle Achlatis, who led the work as a postdoctoral researcher at IBED, and colleagues assessed 24 of the most common sponge species on Curaçao’s reefs and took extensive measurements for eight of them. To gauge how many sponges are present, they used a dataset that accounts for the reef in three dimensions, which captures more sponge volume than flat surveys. “A previous study found that when you look at the three-dimensional reef, there are so many more sponges there than you expect,” Achlatis said.
The result surprised the team. Achlatis said she had expected perhaps a quarter or a third of the species to be photosynthetic, and had not expected how much they added to productivity. “It’s a group that in previous food web studies or big coral reef modeling were always put aside as pure consumers and not producers,” she said. “But they are quite flexible feeders and can supplement with photosynthesis.”
The table below sets out the study’s confirmed scope.
| Parameter | Value |
|---|---|
| Publishing body | University of Amsterdam (IBED) |
| Journal | Functional Ecology |
| Location | Reefs around Curaçao |
| Sponge species assessed | 24 (most common) |
| Species measured in detail | 8 |
| Share of gross primary productivity | 11% |
Source: EurekAlert / University of Amsterdam (July 1, 2026); Functional Ecology.
Why the finding matters for reef carbon
The study covered one tropical region, but the researchers say sponges in similar regions may share the same photosynthetic components, so the results may apply more widely. That has a practical consequence for climate accounting: Achlatis argues sponge-rich ecosystems, such as coral reefs, should be added to assessments of carbon sequestration. Reefs are already studied as habitats and fisheries; counting sponges as producers, not only consumers, adds to the case for including them in carbon removal through enhanced rock weathering and other carbon-accounting work.
“The case we are trying to make with this paper is really that people should be aware that sponges are not only recycling carbon and nutrients that they find on the reef, they also have their own ways of making them, even if they’re small amounts, comparatively,” Achlatis said.
Jasper de Goeij, associate professor of marine benthic ecology at IBED and a co-author, said the result should change how many ocean organisms are classified. “Together with their symbiotic microbes, sponges can photosynthesize, just like a plant,” he said. “We need to look differently at many organisms living in the ocean, as they do not follow the strict plant-animal distinction as most organisms on land.”
Background: sponges on coral reefs
Sponges are among the oldest animal groups and are a common feature of tropical reefs, where they filter large volumes of seawater and cycle nutrients. Reef research has long treated them mainly as consumers within the food web. Work at the University of Amsterdam’s Institute for Biodiversity and Ecosystem Dynamics has focused on their role in reef ecosystems, including how three-dimensional surveys reveal far more sponge volume than flat mapping suggests. The Functional Ecology study, published July 1, 2026, builds on that record by measuring photosynthesis across 24 species on Curaçao’s reefs and scaling the results to the ecosystem, where sponges supplied 11% of gross primary productivity. The authors present the work as a reason to count sponge-rich reefs among the systems that produce and store carbon, not only those that consume it.
Sources: Functional Ecology; University of Amsterdam (IBED); EurekAlert! / University of Amsterdam; ECO Magazine
Featured image: photo by Benjamin Young on Pexels (free Pexels license).
Become a Sponsor
Our website is the heart of the mission of WINSS – it’s where we share updates, publish research, highlight community impact, and connect with supporters around the world. To keep this essential platform running, updated, and accessible, we rely on the generosity of you, who believe in our work.
We offer the option to sponsor monthly, or just once choosing the amount of your choice. If you run a company, please contact us via info@winssolutions.org.
I specialize in sustainability education, curriculum co-creation, and early-stage project strategy. At WINSS, I craft articles on sustainability, transformative AI, and related topics. When I’m not writing, you’ll find me chasing the perfect sushi roll, exploring cities around the globe, or unwinding with my dog Puffy — the world’s most loyal sidekick.
