Survival of biocalcifying shallow-marine benthic organisms in the coastal areas of the Arabian Gulf under conditions of global warming: Is there a limit to their resilience?

The western Arabian Gulf faces significant climate change risks, particularly from current and future global warming. The biota inhabiting coastal areas are increasingly threatened by fluctuating temperatures, on a daily, monthly, and yearly basis. Despite this perceived threat, very few studies have addressed this issue. Our study focuses on whether the benthic fauna in coastal areas have adapted to extreme heat exposure. To answer this question various sites in the western Arabian Gulf, notably the eastern coasts of Saudi Arabia and Bahrain were examined in this study. The initial results, based on datasets including remote sensing, deployed monitors, and in-situ measurements, show high temperatures during summer (exceeding 60 °C for land and 42 °C for water), potentially surpassing the thermal tolerance of benthic ectotherms such as mollusks, arthropods, annelids, and foraminifera. Spatial-temporal data indicate trends of increasing temperatures, especially from in-situ land measurements in the intertidal zones, with a significant temperature rise in the most recent period of measurement (2023–2024). Field sampling and laboratory heat exposure experiments reveal that local biocalcifying marine animals are highly adapted to heat exposure, particularly when submerged under water. Our observations suggest that although the local biocalcifiers demonstrate high survivability during thermal exposure, they are threatened by current and potentially future warming trends, as summer temperatures measured over the 2020–2024 study period already exceed their experimentally-determined thermal limits. Furthermore, our current work can give insight into similar environmental conditions that took place in the same regions/settings or even globally in the geologic past during climate warming events.