Plankton are the diverse collection of organisms found in water that are unable to propel themselves against a current. The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucial source of food to many small and large aquatic organisms, such as bivalves, fish, and baleen whales.
Zooplankton are the animal component of the planktonic community, having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequently, they drift or are carried along by currents in the ocean, or by currents in seas, lakes or rivers.
Lake Vostok is the largest of Antarctica's 675 known subglacial lakes. Lake Vostok is located at the southern Pole of Cold, beneath Russia's Vostok Station under the surface of the central East Antarctic Ice Sheet, which is at 3,488 m (11,444 ft) above mean sea level. The surface of this fresh water lake is approximately 4,000 m (13,100 ft) under the surface of the ice, which places it at approximately 500 m (1,600 ft) below sea level.
Lake Vida is a hypersaline lake in Victoria Valley, the northernmost of the large McMurdo Dry Valleys, on the continent of Antarctica. It is isolated under year-round ice cover, and is considerably more saline than seawater. It came to public attention in 2002 when microbes frozen in its ice cover for more than 2,800 years were successfully thawed and reanimated.
A subglacial lake is a lake that is found under a glacier, typically beneath an ice cap or ice sheet. Subglacial lakes form at the boundary between ice and the underlying bedrock, where gravitational pressure decreases the pressure melting point of ice. Over time, the overlying ice gradually melts at a rate of a few millimeters per year. Meltwater flows from regions of high to low hydraulic pressure under the ice and pools, creating a body of liquid water that can be isolated from the external environment for millions of years.
Biological oceanography is the study of how organisms affect and are affected by the physics, chemistry, and geology of the oceanographic system. Biological oceanography may also be referred to as ocean ecology, in which the root word of ecology is Oikos (oικoσ), meaning ‘house’ or ‘habitat’ in Greek. With that in mind, it is of no surprise then that the main focus of biological oceanography is on the microorganisms within the ocean; looking at how they are affected by their environment and how that affects larger marine creatures and their ecosystem. Biological oceanography is similar to marine biology, but is different because of the perspective used to study the ocean. Biological oceanography takes a bottom-up approach, while marine biology studies the ocean from a top-down perspective. Biological oceanography mainly focuses on the ecosystem of the ocean with an emphasis on plankton: their diversity ; their productivity and how that plays a role in the global carbon cycle; and their distribution.
The microbial loop describes a trophic pathway where, in aquatic systems, dissolved organic carbon (DOC) is returned to higher trophic levels via its incorporation into bacterial biomass, and then coupled with the classic food chain formed by phytoplankton-zooplankton-nekton. In soil systems, the microbial loop refers to soil carbon. The term microbial loop was coined by Farooq Azam, Tom Fenchel et al. in 1983 to include the role played by bacteria in the carbon and nutrient cycles of the marine environment.
Antarctica is one of the most physically and chemically extreme terrestrial environments to be inhabited by lifeforms. The largest plants are mosses, and the largest animals that do not leave the continent are a few species of insects.
Marine microorganisms are defined by their habitat as microorganisms living in a marine environment, that is, in the saltwater of a sea or ocean or the brackish water of a coastal estuary. A microorganism is any microscopic living organism or virus, that is too small to see with the unaided human eye without magnification. Microorganisms are very diverse. They can be single-celled or multicellular and include bacteria, archaea, viruses and most protozoa, as well as some fungi, algae, and animals, such as rotifers and copepods. Many macroscopic animals and plants have microscopic juvenile stages. Some microbiologists also classify viruses as microorganisms, but others consider these as non-living.
LExEN, an acronym for Life in Extreme Environments, is a research program overseen by the National Science Foundation. It was originally developed by G. Michael Purdy in 1997 as an area of research in which scientists could seek funding for activities in the polar regions. Participating were the Directorates for Biological Sciences, Mathematical and Physical Sciences, Engineering, Geosciences, and the Office of Polar Programs of the National Science Foundation. The program sought to place a strong emphasis upon those life-supporting environments that exist near the extremes of planetary conditions. The study of extreme habitats, both planetary and extra-planetary, was underpinned by the idea that "deep understanding of certain earth-bound microbial systems would provide important insights into life-sustaining processes and the origin of life on our own planet, while illuminating the search for life in other planetary environments."
Mycoplankton are saprotrophic members of the plankton communities of marine and freshwater ecosystems. They are composed of filamentous free-living fungi and yeasts that are associated with planktonic particles or phytoplankton. Similar to bacterioplankton, these aquatic fungi play a significant role in heterotrophicmineralization and nutrient cycling. Mycoplankton can be up to 20 mm in diameter and over 50 mm in length.
Cristina Takacs-Vesbach is an American microbial ecologist conducting research on the productivity, diversity, and function of microbial communities living at the two extremes of temperature found on Earth-Antarctica's McMurdo Dry Valleys and Yellowstone National Park's thermal springs.
Trista Vick-Majors is an American Assistant Professor in Biological Sciences at Michigan Tech. She is an Antarctic biogeochemist and microbial ecologist, best known for her work showing that microorganisms are present under the Antarctic ice sheet.
Corina Brussaard is a leading scientist for Antarctic viral ecology working for the Royal Institute of Sea Research (NIOZ) and is a Special Professor of Viral Ecology at the Institute for Biodiversity and Ecosystem Dynamics of the University of Amsterdam (UvA).
Jill Ann Mikucki is an American microbiologist, educator and Antarctic researcher, best known for her work at Blood Falls demonstrating that microbes can grow below ice in the absence of sunlight. She is a leader of international teams studying study ecosystems under the ice.
Mary Ann Moran is a distinguished research professor of marine sciences at the University of Georgia in Athens. She studies the role of bacteria in Earth's marine nutrient cycles, and is a leader in the fields of marine sciences and biogeochemistry. Her work is focused on how microbes interact with dissolved organic matter and the impact of microbial diversity on the global carbon and sulfur cycles. By defining the roles of diverse bacteria in the carbon and sulfur cycles, she connects the biogeochemical and organismal approaches in marine science.
Sea Ice Microbial Communities (SIMCO) refer to groups of microorganisms living within and at the interfaces of sea ice at the poles. The ice matrix they inhabit has strong vertical gradients of salinity, light, temperature and nutrients. Sea ice chemistry is most influenced by the salinity of the brine which affects the pH and the concentration of dissolved nutrients and gases. The brine formed during the melting sea ice creates pores and channels in the sea ice in which these microbes can live. As a result of these gradients and dynamic conditions, a higher abundance of microbes are found in the lower layer of the ice, although some are found in the middle and upper layers. Despite this extreme variability in environmental conditions, the taxonomical community composition tends to remain consistent throughout the year, until the ice melts.
The viral shunt is a mechanism that prevents marine microbial particulate organic matter (POM) from migrating up trophic levels by recycling them into dissolved organic matter (DOM), which can be readily taken up by microorganisms. The DOM recycled by the viral shunt pathway is comparable to the amount generated by the other main sources of marine DOM.
Compared to terrestrial environments, marine environments have biomass pyramids which are inverted at the base. In particular, the biomass of consumers is larger than the biomass of primary producers. This happens because the ocean's primary producers are tiny phytoplankton which grow and reproduce rapidly, so a small mass can have a fast rate of primary production. In contrast, many significant terrestrial primary producers, such as mature forests, grow and reproduce slowly, so a much larger mass is needed to achieve the same rate of primary production.
Jennifer B. H. Martiny is an American ecologist who is a professor at the University of California, Irvine. Her research considers microbial diversity in marine and terrestrial ecosystems. In 2020 she was elected a Fellow of the American Association for the Advancement of Science.
