Freshwater Ecology Lab Exam

Microcystis taxonomy (Kingdom, Phylum, Order, Genus)

Kingdom: Monera

Phylum: Cyanophyta (cyanobacteria

Order: Chroococcales

Genus: Microcystis

Volvox taxonomy (Kingdom, Phylum, Class, Order, Genus)

Kingdom: Protista

Phylum: Chlorophyta (Green algae)

Class: Chlorophyceae

Order: Volvocales

Genus: Volvox

Diatoms Taxonomy (Kingdom, Phylum, Class, Orders)

Kingdom: Protista

Phylum: Bacillariophyta (diatoms)

Class: Bacillariophyceae

Orders: Centrales and Pennales

Euglena taxonomy (kingdom, phylum, genus)

Kingdom: Protista

Phylum: Euglenophyta

Genus: Euglena

Paramecium Taxonomy (Kingdom, Phylum, Genus)

Kingdom: Protista

Phylum: Ciliophora

Genus: paramecium

Rotifera taxonomy (kingdom and phylum)

Kingdom: animalia

Phylum: rotifera

Daphnia taxonomy (Kingdom, Phylum, Subphylum, Class, Genus)

Kingdom: animalia

Phylum Arthrophyta

Subphylum: Crustacea

Class: Branchiopoda

Genus: Daphnia

Stentor taxonomy (Kingdom, Phylum, Genus)

Kingdom: Protista

Phylum: Ciliophora

Genus: Stentor

identify the organism

microcystis

identify the organism

volvox

identify the organism

diatoms

identify the organism

euglena

identify the organism

paramecium

identify the organism

rotifer

identify the organism

daphnia

identify the organism

stentor

what was the name of the site we sampled at for our field trip

sturgeon creek

hold time and purpose

• samples must be collected and brought to the lab within 48 hours

• the chemistry of the sample will change over time if not analyzed right away

• ice helps slow biological and chemical reactions

two types of quality control samples

trip blank and field blank

trip blanks

• sample of lab water is simply
  transported into the field and back, then analyzed

• results indicate if the bottles were cleaned properly in the lab

field blanks

• use lab water, but treat it as an regular sample

• sample its poured though all equipment and sample bottles first and will receive preservative if used for other samples

• determines if field techniques were done properly, if the preservative was contaminated, and if the air contaminated samples

Grab samples 

• into bottle: samples collected directly into bottles

• the bottle is inserted into the water open end down and turned horizontally to the current. Then its is turned upright while still in the water and brought up out of the water to be sealed

ways to obtain larger and deeper grab samples

Kemmerer, Van Dorn and Niskin samplers

lugol’s solution

preserves the samples when they can not be looked at quickly

what is a phytoplankton trawl net

• used to get non-quantitative samples of phytoplankton

advantages of phytoplankton trawl nets

• obtain a large sample of biomass in a
  short period of time

• can see a good range of the organisms present

disadvantages of phytoplankton trawl nets

• loss of small algae

• contamination with larger numbers of
  zooplankton, which selectively consume the algae

• particulate inorganic and organic debris that may have an associated bacterial population collected

• concentrated biomass leads to change in water quality during transport

peristaltic pump

• used to get large grab samples

• creates a vacuum to obtain sample

ways to obtain depth integrated samples

• iron bottles

• sampling tubes

• obtaining multiple samples at discrete depths and mixing them together to get a final sample using Kemmerer or Van Dorn samplers

how to avoid contamination of zooplankton in a phytoplankton trawl net

• you can use a larger mesh net inside a smaller mesh net

Schindler-Patalas Sampler (qualitative zooplankton sampler)

• water flows free through the clear box until desired depth is reach

• then doors on box are closed and the box is pull up out of the water

• water exits the box through the small mesh net, collecting zooplankton in the small bottle at the bottom

why take macrophyte samples

• contribute significantly to the productivity of freshwater systems

• provide substrates/habitat for other organisms

• influence thermal stratification by reducing mixing

• influence the oxygen content of the water because of their high photosynthetic rates

