New Database Maps Heat Tolerance of Critical Marine Plants to Predict Ocean Warming Impacts

Marine macrophytes, including seagrasses and canopy-forming seaweeds, are foundational species that underpin coastal ecosystems and provide critical ecological functions. These vital habitats are increasingly impacted by anthropogenic climate change, with temperature extremes posing significant challenges. Recognizing this, a recent study aimed to compile experimentally-derived upper thermal limits (T_limit) for these habitat-forming marine macrophytes into a centralized database, enabling further research and insight into how populations and species may respond to current and future warming oceans.

Through an extensive search of scientific literature, the researchers meticulously compiled 365 T_limit estimates from 63 studies, encompassing 75 distinct species globally. Their findings revealed considerable variation in thermal tolerances: seaweeds (kelps and fucoids) exhibited T_limit values ranging from 15 to 36 °C, while seagrasses demonstrated a higher tolerance, ranging from 25 to 48 °C. The study also highlighted that these thermal limits are not static, increasing with decreasing latitude and influenced by factors such as life history stage, experimental duration, and the specific response variable chosen to determine the threshold.

Despite this comprehensive compilation, the newly established database revealed several inherent biases, particularly concerning geographical regions and target species, indicating gaps in our current understanding. The existing variation and uncertainty in reported T_limit values significantly impede our ability to accurately predict suitable thermal habitats for marine macrophytes in a rapidly changing climate. As lead author Smith notes in the paper, "Improved understanding of upper thermal thresholds is needed to improve predictions of current and future impacts of ocean warming, which will inform approaches to management and conservation of wider coastal communities and ecosystems."