research cruises and sampling Flashcards
what is very useful in Measuring physical parameters
electricity
5 main physical parameters we measure
- light
- temperature
- turbidity
- salinity
- transparency
how do we measure water temp that’s directly infront of you + deeper water that can’t be accessed
- thermometer
- thermocouple
4 things that are Effected by temp of water
- Biochemical reactions e.g. respiration, photosynthesis, degradation, …
- Oxygen concentration: warmer water holds less oxygen
- Biological functions e.g. spawning and migration, reproduction success and growth pattern
- Long-term population declines of fisheries and other organism
2 things that increase water temp
- Power stations
- Climate change
what is salinity and its formula
- amount of inorganic ions dissolved in certain amount of water (unitless)
- Salinity = 1.80655 x Chlorinity
- chlorinity = grams of chloride ions precipitated from 1 kg seawater by Ag+
4 ways to measure salinity
- Can dry everything out from water sample and weigh the salt left behind and divide by the volume
- Can stick silver ions into water to react with the chlorine – that will precipitate out – weigh precipitation and multiply by 1.8 to get the salinity
- Refractometer: salt content affects refractivity of water
- Electrical conductivity sensor (e.g., in CTD): salt content affects how well water conducts electricity
why would we want to measure the amount of light in water
indicate how capable plankton are to photosynthesise aka primary production rates
2 ways to measure the amount of light in water
- calibrate the change in resistance to give indication of light intensity at that point e.g., a light meter - consists of two main parts: (i) data logger that stores and displays the light readings (ii) light sensor that’s connected to the data logger via a cable
- use Light meter attached to FRRf, light profiler
way to measure Water transparency
- Secchi disk— a white or B&W disk; lowered vertically until the disk disappears from sight; the corresponding depth is the Secchi depth (Zs)
- very clear water, Zs > 50 m
- coastal waters, 2 m < Zs < 10 m
- some estuaries, Zs < 1 m
how can we use Secchi disk to calculate water transparency
- By one rule of thumb, the Secchi disk disappears at 16% of the surface irradiance - one can calculate the attenuation coefficient based on the Secchi depth
- k = ln (Iz / I0)
—————–
zs - Iz = Light intensity at particular depth
- I0 = Light intensity at surface
- -z = water depth
what is Turbidity and its units
- Amount of suspended matter (living or inert) - particles in the water - penetration of light
- FNU (Formazin Nephelometric Unit), FTU (Formazin Turbidity Unit), NTU (Nephelometer Turbidity Unit)
method for measuring turbidity
- Nephelometer or turbidity probe (light beam into the water - light will be scattered by any suspended particles - detect the amount of light detected back)
- Base on a calibration using a Formazin standard (forms small size particles)
- The more light is detected the more particle are in the water
Non-electrical way for measuring turbidity
- filtration of water sample on pre-ashed filter – drying - take the weight
- Can take further by sticking the dried material in oven at 550°C for 6hrs - Determine content of organic matter
- ## Unit: mg/l
what does CTD rosette do
- Vertically profiles water column
- Takes discrete water samples at known depths
- Gives real time ancillary data
what do Sediment traps and Submersible pumps do
- Collect particulates as they fall through the water column
- Allows quantification of exports
- SAPS used to quantify low concentration elements
what do Buoys, moorings and AUVs do
- Collect data without human involvement
- Can be deployed for long periods
- May be stationary (buoys), drifter drogues (Argo buoys) or undergo active movement (AUVs)
- e.g. buoys will measure in real time the size and direction of waves based on how it moves the buoy
- e.g. argo buoys get left in water to log temp and salinity throughout water collum
- e.g. AUVs drive around and collect surface conditions
what do UAVs, Gliders, UORs do
- Provide 2D and 3D maps of parameters
- Generally large enough to carry a suite of instruments for multiple measurements
- May be towed (UOR), guided (Autosub) or autonomous (gliders)
- Data may be transmitted through wires, via radio, via satellite or logged on board for later recover
what do Drogues, Dyes, Bacterial spore do
Allows the following of the flow of water
5 ways to collect water data
1.CTD rosette
2. Sediment traps and Submersible pumps
3.Buoys, moorings and AUVs
4.UAVs, Gliders, UORs
5.Drogues, Dyes, Bacterial spore
main way to measure chemical parameters of the water
CTD rosette (More difficult to use electricity)
- Used to collect water body samples + map what’s going on in the water collum
- Samples taken to the lab to test
