Restoring New York’s Marine Life, With the Help of a Billion Oysters

When Jennifer Zhu (Ph.D. ’22, Biology) was growing up in New York City, she wasn’t aware of the natural environment surrounding her urban landscape. It was only later, as a Cornell undergraduate who was interested in the genetics of oysters, that she realized her hometown was home not only to an oyster population, but to a variety of marine life. “I left the city to find out that there actually was nature in the city,” she says. “And I came back to enjoy the nature I hadn’t really encountered.”

Now Zhu is helping high school students in New York to get first-hand experience with urban nature, and with the creature that was once famously plentiful in its waters, as part of her role at the Billion Oyster Project, a nonprofit dedicated to restoring oysters — one billion of them by 2035 — to New York Harbor through public education initiatives. As the organization’s marine habitat resource specialist, a job she started in February, two months after defending her Ph.D., Zhu has found herself in a position that seems perfectly tailored to her interests and goals.

The first in her family to attend college — her parents immigrated from China — Zhu enrolled in Cornell intending to study biological science. During her first year, she had the opportunity to travel to the Galápagos Islands for a week as part of a class. “That was when the passion really opened up to nature and marine life,” she says. “Everything there was almost immaculate, and viable.” The experience also gave her a concrete understanding of the impact of humans on the environment. “You kind of have to see for yourself how nature can be when it’s untouched, without garbage and pollution.”

She first got in touch with the Billion Oyster Project when a professor at Cornell invited her to conduct field work at some of their research stations. By the time she graduated, she’d decided to pursue a Ph.D. at the Graduate Center, where she met Professor J. Stephen Gosnell (GC/Baruch; Biology/Natural Sciences), whose lab conducts fieldwork in the city’s coastal waters. Zhu expanded her research to include ribbed mussels, investigating how their restoration might enhance the ecosystem services they contribute to the salt marshes of Jamaica Bay. She also reconnected with the Billion Oyster Project, because Gosnell’s lab, which she joined, was working with the project on oyster reef restoration.

Why oysters? Just a century ago, they were so common in New York Harbor that they were cheap bar food and exported by the millions. “Back then you could go into New York Harbor and pick up an oyster shell as big as a dinner plate,” Zhu says. Overharvesting, dredging, and pollution all but destroyed the population. The Billion Oyster Project hopes that part of the solution, at least in terms of the harbor’s cleanliness, might be oysters themselves: They are natural water filters. And the benefits of restoring the city’s oyster population go far beyond creating a habitable environment for marine life. Oysters tend to grow one on top of the other, forming reefs that serve as breakwaters that can help absorb the wave energy of storms and hurricanes. The Billion Oyster Project restores reefs throughout the harbor and is part of the Living Breakwater Project, designed to help protect Staten Island from the next Hurricane Sandy. “The living part of these breakwater structures is our oysters,” Zhu says. “Our oysters are thriving, and they are going to be attracting a whole bunch of other marine animals that will make a healthy ecosystem that even more marine life can join.”

In the eight years since the Billon Oyster Project was founded, it has restored 75 million live oysters and collected 1.9 million pounds of shells to build reefs in New York Harbor, it says. The project partners with schools throughout the city, involving students and community scientists in their restoration and research. “It’s a way to connect kids with nature and also to make them aware of the problems that we have, in terms of the policies around climate change, and to understand how important the ecosystems around us are,” Zhu says. 

Speaking recently on Pier 5 of Brooklyn Bridge Park, where members of the project were checking on the health of oysters that were put out into the water two years ago, Zhu explained that even though the oyster population has come a long way, the city’s oysters are most definitely not meant for consumption. When there is as little as 30 minutes of light rain, or one-tenth of an inch of rainfall per hour, New York’s combined stormwater and sewage overflows directly into the Harbor during rainstorms. “Our oysters are filtering out not just algae, but also bacteria,” she says. (Zhu is too familiar with oysters to eat even the farmed variety, she says.) The oysters in the project’s cages have grown considerably, sometimes through the open bars, and have attracted tautog and sea squirts, rubbery blob-like creatures that spray water if you squeeze them. The oysters were spawned in the project’s lab on Governor’s Island. To build the reefs that serve as landing platforms for young oysters, the project collects oyster shells from local restaurants, and leaves them out to cure on the island for a year before installing them in the harbor.

Zhu is spending most of May working in the field and collecting data on oysters. In June, she’ll collect data on water quality. “We’ll check out the dissolved oxygen, water temperatures, salinity, pH, all these different parameters, so that we can say, ‘Hey, our oysters are here. This is what’s happening in the water. Is there some relation to that?’” 

In the non-field seasons of her job, she plans to analyze the data, write reports, and work on making the project’s research accessible to the public — expertise that she developed during her time at the Graduate Center. “The Graduate Center pushed me to develop skills through teaching, through applying for funding, through connecting with other researchers,” Zhu says. She will also continue to mentor students and conduct research. (All three of her Ph.D. papers have been published, including a recent meta-analysis of whether captive-bred or -raised prey, ranging from birds to fish, can be trained to fear predators to increase their chance of survival when they are released into the wild.)  

Being part of a community of researchers, she says, is one of the things she values the most about her new job. “Through my research, I get to connect with not just other researchers who are doing work in New York City, but also researchers who are passionate about conserving the environment,” Zhu says. “We want to make sure that humans aren't disturbing​ our environment, when we don't even know all the ways that it provides for us."