Microbial Community Dynamics during a Harmful Chrysochromulina leadbeateri Bloom in Northern Norway

A harmful algal bloom occurred in late spring 2019 across multiple, interconnected fjords and bays in northern Norway. The event was caused by the haptophyte Chrysochromulina leadbeateri and led to severe fish mortality at several salmon aquaculture facilities. This study reports on the spatial and temporal succession dynamics of the holistic marine microbiome associated with this bloom by relating all detectable 18S and 16S rRNA gene amplicon sequence variants to the relative abundance of the C. leadbeateri focal taxon. A k-medoid clustering enabled inferences on how the causative focal taxon cobloomed with diverse groups of bacteria and microeukaryotes. These coblooming patterns showed high temporal variability and were distinct between two geographically separated time series stations during the regional harmful algal bloom. The distinct blooming patterns observed with respect to each station were poorly connected to environmental conditions, suggesting that other factors, such as biological interactions, may be at least as important in shaping the dynamics of this type of harmful algal bloom. A deeper understanding of microbiome succession patterns during these rare but destructive events will help guide future efforts to forecast deviations from the natural bloom cycles of the northern Norwegian coastal marine ecosystems that are home to intensive aquaculture activities

Disability and Social Theory: New Developments and Directions

In the Spring of 2019, a harmful algal bloom (HAB) of Chrysochromulina leadbeateri decimated 14 500 tonnes of caged salmon in the Northern Norwegian coastal regions. C. leadbeateri is a natural part of the marine microbiome along the Norwegian coast, and similar events have happened in the past. To heighten our understanding of how these HABs develops, and capacity of the causal agent as a harmful species, we’ve assessed the environmental and enumeration data of C. leadbeateri density in Northern Troms, collected by Akvaplan Niva during the 2019 HAB, in concurrence with the assessment of several microbial isolation and genomic extraction techniques. The highest cell counts of C. leadbeateri existed in Balsfjorden, where, at most, an estimated ∼49 million cells/L resided at 3 m below the surface. Further, we found a temporal correspondence between an increase in C. leadbeateri cell counts and increased salmon mortality at a locality in Kattfjorden. Generally, there was a higher density of C. leadbeateri at 3, compared with 10 m. This discrepancy could plausibly be attributed to divergent water densities between the two measurement depths. The algal isolation and genomic extraction attempts proved largely unsuccessful. Thus, we provide a series of corrections to the techniques used, to ensure that future attempts may be more efficacious