LAKE MERRITT UNDERWATER - VIEWS BEFORE AND AFTER ENVIRONMENTAL CATASTROPHES OF 2022-2023

Lake Merritt, a tidal estuary in highly urbanized Oakland California, has suffered from poor water quality and trash pollution since colonial times. Recently, the threat of harmful algal blooms and extreme weather related to climate change has introduced new challenges. Programs to engage the public in both the science and the conservation measures needed to address the underlying problems remain limited. In 2018 we established an informal environmental education program called the Lake Merritt Underwater Observatory (LMUO) to connect people who visit Lakeside Park at Lake Merritt to the living communities normally out of view. We acquired a Trident ROV (remotely operated vehicle) that recorded underwater video footage and could be operated by students and casual visitors. We were able to continue our program safely through the pandemic. We acquired videos of underwater life nearshore and in deep water in different parts of the lake in different seasons. Here we focus on videos collected before and after two environmental catastrophes: August 2022, the harmful phytoplankton species Heterosigma akashiwo entered the estuary from San Francisco Bay causing a 5-day anoxic condition at both top and bottom of the water column. An unprecedented fish kill seen on the shoreline was national news and spurred city action and new management plans. In January 2023, a series of atmospheric rivers hit Oakland causing rapid freshening of the almost marine lake and flooding of shore habitats. We involved community college, K-8 classes and groups and adults visiting the lake for recreation in viewing the devastation of invertebrate and plant communities immediately following both events and the uneven return of species in the year that followed. We hope the experience will inspire youth to pursue environmental and technology careers in the future.