Massive seagrass die-off leads to widespread erosion in a California estuary

July 27, 2020

The large-scale loss of eelgrass in a major California estuary -- Morro Bay -- may be causing widespread erosion, according to a new study from California Polytechnic State University.

In recent years, Morro Bay's iconic eelgrass beds, which provide the estuary's primary living habitat, experienced a massive die-off, declining more than 90 percent since 2007. Efforts to restore the eelgrass have had mixed success in many parts of the bay, and this seagrass is now only found close to the mouth of the bay and sporadically in other regions.

Seagrass systems are found throughout the world and provide many ecosystem services including fish nursery habitats, forage for migratory birds, nutrient cycling, carbon storage and sediment stabilization.

"The loss of eelgrass in the Morro Bay estuary is analogous to the loss of trees in a rainforest," says lead author and Cal Poly physics Professor Ryan Walter. "Not only do you lose the plants, but you also lose all of the services that they provide for the entire ecosystem."

By slowing down currents and decreasing wave forces, seagrasses help stabilize sediment and prevent erosion. Over the last century, Morro Bay has been building up sediment quickly and is dredged annually.

After the eelgrass died off, however, erosion took place in more than 90% of the places where eelgrass previously grew. In some places, the erosion removed enough sediment to cause the water depth to increase by as much as 50% compared to when eelgrass was present. At the mouth of the estuary where eelgrass remains, sediment is still building up as it did in the past.

"These erosional changes are sizable considering that Morro Bay, a modified estuary, has historically suffered from accelerated sedimentation," Walter said.

Globally, seagrasses in the nearshore coastal environment are among the most threatened ecosystems on the planet. Generally, losses of seagrasses can lead to increased shoreline and estuarine erosion.

On the other hand, it is possible that the erosion in Morro Bay may create new opportunities for seagrass recovery by increasing the depth and suitable habitat for eelgrass in certain locations. Recent restoration attempts by the Morro Bay National Estuary Program have been successful, and there is evidence of a partial recovery in portions of the bay. Tracking changes in sediment in places like Morro Bay will become increasingly important as climate change is expected to drive sea level increases and shoreline change.

"Morro Bay is an estuary of national importance that is under transition with system-wide eelgrass loss, subsequent sediment loss and now some signs of eelgrass recovery. Understanding the dramatic changes in Morro Bay can help identify important factors for management and conservation of eelgrass-dominated systems globally," said coauthor Jennifer O'Leary, former California Sea Grant Extension Specialist.
-end-


California Polytechnic State University

Related Climate Change Articles from Brightsurf:

Are climate scientists being too cautious when linking extreme weather to climate change?
Climate science has focused on avoiding false alarms when linking extreme events to climate change.

Mysterious climate change
New research findings underline the crucial role that sea ice throughout the Southern Ocean played for atmospheric CO2 in times of rapid climate change in the past.

Mapping the path of climate change
Predicting a major transition, such as climate change, is extremely difficult, but the probabilistic framework developed by the authors is the first step in identifying the path between a shift in two environmental states.

Small change for climate change: Time to increase research funding to save the world
A new study shows that there is a huge disproportion in the level of funding for social science research into the greatest challenge in combating global warming -- how to get individuals and societies to overcome ingrained human habits to make the changes necessary to mitigate climate change.

Sub-national 'climate clubs' could offer key to combating climate change
'Climate clubs' offering membership for sub-national states, in addition to just countries, could speed up progress towards a globally harmonized climate change policy, which in turn offers a way to achieve stronger climate policies in all countries.

Review of Chinese atmospheric science research over the past 70 years: Climate and climate change
Over the past 70 years since the foundation of the People's Republic of China, Chinese scientists have made great contributions to various fields in the research of atmospheric sciences, which attracted worldwide attention.

A CERN for climate change
In a Perspective article appearing in this week's Proceedings of the National Academy of Sciences, Tim Palmer (Oxford University), and Bjorn Stevens (Max Planck Society), critically reflect on the present state of Earth system modelling.

Fairy-wrens change breeding habits to cope with climate change
Warmer temperatures linked to climate change are having a big impact on the breeding habits of one of Australia's most recognisable bird species, according to researchers at The Australian National University (ANU).

Believing in climate change doesn't mean you are preparing for climate change, study finds
Notre Dame researchers found that although coastal homeowners may perceive a worsening of climate change-related hazards, these attitudes are largely unrelated to a homeowner's expectations of actual home damage.

Older forests resist change -- climate change, that is
Older forests in eastern North America are less vulnerable to climate change than younger forests, particularly for carbon storage, timber production, and biodiversity, new research finds.

Read More: Climate Change News and Climate Change Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.