World Seagrass Day: Learn more about the wonders of this often overlooked ecosystem

Written by Matthew Vincent Tabilog, Founder of MMPH

Today is World Seagrass Day, a day to recognize one of the ocean’s most vital yet overlooked ecosystems. Often mistaken for seaweeds, seagrasses play a critical role in promoting climate change mitigation, biodiversity, fisheries, culture and tradition, and coastal protection. Conserving them is important and in doing so, learning more about this marine habitat is the first step.

What are Seagrasses?

Seagrasses inhabit an extremely physically challenging environment where they are submerged in marine waters and grow mostly in mud or sand, similar to mangroves but the seagrass genus, Phyllospadix, is reported to have the ability to cling to rocky shelves. Beyond that, seagrasses are flowering plants that are well-adapted to the conditions of the marine area distributed along shallow and subtidal waters and estuaries, both in tropical and temperate regions of the world, in exception to Antarctica.

To survive in these harsh environments, seagrasses have multiple adaptations for them to survive. In line with their growth and structure, the extension of their rhizomes results in seagrasses expanding, like forming clones, to occupy space which leads to seagrass meadows that often comprise wide areas dominated by a single species, however mixed-species are also observed in a meadow. This adaptation allows them to hold sediments in place and reduce their mobility. As for photosynthesis, it is similar to land plants in absorbing light and carrying out gas exchange that both acquire carbon dioxide and produce oxygen. However seagrasses require greater irradiance, which in practice means that they are highly restricted to intertidal, shallow, and subtidal zones but the deepest seagrass species was recorded growing at a depth of over 100 meters in the Mediterranean Sea. As seagrasses evolved from land-based plants to live in the sea, adapting to high salinity became essential and integral. They tolerate these conditions through osmoregulation which reduces physiological stress.

Seagrass meadow in Bolila Island, Hinobaan, Negros Occidental

This coastal habitat is considered a blue carbon ecosystem, such as those of mangroves and tidal salt marshes, for playing a major role in sequestering higher concentrations of atmospheric carbon per hectare compared to their terrestrial counterparts. Aside from their role in sequestering carbon, they also provide valuable services given their roles in enhancing fisheries, promoting high rates of productivity, nutrient cycling, stabilizing sediments, and reducing waves. These are critical food sources for marine invertebrates to large marine vertebrates like turtles and dugongs.

Seagrasses in the Philippines

The Philippines comprises 18 seagrass species from two families, Potamogetonaceae and Hydrocharitaceae. These marine plants are locally known as “Lusay” and coastal communities depend on this ecosystem as their sources of livelihood and food. During low tides, women utilize the seagrasses for gleaning, a subsistence-based fishing method of obtaining marine resources (shellfish, crustacean seaweeds) along intertidal zones during low tide. However, this type of fishing is vital but always seems to be an overlooked aspect in food security and sustaining income to communities. This is why investing in local ecological knowledge is important to support conservation efforts.

As such, seagrasses do not hold the same spotlight like mangroves and coral reefs in terms of conservation and protection in the country and globally. It is important to see the synergy and connectivity between our seagrasses, mangroves, and coral reefs as they collectively support fisheries as a whole. Even in research, most studies are geared towards our mangroves and coral reefs. Future studies should also include our seagrasses to learn more about them and find solutions for their conservation.

Sea urchin gonads are extracted during gleaning as a food source for communities in Dumaguete City, Negros Oriental

Threats to our Seagrasses

Despite the importance of seagrasses, this habitat is considered to be among the most threatened ecosystems on earth with rates of loss from a median of .0.9% and 7% annually before 1940 and 1990, respectively. The main threats to this ecosystem include anthropogenic pressures that lead to eutrophication, primarily from coastal developments that degrade the water quality.

In the Philippines, our seagrasses are highly susceptible to changes in the environment due to dump-and-fill projects like reclamations. Our government should highlight the importance of these ecosystems and should think carefully before they sign permits, especially DENR that has the authority in providing ECCs or Environmental Compliance Certificates, to corporations that allow this environmental fragmentation to happen.

The Future of Our Seagrass

As the impacts of climate change tend to be more frequent and intense, our seagrasses are increasingly vulnerable from such environmental changes. It is high time to advocate for the protection of this ecosystem and call out projects and anthropogenic pressures that continue to degrade them. Our future for our seagrasses can be bright if we invest more in studying and protecting them.