week 9-elle Flashcards
what percent of total global oxygen is produced by marine autotrophs
50-80%
what is primary productivity
rate at which organisms store energy through the formation of organic matter (carbon-based cmpds) from inorganic carbon (CO2)
Photosynthesis
-completed by photo autotrophs
-process by which photoautotrophic organisms (primary producers) use the energy from sunlight to produce glucose from CO2 and Water
light is absorbed by
clorophyll
clorophyll
-converts light energy ti chemical energy (sugar)
-found within the thylakoids that exist within chloroplasts
Full process of photosynthesis combines 2 parts:
- Light absorption phase
- Dark reaction phase
Light absorption phase
-chlorophyll absorbs light, transfers energy to electron acceptors: ADP/NADP+
-these are transformed into ATP/NADH
Dark reaction phase
-The calvin cycle (occurs in stroma - intracellular fluid)
-enzymatically controlled
-converts energy within ATP and NADPH (combined with CO2) to glucose
Three phases of the calvin cycle
- Carbon fixation
- Reduction
- Regeneration
Carbon fixation
CO2 combined into 5 carbon chain, resulting in unstable 6 carbon cmpd immediately splitting into 2 (PGA) molecules
Reduction
PGA molecueles are phosphorylated by ATP and reduced by NADPH to form G3P
**this stage consumes ATP and NADH to make glucose
Regeneration
some G3P are used to regenerate RuBP used in phase 1 with the help of ATP
Photosynthesis in temperate regions
annual cycle of marine productivity
-blooms of phytoplankton in spring & fall
-sunlight greatest in summer
-zooplankton spike in spring
sunlight, water and seasons
sunlight reflected most in winter, least in summer
when is there most nutrient poor water
Summer
when is there a developing thermocline
spring
when is there a strong thermocline
summer
when is there a weakening thermocline
fall
when is phytoplankton and zooplankton most abundant
spring
How do primary producers make food
use energy release by inorganic chemical rxns
Aphotic zone
no light here
where are hydrothermal vent communities found
deep ocean
where do primary producers typically live
as symbionts in macro-fauna in hydrothermal vent ecosystems
EXAMPLES OF PRIMARY PRODUCERS
- giant tubeworms
-Bathymodiolus mussels
-Alviniconcha gastropods
Examples of chemoautotrophic bacteria
-sulfur reducers & Oxidizers
-iron reducers
-Hydrogen reducers
is there are so many chemoautotrophs, why is photoautotrophic primary production so abundant?
diverse array of chemoautotrophs, but large abundance of photoautotrophs
units for primary producitivty
gC/m2/yr
-grams of carbon bound into organic material per square metre of ocean surface area per year
***typically 120
How can we measure primary productivity
plankton tow
Plankton net samples
- measure dry weight / wet weight of bucket after net rinse
What affects primary productivity
- Availability of nutrients (low latitudes)
- Availability of solar radiation (higher latitudes)
what is required for molecule constriction and for skeletons and shells
nitrogen, phosphprus, iron, carbon and silica
Bioeochemical cycle
-nutrients transferred through land and ocean
-many different ways nutrients enter the ocean (natural and anthropogenic)
What happens if one nutrient is lacking?
-limits production
-the lacking nutrient is the rate limiting step in the production process
what if there is a spike in the input of the limiting nutrient
cultural eutrophication
Redfield ratio
-affects primary productivity
-proportion of nutrients in phytoplankton
Optimal ratio for phytoplankton growth
106 carbon: 16 nitrogen: 1 phosphorus
Southern ocean has abundance of
Nitrate and phosphorus but lacks chlorophyll to match these levels
What is a major limiting nutrient
Iron
- led to the Iron-hypothesis to reduce climate change impacts
Iron-hypothesis to reduce climate change impacts
- John martin proposed i the 1990s that adding iron to Southern Ocean would reduce climate change by increasing CO2 removal
***researchers found CO2 was removed faster but other more potent greenhouse gases were created
how far does light reach down in the ocean in the clearest water
1000m
Euphotic zone
-sunlight reaches
-photosynthesis occurs
-sunlight rarely penetrates beyons this
Dysphotic Zone
- twilight zone
- sunlight rapidly decreases with depth
-photosynthesis not possible
Aphotic Zone
- midnight zone
- sunlight does not penetrate at all
-bathed in darknes
Fish in euphotic zone
tuna
Fish in twilight zone
- shrimp
- swordfish
- hatchet fish
fish in midnight zone
- tripod fish
- giant squid
- angler fish
Why is the ocean blue is water is clear?
