Interactive effects of temperature and nutrients on mangrove seedling growth and implications for establishment

The establishment and wellbeing of seedlings governs the spread and survival of mangrove forests. Eutrophication and global warming are major challenges endangering mangrove ecosystem integrity. How these stressors affect seedling growth is not well understood. In a mesocosm experiment we grew mangrove seedlings in temperature-controlled chambers and investigated single and combined effects of temperature (23 and 33 °C), organic matter and dissolved nutrients on seedling trait morphology. Seedling survival was lowest in organic matter treatments. Combined effects of temperature and nutrients caused significant differences in root morphology with fewer but longer and thicker 3rd order roots, fewer 2nd and no 1st order roots in nutrient-enriched (23 °C) compared to non-enriched treatments (33 °C). Our results indicate these seedlings are less resilient to withstand their dynamic environment, in which they must settle and establish, due to lower root complexity. Mangrove ecosystems are negatively affected by global and local stresses; if new seedlings, which support forest recovery, are also affected then this amplifies stresses.