Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biological Oceanography > The Role of Light > Flashcards

The Role of Light Flashcards

1
Q

Why does solar radiation vary with latitude and seasons

A

Sun Angle: Varies with latitude, time of year and time of day
Very high reflectance when sun angle is below 5 degrees

Length of day

Atmospheric Conditions

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Scattered Light

A

Light reflects or bounces off particles/molecules so we can see them

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Absorbed Light

A

Absorption by molecules of water to heat (Infrared)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is the impact of absorbed and scattered light

A

Absorbed light used for photosynthesis
Scattering and absorption effects the quantity/quality of light available

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Solar Energy Percentages Ocean

A

50% absorbed, reflected and scattered in the atmosphere

50% absorbed/scattered in the first ~10m – UV scattered and IR absorbed

50% penetrates (visible light) to about 1000m and decays exponentially with depth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Coastal vs Open Ocean Light Profiles

A

More scattering and absorption when more particulates in coastal waters. Less in open ocean
Coastal waters have green shifted light profiles from sediments
1% surface light at 10m in Coastal and 100m in open ocean

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Light Exponential Decay

A

ID = IOe^(-kD)

ID = irradiance at depth (micromol photons/ms)
IO = irradiance at the surface (micromol photons/ms)
k = light extinction coefficient 1/m
D = depth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Light Extinction Coefficient

A

Describes how rapidly light is attenuated
k is higher in coastal waters
Composed of 3 terms: kw (water), kp (particulates) and kd (dissolved)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Two Ways to Measure k

A

PAR Sensor: Record light intensity directly at surface and at depth (k = ln(Io) - ln(ID) / D)
Secchi Disk: White circular disk lowered until not visible, that depth is Ds (k = 1.7/Ds)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Main Characters of Phytoplankton

A

Unicellular microscopic photoautotrophs
Very small in size
Most have a hard outer covering
Many are eukaryotic
Both prokaryotic and eukaryotic forms have thylakoids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Role of Phytoplankton in Marine Ecosystems

A

Primary producers in marine ecosystems
Form base of virtually all food webs
Represent available energy for transfer up the trophic pyramid
Form extensive blooms, can be toxic
Influence atmospheric and aquatic chemistry (produce O2, CO2 drawdown and C export, cloud formation)
Oil and sediment deposits
Major impact on global climate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Four Major Groups

A

Cyanobacteria
Diatoms
Coccolithophores
Dinoflagellates

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Cyanobacteria
Two Main Groups

A

Prokaryotic
Coccoid: Discovered first because of bright orange phycoerythrin fluorescence
Prochlorophytes: Discovered later because of its dim red fluorescence
These two groups make up a major fraction of phytoplankton in ocean

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Trichodesmium

A

N2 fixer and colonial or free-living filaments
Form large blooms and surface aggregationsDia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Diatoms

A

Have silica dioxide frustule
Single cells or chains of cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Two Groups of Diatoms

A

Centric: Radial symmetry and pelagic
Pennate: Bilateral symmetry and benthic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is a frustule made of

A

Made of silica and two valves (epitheca and hypotheca)
Raphe: elongated groove in frustule – excretes sticky stuff

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Where are diatoms most productive

A

In areas of upwelling

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Diatom sediment

A

They make silica sediment called diatomaceous earth found on sea bottom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Psuedonitzschia

A

This is a diatom that forms large toxic blooms off our shores
Domoic acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Coccolithophores

A

Unicellular or colonail
External body scales (coccolith) CaCO3
May have flagella
CO2 produced in calcification is used in photosynthesis

22
Q

Coccolithophore vs Diatom Bloom

A

Diatom blooms appear very greenish-brown, whereas Coccolithophore blooms are milky white and blue

23
Q

Coccolithophore affect on climate

A

They produce dimethyl sulphide (DMS) which helps to form clouds and reduce solar radiation and cool planet

24
Q

Coccolithophore sediment

A

Produce white chalky sediment
Calcareous sediments

25
Q

Dinoflagellates

A

Unicellular ovoid shape
Can have 2 flagella rotary swimming motion
May have theca made of cellulose plates
Coral symbionts

26
Q

Nutritional Modes

A

Obligate Heterotrophs
Facultative Heterotrophs
Obligate Heterotrophs

27
Q

Protoperidinium

A

Dinoflagellate with a Sticky veil called pallium to digest prey

28
Q

Noctiluca scintillans

A

Naked dinoflagellate uses tentacle to capture prey

29
Q

Harmful Algal Blooms

A

Large aggregations of dinoflagellates
Some produce saxitoxin that is harmful to animals
Cause PSP

30
Q

Bioluminescence

A

Some dinoflagellates flash in response to mechanical, temperature or chemical stimulation

31
Q

Burglar Alarm Hypothesis

A

Dinoflagellates get eaten by Mysids, but when they flash their light they attract cuttlefish which come and eat Mysids

