EPISODE · Mar 2, 2026 · 46 MIN
Seagrass | Theory: The underwater ecosystem you've never thought about (but probably should)
from Big Ideas Only · host Montanus
In this episode of Big Ideas Only, host Mikkel Svold sits down with Kasper Elgetti Brodersen, Associate Professor at Roskilde University, to explore the science behind one of our most overlooked coastal ecosystems: seagrass meadows. What looks like an annoyance when it brushes against your legs while swimming turns out to be a biological powerhouse — nursery grounds for fish, carbon storage systems, and water quality filters all in one. Kasper explains how seagrass interacts with sediments and bacteria, why nutrient runoff from farmland is suffocating Danish fjords, and the surprising discovery that stressed seagrass can flip from climate helper to greenhouse gas emitter. The conversation covers what makes restoration so difficult, why seeds might be better than transplants, and what still needs solving before we can successfully garden the sea.In this episode, you'll learn about:Why seagrass provides four times the ecosystem services of coral reefs (measured in economic value)How seagrass creates its own oxygen supply to survive in toxic, oxygen-free sedimentsThe mechanism that turns nutrient pollution into plant-killing hydrogen sulfideWhy stressed seagrass meadows can start producing methane and nitrous oxide instead of capturing carbonWhat makes restoration in Danish fjords so challenging — and why seeds might work better than transplantsThe bacterial partnerships happening underground that help seagrass access nitrogenEpisode Content 01:13 Why seagrass is a big idea03:11 Global distribution and the 70% loss in Danish waters over the last century 05:07 The main stressor: eutrophication from agricultural nutrient runoff 07:15 How seagrass survives in anoxic sediment by pumping oxygen through internal channels08:56 Epiphytes explained10:17 What healthy conditions look like15:09 The eureka moment: discovering seagrass provides more ecosystem value than coral reefs19:26 Below-ground interactions: how oxygen release acidifies sediment and mobilizes nutrients20:22 The greenhouse gas twist30:32 Why restoration is still so hard41:04 What's happening in the rhizosphereThis podcast is produced by Montanus.
What this episode covers
In this episode of Big Ideas Only, host Mikkel Svold sits down with Kasper Elgetti Brodersen, Associate Professor at Roskilde University, to explore the science behind one of our most overlooked coastal ecosystems: seagrass meadows. What looks like an annoyance when it brushes against your legs while swimming turns out to be a biological powerhouse — nursery grounds for fish, carbon storage systems, and water quality filters all in one. Kasper explains how seagrass interacts with sediments and bacteria, why nutrient runoff from farmland is suffocating Danish fjords, and the surprising discovery that stressed seagrass can flip from climate helper to greenhouse gas emitter. The conversation covers what makes restoration so difficult, why seeds might be better than transplants, and what still needs solving before we can successfully garden the sea.In this episode, you'll learn about:Why seagrass provides four times the ecosystem services of coral reefs (measured in economic value)How seagrass creates its own oxygen supply to survive in toxic, oxygen-free sedimentsThe mechanism that turns nutrient pollution into plant-killing hydrogen sulfideWhy stressed seagrass meadows can start producing methane and nitrous oxide instead of capturing carbonWhat makes restoration in Danish fjords so challenging — and why seeds might work better than transplantsThe bacterial partnerships happening underground that help seagrass access nitrogenEpisode Content 01:13 Why seagrass is a big idea03:11 Global distribution and the 70% loss in Danish waters over the last century 05:07 The main stressor: eutrophication from agricultural nutrient runoff 07:15 How seagrass survives in anoxic sediment by pumping oxygen through internal channels08:56 Epiphytes explained10:17 What healthy conditions look like15:09 The eureka moment: discovering seagrass provides more ecosystem value than coral reefs19:26 Below-ground interactions: how oxygen release acidifies sediment and mobilizes nutrients20:22 The greenhouse gas twist30:32 Why restoration is still so hard41:04 What's happening in the rhizosphereThis podcast is produced by Montanus.
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Seagrass | Theory: The underwater ecosystem you've never thought about (but probably should)
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