Marine Communities Exam 1

study guides from slides + additional notes.

Study Guide for Lecture 1

•Know steps of scientific method in order. 

•Understand basic experimental design.  Be able to identify controls and design an experiment.

•Be able to differentiate good vs. bad hypotheses

•Differentiate between common use of the term theory and scientific theory

•Differentiate science from pseudoscience

•Describe each of the vertical and horizontal divisions of both the benthic and pelagic zones of the ocean, giving their boundaries and basic characteristics.

Earth’s surface is 71% dominated by ____?

oceans

What industries are based on marine organisms? What ecological services are provided?

Fisheries, tourism, pharmaceuticals.

Hurricane buffers, water filtration, carbon sinks

What are the steps in order of the scientific method?

Make an observation

Ask a question

Develop a hypothesis (needs to be testable and you can get data from it)

Experimental Design

Good experimental design pairs…

field experiments with lab experiments

T/F Every study is flawed.

True

T/F Science can prove.

False. “Science never proves.”

What are the 3 R’s of experimental design?

Randomisation: the random allocation of treatments to the experimental units. Randomize to avoid confounding between treatment effects and other unknown effects.

Replication: the repetition of a treatment within an experiment allows: To quantify the natural variation between experimental units. To increase accuracy of estimated effects.

Reduce noise: by controlling as much as possible the conditions in the experiment. A classical example is the grouping of similar experimental units in blocks. Using known characteristics/properties of the experimental units to explain variation, for example inclusion of block effects in the statistical model.

A non-falsifiable hypothesis is called ____.

pseudoscience

Our everyday usage of the word theory is analogous to the scientific term ____.

hypothesis

What is the order of oceans from largest to smallest?

Pacific, Atlantic, Indian, Arctic, Southern

Review thermohaline circulation

Why is Europe not as cold as Canada?

Gulf current of warm water

_____ is

• broad, low sloping (1:500 grade) platform at the margins of continents

• Extends from a few km (California) to 400 km (Newfoundland); mean ~ 200 km

• ~ 8% of the total ocean but very productive

Continental Shelf

_____

• extends from shelf to deep sea

• grade is 1:20 

•may be dissected by submarine canyons

Continental Slope

______ is

• flat, featureless plain of deep ocean

• most of ocean floor is abyssal in depth

• most common habitat on earth

Abyssal Plain

Can canyons have turbidity flows?

yes

Know the order of the zones.

Epipelagic (sunlight zone)

Mesopelagic (twilight zone)

Bathypelagic (midnight zone)

Abyssopelagic (the abyss)

Hadal (the trenches)

Study Guide for Lecture 2

 Explain how temperature and salinity can alter sea water density.  What causes variation in salinity?

 Define and explain halocline, thermocline, pycnocline.  Be able to interpret depth profiles.

 Explain differences in seasonality of stratification between tropical, polar, and temperate waters. How does latitude, formation or dissolution of sea ice, and river input affect salinity?

 Why do water bodies stratify, and why is it ecologically important? How does stratification frequency vary with latitude?

 Graphically indicate the distribution of temperature, water density, salinity, oxygen, and nutrient availability across a thermocline.

 Where are hypoxia/anoxia more common – surface waters or deeper waters?  Why?  Why is hypoxia more common in the summer in temperate zones?  What is a dead zone, what causes it, and why are they so hard to contain? In addition to anthropogenic addition of fertilizers that increases phytoplankton blooms, what natural processes help to make the Gulf Hypoxic Zone?

 Describe how convergence zones, salinity, surface currents, and upwellings all contribute to thermohaline circulation of water through all of the world’s ocean basins.

 Where are upwelling zones common and what effects do they have on coastal ecosystems?

Upwelling

Continental shelf

global conveyer belt

salinity

Interface with changing temperature

thermocline

Because fresh water “floats” on top of denser, saltier water, a ____ is generated when fresh water is released on surface by

melting sea ice

large river input

(interface with changing salinity)

halocline

Interface with changing density

Pycnocline. Where you have a thermocline you’ll have a pycnocline. Where you have a halocline you’ll have a pycnocline.

________ use electrolyte properties to measure conductivity, temperature, and depth from ships. Cl, Na (about 85% Na and Cl), S, Mg, Ca, K are the most common elements.

CTD probe

Normal Ocean seawater is 35 ____

ppt (parts per thousand)

parts per thousand / one way salinity is measured

⁰/₀₀

separation. 3 water layers form.

stratification

O₂ minimum zone

Low dissolved oxygen in water

hypoxic zone

Some seas are always hypoxic on bottom; some only during stratification; some never.  Becoming more common with increasing levels of nutrient pollution.

Northern Gulf of Mexico Hypoxic Zone is largest studied.

Coriolis effect

trade winds

gyre

thermohaline circulation

rip currents

What controls salinity?

If evaporation > precipitation, the salinity in a bay would…

increase

Where rivers and streams meet the ocean. Salinity is ___ than 35 parts per thousand?

estuaries

lower

Normal ocean seawater is __ parts per thousand

35

When ice forms, salinity of surrounding water goes….

up

Salt is not incorporated into ice crystals. When sea ice melts, fresh water is released and salinity of surrounding water goes down.

Water density __ with increasing salt content and salty, heavy water sinks

increases

In surface waters, evaporation ___ salinity. Rainfall and runoff from rivers ___ it.

increases

decreases

Bottom water and sediments are often ___ in salinity and less variable than surface waters (bottom water is more stable)

higher

T/F Surface layer of water is mixed by the wind.

True. Mixed layer

In shallow temperate bays, continental shelf or temperate open ocean, stratification starts in ____ and ends in ___ with increased wind and lower temps.

spring

fall

surface mixing is limited to __-__ m

20-40

Tropical oceans mixed by warm temp and winds to about 100-500 m, stratification is nearly ____

permanent

When stratified density (and/or temp and salinity) varies with depth, density differences prevent ____ ____?

vertical mixing

Does stratification influence distribution of plankton and chemical factors?

Yes

T/F Surface waters of the open ocean are often nutrient starved

true

Deeper water will have less _________ (light limited), higher _____ (more free nutrients)

photosynthesis

decomposition

Concentration of oxygen is ___ in deeper waters.

less

 Stratified, no mechanism to replenish bottom-water oxygen

 Bacterial demand for oxygen for cellular respiration is high (organic matter from surface sinks and is decomposed), reducing oxygen content

Sediment surface; on the sea floor

benthic

Which season would have the most benthic hypoxia?

Summer; more strongly stratified water column; increased decomposition (microbes metabolic rates ramping up, respiration rates ramping up, and consuming more oxygen)

In a stratified body of water, dissolved oxygen levels will be

higher above the pycnocline. High dissolved oxygen on the surface can be due to photosynthesis, diffusion from the air. There is more respiration below the pycnocline and uses more oxygen.

Do algal blooms stay at the surface?

No, they sink below the pycnocline and decompose. Extra nutrients cause algal blooms, but the algae sinks. More organic material to decompose, which uses up more oxygen and causes hypoxia.

Know the steps in this diagram.

What can mix the water column?

Hurricanes/tropical storms