32
Q

Chl a Absorbtion

A

Peaks at 450 and 660 nm

33
Q

How do phytoplankton absorb more wavelenghts

A

Use accessory pigments to broaden the absorption, but all energy is still directed to Chl a to be used in photosynthesis
Cyanobacteria has most accessory pigments
All phytoplankton will have Chl a

34
Q

Methods for Measuring Chl a

A

In Vivo and In Vitro fluorescence
Remote sensing with satellites

35
Q

In Vivo Fluorescence

A

Flow through fluorometer towed behind ship, emits blue light, causes Chl a to emit red light and this intensity is measured

36
Q

In Vitro Fluorescence

A

Sample seawater from various depths, filter known volume and extract Chl a. Measure in fluorometer

37
Q

Remote Sensing with Satellites

A

Convert images of ocean colour into estimates of Chl a
Depth of 5-25 m

38
Q

Photo-Inhibition

A

As irradiance increases so does production up to a point then it decreases

39
Q

Light Saturation

A

As irradiance increases so does production up to a point then it levels off

40
Q

Compensation Irradiance

A

The irradiance where photosynthetic rate is equal to respiration rate

41
Q

Euphotic Zone

A

Where there is just enough light for photosynthesis to balance out the respiration rate, also known as the compensation depth

42
Q

Compensation Light Intensity

A

Amount of light at the base of euphotic zone

43
Q

What causes variability in light quality in the ocean? And how do phytoplankton deal with it ?

A

So as light is absorbed and scattered different wavelengths are left behind. This happens with depth or due to particles or organs. Phytoplankton use accessory pigments to absorb many wavelengths across the PAR.

44
Q

Station A had k = 0.28 and station B had k = 0.14 with a surface irradiance of 1900 at both. How deep is euphotic zone at each, and why does this make sense.

A

A: 16.5m
B: 32.93m
Station A is near the coast with lots of FW. More sediment and particles that cause light to attenuate faster

45
Q

What colour of light are phytoplankton not absorbing? What might this tell you about the colour they appear to our eyes.

A

They are not absorbing greens and yellows
They reflect these colours so that is why they appear green, yellow or brown to our eyes.

46
Q

At what time of year would you expect the depth of the surface mixed layer to be the greatest in the middle of the pacific? Why?

A

In the winter. Because the depth of the mixed layer is controlled by the stability of salinity, temperature and density of the water.

In the winter there is no large FW input to alter the salinity and temperature a great deal, and the ocean temperature is fairly consistent with the lack of sunlight.

47
Q

Explain the difference between compensation depth and critical depth

A

The compensation depth is the depth where the amount of light (compensation light intensity) is just enough for photosynthesis to balance respiration. This is the base of the euphotic zone.

The critical depth is where the average light intensity above it is equal to the compensation light intensity

48
Q

While out on a research cruise in the Subtropical North Atlantic, you conduct a TD cast that includes measurements of light intensity through the water column. You measure a surface irradiance of 450 uE m-2 s-1. From the vertical profile of temperature, you see that the mixed layer depth is 120 meters.
You use the vertical profile of light intensity to calculate a light extinction coefficient of 0.12 m-1 and from bottle incubations for primary productivity determine that the compensation light intensity is 45 umol photons m-2 s-1. Based on these measurements, do you expect there to be a phytoplankton bloom at your sampling location?

A

We know:
IO = 450
IC = 45
k = 0.12

Dcr = IO/(k*IC)
Dcr = 83.3
The mixed layer is 120 m and the Dcr is 83.3 m so there will be no bloom.

49
Q

A student in Biological Oceanography went on a field trip to Haro Strait on a cloudy day in early fall. When they arrived on station H3 in Haro Strait, they deployed the CTD and did a full profile of the water column to 150 m. After downloading the data, it showed a surface irradiance of 650 mol photons m2 s1, 50 umol photons m2 s1 at 23 m, and a distinct thermocline at 21 m.
The student completed their sampling of chlorophyll-a biomass and nutrients from depths in the upper 40 m of the water column (0, 5, 10, 20, 30 and 40 m), and then returned to the lab to analyze their samples. Before measuring the chlorophyll concentration, the student remembered reading a paper that provided a range of values for compensation depth in Haro Strait phytoplankton assemblages at the same time of year, with an average of 17.5 m.
1. Explain how you would solve this problem.
2. Should the student expect to see evidence of a bloom in their chlorophyll-a samples?
Justify your answer numerically.
3. Extension: Would there be any differences in biomass between depths? Explain.

A

What we know:

Io = 650
I23 = 50
Mixed Layer = 21 m

1) Solve for k = ln(Io) - ln(ID) / D
k = 0.11151953728

2) Solve for IC
IC = IO / e^Dc*k
IC = 92.4

3) Solve for Dcr
Dcr = IO / k*IC
Dcr = 63

The MLD is 21m and the Dcr is 63m so we would see a bloom.

49
Q
A
50
Q
A

Biological Oceanography (15 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions