Relation between the relative abundance and collapse of Aphanizomenon flos-aquae and microbial antagonism in Upper Klamath Lake, Oregon

Aphanizomenon flos-aquae (AFA) is the dominant filamentous cyanobacterium that develops into blooms in Upper Klamath Lake, Oregon, each year. During AFA bloom and collapse, ecosystem conditions for endangered Lost River and shortnose suckers deteriorate, thus motivating the need to identify processes that limit AFA abundance and decline. Here, we investigate the relations between AFA and other members of the microbial community (photosynthetic and nonphotosynthetic bacteria and archaea), how those relations impact abundance and collapse of AFA, and the types of microbial conditions that suppress AFA. We found significant spatial variation in AFA relative abundance during the 2016 bloom period using 16S rRNA sequencing. The Pelican Marina site had the lowest AFA relative abundance, and this was coincident with increased relative abundance of Candidatus Sericytochromatia, Flavobacterium, and Rheinheimera, some of which are known AFA antagonists. The AFA collapse coincided with phosphorus limitation relative to nitrogen and the increased relative abundance of Cyanobium and Candidatus Sericytochromatia, which outcompete AFA when dissolved inorganic nitrogen is available. The data collected in this study indicate the importance of dissolved inorganic nitrogen combined with microbial community structure in suppressing AFA abundance.

Transforming growth factor-β1 expression in endangered age-0 shortnose suckers (Chasmistes brevirostris) from Upper Klamath Lake, OR relative to histopathology, meristic, spatial, and temporal data

During July-September of 2008, 2009, and 2010 endangered age-0 juvenile shortnose suckers were sampled from Upper Klamath Lake, OR in a health evaluation that included the measurement of transforming growth factor - beta (TGF-β) expression in spleen in combination with a histopathology assessment. This analysis was performed to determine if the expression of this immuno-regulator could be used as a component of a larger health evaluation intended to identify potential risk-factors that may help to explain why very few of these fish survive to age-1. Potential associations between TGF-β1 expression, histopathological findings, meristic data as well as temporal and spatial data were evaluated using analysis-of-variance. In this analysis, the absence or presence of opercula deformity and hepatic cell necrosis were identified as significant factors in accounting for the variance in TGF-β1 expression observed in age-0 shortnose suckers (n = 122, squared multiple R = 0.989). Location of sample collection and the absence or presence of anchor worms (Lernaea spp.) were identified as significant cofactors. The actual mechanisms involved with these relationships have yet to be determined. The strength, however, of our findings support the concept of using TGF-β1 expression as part of a broader fish health assessment and suggests the potential for using additional immunologic measures in future studies. Specifically, our results indicate that the measure of TGF-β1 expression in age-0 shortnose sucker health assessments can facilitate the process of identifying disease risks that are associated with the documented lack of recruitment into the adult population.