Skip to main content
2023 ESA Annual Meeting Main banner
Icon Legend
This session is not in your schedule.
This session is in your schedule. Click again to remove it.
Back

Contributed Talk

Session: : Physiological Ecology 4

COS 201-3 - New method from land to sea: a novel approach to rapidly assess thermal tolerance of kelp over a latitudinal range size

Wednesday, August 9, 2023
2:00 PM – 2:15 PM PDT
Location: E142

    Presenting Author(s)

  • RH

    Rosalie Harris

    PhD Student
    Australian National University, Australia

    • Coauthor(s)

  • AL

    Andy Leigh

    University of Technology Sydney, Australia

  • MC

    Melinda Coleman

    New South Wales Fisheries, National Marine Science Centre, 2 Bay Drive, Coffs Harbour, New South Wales 2450, Australia National Marine Science Centre, Southern Cross University, 2 Bay Drive, Coffs Harbour, New South Wales 2450, Australia Oceans Institute and School of Biological Sciences, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009, Australia, Australia

  • GW

    George Wood

    University of Western Australia, Australia

  • AM

    Antoine Minne

    University of Western Australia, Australia

  • CB

    Callum Bryant

    Australian National University, Australia

  • PA

    Pieter Arnold

    Australian National University, Australia

  • AN

    Adrienne Nicotra

    Australian National University, Australia

Abstract: Warming sea surface temperatures are contributing to widespread declines of kelp cover around the world and are causing significant range contractions in many species. Not only will average sea surface temperatures increase but so will the intensity and frequency of extreme events such as marine heatwaves. Kelp forests underpin vast ecological, economic, and cultural values in marine ecosystems and therefore characterising temperature thresholds is critical for predicting patterns of change and identifying species most vulnerable to extremes. Existing methods for characterising kelp thermal tolerance produce diverse metrics and are often time consuming, making comparisons between species and techniques difficult, hindering insight into global patterns of change. We developed a high throughput method to rapidly assess the photosynthetic thermal tolerance of kelp to produce a metric in ºC. This method employs temperature-dependent fluorescence (T-F0) curves under heating regimes to determine the critical temperature (Tcrit), i.e., the breakpoint between slow and fast rise fluorescence response to changing temperature, enabling rapid assays of photosynthetic thermal tolerance using a standardised metric. We tested this technique across two habitat-forming species along their entire eastern latitudinal range in Australia, matching sampling sites with genetically distinct populations to investigate correlate patterns between thermal tolerance and genetic diversity. We found that kelp populations with genes linked to heat tolerance also had the highest thermal tolerance (Tcrit), however thermal tolerance declined by about 10 ºC towards higher latitudes. We also found that overall photosynthetic efficiency (Fv/Fm) was reduced towards the range edges, indicating trade-offs for those populations to reside in sub-optimal, more extreme conditions. This method has the potential to identify and select individuals with high thermal tolerance along with increased genetic diversity to assist in 'future proofing' our kelp forests in a changing world. Temperature-dependent fluorescence curves and their derived metric, Tcrit, may offer a timely and powerful new method for the field of phycology, enabling characterisation and comparison of photosynthetic thermal tolerance of kelp across many populations, species and biomes.