The waters of Chiniak Bay, off the coast of Kodiak, Alaska, were unusually glassy on an early morning in mid-August. As the NOAA research boat motored out of Near Island Harbor, the fog was so dense that local seafood processing plants, a major source of employment for Kodiak Island, were invisible. Occasionally, a sea otter or puffin appeared a few feet from the boat before dipping beneath the surface or disappearing in the mist.
On the way out to the first sampling station, NCCOS scientists on board prepared their supplies: labeling sample collection vials, readying the spring-loaded closure on a water sampling device known as a Niskin bottle, and double-checking the knots that secured the plankton net and Conductivity, Temperature, and Depth profiler (CTD) to the railings. The process was vital to tracking the extent and conditions of harmful algal blooms (HABs) in southwestern Alaska. Of particular interest for this sampling excursion was a toxic species called Alexandrium catenella, known to cause paralytic shellfish poisoning, or PSP, which has caused fatalities in the state as recently as 2020.
As the boat approached the first site, the captain killed the engines, and in the absence of noise from the twin outboards, the only sound heard in the fog was the soft slosh of water beneath the metal hull. The scientists set to work.
On the starboard side of the boat, one of the scientists deployed the CTD, a bundle of sensors housed in a four-foot-long metal frame, lowered into the water using a pulley. The deepest areas of Chiniak Bay can be several hundred meters down, and the scientist fed sections of rope through the pulley hand over hand until the CTD reached the seafloor. On its descent, the CTD collects measurements on the saltiness of the water (conductivity), as well as its temperature and depth in the water column, creating a vertical profile of oceanic conditions. These data are useful for monitoring and forecasting HABs like Alexandrium because environmental factors like salinity and temperature can play an important role in bloom dynamics, particularly as Alaska’s waters continue to warm.
Meanwhile, on the port side of the deck, other scientists collected samples of water to test for Alexandrium back at the laboratory. Since HABs are most likely to form near the surface where the plantlike organisms take in sunlight, the researchers lowered the Niskin bottle on a rope to one- and four-meter depths. When the bottle reached the desired depth, a scientist slid a metal weight down the rope into the water. A jolt on the rope signaled the weight hitting the spring-loaded mechanism that kept the bottle open, causing it to snap shut around a sample of seawater. The scientists then pulled the Niskin bottle back onboard and poured its contents into a collection bucket for filtration through a fine-meshed plankton net. Back in the lab, the team planned to analyze these samples for algae content, as well as for molecular methods that can tell researchers whether toxin-producing genes in Alexandrium cells are active.
The scientists repeated these steps at twelve other sites throughout the bay that day. During the last sampling session of the afternoon, the fog finally cleared, revealing dozens of fishing boats returning to the harbor with their catch. The data collected then and throughout the rest of the expedition would eventually be used to model Alexandrium bloom risk for southwestern Alaska, but in the moment, the boats were a floating reminder of why the data matter: to protect Alaska’s coastal community and economy.
This work is authorized by the Harmful Algal Bloom and Hypoxia Research and Control Act (HABHRCA) 33 U.S.C. §§ 4001 et seq.
This Log Book entry was written by Beryl Kahn.