Primary Productivity Flashcards
Light scattered, reflected and absorbed by clouds and atmosphere
45-50%
Light reflected from surface ocean
4-5%
Light absorbed by ocean (total surface radiation)
45-50%. ~50% infrared and ultraviolet- scattered and absorbed near surface. ~50% visible spectrum/ photosynthetically active radiation (PAR), decreasing with depth
Photic zone
Well lit- photosynthesis can occur
Dysphotic zone
Twilight, poorly-lit, no photosynthesis or growing plants
Aphotic zone
No light, chemosynthesis only
Nutrient concentrations
Highest in the deep ocean due to decay of otganic matter sinking through the water column
Upwelling of nutrients
Nutrients are supplied to surface ocean biota by upwelling and vertical mixing of water masses. High primary production
Areas highest in upwelling
Along the equator, continental margins and the Southern Ocean
Density
A function of salinity and temperature
Shallow stable mixed layer
Phytoplankton kept in a well-lit environment favourable for growth
Deep mixed layer
phytoplankton mixed over greater depth range and range of light conditions –> less favourable for growth–> low growth rates –> low primary productivity
Plankton
Derived from the Greek for ‘wandering’- they wander because they cannot control their motion against the current
Phytoplankton
Single-celled plants, bacteria , protists. All photosynthesis. Dominant primary producers of the pelagic realm. Present througout the photic zone
Importance of phytoplankton
Base of ocean food chains and food webs . Convert inorganic nutrients (C,N,P) into organic matter and provide food for consumers in higher trophic levels. Major O2 producers
Pigments contained within chloroplasts
Chlorophyll a= dominant. Chlorophyll b, c, and d. Accessory pigments e.g. phycoerythrin
Metabolism
All chemical reactions occurring in living organisms; allow organisms to grow and reproduce, maintain structures, respond to the environment
Intermediary metabolism
Conversion of energy in food to energy available for cellular processes; conversion of food into building blocks for proteins, lipids, nucleic acids and some carbohydrates; elimination of metabolic wastes
Respiration
A set of metabolic reactions that break down organic matter and release large amounts of energy- this energy supports other metabolic processes of all cells
Vital processes carried out by cells needing energy
Cell division, movement, maintaining body temperature, building/synthesising molecules
Food
The source of chemical energy for most living things; fats contain more than twice as much energy/gram as carbohydrates and proteins, which each contain similar amounts of energy
Major groups of phytoplankton
Diatoms, Coccolithophores, Dinoflagellates
Diatoms
Glass cell walls (“frustules”) formed by taking up dissolved silica from sea water. Two valves made of silica (SiO2) 20-200um in length
Diatoms- key features
Inhabit all aquatic environments but dominant in high nutrient areas. Produce 20-50% of Earth’s oxygen/ year. Substantial contribution to total ocean OM. Large and widespread deposits on the ocean floor.
Diatom taxonomy
Centric diatoms (order Centrales)= radially symmetric and dominate planktonic communities (appeared 120mya).
Pennate Diatoms( order Pennales)= Bilaterally symmetric. Typical of benthic, marine and freshwater communities (appeared 70mya)
Organelles
Living parts or specialised substructures within the cell
Plastids
Major organelles in plant and algal cells. Manufacture and storage of important chemical compounds. Often contain pigments used in photosynthesis
Nucleus- diatom
At centre of diatom; often spherical or lenticular and encloses chromosomes and nucleoli
Nucleolus
Composes of proteins and nucleic acids; transcribes ribosomal RNA (rRNA) and assembles it within the cell
Protoplasm
All living parts within the frustule- cell membrane, nucleus, cytoplasm, mitochondria, plastids and other organelles
Cytoplasm
Colourless gel-like plasma inside frustule and enclosed within cell membrane ~80% water- cytosol, hold all organelles (e.g. mitochondria) except the nucleus in eukaryotes
Raphe
Elongated fissure in valves of pennate diatoms. Used by diatom for movement. Important for identification
Diatom structure
2 interlocking valves:
- Epitheca: larger older valve with girdle elements (epicingulum)connected to it
- Hypotheca: smaller younger valve with girdle elements (hypocingulum)connected to it. Connective zone: overlapping girdle elements that connect the valves, sutures allow movement
Septa
Partitions formed within valves- used to characterise diatoms
Nucleoplasm
Holds the contents of the nucleus
Diatom ornamentation
Valve surfaces are usually covered with striations, pores, spines, punctuations and/or raphes. Very important for diatom ornamentation
Setae
Spine-like projections common in diatoms
Increase cell surface area
Increases drag and reduces the cell’s sinking rate into deeper darker waters with less sunlight
Asexual reproduction in diatoms
- Epitheca and hypotheca of parent cell both become epitheca of daughter cell; new hypotheca constructe
- Cell size limited by rigid cell wall* Each cell division creates smaller cells, so the average cell size of population decreases until cells are ~1/3 their maximum size
- When cells reach critical size limits, sexual reproduction and auxospore formation are triggered to restore population cell size
