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ABSTRACT Successful rearing of fish in hatcheries is critical for conservation, recreational fishing, commercial fishing through wild stock enhancements, and aquaculture production. Flowthrough (FT) hatcheries require more water than recirculating aquaculture systems (RAS), which enable up to 99% of their water to be recycled, thus significantly reducing environmental impacts. Here, we evaluated the biological and physical microbiome interactions of three Atlantic salmon hatcheries (RAS n  = 2, FT n  = 1). Gill, skin, and digesta from six juvenile fish along with tank biofilms and water were sampled from tanks in each of the hatcheries (60 fish across 10 tanks) to assess the built environment and mucosal microbiota using 16S rRNA gene sequencing. The water and tank biofilm had more microbial richness than fish mucus, while skin and digesta from RAS fish had 2 times the richness of FT fish. Body sites each had unique microbiomes ( P  < 0.001) and were influenced by hatchery system type ( P  < 0.001), with RAS being more similar. A strong association between the tank and fish microbiome was observed. Water and tank biofilm richness was positively correlated with skin and digesta richness. Strikingly, the gill, skin, and digesta communities were more similar to that in the origin tank biofilm than those in all other experimental tanks, suggesting that the tank biofilm has a direct influence on fish-associated microbial communities. Lastly, microbial diversity and mucous cell density were positively associated with fish growth and length. The results from this study provide evidence for a link between the tank microbiome and the fish microbiome, with the skin microbiome as an important intermediate. IMPORTANCE Atlantic salmon, Salmo salar , is the most farmed marine fish worldwide, with an annual production of 2,248 million metric tons in 2016. Salmon hatcheries are increasingly changing from flowthrough toward recirculating aquaculture system (RAS) design to accommodate more control over production along with improved environmental sustainability due to lower impacts on water consumption. To date, microbiome studies of hatcheries have focused either on the fish mucosal microbiota or on the built environment microbiota but have not combined the two to understand their interactions. Our study evaluates how the water and tank biofilm microbiota influences the fish microbiota across three mucosal environments (gill, skin, and digesta). Results from this study highlight how the built environment is a unique source of microbes to colonize fish mucus and, furthermore, how this can influence fish health. Further studies can use this knowledge to engineer built environments to modulate fish microbiota for beneficial phenotypes. 

Magmatic and hydrothermal systems are intimately linked, significantly overlapping through time but persisting in different parts of a system. New preliminary U-Pb and trace element petrochronology from zircon and titanite demonstrate the protracted and episodic record of magmatic and hydrothermal processes in the Alta stock–Little Cottonwood stock plutonic and volcanic system. This system spans the upper ~11.5 km of the crust and includes a large composite pluton (e.g., Little Cottonwood stock), dike-like conduit (e.g., Alta stock), and surficial volcanic edifices (East Traverse and Park City volcanic units). A temperature–time path for the system was constructed using U-Pb and tetravalent cation thermometry to establish a record of >10 Myr of pluton emplacement, magma transport, volcanic eruption, and coeval hydrothermal circulation. Zircons from the Alta and Little Cottonwood stocks recorded a single population of apparent temperatures of ~625 ± 35 °C, while titanite apparent temperatures formed two distinct populations interpreted as magmatic (~725 ± 50 °C) and hydrothermal (~575 ± 50 °C). The spatial and temporal variations required episodic magma input, which overlapped in time with hydrothermal fluid flow in the structurally higher portions of the system. The hydrothermal system was itself episodic and migrated within the margin of the Alta stock and its aureole through time, and eventually focused at the contact of the Alta stock. First-order estimates of magma flux in this system suggest that the volcanic flux was 2–5× higher than the intrusive magma accumulation rate throughout its lifespan, consistent with intrusive volcanic systems around the world. 

Summary In seed plants, 1‐aminocyclopropane‐1‐carboxylic acid (ACC) is the precursor of the plant hormone ethylene but also has ethylene‐independent signaling roles. Nonseed plants produce ACC but do not efficiently convert it to ethylene. InArabidopsis thaliana, ACC is transported by amino acid transporters, LYSINE HISTIDINE TRANSPORTER 1 (LHT1) and LHT2. In nonseed plants,LHThomologs have been uncharacterized.Here, we isolated an ACC‐insensitive mutant (Mpain) that is defective in ACC uptake in the liverwortMarchantia polymorpha. Mpaincontained a frameshift mutation (1 bp deletion) in the MpLHT1coding sequence, and was complemented by expression of a wild‐type MpLHT1transgene. Additionally, ACC insensitivity was re‐created in CRISPR/Cas9‐Mplht1knockout mutants. We found that MpLHT1 can also transportl‐hydroxyproline andl‐histidine.We examined the physiological functions of MpLHT1in vegetative growth and reproduction based on mutant phenotypes. Mpainand Mplht1plants were smaller and developed fewer gemmae cups compared to wild‐type plants. Mplht1mutants also had reduced fertility, and archegoniophores displayed early senescence.These findings reveal that MpLHT1 serves as an ACC and amino acid transporter inM. polymorphaand has diverse physiological functions. We propose that MpLHT1 contributes to homeostasis of ACC and other amino acids inM. polymorphagrowth and reproduction.