Abstract
The invasion of natural communities by non-indigenous species represents one of the most serious threats to biodiversity. Understanding the ecophysiology of invasive species can provide insights into potential physiological handicaps relative to native species. By doing so, we can leverage the development of ecoengineering solutions for the removal of non-indigenous species, preferably using non-chemical methods. Spartina patens is a known invasive species of cordgrass aggressively proliferating in Mediterranean salt marshes, producing impenetrable monospecific stands. As its occurrence is delimited by the upper high tide water level, we hypothesized that S. patens is intolerant to waterlogging. Therefore, we developed a field experiment where strands of S. patens were kept waterlogged over the entire tidal cycle for 30 days. At the end of the experimental period, plants in the trial plots exhibited severe stress symptoms at different physiological levels compared with control plots (no intervention). At the photobiological level, intervened plants exhibited lower efficiency in producing chemical energy from light, whilst at the biochemical level waterlogging impaired the antioxidant system and increased lipid peroxidation products. Furthermore, the application of chlorophyll a pulse amplitude modulated (PAM) fluorometry, a non-invasive technique, allowed us to evaluate the effectiveness of the implemented measures, being the tool that provided the best separation between the control and intervened population. Considering the physiological traits observed here, ecoengineering solutions based on increased waterlogging of S. patens stands, can be a low-cost and efficient measure to reduce the spreading and growth of this invasive species in the Mediterranean and other salt marshes worldwide with little disturbance.
Highlights
Salt marshes provide a wide range of ecological services, including nursery habitats for many animals, protection against coastal erosion, water purification, having the considerable capacity to store and sequester carbon, and are key players in the ecosystem natural remediation capacity (Couto et al, 2013; Teixeira et al, 2014; Duarte et al, 2018, 2021), being these services valuated in several millions of euros per year (Duarte et al, 2021)
Observing the Kautsky plots resultant from the in vivo pulse amplitude modulated (PAM) fluorometric analysis, lower fluorescence values could be observed in plants subjected to the treatment when compared with control plants (Figure 2)
The four energy fluxes [Figure 3: A, energy absorbed transported within the electron transport chain (ETC) by the photosystem II (PS II) antennae (ABS/CS); B, (ET0/CS); and D, the energy dissipation flux (DI0/CS)] energy trapped inside the PS II (TR0/CS); C, energy showed the same pattern presenting lower values in the waterlogged plants, that decrease was only statistically significant for TR0/CS and ET0/CS
Summary
Salt marshes provide a wide range of ecological services, including nursery habitats for many animals, protection against coastal erosion, water purification, having the considerable capacity to store and sequester carbon, and are key players in the ecosystem natural remediation capacity (Couto et al, 2013; Teixeira et al, 2014; Duarte et al, 2018, 2021), being these services valuated in several millions of euros per year (Duarte et al, 2021). The Spartina genus is highly successful amongst the halophyte plant group, being widespread across the globe These plants have C4-type photosynthesis, in which a CO2 concentration mechanism at ribulose-1,5bisphosphate carboxylase-oxygenase (Rubisco) level, involving the fixation of atmospheric CO2 by phosphoenol-pyruvate carboxylase (PEPC), increases Rubisco carboxylase activity and allows a faster growth rate (von Caemmerer, 2020). (Gramineae) is a perennial grass distributed along a wide range of coastal habitats, aggressively competing with native species (Duarte et al, 2015). It was introduced in the Mediterranean Sea probably due to ship traffic from America, being used as packing material in ships boxes and crates (Hultén, 1958). Being present for some time along the Western Mediterranean coasts, it had not been recorded on the Eastern Iberian coast until recently (Baumel et al, 2016)
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