Example of Satellite Monitoring of the Impact of El Nino on the Productivity Blooms of Oceanic Phytoplankton

During normal years, when there is a steep thermocline tilt, the cold, deep currents flowing from Antarctica up the west coast of South America are allowed to upwell, bringing essential nutrients that would otherwise lie at the bottom. Phytoplankton living near the surface depend upon these nutrients for survival. In turn, fish and mammals depend upon phytoplankton as the very foundation of the marine food chain. The warm surface waters of an El Niño prevent this upwelling, effectively starving the phytoplankton population there and those animals higher up the food chain that depend upon it. Fishermen in Peru and Ecuador generally suffer heavy losses in their anchovy and sardine industries.

At Christmas Island, as a result of the sea level rise during the 1982-83 El Niño, sea birds abandoned their young and flew out over a wide expanse of ocean in a desperate search for food. Along the coast of Peru during that same time period, 25% of the adult fur seal and sea lion populations starved to death, and all of the pups in both populations died. Similar losses were experienced in many fish populations.

Meanwhile, over a 6-month period, about 100 inches of rainfall fell in Ecuador and northern Peru, ordinarily a desert region. Vegetation thrived and the region grew lush with grasslands and lakes, attracting swarms of grasshoppers and, subsequently, birds and frogs that fed on the grasshoppers. Many fish that had migrated upstream during the coastal flooding became trapped in the drying lakes and were harvested by local residents. Shrimp harvests were also very high in some of the coastal flood regions, but so too was the incidence of malaria cases due to thriving mosquito populations.

The correlation between sea surface temperature and phytoplankton productivity and blooms were well documented by the SeaWiFS satellite around the Galapagos Islands during a transition from El Niño conditions to La Niña conditions in the tropical Pacific Ocean. The images in Figure 6 show an explosion in plankton growth as the warm El Niño waters, blamed for choking off essential ocean nutrients, are replaced by deep cold upwelled waters. The false color images of plankton concentrations between 10 May 1998 and 25 May 1998 show that life in the region to the west of the archipelago has returned in remarkable abundance associated with cooling waters.

The images in Figure 6 are four frames from an animation in http://earthobservatory.nasa.gov/Library/ ElNino/Anim/plankton_sst.mov. The animation shows sea surface temperature across the equatorial Pacific Ocean (top) during the 1997-98 El Niño; the lift-out (four frames in Figure 6) shows a higher-resolution image of ocean color (phytoplankton) in the region surrounding the Galapagos Islands. Notable are the transitions that occur between 10 and 25 May 1998. As the El Niño recedes, surface temperatures cool, allowing colder, nutrient-rich currents to upwell. There is a large, almost immediate bloom of phytoplankton in response to the replenished food source.

Figure 6 This sequence of SeaWiFS ocean color imagery shows the impact of a recent El Niño on the productivity of phytoplankton around the Galapagos Islands in the Pacific Ocean. The left top image (10 May 1998) was taken during the height of the 1997-98 El Nino, while the bottom right image (25 May 1998) was taken during the transition to a La Nina that followed. Note the flourishing bloom of phytoplankton as the surface waters cool, allowing the deeper, more-nutrient-rich waters to upwell. Credit: Adapted from and courtesy of Greg Shirah, NASA/ Goddard Scientific Visualization Studio (http://visibleearth.nasa.gov/view_set.php?categoryID=5227), and the SeaWiFS project.

Figure 6 This sequence of SeaWiFS ocean color imagery shows the impact of a recent El Niño on the productivity of phytoplankton around the Galapagos Islands in the Pacific Ocean. The left top image (10 May 1998) was taken during the height of the 1997-98 El Nino, while the bottom right image (25 May 1998) was taken during the transition to a La Nina that followed. Note the flourishing bloom of phytoplankton as the surface waters cool, allowing the deeper, more-nutrient-rich waters to upwell. Credit: Adapted from and courtesy of Greg Shirah, NASA/ Goddard Scientific Visualization Studio (http://visibleearth.nasa.gov/view_set.php?categoryID=5227), and the SeaWiFS project.

Worm Farming

Worm Farming

Do You Want To Learn More About Green Living That Can Save You Money? Discover How To Create A Worm Farm From Scratch! Recycling has caught on with a more people as the years go by. Well, now theres another way to recycle that may seem unconventional at first, but it can save you money down the road.

Get My Free Ebook


Post a comment