Temperature extremes reduce seagrass growth and induce mortality

Area of Science:

• Marine biology
• Ecology
• Climate change impacts

Background:

• Shallow coastal seagrass meadows face extreme heat up to 43°C during low tide.
• Seagrass ecosystems are vital for marine biodiversity and coastal protection.

Purpose of the Study:

• To investigate the impact of short-duration heatwaves on tropical seagrasses.
• To determine critical temperature thresholds for seagrass survival and function.

Main Methods:

• Four tropical seagrass species were exposed to experimental water temperatures of 35°C, 40°C, and 43°C for 6 days.
• Measurements included effective quantum yield (photosynthetic efficiency), growth, senescence, and mortality.
• Photosynthetic Photon Flux Density (PPFD) was also recorded.

Main Results:

• Temperatures of 35°C positively affected photosynthetic efficiency (ϕPSII) with no impact on growth or mortality.
• 40°C acted as a critical threshold, causing significant species-specific impacts on growth and mortality.
• Exposure to 43°C resulted in complete mortality within 2-3 days.

Conclusions:

• Increasing duration and intensity of marine heatwaves above 40°C pose a significant threat to tropical seagrass meadows.
• These findings highlight the vulnerability of seagrass ecosystems to climate change and the potential for ecological function disruption.