Does Morro Bay support healthy eelgrass beds?

Eelgrass Status in the Morro Bay Estuary

Eelgrass is a flowering plant that puts down roots in Morro Bay, where it serves many functions. Its overlapping roots help stabilize the bay floor and keep the waters clear. It puts oxygen into the water to support other wildlife. And its floating blades form an underwater meadow that provide shelter and a place to find food for the bay’s aquatic life.

The Estuary Program has mapped eelgrass and monitored bed health around the bay since the early 2000s.

A baywide map created in 2007 indicated 344 acres of eelgrass. Over the next five years, eelgrass acreage dwindled, with large stable beds all but disappearing from the mid and back bay areas. Our 2017 mapping effort indicated 13 acres of intertidal eelgrass. In the past two years, monitoring efforts showed patches of eelgrass in areas where it has not been present for several years. Although these new plants are not enough to increase the overall acreage significantly, they could indicate positive trends for eelgrass in the future.

Eelgrass Acreage: 2007 and 2017

Eelgrass acreage (represented in yellow) has declined since 2007 when 344 acres were mapped. While beds toward the front bay and along the main channel have remained relatively stable, nearly all eelgrass was lost in the mid and back bay. Eelgrass loss has since stabilized, and the 2017 map shows small patches of eelgrass recurring in areas that suffered almost total loss.

Restoration Success

The Estuary Program has worked with partners including Cal Poly San Luis Obispo (Cal Poly), California Sea Grant, and countless volunteers to conduct experimental eelgrass restoration in the bay. Plants are harvested from the healthy beds toward the front of the bay, and then transplanted in the mid and back bay where eelgrass loss has been the most severe. This small-scale experimental restoration allows us to test out the timing, method, and locations for transplanting. We are learning a great deal from this work, and the success we’ve seen as a result supports expanding our restoration efforts in the future.

The Estuary Program conducted three years of small scale experimental eelgrass transplanting to learn more about the optimal methods, locations, and timing for restoration. These efforts have tested plantings at different times of the year, with different anchoring methods, a range of sites and depths, and multiple donor bed locations.

Staff and volunteers venture out onto eelgrass beds on foot and collect eelgrass shoots and a portion of roots by hand at low tides. In 2017, 17 plots were planted with garden stakes, with a higher survival occurring in spring planting than the summer planting. In 2018, 22 plots were planted with garden stakes and 9 rebar pieces. Plantings also occurred at a larger range of locations and depths. Plot and rebar plantings in 2018 were successful, with all plots growing well at about 9 months.

Staff and volunteers carefully transplanted 72 harvested eelgrass shoots into each one-meter by one-meter plot, anchoring them in place using u-shaped garden stakes.

Next steps include expanding existing beds along the main channel, planting at subtidal locations (scuba), and planting further from the main channel (snorkel).

This photo shows the transplanted plots two years later. The white PVC quadrat illustrates the original one-meter by one-meter plot that was transplanted. The bed has greatly expanded over the two years.

Cal Poly Research Efforts

To help understand the reasons for the eelgrass decline, Cal Poly and the Estuary Program, with support from California Sea Grant, are conducting a multi-year study of water circulation in the bay and how it may have changed over time. Changing conditions such as shallower, more turbid waters, for example, could be having negative impacts on eelgrass. The results of this research, expected in 2020, will help guide our future restoration efforts and other projects that could potentially tip the balance in favor of eelgrass. The photos on this page show members of the Cal Poly project team at work, including undergraduate students Sydney Wewerka and Edwin Rainville, Senior Research Scientist Ian Robbins, and Physics Professor Ryan Walter.

In this picture, Sydney Wewerka (left) and Professor Walter (right), lower a sampler into the bay to gather sediment from the bay bottom. Samples are sent to a lab to conduct grain size analysis. Photograph courtesy of Ryan Walter.

Sydney Wewerka, Professor Walter, and Ian Robbins (pictured left to right) collect sediment samples to determine how much silt, clay, and sand are present in different regions of the bay. See page 9 for results. Photograph courtesy of Ryan Walter.

Cal Poly researchers lower an array of water quality sensors into the bay where they will continuously gather data for one month. The measurements include temperature, water velocity, and salinity. Photograph courtesy of Ryan Walter.

Edwin Rainville helps install sensors in the middle of the bay near Windy Point. Along with sensors near the Coast Guard station and the oyster farms, the data helps track water quality conditions throughout the bay. Photograph courtesy of Ryan Walter.

Cuesta College Research Efforts

Cuesta College, with support from the Estuary Program, embarked on a research effort to study Labyrinthula spp., which is the slime mold that can lead to wasting disease. At other estuaries around the country, wasting disease has been responsible for widespread eelgrass declines. Cuesta professors Laurie McConnico and Silvio Favoreto wanted to better understand the prevalence of this disease and how it impacts eelgrass.

The Estuary Program awarded funding to the two professors to purchase reagents and equipment and to pay the course registration fees for students volunteering in the lab. The project involved the Cuesta faculty and students collecting eelgrass blades with and without signs of necrosis (dark areas on the blades) throughout Morro Bay and using this material for the isolation of strains of Labyrinthula spp., resulting in 18 isolates cryopreserved in liquid nitrogen. During the summer of 2018, they collected eelgrass from four sites (Coleman Park, Windy Cove, Mid Bay, and Back Bay) and in summer 2019 they collected from three sites (Coleman Park, Windy Cove, and Back Bay). The blades were used to quantify necrotic tissue and an Excess Green Index was created, to represent the health of the eelgrass based on its color. All samples were collected and initially processed by students participating in a summer environmental microbiology course. Preliminary data analysis indicates Labyrinthula spp. is found at all sample locations within the estuary, and in both green and necrotic eelgrass tissue.

The researchers’ efforts will include sampling in 2020.

Students collected healthy (green colored) and unhealthy eelgrass (brown colored) blades from locations throughout the bay. The blades were laid out on a white board to more easily detect their color.

The students put sections of eelgrass glades onto agar plates. If it was present, the slime mold would grow and be detectable on the plate.

Hard at work in the lab! Photos courtesy of Cuesta College.

Video Presentation: How Healthy is Morro Bay's Eelgrass?

See how eelgrass in Morro Bay is doing today and learn what the Morro Bay National Estuary Program, researchers at California Polytechnic University San Luis Obispo, and other partners are doing to help bring back this essential aquatic grass.

Data Notes

The eelgrass maps from 2007 and 2017 were created using multi-spectral imagery collected in the fall by Ocean Imaging, Inc. The eelgrass map was created using an automated classification scheme and was groundtruthed by Estuary Program staff.