Artificial Reefs, revisited…

Photograph by David Doubilet, National Geographic

Well I finally picked up a copy of the this month’s National Geographic with the artificial reef article in it. And by picked up I mean borrowed from a waiting room, but I have to go back on Thursday and will return it then, so I am no thief.  Anyway, I briefly blogged about this article already when I was depressed about winter weather and longing to be someplace else, preferably warm, and diving.  That’s because I love diving.  And sometimes, there’s nothing better than diving on wrecks.  Sometimes.  Don’t get me wrong, there is plenty of cool things to see on naturally occurring bottom.  But artificial reefs created by wrecks are definitely very cool (so is this video).

Image from Pangea-yep.com

But actually reading the article, in print, and seeing the pictures, made me want to blog about it all over again.  This time, though, I will concentrate a little more on artificial reefs themselves. Artificial reefs are quite simply structures artificially sunk by man to create a hard bottom in an otherwise sandy and structure-less habitat.  The idea is to mimic some of the functions of naturally occurring reefs – namely, by providing a hard, 3-dimensional structure that sits in the water column.  These reefs are intended to attract and enhance many marine species, in particular, finfish.    In fact, fisherman have been sinking things for decades (probably even centuries) to attract fish, so this is not a particularly novel idea.  However, the number and magnitude of  artificial reefs has certainly expanded greatly in recent years (Edit – as Dr Alan Dove pointed out in the comments below, there have been numerous “natural” or unintentional wrecks sunk over the years.  So the rate of sinking artificial reefs might not have increased, but I imagine the rate of intentionally sunk reefs has).  Typically, “Artificial reefs” just consisted of junk.  Now, many have expanded to be large decommissioned ships, subway cars, and oil rigs (and other cool things).  And even more recently, companies are creating artificial reefs from concrete, such as Reef Balls, which I think are pretty cool (and, if you are lucky, when you die, you can be commemorated for eternity as an artificial reef ball! Sign me up!).

It might not happen over night, but eventually these sunken structures become teeming with life.  Swirling currents around these structures can kick up and contain plankton, which attracts small planktivorous fish.  These little guys, in turn, attract larger piscivorous fish.  In addition to seeking food, many fish arrive simply to seek shelter in the many nooks and crannies that artificial reefs provide.  But its not just fish.  The artificial structures also become colonized by invertebrates and macroalgae, creating a crusty layer of living organisms growing as a living shell of sorts on the submerged structure.  This living structure offers more nooks and crannies for smaller creatures, and provides food for numerous species that inhabit the reef.  It essentially becomes just like a natural, living reef, with the only difference being that the underlying structure is man-made.  Typically, when we think of artificial reefs, we think of tropical locations.  However, they are also used in many temperate coastal waters to enhance fisheries, including Maryland,  South Carolina and New Jersey.  Here, they create ecosystem structure typically only present on the few limestone rocky outcroppings that stick out of the sand bottoms.

Despite providing food and shelter to numerous species, there are certainly detractors, and artificial reefs aren’t without certain cons.  One major concern is that some things are just tossed in the ocean as junk, but that companies/organizations/municipalities/entities use the “artificial reef” moniker as an excuse to dump crap.   Its cheaper to just toss things into the water than dispose on land, and so sometimes, things are called reefs just as an excuse.  That is bad.  Additionally, many things that are sunk have toxic substances on them, which can actually do more harm to the environment, leaking contaminants for the life of the reef.  It is for these reasons that there are now strict, stringent regulations for sinking artificial reefs.

But one of the biggest complaints against artificial reefs is the very reason they are created in the first place – they concentrate fish.  The complaint is that these concentrations make fish easier targets for fishermen, and can be potentially harmful to specific species.  According to the NatGeo article, some biologists believe that this artificial enhancement of certain fishes, can be extremely detrimental to stocks.  One such fish that is likely being negatively impacted by artificial reef structures is the red snapper, which concentrate around the structures and become easy targets for fishermen.  In other words, these artificial reefs might make fishing as easy as shooting fish in a barrel.  Obviously, acting as fish attractants with easy access can be harmful to fish populations, and some might argue that recreational fishermen are quite capable of decimating fish stocks, even in the absence of commercial fishing pressure

Clearly there are pros and cons of artificial reefs.  However, it is my opinion that the pros outweigh the cons.  And an easy way to eliminate the major negative impact of artificial reefs – the potential to overfish exploited stocks due to large congregations of target species around these structures – is to incorporate reefs into marine reserves and no-take zones.  Yes, this might defeat the purpose of the reefs, and many will argue against this.  I am not suggesting all artificial reefs become no take zones, but by leaving some as no take refuges, the reefs could serve there original purposes.  While there is some debate as to the usefulness of marine reserves on highly mobile species, it stands to reason that artificial reefs create habitat where there is otherwise none, and enhances the local ecology of the area of the reef, enhancing species abundance and diversity.  Plus, they are just awesome to dive on.