Food Webs

What is the role of marine microbes in food webs?

they obtain energy, fix carbon dioxide, decompose organic matter, and serve as food for other organisms.

What is the microbial loop?

a concept that describes how microbes transfer energy and elements within marine food webs.

What are the key components of the microbial loop?

Key components include dissolved organic matter and the phagocytosis of bacteria.

How do marine microbes contribute to the global carbon budget?

They move carbon through the ecosystem, linking oceanic processes to atmospheric CO2 levels.

What is photoautotrophy?

the process where organisms use light energy to fix CO2 into organic carbon.

What organisms perform photoautotrophy?

Cyanobacteria, eukaryotic phytoplankton, and some forms of bacterial photosynthesis.

What is the role of Rubisco in photosynthesis?

an enzyme that plays a major role in the Calvin cycle for CO2 fixation.

What is chemoautotrophy?

a form of primary production that occurs in the absence of light, using inorganic chemicals for energy.

What is heterotrophy?

the process where organisms use organic carbon as their carbon source.

What is the significance of dissolved organic matter (DOM)?

it plays a crucial role in nutrient cycling and serves as a major energy source for microorganisms in aquatic ecosystems. It also influences water quality and the transport of pollutants, impacting overall ecosystem health

Who is considered the grandfather of marine microbiology?

Claude ZoBell.

What did Charles Darwin speculate about flagellates in the ocean?

He wondered how they found enough food to thrive in clear blue water.

What is the Great Plate Count Anomaly?

It refers to the discrepancy between the number of bacteria estimated in seawater and those that can be cultivated in labs.

What is the primary production process in photoautotrophic organisms?

The fixation of CO2 through photosynthesis, primarily in the Calvin cycle.

What is the role of bacteria in the microbial food web?

move dissolved organic carbon to bacterial biomass and play a crucial role in carbon cycling.

What is mineralization in the context of microbial processes?

the conversion of organic compounds into CO2 and other inorganic compounds.

What methodology advancements helped in studying marine microbiology?

The development of epifluorescence microscopy, fluorescent stains, and flow cytometry.

What was the significance of Lawrence Pomeroy's 1974 paper?

It redefined the ocean's food web, emphasizing microbial respiration and the role of dissolved organic matter.

What is the estimated contribution of bacterial biomass to oceanic carbon?

Almost half of all carbon biomass in the ocean is attributed to bacterial auto- and heterotrophs.

What are the two forms of primary production discussed?

Photoautotrophy and chemoautotrophy.

What is the role of phagocytosis in marine food webs?

it allows protists to feed on bacteria, transferring energy and elements to the food web.

What is the relationship between microbial activities and human food production?

they are fundamental for oceanic carbon uptake, processing, and contribute to the conservation of marine biota.

What is the primary energy source for chemo-organotrophy?

Organic carbon.

What is the significance of the picocyanobacterium Synechococcus?

It was discovered to be a significant photoautotroph, contributing to new estimates of primary production.

What is the role of ammonium (NH4+) and phosphate (PO43-) in microbial processes?

They are released during the mineralization of organic compounds by prokaryotes.

What is DOM?

Dissolved Organic Matter, formed by release from live organisms and when cells die.

How do zooplankton contribute to DOM?

Through 'sloppy feeding' which spills DOM into the surroundings and by producing fecal pellets.

What is the difference between DOM and POM?

DOM is defined as organic matter that passes through a 0.45 micrometer filter, while POM is captured by the filter.

What organisms are involved in the microbial loop?

Bacteria, flagellated microplankton, ciliates, and macrozooplankton such as copepods.

What is the role of viral lysis in the microbial loop?

It causes cell death, returning DOM back to the bottom of the food web and disrupting the loop.

What is mixotrophy?

The ability of some organisms to be both autotrophic and heterotrophic, consuming organic matter and fixing CO2.

How does microbial net growth relate to losses?

the total growth - losses, typically balanced in the marine environment.

What is the estimated growth rate of Prochlorococcus?

Approximately one cell division per day.

What is the significance of the viral shunt?

It shunts organic matter from POM to DOM, keeping carbon away from the food web.

What are some examples of nanoflagellates?

Prymnesiomonads and Cafeteria roenbergensis.

What is the size range of nanoplankton?

Approximately 2-20 µm.

What is the role of microplankton in bacterivory?

plankton, such as dinoflagellates and ciliates, contribute to the consumption of bacteria.

What happens to carbon at each step of the microbial loop?

Energy and carbon are transferred to the next level, with losses occurring through cell death and respiration.

What is the typical abundance of Prochlorococcus in the open ocean?

Approximately 100,000 cells/mL.

What is the importance of the microbial loop in marine ecosystems?

It captures carbon back into the food web, supporting the entire marine food web.

What is the role of mineral cycling in the microbial loop?

It occurs during the remineralization process with DOM decomposition.

What are some complications in understanding the microbial loop?

Mixotrophy and viral lysis introduce uncertainties in the roles of organisms in food webs.

What is the size range of microplankton?

Approximately 20-200 µm.

What is the definition of refractory organic matter?

Organic compounds that are more resistant to degradation.

What is the impact of grazing on microbial populations?

it balances microbial growth, maintaining stable cell numbers.

What are larvacean houses?

Structures produced by larvaceans that contribute to POM.

What is the significance of the microbial loop diagram?

It illustrates the different paths for carbon in the food web, showing organism size and advancement.

What are some examples of mixotrophic organisms?

Nanoplankton that can consume bacteria and perform photosynthesis.

What is the role of copepods in the microbial loop?

They serve as food for larger organisms, transferring energy and carbon up the food web.

What is the main source of DOM from viruses?

Viruses that cause the lysis of organisms.

How does the microbial loop affect carbon cycling?

It facilitates the transfer of carbon back into the food web, impacting overall productivity.