Jul 14, 2023

June 2023 Field Updates: Current Monitoring Efforts

The Estuary Program conducts routine monitoring to help track the health of the estuary and the creeks that drain into it. In June, our team piloted a new toxicity monitoring effort and continued our seasonal eelgrass health assessment. These efforts guide our conservation and restoration efforts and inform management. 

Toxic Contamination

Toxic pollutants pose a threat to ecosystems by altering water and soil chemistry. These changes can affect the behavior and reproduction patterns of aquatic species and, in severe cases, may even cause mortality. Toxic contaminants can accumulate in sediment and be released slowly over time, thus acting as a long-term pollution source to our waterways. Potential sources of toxic contamination include storm runoff, untreated wastewater, and hazardous materials spills. 

To better understand the extent of toxic contamination in the Morro Bay watershed, the Estuary Program is undertaking a new monitoring effort where staff collect water and sediment samples and send them off to a laboratory for toxicity testing. The resulting data helps us identify polluted areas and better understand the direct impacts to aquatic life from the water and sediment present in our creeks. 

This spring staff collected water and sediment samples from three sites in the watershed for toxicity analysis.

Testing for Toxicity 

In June, staff collected water and sediment samples from two sites in the Chorro Creek subwatershed and one site in the Los Osos Creek subwatershed. After collection, the samples were hand-delivered to personnel from the UC Davis Granite Canyon Lab.  

To assess toxicity, the lab uses indicator species like algae and insects that are known to be sensitive to pollution. The lab puts these organisms in the water and sediment collected from our creeks. The lab then tracks the survival and growth of the organisms. If the organisms can survive and thrive over the study period, there is likely no toxic material present in the sample.  

Researchers at UC Davis assess toxicity in their laboratory using small organisms with a known sensitivity to pollution. Photo courtesy of UC Davis Granite Canyon Laboratory.

Monitoring Eelgrass Health 

Eelgrass (Zostera marina) is a flowering seagrass that grows in the Morro Bay estuary. Eelgrass is important for bay health, as it serves as a source of food and habitat for a diverse range of species. It also helps to improve water quality by stabilizing sediment and producing oxygen. To read more about the status of eelgrass in the estuary, please click here. 

The Estuary Program monitors eelgrass condition several times throughout the year, including once each spring.

The Estuary Program monitors eelgrass health in several different ways. During the spring, our staff take an in-depth look at the condition of our eelgrass beds. We collect data like the length of the eelgrass blades, the presence of algae covering the blades, and the appearance of dark patches that could indicate diseased tissue.  

The results of our monitoring have shown that there is diseased or decaying tissue present in eelgrass beds throughout the estuary. The amount of decay varies by location. This disease takes advantage of stressed or weakened blades and decomposes the surrounding tissue. This decomposition creates characteristic dark spots along the otherwise green and healthy-looking plant. Despite the presence of diseased tissue, the survival of the eelgrass plant is not necessarily impaired as long as adequate green blades are left to support photosynthesis. 

A photo of an eelgrass plant with dark areas circled in red. The zoomed-in portion of the blade offers a closer look at the diseased tissue.

A large component of our spring eelgrass monitoring involves analyzing photos of eelgrass blades that are taken in the field. If you’re interested in how the photo processing works, check out last year’s blog post discussing this project. 

Help us protect and restore the Morro Bay estuary! 


Thank you for helping our beautiful, bountiful, biodiverse bay!