Mangrove Observation in Wonorejo River Estuary

by Pippin Barry

Firewood, fish farms and rubbish are what remains at the area of Surabaya’s mangrove forests. Today Bram, Curtis, Sukri, Sugeng and I did an observation of the delta leading into the bay of Surabaya. The view from the river boat is deceptive. The banks are lined with mangroves where birds nest and monkeys swing from branch to branch. Behind this front most of the mangroves have been cleared.

To begin the observation we went out onto the mud flats. Knee-deep mud greeted us as we surveyed what creatures were living in the mud. Growing up in a similar environment in Australia I noticed a lack of biodiversity on the mudflat. The only creatures we found were small clams and evidence of a type of tube worm. This is compared with the vast array of sponges, feather-duster worms, scallops, carpet anenomes and sea grass found on the Great Sandy Straights in Queensland Australia. While there are many variables that control biodiversity it is likely that pollution coming down the river has killed off many of the invertebrates.

Invertebrates, such as worms, sponges, crustaceans, are sensitive to changes in water chemistry particularly to the presence of some metals like copper. It seems the clams that we found are more can survive in a harsher environment and without competition have thrived.

Heading back into the mangroves we revisited the trees planted two years ago. Mudskippers hopped around the descending roots of the juvenile plants. A different species of mangrove was growing further into the conservation area, on sandier soil, and was too thick to explore. Unfortunately because most of the mangrove forest was destroyed we couldn’t find a patch to perform a good survey of the animals living there, however, we encountered several bird species on the way back.

I’m keen to explore more of the shoreline to see if there is some old forest intact. If so we can collect more information about what the natural mangrove forests of Surabaya contain – to use in our education campaign – and prove just how rich the diversity of life is in the forest.