Brunei is one of the best places outside of the U.S. for wreck diving. While dive magazines (variably reliable) rarely mention this small equatorial nation, I’ve been pleasantly surprised at the abundance and diversity of marine life in the South China Sea. On top of the sea snakes, cuttlefish, and nudibranchs – or, rather, under them – there lie over a dozen shipwrecks from the turn of the century on. As far as I can tell, most of them were sunk during World War II; don’t get me started about the ghost stories.
Wreck diving has a loyal following, often attracting the treasure hunters and historians within the diving community. Technical or “Tec” diving is a growing division of the dive industry that trains advanced divers to use more complicated gear (ReBreathers, TriMix, Sidemounts) to do deeper, longer. I’ve had a few conversations with inebriated divers (not in dry Brunei, obviously) who virtually grab my collar and loudly whisper about a yet-unpenetrated wreck and the booty within. I’m more interested in the contemporary ecological and political functions of these manmade structures at 20 meters or more.
Shipwrecks have been recognized as prime fishing sites since at least the 1830s when American fishermen built artificial reefs out of interlaced logs. Japanese fishermen (as we’ll get into later this year) built their own personal structures to supplement offshore catches. We throw so much stuff into the ocean that you could call anything from a car to a crane an “artificial reef.” As Harrigan notes for NatGeo, “Even officially sanctioned ones are often created from distinctly odd materials, including decommissioned subway cars, vintage battle tanks, armored personnel carriers, oil drilling rigs, and specially designed beehive-like modules called Reef Balls.” Shipwrecks and their production value served as a model for the early years of alternate material use in the history of artificial reefs (which can have disastrous consequences).
Harrigan goes on to explain the ecological function of sunken ships, which “can create a plankton-rich upwelling that provides a reliable feeding spot” for smaller fish, upon which an entire food web rests. Structurally, the holes and crevices provided by wrecks encourage the shier fish like like groupers, snapper, squirrelfish, eels, and triggerfish. Opportunistic predators, Harrigan notes, wait in the water column for their prey that call the wreck home. Finally, they can act as substrate for hard and soft corals.
Understanding this ecological capacity of wrecks, it becomes easier for governments and companies to justify the intentional sinking of wrecks. Wrecks serve as artificial reefs as well as a diver training sites – they’re great for deep diving and protecting natural reefs from klutzy divers. (I think it’s a little weird to prioritize natural or artificial coral this way, but…) They can provide commercial revenue as dive attractions. The US will sink pretty much anything – check out Florida. So why don’t we just call these ships junk? What’s the difference between dumping and decommissioning?
Statistical likelihood of success, first of all. Researchers in China (Wang et al. 2014) emphasize that something is better than nothing, and that artificial structures better regulate fish community structure than a patch of sand. But researchers emphasize how man-made wrecks specifically alter those community structures. Walker and Schlacher (2013) assessed the growth on a 133m battleship after three years and found that, while cover was similar to natural conditions, invertebrate ecology was “fundamentally different” on these young reefs. There was no large coral growth. They emphasize how there’s a significant “temporal lag” on artificial reefs before they function as natural reefs do.Fowler and Booth (2012) report that fish community structure on wrecks is, at its core, significantly different from local natural reefs, and that wreck size enables proportionally higher fish abundance. I’ll be using Walker and Schlacher’s standards as I do my own assessment of the Oil Rig Wreck here in Brunei.
Embedded in the success of these artificial reefs, wrecks or not, is intent. We sink these ships with a lot of human baggage: Wrecks pay homage to particular moments in history, intentionally sunk or not. They participate in narratives of exploration, mystery, and danger embedded in diving. They’re also a convenient way to get rid of decommissioned train cars, helicopters and oil rigs. So, secondly, we have to think about design as intention, and the way that design impacts the success of these conservation projects as much as our sense of self-worth. This is no clearer than in the Rigs to Reef program – good thing it’s what we’ll be focussing on for a month.
Walker, SJ and TA Schlacher. 2014. Limited habitat and conservation value of a young artificial reef. Biodiversity and Conservation. 23(2): 433-447.
Zhenhua W, C Yong, Z Shouyu, W Kai, Jing Zhao, X Qiang. 2015. A comparative study of fish assemblages near aquaculture, artificial and natural habitats. Journal of Ocean University of China.14(1):149-160.
Fowler, AM and D. J. Booth. 2012. How well do sunken vessels approximate fish assemblages on coral reefs? Conservation implications of vessel-reef deployments. Marine Biology.159(12): 2787-2796.