Collections > Electronic Theses and Dissertations > Consumers Mitigate Effects of Heat Stress and Nutrient Enrichment on Eelgrass (Zostera Marina L.) Communities at its Southern Range Limit
pdf

At the southern end of its range, eelgrass (<italic>Zostera marina</italic>) meadows in North Carolina are vulnerable to stressors including eutrophication, which promotes overgrowth of algal epiphytes, and heat stress that causes summer die-offs. I conducted a mesocosm experiment investigating the interactive effects of heat stress (+1.5°C) and nutrient loading (+10µM NH<sub>4NO</sub>3/1µM KH<sub>2PO</sub>4) on an amphipod-eelgrass system. Additionally, I manipulated consumer pressure from an abundant omnivorous fish (<italic>Lagodon rhomboides</italic>) to understand how top-down pressure interacted with bottom-up stressors. Nutrient enrichment only increased epibiont load when combined with warming, and had no effects on aboveground biomass. Pinfish consumed nearly all amphipods, which had no effect on epibiont load, but prevented macroalgal accumulation and mitigated eelgrass loss due to heat stress. Omnivorous consumers can play an important role in preventing macroalgal accumulation from exacerbating heat stress effects, although continued warming may nevertheless cause significant regional habitat loss as eelgrass reaches extreme physiological limits.