Question

Draw a diagram that explains the process of upwelling. An area of upwelling exists off of the western coast of South America. During El Niño events, upwelling does not occur and surface water is warm and nutrientpoor. What effect could this change have on the marine organisms in this area?

Short answer

El Niño weakens upwelling, leading to nutrient-poor waters, harming marine life dependent on nutrient availability, starting from phytoplankton.

Step-by-step solution

Define Upwelling

Upwelling is a process where deep, cold, and nutrient-rich water rises to the surface, often due to wind-driven movement of surface water. This process brings nutrient-dense water to the euphotic zone, supporting marine life.

Identify Upwelling Area

An area of regular upwelling exists off the western coast of South America. Here, the trade winds usually blow from east to west, moving warm surface waters away and allowing colder, nutrient-rich waters to rise.

Describe El Niño Effects

During El Niño events, these trade winds weaken or reverse, preventing upwelling. Consequently, the surface water remains warm and nutrient-poor, disrupting the usual availability of nutrients in the surface layer.

Examine Impact on Marine Life

Marine organisms, especially those at the base of the food chain like phytoplankton, depend on nutrients brought by upwelling. Without these nutrients, phytoplankton production declines, affecting the entire food web, including fish and higher predators.

Key concepts

El Niño

El Niño is a complex climate pattern that disrupts normal atmospheric and oceanic conditions in the Pacific region. It occurs every few years and is characterized by the warming of ocean surface temperatures in the central and eastern Pacific. This warming effect has significant impacts on weather and climatic conditions around the globe.

A key feature of El Niño is the weakening or reversal of the trade winds. These winds usually blow from east to west along the equator and drive upwelling. However, during El Niño, the winds diminish, leading to reduced upwelling activities off the coast of South America. The absence of upwelling means the waters remain warm and nutrient-poor.

In essence, when El Niño events take place, the usual replenishment of nutrients in the surface waters is halted, leading to cascading effects on marine life.

marine ecosystem

A marine ecosystem consists of interconnected relationships between organisms living in ocean waters and their surrounding environment. This ecosystem is full of diverse life, ranging from microscopic organisms to massive whales. Marine ecosystems depend heavily on physical and chemical factors, such as temperature, salinity, and nutrient availability.

Upwelling zones, like those found off the coast of South America, play a vital role in maintaining healthy marine ecosystems. These areas are some of the most productive in the world because upwelling brings nutrient-rich waters to the surface. These nutrients feed phytoplankton, forming the foundation of a vibrant food web.

However, when disruptions like El Niño occur, the balance in these ecosystems becomes threatened. Reduced nutrient availability impacts the phytoplankton populations, which, in turn, affects all organisms higher up the food chain.

phytoplankton

Phytoplankton are tiny photosynthetic organisms that float near the ocean surface. Despite their minuscule size, they are vital to marine ecosystems. They perform photosynthesis, using sunlight to convert carbon dioxide and nutrients into organic matter, releasing oxygen into the water.

These organisms form the base of the marine food web. Many marine animals, including small fish and large whales, depend on phytoplankton as a food source. Phytoplankton also play a crucial role in global carbon cycles, helping to regulate carbon dioxide levels in the atmosphere.

During typical upwelling conditions, phytoplankton populations thrive due to the abundant nutrients brought to the surface. However, when El Niño events disrupt upwelling, the lack of nutrients leads to a significant decline in phytoplankton productivity, affecting the entire marine ecosystem.

nutrient cycling

Nutrient cycling is the natural process of moving and transforming essential nutrients within an ecosystem. In the ocean, this process is driven by upwelling, which brings nutrient-rich waters from the deep to the surface layers. These nutrients, such as nitrates and phosphates, are vital for the growth of marine organisms.

When upwelling occurs, nutrients reach the euphotic zone, the sunlit upper layer of the ocean, where most photosynthesis happens. Here, phytoplankton absorb these nutrients to grow and multiply, forming the base of the marine food chain.

The implications of nutrient cycling go beyond just supporting marine life; it is essential for the health of the global ecosystem. Phytoplankton, by using these nutrients, also help in sequestering carbon, aiding in regulating Earth’s climate. Events that disrupt nutrient cycling, like El Niño, thus have far-reaching consequences, affecting both marine biodiversity and global environmental health.