While polar terrestrial ecosystems appear to be snow and ice deserts most of the time, their marine counterparts bustle with life throughout the year. Vast amounts of plankton and ice-associated organisms sustain the marine, but also major parts of the terrestrial food web, all the way up to the highest predators, including penguins, seals and polar bears. Their annual cycles are extremely seasonal, but the strong plankton blooms in the spring set off a feeding extravaganza that does not only sustain the local fish, bird and sea mammal life, but even causes huge whales to travel to the polar regions over thousands of miles to feast there. Although the planktonic community is generally not very species-rich, its high abundance provides food input for an astonishing diverse and colourful benthic fauna as well. However, systems with low numbers of species are at the same time more vulnerable for impacts of global changes. International and interdisciplinary research efforts attempt to understand the biological responses to warming, sea ice retreat, freshwater input and other anthropogenic impacts such as ocean acidification and pollutants. Various types of models are developed to predict changes in the marine community structure that will impact greatly on these ecosystems and may have major repercussions on a global scale. These predictions can only be made in close collaboration with other disciplines such as physical oceanography and atmospheric sciences.
The ocean does not only cover two thirds of the Earth’s surface thereby linking polar regions and the tropics but it is also home to a multitude of microbial species, fish and mammals, it provides food for many people, and it buffers climate change.
Already now scientists observe rapid sea ice decrease and sea level rise endangering rare species like the polar bear but also entire human settlements in shallow coastal regions. What will happen to the CO2 storage capacity of the ocean with increasing water temperatures? And how will fish, penguins, albatross and seals survive if humans keep harvesting krill? All these questions, concerns, and much more is addressed in the various fields of research related to polar marine science.
Limnology is the study of inland waters ranging in size from large lakes down to puddles, as well as wetlands and running-water systems such as streams, rivers and estuaries. Inland waters range from very fresh glacier- or groundwater-fed systems, to brackish saline waters in isolated or ocean-influenced basins. Inland water bodies can be permanent features of the landscape, or may be ephemeral features that are only present seasonally. The wide variation in possible sizes, physicochemical characteristics and permanence of inland waters makes limnology a very diverse field of study!
Studying limnology in polar regions adds even more complexity – there are extreme variations in light, nutrient availability and temperature amongst seasons. The presence of a seasonal ice cover, near-desert conditions in surrounding tundra landscape, and very low temperatures all exert strong influences on polar inland waters.
Limnology is an important field of study in the polar regions because lakes and rivers are abundant in the arctic, and in some parts of Antarctica as well. Understanding the processes that occur within a catchment gives a better perspective on interactions within the landscape. For instance, biogeochemical processes generally occur more rapidly in water than they do in polar soils or terrestrial vegetation, making aquatic habitats hot spots for biodiversity and productive aquatic food webs. In the arctic, processes occurring in inland waters also have important impacts on the world’s oceans, because riverine outflow to the Arctic Ocean influences the global thermohaline circulation.
Microbial ecology is the study of interrelationships between microorganisms and the living and non-living aspects of the environments that they inhabit. Microorganisms are important players in Polar habitats, where they are major drivers of biogeochemical cycles in aquatic and terrestrial ecosystems. In the Arctic, for example, the thawing of permafrost could lead to increases in microbial activities and carbon decomposition, resulting in accelerated release of greenhouse gases. In the Antarctic, microorganisms are important in mediating nutrient cycling in surface lakes and subglacial environments, which are thought to carry important nutrients to the surrounding Southern Ocean. Additionally, studies focusing on the survival mechanisms of microbes exposed to sub-zero conditions or freeze-thaw cycles contribute to our understanding of the resilience of life and to advances in the fields of biotechnology and astrobiology. Answering basic questions about microbial ecosystems can be difficult, as the systems cannot be observed directly, but recent technological advances allow the construction of molecular “blueprints”, which are keys to describing and understanding microbial ecosystems. Large quantities of these molecular data help inform our understanding of microbial population structures and metabolic activities, as well as how these elements interact with the environment as a whole. Combining current molecular approaches with field-based measurement and laboratory-based culture studies allows today’s microbial ecologists to examine important issues ranging from the impact of changing climate on nutrient cycling to life’s ability to survive in extreme environments.