Nutrient cycling Flashcards
Why are phytoplankton important in carbon and biogeochemical cycles?
Phytoplankton play a central role in marine and atmospheric systems as they help sequester carbon in the ocean, acting as carbon sinks
What are the major human impacts on the carbon cycle?
Fossil fuels, cement production, and land use changes contribute to a significant increase in carbon emissions, around 9 gigatonnes annually
What are the major elements in the oceans?
Cl^-, Na^+, Mg^2+, SO4^2-, Ca^2+, K^+ are found in high concentrations, and are conserved throughout the oceans, though they aren’t limiting nutrients
What macronutrients are important for plankton?
C, H, O, N, P, S, Mg, K, Ca, Si are macronutrients, and when present in low concentrations, they can be limiting nutrients for phytoplankton
What micronutrients are critical for plankton?
Fe, Mn, Cu, Zn, Mo, Cd, V, Co are essential micronutrients for plankton growth
What does the iron enrichment experiment suggest about iron fertilization in the ocean?
Large areas of the ocean, like the equatorial South Pacific, respond positively to iron fertilization, with lab experiments showing that 1 ton of Fe can draw 30-100K tons of carbon out of the atmosphere
What is the role of the microbial food web in the carbon cycle?
Phytoplankton biomass is consumed by grazing micro- and zooplankton, forming aggregates that sink to the ocean floor, sequestering carbon
e.g., fecal pellets
How do human activities affect the ocean’s carbon cycle?
Approximately 30-40% of CO2 from human activity dissolves in oceans, rivers, and lakes, altering the ocean’s carbon cycle
What is the biological carbon pump?
The biological carbon pump is a process where phytoplankton capture CO2 from the atmosphere, which then sinks to deeper ocean layers, helping to sequester carbon
What is the role of coccolithophores in the carbon cycle?
Coccolithophores produce calcite discs (coccoliths) that sink to the ocean floor and become part of sediment, contributing to carbon sequestration. They also produce DMSP, which helps in cloud formation, impacting the Earth’s albedo
How does calcification affect carbon cycling in the ocean?
Calcification by organisms like foraminifera and coccolithophores uses CO2 to form calcium carbonate, which can sink and sequester carbon, but also releases CO2 when the calcium carbonate dissolves
What are the major nitrogen and phosphorus cycles in the ocean?
Phytoplankton can fix N2 into ammonium, which undergoes nitrification into nitrate. Phosphorus mainly exists as phosphate and is integral in cellular components like ATP and DNA
What is the Redfield ratio?
The Redfield ratio (106C:16N:1P) reflects the typical stoichiometric ratio of carbon, nitrogen, and phosphorus found in oceanic phytoplankton biomass
What factors control primary production in the ocean?
Light, nutrients, and temperature control primary production. The euphotic zone, where light is sufficient for photosynthesis, plays a key role in productivity
What is the role of the deep chlorophyll maximum (DCM)?
The DCM occurs where light and nutrients limit growth. Phytoplankton adapt by increasing chlorophyll to maximize photosynthesis in lower light conditions
How does the thermocline affect nutrient mixing?
The thermocline prevents nutrient mixing between surface and deeper waters, limiting nutrient availability in the upper ocean
What is the role of microbes in the marine phosphorus cycle?
Microbes help cycle phosphorus in marine ecosystems by converting phosphate (Pi) into organic forms and decomposing organic phosphorus (DOP)
What abiotic and biotic factors influence marine ecosystems?
Abiotic factors include light, temperature, nutrients, pH, and salinity
Biotic factors include grazers, bacteria, symbiosis, and phytoplankton growth
Abbreviations
- POC (and or TC) – DOC Particulate Organic Carbon (>0.2 microns
is a particle, if less, its Dissolved Organic Carbon) - PON – DON Particulate (Dissolved) Organic Nitrogen
- POP (DOP) Particulate (Dissolved) Organic Phosphorus
- DIP (Pi Phosphate) DIP: Dissolved In-organic Phosphorus
- DCM (Deep Chlorophyll Maxima)
- NPP and GPP (Net and Gross Primary Production)
- μ and μmax (phytoplankton growth rate)
TERMS AND ACRONYMS
