Protecting and Restoring the Morro Bay Estuary.

EELGRASS HABITAT REBOUNDING IN MORRO BAY ESTUARY

EELGRASS HABITAT REBOUNDING IN MORRO BAY ESTUARY

Eelgrass monitoring_landscape_with person_Morro Bay National Estuary Program

 

 

146 acres of eelgrass and growing!

We are excited to announce that eelgrass habitat in Morro Bay has expanded dramatically. In 2017, there were only thirteen acres of eelgrass left in the bay. However, our most-recent map, created with aerial images taken in 2020, shows 146 acres of eelgrass habitat. If you have been out on the water lately or taken a bayside walk, you’ve likely seen the increased amount of eelgrass wrack along the shoreline of the estuary. This is because many areas where eelgrass had died off previously now support healthy eelgrass meadows.

Eelgrass habitat recovery in pictures

The three images below show the progression of eelgrass coverage at a single monitoring site, from the drastic die back to the recent signs of recovery.

2010 photo of eelgrass in the bay_morro bay national estuary program

Eelgrass coverage at a long-term monitoring site in 2010.

Lack of eelgrass shown at a long-term monitoring site in 2015 after eelgrass loss. Morro Bay national Estuary Program

This is the same long-term monitoring site in 2015 after the drastic eelgrass decline.

2021 view of eelgrass from long-term monitoring site with abundant eelgrass and monitoring measurement tool.

Here, you can see the recent eelgrass expansion at the same site in 2021.

Where has eelgrass habitat grown back?

Eelgrass habitat extent from 2007 to 2020, showing eelgrass decline and recent partial recovery.

Eelgrass habitat extent from 2007 to 2020, showing eelgrass decline and recent partial recovery.

During the recent decline, eelgrass towards the bay mouth remained relatively stable. Most of the eelgrass lost was in the mid and back bay. In 2016 and 2017, we observed small patches of individual eelgrass plants returning to these areas, but much of the estuary remained mudflat where eelgrass had previously grown. Areas adjacent to the main tidal channel) have filled in the fastest, with smaller patches expanding into sizable continuous eelgrass beds. Currently, eelgrass is present almost continuously from Morro Bay State Park Marina to Pasadena Point along the main tidal channel.

This map shows 43 acres of eelgrass habitat in 2019 and the expansion of eelgrass to 146 acres in 2020.

This map shows 43 acres of eelgrass habitat in 2019 and the expansion of eelgrass to 146 acres in 2020.

To learn more about how the eelgrass coverage is calculated using high-resolution images of the bay, check out our Field Updates November 2021: Eelgrass Monitoring Behind the Scenes blog.

Eelgrass expands naturally and with human assistance

Eelgrass can expand naturally through a horizontal root system referred to as rhizomes. It can also release seeds that spread with the tides. To aid the natural expansion of eelgrass, the Estuary Program has worked with project partners and funding support over the last five years to harvest eelgrass from healthy donor beds and transplant it in areas where eelgrass had died back. These partners and funders include private individuals, United States Fish and Wildlife Service, Pacific Marine Estuarine Fish Habitat Partnership, United States Environmental Protection Agency, California Department of Fish and Wildlife, Black Brant Group, and others.

Eelgrass root structure with shoots growing up from the rhizomes. Both natural and restored plots can expand horizontally. Some restoration plots have at least doubled in size over one year.

Eelgrass root structure with shoots growing up from the rhizomes. Both natural and restored plots can expand horizontally. Some restoration plots have at least doubled in size over one year.

Both restored eelgrass beds and natural beds produce eelgrass seeds.

Both restored eelgrass beds and natural beds produce eelgrass seeds.

These seeds disperse and create new eelgrass plants, adding to the genetic diversity of the eelgrass population in the bay.

These seeds disperse and create new eelgrass plants, adding to the genetic diversity of the eelgrass population in the bay.

In 2018, we planted six eelgrass restoration plots in the area shown in the picture below. Those original six plantings expanded into two large beds (shown on the left and right of the foreground) over the following two years. In left bed, we originally planted three rebar pieces with about 25 eelgrass rhizomes tied to each one. In the bed on the right, we planted three one-meter-squared plots. You can see one of the original plots marked by a square transect inside the oval.

Six small restoration plots have grown into the two large eelgrass beds shown in this picture. A square transect marks one of the original one-meter-squared plots in the bed on the right.

You can find further information on eelgrass restoration efforts in prior blogs here and you can read about the factors that affect eelgrass health here. We will continue to report on eelgrass health and restoration efforts in the future.

What’s next?

At the most recent peak of eelgrass coverage in 2007, there were 344 acres of eelgrass habitat in Morro Bay. This historic acreage gives us an idea of how much eelgrass the bay is able to support. Considering this number and the recent mapping of suitable elevations for eelgrass habitat, we have set 313 acres as our bay-wide eelgrass goal.

We plan to continue restoration efforts this spring. We will also continue mapping eelgrass acreage. The Estuary Program partnered with Cal Poly researchers in early December 2021 to collect high-resolution images of the bay to track eelgrass acreage changes since 2020. We now begin the lengthy work of field checks and computer analysis to create the 2021 eelgrass habitat map and assess how things have changed over the year. We will share an updated map and acreage amount next year.

These valuable efforts to monitor, map, restore, and conduct research on eelgrass would not have been possible without the support of numerous Estuary Program partners, including Tenera Environmental, Inc., Cal Poly, and Cuesta College.


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