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Brian Lehrer: Brian Lehrer on WNYC. For this membership drive, we're going to end most of the shows with a brisk deep dive into the marine life living right here in our listening area. We have picked six unique species that you might not have expected are in our waterways. Later in the week, we'll talk about the lined seahorse. Do you know we have seahorses here in the New York area? The technically edible, but we don't recommend that, blackfish, the spider crab, the skilletfish, and something called the sea squirt.

We've partnered with our friends at the Billion Oyster Project, a New York City-based nonprofit that has the goal of restoring one billion live oysters to New York Harbor by 2035. Appropriately, we begin this series now with a closer look at the eastern oyster. Joining us is Pete Malinowski, executive director and co-founder of the Billion Oyster Project. Hi, Pete. Welcome back to WNYC. Thanks for doing this with us.

Pete Malinowski: Hi, Brian. Thank you so much for having me.

Brian Lehrer: I guess listeners may not know that New York Harbor used to be known for its oysters. You've been quoted as saying that at one time, half the world's oysters were harvested right here in the city. I certainly didn't know that. Can you take us back to whenever that was and give us a picture of that industry at that time?

Pete Malinowski: Sure. The more I learn about it, the more I learn that this is a global phenomenon. I think that the half the world's oysters may be an overstatement, but if you look at the 1800s, in the year 1800, there were 60,000 people in New York, and by the end of the 1800s, there was over three million people, so it was a time of great change. New Yorkers during that time were averaging over 600 oysters per person.

There was a ton of oyster harvesting, and we were slowly removing this really cool important landscape from the harbor and consuming it and cutting that ecosystem off at the knees. It was a time of gluttony, eating all the oysters, and it was also a time when the Harbor really took a hit from having that ecosystem removed.

Brian Lehrer: I guess it's an example of overharvesting and what the consequences of that has been for our waterways, just like overuse of the planet's resources in general. Tell us a little more about just how cool oysters are. Eastern oysters are bivalve mollusks. Can you explain what that means?

Pete Malinowski: Mollusks are all of the snails, slugs, clams, oysters, squid, and octopus. It's a really diverse phyla of organisms. There's actually over 35,000 different mollusks in the ocean, but when you [unintelligible 00:03:00] a bivalve mollusk, the bivalve refers to them having two shells. Those are oysters, clams, mussels, scallops, and animals like that.

Brian Lehrer: They thrive in New York because it's a brackish habitat. Can you explain what brackish water is?

Pete Malinowski: Brackish water is a mix of salt and fresh, or an estuary like New York Harbor. Here we have the Hudson River bringing freshwater down and meeting the ocean, and so the salinity in New York Harbor is a mix of ocean salinity and freshwater, and that's really good for oyster reproduction and survival. A lot of estuaries traditionally had high densities of oysters in them.

Brian Lehrer: According to the National Oceanic and Atmospheric Administration, oysters first mature as males then later develop female reproductive capabilities and some switch back to male. Wow, how does that work?

Pete Malinowski: [chuckles] The term is protandric hermaphroditism, if you're wondering. It turns out that eggs are more valuable than sperms, so are more metabolically expensive. As oysters grow and develop, the metabolic reserves to produce eggs, they transition from male to female. It's a very common strategy and plants also. Many younger plants will only produce male flower parts until they are large enough to produce those embryos. Oysters respond by releasing their gametes into the water and then fertilization happens in the water column.

Brian Lehrer: One of the coolest parts about oysters is how they mature. According to your Billion Oyster Project Species ID Guide, oyster larvae swim freely for several weeks and then sink down to the seafloor. They use their foot to crawl around and search for an adult oyster to settle on. Now, for some listeners that may be the first time that they have heard of an oyster having feet or a foot, can you explain that a bit more?

Pete Malinowski: Sure. An oyster larvae look very similar to clam and mussel and scallop larvae. At that stage, they're about a quarter of a millimeter across, so roughly the width of a human hair. They're very, very small. They crawl around just like clams do. They have a little shell and the foot comes out and they walk along the bottom with that foot. That period is very brief for oysters, because once they attach to a substrate, they never move again for the rest of their lives. They actually cement themselves to an oyster shell or a piling, or in New York a tire or a plastic bag, and then they'll grow their own shell, and from there, go about their lives in that spot.

Brian Lehrer: Once mature, oysters are powerful water filters. Can you explain how they process water and what they filter out and should I attach one to my faucet?

Pete Malinowski: I think that'd be a great way to kill an oyster. They filter water by pulling water through their bodies and then their gills actually work to sort through the different particles in the water and then bring it down to their mouth. There, they'll decide what they ingest and what they'll reject as pseudo feces or fake poop. Their biggest impact on water quality is processing nitrogen through their feeding. Nitrogen is the biggest pollutant in all urban estuaries and most coastal environments, and that comes into the water from agricultural runoff and from wastewater runoff.

An excess of nitrogen can cause phytoplankton blooms, so excess biomass in the water column, which then settles out and can affect the dissolved oxygen in the water. If you hear about dead zones or hypoxia or eutrophication, that's all a result of excess nitrogen. Oysters by incorporating that nitrogen into their body tissue or by pulling it out of the water column and putting it on the bottom where it's accessible to other animals and bacteria helps cycle that nitrogen out of the water column.

Brian Lehrer: It is definitely the first time that the word fake poop were used on the Brian Lehrer Show. This brings us in our last minute to the big issue facing the eastern oyster, and that's habitat destruction. Oysters essentially create their own habitats in a certain way, but humans are working against that. What's the issue and what's a possible solution for you as oyster Pete?

Pete Malinowski: Well, the habitat has been destroyed. You can think of New York Harbor as a 200,000-acre forest that's had all of its trees removed. Those oyster reefs are the three-dimensional structure of a ecosystem. We call them ecosystem engineers. What we're doing to try to help that is restoring oyster reefs to New York Harbor. Building back the three-dimensional habitat, providing homes for all these other animals that used to thrive in oyster reefs here in New York Harbor.

The cool thing is that there's no competing uses for so much of the Harbor. There's all this empty land that's underwater that can be reclaimed by the natural environment if we're able to restore these reefs. We think about it as rewilding New York Harbor in that sense.

Brian Lehrer: Pete Malinowski, executive director of the Billion Oyster Project. Thanks so much for coming on and kicking off the series with us. That was really fascinating.

Pete Malinowski: Thank you, Brian. Appreciate it.

Brian Lehrer: Listeners, tune in tomorrow to hear all about the lined seahorse, one of the more delicate species that keeps showing up more and more in our local New York area waterways and what that indicates about local water conditions.

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