EcoMENA

It appears that the Arabian Gulf is a preferred location for the marine dugong as the second largest population of this species, after those located in Australian waters, are found in the Gulf waters. The largest group sightings have been north-west of Hawar Island (between Bahrain and Qatar). From recent studies published in the Journal of Biological Conservation, the local population is around 6,000 dugongs. Just who or what is the dugong?

What are Dugongs?

The dugong belongs to the taxonomic group referred to as the Sirenian. It is one of four living species belonging to the order Sirenia. The other three species are the manatee.  It is a marine mammal (i.e. no basking in brackish waters or river outlets), and the only herbivore mammal.

Difference between Dugong and Manatee

Both dugong and manatee are marine mammals often referred to as “sea cows”. They are similar in appearance and behavior.  But there are some key differences. These differences show up in the design of their tail, their habitat, and a few physical features.

Dugongs have fluked tails (two tips) like the tail of a dolphin or whale while the manatee have paddle-shaped tail (singular). The dugong is only located in marine waters whereas the manatee is found in both freshwater and saltwater environments. The dugong is totally intolerant of freshwater. The dugong weighs considerably less than the manatee. The average weight of an adult dugong is between 250 to 400kg. The manatee on the other hand, weighs between 400 and 500kg. The dugong is smooth skinned compared with the wrinkly and rough-skinned manatee.  And the distribution of dugong is mainly in the Indian and Pacific Oceans while the manatee tends to frequent the Atlantic waters.

Dugongs in the Arabian Gulf

Dugongs are known by various local names both in Bahrain and the Arabian Gulf. The names of the mammal include arus al bahr (Arabic: bride of the sea), baqarah al bahr (Arabic: cow of the sea), and cow diryali (Farsi: marine cow).

The Arabian Gulf is an interesting environment as it has some very shallow waters, is semi-land locked, and is surrounded by desert lands.  This makes for a harsh, saline environment.  The seawater has high levels of salinity and extreme water temperature variability. The summer water temperatures can get very high and cool excessively after sundown. Summer water temperatures have been recorded as high as 38^oC, peaking to 40^oC in the very shallow waters, while winter temperatures can drop to 11^oC.  Therefore, the average annual range of water temperature can have a very wide range (~27^oC) which is very stressful for the marine life.

The dugong is an herbivore.  It is the only marine mammal whose entire diet is plant material. It is largely dependent on seagrass ‘meadows’ for its food source.  Consequently, the dugong favours the shallow, coastal waters especially along the south-west margin of the Arabian Gulf. Hence, their presence in the waters surrounding Bahrain. And in the waters of the neighbouring GCC countries.  In the area north-west of Hawar Island, there have been sizable clusters (around 600) of dugongs observed and documented since the 1980’s.

Relationship between Seagrass and Dugongs

The seagrass ‘meadows’ are vital for the survival of the dugong as it is their main food source. The seagrasses are best described as flowering plants that exist in shallow marine waters with low turbidity. They are also associated in areas where there are mangrove  plantations,  and reef ecosystems.  These are all ecosystems which can tolerate the extreme temperatures and high salinity. The dugong prefers the quieter waters with minimal wave action. It favours their more gracious style of movement in the water. There is also limited wind flow over these waters meaning that the turbulence is low. Lower levels of turbidity means clearer waters as the sand sediment is not stirred up as frequently.

The ideal calmer,  shallow water areas are limited areas. The seagrass beds have been diminishing over the recent decades. Seagrass ‘meadows’ cover a very small portion of the ocean sea floor (only 0.2%). Therefore, both the seagrass beds and the dugong need to be well  protected to ensure the survival of this mammal and its preferred habitat.

Threats Posed by the Oil Industry

The Arab Gulf region is also a major centre of oil extraction, processing and refining ready for export. The oil industry can be a major threat to all natural ecosystems but especially to aquatic systems. There are many other activities that also pose challenges. Activities associated with land claiming such as seabed dredging threaten the health and survival of the seagrass meadows. [One cannot use the term, land reclaiming as the present day islands did not exist previously. They are man-made features.] The threats are both direct and indirect.

