In this series, we showcase the diversity of rare, peculiar, and fascinating native flora and fauna in Singapore. We enthusiastically invite you to explore our nature reserves and gardens, urging you to pause and observe your surroundings—whether by looking up or down—to see if you can catch a glimpse of these unique wonders.

Seagrass

Seagrasses are underwater plants that are commonly found in both tropical and temperate coastal waters. Seagrass is often confused with large seaweed. Unlike seaweeds, which do not have a root system and reproduce by releasing spores, seagrasses are true flowering plants and belong to the same group of plants as land grasses and lilies. They have leaves, roots and veins, and produce flowers and seeds––the roots absorb nutrients from soft sediment and the leaves make food through photosynthesis. Seagrasses thrive in shallow, protected coastal waters with sufficient sunlight. They can exist as a few plants or clumps, but generally form dense underwater meadows.

Image credit: Ria Tan, Wild Singapore

Seagrass habitats provide crucial services such as acting as shelters and nursery areas for numerous species––including animals like seahorses and juvenile fishes of larger commercially valuable fishes and marine creatures, contributing to nutrient cycling, improving water quality, stabilising sediments for coastal protection, and playing a big part in carbon sequestration by retaining carbon within their leaves and roots.  

In addition, seagrasses support a complex food web. They serve as the primary food source for sea turtles and dugongs in our waters. Sea turtles and dugongs eat seagrasses, including the seeds of the plants, and play a role in seed dispersal as they pass the seeds through their digestive systems and excrete them. Seagrasses also indirectly contribute to the food chain by hosting microscopic algae on their leaves. Smaller animals feed on these algae and, in turn, are prey for larger animals.

Image credit: Ria Tan, Wild Singapore

Seagrasses are one of the most productive ecosystems in the world and are vital for climate change mitigation. Seagrass ecosystems can sequester up to twice as much carbon from the atmosphere as land forests. They store large amounts of carbon through photosynthesis by trapping them in their stems. And when parts of the plants die and decay, they collect on the seafloor, eventually getting buried in sediment and effectively trapping carbon for hundreds of years. Although seagrasses account for less than 0.2% of the world’s oceans, they sequester roughly 10% of the carbon stored in ocean sediment annually.

Over the past fifty years, there has been significant and widespread decline in global seagrass cover, primarily attributed to human activities such as changes in land-use, coastal changes, dredging, and declining water quality. They are among the world’s most threatened ecosystems, experiencing an annual loss of approximately 1.5%. and accelerating in recent decades. It is estimated that at least 29% of the global coverage of seagrass meadows have been lost. The ecosystem services they provide make seagrasses a high conservation priority.

Seagrasses were previously abundant on Singapore’s shores, but their diversity and extent were never rigorously documented until recently. There are three major seagrass meadows in Singapore. They are at Chek Jawa Wetlands, Pulau Semakau, and Cyrene Reef.

Image credit: McKenzie et al, 2016

There are about 72 different seagrass species in the world. These are some of the species that are found in Singapore.

Common name: Tape Seagrass

Scientific name: Enhalus acoroides

Tape Seagrasses have long ribbon-like leaves that can grow up to 150cm long. They are often found close to mangrove forests. Tape Seagrasses are abundant at Pulau Semakau and Cyrene Reef.

Image credit: Ria Tan, Wild Singapore

Common name: Smooth Ribbon Seagrass

Scientific name: Cymodocea rotundata

Smooth Ribbon Seagrasses have flat narrow leaves that look like straps with a smooth rounded leaf tip.

Image credit: Ria Tan, Wild Singapore

Common name: Serrated Ribbon Seagrass

Scientific name: Cymodocea serrulata

Serrated Ribbon Seagrasses have a similar shape as Smooth Ribbon Seagrasses, with slightly wider leaves and a serrated leaf tip instead.

Image credit: Ria Tan, Wild Singapore

Common name: Sickle Seagrass

Scientific name: Thalassia hemprichii

Sickle Seagrasses have hooked curved-shaped leaves with short black bars on its leaf blade.

Image credit: Ria Tan, Wild Singapore

Common name: Noodle Seagrass

Scientific name: Syringodium isoetifolium

As its common name suggests, Noodle Seagrasses mimic spaghetti. The leaves are cylindrical and grow up to 30cm long.

Image credit: Ria Tan, Wild Singapore

Common name: Needle Seagrass

Scientific name: Halodule uninervis

Needle Seagrasses are long and narrow with a leaf tip resembling the letter “W”. They are the preferred food for Dugongs.

Image credit: Ria Tan, Wild Singapore

Common name: Fern Seagrass

Scientific name: Halophila spinulosa

Fern seagrasses look like… ferns! Tiny leaves are arranged in opposite pairs, and the “fronds” grow up to 15cm long. They can be found at Check Jawa.

Image credit: Ria Tan, Wild Singapore

Common name: Hairy Spoon Seagrass

Scientific name: Halophila decipiens

Hairy Spoon Seagrasses have small oval leaves and leaf hairs on both sides of the leaves. They were discovered on Singapore shores only in 2007.

Image credit: Ria Tan, Wild Singapore

A key consideration when visiting seagrass meadows:

The roots and rhizomes (underground stems) of seagrass are often buried in sand or mud. When trampled on, the underground stems can damage and take a long time to recover. So keep off the seagrass!

Join a conservation initiative!

Consider becoming a part of Team Seagrass–– a volunteer team working in collaboration with the National Biodiversity Centre of the National Parks Board and Seagrass-Watch. Help contribute to the monitoring of seagrasses along Singapore’s shores!

If you come across seagrass in the wild, we encourage you to (safely and respectfully) capture photos and document your observations. We especially recommend using the local SGBioAtlas app, or the iNaturalist app, which enables you to share and validate your findings within the community.

Discover the wonders of nature, observe the intricacies of the world around you, and let curiosity be your guide. Happy exploring!

📷 Post your findings on social media and tag us on Instagram or Facebook.

References and further reading:

🌱 What are seagrasses? (Team SeaGrass)

🌱 Seagrasses on the Shores of Singapore (Wild Singapore)

📄 The Diversity And Distribution Of Seagrass In Singapore

📄 Seagrass habitats of Singapore: Environmental Drivers and Key Processes