OOS 32-8
Collaborative research identifies environmental processes leading to harmful algal blooms off the California coast
Marine phytoplankton, the primary producers at the base of most ocean food webs, are essential to life in our biosphere. Blooms of some algae have harmful effects: producing toxic substances that enter the food web, the seafood supply, or the air, or depleting oxygen in seawater during bacterial degradation of senescent blooms. Harmful blooms caused by algae, such as the diatom Pseudo-nitzschia or the dinoflagellate Alexandrium, pose significant threats to fisheries and aquaculture, and human health. Increasing occurrence of these blooms motivated MBARI to undertake collaborative research to understand the nature and causes of these events, as a first step toward predicting and mitigating these threats. In 2013, two multi-institutional algal bloom ecology experiments examined regions along the California coast known to be “hotspots”—San Pedro Bay (in spring) and Monterey Bay (in fall).
During these experiments, researchers coordinated use of satellites, ships, autonomous underwater vehicles, and moored instruments such as MBARI’s Environmental Sample Processors (robotic DNA labs) to detect targeted algal species and their toxins. Novel web-based tools allowed all participants to track the experiment and examine incoming sensor data. Real-time analysis of environmental data from the various sensors autonomously triggered sample collections when conditions indicated a bloom.
Results/Conclusions
Samples from the 2013 experiments are still undergoing microscopic and molecular analyses to reveal the composition and variability of the overall microalgal community, as well as harmful algal species. The integrated data system used in the experiments revealed relationships between changes in the environment and increased abundance of toxin-producing algae. Autonomous vehicles allowed for extended observations and high-resolution sensing in space and time, permitting detailed examination of environmental changes, which in turn, influenced algal communities being tracked by the Environmental Sample Processors.
The wide variation in concentrations of harmful algae illustrated that significant environmental variability often accompanies the emergence of target species. The following sequence of events demonstrates one process by which blooms of the harmful Pseudo-nitzschia diatoms may be initiated in San Pedro Bay. Low densities of Pseudo-nitzschia are often found in deeper water (20 to 50 meters below the surface). Without much sunlight, these algae are often dormant or reproduce very slowly. When strong northwest winds blow across waters just offshore, they push the surface water away from shore and bring deeper water and Pseudo-nitzschia up toward the surface. After a few days in the sunlit surface waters, the diatoms begin to reproduce rapidly, forming a bloom.