SAWMILLS, SULIFIDE, AND SPECIES SURVIVAL : Biodiversity Loss in Highly Altered Intertidal Habitats Marissa Jones; Advisor: Joel Elliott University of Puget Sound, Tacoma, Washington Research Questions Intertidal Diversity: To what extent do high levels of organic pollution affect the diversity of intertidal animals and algae? Do species differ in their apparent tolerance to hydrogen sulfide and anoxia? Transplant Experiment: Will the diversity of organisms living on rocks change when the rocks are transplanted to or from a site impacted by organic pollution? Sulfide and Oxygen Levels: What is the frequency and duration of stress from hydrogen sulfide and anoxia in impacted habitats? Selected References Frequency and Duration of Stress Abstract Organic pollution from historic lumber mills has been deposited into marine sediments in Puget Sound. Organic matter decomposes, releasing hydrogen sulfide that is oxidized by white mats of thiotrophic bacteria. These bacteria are a source of increased primary production in the intertidal zone, but sulfide is a potent toxin to most organisms. To investigate the effects of organic waste on intertidal organisms, former mill sites in Commencement Bay in Tacoma and Thatcher Bay on Blakely Is. were identified by the presence of white bacterial mats. The Shannon-Weiner Index (H’) was calculated for the top and bottom of 15 rocks at three impacted and two control sites. Diversity was significantly lower at the impacted sites, and particularly on the bottoms of the rocks. Diversity on rocks transplanted from clean to sulfide sites decreased over five weeks. Rocks transplanted from sulfide to clean experienced the opposite effect. The relative concentrations of sulfide and dissolved oxygen were measured during an incoming tide. The levels of sulfide decreased rapidly when exposed to oxygenated seawater. Rock from control area on Ruston Way. Rock from ASARCO site. The bottom is covered in filamentous, sulfide- oxidizing bacteria. Impacted Site Control site Sampling sites along Ruston Way on Commencement Bay in Tacoma, WA. Numerous mills operated along the shoreline. Areas affected by wood waste in the intertidal correspond with subtidal bacterial mats (Elliott et al. 2006). Thatcher Bay San Juan Islands Sampling site in Thatcher Bay on Blakely Island, WA. Thatcher Bay was the site of the largest lumber mill north of Seattle. Sulfide Oxygen Are the bacteria living on this crab collected from Commencement Bay helpful ectosymbionts, or just hitching a ride? Intertidal Diversity Survey Commencement Bay Tidal Height Side of Rock Lumber mills deposited tons of organic debris into marine sediments along Washington’s shoreline. Organic material decomposes, releasing extremely high levels of hydrogen sulfide, a potent toxin to most forms of eukaryotic life. In impacted areas, sulfide supports robust communities of thiotrophic bacteria growing at the oxic/anoxic interface. Transplant Experiment Acknowledgements University of Puget Sound Summer Research Grant, Phi Sigma Slater Award, Pierce Conservation District, Dr. Sandy Wyllie-Echeverria, University of Washington Friday Harbor Laboratories, Dr. Peter Wimberger, Al Vallecorsa. For Future Research… Five rocks were transplanted according to the treatments listed above and monitored for five weeks. As predicted, the diversity of organisms on the undersides of rocks transplanted from sulfide to control sites increased while the diversity on rocks transplanted from control to sulfide sites decreased (Repeated Measures ANOVA, p = 0.01). Top side of rocks Underside of rocks Commencement Bay Thatcher Bay Commencement Bay The Shannon Weiner Diversity Index (H’) was calculated for the top and bottom of 15 rocks at 8 sites, 2 in Thatcher Bay and 6 in Commencement Bay. Impacted sites were impoverished in species diversity compared to control sites. Some taxa appeared to be more tolerant to hydrogen sulfide than others. A concrete block containing sulfide and dissolved oxygen probes was constructed so that the probes measured the concentrations on the underside of the rock. Measurements were taken during an incoming tide. The concentration of hydrogen sulfide decreased dramatically when the rock came into contact with oxygenated seawater. For intertidal organisms living on the undersides of rocks, exposure to high levles of sulfide is periodic and linked to low tides. Determine the spatial extent of affected areas throughout Puget Sound and Georgia Basin. Explore the degree to which intertidal animals can exploit or tolerate hydrogen sulfide. Physiology Species interactions Investigate the role bacteria play in these unique, sulfide- rich habitats. If biodiversity is to be fully restored, the levels of organic pollution need to be addressed first. Wood Waste Bacteria