Our research set out to investigate the impact of hydrogen sulfide on eelgrass seedlings through a series of lab and field studies. In the lab, we exposed seedlings to various concentrations of hydrogen sulfide to determine how it impacted health, and the concentration required to kill 50% of the test samples (LD
50). To acquire test specimens, flowering shoots were harvested from False Bay (San Juan Island, WA) and seeds were extracted, then germinated in sterile conditions at the Biology Department of UW. Health was measured by the individuals’ ability to photosynthesize, indicated by their irradiance spectrum.
Laboratory trials demonstrated that minuscule doses of hydrogen sulfide actually increased photosynthesis and leaf health, but that higher concentrations shut down photosystem II, inhibiting photosynthesis. Even relatively low concentrations of H
2S (400-500 μM) appeared to significantly increase seedling mortality. While it was possible for seedlings to recover after short-term exposure to high concentrations, it was determined that the LD
50 boundary after 48 hours of H
2S exposure was 483
μM, and after one week the boundary level was 334
μM (Figure 2).