blue is transmitted/reflected while the other colours are absorbed
what can we use to measure how transparent the water is
Seechi disk
Seechi depth
depth the disk can no longer be seen (measure of light penetration)
Examples of primary producers (photoautotrophs)
- sea grasses
-macroscopic algae (seaweed) - phytoplankton
- Diatoms
-Coccolithophores - Dinoflagellates
sea grasses
- only true plants that have their complete life cycle within the oceans
- seed-bearing vascular structures
- Phylum: Anthophyta
Macroscopic Algae
- looks plant-like but NOT a plant
- they are protists
- no vascular tissue
parts of macroscopic algae
- Thallus: entire body
- Frond: flattened structure like leaf
- Stipe: stem-like structure, not always present
- Gas bladder: hollow, gas filled structure on frond
- Holdfast: specialized structure at base, attaches to hard surface
unicellular/multicellular algae are not plants but…
- still photosynthesize
- great diversity in size and shape
- partially classified based on colour pigment they contain
Green algae
chlorophyta
- intertidal
- shallow water
Red algae
rhodophyta
- most abundant
- widely distributed
- attached to substrate or encrusting
Brown algae
phaeophyta (rockweed, kelp)
**can grow heights of 34m
Phytoplankton
-autotrophic plankton
- create glucose via photosynthesis
-occupy euhotic zone
-huge population
-invisible to naked eye
-90-96% of surface oceans carbohydrate
- necessary compoennt for marine life
-producers of atmospheric oxygen
Cocolithophores
- covered with small plates
-made of calcite - moderate to low nutrient conditions
- tend to live in waters that are brightly lit; temperate to warm
- sediment producers
- very small: 5-100um
site of cocolithophore bloom
barents sea off coast of norway
Dinoflagellates
- single-celled organisms
-microscopic - internal skeleton (cellulose & siliceous)
-variety of shapes and sizes - small to large: 2-2000um
-have flaglla (small apendage)
what do flagella facilitate
allows movement and obtains nutrients
unique feature of dinoflagellates
- can be bioluminescent (caused by movement)
-red during the day but blue at night
Explosive growth of dinoflagelates caused
-red tides and harmful algal blooms (red b/c red pigment)
-can be toxic or non toxic
-can ddeplete water of oxygen (response from zooplankton)
what uses O2
chemoheterotrophs NOT primary producers
Exponential growth of dinoflagellates due to
- favourable winds and currents
- over feeding
- high water conditions
how do dinoflagellates make it into our diet
shellfish filter them and we eat shellfish
when/where are dinoflagellates seasonal
april - november in the Northern hemisphere
Diatoms
-some of most productive photosynthesizers
- presence indicates high nutrient conditions
- small to large: 2-2000um
- top half and bottom half fitting together
Halves of diatoms
- Epitheca (larger top half)
- Hypotheca (smaller bottom half)
what type of diversity is high in diatoms
phenotypical
-different shapes and sizes
composition of diatoms
glass/sand
where are the primary producers?
-abundance of phytoplankton varies with location
-phytoplankton distribution corresponds to nutrient distribution in the water (upwelling areas, large river inputs, wind blown nutrients)
who are the primary consumers?
-zooplankton (heterotrophic plankton)
-1cm-3.5m
-grazers
Zooplankton need what in order to live?
phytoplankton
Biotic community
assemblage of organism that live together within some definable area or habitat
Ecosystem
-biotic plus abiotic community
-organisms exchange energy and chemical substances (matter)
Energy Flow in marine ecosystems
-energy flow
-unidirectional
-energy transferred up food chain/web (up trophic levels)
What would happen without energy flow
the world would get hotter and hotter
Path of energy
Sun > Producers > Chemical Energy > Consumers > Energy of movement > Space
3 categories of organisms in an eccosystem
- Producers
- Consumers
- Decomposers
what do consumers do
break down compounds and turn them into somehting useable again
Producers
Autotrophic
Consumers
Heterotrophic; herbivores, carnivores, omnivores
Decomposers
heterotrophic; break down organic compounds
Trophic (Biomass) pyramid
- energy transfer between levels
-accurate representation of nutrient energy exchange in marine ecosystems
-as you move up, organisms get larger
BUT
-more biomass at the bottom
what percent of efficiency of energy transfer in a trophic pyramid
about 10%
Biomass on the pyramid
goes down as size goes up
general rule of thumb for species eating species
members of an ecosystem will only be slightly larger than the food they eat, but there are exceptions (krill & blue whales)
largest animal ever
blue whale
why do whales migrate
to coincide with plankton blooms
Food chain
sequence of organisms through which energy is transferred (over simplified)
Food web
interconnected food chains
why do heterotrophs rely on autotrophs
food and respiration
