Non-invasive monitoring of thermal stress in Patella depressa: insights into physiological responses to temperature

Mar Humet¹, Rocio Nieto-Vilela¹, Fernando P. Lima¹, Rui Sebra¹

¹CIBIO/BIOPOLIS, University of Porto, Portugal

The intertidal zone is one of the most physically demanding environments on Earth and has long served as a model for studying the effects of environmental stressors on organisms. These challenging conditions make it an ideal natural laboratory for investigating species’ responses to environmental stress, particularly as they approach their physiological limits.

Temperature is a key driver of physiological performance and survival, making accurate assessments of thermal stress crucial for forecasting the impacts of climate change. However, distinguishing natural variability from stress caused by extreme weather events remains a significant challenge. Sustainable monitoring programs capable of assessing heat stress in natural populations are therefore urgently needed.

In this study, we present the first results from a user-friendly, non-invasive technique that measures heartbeat frequency using an infrared sensor connected to a smartphone app. This method enabled the collection of real-time physiological data to assess thermal stress in Patella depressa, a keystone species of the rocky intertidal zone in the NE Atlantic. Combining this data with temperature measurements allowed for the evaluation of sub-lethal stress levels.

Our findings reveal a strong correlation between field-measured heart rate and temperature in P. depressa. Notably, we documented a deviation in baseline heartbeat frequency coinciding with a marine heatwave. Additionally, we observed significant differences in thermal stress responses based on solar exposure (sunlit vs. shaded locations) and animal size. This simple and accessible technique opens new avenues for monitoring physiological responses to sub-lethal stress in natural populations, providing valuable insights into the impacts of a changing climate.