Uneven, complex oyster reefs create protective crevices where calm waters allow larvae to attach and thrive.

Introduction

Oyster reefs are like underwater forests that provide habitat for hundreds of marine species, including shrimp, flounder, and herring. These forests not only protect, house, and feed marine life, they also help sustain commercial fishing that humans rely on for food.

For reefs to grow, individual oysters cluster together. Just like we need homes that shelter us from the elements, oysters must find locations where they can survive. That isn’t always easy for larvae, which swim in potentially rough ocean currents for up to three weeks before finally settling, hopefully, on a reef. If enough larvae can’t find purchase or don’t end up in locations where they can endure, reefs won’t flourish.

Life Cycle of an Oyster

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The Strategy

Scientists compared naturally thriving reef locations to a restored reef site to study the variables that influence larval success. They found that natural reefs have surfaces that increase the larvae’s ability to attach to and survive on it.

Human buildings are uniform structures because we design elements like bricks to fit together perfectly. But oyster shells are rough and irregular. They secrete a specialized adhesive to stick to one another, building complex, amorphous structures that climb from the ocean floor up rocks and seawalls. These structures must be sturdy to withstand strong forces from the ocean’s currents.

Luckily, the bulky external structure of an oyster reef shields a complex inner world of crevices, fissures, and gaps that develop from the oysters’ nonuniformity. Larvae find protection within these “interstitial folds,” where calmer waters exert weaker stresses.

Turbulent waters may help swimming larvae reach farther destinations but can make it difficult for them to attach when they arrive. Strong currents can also pull attached juveniles or adults off reefs, especially on the edges where velocities are the greatest. Stirred-up sediment can even bury individuals at lower elevations within the structure.

Luckily, the bulky external structure of an oyster reef shields a complex inner world of crevices, fissures, and gaps that develop from the oysters’ nonuniformity. Larvae find protection within these “interstitial folds,” where calmer waters exert weaker stresses. Reefs with more of these internal fissures have higher oyster abundance and more larvae that successfully attach. Furthermore, oysters within reef crevices grow faster and live longer than those positioned outside.

Inside these protected zones, tightly packed vertical surfaces provide additional refuge, restricting access for predators such as the blue crab.

The Potential

Overfishing, coastal development, and disease have ravaged oyster reefs. Globally, as much as 85% have been lost over the past few centuries. Understanding how oysters optimize their reef designs to maximize larval success can improve restoration methods to revive in failing reefs. It could also lead to greener concrete for underwater structures, made with compositions and textures that promote larvae attachment and reef growth.

Oysters can also inspire ideas beyond reef construction. For example, what can oysters teach us more broadly about the strong currents that cause erosion and weathering of materials in water and other environments as well?

Last Updated June 14, 2021