• work to stabilize bottom sediments

• excrete organic compounds that inhibit growth of phytoplankton and bacteria

ways to collect qualitative macrophyte samples

• by hand using wader

• double sided rakes

• Ekman dredge

• Louisiana box sampler

• Osborne frame sampler

determining macrophyte biomass

• (dry) weight of plant material taken from a unit of bottom area at a given
  time

• considered standing crop if bellow ground portions not included

• considered biomass if bellow ground portions included

Ekman dredge

• size used depends on organism density and sediment softness

• doors swing open to let water in as it is lowered into the water

• once at the bottom pull up one meter and let the dredge free fall so it penetrates the sediment

• then the messenger is released to close the jaws and retrieve the sample

• contents are then sifted with bucket with a sieve at the bottom

why take benthic macroinvertebrate samples

• diversity is generally high in stable environments with a balanced distribution of species

• Physical/chemical stresses can result in a shift in the community makeup, causing sensitive organisms to disappear, while tolerant species become disproportionately dominant

ways to obtain benthic macroinvertebrate samples

• Ekman dredge

• kick sampler

• tow nets attached to boats

• Ponar grab

• Peterson grab

sediment corers

• collect sediment samples for chemical analysis

• assess changes in sediment composition over time

• sediments are laid down annual like tree rings, providing a historical record

List of water quality parameters that need to be measured

• temperature

• dissolved oxygen

• pH

• conductivity

• light

stenothermic

adapted to a narrow temperature range

eurythermic

adapted to a wide range of temperatures

thermocline

thin layer in the water column where temperature
changes more rapidly with depth than the layers above or below it

why measure temperature

• some organisms are stenothermic or eurythermic

• impacts the amount of gases dissolved in water (ex: colder = more DO)

• impacts rates of chemical reactions

• presence of thermocline prevents mixing of nutrients between hypolimnion and epilimnion

epilimnion vs hypolimnion

epi - above thermocline

hypo - below thermocline

how is temperature measured

• thermistor thermometer

• The device is made of metals whose electrical resistance
  depends on temperature. A change in resistance to an electrical current
  indicates a change in temperature

• can be placed on a long cable so temperature can be read at different depths

why measure dissolved oxygen

• required for all animals in the water column, the benthos organisms in the substrate, and plants/phytoplankton

• many organism sensitive to dramatic DO changes

• fluctuates diurnally - added by photosynthesis during the day and consumed by respiration at night

• depends on depth, organic matter,  and sediment type

• depletes in the winter

how is dissolved oxygen measured

• electrometric technique (yellow springs instrument)

• based on the rate of diffusion of molecular oxygen across a membrane

• measure temperature as well

• probe can be attached to a long cable to take reading a different depths

how to measure pH

• based on the use of a pH sensitive glass electrode and a
  reference electrode (e.g. a silver chloride electrode) and a temperature
  element to provide a temperature signal to the pH analyzer (as pH is
  temperature dependent)

• the difference in the potentials of the glass and reference electrodes when placed in a solution provide a millivolt signal proportional to the pH

conductivity

• The electrical conductivity of water is the ability of water to conduct an electrical current, which is dependent on the concentration of ions it contains

• The greater the ionic concentration (dissolved salts etc.), the greater the conductivity

why measure conductivity

• greater concentration of dissolved ions = greater productivity

• provides a rough indication of the amount of total dissolved solids within the water
  

how to measure conductivity

• temperature dependent (increases 2-3 percent per increases degree of temp)

• measurement is made by a probe that uses two electrodes
  placed 1 cm apart, so the results are often reported as μmho/cm

why measure light

• provides energy for photosynthesis

• heats the water

• helps organisms see

• different wave lengths of light penetrate water at different depths

what does light penetration depend on

• angle the light is hitting the water at (the straighter the angle, the more is reflected)

• the types and sizes of waves

• material that may be on the surface of the water

extinction of light with depth is due to

• the water itself

• suspended particles (such as clay or phytoplankton)

• dissolved organic substances such as humic acids that colour the water

photic zone

depth to which 1% of the PAR penetrates the water

light compensation points

• When an organism is at their light compensation point their production rate
  equals their respiration rate

