Green miracles in our blue ocean

02 Mar 2023 | Dan Benham

We are on a mission to restore ocean biodiversity. As Sea Rangers are preparing to work towards larger-scale restoration, let’s explore ocean biodiversity, the benefits it offers and how we can regenerate it.

Mighty marine meadows

Seagrasses are marine flowering plants that live in shallow, coastal waters and, similar to  grasses on land, they need sunlight to grow. There are 72 different species of seagrass that grow on every continent except Antarctica, all with different characteristics.

Seagrass meadows typically provide support for lots of aquatic life. It could be that smaller, or slower moving species find safety from predators within the canopy, or other species may choose to spawn amongst the seagrass, as a way to offer relative shelter to their offspring. Another major benefit of seagrasses is that they tend to store carbon from our atmosphere in their sediments. It is a little known fact that seagrasses occupy only 0.1 percent of the seafloor, but they remove one-third of all of the carbon that gets sequestered in the seafloor annually.

Around the world different species of seagrass often take on the names of the underwater species they support, such as turtle grass and manatee grass, which is found off the coast of Florida, or eelgrass that is prevalent across Europe. 

A Sea Ranger using a scope to look at seagrass below the waters surface.

Recently a single seagrass plant stretching over 180 km was discovered off the west coast of Australia. This individual plant has spread by extending its root system, and growing new shoots from them, making it the world’s largest living single organism. Based on its size and growth rate it is estimated to be around 4,500 years old!

Despite seagrass being an excellent resource for our planet, on average 1 hectare of seagrass is destroyed every hour. Globally the main causes are destructive fishing practices, coastal development and poor water quality or water pollution.

The Sea Ranger Service completed an initial pilot for monitoring seagrass off the coast of the UK in 2021 and Sea Rangers are now involved in preparing for new seagrass planting operations in the Netherlands and elsewhere in Europe.

Seaweed is versatile

Then there is seaweed. Quite unrelated to seagrasses, the term seaweed is used to describe thousands of different algae species. The main difference with seagrass is that seaweed doesn’t have the same kind of root system. Instead seaweed has an anchor-like system referred to as a ‘holdfast’ which helps to keep them stuck to rocks or the seabed. Unlike roots, these holdfasts don’t extract nutrients to feed the plant. 

Diagram showing the difference between algae, a common type of seaweed, and seagrass. Image courtesy of Project Seagrass

Though similar to seagrasses, seaweed has many ecological benefits like carbon sequestration and providing homes for sea life, but there are also commercial benefits. Some forms like Nori and Wakame are popular edible types of seaweed, and The Dutch Weed Burger makes burgers and hotdogs out of seaweed. Other, more unexpected uses, are using seaweed in cosmetic products like soap and facial creams, and remarkably as Notpla are doing in the UK, it can also be processed into a biodegradable replacement for plastics and other packaging. 

Sea Rangers using an ROV to monitor seaweed farms off the coast of the Netherlands.
Pinto beans in a plastic wrapping that is made from seaweed. Image courtesy of Notpla.

In previous years Sea Rangers have worked with North Sea Farmers to provide a low emission way to monitor their seaweed crops out at sea. Together with Vriezoo BV, we were able to use their underwater robot to monitor their test site seaweed farm, 3 miles off the coast of the port of Scheveningen in The Netherlands. 

What on earth is ocean chlorophyll?

Something else to consider is ocean chlorophyll. Even if it is microscopic, its impact is massive. Simply put, ocean chlorophyll uses photosynthesis to turn CO2 into food for underwater plants. This makes it an integral part of everyday life as it creates nutrients for the smallest of species that are right at the bottom of the food chain, something all ocean life relies on.

Ocean chlorophyll seen under a microscope
Sea Rangers pouring sea water through a filtration system to collect chlorophyll samples.

Chlorophyll also helps in other ways. By turning carbon dioxide into food for plants, chlorophyll plays a big part in the ocean’s carbon cycle, which in turn helps to mitigate the effects of climate change. It also balances ocean acidity levels, which is vital for ensuring marine life and things like coral reefs have a safe environment to survive. 

Chlorophyll in the sea alters the way it reflects and absorbs light, which is where the Sea Ranger Service comes in. One of our assignments for the Dutch government has been to monitor and ‘ground-truth’ chlorophyll data in the North Sea. Sea Rangers collect water samples in lab-like conditions from the Sea Ranger Service ship, store them in a specially designed lab-freezer on board, and then deliver them to be tested. The samples are compared to the readings from satellites of how much chlorophyll there is in the sea. This is only possible to monitor from space because of how the light is reflected when chlorophyll is present. Sea Rangers help validate crucial data that goes on to inform climate models and policies.

Underwater plants are incredible

Seagrasses, seaweed and chlorophyll provide integral support to life in the oceans. Whether that is providing food at the very bottom of the food chain, or by providing part of the carbon lifecycle. Sea Rangers continue to focus on researching and regenerating these unseen, underwater heroes and ensure, where possible, they can thrive.