UC Irvine

Climate change and expanding human populations are converging threats that impact marine ecosystems, leading to global declines in critical habitat and biodiversity. Targeted and innovative management solutions that can reconcile the objectives of supporting human livelihoods alongside those of environmental sustainability are urgently needed. My research highlights important management considerations for the conservation and restoration of two foundation marine ecosystems that dominate global temperate coastal regions, seagrass meadows and canopy-forming kelp forests. Urban greening offers a strategic opportunity to reinforce the security and safety of food from the sea. Seagrass ecosystems can reduce human bacterial pathogens from terrestrial sources, however it remains unknown whether this health benefit is conferred to associated food fish. Marine bivalves are bioindicators of bacterial contamination and constitute over half of global seafood production. Following a three month deployment across 20 coastal urban locations in the greater Seattle Metropolitan Area, I found in Chapter 1 that bivalves deployed and subsequently retrieved from locations with seagrass present had a 65% reduction in the abundance of bacterial species with known human pathogenicity when compared to locations without seagrass. My global models estimate that 1.1 billion people currently reside in over one-third (662 of 1,860) of urban agglomerations (populations over 300,000 people) and 19 megacities (populations over 10 million people) within 50 km of seagrass ecosystems, which I forecast to rise 15% by 2030. Given increasing reliance on food from the sea to meet supply and nutritional needs, these results highlight the global opportunity to support ambitious human health and biodiversity sustainability targets. Canopy-forming kelps are foundation species that support biodiversity and provide ecosystem services valued at over USD$500 billion per year. Giant kelp forests are facing unprecedented loss due to climate-driven ecological stressors necessitating innovative restoration strategies. I produced a video for Chapter 2 to illustrate a protocol and tools for restoring canopy-forming giant kelp forests. I include field-based tissue collection and laboratory-based methods of sporulating, inoculating, rearing, maintaining, and monitoring substrates seeded with early life stages using the ‘green gravel’ technique. The protocol simplifies and centralizes existing practices in this field of restoration to facilitate conservation objectives for underwater kelp forests by researchers, managers and stakeholders. Climate change and anthropogenic disturbances are currently outpacing the adaptive capacity of natural kelp populations, challenging traditional conservation aims of restoration to historic states. Thus, conservation frameworks have expanded to include anticipatory management that proactively consider resilience and adaptive capacity. I conducted a >2-month long-term trial in Chapter 3 to assess the effect of rearing temperatures (12°C, 16°C, 20°C, and 24°C) on early microstages of a canopy-forming giant kelp species from potentially locally adapted Santa Cruz and San Diego populations of origin in constant thermal conditions, followed by a simulated deployment for restoration at 16°C and a realistic marine heatwave of 22°C. Samples reared in cooler 12 and 16°C temperatures performed best in constant thermal conditions. However, these samples were significantly impacted by a simulated heatwave. Despite poor performance in constant thermal conditions, samples reared at 20°C were able to recover from reproductive dormancy given a simulated deployment for restoration at 16°C, and performed best after a 22°C simulated heatwave. There was no kelp survival in the 24°C rearing temperature, and thus this treatment was terminated. These findings suggest that rearing M. pyrifera at warmer temperatures may confer an advantage when deployed into warming oceans with increasing frequency and magnitude of marine heatwaves, and provides an avenue forward for marine managers looking to future-proof restoration efforts. Critical marine habitats such as seagrass and kelp ecosystems continue to deteriorate at unprecedented rates, calling upon management solutions that pro-actively and simultaneously consider human populations and future environmental decisions.