14 April 2013

Seagrass-Watch check up on Cyrene

Why are the seagrasses still 'chomped' short at Cyrene Reef? We tap on our seagrass gurus, Len McKenzie and Rudi Yoshida of international Seagrass-Watch HQ who join TeamSeagrass monitoring at Cyrene today.
TeamSeagrass volunteers monitoring at Cyrene Reef.
Although Cyrene lies in the middle of the industrial triangle next to shipping lanes heavily used by large container ships, this amazing submerged reefs has among the best seagrass meadows in Singapore.

Sadly, since 2011, we noticed that the Tape seagrasses on Cyrene have been 'cropped' short. Len and Rudi did have a look at this situation in May 2012, and things haven't improved much since then.
We checked the pool in the middle of the Reef and it's still rather bare. Although there are other kinds of seagrasses especially around the shallower edges, the Tape seagrasses here are still very short, even in deeper parts of the pool.
This is what the pool looked like in 2009, with Jeff and Collin of NParks doing a survey of the abundant variety of fishes found in the pool.
Pool of seagrasses on Cyrene facing Jurong Island
We find a small patch of Tape seagrass that are longer! Len explains to Rachel and Wei Ling that it is probably because the blades are all laying down, instead of sticking out. During Len's trip to Cyrene last year, he suggested that one reason why the Tape seagrass got 'chomped' was because it was too hot. Especially for those growing on the white sandy areas which reflects the light. Also, the rather stiff Tape seagrass tends to have a short portion standing upright, with the rest of longer leaf blade flopping over. The creased portion may have been weakened by exposure and heat.
Len points out how something has killed off the chlorophyll in the seagrass at a certain point. The tissues then eventually rotted away.
Len is also wondering what is causing the pits in the seagrass meadows? They are not burrows but are depressions. Somewhat similar to depressions caused by feeding rays.
Len shared how in the US when sharks were overfished in the 1970s, the population of cownose ray exploded. As the increased numbers of rays foraged in seagrasses for buried prey, they caused much damage. More about this in this SeagrasWatch magazine article on rays (pdf pg 23). Indeed, we have seen sharks trapped in driftnets laid on Cyrene Reef.
Shark trapped in driftnet in Jul 2010
Len asks, "Have you seen Spoon seagrasses (Halophila ovalis) flowering?". After we say no, he promptly takes a look at the clumps at this feet and produces a flower! We are most impressed!
Here's a closer look at the delicate flower made up of three filaments!
Len also found some fertilised flowers that eventually will form flask-like fruits. Which Pei Yan and I saw during TeamSeagrass monitoring at Labrador last year.
I also took the opportunity to photograph the pretty veins of this true plant that lives in the sea.
Rudi also showed us photos of dugong feeding trails he saw on Cyrene, which we all missed spotting! Wow! Siti saw dugong feeding trails here in Apr 2012.

More about the trip on the TeamSeagrass blog.

Everywhere on Cyrene, the Common sea stars (Archaster typicus) seem to be a frenzy of mating, with many in arms-interlocked position and some in stacks of more than two sea stars! The rest also observed Knobbly sea stars 'standing on their toes', which is a pose they adopt to release sperm and eggs in the water. Hmm...it is coming close to the usual Mass Spawning season for corals. Hope we hear good news soon from the scientists and volunteers who are keeping a close eye on this.
On the way home, I noticed the floating security barriers installed at Sentosa's reef actually goes onto the reef, across the seagrass meadows there and onto the natural cliffs! Oh dear. I'm worried that this will have some impact. Some of us will soon be taking a closer look at this shore to see what is happening there.
As usual, after the rainy morning, the water become brownish as we head away from Sentosa (on the horizon in this photo) towards the mainland. Rain washes sediments down the drains into the canal and into the sea, resulting in a 'flood' of brown sediment-laden water that can affect marine animals and plants. Monitoring of seagrasses helps keep track of how these coastal ecosystems are coping with these and other threats.
As we wait to group up with the rest on the other boat, we have a quick look at the amazing marine life that has settled naturally on the pontoons at Marina Keppel Bay.
Here's a glimpse of some of the marine life growing on the pontoons. These include hard and soft corals. It's amazing what marina life can naturally settle on artificial structures if we keep the water clean and protect the natural sources of 'babies'.
There's so much more to see and do for our shores. And as the predawn low spring tides resume with a vengeance, we will start to get some of it done!

Tomorrow we take Len and Rudi to Chek Jawa to see how the seagrasses are doing there.


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