Marine heatwave and reduced light scenarios cause species‐specific metabolomic changes in seagrasses under ocean warming

Abstract

Summary Climate change and extreme climatic events, such as marine heatwaves (MHWs), are threatening seagrass ecosystems. Metabolomics can be used to gain insight into early stress responses in seagrasses and help to develop targeted management and conservation measures. We used metabolomics to understand the temporal and mechanistic response of leaf metabolism in seagrasses to climate change. Two species, temperate Posidonia australis and tropical Halodule uninervis, were exposed to a combination of future warming, simulated MHW with subsequent recovery period, and light deprivation in a mesocosm experiment. The leaf metabolome of P. australis was altered under MHW exposure at ambient light while H. uninervis was unaffected. Light deprivation impacted both seagrasses, with combined effects of heat and low light causing greater alterations in leaf metabolism. There was no MHW recovery in P. australis. Conversely, the heat‐resistant leaf metabolome of H. uninervis showed recovery of sugars and intermediates of the tricarboxylic acid cycle under combined heat and low light exposure, suggesting adaptive strategies to long‐term light deprivation. Overall, this research highlights how metabolomics can be used to study the metabolic pathways of seagrasses, identifies early indicators of environmental stress and analyses the effects of environmental factors on plant metabolism and health.

Comparative gene co-expression networks show enrichment of brassinosteroid and vitamin B processes in a seagrass under simulated ocean warming and extreme climatic events

“…Approximately 350 ramets were collected via SCUBA from growing edges of the meadow at an average depth of 1.5 m. The in situ temperature was 26.1°C ± 0.3°C (± standard error) and salinity was 40.2 PSU ± 0.2 PSU (Practical Salinity Units) at the time of collection. The details of transportation and planting are described in Jung et al (2023).…”

“…A mesocosm experiment was conducted over 18 weeks (Figure 1). A detailed description of the mesocosm setup can be found in Jung et al (2023). Briefly, 12 L × 1,800 L self-contained, recirculating, reinforced tanks were in a temperature-controlled glasshouse with ambient light and natural seawater.…”

“…After two weeks of MHW, temperatures were decreased in 'Heat' and 'Heat + Shade' tanks by −0.8°C increments over another five days, back to future warming temperatures (+1.5°C above baseline control) and held for one week to simulate a recovery period. Temperature, light, and salinity levels were monitored at the seagrass leaf canopy height throughout the experiment, as reported in the Supporting Information in Jung et al (2023).…”

“…Rising ocean temperatures and reduced light availability, for example, caused by flash flooding and subsequent sediment resuspension in the water column, are two key stressors for marine plants (Duarte et al, 2018). Each stressor has an effect in isolation; however, in combination, they can have additive or synergistic effects (Brook et al, 2008;Jung et al, 2023). Interactions among stressors can push seagrass populations above their functional threshold, where range contractions and extinctions are likely to occur (York et al, 2013;Lefcheck et al, 2017;Kendrick et al, 2019).…”

Above and below-ground bacterial communities shift in seagrass beds with warmer temperatures

“…Although slight temperature increases can in some cases enhance seagrass growth rates, once a species' thermal threshold is reached, there can be negative impacts (York et al, 2013;Anton et al, 2020;Nguyen et al, 2021). For example, prolonged marine heatwaves up to 3°C above ambient have caused seagrass mortality in temperate and subtropical regions Thomson et al, 2015;Serrano et al, 2021;Jung et al, 2023). While responses of some seagrasses to temperature changes have been well studied, the response of microbes and the role they play in ameliorating these environmental stressors has rarely been investigated (Garcias-Bonet et al, 2016;Fuggle et al, 2023).…”