Effects of soil saturation and salinity on seed germination in seven freshwater marsh species from the tropical coast of the Gulf of Mexico

Abstract

The Gulf of Mexico will be strongly impacted by climate change. Most climate change scenarios predict increases in sea level, which will affect coastal wetland systems. Our aim is to understand how salinity and flooding affect germination in tropical freshwater marsh species. The germination of seven species occurring in coastal freshwater marshes in central Veracruz on the Gulf of Mexico was evaluated. The purpose of this study was to determine in the laboratory the rate and percentage of seed germination at different levels of salinity and flooding for the species: Typha domingensis, Sagittaria lancifolia, Ludwigia octovalvis, Pontederia sagittata, Boehmeria cylindrica, Cyperus digitatus and Fuirena simplex. Germination tests were conducted in Petri dishes. The treatment consisted of two factors: saturation and salinity. The first factor presented two levels (moist and saturated), and the second factor four levels (freshwater, 5, 10 and 15 ppt). The controlled conditions in the germination chamber were light for 14h at 25°C and dark for 10h at 20°C. The results showed that the species germinated faster and had higher germination percentages in the freshwater treatment compared to the more saline conditions. The three most salt-tolerant species were T. domingensis, L. octovalvis and C. digitatus. Additionally, germination was higher under saturated conditions for all species except for B. cylindrica. Based on our results, we conclude that changes in hydroperiod, but mainly an increase in saline conditions, can significantly affect the germination process of coastal freshwater marsh species under wetland salt intrusion.