Azong Valery FunwieEric RaesFiddy Semba Prasetiya

Is the primary production in the Spuikom lagoon influenced by water depth ?

Presented by:

OverviewIntroductionObjectivesMaterial and MethodsResultsDiscussionConclusion

Introduction

• The flow of energy through a community starts with the fixation of sunlight by plants photosynthesis

light• 6CO2 + 6H2O => C6H12O6 + 6O2

• Autotrophes are those organisms in an ecosystem system who convert inorganic raw materials into organic substances.

– Phytoplankton are such autotrophic organisms and are responsible for approximately 40 per cent of the planet's total annual photosynthetic (`primary') production. (Baer 2002)

– They are found in the water’s top layer (euphotic zone) where they receive enough solar radiation for their photosynthetic requirements as well as nutrients.

– Light inhibition will effectively lead to an optimal level of light intensity for the phytoplankton. (Christopher A, et al., 2000)

Energy accumulated by plants = primary production

Introduction

Gross Primary Production, GPP, is the total amount of CO2 that is fixed by the plant in photosynthesis

Respiration, R, is the energy required for biological functions such as maintenance and reproduction.

Net Primary Production, NPP, is the energy remaining after respiration and stored as organic matter, or plant growth.

NPP = GPP - R

Objectives

Is the primary production in the Spuikom lagoon influenced by water depth ?

• Questions:

– How do we measure oxygen ?

– Will their be a difference in time ?

– Is there a difference in NPP between surface and bottom water ?

Material and Methods

Both ‘light’ and ‘dark’ bottles are filled with surface and bottom water

Before incubating the bottles initial O2 concentration, from bottom and surface water, was determined and expressed as mg of O2 per litre of water (mg/L).

Bottles are closed with stoppers and are suspended for 4 hours at the same depth from where water originally was taken.

Final O2 concentrations were measured in light and dark bottles after 4 hours of incubation.

Oxygen quantity was measured by chemical titration, Winkler titration method.

1. Production of a manganous hydroxide in the water sample to which manganous sulfate is introduced when KOH plus KI are added:

MnS04 + 2KOH=>Mn(OH)2 + K2S04

2. Oxidation of manganous hydroxide to manganic hydroxide by the dissolved oxygen in the sample:

2Mn(OH)2 + 02 + 2H20=>2Mn(OH)4

3. Conversion of manganic hydroxide to manganic sulfate when concentrated sulfuric acid is added:

2Mn(OH)4 + 4H2S04=> 2Mn(SO4)2 + 8H20

Material and Methods : Steps in Winkler Method

4. Replacement of iodine in an iodide (KI) by sulfate, releasing free iodine:

2Mn(OH)4 + 4KI=>2MnS04 + 2 K2S04 + 2I2

5. Titration of the iodine solution with sodium thiosulfate until all free iodine combines into sodium iodide. The endpoint, marked by the disappearance of the yellow color:

4Na2S2O3+ 2I2=>2Na2S406 + 4NaI

Material and Methods : Steps in Winkler Method (2)

Material and Methods

Light bottle: Has photosynthesis, Gross Primary Production (GPP), Respiration (R).

The difference between these two processes is Net Primary Production NPP = (GPP - R)

=> The quantity of oxygen ,measured after titration, in the light bottle indicates the net photosynthesis, or gross primary production. (GPP)

• Dark bottle: – No photosynthesis – Only respiration.

=> The quantity of oxygen ,measured after titration, in the drak bottle indicates the respiration (R)

• Initial bottle: – Time zero, to calculate the Respiration or Net Primary Production

Material and Methods

• Light Bottle DO - Initial DO = NPP• Light Bottle DO - Dark Bottle DO = GPP• Initial Bottle DO - Dark Bottle DO = Respiration

– (DO = Dissolved Oxygen)

Material and Methods

The whole aquatic ecosystem can be represented by this bottle method.

Light bottle representing the daytime

Dark bottle representing the night.

Where the rise and fall of oxygen during the day and night can be plotted on a diurnal curve.

Results

Day 1, 2:30 pm Oxygen quantity

05

10152025303540

Time Zero (Light) (Dark)

After 4hrs

time (h)

mg

O2

/l

Day 1 2:30pmSURFACE mg O2/L

Day 1 2:30pm BOTTOM mg O2/L

Results

Oxygen concentration in surface and bottom at time zero

0

10

20

30

40

7:00 AM 11:00 AM 2:30 PM

time (h)

mg

O/l SURFACE

BOTTOM

Results

Oxygen concentration mgO/l

05

10152025303540

Day 2 7:00am

Day2 7am

Day 2 11:00 am

Day2 11:00am

Day 1 2:30pm

Day 1 2:30pm

SURFACE BOTTOM SURFACE BOTTOM SURFACE BOTTOM

time (h)

mg

O/l

Time Zero After 4hrs (Light) After 4hrs (Dark)

Results

NPP

0

0.2

0.4

0.6

0.8

1

1.2

1.4

7:00 AM 11:00 AM

Time (h)

mg

C/l

NPP Surface

Results

NPP, R and GPP at the surface

-3

-2

-1

0

1

2

3

4

07.00 (day 2) 11.00 (day 2)

Time (h)

mgc

/l

NPP

Respiration

GPP

Conclusions

Slight increase in NPP Slight increase in O2 concentration over time

Measuring PAR, secchi disk Individual titration, less errors Minimise oxygen bubbles when moving water from bottom water to

bottles

Not enough sampling points/ data Data doesn’t reflect hyothesis No difference between surface and bottom

Dank u well

(^_^)!