what is the process in the lab after using CTD rosette to collect water samples
- filtering : Filters things out of the water using different size membranes - look at low concentration of everything
- nutrients : use equipped equipment to measure concentration (of usually N, P and Si) through change in colour down to nano-molar concentrations
- Gas chromatography and Mass spectrometry : Allow identification (of molecules + of radioactive and stable isotopes) and quantification of chemicals in water through changes in carrier materials - Commonly used for C:N measurements and dissolved gas quantification
- HPLC : Measures pigment concentrations of plankton by using system similar to ink chromatorgraphy – can get an idea of the taxonomy present - Light absorption of pigments is diagnostic of plankton groups
main thing we focus on whilst Measuring biological parameters
sampling plankton
4 ways we collect plankton whilst Measuring biological parameters
- Simple plankton net
- continuous plankton recorder (CPR)
- Longhurst Hardy Plankton Recorder (LHPR)
- MOCNESS and MultiNet
how can we use Simple plankton net to collect plankton
- Horizontal / vertical / oblique tows
- Replication
- Quantify
how can we use continuous plankton recorder (CPR) to collect plankton
- Towed behind “platforms of opportunity”
- Traps plankton on continuous band of silk mesh + stored in preservative
- Abundance estimated by colorimetry and subsampling
- Developed by Sir Alister Hardy in 1925
what is LHPR – Longhurst Hardy Plankton Recorder
Incorporates CTD with net, allowing targeted plankton collection
what is MOCNESS and MultiNet
- More structured collection of samples
- Nets can be opened and closed to allow collection of samples from discrete depths
4 ways we can calculate the abundance of plankton collected
- microscopy
- Coulter counters
- Flow cytometer
- Flowcam
what is abundance
Organisms per unit area or volume E.g. 100 cells L-1
what is microscopy and its disadvantages
Count based system
- Human error, miss smaller cells
- Very labour intensive
- Slow
what is Coulter counters
- Movement of a sample between two reservoirs of water
- Particles in the sample flow through a narrow channel, changing the electrical resistance across the channel
- This change is registered as a ‘count; of a particle
what is Flow cytometer
- Measures different types of picoplankton (>2mm) - can get info on amount and size
- Even in the most nutrient poor waters cell counts >100,000 cells/ml
what is Flowcam
Use data analysis to identify zooplankton at different taxa
4 ways to calculate biomass of collected plankton
- Fluorometer
- Remote Sensing
- Cell counts
- Measure Primary production
what is biomass
Organism C per unit area or volume E.g. 100 mg C L-1 OR Chlorophyll a E.g. mg chl a m-3 or mg chl a L-
what is Fluorometer
- Measures chlorophyll (usually from a ship)
- Give indications of concentration, not numbers
- High resolution
- Can be used to profile or from water supply along transect
what is Remote Sensing and its disadvantages
- Use sensors mounted on satellites: translate ocean colour of water leaving irradiance
- Light entering water = downwelling irradiance
- Light redirected back to surface = upwelling irradiance
- Phytoplankton absorb blue & red wavelengths, Reflect in green
- problems:
- Only detect surface chl a
- Reflectivity of sediments and non-phyto particles can be high: estuaries
- Not so great at night (visible spectrum)
problems associated with using Chl a to calculate biomass of plankton
- biomass varies depending on:
Species
Light
Nutritional status - Chl a and biomass do not always correlate
what is cell counts and its disadvantages
- Cell dimensions, geometric shape: biovolume
- Literature carbon:volume conversion figure
- Time consuming, many errors
- Still used for microzooplankton
what’s the Measure of Primary production and 2 ways we can do it to calculate plankton biomass
- C fixation = more accurate and descriptive term
- Radiant energy -> chemical energy
1. 14C method
2. Active Fluorescence
how can we use 14C method to calculate plankton biomass
- Look at how quickly phyto take up carbon by measuring radioactive bicarbonate H14CO3-
- Bottle 1 -> light -> photo & resp
- Bottle 2 -> dark resp
- Amount of 14C in phyto measured: scint. counter E.g. units: mg C m-3 h-1
how can we use Active Fluorescence method to calculate plankton biomass
- In situ measurement of activity in photosystem 2
- Measures rate of and quantity of light absorption by the cell’s photosynthetic apparatus
- Measurement of the process rather than the effect
- Combination of these parameters along with measured photo synthetically available radiation allow a calculation of gross photosynthesis
3 ways we can correlate ocean parameter data with
- Sea surface temps
- Nutrient supplies etc.
- Produce predictive models for future…
