Copper sulphate treatment induces Heterozostera seed germination and improves seedling growth rates

Evidence for seed germination and/or seedling recruitment in wild populations of the Southern Hemisphere seagrass H. nigricaulis are lacking. Additionally, seeds of H. nigricaulis, have proven extremely difficult to store and germinate in laboratories, even when using techniques for germination proven successful in other Zosteraceae. Prior studies reveal Zosteraceae seed and seedling failure may be correlated with oomycete infections. Copper sulphate treatments can reduce oomycete and other seagrass infections in laboratory tests. Here, we tested whether copper sulphate seed treatments promote germination and seedling growth in H. nigricaulis. We found treatment with 2.0 ppm copper sulphate solution induced significant seed germination and led to 3 times more photosynthesizing H. nigricaulis seedlings after 3 months. Thus, in addition to reducing disease, copper sulphate appears to be a novel cue for H. nigricaulis germination and improves seedling development and success in H. nigricaulis. This discovery will improve our opportunities to overcome biogeochemical germination cues and bottlenecks for Zosteraceae and improve seed-based seagrass restoration strategies where copper sulphate treatment is available to pre-treat and cue germination and promote seedling development and growth.