Abstract
Climate change fuels invasions of plant species and displacement of local plants. Little is known about the ecophysiological adaptation of the invasive species, and their ability to cope with the changing conditions in their new habitat. Halophila stipulacea, a tropical seagrass native to the Gulf of Aqaba (GoA; northern Red Sea), became a Lessepsian migrant spreading within the eastern Mediterranean where it could potentially outcompete local species. We analyzed temperature records in the last 35 years and show that water temperature has increased faster in the eastern Mediterranean Sea compared to GoA, suggesting that H. stipulacea’s invasive success is associated with adaptation to thermal warming. Furthermore, we compared the responses of native (Eilat, Israel) and invasive (Limassol, Cyprus) H. stipulacea plants to current (26oC) and predicted thermal maxima (29℃ and 32℃) in a controlled experimental microcosm. Morphological and photo-physiological results showed negative effects of heat stress on the native plants while un-affected/ or even enhanced performance in their invasive counterparts. Gene expression, studied for the 1st time in H. stipulacea, pointed to differences in the molecular responses of two populations to thermal stress. Results predict that sea warming will cause vast reductions in H. stipulacea meadows growing in the GoA while sea warming will facilitate H. stipulacea’s spread within the Mediterranean Sea.
Highlights
Seagrass meadows thrive worldwide in shallow sedimentary shorelines, where they fulfill important ecological services estimated at US$ 2.8 × 106 km−2 yr−1 (Costanza et al, 2014)
Comparisons between the long-term environmental conditions at the two sites that were based the Bio-ORACLE global dataset (Supplementary materials S1) demonstrated that salinity was very similar between the sites, with an annual average of 39.2 and 38.8 [Practical Salinity Scale (PSS)] for Cyprus and Gulf of Aqaba (GoA) sites, respectively
Detrended sea surface temperatures (SSTs) regression analysis continued to show that both sites have been warming significantly, this data shows that warming has been faster in Cyprus (0.36 ± 0.06◦C SE /decade, p < 0.05) compared with the northern GoA)0.26 ± 0.06◦C SE /decade, p < 0.05) (Figures 3E,F)
Summary
Seagrass meadows thrive worldwide in shallow sedimentary shorelines, where they fulfill important ecological services (including high primary productivity, production, and burial of organic carbon, nutrient cycling, and sediment stabilization) estimated at US$ 2.8 × 106 km−2 yr−1 (Costanza et al, 2014). Seagrass ecosystems are facing a global crisis due to both direct (reduced water quality, coastal development, and poor land use) and indirect (climate change) anthropogenic perturbations (Orth et al, 2006; Waycott et al, 2009; Short et al, 2011). Halophila stipulacea Under Climate Change entails devastation of the associated biodiversity and primary productivity, reduction of local fishing grounds, enhancement of coastal erosion, and loss of major carbon sinks culminating in ecological and socio-economic dislocations (Wyllie-Echeverria and Cox, 1999; Orth et al, 2006; Fourqurean et al, 2012; Costanza et al, 2014; Arias-Ortiz et al, 2018). Within the northern Gulf of Aqaba (GoA), one of the focal regions of this study, H. stipulacea is the most dominant, and sometimes only seagrass species (El Shaffai, 2011; Mejia et al, 2016), forming extensive mono-specific meadows found in both shallow and deep environments (1–50 m depth; Sharon et al, 2011; Winters et al, 2017), in soft sediments ranging from fine sand to gravel (Mejia et al, 2016; Rotini et al, 2017)
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