Integrated Kelp - Oyster Aquaculture: Addressing Oyster Larvae Death in Acidic Ecosystems Affected by Coastal Upwelling and Ocean Acidification

Since the industrial revolution, anthropogenic CO2 has been steadily increasing the greenhouse gas effect warming earth’s atmosphere. About a third of all anthropomorphic CO2 finds its way into the ocean where it causes ocean acidification, which devastates shell forming organisms and coral reef ecosystems. Since the Industrial Revolution, the ocean’s average pH has dropped from 8.2 to 8.1, which constitutes a 30% increase in ocean water acidity. Ocean acidification has a particularly harsh impact on coastal ecosystems that experience seasonal upwelling, a process where colder, nutrient-rich, and acidic water rises up to the surface near coastlines. The combination of ocean acidification and upwelling serves to make these ecosystems incredibly acidic, damaging vulnerable shell-forming organisms like oysters. The oyster industry along the west coast of North America is struggling to cope with increased oyster larvae die offs due to these increasingly acidic conditions. Macroalgae photosynthesis has been shown to have a bufferingeffect in acidic ecosystems on a local scale in a process known as phytoremediation. Macroalgae phytoremediation could be utilized in integrated multi-trophic level aquaculture to mitigate the impacts of ocean acidification in coastal upwelling communities, improving the ecosystem and benefiting oyster growth rates and yield. By working with researchers in the Pacific Northwest, this report reviews current literature and assesses the feasibility of using macroalgea to rehabilitate acidic coastal ecosystems and quantitatively assesses the impact that macroalgea can have when grown with oysters. Tests were run with the Hood Head Kelp Farm model developed by System Science Applications Incorporated, and found that sugar kelp, Saccharina latissima, has a stabilizing effect on daily fluctuations of pH and Aragonite saturation when grown in coastal areas with a current speed of approximately .01 m/s.