Dr. Hamdan and her colleagues directed Odysseus around the shipwreck. The remotely operated vehicle, about the size of a small car, carried a payload of clear plastic tubes. At predetermined distances from the shipwreck — ranging from about 300 to seven feet — one of the vehicle’s robotic arms plunged a tube the size of a water bottle into the fine gray sediment of the seafloor. The team collected cores off the yacht’s bow, starboard side and port side. (On previous research cruises, the team had collected cores as far away as 3,300 feet, including ones off Anona’s stern.)

In June and July of last year, the team conducted similar fieldwork at two other shipwreck sites that they discovered in the Gulf of Mexico. Based on the shapes of the wooden sailing vessels and the artifacts found nearby, the ships were most likely built in the 19th century. Like Anona, both vessels were upright and intact. One rested in relatively shallow water, about 1,700 feet, and the other lay beneath more than 5,900 feet of water.

Back in the laboratory, the team extracted microbial DNA from the cores and sequenced the genetic material. “We look both at who is present and what their abundance is,” Dr. Hamdan said.

The researchers found the largest diversity of microbes — several hundred types — roughly 160 to 330 feet away from Anona. That makes sense based on the age of the shipwreck, Dr. Hamdan said, since the structure is providing resources to microbes. “Those resources begin to spread over time, and with the resource follows the microbes.”

The team also discovered that the seafloor’s microbiome varied with distance from Anona. That’s something that had not been demonstrated before, Dr. Hamdan said. “A shipwreck sitting on the deep ocean floor is materially changing the biodiversity of the seabed.”