WELLFLEET — Attaching heart monitors to bay scallops, examining the fuzzy organisms on blades of seagrass, and counting sea stars. These are the kinds of things scientists from across the country come to do in the Cape Cod National Seashore.

Eight of them — the lineup included Ph.D. candidates, a Center for Coastal Studies researcher, and a semi-retired Park biologist — gave brief presentations on studies they conducted at the tenth annual Science in the Seashore Symposium on Sept. 23, sponsored by the Friends of the National Seashore.

“This is a tremendous body of scientific effort that informs management decisions for the Seashore,” said Supt. Brian Carlstrom in his opening remarks.

Tipping the Trophic Scales

Nancy Leland, University of New Hampshire

Cyanobacteria blooms have shut down several Cape Cod ponds in recent years. Some generate toxins that target the nervous system, while others take aim at the liver. Nancy Leland spent this past summer sampling Herring Pond in Wellfleet, and her preliminary results suggest that when cyanobacteria run rampant, it’s a sign that the food web in the pond is off balance.

In early summer, Herring Pond was host to a great diversity of zooplankton, a microscopic animal that grazes on cyanobacteria, but by mid-June, the structure of this community shifted. Diversity dwindled, likely because predators that go after fish proliferated, and as the summer wound down, rotifers, which are microscopic algae eaters, dominated the pond. Compared to other zooplankton categories, rotifers are less efficient at controlling cyanobacteria biomass — which may, in turn, give certain cyanobacteria species a chance to flourish.

Strengthening the Salt Marsh

Katie Sperry, Northeastern University

A perk of salt marshes: they can buffer us from storm surges. But Spartina alterniflora, the foundation cordgrass species, faces the dual threats of climate change and human development. How to boost the resiliency of this coastal ecosystem is a central question in Katie Sperry’s research. Upping genetic diversity among S. alterniflora may be a promising avenue, especially as tidal restoration efforts are underway.

One method to restore the salt marsh ecosystem: removing barriers to tidal flow, then planting S. alterniflora along the degraded marsh, as was the case in North Truro’s East Harbor. Sperry compared genetic diversity among grasses from this site and samples from natural salt marshes, and she found high genetic similarity between the populations. “To me, this is a really good sign,” she said. “I think this indicates that the seeding strategy that was used to revegetate East Harbor seems to have succeeded in establishing comparable genetic diversity to that found elsewhere in the Cape Cod National Seashore,” she said.

Downstream of the Dike

John Portnoy, Cape Cod National Seashore

Just seaward of the Herring River dike lie over 90 acres of oyster beds that have been closed to harvesters since 1985. That year, fecal coliform bacteria concentrations were well beyond the state water quality standard, “which is set very low,” said John Portnoy. “These are filter feeders, and they tend to concentrate potentially pathogenic bacteria in their tissues that people can subsequently eat.”

Fecal coliform survival is favored by low salinity and dissolved oxygen — conditions reinforced by the dike, which stops the river from receiving salty, well-oxygenated bay water. But Portnoy anticipates that the Herring River Restoration Project, which aims to restore tidal flushing, will substantially boost water quality.

A comparison of two sets of water quality data from 2005 and 2020 hints at the project’s potential. Above the dike, the 2020 samples showed a threefold jump in bacteria concentrations over 2005 — but below the dike, where tidal flushing occurs, concentrations were comparable.

“Tidal restoration is likely to reduce bacterial concentrations with clean, high-salinity Cape Cod Bay water,” Portnoy said. This could eventually allow nearby shellfish beds to open again.

Shellfish FitBits

Stephen Tomasetti, Stony Brook University

In 2019, catastrophe struck the Peconic Estuary, the epicenter of New York State’s bay scallop fishery. More than 90 percent of the scallops died — and in 2020, the fishery collapsed again. Marine biologists and fishermen have since been keeping a close watch on this sensitive species, but growth measurements take weeks to conduct. By contrast, temperature stress, coastal hypoxia (lack of oxygen in the water), and harmful algal blooms — suspected contributors to the die-offs — happen on “scales as short as minutes, hours, or days,” Stephen Tomasetti wrote in the abstract of his talk.

For quicker snapshots of bay scallop health, Tomasetti built a shellfish “FitBit”: an optical infrared sensor glued onto the scallop’s shell just above the heart. It captures changes in infrared light that accompany cardiac contractions. Measure these fluctuations over time, feed the data through a custom script, and a heart rate can be calculated.

Tomasetti deployed these “FitBits” in the Peconic Estuary and here, and though Tropical Storm Ida walloped our shores, his East Harbor bit-wearing scallops weathered the storm. The monitors recorded bay scallop heart rates every 15 minutes for a month, alongside temperature, dissolved oxygen, and salinity.

Warming waters and low dissolved oxygen levels seemed to hasten scallop heart rates. “These stressors may have contributed to the local extirpation of the NY bay scallop fishery in 2019 and 2020,” Tomasetti concluded.

A Bird’s-Eye View of the Great Island Tavern

John M. Steinberg, UMass Boston

Buried on Great Island is a tavern dating to A.D. 600. The sands have kept it remarkably well preserved, yet the site faces rapid erosion from the creeping shoreline. To monitor this erosion threat, John M. Steinberg sought to take a series of aerial photographs. The National Park Service wasn’t too keen on drones — but they allowed a kite.

Every couple of months between early 2018 and late 2020, Steinberg strung a camera from a kite to map the shoreline from the air. He saw the vegetation line dramatically recede, and, in some places, elevation sank at least half a meter. On one occasion, a migrating duck photobombed their shots.

“This is a remarkably dynamic environment that’s being rapidly lost,” Steinberg said. In the coming years, his team hopes to sketch out, in finer detail, the types of encounters that took place at the tavern. The upper layers of the site contain a mix of European and Native American artifacts. Whether or not these two groups of people mingled, “we’d really like to know,” Steinberg said.

Catching Plastic

Cece Gerstenbacher, Boston University

Up close, a blade of seagrass looks fuzzy. Algae carpets the surface, and snails may lay their eggs there, joining the neighborhood of epibiont species — that is, organisms that live on top of one another — that have taken up residence atop seagrasses. All this epibiont fuzz, Cece Gerstenbacher has found, can act as a microplastic “trap.”

In summer 2020, Gerstenbacher examined 80 blades of seagrass and found all manner of microplastics clinging to them. Among the mix: fiber, fragments, and beads of various shapes, sizes, and colors.

How microplastic accumulation affects seagrass meadows and their epibiont communities remains unclear. The extra baggage may hinder photosynthesis and possibly expose species to toxins.

Living Under a Rock

Melina Giakoumis, City University of New York

To hunt for sea stars, Melina Giakoumis heads out at low tide. She lays down a transect for sampling, and within a meter on either side of this line, she scans the subtidal zone, flipping over rocks and brushing aside seaweed. Often, she has better luck wading offshore and snorkeling around.

Giakoumis has been retracing the steps of Bruce Menge, a marine biologist who, in 1979, fielded the sea star populations up and down New England beaches, including two locations in the Seashore. But 42 years later, Giakoumis’s counts have paled in comparison to Menge’s. Her preliminary findings show dramatic population crashes along the coast. The most striking decline occurred in Chamberlain, Maine. In 1979, Menge found 18.9 stars per quarter meter squared; in 2021, Giakoumis found 0.005 stars in the same range. She came up empty-handed at Duck Harbor. Ditto for the Provincetown Causeway — though after packing up her transect, she spotted a lone, feeble-looking star on her walk back to her car.

Sea star wasting disease, a flesh-eating illness with an 80-percent mortality rate, could be responsible for the decline. Warming seas, Giakoumis added, may help the illness spread more quickly — kicking a population that’s already down.

Stalking Sharks

Bryan Legare, Center for Coastal Studies

The closer you are to a seal hollow, Bryan Legare said, the more likely a shark may be lurking nearby. “The general guidelines of not swimming near seals does definitely hold up,” he said.

Between 2019 and 2021, Legare’s team tagged over 82 individual white sharks and mapped their movements in ultra-fine scale, using acoustic receivers at Head of the Meadow Beach in Truro. They also set up trail cameras to track the number of seals bobbing in the water and kept tabs on waves, currents, tides, and turbidity (water “cloudiness”). Considering these factors, his team plans to build a model predicting how sharks are using Outer Cape beaches, which may inform future public safety recommendations.

In 2019, Head of the Meadow — where seals congregate on the bars  — saw a shark 40 percent of the time, and in 2020, this rose to 51 percent. Legare is still crunching the numbers for 2021, but preliminary results suggest that, this past year, sharks have been present 50 percent of the time. His team later expanded to Nauset Beach in Orleans, and initial data indicate sharks were around at least 60 percent of the time in 2021. Looking ahead, he hopes to expand this project to Marconi, Newcomb Hollow, and Herring Cove beaches.