Eelgrass meadows are underestimated biodiversity hotspots

In recent decades, eelgrass meadows have significantly declined in the southern Bohus county in Sweden, and in many areas have disappeared completely. 

Since eelgrass serves as a habitat or nursery for a variety of aquatic organisms, such as young cod, crabs, and shrimp, they are highly important for biodiversity, and their decline could thus have disastrous consequences for many coastal ecosystems.

Moreover, since eelgrass roots also bind the sediment, they prevent erosion and limit resuspension of sediment in the water.

For over a decade, a team of researchers from the University of Gothenburg has been working on the restoration of eelgrass meadows. Their most recent assessment of this initiative is highly positive, showing that fauna returned rapidly once the eelgrass started to grow again. 

In fact, already in the second summer, the biodiversity in the planted meadows was almost the same as in the old established meadows. The study is published in the journal Restoration Ecology. 

How the research was conducted

During the summer of 2019, the scientists planted eelgrass shoots in four test plots of different sizes on the seabed, with different spacing between the shoots.

By autumn 2020, new populations of invertebrates that live or burrow in bottom sediments were already thriving in the young meadows.

“The recolonization has been very rapid. After the first three-month growing season, up to 80 percent of the invertebrates had returned to the newly planted eelgrass,” said study senior author Eduardo Infantes, a marine biologist at Gothenburg.

Observations have also revealed that size did not play a major role in the recovery of biodiversity in the meadows. Even if eelgrass did not have time to grow to the same density as in an established meadow, after only two growing seasons, the level of biodiversity was just as high as in old meadows.

“This is good news for future restorations and new plantings of eelgrass meadows. We can plant new smaller plots with fewer shoots and this saves money because it is an expensive method for restoring biodiversity on the seabed,” Infantes concluded.

More about eelgrass 

Eelgrass, which belongs to the genus Zostera, is a group of species of submerged aquatic plants that live in marine environments along coastlines. Here are some key facts about it:

Habitat

Eelgrass is found in temperate and cold waters in the Northern Hemisphere. It thrives in shallow coastal areas, lagoons, and estuaries where sunlight can reach the seafloor.

Appearance

As the name suggests, eelgrass has long, ribbon-like leaves which often form dense underwater meadows. These grass-like leaves are usually bright green, and the plant can produce small flowers and fruits.

Role in the ecosystem 

Eelgrass beds are very important ecologically. They provide valuable habitats and nurseries for many species of fish and invertebrates. They also help to improve water quality by absorbing nutrients, and their root systems stabilize the seafloor, preventing erosion.

Threats and conservation

Eelgrass populations have declined in many places due to factors such as pollution, coastal development, dredging, and disease.

Climate change is also a potential threat, as changes in sea level or water temperature could negatively affect eelgrass. Various conservation efforts are underway to protect and restore eelgrass habitats.

Scientific research 

Eelgrass is the subject of much scientific research. For example, it has been found to sequester carbon dioxide at a much higher rate than terrestrial forests, making it an important potential tool in the fight against climate change.

Eelgrass and climate change 

Eelgrass, like other types of seagrass, plays a significant role in climate change mitigation. Here’s how:

Carbon sequestration

Eelgrass meadows are exceptional at sequestering carbon, trapping it in the sediment below. They can absorb and store carbon dioxide from the atmosphere at rates over ten times faster than forests on land.

This process, known as “blue carbon” sequestration, helps to mitigate the impacts of increasing atmospheric carbon dioxide levels, which is a primary driver of global climate change.

Coastal protection

Eelgrass also acts as a buffer against coastal erosion, which can be exacerbated by climate change. Rising sea levels and increased storm surges can lead to significant erosion, and eelgrass beds help protect coastlines by stabilizing sediment and dampening wave action.

Biodiversity and resilience

Eelgrass beds are biodiversity hotspots, providing food and shelter for a wide range of marine life. Biodiversity often equates to ecosystem resilience, and maintaining healthy, diverse ecosystems is key in the face of climate change.

However, eelgrass is also vulnerable to climate change. Rising sea temperatures can lead to increased prevalence of diseases that affect eelgrass.

Changes in salinity and nutrient levels, ocean acidification, and increased storm intensity can also negatively impact eelgrass meadows.

In the face of climate change, conserving and restoring eelgrass meadows are crucial actions. Despite their importance, these ecosystems are often overlooked in climate policy. Increasing awareness about the value of “blue carbon” ecosystems can help drive conservation efforts and support sustainable management of these critical habitats.

—-

By Andrei Ionescu, Earth.com Staff Writer

Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.