Format: ORAL

Dustin Wolkis1, 2, Seana Walsh1, 2, Raffaela Abbriano1, 2, Kasey Barton3

1 Department of Science and Conservation, National Tropical Botanical Garden, Kalaheo, HI, USA. 2 Natural History Museum of Denmark, University of Copenhagen, Copenhagen, Denmark. 3 School of Life Sciences, University of Hawai‘i at Manoa, Honolulu, HI, USA.

Many coastal plant species have adaptations that enable them to exist in higher saline conditions. However, rising sea levels, increased frequency and intensity of storm surges, and increased drought due to climate change are anticipated to increase the level of salinity to which coastal plants are exposed. Although some species may be able to tolerate these changes, salinity tolerance is highly variable across species and ontogenetic stage. Coastal ecosystems are critical for the welfare Hawai?is residents, providing sustenance, stabilizing shorelines, and promoting economic and cultural well-being. Understanding how increased salinity will affect Hawaiian coastal plants is important to effectively manage and conserve these critical ecosystems. To improve our understanding of coastal plant species tolerance to projected increases in salinity exposure at the early ontogenetic stage of seed germination, we tested the effect of salinity (0, 10, 20, and 35 ppt total salinity of unfiltered/untreated seawater), then tested for resilience by rinsing seeds and sowing with freshwater. We included 17 native and 3 non-native species in our study. Although salinity tolerance varied considerably among species, salinity exposure generally reduced and delayed germination. The greatest effects were detected at higher salinity levels. Recovery germination overall was higher for seeds that had been exposed to higher salinity. None of the factors we explored emerged as predictors of salinity tolerance except seed mass, which tended to enhance germination at higher salinity. Species responses to salinity exposure indicate high vulnerability of coastal systems to increased salinity stress, and variability among species could lead to shifts in community assembly and composition under sea level rise. These results can help guide coastal ecosystem conservation and restoration management decisions in the face of climate change.