Combined stable isotope records and skeletal growth properties of the reef-building coral Porites reveal biological response to environmental forcing relationship (early Tortonian, Crete/Greece)

Late Miocene reefs were widespread over the entire Mediterranean. Knowledge of their long-term sedimentary and ecological variability on orbital time-scales and their responses to climatic changes is well established, while understanding of annual to inter-annual dynamics is poor because of inappropriate coral preservation related to the dissolution and cementation of the skeletal aragonite. Exceptionally well-preserved Porites corals retaining the aragonite mineralogy and primary skeletal porosity have been reported by the authors previously from an early Tortonian mixed clastic-carbonate system at Psalidha site (Crete/Greece, Eastern Mediterranean). Here, we present a review of all sub-annually resolved stable isotope chronologies (δ¹⁸O, δ¹³C) and corresponding skeletal growth data (skeletal extension rate and density, calcification rate) available from the Psalidha site, covering a total of 266 years, together with data on sedimentary facies and paleontological inventory. Based on categories of present-day Porites regarding calcification properties and stable isotope systematics, we find average annual SST ~23 °C with mean seasonal SST amplitudes ~7.5 °C. Overall low skeletal growth was limited most during the cool seasons, fully consistent with paleontological inventory (low diversity of reef-building corals) and sedimentary facies, Mediterranean region geographic latitude (subtropics) and biogeography (near northern limit of global reef belt). No evidence for bleaching events has been identified so far. We discuss the growth responses of an important reef-building coral genus in the Late Miocene Mediterranean Sea to environmental variability on seasonal to decadal time-scales in the light of ancient climatic variability and modern reef dynamics during the ongoing reef crisis.