Far north, in the frigid Arctic oceans, scientists uncovered a mystery involving the tiniest of creatures, phytoplankton. However, their physical size as individual organisms is not indicative of their oversized importance in marine ecosystems. These humble little critters are at the base of the marine food chain, the lowest trophic level. The mystery is that their population is growing at rates not predicted by any models.
Phytoplankton are the most important primary producers in the marine food chain because they take sunlight and convert it into food. The rest of the animals higher up the chain depend on this primary production. It is well known that the summer sea ice cover in the Arctic decreased by 40 percent over the past 40 years. The disappearance of sea ice exposed vast areas of open ocean water, providing the Arctic phytoplankton with more direct sunlight for food production. Accordingly, their populations increased by 57 percent in the last two decades.
These observations present no mystery at first look; more solar energy equals more population growth. The mystery is that since 2009 the ice disappearance and ocean exposure has slowed significantly, but the phytoplankton populations continued shooting upward instead of leveling off.
Limiting factors
Ecological studies are not like political discussions where the facts are easily ignored, and irrelevant or blatantly wrong observations become the norm. Ecosystem models are great tools, but when facts contradict the models, then the models are demonstrably wrong and must be reexamined. Predicting how Arctic phytoplankton populations behave requires taking a look at which factors limit growth.
The two critical limiting factors for phytoplankton are sunlight and nutrients. The fact that sunlight availability leveled off but populations continued rising indicates the presence of increasing nutrient supplies. This observation fits with the current knowledge about permafrost melting.
Permafrost forms over centuries and is rich in organic materials. It contains the partially decomposed remains of countless plants and animals. As Arctic temperatures rise, more permafrost melts in the summers, and large quantities of organic nutrients make their way into both surface and underground water systems. As the saying goes, “all rivers flow to the sea,” and in this case to the Arctic sea.
The fact that the Arctic ocean is receiving more nutrients that previously expected may indicate that our permafrost melting estimates are on the low side. Fortunately, this is science, not politics, so that new information influences future research. Unfortunately, government policy is not required to incorporate new facts, and thus ideas proven wrong can continue influencing environmental policy.
ArcheanWeb:
Permafrost: A ticking carbon bomb (Source: ArcheanWeb) – https://archeanweb.com/2020/05/08/permafrost-a-ticking-carbon-bomb/ Also:
Arctic carbon transport via groundwater (Source: ArcheanWeb) – https://archeanweb.com/2020/03/23/arctic-carbon-transport-via-groundwater/ Also:
Sources:
A Major Food Chain Shift Appears to Be Happening in The Arctic Right Now (By Mike McRae; Science Alert) – https://www.sciencealert.com/there-s-a-shift-in-how-the-arctic-locks-up-carbon-and-nobody-knows-what-to-expect Also:
Feature Image:
