Every fortnight we feature a seagrass meadow from around the world. This week, Marjolijn Christianen shares her experiences working in the beautiful tropical island of Derawan in Indonesia. Marjolijn is currently a PhD student at Radboud University in The Netherlands. She has a blog detailing her experiences working with turtles and seagrass.

by Marjolijn Christianen

The Derawan Archipelago, is a hotspot of biodiversity and located in front of the Berau River on the mainland of East Kalimantan, Indonesia. In recent decades the once pristine rainforest and mangroves have been quickly transformed into palm oil plantations, coal mines and shrimp farms. Since all this activity is concentrated around the rivers it expected that the adjacent estuary will experience great effects of the increasing sediment and nutrient loads that will negatively affect the marine life & biodiversity of the adjacent estuary. So what is the effect of this on the seagrasses here?

(a) Map of the a Indo-Pacific Ocean with (b) The Derawan Archipelago and the (c) location of the exclosures on Derawan Island (d) Leaves are intensively grazed by green turtles, and a detritus layer is absent.

Following a pilot expedition of a Dutch group of marine biologists in 2003, we started with a 5 year PhD project in cooperation with the Indonesian Institute of Sciences (LIPI) and based ourselves on the small & beautiful Island of Derawan. The island is surrounded by a large shallow area (light-blue in picture c above) which is dominated by a mono species Halodule univervis meadow. On the other islands of the archipelago you can also find other species like Cymodocea rotundata, Cymodocea serrulata, Halophyla ovalis (with very rare dugong tracks), Enhalus acoroides, Thalassia hemprichii, Syringodium isoetifolium.

We found that the effect of increasing nutrient loads proved to be much less than the effect of the local grazers. Directly after arrival I was amazed by the extremely shortly grazed leaved, that were also very thin. It just looks like there is someone mowing the underwater seagrass lawns every day. And the extremely high densities of green turtles (Chelonia mydas) were found responsible for this. In our latest paper (Christianen et al. 2011, Journal of Ecology, link http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2745.2011.01900.x/citedby) we estimated that these hungry grazers graze 100% of the daily primairy production of the seagrass meadow.While populations of green turtle have dramatically declined at most other places, green turtle hotspots like Derawan could teach us about the historical role of the role of these megaherbivores. The green turtle not only drives structure and functioning of their foraging ground but also increases the tolerance of seagrass ecosystems to eutrophication (Christianen et al. 2011).

It is not difficult to spot green turtles grazing around the island

The majority of our fieldwork on Derawan focuses on unraveling the interactions between seagrasses, turtle grazing and increasing nutrient loads. A fancy fieldwork station is lacking but this stimulates to interact a lot with the (families of the) local fisherman that have a lot of knowledge about the ecosystems.

On a small island with 1500 people we always have enough attention from the local kids (left). Daily fieldwork life, working on exclosures 400 meters offshore of the island (right)

Working on such a remote island is amazing because you are surrounded by marine life such as green turtles, mantas, dolphins, frog fish, and (my favorite) the robust ghost pipefish (looks like a Thalassia leaf). But on the other hand you also have to plan your experiment well and buy your materials a full day travelling away, or even further. And don’t step in a stingray like I did because this will definitely slow down your fieldwork.

180 degrees panorama from the Telkom tower

Every fortnight we feature a seagrass meadow from around the world. This week, Ria Tan takes us on a tour of Cyrene Reef in Singapore. Ria is an avid naturalist and runs the wildsingapore webpage. In addition to hanging out in seagrass meadows, she enjoys exploring new intertidal reefs and has recently taken to trudging around in mangroves.


People normally assume that the best seagrass meadows are found in shallow, sheltered, clear waters far away from human impact and industry. That’s not the case in Singapore, a small island nation sitting at the tip of the Malayan Peninsular. One of Singapore’s best seagrass meadows is surrounded by massive petrochemical industries, a world class container terminal and major shipping lanes in one of the world’s busiest ports. Cyrene Reef is a 1km by 500m submerged reef with astonishing marine biodiversity!


