If you’ve ever visited Sungei Buloh, the first thing you probably noticed is the scent of salt dancing on the sea breeze, courtesy of the seawater that flows into the mangroves from the sea. In this post, I highlight the salinity gradient present in the mangrove ecosystem, which manifests as changes in vegetation as we move from the back mangrove to areas closer to the sea.


Photo 1: Back mangroves with high canopy cover. Photo taken from Google Maps.

During our NUS GE3255 Aquatic, Riparian and Coastal Systems class field trip, we noticed how the more densely vegetated back mangrove (Photo 1) gives way to more specialised, salt-tolerant species closer to the sea. For example, in the back mangroves, vegetation resembles that of a tropical rainforest, with common species such as strangler figs (Ficus sp.) and fishtail palms (Caryota mitis) observed in both. However, if you look closely, you can find plants that are dispersed by water in the mangroves, the most common being the Pong Pong tree (look for the tennis ball-sized round fruit!).


Photo 2: Transition between Back and Front Mangrove. Photo taken from Google Maps.

As we move further into Sungei Buloh, canopy cover becomes sparser as only plants that can tolerate salt and flooding survive, reducing the variety of species seen.


Photo 3: Mangrove Seaward Zone. Photo taken from Google Maps.

Making our way to the seaward zone, this area has the most extreme conditions and thus is the least vegetated. This area is subject to periodic flooding, owing to daily tide changes. As a result, the soil has the highest salinity, most hydric soil, and barely any leaf litter as compared to the more inland areas. The few species, such as Avicennia and Rhizophora, that make their home here have special roots to breathe within the frequently-waterlogged soil and to filter excess salt when taking up water! Some species even involve their leaves in accumulating or secreting excess salt!

The next time you have the opportunity to visit Sungei Buloh, see if you can recognise the different zones of the mangroves! They are a beautiful and unique ecosystem, providing many benefits such as coastal defence and habitats for migratory birds. Let’s save them before it’s too late!