Marine Primary Production and Nutrients

These vocabulary flashcards cover the fundamental concepts of marine primary production, light dynamics in the ocean, photosynthetic parameters, and nutrient uptake mechanisms as discussed in the lecture.

Primary Production

The formation of organic matter through the trapping of light energy and the assimilation of inorganic elements.

Primary Productivity

The rate of the net incorporation of inorganic carbon into organic compounds, ideally measured as $\text{kg C m}^{-2} \text{ year}^{-1}$.

Photoautotrophs

Photosynthetic organisms that drive the majority of primary production in the ocean.

Phytoplankton

Microscopic primary producers, often less than $2\text{ mm}$ in size, which include groups like cyanobacteria, diatoms, and dinoflagellates.

Phycobilins

A group of accessory pigments found in red algae ($\text{Rhodophyta}$) that assist in harvesting light and provide the red color.

Fucoxanthin

The primary brown accessory pigment found in brown algae ($\text{Phaeophyceae}$).

Attenuation

The decrease in light intensity and change in light quality (wavelength) as depth increases in the marine environment.

Photon Flux Density

A measure of irradiance defined as the amount of light per meter squared per second, typically in $\text{micromoles photons m}^{-2} \text{ s}^{-1}$.

Photoacclimation

A non-evolutionary process where a photosynthetic organism responds to its light environment by altering its photosynthetic apparatus, such as increasing pigments or reaction centers.

Photosynthetic Unit

A conceptualized structure containing pigments for harvesting light energy and a reaction center where light energy is converted to chemical energy.

Pmax

The maximal photosynthetic rate achieved at light saturation on a photosynthesis versus irradiance curve.

Alpha ($\text{alpha}$)

The initial slope of the P-I curve during the light-limited phase, indicating how efficiently an organism harvests light at low levels.

EK

The specific irradiance or photon flux density level where photosynthesis reaches saturation.

EC (Compensation Irradiance)

The irradiance level at which the rate of photosynthesis exactly cancels out the rate of respiration.

Oligotrophic

A classification for marine systems with low concentrations of essential nutrients and low primary production.

Eutrophication

An increase in the rate of organic matter into an ecosystem, typically caused when a limiting nutrient becomes non-limiting.

Leibig’s Law of the Minimum

The principle stating that growth is limited by the scarcest essential nutrient relative to an organism's requirements, rather than total nutrient availability.

Passive Diffusion

A mechanism of nutrient uptake where nutrients move across the cell membrane without the requirement of energy, typically resulting in a linear relationship with external concentration.

Active Transport

An energy-requiring mechanism of nutrient uptake that can move nutrients against a concentration gradient and eventually reaches a saturation point ($V_{max}$).

Vmax

The maximum nutrient uptake rate for a species when the nutrient concentration is no longer limiting.

New Production

Primary production stimulated by 'new' nitrogen entering the system from outside, such as nitrate ($NO_3^-$) from upwelling events.

Regenerated Production

Primary production based on nitrogen recycled within the biota, mostly in the form of ammonium ($NH_4^+$) or urea.

Redfield Ratio

The theoretical stoichiometric ratio of $106\text{ C} : 16\text{ N} : 1\text{ P}$ found in phytoplankton for optimal growth.

C:N Ratio

A tool used to assess the health of algae; for example, a ratio greater than $6.6$ in phytoplankton often indicates nitrogen limitation.

Silica

An essential nutrient required specifically by diatoms to form their cell walls, known as frustules.

Iron

A micronutrient that can limit the growth of diatoms and other phytoplankton, particularly in High Nutrient Low Chlorophyll (HNLC) regions of the ocean.