The overpowering stench was the first thing that scientists encountered when responding to a fish kill alert at California's Redondo Beach early on March 8, 2011. More than two million sardines - that's 175 tons - suddenly perished and floated to the surface of King Harbor that morning and over the next few days, echoing previous fish die-offs that occurred in the same waters in 2003 and 2005. But unlike those previous fish kills, this time the scientists were prepared.
Redondo Beach is more than just a mecca for surfers and sunbathers, it has also become the home of an innovative water quality monitoring system called the
EcoMapper. Affectionately known as "Boomer," the city's EcoMapper is no ordinary piece of monitoring equipment. It is a self-propelled autonomous underwater vehicle (AUV) equipped with sensors that continuously measure temperature, salinity, dissolved oxygen, chlorophyll, and algal pigments in the water column. Quietly patrolling the depths of King Harbor, the EcoMapper keeps scientists updated with real-time water quality information every 30 minutes without anyone getting their feet wet.
Fish kills often occur when the algae population rises dramatically due to a sudden increase in available nutrients. This algal bloom can cause a rapid depletion of oxygen in the water column, effectively suffocating fish and other aquatic life. When an algal bloom triggered massive fish kills in King Harbor in 2003 and 2005, city officials and University of Southern California (USC) scientists decided that they needed to ramp up their efforts to protect the harbor and its vulnerable aquatic life. In 2006, USC researchers started taking weekly water samples and the next year, deployed the
YSI EcoMapper as part of a long term study aimed at understanding and predicting algal bloom events. The EcoMapper's ability to simultaneously map the ocean floor and collect real-time water quality data makes it an incredibly useful tool, since it enables scientists to see a detailed view of the entire physical and chemical make-up of the marina.
USC lead researcher, David Caron, and his team have been compiling and analyzing data collected by the EcoMapper, an instrument they say has allowed them to gain an unprecedented glimpse into how a fish kill event of this magnitude occurs. "This allows us to have a finger on the pulse of what's going on out there," Caron says. The light-weight, torpedo-shaped EcoMapper can easily be deployed by just one person, and can be fitted with multiple sensors that can collect up to 10 water quality parameters. Its ability to produce high-resolution maps of water quality while on the move makes it a uniquely valuable instrument for tracking the movement of "dead zones," or plumes of oxygen-depleted water, as well as toxic algal blooms -- which can result in serious public health concerns.
With Boomer's help, Caron and his research team hope to predict and possibly even prevent events like this in King Harbor. This would not only help safeguard the health of the marina's aquatic life, it could potentially save the city of Redondo Beach hundreds of thousands of dollars in fish kill clean-up costs. Already, the city of Redondo Beach has been able to investigate the possibility of installing an oxygenation system at the harbor, which could be used when algal biomass levels start to rise to dangerous levels.
Predicting the occurrence of harmful algal blooms would also enable city officials to issue more effective public warnings. With the EcoMapper in place, Redondo Beach residents and tourists can rest assured that they have a vigilant guardian keeping round-the-clock watch on the health of their harbor.