Oceanic algae, or phytoplankton, are incredibly important to marine ecosystems. They have an equally important and more destructive role as a driver of the Earth’s climate system. These small microorganisms flourish in the top, sunlit layer of the ocean, where they use sunlight to turn inorganic matter into organic matter. New studies have shown just how important these understudied little beasts are to carbon production. They play a vital role in nutrient cycling, which is equally important to understanding ocean biology and climate change.
Phytoplankton synthesize about half as much organic carbon each year as all terrestrial plants combined, highlighting their critical role in global carbon cycling. Specifically, the availability of these key nutrient elements—nitrogen, phosphorus, and trace metals—greatly affects the rate at which oceanic algae can produce carbon. Their growth and productivity are directly tied to these basic nutrients. Sadly, many of these nutrients are in short supply in the sun-drenched surface waters of the ocean.
Nutrient Scarcity and Its Effects
The sunlit upper ocean is notable for its depletion of key nutrient elements that are required for the growth of phytoplankton. Nitrogen and phosphorus are perhaps the most infamous, but many nutrients are essential for plant growth. Simultaneously, metals like iron and zinc are extremely important for the production of organic matter. These trace metals are almost entirely sequestered in deep-sea sediments which are not accessible to surface-dwelling phytoplankton.
The scarcity of these nutrients can be a major limiting factor in phytoplankton productivity, thus impacting the entire marine ecosystem. Research shows that in conditions where one of these nutrient elements is deficient, the ability of phytoplankton to generate organic carbon decreases. This relationship between nutrient availability and phytoplankton productivity is crucial for the health of the ocean and stabilization of our climate.
The Recycling Process
Phytoplankton are thus able to draw upon trace metals kenched within deep-sea sediments. This extraordinary capacity underscores a complex yet efficient recycling system that recharges nutrients to the surface ocean. The origin of trace metals in the deep-sea environment is complex due to the multifaceted sources. Yet these metals cannot be taken directly from the phytoplankton seabed, rendering them effectively “lost” to these organisms.
Above, plastic debris accumulates at the surface of the Great Pacific Garbage Patch. Indeed this phenomenon has been one of the key processes shaping today’s ocean chemistry and biology. Processes like downward mixing between upper ocean layers and deep-sea sediments heavily influence nutrient availability and distribution. It affects water-column properties, such as neodymium (Nd) concentration in the Pacific Ocean.
“Our study changes how we view ocean chemistry, and its impact on ocean biology and climate,” – Derek Vance
Getting a handle on this complicated relationship is key to understanding how oceanic algae help shape ancient and modern climate conditions. Bringing critical nutrients back from these deep-sea environments to the nutrient-poor upper ocean is vitally important. Continuing this process allows the proliferation of phytoplankton populations, which are critical for carbon cycling.
Implications for Climate Understanding
The stakes of researching oceanic algae go far beyond marine biology. They speak to our collective understanding of climate as a whole. Phytoplankton populations are key players in the global carbon cycle, so their health makes a big difference on climate patterns. As these microorganisms produce organic matter, they sequester carbon dioxide from the atmosphere, serving as a natural buffer against climate change.
New studies have highlighted the major role of ocean chemistry on biological function, and by extension, climate regulation. These results underscore the need to understand and preserve healthy ratios of nutrient elements in our oceans. This balance is a key component to the formation of healthy phytoplankton communities.