Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8371
Title: Spatial distribution of algicidal and growth-inhibiting bacteria associated with seagrass and macroalgae beds in Puget Sound
Author: Nobuharu Inaba, Vera L. Trainer, Yuka Onishi, Ken-Ichiro Ishii, S. Wyllie-Echeverria
Publication Year: 2016
Journal: Harmful Algae
Keywords: algicidal bacteria,harmful algal blooms,Heterosigma akashiwo,Alexandrium spp.,mitigation

The spatial distribution of algicidal bacteria and growth-inhibiting bacteria associated with seagrass and macroalgae were investigated during the summer of 2012 and 2013 throughout Puget Sound, WA, USA. In 2012, algicidal bacteria against the fish-killing raphidophyte Heterosigma akashiwo were isolated from the outer organic layer of biofilm on the common eelgrass, Zostera marina, in north Padilla Bay (2.77 x 106 CFU g-1 wt) and growth-inhibiting bacteria against the neurotoxin-producing dinoflagellate Alexandrium tamarense species complex were detected within the eelgrass canopy at Dumas Bay and North Bay at densities of ~108 CFU g-1 wt. From 1.8 x 101 – 4.1 x 103 CFU mL-1 of algicidal and growth-inhibiting bacteria against both A. tamarense and H. akashiwo were also detected in seawater adjacent to seven different eelgrass beds. In 2013, the the investigation was extended to include algicidal and growth-inhibiting bacteria associated with several seagrass and dominant macroalgae species in north Puget Sound. Algicidal bacteria against H. akashiwo were found on Z. marina and U. lactuca with the highest densities of 1.1 x 108 and 1.4 x 108 CFU g-1 wt, respectively, at Shallow Bay, Sucia Island, in the northern San Juan Archipelago region of Puget Sound. Growth-inhibiting bacteria against three different harmful species, H. akashiwo, A. tamarense and Karenia mikimotoi, were also detected on Z. marina, Z. japonica and U. lactuca. Cyst densities of Heterosigma and Alexandrium in the sediment were also investigated at five different eelgrass beds and in Westcott Bay (north of San Juan Island), a location where eelgrass disappeared in 2002. No cysts of Heterosigma and Alexandrium were found at any eelgrass beds, however H. akashiwo cysts were detected in Westcott Bay at 3400 cells g-1 wet sediment. These findings provide new insights on the ecology of algicidal and growth-inhibiting bacteria, and suggest that seagrass and macroalgae beds serve as a habitat for bacteria that help to mitigate harmful algal blooms in coastal waters. This work highlights the importance of protection and restoration of native seagrass and macroalgae in nearshore environments, in particular those regions where shellfish restoration initiatives are in place to satisfy a growing demand for seafood, to provide cleaner water via nutrient removal, and to assist with species recovery.

Theme: Sustainable, safe and secure seafood for healthy populations and vibrant communities
Foci: Provide scientific support to ensure safe seafood for healthy populations and characterize how human activities and climate affect risks from pathogens, chemical contaminants and biotoxins