Not Just Another Lovely Summer Day on the Water

It looks like nice summer day on the water, but Alexis Fischer (right) and Alice Alpert, graduate students in the MIT-WHOI Joint Program, are hard at work preparing instruments called sediment traps. They collect detritus and many types of organisms that fall from surface waters to sediments on the bottom of Nauset Marsh, a network of shallow channels and ponds at the Cape Cod National Seashore.

Nauset Marsh supports abundant shellfish and recreational and commercial shellfishers. But it also harbors a growing population of harmful algae. Shellfish consume the algae, and people who eat the shellfish can become sick or even die. Massachusetts officials monitor shellfish to prevent human illness and close the marsh to shellfishing when necessary.

The algal species that produces shellfish toxin forms resting cysts that settle in sediments and germinate in spring to grow into harmful algal blooms, or “red tides.”

Working with her Ph.D. advisor, WHOI biologist Don Anderson, Fischer is trying to establish what conditions start and stop blooms­—in an effort to improve the ability of shellfishers and coastal resource managers to forecast the onset of red tides.

“Many phytoplankton have evolved behavioral and life-cycle strategies, such as resting cysts, for surviving seasonal stresses of intense cold, heat, or light,” Fischer said. “My work is on how the cysts use internal and environmental cues, such as temperature, to coordinate the timing of their germination for when conditions will be most favorable for blooms.

“Many plant seeds and bulbs require weeks or months of chilling to germinate. I used this as inspiration to design cyst germination experiments that mimic winter chilling in Nauset.”