Fear Of Uncertainty

La baleine boréale (Balaena mysticetus) | WWF-Canada
Credit: http://www.wwf.ca

You know that everything related to ice, the cold and the deafening silence of the ocean makes me a better person. And so today we will talk about these 3 components and obviously about a majestic living organism: Balaena mysticetus.

This is the only endemic whale in the Arctic and can easily navigate through large areas of sea ice cover. Despite this, they often live in open water habitats. For example, they occur frequently in polynye and along marginal ice areas.

We will talk about the population of Balaena mysticetus of Bering – Chukchi – Beaufort (BCB), also known as the western Arctic population.

Circumpolar commercial exploitation of whales has reduced the species to an extremely low number in the early 20th century. But despite this, the population has undergone an increase for various reasons to date: low anthropogenic mortality, a relatively uncontaminated habitat and a well-managed subsistence hunt that is not such as that of the twentieth century.

Concerns for the population, on the other hand, are now focused on ecosystem disturbances due to climate change and the anthropogenic activities, as a background in this situation.

These concerns underscore the need to delineate the key habitats for the survival and recruitment of these organisms. So we need to start evaluating the ecological effects of climate change perceived by the population, on a temporal and spatial scale. In Arctic marine ecosystems, resources are fragmented and the reduction of sea ice in the western Arctic affects local prey production. But how???

What has been observed in that area is that there have been no dramatic changes in winter ice cover except for a few exceptions (Nunivak island). On the contrary, there is a significant reduction in the coverage of sea ice in the areas suitable for feeding in late summer and autumn. In addition, there is an extreme interannual variability of ice cover as the most alarming feature of climate change.

Due to the reduction of summer and autumn ice, the period of primary and secondary production can be extended. Whales feed on zooplankton produced locally within a foraging area and zooplankton that arrives by advection from other areas.

Sea ice can therefore influence:

  1. the zooplankton production path through the impacts on solar radiation (i.e. the seasonal light cycle) and water stratification
  2. the advective path through the impacts on the dynamics of water flows (ie, currents and upwelling), guided by highly variable atmospheric (wind) forcing.

The variability of sea ice cover has cascading effects of pelagic productivity. Therefore, there are variations in the times and intensity of the phytoplankton bloom if the sea ice regime is variable. The blooms are generally more intense after the stratification of the waters that occurs in late summer, with a flowering peak associated with abnormal heating and early stratification.

With the early melting of the ice there is not only an increase in the phytoplankton but also of the zooplankton that feeds on it. For this reason, to date, Balaena mysticetus does not seem to be limited by food sources.

But in the future it may no longer be favored for 2 reasons:

• primary production may be decoupled from vertical migration of zooplankton

• the increase of free water increases the mixing caused by storms and delays the stratification required for the production of the production peak in the Arctic

And indeed some ecosystem models claim that the decrease in coverage could result in less energy transfer to higher trophic levels. Ultimately, any decoupling of the system that reduces secondary production will have negative effects on higher trophic levels, including Balaena mysticetus.

Here is how a single factor, in this case the melting of the ice, will be able to determine effects on the highest trophic levels, above all on several points of view. For this reason, the migratory patterns of the Balaena mysticetus species, the peaks of primary production and related secondary production will probably change.

Let’s not forget that when this happens, and it is already happening, there will be stratification of the waters that will cause organisms to stay in the upper layers of the water column. This will expose them to solar radiation which can generate genetic changes and will certainly occur faster in plankton organisms such as zooplankton and phytoplankton. These organisms are very important and the basis of the trophic network of any ocean.

We understand that in reality the situation is much more complex than it seems and that the effects can be devastating. But we don’t know, we can’t know, since they are unpredictable. And unpredictability is scary.

Maria Bruno

	© Paul Nicklen/National Geographic Stock / WWF-Canada
Credit: http://www.wwf.ca

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