311 final Flashcards
(87 cards)
1
Q
what are phytoplankton adapting to?
A
light, nutrient availability, grazing pressures
2
Q
what phytoplankton have shells and what are they made of?
A
diatoms - silica
coccolithophores - calcium carbonate
3
Q
what are advantages and disadvantages of having shells?
A
disadvantages:
- energetically costly
- sinking - takes them out of euphotic zone
advantages:
- protection from grazing (predators always choose prey with no shells over shelled)
- buoyancy control - some sinking allows for increased nutrient uptake bc refreshes water around it
4
Q
what mechanisms are used to prevent sinking
A
- change shell thickness
- gas vacuole
- flagella for swimming
- fats and oils
- attachment
- removal of dense stuff - like salt ions
- spine and colony formation - to increase surface area
sudden increasing in density slows sinking
5
Q
what are reasons for slower growth rate in diatoms
A
light limitation
nutrient limitation
(N, P, Fe) - Si not limiting here
6
Q
how does slower growing relate to shell formation
A
slower growth rate is associated with thicker shells
7
Q
experiment showing shell thickness and size in diatoms (and correlation to predators)
A
thicker shells of diatoms = less eaten by copepod nauplii
increased size of diatoms = less eaten by dinoflagellates
8
Q
- how do spines and colonies work
A
diatoms have spines to increase drag bc of increased surface area
mechanism to allow for slower sinking
9
Q
- flagellates
A
flagella allow for them to move purposefully
many have photoactive cells to detect light
10
Q
- removal of dense stuff like salt ions
A
concentration of ions in diatom storage vacuoles (cell sap)
salt ions lower conc inside vacuole (inside cell) than outside
density of vacuole lower than sea water –> phytoplankton actively transport salt ions out of cell to lower density
11
Q
how does nutrient availability change sinking speed ?
A
more nutrient limited - sink faster
more nutrients = sink slower
12
Q
In what ways does zooplankton size impact grazing?
A
SMALL ZOOP:
- some small zooplankton are same size as phytoplankton –> small zooplankton can only eat so big, many cant feed on large diatoms
- can have tight coupling between zoop and phyto if both are small - they both stay at the top
LARGER ZOOP:
- larger zooplankton can graze larger organisms
- group dependent
- larger zooplankton are more complex and can be more selective - migration –> how they control phyto bloom dependent on timing
- specialization
- greater mobility
- reproduce slower
13
Q
What is the difference between ML light availability and euphotic zone
A
MLD is determined by how much light is experienced by phytoplankton
14
Q
what is surface irradiance determined by
A
sea sun, latitude, weather, particulates (absorb and scatter light)
15
Q
What does mixed layer light availability depend on?
A
- surface irradiance –> sea sun, latitude, weather
- mixed layer depth
- particulates - absorb and scatter light
16
Q
ingestion rate vs prey concentration
A
total ingestion also increases as predator concentration increases
ingestion increases as the prey concentration increases (up to some maximum - saturation)
17
Q
trophic transfer efficiency
A
production rate at trophic level below
OR
biomass at trophic level below
18
Q
Suppose a primary production rate of 100 mmol C m-2 d-1 and a trophic transfer efficiency of 15%.
What production can you expect at the third trophic level (secondary consumer)?
A
19
Q
how does phytoplankton size control top level biomass?
A
- loss at each trophic level (trophic transfer efficiency)
- lower biomass at phyto level
- small phyto = characteristic of nutrient limitation
- larger phyto = dominate at more nutrient rich systems
smaller phyto = more trophic levels = less biomass
20
Q
how is trophic production linked to primary production?
A
Higher trophic production linked to primary production
21
Q
copepods
A
v abundant ~80% net samples
key link of phytoplankton to higher trophic levels
eats large phytoplankton (herbivorous) and small zooplankton (carnivorous)
sexual reproduction
22
Q
generic copepod life cycle
A
generation time:
- several weeks to several years depending on species and environmental conditions
nauplii:
- v diff shape than adults
- less ability to sense environment than adults –> less successful predators
- smaller
- weaker swimmers
- less sensory ability
nauplii hatch in early spring to summer bc high phyto population and therefore easier to feed - more encounters and promotes high growth
adults then go down to depth bc theyre better at feeding can survive low food availability and allows for less predation
- enter diapause where slow respiration in cold deep waters
23
Q
Why is this an advantageous timing for the copepod life cycle?
A
the timing of blooms makes it important for them to be hatched right at spring bloom
- since they are worse at finding food, this allows for greater success
you look cute w your glasses on.
24
Q
importance of diversity in migration timing of copepods
A
advantageous for them to come up at different times bc then theres some diversity in case blooms are different timing
- not all population follows same exact schedule
- spring bloom timing variable (mixed layer shoaling depends on weather
- diversity in migration and egg production timing to ensure some nauplii are born at optimal period
25
What advantage does a planktonic stage give a benthic organism?
planktonic larvae promotes DISPERSAL with currents to other regions
an example: barnacle nauplii
26
euphausiids - krill (crunchy)
large
shrimplike
eats large phytoplankton and small zooplankton
multi-year life cycles (up to 5 years)
DVM
27
What is the advantage to organisms that live at depth during daytime and rise to the surface at night?
Diel Vertical Migration — DVM
1. predator avoidance - lots of predators are visual, so less chance of being eaten when not seen
2. feed where plankton biomass high at night
28
how does DVM vary by season?
different day lengths so there would be different pressures -- maybe not as much pressure to go up and down
this would change what organisms we see in deep net tows vs shallows
29
Amphipods (crunchy)
laterally compressed / flatter than euphausiids
eats detritus almost exclusively
direct development (no nauplius)
often live commensally within large jellyfish
30
Ostracods – seed shrimp (crunchy)
Primary sense – touch (water movement)
Eats large phytoplankton and small zooplankton
31
Cladocerans – water fleas (crunchy)
Antennae used for swimming
Largely eats detritus
32
Pteropods – a Mollusc (Crunchy)
Spend full life as plankton
look like small snails
foot has evolved into paired wings for swimming.
Most common in our samples Limacina spp.
thin, sinistrally coiled (to the left) calcareous shell
feeds by secreting a sticky mucus web
aragonite shell
- maybe most effected by ocean acidification?
33
Larval gastropods (Crunchy)
Plankton larvae
Benthic adults
Also look like small snails
thin, dextrally coiled (to the right) calcareous shell
Typically much smaller than local pteropods
34
Chaetognaths (Soft)
Carnivorous raptorial feeders
Attack plankton several times their own size
hang motionless until prey detected
use spines and hooks to grab prey
diel vertical migrators
Hermaphroditic
35
Larvaceans a primitive chordate (Soft)
Looks like a small tadpole
Secretes a mucous “house” through which water is pumped.
Food particles sieved out
When filter clogs, house abandoned and new one secreted
Old “houses” are important food source for other zooplankton and bacteria
36
Jellies - gelatinous zooplankton (Soft)
diverse collection of species from several different phyla:
Cnidarians (i.e. true jellyfish) and Ctenophores (i.e. comb jellies) both “fish” for smaller zooplankton with tentacles
Salps (primitive chordates) are filter feeders that form dense patches
37
Ctenophores - sea gooseberries
ctenophore tentacles are equipped with sticky cells called colloblasts
Typically up to 1 cm
Most feed on zooplankton, but some specialized to feed on other ctenophores
38
Although sometimes referred to as “the insects of the sea”, why are only 13,000 copepod spp compared to at least 1M terrestrial insect species?
not as much diversity in the environment as terrestrial
marie population more connected than terrestrial
39
reynolds number
at Re<100 viscous forces dominate (phytoplankton) - corn syrup
at Re>200 inertial forces dominate (like us) - air
40
how to swim at low reynolds number ?
have to use non-reciprocal propulsive force - like a flexible oar or corkscrew
cant do like boat w oar cause would keep going back & forth
41
how to catch prey at low reynolds number ?
copepods use complicated series of non-reciprocating movements - feeding appendages “fling and clap” strategy
no 2 pairs do the same thing
42
movement (escape response) vs feeding
two geared system of swimming appendages
non-reciprocating movement of feeding appendages - for slow cruise swimming and food capture
escape responses generate an order of magnitude more than any animal on earth
43
What is patchiness in copepods and what drives it?
Plankton are not perfectly spread out
- can be:
* patchy (clumped) distribution
* uniform or even distribution
* random distribution
Patchiness is caused by physical and biological processes
PHYTO - non motile so caused by physical mixing, turbulence, OR biological such as blooms or temps
ZOOP - driven by behaviour and biology - physical can contribute but since they’re motile mostly BEHAVIOURAL dominate zoop patchiness - can be driven by phyto conc in certain areas bc wanna be where phyto are to feed
zoop more patchy - also do DVM so this effects it too
44
Do all species of zoop do same DVM?
No, varies between diff types of zoop
Lots of diff behavioural patterns
45
What are 2 phenomenon that causes concentrations of plankton in ocean
WINDROWS
- Plankton concentrate in convergence zones between rows
- Divergence zone will be clear - convergent zones will hv high conc of plankton
FRONTAL ZONES
- when 2 water masses come together
46
Different scales of patchiness
Microscale, mesoscale, macroscale
47
Problems w net sampling
Nets don’t catch everything - larger zoop avoid nets, one mesh doesn’t work for all
Patchiness
Nets get clogged
48
Velocity of water in front of net
Bow wave
Caused by small mesh size - doesn’t let water thru fast enough
49
What role do heterotrophic bacteria and viruses play in the ocean ?
Play important role in carbon cycle
- utilizing, respiring, and remineralizing organic matter exported from surface to deep ocean
90-95% of marine bacteria are heterotrophic ↳ 70% of all living carbon in the ocean
- 20% of all bacterial biomass turns over everyday
50
What dominates the flux of energy and biologically important chemical elements of the ocean?
Microbes - bacteria (heterotrophs), viruses (phases, animal viruses), and protists
- total mass of bacteria in ocean exceeds combined mass of fish and zoop
- high metabolic rates
- turnover of carbon - 20% of bacterial mass turns over every day
51
Highest to lowest bacterial cell density environments and why
- estuaries, deep sea, open ocean, coastal (near shore)
1. Estuaries
2. Coastal (near shore)
3. Open ocean
4. Deep sea
Estuaries have stuff from land - high oxygen and particles for bacteria to break down
Coastal ecosystems have terrestrial influence as well
Deep sea is vast so less density compared to other areas
52
What happens to the bacteria in the ocean?
- Consumed by other plankton → heterotrophic or microzooplankton
- lysed by viruses
53
How is bacteria and their graces similar to phyto and zoop?
Fight coupling between bacterial and their grazers
54
What do heterotrophic marine bacteria eat?
DOM → organic matter that passes through a 0.45um filter
- DOC → dissolved organic carbon (main component of DOM)
55
What is DOM and where does it come from ?
Defined at organic molecules that pass thru at 0.45um filter - mostly dissolved organic carbon
Come from:
- phytoplankton exudates
- excretory products from marine organisms
- viral lysis of of host cells
- sloppy feeding by zoop and protozoans
- sinking zoop faecal pellates
- larvacean houses
56
Steeles Dilemma
57
What are the ecological roles of heterotrophic bacteria in the marine environment?
1. Recycling of nutrients
- breakdown of DOC and turn back into inorganic nutrients to the water column
2. Increases overall food chain efficiency
- microzoop consumes by mesozoop
- helps resolve steeles dilemma by providing a way to channel “bacterial carbon” back into classic food chain
58
Where are marine viruses most abundant & why?
In upper 200m of water column
Cause this is where their host cells are - heterotrophic bacteria
59
Ecological roles of viruses in marine environment?
1. Recycling of nutrients (indirectly)
- remineralization/respiration of lysed cell contents by bacteria
2. Regulation of primary productivity
- viral outbreaks may regulate phytoplankton blooms
3. Other roles:
- source of mortality
60
Recycling takes place on different time scales
1. In the euphoric zone and water column (relatively rapid, seasonal)
2. In accumulated sediments (slower, up to geological time frame)
61
Where does this reaction (remineralization/aerobic respiration) take place in the ocean ? Why ?
As long as there is oxygen, this can happen
Out of euphotic zone nitrification happens (deeper
62
What is the point of nutrient recycling in marine environments ?
- increases the productivity of food webs
- enhances and extends phytoplankton productivity
- influences composition of phytoplankton assemblages
- is a key component of the microbial loop
- works with other biotic and abiotic processes to form biogeochemical cycles
63
What are the sources of N to phytoplankton?
NH3, NH4+, NO3-, NO2-, urea, amino acids, other DON and N2
N2 most abundant, but only some cyanobacteria can use it directly
64
How is nitrogen assimilated?
Assimilation of N into amino acids requires complete reduction of the N compounds
Although phytoplankton can take N as NO3- , NO2-, urea, etc, they must first reduce these compounds to NH4+
65
If provided with a mix of N compounds, which would be preferentially utilized by phytoplankton? Why?
NH4+ would be chosen bc the reduction usually requires ATP
66
Nitrogen Cycle
• Remineralization occurs throughout the water column, but with different outcomes:
- • Regenerated production:
Portion of primary production that results from the utilization of
"regenerated nitrogen" (mainly NH4+,
urea
- • New prpduction:
Portion of primary production that results from the utilization of "new nitrogen" (mainly NO3-)
- • Role of DON:
Contributes to regenerated production AND to new production
67
Phosphorus Cycle
• Phosphorus in organic material is readily respired back to inorganic P.
• P rapidly cycles through the system, so, it is seldom limiting in the marine environment.
68
Silicon Cycle
• Only involves inorganic forms!
• Dissolution of biogenic Si is solubility driven. The ocean is undersaturated with Si, and therefore corrosive to biogenic Si.
• Skeletal material dissolves at all depths following death of the organisms and decay of organic material
• ~1/3 of material may reach sediments, only ~5% preserved
69
why is iron important to phytoplankton ?
1. photosynthesis
2. nitrogen assimilation
- used in synthesis of nitrate reductase (one of enzymes used to convert NO3 to NO2 to NH4+)
- nitrogenase enzyme is used for N2 gas fixation by cyanobacteria
3. synthesis of chlorophyll a
70
where does iron come from ?
sources of iron in the ocean:
- dust from atmosphere
- hydrothermal vents
- margin sediments
71
what is HNLC and where
High Nutrient (nitrate) Low Chlorophyll regions
- Subarctic NE Pacific
- Eastern Equatorial Pacific
- Southern Ocean
72
old Iron Hypothesis
“Antarctic Paradox”
the growth of diatoms is determined by factors other than the conc of phosphates and nitrates besides light and temperature
73
modern Iron Hypothesis
1. Fe not very soluble in oxygenated seawater - and much of the ocean is far from terrestrial sources
2. open ocean iron conc is very low and limiting compared to macronutrients
3. bottle experiments showed Iron stimulated growth of large diatoms and led nutrient drawdown
4. indirect evidence from “island effects”
74
early shipboard bottle incubation experiments
seawater spiked with Fe and incubated on deck
with iron it doubled or tripled
another study by Martin et al found similar results of experiments in Antarctica, Alaska, and Equator
— this suggested that iron was INDEED LIMITING phyto growth in these regions
indirect evidence -
NATURAL : dust blowing from Saharan desert caused high Chl plume - biological pump
75
biological pump
76
positive feedback between dust flux and global climate
• Fe rich dust entering the oceans
—> Increases PP
—> Decreases CO2 in atmosphere
• Temperature decreases
—> decreases precipitation
—> increased desertification
—> more dust
77
what provided evidence suggesting that Fe supply may affect atmospheric CO2 concentration ?
The Vostok Ice core (Antarctica)
78
Despite these lines of evidence, many oceanographers still questioned the importance of Fe in the regulation of primary production:
1) Artifacts associated with bottle experiments hinder extrapolation to ocean temporal and spatial scales
2) Bottle experiments are not acturate representations of a true phytoplankton community
3) Possible Fe contamination or improper analytical technique could lead to faulty conclusions
79
Advantages and disadvantages of large scale Fe hypothesis testing
advantages:
- significant increase in Chl
- drawdown of CO2
- suggest reversing anthropogenic caused climate change
disadvantages:
- possibly alter natural cycles, wiping out fish bc too productive of oceans (eutrophication)
- other problems we dont know yet
can study this naturally w volcanoes
80
what does the natural Fe fertilization event show ?
volcano eruption brought iron and blooms
showed that bad effects could be minimal
australian wildfires fertilized bloom - may hv drawn down lots of carbon from atmosphere
81
Did the Kasatochi bloom event affect Fraser River sockeye salmon?
suggests that bloom caused way more salmon to return
also after commercial vessel released iron sulfate, 2014 has 20 milliom sockeye return to fraser
82
What limits productivity in three different locations ?
(subarctic NE Pacific, North Atlantic, subtropical N Pacific) LOOK AT THIS AGAIN
Subarctic NE Pacific (Ocean Station Papa) - seasonal light changes
North Atlantic - similar latitude and similar light difference between seasons
-
Subtropical Pacific - light varies much less
83
Which size class of phytoplankton are likely responsible for the occasional peaks in chlorophyll ?
84
What kind of phytoplankton are good at dealing with low nutrients?
Small spheres are best bc they can use ammonium directly at low concs
Large phytoplankton need higher concentrations
Larger diatoms in Subarctic NE pacific can only take up higher concs of NO3- BUT require Fe
85
Why is the biological pump important ?
- sink for atmospheric carbon
- important for connecting nutrient cycles
- Pathway for organic matter to reach sea floor ecosystems
86
Would atmospheric CO2
87
How might climate change affect the biological pump ?
Ocean acidification - shells CaCo3 susceptible to dissolution - less efficient sinking
Temperature
- warmer water can hold less dissolved gas (CO2)
- ice coverage and timing of grazing
- stronger stratification- warmer water less dense
- less nutrient renewal