• if they fall below this level in the water column they
  will survive only until they use up their energy stores

surface inhibition

• organisms can be damaged at the direct surface due to high light intensity

• phytoplankton tend to be most dense at some point below the surface of the water

how to measure light

• photometer ( can be used to determine the depth of the photic zone by taking multiple readings at different depths

• secchi disk - The disk, tied to a calibrated line, is lowered
  into the water and the depth where it disappears is
  recorded. It is then lowered further another m and
  raised. The depth that it reappears to the observer
  is also recorded. The average of the first and
  second readings is the Secchi Disk Depth

why sample/ study plankton

• contribute oxygen to the atmosphere

• sensitive to various pollutants and nutrient inputs = changes occur in plankton before they are visible in larger organisms = bioindicators

• healthy ecosystem = diverse plankton

• unhealthy = little diversity and many undesirable plankton

• food source for larger organisms

Characteristics of genus Microcystis

• Unicellular but form globular colonies covered with a layer of mucilage

• for large blooms

• produce microcystins - hepatotoxins

• toxins releases upon cell death or lysis

general characteristics of all Cyanophyta

• prokaryotic (lack organelles but have granular inclusions)

• photosynthetic pigments associated with thylakoid membranes

• thin cell wall made of peptidoglycan and lipopolysaccharide

• optimal growth at high temperature

• tolerate low light and N:P ratios

• reproduction is vegetative - cell division and spore formation

• colonial or unicellular forms

different adaptations Cyanobacteria may have

• gas vacuoles

• heterocysts

• akinetes

• mucilage layer

• colony formation

• production of toxins

gas vacuoles 

• allow cyanobacteria to change their vertical position in the water column

• float down to obtain nutrients

• float up to obtain light for photosynthesis

heterocysts

• specialized cells that fix nitrogen

• have special cell wall layers that prevent oxygen from diffusing into the cell

• advantage in low nitrogen environments

akinetes

• thick walled spore-like cells

• able to survive harsh conditions

• ensure that an organisms genetic information is passed on

general characteristics of Chlorophyta class Chlorophyceae

• green color due to dominance of chlorophyll a and b

• unicellular, colonial, and filamentous

• microscopic and macroscopic

• motile and non-motile

• starch reserves stored in plastids

• eukaryotic

• planktonic and benthic

• rarely form blooms

morphology of diatoms

• yellow-brown color

• thick silica cell walls

• non-flagellate

• unicellular, colonial, or chains

• 2 shapes: centric (discoid or cylindrical with radial symmetry) and pennate (elongate with bilateral symmetry)

diatoms habitat preferences

• standing and running water

• planktonic, benthic, epiphytic, epizoic

• tolerant to low light and and low temperature

• form blooms in fall and spring

• well preserved in sediment

function of silica cell wall in diatoms

• aka frustule

• requires less energy to make than the other types of algal cell walls

• gives them a head start in spring

disadvantage of silica cell wall in diatoms

• the frustules are heavy and cause the diatoms to sink to the bottom of the water column

• require turbulence to to remain suspended

ways diatom colonies form

• mucilage pads - occur at the ends of cells, allowing them to join

• interlinking spines where where chains of cells are joined valve to valve

• gelatinous stalks - used to attach to the substrate and join small groups of cells together

Euglenophyta morphological characteristics

• unicellular with flagella

• anterior depression where flagella immerge

• have an eyespot

• surface coat/pellicle is flexible

• paramylon storage reserves

Euglenophyta feeding preferences

• 1/3 are photosynthetic - elongate, spindle shaped, with multiple chloroplasts

• the rest are heterotrophic or phagotrophic

• genus euglena are facultative heterotrophs

• prefer environments with abundant decaying matter (shallow lakes, wetlands, farm ponds)

Rotifera characteristics

• unsegmented

• pseudocoelomate

• ciliated apical region known as the corona

• a muscular pharynx known as the mastax

• cilia are used for filter feeding and locomotion

• critical role in microbial nutrient loop

daphnia  and other branchiopod characteristics

• leaf-like thoracic legs (phyllopods)

• eat algae and detritus and often consume the bacteria on benthic or suspended organic matter

what were we trying to determine in the chlorophyll experiment

Do the algae respond to changes in nutrient levels (N and P) of their growth medium?

why use chlorophyll a to determine phytoplankton growth

• all algae contain chlorophyll a because it is required to capture energy from the sun to be used in photosynthesis

• makes photosynthesis possible by passing its energized electrons onto molecules that manufacture sugars

• therefore chlorophyll a can be used a bioindicator for algae

chlorophyll accounts for what percent of algae dry weight

0.9 – 3.9%

what happens when chlorophyll a is exposed to light

can degrade to phaeophytin

why does conversion of chlorophyll a to phaeophytin cause inaccurate results

• phaeophytin absorbs light in the same wavelength as chlorophyll a

• can result in an artificially high concentration of chlorophyll a reported
  

what causes high phaeophytin

• many dead phytoplankton

• or they are nearing senescence

• indicates poor physiological condition (health) of phytoplankton

healthy ratio of chlorophyll a to phaeophytin

• A ratio of 1.7 chlorophyll a to phaeophytin

• indicates little degradation occured

unhealthy ratio of chlorophyll a to phaeophytin

ratio of 1 indicates an unhealthy culture
and/or chlorophyll a degradation with sample processing

what are the first steps in the chlorophyll a experiment (filtration steps)

1. add10 mL of the algae culture to filter apparatus, using the hand vacuum pump to separate the algae from the medium

2. transfer the filter paper with the algae to a homogenizer tube and add 5 mL of absolute methanol

3. grind the filter paper and methanol using the drill assembly at medium speed for 1 minute

4. add a new filter paper to the apparatus and put a test tube into the filtration flask to catch the filtrate

5. pour the homogenized mixture into the filtration apparatus

6. rinse the homogenizing tube with 3 mL absolute methanol and add to the filtration apparatus

7. collect the filtrate to use for spectrophotometry

steps of the chlorophyll a experiment involving recording data (spectrophotometry)

1. add 3 mL of sample to a cuvette

2. take readings at 650, 665, and 750 nm (use methanal blank at each wavelength)

3. add 100 microliters of 0.1 N HCl to cuvette and blank

4. mix and set aside for 4 minutes

5. add 100 microliters of 0.1 N NaOH to cuvette and blank, then mix

6. take readings at 665 nm and 750 nm (use blank at each wavelength)

why is HCl added in the chlorophyll a experiment

the acidification converts all chlorophyll a to to phaeophytin

why add NaOH in the chlorophyll a experiment

The NaOH step neutralizes the acidity prior to reading because acidified
samples in methanol affect chlorophyll’s maximum absorption peak

why were readings in the chlorophyll a experiment taken at 750 nm

• corrects for turbidity and other pigments that might interfere with the assessment

• must subtract the readings at 750 from the readings at 650 and 665 (650-750 and 665-750)

how to determine chlorophyll a to phaeophytin ratio

665 reading before acidification / 665 reading after acidification

(correction for turbidity with 750 reading must be done first)

what is bioassay

an assessment that determines the effect of pollutants on standard test organisms in a lab setting

why were daphnia used in our experiment

are easy to maintain in the lab and do not require animal care permitting

define LC50

50% lethal concentration – this is the
concentration which kills 50% of the organisms over a specified period of time

define no-observable-effect level

the concentration where there was no observable effect on the organisms

normal swimming behavior vs abnormal swimming behavior in daphnia

• normal: hop and sinking motion

• anormal: slow movement, jittery/fast movement, immobility

what was the purpose of the daphnia bioassay

determine acute and chronic effects of salt (ice melting salt) on daphnia behavior and mortality

what is a standard curve

a graph that is prepared by plotting results for samples of
known concentration (or standards) vs. absorbance

what r² value range is considered accurate

over 0.95

why use a standard curve

to determine the unknown concentration of samples using the standards

what concentrations are inaccurate in a standard curve

very high or very low concentrations

why are very low concentrations inaccurate

the error of measurement may be too great and result in inaccurate measurements