Physiological and Biochemical Responses of Saltmarsh Plant Spartina alterniflora to Long-term Wave Exposure: A Laboratory Study

Recently, ecosystem-based flood defense comprising salt-marsh as a key component has seen increasing applications worldwide for its multi-functionality and cost-effectiveness. While numerous laboratory experiments have been performed to explore the wave-attenuation effects of saltmarsh plants that are critical to its flood protection function, to our knowledge, little is known on the physiological and biochemical responses of saltmarsh plants to long-term wave exposure, presumably due to the constraint that traditional wave generator fails to provide long-term controllable wave conditions necessary for physiological experiments. In this study, a long-term shallow water wave simulator using slider-crank mechanism was built in the laboratory to address this gap. Experiments using the wave simulator were conducted for 8 weeks in a greenhouse. After being acclimatized, salt-marsh plant S. alterniflora individuals (initial height 35cm) collected from the Yellow River Estuary were transplanted in three replicate streamlined cuboid containers (12cm×12cm×20cm), which were partially submerged in the test tank, and undertook horizontal sinusoidal motion imposed by the slider-crank mechanism to mimic plants exposed to shallow water waves. Two wave heights (4.1cm, 5.5cm) and two wave periods (2s and 3s) were tested in a factorial experiment, as well as a no wave condition as control. Key physiological and biochemical parameters characterizing the plant growth, antioxidant defense and photosynthesis ability were measured to explore the plant response. Differences between the wave-treatment and control groups as well as those among the wave-treatment groups were analyzed to elucidate the wave effects. The experimental facility developed in this study proves to be an effective tool for studying response of salt-marsh plants to long-term wave exposure, which has important implications for salt-marsh conservation and utilization such as ecosystem-based flood defense.