Overfishing is already a considerable issue, with a number of species having been fished to the brink of extinction. Tuna in particular has been hard hit, but a number of sharks are also threatened due to shark finning. A growing world population, particularly in Southeast Asia and living near the coastlines, depends on fishing for their sustenance. Ever more efficient fishing techniques in the industrialized world will only exacerbate this problem. Divers have seen a marked decline in marine wildlife at a number of popular dive sites, and not just of the species that are fished commercially. Bycatch, the catching of fish not intended for commercial use, means that more species are overfished than the ones we see at the supermarket, and the disruption of multiple food chains also contributes to the depletion of reef life.
Global warming has a number of negative consequences for the oceans. First and foremost it warms the water, which creates a shift in the temperate zones, meaning species that used to thrive only near the equator move further north and south. Second, it leads to coral bleaching and death, as corals are quite sensitive to temperature fluctuations. This will also have a profound negative effect on the marine wildlife we’ll be able to see on these reefs, as the corals themselves are an integral part of the ecosystem. And third, global warming leads to ocean acidification, wherein the acid levels of the ocean waters increase, making it more difficult for a number of species to survive.
Invasive species have become a problem during the 20th century, both on land and at sea. Temperature shifts due to global warming (see above) play a large role. As the ocean’s waters become warmer, animals such as Humboldt squid and a number of other high-level predators are able to expand their territories to places where they have few or no natural predators. Their populations quickly increase beyond what is healthy for the local ecosystem, causing local species to disappear. Invasive species can also hitch rides on man-made transport vessels, such as cargo ships. When these ships take on ballast water in one part of the world, and release it in another, a number of smaller animals, fish eggs, and other representatives of foreign species can be quite effectively moved from one part of the world to another. One example of this is the lionfish, which has become a huge problem in the Caribbean. The lionfish is indigenous to Southeast Asia, the Indian Ocean, and the Red Sea, and may have been introduced to the Caribbean by cargo freighters.
This section could more simply be called “Plastic,” or even “Non-Biodegradable Waste.” Anyone who has read anything about the Great Pacific Garbage Patch has a very real idea of what happens when human waste deliberately or accidentally ends up in the ocean. We highlight plastic bags here because they make up the bulk of our non-biodegradable waste, and pose a separate threat to a number of animals, not least to turtles. Many species of turtles feed on jellyfish, and a clear plastic grocery bag floating in the water looks a lot like a jellyfish. When a turtle tries to eat it, he chokes on it and dies. Better waste management and a ban on plastic bags near shorelines, as a number of communities around the world have imposed, are obvious ways to address this problem.
Yes, you. Every individual on the planet can do something about all of the above. The classic triad of “reduce, reuse, recycle” can have profound effects on the ocean’s problems. But as a diver, we can do even more. We can go where few others can go, and see what others don’t. We see the effect of poor waste management and sloppiness; we see the coral bleaching that is a result of global warming and pollution; we notice the drop in wildlife on popular reefs. In that sense, we have a power that few others have. And, as Peter “Spiderman” Parker’s late uncle Ben said, “with great power comes great responsibility.” I try to inspire all the divers I train to take action, in some small way, every time they dive, trying to solve the oceans’ problems one step at a time. Pick up a bit of trash every time you dive. Report a suspected invasive species to the proper authorities. Report erosion or other changes to a dive site to the proper authorities. And tell people about what you see, both the good and the bad. Share your stories and concerns, and inspire non-divers to care and take action. If each and every one of us took just small action every day, we could change everything.