Kelp forests, long known for their biodiversity and ecosystem services, are rapidly vanishing from the southern Gulf of Maine. This ecological shift, replacing lush kelp beds with turf algae, is now revealing profound changes in the marine food web dynamics and energy transfer — reshaping the foundation of life under the sea.
📍 Where and What Is Happening?
Researchers from Bigelow Laboratory for Ocean Sciences have uncovered that kelp abundance has declined by up to 80% along southern Maine’s rocky coastlines. In its place, low-lying turf algae now dominate these reef ecosystems — but they aren’t offering the same ecological value.
Published in Science Advances (2025), the study demonstrates how this foundational habitat loss is altering predator-prey interactions and carbon flow in one of the world’s most rapidly warming marine ecosystems.
🔬 Key Findings: Energy Source Shift in Marine Food Webs
Using visual dive surveys and amino acid-based stable isotope analysis, the team traced how energy flows from primary producers to predatory fish like pollock.
🐟 In kelp-rich areas:
- Predatory fish derived over 50% of their energy from kelp-derived carbon.
- The food web was more complex, with broader ecological niches and dietary separation.
🐠 In turf-dominated reefs:
- Fish shifted to phytoplankton as their main energy source.
- Turf algae, despite their abundance, were not a significant contributor to the food web.
This shift reveals a critical ecosystem function of kelp forests that has largely gone unnoticed: their role as an energy provider in marine food webs.
🧬 Advanced Techniques: Tracing Energy with Isotope Fingerprinting
Lead author Dara Yiu, a Ph.D. candidate at the University of Maine, collaborated with Emma Elliott Smith from the University of New Mexico to implement amino acid-specific isotope tracing — a cutting-edge technique that pinpoints energy sources with high precision.
💡 “By analyzing individual amino acids, we gain much clearer insights into energy flow and source pathways that bulk analysis can’t reveal,” said Elliott Smith.
🌍 Ecological Implications: More Than Just a Habitat Loss
The study’s senior author, Doug Rasher, emphasized that kelp loss isn’t just habitat loss — it’s a collapse in energy infrastructure for the entire coastal ecosystem.
While tropical reefs and terrestrial forests have long been known to shift dramatically due to foundational species loss, the Gulf of Maine is only beginning to show these effects. The consequences for commercial fisheries, marine biodiversity, and ecosystem resilience are likely significant.
🔮 What’s Next? Conservation and Future Research
The researchers aim to apply their methods to Cashes Ledge, an offshore marine refuge 90 miles off the Maine coast. With thriving kelp beds and vibrant fish populations, it might serve as a model for restoration and resilience in future climate-adaptive marine management.
🗣️ “Our work is just the beginning,” said Rasher. “Understanding how kelp forest loss affects energy flow is essential for predicting how marine ecosystems will respond to climate change.”
📚 Reference
Study Title: Kelp forest loss and emergence of turf algae reshapes energy flow to predators in a rapidly warming ecosystem
Authors: Dara Yiu, Doug Rasher, Emma Elliott Smith
Journal: Science Advances (2025)
DOI: 10.1126/sciadv.adw7396
📌 Provided by Bigelow Laboratory for Ocean Sciences