Deepwater Horizon Disaster
In April 2010, approximately 210 million gallons of oil was released into the Gulf of Mexico marine environment following the Deepwater Horizon oil spill. In response, over 2 million gallons of oil dispersant was released, in unprecedented quantities and untested ways in an effort to break up and sink the oil.
In July 2010, Ocean Alliance, in partnership with the Wise Laboratory of Environmental and Genetic Toxicology, took the RV Odyssey into the area in an effort to determine the, often over-looked, long-term impacts of this environmental catastrophe. After such incidents, people often look no further than the immediate impact: death tolls of particular species are logged, population declines/increases recorded, and these figures are seen as broadly representative of the environmental damage. The toxicological work being conducted by Ocean Alliance and our partners at the Wise Lab was primarily aimed at determining the chronic, long-term impact of the incident-in particular the geno-toxic impacts of oil (and compounds found in oil) and dispersants as they work their way up the trophic food chain. The long-term effects are believed by many to be far more significant than the short-term effects, a belief corroborated by on-going research in the Gulf of Mexico and the fact that the impacts of the Exxon Valdez spill (which occurred in 1985 in Prince William Sound, Alaska) are still being studied over 25 years after the initial accident. In terms of total discharge of oil, this spill was approximately one tenth of the Deepwater Horizon spill. Perhaps the most significant economic impact of the Exxon Valdez disaster-the collapse of the herring fishery, only collapsed four years after the spill, and to this day is not showing signs of recovery. This makes the kind of long-term focused program Ocean Alliance conducted all the more important. Preliminary analysis has shown potentially damaging levels of genotoxic metals including chromium and nickel in sperm whales living in the area, significantly higher than the global average. Furthermore, it has shown a correlation between proximity to the spill and levels of these genotoxic metals.
To achieve this aim of conducting a long-term analysis, Ocean Alliance monitored the top apex predator of the region, the Sperm whales. A resident, non-migratory population of Sperm whales resides in the Northern Gulf of Mexico in close proximity to the Deepwater Horizon oil spill. As apex predators, Sperm whales act as bio indicators of the health of the marine ecosystem in a toxicological context, demonstrating the effects of three key processes: bioaccumulation, biomagnification and the generation effect. Sadly these processes also make Sperm whales, and other apex predators, at greater risk from toxic pollution. Significantly, the data which was collected could be placed into the global data-set acquired during The Voyage of the Odyssey program.
Ocean Alliance conducted this study for 5 years, during each summer from 2010 to 2014. For the final two years, they were joined by activist group the Sea Shepherd Conservation Society, as part of a program labelled Operation Toxic Gulf. This afforded the program much more exposure than was previously possible.
How do you find a sperm whale?
Sperm whales are massive animals. They can measure up to 70 feet in length and can weigh over 100,000 pounds! Yet the Gulf of Mexico is a massive area. Searching for a 70-foot-long animal in a body of water larger than Texas, California, Florida and New England combined is very much like looking for a needle in a haystack.
Unless you know where to look. Or perhaps more accurately, where to listen.
Sperm whales are amongst the loudest animals on the planet. The clicks they use to locate food can be as loud as 230 decibels underwater. As a comparison, a thunderclap is 120 decibels and a jet plane taking off is 150 decibels. So when you want to find sperm whales, the secret is to use sound, not sight. On a calm day, these loud clicks can be heard up 20 kilometres away. On-board the Odyssey, the Ocean Alliance team dragged an acoustic array, a 300-foot long line with multiple hydrophones (underwater microphones) behind the boat. Because this acoustic array had more than one hydrophone, the Ocean Alliance team could work out an approximate location for the whale by triangulating its position.
A second way of finding sperm whales is to look at topographical maps of the seafloor. Sperm whales primarily like to feed in deep water where there are large aggregations of squid. In turn, the squid are there to feed on their own prey. What drives the presence of the squids prey is nutrients in the water. Deepwater canyons and cliffs often cause
When deepwater currents, which tend to carry lots of nutrients, hit underwater canyons, cliffs and seamounts they push up, bringing the nutrients into shallower waters. This creates an increase in small fish and other organisms, which in turn feed the squid, which in turn feed the sperm whales. So when looking for sperm whales, it can help to look for dramatic features on the seabed where waters quickly go from very deep to very shallow.