Experimental Data to" Small-scale thermal habitat variability may not determine seagrass resilience to climate change"

Description

Technical info

Experimental Setup and Treatments:

Eelgrass (Zostera marina) was collected from ten meadows in the Koster Sea archipelago, Swedish west coast, between June 28 and July 2, 2021. Samples were taken by scuba diving at 1–3 m depth. Each meadow was approximately 7 km apart (range: 1.5–14 km). Eelgrass shoots were transported to Tjärnö Marine Laboratory, where they acclimated in flow-through seawater for ~20 days.

Experiments were conducted in BALTOTRON outdoor mesocosms at Tjärnö Marine Laboratory. Eelgrass shoots were planted in 12 L bags with sediment and distributed across ten 900 L tanks. Treatments included:

1. Ambient conditions – Natural temperature and salinity fluctuations recorded at the station.
2. Climate change conditions – +4.7°C warming and -5.5 PSU freshening, based on long-term data

Response Traits and Measurements

Before the Experiment:

• Total Wet Weight Start (g): The combined wet weight of all plant components at the beginning of the experiment.
• Leaf Number Start: The number of leaves per plant at the start.
• Infection Labyrinthula (Start): Initial infection levels with Labyrinthula (presence/ absence).

After the Experiment:

• Dead End: Individuals that did not survive until the end (1), alive (0)
• Wet Weight Leaf End (g): Wet weight of leaves at the end.
• Leaf Number End: Total number of leaves at the end.
• Wet Weight Roots End (g): Wet weight of roots at the end.
• Wet Weight Total End (g): Total wet weight (leaves + roots) at the end.
• Shoots End: Number of shoots per plant.
• New Leaf End: Number of new leaves grown during the experiment.
• Dry Weight Shoots End (g): Dry weight of shoots.
• Dry Weight Roots End (g): Dry weight of roots.
• Dry Weight Total End (g): Total dry weight (leaves + roots).
• Infection Labyrinthula (End): Infection levels with Labyrinthula at the end (presence/ absence).

The increase in, for example, wet weight and number of leaves was calculated as the difference between the start and end values for each measured trait.

Differences in growth and wet weight were calculated to evaluate the effect of the climate change treatment, using a paired-design where one shoot from the same genetic individual was assigned to the "ambient" treatment and the other to the "climate change" treatment.