As a burning sunset faded over Menemsha on Monday, a large crowd of beachgoers settled into the sand for a series of short films about the local shellfishing industry and the perils of overdevelopment on the Cape and Islands.

Kids, adults and dogs enjoyed the last moments of daylight before a projector perched on a wooden stand came to life and lit up a screen that hung from the side of a Martha’s Vineyard Film Festival truck parked on the beach.

Young campers in the festival’s summer filmmaking program kicked off the event by introducing themselves and sharing their favorite part of the program, which involves documentary filmmaking, animation and live-action shorts. The first film of the evening, shot last week, featured campers interviewing people on the Island about their relationship to the ocean.

Robin Athearn talks to the audience. — Mark Lovewell

“I like to just sit and watch the birds soar overhead,” answered one person when asked what she liked most about the ocean.

“It’s one of nature’s great resources, and on a hot day like this, it’s very refreshing,” said another. “But up here, it’s just plain beautiful.”

Many of the interviews took place in Menemsha, as did scenes in the next film, about the Vineyard conch fishery – adding to the intimacy and immediacy of the event, which was sponsored by LoveMV and Sargent Gallery as part of the MVFF summer series.

The Secret Life of Conchs, by Aquinnah-based filmmakers Liz Witham and Ken Wentworth, explores the Island’s commercial conch fishery with Shelley Edmundson, a graduate student at the University of New Hampshire who is studying conchs in the area. The film includes the first footage of a conch laying a string of eggs — a days-long process condensed into minutes through underwater time-lapse photography.

“I’d be very happy if this fishery was still operating 20 years from now and people were able to make a living and the whelk population were flourishing,” Ms. Edmundson says in the film. “Fishing is still viable and there are still sustainable ways of doing it.”

In a group discussion that followed the screenings, Ms. Witham said she had been surprised to learn that conchs were the Island’s largest commercial fishery, since most of the product ends up in China. But she said an understanding of the fishery plays an important role in mitigating the effects of wind farms and other offshore developments in the area. “It’s really important for people on a state level to understand these cycles . . . or you can inadvertently wipe out an ecosystem,” she said.

The Watershed, a film by Elise Hugus, dropped in on members of the Mashpee Wampanoag Tribe and others working to restore impaired estuaries on the Cape. One scene shows a fisherman with a clam rake pulling up clouds of black muck from the bottom of Eel River — the result of land-use changes in the watershed. Other scenes show workers harvesting quahaugs and preparing them for market, although their livelihoods face an uncertain future.

“This is not like it used to be,” tribe member Emma Jo Mills-Brennan says in the film. “People don’t take it seriously and realize that every little thing that we do affects the water.”

The film includes an animated sequence on how nutrients from septic tanks lead to algal blooms that deprive organisms of oxygen and sunlight — a topic that reappeared throughout the evening. One solution is aquaculture itself, since shellfish consume phytoplankton. In the film, Scott Lindell of the Marine Biological Laboratory in Woods Hole demonstrates how oysters can clean a murky tank of water in just a few hours — another process captured with time-lapse photography.

The Last Bay Scallop? by John Stanton took the audience 30 miles out to sea for a look at Nantucket’s historic bay scalloping industry, which has struggled to survive in the face of declining water quality and the widespread loss of eelgrass.

Some dusty pink clouds were still visible from Menemsha as scallopers, town officials and others on the screen reflected on the past and future of the industry. The film also highlights the importance of eelgrass, which many species depend on for food and habitat. As with The Watershed, it points to an overload of nutrients from wastewater and fertilizers as the main culprit.

“If I had my way, we’d ban fertilizer on Nantucket,” selectman Bob DeCosta says in the film — a sentiment that drew applause on the beach. Nantucket recently appropriated $1.3 million to renovate the island’s shellfish propagation lab, which grows around 170 million bay scallop larvae each year. The town has also approved a $41 million initiative to expand the town sewer system to keep more nutrients out of the groundwater.

Filmmakers joined Martha’s Vineyard Shellfish Group director Rick Karney to comment on the films and answer questions. About 50 people stayed on for the discussion, bundled up in sweatshirts and blankets on the beach.

“Everything that you saw was true,” Mr. Karney said of the films. “We know what the problems are now. We [just] need the support.” He urged people to take part in town meetings and get involved in their communities. In response to a question about whether fertilizers were ever safe for the environment, he recommended organic products, if anything, and noted that

the time of year may affect the amount of runoff into the ponds. He drew attention to the Islandwide fertilizer regulations that went into effect last year, but he said the real problem was wastewater. “That’s true in Falmouth, that’s true on Nantucket, that’s true on Long Island . . . We see this problem all over.”

Mr. Stanton pointed to some of the challenges in improving water quality on Nantucket. “It really comes down to getting people together and getting them riled up,” he said. “On both these Islands, there are a lot of socioeconomic hurdles to getting some of that done.” But he felt reassured by the efforts to keep Nantucket’s shellfishing industry alive. “The great majority of people don’t scallop anymore, but they remember it as a local culture and they want to keep it going,” he said.

In closing, Mr. Karney encouraged people to support local aquaculture, but he also noted the political backlash that may accompany even minor changes to the environment. “I think we have to get past that, and realize that the more shellfish we put in the water, the better the clarity is going to be,” he said. “It’s part of the solution.”