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Tuesday, 18 January 2011

Can seagrasses survive when they're buried by sediment?

That was one of the questions our Oceans Institute team set out to answer when we embarked on a recent month-long field trip to the small, sleepy island of Pulau Tinggi, Malaysia.

Sediment deposition is a common phenomenon on Southeast Asian coasts due to runoff from intense land development, as well as from the frequent sand mounds created by burrowing and grazing fauna.

We simulated these effects by laying out PVC pots among the seagrass meadows and burying them with sediment at a range of depths. Our results revealed that seagrasses were adversely affected when buried under more than 4 cm of sediment, as evidenced by declines in shoot density and abundance.

The burial experiment was just one aspect of the trip. The overarching goal was to examine how seagrass spatial patterns are affected by sediment properties, sediment mobility, and faunal activities.

This is valuable knowledge, as seagrass meadows in Southeast Asia occur in coastal areas of extremely high sediment runoff, and are expected to decline more than anywhere else in the world.

Our team of SCUBA divers collected seagrass and sediment cores from all around Pulau Tinggi and her neighbouring island, Pulau Sibu, to construct species distribution models. On alternate days, we monitored seagrass patches in twenty plots to see if seagrass growth was affected by physical disturbance from dugongs, benthic invertebrates and burrowing shrimps.

During our stay, we were approached by local officers from the Marine Parks Department to help them investigate coral bleaching in the area. Sadly, the footage we collected showed approximately 80% of corals were bleached, with sea anemones showing similar effects.

Our team also had the honour of being asked to run marine education activities with some very enthusiastic children from a local community club called Kelab Alami Tanjung Kupang (Tanjung Kupang Environment Club).

Gary Kendrick, Kimberly Van Niel and Marion Cambridge gave the kids a glimpse of the underwater world by taking them for their first snorkel, while Renae Hovey, Jillian Ooi and Affendi Yang Amri gave presentations on seagrass and corals.

After a week, we bid farewell to the fearless leaders in Gary and Kimberly, and welcomed John Statton to island life. When spring tides kept us from working in the water around Pulau Tinggi, we took up an invitation from John Amos to visit his two resorts and Turtle Hatchery at Juara Village on a neighbouring island called Pulau Tioman.

Here we gave presentations to school groups at John's resorts: the Garden International School in Kuala Lumpur, and three Australian schools participating in the Round Square Conference 2010.

After interacting with the students and teachers, we realized that we had made head way in promoting the importance of these benthic habitats - seagrasses in particular, which went from being unknown to the most talked about thing in Juara village!

­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­­By Jillian Ooi and Renae Hovey

Page 8: The UWA Oceans Institute December Newsletter

Media references

Maryann Evetts (The UWA Oceans Institute), (+61 8) 6488 8116

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