Extreme climate events lower resilience of foundation seagrass at edge of biogeographical range. (6th August 2014)

• Record Type: Journal Article
• Authors: Fraser, Matthew W.; Kendrick, Gary A.; Statton, John; Hovey, Renae K.; Zavala‐Perez, Andrea; Walker, Diana I.; Lee, John
• Is Part Of: Journal of ecology. Volume 102:Number 6(2014:Nov.)
• Page Start: 1528
• Page End: 1536
• Publication Date: 2014-08-06
• Subjects: Plant ecology -- Periodicals; 577.05
• DOI: 10.1111/1365-2745.12300
• Languages: English
• ISSNs: 0022-0477

Abstract

<abstract abstract-type="main" id="jec12300-abs-0001"> <title>Summary</title> <p> <list id="jec12300-list-0001" list-type="order"> <list-item> <p>Extreme climatic events will dictate the response of ecosystems to climate change, yet are understudied in marine ecosystems. The interaction of stressors from such events has the potential to amplify negative impacts and drive ecosystems into alternate states.</p> </list-item> <list-item> <p>Here, we show a drastic response of a temperate seagrass species (<italic>Amphibolis antarctica</italic>) in Shark Bay – a World Heritage Site in Western Australia at a temperate–tropical transition zone – to two stressors driven by concurrent extreme climatic events: a marine heatwave (Ningaloo Niña) and the Gascoyne floods that impacted the west coast of Australia in the austral summer of 2010–2011.</p> </list-item> <list-item> <p>Widespread defoliation (leaf loss) of <italic>A. antarctica</italic> was observed in the months following the extreme events and was highest at sites affected by flooding (Wooramel River floods). We propose that the negative impact was magnified by the synergistic interactions both stressors had on the carbon balance of the plant. The elevated temperatures increased plant demand for carbon, which could not be met through photosynthesis due to turbid floodwaters reducing light availability, resulting in the plant having a negative carbon balance.</p> </list-item> <list-item> <p>Two years following the extreme events, recovery of leaf biomass was evident, though still 7–20% of historical averages. In contrast, below‐ground biomass decreased by an order of magnitude in the two years following the events. As below‐ground reserves underpin the tolerance of large seagrass species like <italic>A. antarctica</italic> to disturbances, the declining trajectory of below‐ground biomass will likely manifest as a loss of resilience in <italic>A. antarctica</italic> to future disturbances.</p> </list-item> <list-item> <p> <italic>Synthesis</italic>. Given the ecological importance of <italic>Amphibolis antarctica</italic> in Shark Bay as a foundation species – accounting for 85% (˜3700 km<sup>2</sup>) of the cover of seagrasses in Shark Bay – predicted increases in the frequency and magnitude of similar climatic events could have catastrophic implications for the future of this World Heritage embayment. Where extreme climatic events overlap and cause multiple, synergistic stressors to plant communities, ecological responses are likely to be more extreme, particularly in ecosystems where foundation species exist near upper thermal tolerance limits.</p> </list-item> </list> </p> </abstract>