Flooding in the Oceans?
Floods in the ocean may sound like an oxymoron, but the truth is that many marine habitats are highly sensitive to fluctuations in water levels and the changes they bring. Today, we are seeing a tragic example of this in Australia's Great Barrier Reef, the world's largest reef system. The torrential rains that have been pummeling Australia this year bring many unwanted gifts to the nation's waters and reefs. Flooded freshwater rivers carry extra freshwater out to sea, creating a shift in the salinity of the Great Barrier Reef's waters. Species like coral, shellfish, and others are highly sensitive to changes in their environments, and even a small decrease in the ratio of salt can have devastating impacts. These rivers also bring with them many fertilizers, pesticides, and sediment flushed out by rainwater, and each carries a different threat for the reef: Fertilizers stimulate the growth of marine plants like algae and seaweed, which chokes corals and other native species. At the same time, foreign chemicals from pesticides can be toxic to sensitive marine plants and animals. And while sediment may be "natural" compared to fertilizers and pesticides, too much can muddy ocean waters and block sunlight from the corals, plants, and other species that thrive in shallow ocean waters and depend heavily on adequate lighting. Ocean currents carry river effluents far and wide, so even waters in southeast Australia make their way up to the Great Barrier Reef.
To make matters worse, coral reefs are in no condition to bear these challenges. While a robust reef might be able to weather them with relatively little long-term effects, the world's reefs today are already debilitated by climate change, ocean acidification, pollution, overfishing, and other threats. Adding floods to the mix may put them over the edge. As global warming continues to bring more extreme weather, such as the flooding Australia is currently experiencing, the Great Barrier Reef and other marine ecosystems will be on increasingly fragile territory.
Above, an aerial view of the Great Barrier Reef, the largest thing on earth created by living organisms. Picture courtesy of Wikimedia Commons.