New to science: studying microscopic life in the Polar Regions

Life in the Polar Regions is harsh: during the summer season, organisms experience continuous sunlight, combined with relatively high levels of ultraviolet radiation, whereas during the winter temperatures permanently drop (far) below 0 °C and there is no sunlight for months on end. Consequently, the number of macroscopic plant and animal species living in the Polar Regions is small compared to the rest of the planet. Nevertheless, the Polar Regions harbour a huge diversity of microscopically small life.

One of the most abundant groups of microscopic life worldwide, including the Polar Regions, are the diatoms. Diatoms are a group of unicellular algae that live in a cell wall made of ‘silica’, which is literally ‘a glass house’. This cell wall consists of two halves (the valves) which perfectly fit in each other, much like a box of Camembert cheese. When observed through a microscope, the glass house of diatoms appear as very beautiful, finely ornamented structures. When alive, diatoms have a yellow brownish colour. In the Polar Regions, diatoms can be found living in the sea, lakes or even terrestrial environments, such as soils and mosses. Diatoms live floating in the water column or attached to substrates such as sand grains, rocks, plants or sea ice. They often occur with millions of individuals together.

Diatoms are not only beautiful little creatures, they are also the base of the global foodweb and account for about 20% of the oxygen production on a global scale. Imagine: every fifth of your breaths is entirely produced by these tiny little algae! Diatoms can be found on all continents and climate zones: from tropical Africa to Antarctica. Nevertheless, the diversity of diatoms in the Polar Regions, especially in the High Arctic, is not well studied. Whenever scientists take new samples, they are bound to find new species that were never seen or recognized before!

A couple of years ago, I had the chance to travel to the High Arctic archipelago of Svalbard to study diatoms. After microscopically analysing more than 80 different samples taken from freshwater lakes and ponds, I found more than 300 different species. About 100 of these could not be identified using the existing literature, suggesting they represented new species unknown to science. Identifying a microscopically small algae as a new species is not easy though. Usually, these decisions are based on the cell wall: a new species needs to have a unique morphology (i.e. it has to look different than all other species). In order to know this, you need to assess the complete literature, which often involves digging through books written in the 19th century. When knowing that scientists have already described more than 25,000 different diatom species in the past two centuries, it is easy to imagine that this takes a lot of time, and a good photographic memory!

Picture1
Figure showing several light microscopic pictures of diatom species from Svalbard (High Arctic). Scale bar= 10 µm.

For now, three new species were described based on the samples taken in this study. When scientists describe a new species, they can decide on how to name it. Each organism, whether it is a plant, an animal or an algae, has a scientific name (in Latin) consisting of two parts: the first part is the genus name, the second part is the species name. For humans, the scientific name is Homo sapiens: genus Homo, species sapiens. In most cases, scientists use an already existing genus name to pinpoint similarity with already described species. For the species name, however, they can be very creative, naming species to the region where they were found, their morphology or even after a person. In my diatom study, I named one species after the Svalbard Archipelago: Gomphonema svalbardense. Another one was named after the region in which I discovered it, Petuniabukta: Achnanthidium petuniabuktianum. At last, a third species was named Achnanthidium digitatum, since it slightly resembles a finger (digitus in Latin).

Picture2
Light microscopic (Figs 1-13) and scanning electron microscopic pictures (Fig. 14) showing the valves of a diatom species inhabiting the High Arctic: Gomphonema svalbardense. Fig. Fig. 1 shows two valves attached to each other, as seen from the side. Figs 2-14 show the morphological variation in the valves as seen from above. Scale bar = 10µm.

Many of the diatom species that are found in the Polar Regions seem to be specifically adapted to living there and, in many cases, have never been found outside the Polar Regions. In an age of climate change, environmental pressures on the High Arctic and Antarctic Regions are continuously rising. It is clear that many organisms, the most famous example being the Polar Bear, have trouble adapting to their warming environment and are consequently facing extinction. It is as of yet still unclear, however, how microscopic life, such as polar diatoms, will fare in a warmer world. We can only hope that the future will be bright for the Arctic and Antarctic, so that we do not lose those jewels of the cold, big or small.

Written by Eveline Pinseel

References:

Pinseel E., Vanormelingen P., Hamilton, P.B., Vyverman W., Van de Vijver B. & Kopalová K. (2017) Molecular and morphological characterization of the Achnanthidium minutissimum complex (Bacillariophyta) in Petuniabukta (Spitsbergen, High Arctic) including the description of A. digitatum sp. nov. European Journal of Phycology 52: 264–280. doi: 10.1080/09670262.2017.1283540

Pinseel E., Van de Vijver B., Kavan J., Verleyen E. & Kopalová K. (2017) Diversity, ecology and community structure of the freshwater littoral diatom flora from Petuniabukta (Spitsbergen). Polar Biology 40: 533–551. doi: 10.1007/s00300-016-1976-0

Pinseel E., Van de Vijver B. & Kopalová K. (2015) Achnanthidium petuniabuktianum sp. nov. (Achnanthidiaceae, Bacillariophyta), a new representative of the A. pyrenaicum group from Spitsbergen. Phytotaxa 226: 63–74. doi: 10.11646/phytotaxa.226.1.6

Pinseel E., Kopalová K. & Van de Vijver B. (2014) Gomphonema svalbardense sp. nov., a new freshwater diatom species (Bacillariophyta) from the Arctic Region. Phytotaxa 170: 250-258. doi:  10.11646/phytotaxa.170.4.2

Advertisements