Investigating Algicidal and Growth-inhibiting Bacteria associated with Seagrass and Macroalgae beds in Puget Sound

• Main Author: Inaba, Nobuharu
• Format: Text
• Language: English
• Published: Western CEDAR 2014
• Subjects: Terrestrial and Aquatic Ecology; Pacific; Shallow Bay; Sucia; Sucia Island; Crassostrea gigas
• Online Access: https://cedar.wwu.edu/ssec/2014ssec/Day3/2; https://cedar.wwu.edu/cgi/viewcontent.cgi?article=1463&context=ssec

Harmful Algal Blooms (HABs) caused by the fish-killing raphidophyte Heterosigma akashiwo and the neuro-toxic dinoflagellate of the genus Alexandrium, impact finfish and shellfish aquaculture in Puget Sound including Pacific Salmon (Oncorhynchus spp.), oysters (Crassostrea gigas; Ostrea lurida), mussels (Mytilus edulis), geoducks (Panopea generosa), etc. Previous studies in Japan have demonstrated that the density of algicidal bacteria (AB) and gowth-inhibiting bacteria (GIB) detected from biofilm on the seagrass Zostera marina was remarkably high. During the summer of 2012, using methods developed in Japan, we sampled the leaves of Z. marina and adjacent water from 14 sites in the Puget Sound. In 2013, we extended our survey to include samplings of other seagrass species as well as the water column surrounding various macroalgal species. Using a co-culturing method, the effects of algicidal and growth-inhibiting bacteria were tested against H. akashiwo and Alexandrium tamarense. The high densities (2.7 x 106 CFU g wet leaf-1) of H. akashiwo-killing bacteria and of A. tamarense growth-inhibiting bacteria (8.3 x 106 CFU g wet leaf-1) were both detected from Z. marina collected from north Padilla Bay in 2012. Interestingly, the bacteria that killed H. akashiwo showed no effects on A. tamarense and vice versa, indicating species specificity. Both AB and GIB against H. akashiwo were successfully isolated from 3 different species (Z. marina, Z. japonica and Ulva lactuca) in 2013. The high densities of H. akashiwo-killers were found from the leaves of Z. marina (1.0 x 108 CFU g wet leaf-1) and the green algae Ulva lactuca (1.3 x 108 CFU g wet weight-1) collected from Shallow Bay, on Sucia Island in the northern reach of Puget Sound and the highest density of H. akashiwo-GIB (2.8 x 108 CFU g wet weight-1) were detected from Z. japonica leaves collected from Padilla Bay, northern Puget Sound. Of the viable bacteria isolated from Z. japonica at Padilla Bay, 17% were identified as H. akashiwo-GIB. These findings provide a ...