In 2016, New Jersey sank 5,000 tons of concrete from a demolished Brooklyn pier off Sandy Hook; the rubble was designed to become habitat for fish and mussels

Old piers don’t usually get a second act. But in 2016, one from Brooklyn did. The New Jersey Division of Fish and Wildlife announced that 5,000 tons of concrete rubble from a pier in Brooklyn would be shipped to the Sandy Hook Reef off Monmouth County’s coast. The plan sounded pretty simple. Drop the concrete on the bottom of the ocean and let sea life take over.

From city debris to ocean home

According to the state's notice, the concrete would arrive in five loads totaling 4,631 cubic yards. The first load was due out Friday, August 19, 2016, though the schedule would depend on weather and sea conditions. The reef is part of the Division's Artificial Reef Program, and the notice included photos from a similar 2002 project on the Ocean City Reef, including one of fully colonized concrete. It also warned anglers to keep away from the barges that transport the concrete because the boats cannot easily change course.


How rubble becomes a reef

So why would fish care about broken concrete? It's all about the surface area. Mussels, barnacles, hydroids, anemones, stony coral, and other small animals find a concrete home where they can attach. They quickly cover it with what state officials called a living layer. This layer is the foundation of a marine food chain. Think of it as a new apartment building. The smaller organisms colonize first, followed by larger species. The state anticipated that black sea bass, tautog, scup, triggerfish, and summer flounder would move in soon after. It also expected the reef to be a popular spot for anglers heading out of Sandy Hook.

Does concrete really work?

Some research says yes. In a study conducted by researchers in 2002 at Miami Beach, Florida, there was a comparison between 12 reefs that were located in 7 meters of water. The reefs were made using limestone quarry boulders, concrete and gravel, or concrete and tires. Divers counted fish every two months, from October 1998 to February 2001. They recorded 146 fish species.

Fish populations did not differ significantly among the three reef types. Concrete did not stand out against the quarry stone. The authors also compared fish numbers before the reefs were built with those recorded two years after. This analysis found that fish numbers and diversity in the area were higher after the reefs went in.

What the bigger picture says

A 2020 meta-analysis in Frontiers in Marine Science combined data from 39 studies. It covered artificial structures such as reefs, shipwrecks, and oil platforms. On average, the analysis found that these structures supported fish density, biomass, species richness, and diversity at levels comparable to natural reefs. The details varied by location and reef material, so the four measures did not all match in every setting. Concrete reefs also tended to hold more fish per area than natural reefs, though material was not a statistically significant factor overall. On average, then, artificial structures held their own against natural reefs on these four measures, a promising sign for Sandy Hook, but results depend on the setting.

It’s not a magic fix

Reefs around the world may not behave the same way. According to the researchers, each reef must be judged on its location and objectives. Moreover, the review considered only four parameters related to the fish community. There could be other parameters, such as the composition of the fish community, that may not act similarly. Lastly, the researchers have not yet addressed whether artificial reefs generate fish or simply attract them from other habitats. The answer, the authors add, will likely depend on the specific system or species. Neither study looked at the Sandy Hook project itself. They only showed that the approach can work.

Why this story sticks

A torn-down Brooklyn pier could become a home for mussels, barnacles, and fish. That's a pretty wholesome story, but the more important lesson is a bit more nuanced. It's a promising idea, and research backs it up. However, researchers caution that the details matter because, at the end of the day, the effectiveness of a reef depends on its location and construction material. So next time you see a bit of concrete, your mind might drift off to Sandy Hook. Under the right conditions, it might end up hosting a whole ocean neighborhood.