Trait gradients inform predictions of seagrass meadows changes to future warming

Abstract

Comparing populations across temperature gradients can inform how global warming will impact the structure and function of ecosystems. Shoot density, morphometry and productivity of the seagrass Posidonia oceanica to temperature variation was quantified at eight locations in Sardinia (western Mediterranean Sea) along a natural sea surface temperature (SST) gradient. The locations are spanned for a narrow range of latitude (1.5°), allowing the minimization of the effect of eventual photoperiod variability. Mean SST predicted P. oceanica meadow structure, with increased temperature correlated with higher shoot density, but lower leaf and rhizome width, and rhizome biomass. Chlorophyll a (Chl-a) strongly impacted seagrass traits independent of SST. Disentangling the effects of SST and Chl-a on seagrass meadow shoot density revealed that they work independently, but in the same direction with potential synergism. Space-for-time substitution predicts that global warming will trigger denser seagrass meadows with slender shoots, fewer leaves, and strongly impact seagrass ecosystem. Future investigations should evaluate if global warming will erode the ecosystem services provided by seagrass meadows.

Decline of seagrass (Posidonia oceanica) production over two decades in the face of warming of the Eastern Mediterranean Sea

“…High temperature reduces seagrass photosynthetic rates due to an alteration of the photosynthetic apparatus, mostly the heat‐stress‐sensitive PSII (Marín‐Guirao et al ., 2016). The resulting increase in respiration in relation to photosynthesis can lead to a negative carbon balance, impeding growth and production in different seagrass species (York et al ., 2013; Collier & Waycott, 2014) including P. oceanica (Olsen et al ., 2012; Hendriks et al ., 2017; Pansini et al ., 2021). Apart from the direct physiological stress that high temperatures pose to the meadows, the increase in temperature can indirectly affect seagrass meadow by altering other factors that are crucial for their well‐functioning, including salinity (Ruíz et al ., 2009; Borghini et al ., 2014), nutrient availability (Mvungi & Pillay, 2019), anaerobic mineralization (García et al ., 2012) and herbivore pressure (Buñuel et al ., 2021).…”

“…The iconic endemic seagrass of the Mediterranean Sea, Posidonia oceanica (L.) Delile, is particularly vulnerable to thermal stress, showing extensive damage (Ontoria et al ., 2019a; Pansini et al ., 2021; Stipcich et al ., 2022a) or even massive mortality (Díaz‐Almela et al ., 2009; Marbà & Duarte, 2010). The Mediterranean Sea is warming on average 20% faster than the global ocean (Lionello & Scarascia, 2018), with a cumulative increase in mean SST of 1.3°C over the last 40 yr (Pastor et al ., 2020), and an increase of 0.056°C yr −1 in maximum (i.e.…”

A research blueprint: Plant trait responses to stress and effects on blue carbon storage potential

“…Global increase in mean seawater and air temperature and the more frequent and lengthy heat wave events, are one of the most important drivers shaping coastal ecosystems worldwide. Temperature causes direct changes in biochemical composition, through changes in nutrient allocation or pigment composition, growth, morphology, primary productivity and phenology (Pansini et al, 2021). In particular, mangrove trees' distribution is limited by its sensitivity to cold temperatures, and therefore, the tropicalization of mid‐latitudes and higher mean winter temperatures in high latitudes may contribute to the colonization of new areas by this ecosystem.…”

Analysis and global research trends on nautical tourism and green coastal infrastructures: the case of coral reefs and seagrass meadows

“…In relation to this last aspect, this cluster also includes another group of research linked to the use as indicators for making projections on the effects of Global Change, the changes that are occurring in these marine green infrastructures, such as coral bleaching or the reduction in the surface area of certain seagrass meadows, such as posidonia oceanica [27,42,58,56].…”