Effects of Ocean Acidification and Warming on Salish Sea Kelps: a Meta-analysis

• Main Author: Roethler, Miranda
• Format: Text
• Language: English
• Published: Western CEDAR 2022
• Subjects: Ocean acidification
• Online Access: https://cedar.wwu.edu/ssec/2022ssec/allsessions/245; https://cedar.wwu.edu/context/ssec/article/3407/viewcontent/1030_Roethler_EffectsofOceanAcidificationandWarmingonSalishSeaKelpsaMetaanalysis.pdf

Kelp (order Laminariales) is highly abundant and diverse in the Salish Sea, and serves a variety of functions, from ecosystem engineering, to providing food for herbivores and detritivores, to mariculture. To date, little research has been conducted in the Salish Sea on the effects of climate change (specifically ocean acidification and warming) on local kelp species. Decline in bull kelp (Nereocystis luetkeana) in some areas of Puget Sound (Washington, USA) has generated concern amongst local stakeholders about the long-term health of Salish Sea kelp forests. Additionally, for local mariculture ventures it is important to understand how specific species of kelp will perform in future oceans. We conducted a meta-analysis to determine the effect of climate change on kelps, by compiling a global dataset of peer-reviewed experimental studies on kelp and warming or acidification. For the analysis, we focus on species found in the Salish Sea, and compare their response to global trends. We determine which life stages and endpoint metrics (e.g., survival, growth, reproduction) are most vulnerable to climate change stressors and highlight knowledge gaps where more research needs to be done. In general, the direction and magnitude of kelp response to stress was life stage specific. Adult sporophytes were negatively impacted by warming but positively impacted by acidification, while gametophytes were not affected by warming but were negatively affected by acidification. For all life stages, endpoint metrics such as survival, growth, and reproduction/development were the most heavily impacted by single and multiple stressors. The four studies conducted in the Salish Sea on adult sporophytes show a positive effect of acidification and no significant effect of warming. More kelp studies need to be conducted in the Salish Sea region, specifically on gametophytes and incorporating multiple stressors.