Abstract
The increase in extreme heat events associated to global warming threatens seagrass ecosystems, likely by affecting key plant physiological processes such as photosynthesis and respiration. Understanding species’ ability to acclimate to warming is crucial to better predict their future trends. Here, we study tolerance to warming in two key Mediterranean seagrasses, Posidonia oceanica and Cymodocea nodosa. Stress responses of shallow and deep plants were followed during and after short-term heat exposure in mesocosms by coupling photo-physiological measures with analysis of expression of photosynthesis and stress-related genes. Contrasting tolerance and capacity to heat acclimation were shown by shallow and deep P. oceanica ecotypes. While shallow plants acclimated through respiratory homeostasis and activation of photo-protective mechanisms, deep ones experienced photosynthetic injury and impaired carbon balance. This suggests that P. oceanica ecotypes are thermally adapted to local conditions and that Mediterranean warming will likely diversely affect deep and shallow meadow stands. On the other hand, contrasting mechanisms of heat-acclimation were adopted by the two species. P. oceanica regulates photosynthesis and respiration at the level of control plants while C. nodosa balances both processes at enhanced rates. These acclimation discrepancies are discussed in relation to inherent attributes of the two species.
Highlights
Z. marina best hit ZosmaCg00300 ZosmaCg00300 ZosmaCg00540 ZosmaCg00550 ZosmaCg00390 Zosma196g00110 Zosma196g00110 Zosma88g00030 ZosmaCg00710 ZosmaCg00710 Zosma15g00370 Zosma15g00370 Zosma118g00060 Zosma82g00590 Zosma82g00590 Zosma8g01500
The assessment of the response to warming of shallow and deep P. oceanica ecotypes is a priority to improve our ability to predict their future trends in the framework of global climate change and to establish adequate management and conservation policies
The F0 increase, that is considered a very suitable test to assess the state of the photosynthetic machinery in terrestrial plants under heat stress[30], confirmed that deep plants were experiencing critical temperature levels that lead to photosystem II (PSII) inactivation[31]
Summary
Z. marina best hit ZosmaCg00300 ZosmaCg00300 ZosmaCg00540 ZosmaCg00550 ZosmaCg00390 Zosma196g00110 Zosma196g00110 Zosma88g00030 ZosmaCg00710 ZosmaCg00710 Zosma15g00370 Zosma15g00370 Zosma118g00060 Zosma82g00590 Zosma82g00590 Zosma8g01500. Inter- and intra-specific differences in heat tolerance of seagrasses is not surprising, considering that this group of plants comprises species with quite different ecological strategies and biological attributes[19], and that individuals and populations of the same species are distributed, and likely thermally adapted, along ample clines (i.e. latitudinal and bathymetrical gradients). Meadows are distributed along a wide bathymetrical cline, with individuals within a single population living above and below the summer thermocline and experiencing distinct thermal regimens This might have induced an adaptive differentiation through phenotypic plasticity and/or local adaptation, giving rise to shallow and deep ecotypes with distinct tolerance and acclimatization capacity to warming[27]. The assessment of the response to warming of shallow and deep P. oceanica ecotypes is a priority to improve our ability to predict their future trends in the framework of global climate change and to establish adequate management and conservation policies
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