Dredging involves the physical removal of substrata but also contribute to the rising levels of turbidity in the waters, lowering the clear visibility in the waters, and disturbing the natural characteristics of the marine ecosystems.  As the nation develops, there are more occurrences of discharge of industrial effluents, even if at acceptable levels set by the environmental regulatory bodies. Therefore, concerted conservation methods are essential to ensure the survival of these mammals, and the long-term sustainability of the marine environment.

As well as the impact of urbanization on the island, there are a number of other threats that could endanger the lives of the marine mammal.  Such threats include intensive fishing in near-shore waters, the use of large-mesh fishing nets, invasion by new (alien) fish species, increased migratory bird life, other non-petroleum industrial pollution, extensive coastal and offshore island development, discharge from desalination plants that have both thermal and very high saline impacts.

All these ongoing activities, plus the constant threat of climate change and environmental warming, contribute to the challenge of protecting a vulnerable and very sensitive ecosystem, and the even more vulnerable dugong species.

Overall, the natural environment of the Gulf waters, is very fragile. Not just for the dugong, but many local marine species are subjected to a variety of both natural and man-induced practices which threaten their long-term viability in the region. Since the turn of the 21st century, there has been a significant increase in the human population, land reclamation and the formation of island developments, and more intense fishing practices in the local region. So nature is competing with humankind to an even greater degree.

The extreme climatic conditions – desert, hyper-arid, highly saline, ever-increasing sea and air temperatures, and extreme evaporation rates all combined, limit the abundance of local biodiversity in the waters of Bahrain. And since the discovery of oil, there have been various spillages into these waters from surrounding oil installations. These incidents have severely impacted the marine environment in the past. And there is possible evidence of ongoing impacts resulting in reduced marine life populations.

Why Dugong is Facing Extinction

The dugong is vulnerable to extinction for various reasons. First it has a very limited food source, seagrass which is also threatened. Although the dugong has a long-life span, it experiences very slow reproduction rates. It also devotes a significant amount of time caring and nurturing its young. The population growth rate is very low, around 5% per year. This translates to the species being very vulnerable and tend towards less favourable survival rates.

However, the main threat to the survival of the dugong is from the various modes of fishing, especially with the variety of nets used. The mammal is not fast swimming and also needs to come to the water surface for air every 3-12 minutes making it vulnerable to other threats. It would be very easy for the mammals to encounter or encroach upon fishing activities, or even be hit by fast moving vessels.

As well as needing to protect the very endangered dugong, there are other factors why the seagrass ‘meadows’ should likewise be well protected. It has already been mentioned how little of the ocean is covered with the precious seagrass. Yet the seagrass has an amazing carbon sink capacity. The seagrass ‘meadows’ capture around 10% of the carbon sink capacity of the entire oceans. This translates into seagrass carbon storage is far in excess of the carbon storage capacity of the Amazon rainforest.

Not only does seagrass provide essential food resources for the dugong mammals, but it also provides nursery grounds for both juvenile shellfish and finfish. It acts as a carbon storage of very significant proportions. It has been estimated that a third of the global seagrass habitats have already been lost through human activities. But it is still very worthwhile protecting and nurturing as it can also make a significant contribution to managing global warming and subsequent climate change.

The Way Forward

There are conservation measures and environmental laws in place to protect the dugong species and their natural seagrass environment. The laws are designed to combat polluting activities and the overall protection of the natural environment thereby preserving the dugong in their natural habitat.  It would be good to see more aggressive measure to ensure the safety and longevity of the dugong species, while preserving the seagrass ‘meadows’ and enhancing their regrowth in regions where the seagrass has already been depleted.

Research scientists are the first to admit that the role and habitat of the dugong and the seagrasses is not well understood. This is because the mammal numbers have been diminishing in significant numbers and species have retreated from inhabited regions. But by raising awareness of the uniqueness of these marine creatures living in a multifaceted ecosystem that benefits the whole globe from various perspectives, both are worth protecting and saving, promoting their existence and benefiting the whole globe as a most worthy outcome of human endeavour.

You can read up more on the Dugong and Seagrass Conservation Project operating across the globe as presented on the website https://dugongconservation.org