On one side of the Triangle is Pulau Bukom, the site of Singapore’s first oil refinery, set up in 1961 by Shell. Today, the 500,000 barrels-per-day Bukom Refinery is the largest Shell refinery in the world, in terms of crude distillation capacity. On another side of the Triangle are the massive heavy industries on Jurong Island encompassing a wide variety of installations. Some industrial activities that can potentially impact marine life include flaring. Developed in 1974, the Pasir Panjang Container Terminal is the largest of Singapore’s four terminals. Together, the terminals handle about one-fifth of the world’s total container transhipment. Cyrene is at a key maritime crossroads where east-west traffic routes cross north-south traffic routes. About five hundred ships in excess of 5,000 DWT per day transit the waters around the Reefs.

Despite it’s location in the middle of this ‘Industrial Triangle’, Cyrene Reef is home to vast meadows with 7 seagrass species! Long ribbons of Enhalus acoroides are particularly spectacular when in bloom!

Cymodocea serrulata covers large areas of Cyrene Reef. These seagrass meadows are home to large numbers of Knobbly sea stars (Protoreaster nodosus). A study of these sea stars found that the presence of juveniles, subadults and adults, which indicates a healthy level of recruitment at Cyrene Reef. And that Cyrene Reef may be the only sustainable population of knobbly seastars left in Singapore today.

Cyrene is one of the few locations in Singapore where Syringodium isoetifolium is abundant. Other seagrass species on Cyrene include Cymodocea rotundata, Thalassia hemprichii, Halodule uninervis and Halophila ovalis.

Besides massive industries, frequent dredging also takes place near Cyrene Reef. Meanwhile, further reclamation is being considered at nearby Jurong Island. Just last week, a large fire broke out at the Shell refinery on Pulau Bukom close to Cyrene Reef. The fire raged for 30 hours before it was put out. It remains to be seen whether this massive industrial accident has impacted marine life on Cyrene Reef.
Cyrene Reef is one of the major sites monitored by the volunteers of TeamSeagrass, a collaboration with the National Parks Board
(NParks) and international Seagrass-Watch, the largest scientific,non-destructive, seagrass assessment and monitoring program in the world. TeamSeagrass includes about 100 volunteers from all walks of life who have been monitoring Singapore’s meadows since 2007. The data they collect is submitted to NParks for a better understanding and management of Singapore’s seagrasses and shores, and to Seagrass-Watch thus contributing to global understanding of the world’s seagrasses.
TeamSeagrass also gives ordinary people the opportunity to see first hand, some of Singapore’s best shores. Volunteers also have the satisfaction of making a difference for Singapore’s marine biodiversity.

Besides monitoring, TeamSeagrass volunteers also participate in other outreach efforts such as public exhibitions and in giving talks. TeamSeagrass also has a blog and facebook page for online outreach. This is one of the posters of seagrasses on Cyrene used in TeamSeagrass public exhibitions.


There is also an effort by a small team of volunteers to raise awareness of Cyrene Reef. The focus currently is to bring decision makers and selected corporations to visit the Reef and see it for themselves. Thus far, visits have been arranged for the Urban Redevelopment Authority, NParks and JTC (which manages Jurong Island).

Hopefully, these and other efforts to document and share Cyrene’s treasures will help protect this miraculous reef in the middle of an Industrial Triangle!

Find out more about Cyrene Reef and Singapore’s seagrasses at these sites
TeamSeagrass http://teamseagrass.blogspot.com/
Cyrene Reef Exposed http://cyrenereef.blogspot.com/

A new manual aimed at building knowledge and raising awareness of seagrass habitats has hit the shelves (well not literally)! The training manual, titled “Seagrass Syllabus” was developed by The World Seagrass Association and Seagrass-Watch in partnership with Conservation International.

The Seagrass Syllabus is the first of a series of initiatives that the WSA is taking to increase the profile of seagrasses within the global conservation arena. Many WSA members contributed to creating and designing the manual, and the WSA welcomes suggestions to continue to improve on the manual.

Although aimed at resource managers, the manual is accessible enough for the general public and it represents a useful tool to ensure that seagrass ecosystems receive due attention so that their ecosystem services can be secured for the future. The Seagrass Syllabus is made freely available worldwide to continue to increase awareness on seagrass ecosystems, to educate the general public and to improve the management of this critical resource.

