Polar Ecology in Flux Due to Climate Change

Glacial melting and rising ocean temperatures are affecting the feeding, breeding and dispersion patterns of species, such as krill, cod, seals and  polar bears, in the polar regions, according to two recently published research articles. This climatic shift could create an imbalance in the regional ecology and negatively impact numerous species as the effects of climate change worsen.

The first article reflects on how a threat to a key species in Antarctica may shake up the food chain, while the other considers how a changing habitat in the Arctic could skew the population trends of several interconnected species and create a systemic imbalance in the ecosystem.

Glacier-originated melt-water creek carrying large amounts of particles. (Source: V. Fuentes/Nature)

After a nine-year study of krill in Potters Cove, a small section of King George Island off the coast of Antarctica, a team of South American and European marine biologists published their research this past June in the scientific journal Nature.

Krill are shrimp-like sea creatures that feed mostly on plankton.  Since they extract their food from the water by filtering it through fine combs, they are known as filter feeders.  Krill are found in all oceans and are an abundant food source for many marine organisms.  In the polar regions, predators such as whales often rely on krill as their only consistent food source.

The authors of this first piece found that a destruction of the krill population could extend undermine the Antarctic food web that relies on the presence of the small creatures.

 The study launched after stacks of dead krill washed ashore at Potters Cove in 2002, lining the coast. The article’s nine authors, Verónica Fuentes, Gastón Alurralde, Bettina Meyer, Gastón E. Aguirre, Antonio Canepa, Anne-Cathrin Wölfl, H. Christian Hass, Gabriela N. Williams and Irene R. Schloss, suggest the first observed  and subsequent stranding incidents are connected to large volumes of particulate matter dumped into the ocean by melting glaciers. The high level of tiny rock particles carried by the glacial melt water may have clogged the digestive system of filter feeders like krill.

The researchers conducted a series of experiments in which they exposed captive krill to water with varying amounts of particulates. The krill’s feeding, nutrient absorption and general performance were all significantly inhibited after 24 hours of exposure to concentrations of particles similar to those found in the plums of glacial runoff.

Stranded krill along the southern shore of Potters Cove, King George Island (Source: V. Fuentes/Nature).

Although krill are mobile creatures and can usually avoid harmful environments, exposure to the highly concentrated particles interfered with their ability to absorb nutrients from their food.  The krill became weak, which resulted in their inability to fight local ocean currents and their subsequent demise.

About 90 percent of King George Island is covered in glaciers that are melting and discharging particles into the surrounding marine ecosystem, according to the article.  Similarly, an overwhelming majority of the 244 glacier fronts, a location where a glacier meets the sea, studied on the West Antarctic Peninsula have retreated over the last several decades, which suggests that high particulate count from glacial meltwater may be occurring in other parts of Antarctica.

Since much of the Antarctic coast is not monitored and most dead krill sink to the bottom of the ocean, the authors caution that these stranding events likely represent a small fraction of the episodes.  

In another recent study on climate change’s impacts on wildlife, scientific researchers with the Norwegian Polar Institute focus their attention on the high Arctic archipelago of Svalbard, Norway.  They found that glacial melting and changes in sea ice have impacted numerous land and sea animals in the Arctic. These shifts have the potential to influence more creatures. The study, by Sebastien Descamps and his coauthors, was published this May in the scientific journal Global Change Biology.

Tidewater glacier in Greenland, taken from helicopter (Source: Brocken Inaglory/CC)

Some species, such as the pink-footed goose, are benefiting from the warming Arctic climate, however. Lower levels of spring snow cover and earlier melting has expanded the time for its breeding and the area of available breeding grounds, which will likely lead to an increase in the geese population.  

However, the success or the overpopulation of one species can cause an imbalance in the ecosystem and negatively affect numerous other organisms.  As the authors explain, “An extreme increase in a herbivore population [like the geese] has the potential to affect the state of Svalbard’s vegetation substantially, with possible cascading consequences for other herbivorous species and their associated predators.”

The authors conclude, “even though a few species are benefiting from a warming climate, most Arctic endemic species in Svalbard are experiencing negative consequences induced by the warming environment.”

Polar bears and the Arctic ringed seal are among the species which are suffering the impacts of a warming Arctic.  Seals breed on sea ice and depend on snow accumulation on the ice in order to form lairs for their pups.  The snow lairs provide protection from the harsh winter and predators.  As ocean temperature warms and the season of sea ice formation shortens, there is less time for accumulation of snow.  Thus, many seals are giving birth on bare ice, which leads to a much higher pup mortality rate.

Weddell seals (Source: changehali/CC).

This  article also points out that tidewater glaciers have become increasingly important foraging areas for several species, including seals, seabirds and whales.  Additionally, these creatures’ presence makes the glacier fronts fruitful hunting grounds for polar bears. Icebergs drifting near the glacier fronts create valuable resting areas in the hunting grounds for many of these animals.

The authors hypothesize that the increase in icebergs calved from the glacier fronts could counterbalance the ecological loss resulting from the disappearance of sea ice. Yet this may only offer a brief reprieve for the Arctic species that depend on the ice.  

“Continued warming is expected to reduce the number of tidewater glaciers and also the overall length of calving fronts around the Svalbard Archipelago.  Thus, these important foraging hotspots for Svalbard’s marine mammals and seabirds will gradually become fewer and will likely eventually disappear,” wrote the authors.

Taken together, these two recent articles show that glacier retreat, as well as other forms of loss of ice, have negative impacts on high-latitude ecosystems, both in the Arctic or in Antarctica. There are strong similarities between these two cases, distant from each other in spatial terms but close to each other in their shared vulnerabilities.

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