Nauset Marsh System May Reveal Answers To Harmful Algal Blooms

by Jeffrey M. Brodeur, Woods Hole Sea Grant

The Nauset Marsh system holds many secrets for visitors to Cape Cod, from tucked-away tidal creeks loved by kayakers to a vast array of wildlife hidden in the grassland. For a team of Woods Hole Sea Grant-funded researchers, however, the secrets they hope to uncover within the marsh are of a more ominous nature.

The system is home to a nearly annual outbreak of paralytic shellfish poisoning (PSP) caused by harmful algal blooms (HABs, or "red tides"), which have a major effect on the thriving commercial and recreational aquaculture activity in the area.

Dennis McGillicuddy of WHOI deploys a drifter in the Bay of Fundy during a 2005 study into harmful algal blooms.

Photo by Mike Carlowicz, WHOI

In addition, cells of the causative organism Alexandrium fundyense from the marsh are often found in areas downstream of the system, creating concern about the organism's impact regionally.

So a team led by biologist Don Anderson, a senior scientist at the Woods Hole Oceanographic Institution, is looking into the distribution and dynamics of the toxic blooms within the system and nearby waters.

The researchers hope to better guide the monitoring and management of outbreaks, especially with regard to the current policy, which shuts down the entire marsh when PSP is detected.

What they discover could be critical to the health of the system. PSP occurred in Salt Pond, Eastham, in eight of 17 years (48 percent) from 1975 to 1991 and in 16 of the next 17 years (94 percent), according to Anderson. In fact, state fisheries officials told him the system "has recently become one of the hottest spots for shellfish toxicity along the Massachusetts coast."

And although exchange within the salt pond is limited because of restrictions in Nauset inlet, leading to the belief that blooms are localized, a devastating bloom in 2005 revealed "that the highest cell concentrations of this species ever recorded in southern New England were found just outside the Nauset inlet," he wrote in his proposal.

That, in turn, leads to some major questions, especially if the blooms come from cysts germinated locally or in the Gulf of Maine, where Anderson has conducted much of his work.

It's in the Gulf of Maine that Anderson and Dennis McGillicuddy, an oceanographer and senior scientist with WHOI's Applied Ocean Physics and Engineering department, have become adept at providing an early warning system for toxic algae blooms along the New England coast.

In the fall of 2007, surveys revealed an extreme number of cysts-30 percent more than previously found-lying dormant in the sediment of the Bay of Fundy, launching point for previous outbreaks of Alexandrium.

Entering the data into a computer model they constructed, the team in late April predicted a widespread bloom affecting New England coastal waters. Though McGillicuddy says they were "ready to be wrong," their predictions were extremely accurate.

"It met our expectations-it was a major regional bloom," Anderson says.

And though closures occurred from Canada to Massachusetts, the modeling allowed government agencies and shellfishermen to take protective actions earlier than they may have without the projections.

"Managers were happy this [prediction]was made," Anderson says. "It allowed them to assemble the staff and resources they needed, and it showed that the management and scientific community were in control [of the situation]."

In addition, in a world where perception of a crisis is often as damaging as the crisis itself, early warning allowed for education and awareness.

"It helped reduce the hype and hysteria around the bloom [so] the economic impact was lessened," Anderson says, adding that the consumer needs to understand that the safeguards in place work. "We really do believe in the safety net that the state and federal governments have put in place," he says. "They do a fantastic job of keeping dangerous seafood off the market."

This fall, members of the project are taking cores of sediment from stations throughout the marsh and will then count the number of Alexandrium cysts contained within each. They are also taking a look at the historical records for shellfish toxicity.

Next spring, when the blooms normally are found in the western Maine coastal current and passing the outer Cape, the team will collect hundreds of water samples inside the marsh system and outside as well, to gauge abundance. Conductivity, Temperature, Depth (CTD) sensor profiles will aid in determining other factors influencing the dinoflagellate.

Anderson says that discovering what's occurring in the embayments and salt ponds of Nauset Marsh allows them to expand their knowledge base. "It's a small-scale version of what we've done in the Gulf [of Maine]," he says. "This project will aid our understanding of this type of coastal system." Anderson also hopes that at some point his research into the presence of cysts will extend into regions farther offshore, such as on Georges Bank.

"Managers want very much to know what's going on out there," he says. Anderson credits Sea Grant with having been involved in the search for answers regarding toxic blooms from a very early stage, recognizing the crisis and funding proposals. Sea Grant funded his Ph.D. work at the Massachusetts Institute of Technology. "Sea Grant can legitimately say they were there at the launch - of me and of HAB research in this region," he says.

Proposed hydrographic sampling stations (circles) with the Nauset Marsh estuary. These stations are distributed near significant shellfish resources, including Salt Pond and Mill Pond, at the geographic extremes of the estuary. These are sites with histories of high levels of PSP toxicity.