Seagrasses can help mitigate climate change

The Philippine may help mitigate climate change by sequestering significant pollutant carbon dioxide from fossil fuel-run vehicles.  This can be done by tapping its huge carbon stock potential from its ocean’s seagrasses, according to a research arm of the Department of Environment and Natural Resources (DENR).

With 7,107 islands strewn across 2,200,00 square kilometers of ocean, the Philippines has one of the world’s longest coastlines (36,289 kilometers, to be specific).  As such, the Ecosystems Research and Development Bureau (ERDB) has embarked on a basic research on carbon sequestration potential of seagrass beds.

A blue carbon study conducted in Lian, Batangas showed that a 50-hectare seagrass meadows can capture 97 megagrams of carbon dioxide equivalent to the annual emission of 20 cars.

“Some people think seagrasses are mere colonizers and can quickly appear and disappear. Others think that planting of mangroves on seagrass beds is all right. As such, our objective is to unfold another important ecological value of seagrasses in the ecosystem,” said Jose Isidro Michael T. Padin, ERDB supervising science research specialist.

The Philippines has 16 species thriving along its coasts. This makes the country as having the second highest species of seagrasses around the world – after Western Australia which has more than 17 species of seagrasses.   The Philippines has more seagrass species than Indonesia, Malaysia and Brunei.

The same blue carbon study is also involved in the identification of seagrass species that have high carbon sequestration capacity to offset emissions.

Aside from Lian, Batangas, the ERDB is also conducting blue carbon study in Alabat Island, Quezon; Coron, Palawan; Catanauan, Quezon; and Masinloc, Zambales.

Dr. Theresa Mundita S. Lim, former director of Biodiversity Management Bureau, said the Philippines has a total seagrass area of 27,282 square kilometers, which are widely distributed throughout the country: from Bolinao Bay (Pangasinan) in the north, Palawan and the Cebu-Bohol-Siquijor area to the center, and Zamboanga and Davao in the South.

But like the two other marine ecosystems — the coral reefs and mangroves — the seagrasses are also in deep trouble.

“In spite of the ecological and economic value of seagrasses, between 30% to 50% of the seagrass beds have been lost… in the last 50 years,” said Dr. Lim.

The country’s seagrasses have been threatened by human activities such as heavy dredging from construction works, grounding of vessels and motorized boats, release of chemical-filled effluents from human activities, and overfishing.

Dr. Miguel D. Fortes, the country’s foremost expert on seagrasses, said it is high time that Filipinos should pay attention to this vanishing ecosystem. “Despite their high biodiversity and abundance, seagrass habitats are still poorly understood in our country,” he said. “Hence, it appears only marginally useful when, in fact, the ecosystem plays significant economic and ecological roles.”

Dr. Fortes, who presented a paper during a mini-symposium on seagrasses and seagrass ecosystems during the International Coral Reef Symposium some years back, said that seagrasses are among the most productive of coastal ecosystems, matching coral reefs and mangroves in terms of environmental and economic importance. “As meadows, seagrasses are an important link between land and ocean and support a high primary production,” he pointed out.

Since the time of the dinosaurs, three groups of flowering plants have colonized the oceans. Seagrasses, however, are the only flowering plants that can live underwater. More closely related to terrestrial lilies and gingers than to true grasses, they grow in sediment on the sea floor with erect, elongate leaves.

Dr. Fortes described seagrasses in these words: “Just like the grasses that we normally see outside our homes, they are flowering plants. But the only difference is that they complete their life history submerged in seawater, forming extensive meadows on sandy to muddy sediments in shallow coastal waters.”

Seagrasses – common known as isay or lusay – are quite different from seaweeds, which are algae. Seagrasses produce flowers, fruits, and seeds while seaweeds make spores. Seagrasses have separate roots, leaves and underground stems called rhizomes (which form an extensive network below the surface). Seaweeds rarely have “roots” below the surface. Unlike seaweeds, seagrasses are vascular plants – they have a network of veins to move nutrients and dissolved gases around the plant.

Ordinary people may find seagrasses useless, but they have important economic and ecological value, according ERDB Director Dr. Sofio B. Quintana. Such value, he said, may sometimes be underestimated due to their indirect nature.

Among the benefits derived from seagrasses are as follows: direct food source, nursery function (commercial fishes, coral reef fishes and tourism revenue), carbon sequestration, wave energy reduction (erosion control and coastline integrity, coastal real estate value), sediment stability, and improved water quality (from its use of marine nutrients).

“The rhizomes of seagrasses hold the sediment in place and thus reduce the flux of nutrients from the benthos into the water column.  This lessens the probability of (potentially pollutant) algal blooms that can cause permanent seagrass loss,” noted Bryan M. Dewsbury, a leader of seagrass experts.

Seagrasses are sometimes found growing together with corals –making up coastal resources that have huge ecological value in preventing coastal erosion, breaking the “power of the waves during storms, tsunamis,” the Worldwide Fund for Nature claims.

“Underwater meadows of seagrass offer important protection against pollution to both humans and coral reefs,” said a study published in the journal Science.  “Places with healthy seagrass – where sponges, clams, small fish and other filter feeders thrive – can reduce bacteria that is harmful to both people and marine life by up to 50%.”

Cornell University’s Dr. Joleah Lamb, lead author of the study, was quoted as saying: “The seagrass appears to combat bacteria, and this is the first research to assess whether that coastal ecosystem can alleviate disease associated with marine organisms.”

Those benefits are only for starters. They can also be used as fodder for livestock.  They are likewise a major component for sea farming and sea ranching.  As a matter of fact, the high primary production rates of seagrasses are closely linked to the high production rates of associated fisheries.

Among the diversified species found in the seagrass beds are fishes, sea cucumbers, sea urchins, crabs, scallops, mussels and snails. Shrimps spend the early stages of their lives in seagrass areas.

Large animals like sea cow (dugong) and green sea turtles graze extensively in seagrass meadows.  Seahorses, a tourist attraction and of medicinal value, reside in seagrass beds. A study done in five seagrass sites in the country identified a total of 1,384 individuals and 55 species from 25 fish families.

“All these have economic value mostly as food and aquarium specimens,” Dr. Fortes said. “Five times as many fish live in seagrass beds as above sea floors of mud, shells, and sand.”

It has been reported that in Australia, economic value of seagrass beds has been placed at $103.74 million per year owing to the market price of fish species that use seagrasses as their home.

Seagrasses also have economic value from medical raw materials.

Presently, the Philippines does not have any mature technology on seagrass rehabilitation.   And, according to Padin, seagrass transplantation studies have been conducted in the 1990s by academic research institutions in the country.  But those undertakings might have gained little success.

Seagrasses occur in shallow tidal flats, where they are exposed during low tides. Some species can grow down to depths of 12 to 60 meters.

“As meadows, seagrasses are an important link between land and ocean and support a high primary production,” Dr. Fortes reminded. – ###

(Photos courtesy of Dr. Miguel Fortes)