A Stinking Mess
An LA Waterkeeper Blog
Last week a school of fish caused quite a stink in Marina del Rey. Sadly, an entire
school of anchovies ended up in a shallow dead-end basin of the marina, and before they managed to swim out to more open waters, the thousands of fish used up
the available oxygen and suffocated. These mass mortality events are tragic, but not
necessarily a sign of foul play. Much like the mass mortality event that occurred in
King Harbor in March 2011, the cause is likely just a perfect storm of conditions that
lead to a lack of oxygen in the water so extreme it caused fish to die. In this case it
was the recent heat wave, poor circulation in the basin and timing of the large school
of fish that resulted in significant oxygen reduction in the basin and ultimately caused
mortality of the fish. When oxygen levels drop below 2mg/L, waters are considered
hypoxic and fish begin to be stressed.
This is what likely happened late Saturday night on May 17th in Marina del Rey. By
Sunday morning Community Program Manager, Michael Quill, and LA Waterkeeper
volunteers witnessed thousands of dead fish blanketing the basin. LA Waterkeeper, in
collaboration with Marina Harbor, quickly acted to activate volunteers for a cleanup
effort and monitor the dissolved oxygen levels with some help from Dr. John Dorsey
at Loyola Marymount University. In the first couple days after the mortality event we
observed dissolved oxygen levels below those capable of supporting marina life. In
fact, the farthest back corners of the basin the water were anoxic (no oxygen). After
an extensive cleanup of the decaying fish thanks to some awesome LA Waterkeeper
volunteers and the temporary installation of some water circulation pumps, the basin
is now showing signs of recovery from the episode. Dissolved oxygen levels were up
above 2mg/L a week later and most noticeably the smell has subsided.
LA Waterkeeper hopes to continue to work with LMU to monitor and collect data
on dissolved oxygen levels throughout the marina and hopes to better understand the
health of the marina and predict when low oxygen conditions are a risk to fish and
marine life.
By
Lara Meeker