California’s drought, El Niño and aquatic ecology

For the last four years, California has experienced one of the most severe droughts ever recorded. California Gov. Jerry Brown declared a state of emergency in January to prepare for the statewide water shortages and put firm conservation procedures into effect.

According to a study published in the British journal Nature Climate Change, the snowpack in the Sierra Nevada Mountains has decreased to its lowest level in at least 500 years. The resource typically supplies about 30 percent of reservoir water in California in the spring. Normally, there is up to 5 feet of snow in Northern California, but there was no snow and bare ground in April 2015.

Valerie Trout, lead scientist from the University of Arizona's Laboratory of Tree-Ring Research, studied 1,500 trees in California and other trees across the Western U.S. to determine the amount of snow fall for the last 500 hundred years. Trees are unique organisms because they allow scientists to study precipitation and temperature without doing any damage to the organism itself. Blue oak trees were used to determine the amount of precipitation, and a variety of other species were used to determine the temperature.

"The Sierra Mountain snowpack typically supplies about 30% of reservoir water in California."

"Trees are remarkable … they are the best recorder of past climate," Trout said in USA Today

California wildfires caused by severe four-year drought
In 2013, a wildfire in Stanislaus National Forest's canyon in California burned over 257,000 acres and was the third-largest wildfire in the state's history. This summer, Northern California endured the two largest and most destructive wildfires. According to national statistics, over 800,000 acres burned to the ground during the 2015 calendar year. A lack of rain has caused vegetation to dry out, creating a great fuel source for the fire. Dry, hot and windy weather, combined with dry plants and a spark – either through human intent, accident or lightning – can start a wildfire. The drier the conditions, the greater the increase in the intensity and severity of wildfires. The wildfires create massive amounts of ash, woody debris and sediment that move into streams and rivers, which can then contaminate an area's water supply.

"Four years of such parched conditions have predisposed the vegetation to be explosive, and that's not exaggerating — it's explosive," Ken Pimlott, director of the California Department of Forestry and Fire Protection, explained to the Los Angeles Times. "The year hasn't ended yet, and it's comparing right up there with some of the most devastating fire seasons on record."

The consequences of El Niño
Currently, California is grappling with the effects of El Niño. This weather event, first identified by fishermen off the coast of South America, is a type of weather pattern that changes trade winds across the Pacific Ocean. This causes unusual ocean warming and other drastic weather changes in different regions throughout the U.S.

Normally, the Pacific Ocean winds blow steadily from east to west, pushing warm water toward Indonesia and Australia on the western edge. According to data collected by the National Oceanic and Atmospheric Administration, these winds are so strong that they are able to push sea levels upward 5 feet near Indonesia compared to Ecuador. While the easterly winds move the water in the Pacific Ocean toward Asia, the colder water rises off the South American coastline, bringing with it colder temperatures and high concentrations of nutrients that benefit marine ecosystems.

The Sierra Nevada snowpack is crucial to California's aquatic ecology. The Sierra Nevada snowpack is crucial to California's aquatic ecology.

El Niño events typically occur yearly. However, the last strong El Niño took place over 15 years ago. During El Niño, the winds slow down, causing the ocean currents to stop or in some severe cases, reverse their flow across the Pacific. The colder water does not rise to the surface, carrying the rich nutrients needed by the marine ecosystems, and the water temperature in the Pacific continues to rise. These effects typically cause drought in parts of Asia and Australia as well as severe flooding in parts of the southwest U.S.

Due to the severe drought that California has had in the last four years, the water that seeps into the ground makes the soil very loose because there is no longer vegetation holding it in place. This has created many mudslides and dangerous levels of toxic materials entering lakes, ponds and streams. Zooplankton and other small organisms are in danger of bio-magnification, which can result in significant problems for organisms at higher trophic levels. Water quality laboratories in California need to not only monitor the levels of water, but also water quality throughout the duration of El Niño.

Marine ecosystems greatly rely on the nutrients that the trade winds carry from the southern tip of South America. The decrease in nutrients and an increase in the water temperature will change the reproduction and feeding relationships in many food chains. The effects of El Niño will also impact the fisheries and the amount of fish available during the upcoming year.