To download a copy of the seagrass syllabus, please visit the WSA website or at this direct link: http://wsa.seagrassonline.org/images/stories/download/Seagrass_Syllabus.pdf

This is a the first of a series of fortnightly articles featuring seagrass meadows around the world. This week, Dorothée Pête of the University of Liege takes us to Calvi Bay in Corsica, which is one of her research field sites.
By Dorothée Péte

Although it’s nearest water body is the river Meuse, the University of Liege in Belgium has always had a strong interest in marine sciences. To strengthen the link between Liege and the sea, a research station was built in the late sixties, in Calvi Bay in Corsica, France. This research station with a catchy acronym – STARESO which stands for STAtion de REcherches Sous-marines et Océanographiques – which in English means “Station for underwater and oceanographic research” is a base for marine research carried out by the University.

Map of Calvi Bay (taken from Google Earth) showing the locations of STARESO, Punta Oscellucia, sewage outfall area, zone where Caluerpa racemosa was identified and location of fish farms. and other seagrass sites in the locality.

Calvi Bay is a wonderful place for studying seagrasses in the Mediterranean. It has two species of seagrasses, Posidonia oceanica (which is endemic to the Mediterranean Sea) and Cymodocea nodosa. This bay is of particular interest because all the major threats present in the Mediterranean Sea can be found in such a small area – making it a natural choice for studying impacts via field experiments. Plus, the view is spectacular both above and below water so you can easily understand why our lab (Laboratory of Oceanology) is working there and why I wanted to write a note to explain our field work.

Calvi Bay, Corsica - the view above water

Let’s begin with the STARESO. In front of the research station, you can find a continuous meadow of P. oceanica. This seagrass canbe found from near the surface (5 m depth in STARESO) to about 40 m depth, so scuba diving is essential if you want to work in this meadow. The meadow at the STARESO site is a reference one, thanks to its good state of health. Our lab has been following it for years, with a particular focus on the seagrass itself (its growth, density and leaf litter accumulations), but also on its epiphytes, nutrients and trace elements contents, food webs and on organisms living in the sediment. Of course, environmental parameters such as nutrients in surrounding and pore waters and temperature are monitored as well. The meadow is also part of the SeagrassNet monitoring program. In situ experiments like shading, microcosms, sediment loading and nutrients and trace elements dynamics (e.g. inside isolated jars) are being carried out there too.

Studies being carried out in Calvi Bay (from L-R): Nutrient dynamics, microcosm experiments and shading experiments

Just next to STARESO, near Punta Oscellucia, large amount of underwater leaf litter accumulations are present and are exported onto the surrounding beaches and there are currently studies focused on the dynamics of those litter patches and organisms living inside them.

Seagrass wrack accumulations off Punta Oscellucia

Sadly, it’s not all about beautiful seagrass and crystal clear waters in Calvi Bay as there are quite a number of threats in the area. It is widely known that the Mediterranean Sea is a major tourist attraction and a hub for marine recreation. In summer, tourists from all over the world invade the city of Calvi, causing direct stress to the seagrasses there through activities such as yachting but also indirectly due to increased sewage, which is another important (although slightly less glamorous) topic that our lab is studying by looking at the zones of the seagrass meadow situated near the sewege outfalls from Calvi.

Fish farming activities have been increasing in the Mediterranean Sea, and Calvi Bay has a small aquaculture industry. It is situated above a P. oceanica bed but it is fortunately quite well managed, so the impact on the meadow is very small. However, we are also studying the P. oceanica ecosystem in that zone for a better understanding of fish farming impacts.

Fish Farms floating in the waters off Calvi Bay.

The last (but not least!) threat that was identified very recently in Calvi Bay is the presence of an invasive seaweed species Caulerpa racemosa. We are just beginning to work on that subject and for now, it looks like it shouldn’t be a problem for P. oceanica in that zone. However, in other parts of the Mediterranean Sea, invasive seaweeds are causing more and more troubles to seagrass meadows. They are taking over areas formerly colonized by large beds of seagrasses and seem more resistant to environmental impacts than the seagrasses. In that way, they are becoming a threat for the coastal biodiversity of the Mediterranean by causing modifications in the habitats of numerous organisms (some of which are commercially important species) and a switch in communities, leading to a decrease in biodiversity.

I hope that I have convinced you how lucky we are to have such a nice site for field work, but if you want to see more and learn more about STARESO and the awesome people in my lab working seagrasses, please visit our website and check out the links below:

Laboratory of Oceanography, University of Liege:





Thanks to Klemens Gann, the WSA would like to share this seagrass video from the Philippines. If you have video you would like to share, please let us know.


To access the video click on the link below, and Enjoy!

Seagrass Symphony



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