THERMAL TOLERANCE OF THE SEA VEGETABLE CROP Alaria esculenta

Seaw eed aquaculture is expanding rapidly along the Maine coast , but will be increasingly dependent on strains that are tolerant to coastal warming. We examined temperature tolerance of the edible kelp  Alaria esculenta (L.) Greville with lab oratory experiments,  transcriptomic analyses, and  grow-out  of experimental strains on  a  sea farm.

We cultured gametophyte seedstocks from northern (Lubec ) and southern (Two Lights) Maine.  Replicates were maintained at 12 °C (controls) or slowly acclimated 1 °C/12 h to 22 °C, with gradual return to 12 °C three days later (heat acclimation treatment). Gametophyte health was affected by treatment, but there was no effect of source location (repeated measures MANOVA, treatment: p = 0.002, location: p = 0.423). Most (90%)  gametophytes recovered from  the  heat acclimation . RNA was extracted from heat-acclimated and control treatments throughout the experiment to analyze gene expression. Preliminary analysis of transcript abundance profiles indicates that clusters of co- expressed genes in functional categories associated with temperature acclimation had distinct signatures between source populations.

Control and acclimated strains from both source locations were each blended within treatment,  and  seeded separately to produce juvenile sporophytes  that grew in a  common garden  tank  at  our aquaculture center  (CCAR) before  transfer  of seeded spools to a sea farm .  Blade surface area was measured  periodically during the growing season. B oth treatment and  source  location of the gametophyte seedstocks significantly affected the next-generation sporophyte blade area (ANOVA, treatment: p ≤ 0.003, location: p ≤ 0.010 ). Thermal acclimation of gametophytes positively affected next-generation sporophytes.  Acquisition now of wild strains and acclimation treatments in culture will help secure resilient  Alaria aquaculture in warming waters.