Aquariums – Miniature Oceans (part 1)

The main goal • To highlight a few of the versatile ways

aquariums can be used in the classroom to demonstrate fundamental concepts in biology, chemistry, and earth science

• To show the utility of having an aquarium in the classroom is that there is a “one-time” cost in which you can refer to over the course of the year to help leverage lesson plans

What are the main components of an aquarium? How to replicate the oceans?

• Light• Water movement• Filter (what makes a

good filter and why)– Chemical– Physical– Biological

• Salt (depends on the system)

• Research, Research, ResearchIn other words: habitat

recreation

SalinityDIY hydrometers and Salt Mixing

• To introduce students to a major property of seawater

• Encourage students to relate chemical properties (i.e. ion concentration) to physical properties (i.e. density)

• Illustrate a simple method to harness physical properties of seawater to estimate a chemical parameter, salinity

Goals

SalinityHow much salt is there in 1 kg (1L) of seawater? What are the chemical components of salinity?Na+, Cl-,Mg2+, Ca2+, K+, Sr2+, Br-, F-, I-, SO4

2-, HCO3

-, BO33-, SiO3

2-

How do these ions get concentrated in the oceans?

Weathering of rock by rain removes ions from the land, rivers bring them to the oceans, evaporation removes fresh water leaving the ions (salt) behind in the ocean basins

3.5% or 35 ppt (‰)

How do you think warming will affect salinity based on this simple diagram?

Salinity – Why is it important?

• Key driver of ocean density– What are the implications?

– Impacts microbial communities

– How can this be influential in the oceans?

• Sensitive to Climate Change– How could global warming influence

surface salinity?

Stratification, defining oceanographic regions

Impact Biogeochemical cycles, alter food web dynamics

Increased evaporation could increase salinity at the equator or at polar regions increasing freshwater from melting ice could decrease salinity

Activity 1 – Make and calibrate hydrometer

• Fill Clear bottle with enough sand to keep it floating vertical (~1/4 full)

• Place bottle in saltwater of known salinity

• Take bottle out of water and use marker to mark the water line* and write the known salinity

* You may need to adjust the amount of sand to achieve a workable waterline

Activity 2 – Mixing Saltwater

• Collect 8L of water

• Add 240g or ~ 1 cup of salt

• Mix

• Check Salinity with your homemade hydrometer

• Is it higher or lower than your calibration mark?

8L water+

~ 1 cup salt

Salinity – Follow up

• What physical property are we using as a proxy to check a chemical parameter of seawater?

• How will you be able to tell if you need to add more salt or more water to your freshly mixed salt based on your hydrometer reading?– If the mark is below the water line? – If the mark is above the water line?

Density

Salt, why?Water, why?

Nutrient Testing

Goals– Challenge students to draw connections between

water chemistry and biological activity– Introduce students to simple tests for measuring

nutrients and water column diagnostics – Familiarize students with the major nutrients in

ocean ecosystems

Testing nutrients between heavy bio-load and light bio-load systems

Microbes and Chemical Cycles• Microbes are everywhere

• They are not all bad, in fact many of them carry out critical ecological functions that keep environments healthy

• 1mL of seawater can harbor 100 of thousands to millions of microbes

• Crucial link between chemical energy and higher trophic levels in food webs

Microbial Filter – Moving Nitrogen

Fish + food

NH3 + NH4+

(Fish waste)

NO2-

(Bacterial waste)

NO3-

(Fertilizer for primary productivity)

O2

O2

Ammonia Oxidizers

Nitrite Oxidizers

How does this process differ in oceans?

It only differs in that it is half of the cycle. The other half if carried out in sediments or low oxygen water columns.

Why is it important to remove these nutrients from the aquarium?

What compounds are toxic to fish and inverts?

Ammonia/Ammonium(NH3/NH4

+)&Nitrite (NO2

-)

Why are these compounds toxic?

Ammonium disrupts neuron charge balance

NH4+

NH4+

NH4+

NH4+

NH4+

Nitrite irreversibly binds to the iron hemoglobin, preventing oxygen utilization

Activity 1 – Nutrient Testing• Collect 15mL of water from

each aquarium • Following the instructions on

the kit• Dip the test strip into the

water sample• Check the strips against

color key on kit• Record values from each test• Plot the values on the graph

proved

By looking at the systems, which one do you think will have higher nutrient concentrations?

Activity 1 - Questions

• Are these healthy levels compared to pristine reefs?

• What factors may influence these differences? What are consequences

• Why do the tanks differ?

• Predict how the nutrient concentrations will change over time? What could be mediating these changes? Natura

l Reef

Light B

ioload0

2

4

6

8

Ammonia (NH3)

Conc

entr

ation

(ppm

)

Natural R

eef

Heavy Bioload

Light B

ioload0

2

4

6

8

10

Nitrite (NO2_ )

Natural R

eef

Heavy Bioload

Light B

ioload0

20

40

60

80

100

Nitrate (NO3_)

Values in ppmChemical Natur

al reefHeavy

bioloadLight

bioloadAmmonia (NH3/NH4

+) 0.2

Nitrite (NO2-) 0.5

Nitrate (NO3-) 1.2

Activity 2 – Gram stain bacteria

Goals– Challenge to students to think about

microorganisms in seawater– To understand linkages between nutrients and

microorganisms– Introduce simple methods for visualizing bacteria– Introduce students to microscopes

Activity 2 – Gram stain bacteriaBased on activity 1, which system should have a more dense bacteria population?

• Take 0.5 mL of water from each tank with disposable pipette• Place a thin, dime size amount water on slide.• Allow to air-dry• Pass the smear through a flame 2-3 times to heat-fix.• Gently flood the smear with crystal violet and let sit for 1 minute.• Gently rinse with water.• Gently flood the smear with Gram’s iodine and let sit for 1 minute.• Gently rinse with water.• Tilt the slide and drop Gram’s decolorizer on the smear drop by drop until it runs almost clear.• Gently rinse with water• Gently flood the smear with Safranin and stain for 45 seconds.• Gently rinse with water• Blot dry• View under microscope using the 40X objective.• To view samples at 100X, first focus in using the 40X objective; then rotate the objectives so that the

40x objective is out of the way, but not all the way onto the 100x objective.• Add a drop of immersion oil over the center of the hole where the light is coming through the slide,

and then rotate the 100x objective into place.• Use the fine focusing knobs to focus in, but be very subtle, because even the slightest slip can cause

you to overshoot the depth of focus for the specimen

Activity 2 – Gram stain bacteria• How do microbes in the environment

differ from those in culture?

• Do you expect there to differences in lifestyle strategies between different niche spaces?

Less dense, smaller, slow growing…

Much like macrofauna, microbes exhibit different strategies to live in very diverse environments: free living, aggregate forming or particle associating, biofilms, migrating, symbionts