Notes on Marine Nutrients

These flashcards cover key concepts related to nutrients in marine biology, focusing on phytoplankton, nutrient requirements, nutrient cycling, and environmental impacts.

What elements are required by photoautotrophs in marine environments?

Potassium, Sodium, Silicon, Sulphur, Copper, Zinc, Vitamin B12, biotin, thiamine.

What are commonly limiting nutrients in marine habitats?

Nitrogen and Phosphorous.

What is the typical composition of phytoplankton?

40% carbohydrates, >40% protein, 5% nucleic acids, and 15% lipids.

What ratio is used to determine the physiological health of phytoplankton?

The Carbon: Nitrogen: Phosphorous - Redfield ratio.

What indicates phosphorus limitation in terms of the N:P ratio?

If N:P > 16.

What indicates nitrogen limitation in terms of the N:P ratio?

If N:P < 16.

Which bacteria can fix N2 into biologically available nitrogen?

Cyanobacteria, such as Trichodesmium.

What is the F-ratio in the context of nitrogen production?

The ratio of new production to total production is typically 0.3-0.5.

What is the most common form of nitrogen taken up by organisms?

Nitrate (NO3-).

What is the role of Archaea in the marine nitrogen cycle?

They are important in the removal of nitrogen from the oceans.

What does DMSP stand for, and why is it significant in marine ecosystems?

Dimethylsulphonioproprionate; it helps regulate climate and is a key component in microbial food webs.

What environmental effect does dimethylsulfide (DMS) have when released into the atmosphere?

It is oxidized to form sulfate aerosols that create clouds.

How does DMSP influence zooplankton feeding behavior?

Zooplankton grazing on phytoplankton increases DMS production, which attracts predators.

What process forms H2S from DMSP in marine sediments?

Most of DMSP is converted into methanethiol and can be released as H2S.

What happened during the IronEx experiments regarding phytoplankton growth?

Adding iron to seawater led to a bloom of phytoplankton and a significant reduction in nitrate concentration.

What factors influence nutrient uptake in phytoplankton?

Nutrient charge, cell membrane transport methods, cell size and surface area, and turbulence.

What is the significance of the maximum cell doubling rate (Dmax) and half saturation constant (K3) for phytoplankton?

Different species of phytoplankton have specific K3 and Dmax values, influencing their nutrient uptake efficiency.

What is the specific atomic Redfield Ratio for C:N:P?

The ratio is 106:16:1.

Which specific group of phytoplankton requires Silicon for their cell walls?

Diatoms, which use silicate (SiO_4) to construct frustules.

What are HNLC regions in the context of marine nutrients?

High-Nitrate, Low-Chlorophyll regions where phytoplankton growth is limited by a lack of iron rather than nitrogen.

What is the difference between "new production" and "regenerated production"?

1. New Production: Fueled by nutrients entering the photic zone from the outside (e.g., upwelling or atmospheric deposition).
2. Regenerated Production: Fueled by nutrients recycled within the photic zone (e.g., excretion by zooplankton).

What process describes the conversion of Ammonium (NH4^+) to Nitrate (NO3^-)?

Nitrification, which is a two-step aerobic process often performed by nitrifying bacteria and archaea.

How does cell size affect the Half Saturation Constant (K_s)?

Smaller cells generally have lower K_s values, meaning they are more efficient at taking up nutrients at low concentrations due to a higher surface-area-to-volume ratio.

What is the "Biological Pump"?

The process by which inorganic carbon is fixed by phytoplankton and then transported to the deep ocean as organic matter sinks.

Besides climate regulation, what role does DMSP play for phytoplankton cells?

It acts as an osmolyte, helping the cell maintain osmotic balance against the salinity of seawater.