Oct 26, 2006

Seagrasses in a nutshell

So we've given you a sneak peak of the many species of seagrasses found in Singapore waters and we've got the FAQs covered, save perhaps, THE most frequently asked question:

What on earth is a seagrass?

Seagrasses are marine flowering plants and are sometimes better known as dugong feed. They are often mistaken for seaweed or algae. However, unlike algae, seagrasses are unique in that they have flowers, bear fruit and produce seeds. Seagrasses complete their entire life-cycle immersed in water, with the exception of Enhalus, which must emerge to the surface of the water to reproduce.

Seagrasses also have a system of roots (rhizomes), stems and leaves, which are used for various functions including anchoring, photosyntheis (food production) and transport of nutrients and energy. They are often found growing in sandy or muddy substrates from which they obtain their nutrients. This is unlike algae, which derives its nutrients directly from the water column.

Although they can look very similar to their terrestrial namesakes, seagrasses are actually more closely related to lilies and gingers than to the grasses found on land.

More about seagrasses

Seagrasses are found in a range of coastal habitats, but Seagrass meadows are typically found in shallow, soft-bottomed areas. In Singapore, Chek Jawa (on Pulau Ubin) and Pulau Semakau have by far, the largest meadows with the highest diversity of seagrasses.

The different species of seagrasses favour different growth conditions. For example, Halophila ovalis (spoon seagrass) grows pretty much everywhere in Singapore. They're very hardy and often all it takes for them to grow is seawater, sand and not too much wave action. However, these often scoffed at little guys (they are often met on recce trips with a "Aiyah... ovalis again?") pave the way for other species of seagrasses to colonise the area because they improve surrounding conditions by stabalizing and increasing Nitrogen availability in the sediment.

On the other hand, we have Enhalus acoroides (tall tape/ribbon seagrass) which prefers harder areas (by harder, I mean you don't sink in and fall on your behind... as much) and are often found in small clumps in between coral rubble (on the far side of Chek Jawa) or on rocky shores (Labrador Beach and Sentosa).

Ask not what the seagrasses can do for you, but what YOU can do for the seagrasses

Not convinced you should help out? Well what if I tell you that seagrasses are extremely useful and productive habitats? In addition to stabalising coastal sediment, seagrass meadows on reef flats and near estuaries act as a buffer zone, filtering nutrient and chemical input into the marine environment. They also provide food, shelter and nursery grounds for a vast variety of organisms including molluscs, crustaceans (prawns, shrimp and crabs) and fishes (both the kind you eat (commercial species) and the kind you like looking at (reef fishes)).

Long term monitoring of seagrass habitats helps us understand the dynamics of these habitats and whether changes in distribution, cover and species composition are part of a natural process or the result of human influence. Data from regular monitoring also helps in coastal management.

So what can you do for our local seagrasses? Join team seagrass! You're guaranteed lots of fresh air, salt water, laughs and memories to last you if not a lifetime, then at least till the next monitoring session.

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