Abstract
Abstract Increasing ocean warming and marine heatwaves will have important consequences for the world’s seagrasses. Predicting impacts of thermal stress on seagrasses depends on understanding their temperature-productivity responses. Here, we examine these responses for eelgrass ( Zostera marina ) and how they are influenced by plant acclimation to seasonal and localized physical conditions. Eelgrass was collected seasonally from two sites in Nova Scotia (NS) Canada that were characterized by contrasting physical conditions, with temperature regime being a dominant feature. Laboratory incubations measured oxygen production and consumption rates by eelgrass leaves and roots-rhizomes from 5 to 40 °C. Unimodal temperature dependence of net photosynthetic rate and whole plant net productivity was modelled and maximum productivity ( P max ) and optimal temperatures ( T opt ) were estimated. Both net photosynthetic rate and net plant productivity were more peaked and bell-shaped across increasing temperature for plants from a warm highly variable temperature regime compared to plants from a cool less variable regime. P max and T opt were highest in warm relative to cool regime plants across all seasons. Furthermore, P max was lower and T opt was higher when seasonal ambient temperatures increased. T opt for whole plant productivity (22.5 to 28.5 °C) was used to create a thermal risk map for eelgrass, which indicated that 20%, 8.5%, 4.6%, and 1.3% of predicted eelgrass habitat in NS exceeds 22 °C, 24 °C, 26 °C and 28 °C, respectively, for at least 1 h annually. Our results show that even northern temperate eelgrass can be heat stressed, and that plant acclimation to seasonal and localized conditions should be considered when evaluating seagrass thermal risk.
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Claims 10
Claim · model-written summary
Photosynthetic and whole-plant productivity curves were more peaked for plants from a warm variable regime.
- Taxon
- Eelgrass
Zostera marinat0 - Outcome
- net photosynthetic rate and net plant productivitye0
- Direction
- more peakede0
- Comparator
- cool less variable regimee0
- Setting
- warm highly variable temperature regimee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both net photosynthetic rate and net plant productivity were more peaked and bell-shaped across increasing temperature for plants from a warm highly variable temperature regime compared to plants from a cool less variable regime”
t0“Eelgrass, Zostera marina”
Claim · model-written summary
Maximum productivity was highest in warm-regime plants across seasons.
- Taxon
- EelgrassZostera marinat0
- Outcome
- P maxe0
- Direction
- higheste0
- Qualifier
- across all seasonse0
- Comparator
- cool regime plantse0
- Setting
- warme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“P max and T opt were highest in warm relative to cool regime plants across all seasons”
t0“Eelgrass, Zostera marina”
Claim · model-written summary
Optimal temperature was highest in warm-regime plants across seasons.
- Taxon
- EelgrassZostera marinat0
- Outcome
- T opte0
- Direction
- higheste0
- Qualifier
- across all seasonse0
- Comparator
- cool regime plantse0
- Setting
- warme0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“P max and T opt were highest in warm relative to cool regime plants across all seasons”
t0“Eelgrass, Zostera marina”
Claim · model-written summary
Maximum productivity was lower as seasonal ambient temperature increased.
- Taxon
- EelgrassZostera marinat0
- Outcome
- P maxe0
- Direction
- lowere0
- Setting
- seasonal ambient temperatures increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“P max was lower and T opt was higher when seasonal ambient temperatures increased”
t0“Eelgrass, Zostera marina”
Claim · model-written summary
Optimal temperature was higher as seasonal ambient temperature increased.
- Taxon
- EelgrassZostera marinat0
- Outcome
- T opte0
- Direction
- highere0
- Setting
- seasonal ambient temperatures increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“P max was lower and T opt was higher when seasonal ambient temperatures increased”
t0“Eelgrass, Zostera marina”
Claim · model-written summary
Whole-plant productivity optimal temperature ranged from 22.5 to 28.5 °C.
- Taxon
- EelgrassZostera marinat0
- Outcome
- T opt for whole plant productivitye0
- Value
- 22.5 to 28.5 °Ce0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“T opt for whole plant productivity (22.5 to 28.5 °C)”
t0“Eelgrass, Zostera marina”
Claim · model-written summary
The risk map estimated 20% of predicted habitat exceeded 22 °C for at least one hour annually.
- Taxon
- eelgrassZostera marinae0
- Outcome
- predicted eelgrass habitat in NS exceeds 22 °Ce0
- Value
- 20%e0
- Qualifier
- for at least 1 h annuallye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“20%, 8.5%, 4.6%, and 1.3% of predicted eelgrass habitat in NS exceeds 22 °C, 24 °C, 26 °C and 28 °C, respectively, for at least 1 h annually”
Claim · model-written summary
The risk map estimated 8.5% of predicted habitat exceeded 24 °C for at least one hour annually.
- Taxon
- eelgrassZostera marinae0
- Outcome
- predicted eelgrass habitat in NSe0
- Value
- 8.5%e0
- Qualifier
- 24 °Ce0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“20%, 8.5%, 4.6%, and 1.3% of predicted eelgrass habitat in NS exceeds 22 °C, 24 °C, 26 °C and 28 °C, respectively, for at least 1 h annually”
Claim · model-written summary
The risk map estimated 4.6% of predicted habitat exceeded 26 °C for at least one hour annually.
- Taxon
- eelgrassZostera marinae0
- Outcome
- predicted eelgrass habitat in NSe0
- Value
- 4.6%e0
- Qualifier
- 26 °Ce0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“20%, 8.5%, 4.6%, and 1.3% of predicted eelgrass habitat in NS exceeds 22 °C, 24 °C, 26 °C and 28 °C, respectively, for at least 1 h annually”
Claim · model-written summary
The risk map estimated 1.3% of predicted habitat exceeded 28 °C for at least one hour annually.
- Taxon
- eelgrassZostera marinae0
- Outcome
- predicted eelgrass habitat in NSe0
- Value
- 1.3%e0
- Qualifier
- 28 °Ce0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“20%, 8.5%, 4.6%, and 1.3% of predicted eelgrass habitat in NS exceeds 22 °C, 24 °C, 26 °C and 28 °C, respectively, for at least 1 h annually”