Middle Bank: A Marine Sanctuary to Enrich the Future

By Professor Zulfigar Yasin

January 2022 FEATURE
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The flowering seagrass, Enhalus acoroides, the largest seagrass species in the world, is found on the Middle Bank. The seeds of these plants are a favourite food of the dugong. Unfortunately, there is no dugong population left in the Straits of Malacca.
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I CHANCED UPON an old British map of Penang from 1884 – it was a nautical chart of the sea. The Island's shoreline then resembled an irregular square which over the hundred-odd years since, had been rounded by reclamation. This is especially obvious on the eastern foreshore, where shallow coasts had since been reclaimed at Tanjung Tokong, Bayan Baru and Batu Maung.

While poring over the map, I noticed yet another interesting feature. It is a marine seascape where a long strip of shallow sea, known to locals as the Middle Bank or in Malay, "Tebing Tengah", runs almost parallel to the coast. On the map, its water depths are measured in furlongs and feet (one furlong is the equivalent of six feet). This narrow strip extends from Pulau Jerejak in the south to the foreshore of Weld Quay in the north; and is separated from the Penang coastline by a relatively deep water channel.

At the lowest tide, the Middle Bank reveals its rich marine ecosystem of interacting plants, fishes and invertebrates, rivalling that of rainforests. Fundamental to this ecosystem are its seagrass beds and shallow mudflats that house a variety of habitats, including oyster beds, mollusc nurseries and salt pools; these are also feeding and nursery grounds for many other marine creatures.

The sandbanks at low tide. The fast water current in the shallows carves intricate patterns on the sand. Only when the banks are stabilised are they suitable for colonisation by the seagrass.

Minute molluscs, crabs and cryptic animals feed on the microalgae that green the lawn of this saline soil. These creatures in turn become food for the carnivorous snails, starfish and sea anemones. The latter provide habitat to marine shrimps that are oblivious to their stings.

Some of the tiny snails and hermit crabs number in the thousands per square metre, enough to feed the foraging birds that frequent these habitats. From Siberia, migratory birds, in flocks of 10,000 to 12,000, stop in Penang on their way to Australia to feed on the mudflats of the Middle Bank. This epic journey along what is known as the East-Asian Australasian Highway, peaks in January and is one of the longest animal migrations on the planet.

The flood tides that come in to cover the seagrass meadows also bring in swimming creatures. Fish such as the mullets and catfish forage in the mud, unearthing ragworms and crustaceans; one can also find large stingrays and even dolphins hunting in the shallow waters. Also found on the Middle Bank are the commercial fish species trevallies, jacks, grunts, barramundis and snappers, as well as blue flower crabs.

Studies have highlighted the Middle Bank's importance as a nursery ground for marine life. Egg cases of snails are a common find here, as are frequent sightings of mating horseshoe crabs. The female horseshoe crabs are generally preferred for their eggs; this has caused a stark dwindling in their numbers within the last decade, save for the few that have escaped to roam the quiet shallows.

Not two decades ago, there were thousands of bristling spiked tails at the water's edge as they wait in anticipative patience to pair and mate. Even today, there are still small fish and crab larvae that swim among the floating Enhalus seagrass shoots – the largest seagrass species in the world. Their floating canopies afford protection from larger predators as well as food for the growing juveniles among the sea creatures.

The Middle Bank also provides livelihood for the fisherfolks of Batu Uban, Jelutong and Sungai Pinang, as it has done for the last few hundred years. Records show the fishing villages at Batu Uban to be one of the Island's earliest settlements. The small-scale fisheries use drift and cast nets, crab traps and long lines. Fishing in these communities is sustainable as there are no trawlers working there.

The nursery and feeding grounds of the Middle Bank also connect and support the ecosystems of Perak, Kedah and the offshore seas of Sumatra. Living ecosystems exchange nutrients and life across borders for health and survival.

Our Seas are Changing but Not for the Better

Sadly, the sea has now become warmer and more acidic, affecting coastal ecosystems and Penang's food bank. The higher temperatures and increased nutrients in the local waters have drastically lowered the oxygen level, resulting in frequent fish kills. Death of fish is but a causal effect of this decaying ecosystem. Imagine the unseen casualties beneath the waters!

A flower crab in a fish trap caught by local fishermen.

Sea levels will continue to rise, affecting coastal cities like George Town, Nibong Tebal and Alor Setar. Low-lying paddy areas that hug the coasts are especially vulnerable; even a small amount of saltwater can make the land uncultivable; not to mention the increased frequency of violent storms that lash at Penang's coasts.

The Middle Bank and its seagrass meadows have been buffers against these climatic impacts. The seagrass, for example, bind sediments and absorb carbon dioxide from the atmosphere in a process known as carbon sequestration, and is important in mitigating climate change.

During the launch of Phase 2: Accelerating Penang2030, Chief Minister Chow Kon Yeow announced the conservation of the Middle Bank as a marine sanctuary. This is a timely effort; it is after all Penang's future that we are ultimately securing. Until 2017, there were two green islands to the north of the Penang Bridge, but erosion had caused one to submerge underwater.

We have not treated our sea well. Pollutants have been pumped into it through river and drainage discharge; and plastics brought in by incoming tides form unsightly mounds on Penang's shores.

Trapped plastic debris on the Middle Bank. Plastics are hard to break down, which makes the material dangerous when they accumulate and are introduced into the food chain.

To be sure, coastal cleanups have never been as effective as curbing improper waste disposal from the source. Perhaps educating our young can help reverse the effects. Urbanisation on the Island, and the loss of Penang's free port status have somewhat distanced our connection to the sea; it is not as easily accessible today as it was in the past. The Middle Bank, with its vast blue carbon stocks and potential for marine ecotourism, is a valuable asset to socialise and make accessible for marine education; and if such a programme is well planned, what a legacy this would leave to future generations!

Professor Zulfigar Yasin

is a marine environmental scientist who is an Honourable Professor at Universiti Sains Malaysia and a visiting senior analyst at Penang Institute. His work now focuses on the sustainable development of the marine environment.