Seasonal shifts in morphology, physiology and population traits in the seagrass Halodule wrightii (Cymodoceaceae) in a subtropical arid area

Abstract A seasonal field monitoring study was carried out to evaluate for the first time in Bahia Balandra (Southern Gulf of California) the changes in morphology, phenology and physiological traits in the seagrass Halodule wrightii. Seasonally, traits associated with morphology (leaf, sheath and rhizome), shoot density, biomass and physiology (non-structural carbohydrates, carbon and nitrogen contents) were measured between winter 2016 and spring 2017. Overall, all the traits varied across the seasons, with most of morphological characteristics, density and biomass peaking during autumn and showing the lowest values in winter-spring. Sexual reproduction was not observed, thus vegetative (asexual) propagation was the main strategy in this population. Both branching and shoot recruitment explained the increase in above- and belowground biomass in summer-autumn. The high starch concentrations found during winter, suggested that autumn is a suitable season for the growth of H. wrightii, investing a large fraction of their energy in producing biomass, but also in carbon storage (i.e. starch) in both tissues (above and belowground). This kind of study is needed in the protected area of Bahia Balandra in the Gulf of California and in general in Mexico, since H. wrightii has been recently categorized as a threatened species in Mexico and management actions demand current and accurate biological data for appropriate conservation actions.