Aquatic Productivity
*Concepts:*
1. Primary Producers (Autotrophs): Convert inorganic compounds into organic compounds using sunlight (photosynthesis) or chemical reactions (chemosynthesis).
*Photosynthesis:*
6CO2 + 6H2O + sunlight → C6H12O6 (carbohydrate) + 6O2
*Respiration:*
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
*Productivity Types:*
1. *Primary Productivity*: Conversion of inorganic compounds into organic compounds.
2. *Gross Primary Productivity (GPP)*: Total organic material synthesized during photosynthesis/chemosynthesis.
3. *Net Primary Productivity (NPP)*: GPP - Respiration
*Formula:*
NPP = GPP - Respiration
*Key Points:*
1. Photosynthesis exceeds respiration for net biomass gain.
2. Chemosynthesis occurs at deep-sea hydrothermal vents using hydrogen sulfide oxidation.
3. Primary producers support heterotrophic life in aquatic systems..
*Memory Tips:*
1. "Photosynthesis = Energy In" (sunlight)
2. "Respiration = Energy Out" (energy release)
3. "GPP = Total Production"
4. "NPP = Net Gain" (GPP - Respiration)
Here are the notes on Measuring Primary Productivity using the Light and Dark Bottle Technique:
* Light and Dark Bottle Technique (Garder and Gran, 1927)
*Method:*
1. Collect water sample from a specific depth.
2. Fill three bottles:
- Light Bottle (transparent)
- Dark Bottle (opaque)
- Initial Condition Bottle (measure initial oxygen)
3. Incubate Light and Dark Bottles at original depth for 24 hours.
4. Measure oxygen content in all bottles.
*Calculations:*
1. Gross Photosynthesis = (O2 increase in Light Bottle) + (O2 decrease in Dark Bottle)
2. Net Photosynthesis = O2 increase in Light Bottle
3. Primary Productivity (PP) = (ΔO2 Light Bottle – ΔO2 Dark Bottle) × (12/32) × (1/incubation time)
*Units:*
- mg C m-3 h-1
- µg L-1 h-1
*Key Points:*
1. Light Bottle: Photosynthesis and Respiration occur.
2. Dark Bottle: Only Respiration occurs.
3. Initial Condition Bottle: Measures initial oxygen.
*Formula Breakdown:*
- ΔO2 Light Bottle: Oxygen change in Light Bottle
- ΔO2 Dark Bottle: Oxygen change in Dark Bottle
- 12/32: Conversion factor (carbon to oxygen ratio)
- Incubation time: Time bottles were submerged (24 hours)
*Memory Tips:*
1. "Light Bottle = Photosynthesis + Respiration"
2. "Dark Bottle = Respiration Only"
3. "PP = ΔO2 Light - ΔO2 Dark × conversion factor"
simplified flowchart:
*Primary Productivity Measurement Methods*
1. *14C Method*
→ Collect Water Sample
→ Add 14C Labelled Bicarbonate
→ Expose to Light (2-24 hrs)
→ Filter Samples
→ Measure Radioactivity
→ Calculate Primary Productivity
2. *Chlorophyll Concentration (Proxy Method)*
→ Collect Water Sample
→ Extract Chlorophyll
→ Measure Chlorophyll-a Concentration
→ Estimate Biomass
3. *Satellite Remote Sensing*
→ Collect Satellite Data
→ Measure Ocean/Lake Color
→ Relate Color to Chlorophyll Concentrations
→ Estimate Primary Productivity using Models.
Standing Crop of Phytoplankton:
**
*Definition:* Total biomass of phytoplankton in a given volume of water at a specific point in time.
*Represents:* Current population of phytoplankton in an ecosystem.
*Units:*
1. mg C/m² (milligrams of carbon per square meter)
2. mg Chl/m³ (milligrams of chlorophyll per cubic meter)
Here are the notes in a flowchart format:
*Phytoplankton Biomass Measurement Methods*
1. *Direct Biomass Measurement*
→ Collect Phytoplankton Sample
→ Filter Sample
→ Dry and Weigh Biomass
→ Measure Carbon Content (optional)
2. *Chlorophyll Measurement*
→ Collect Phytoplankton Sample
→ Filter Sample
→ Extract Chlorophyll using Solvents
→ Measure Chlorophyll-a using Spectrophotometer/Fluorometry
3. *Remote Sensing*
→ Satellites Measure Ocean Color
→ Relate Color to Chlorophyll Levels
→ Estimate Phytoplankton Biomass
*Comparison of Methods*
|
Method |
Advantages |
Disadvantages |
|
Direct Biomass |
Accurate |
Time-consuming, Labor-intensive |
|
Chlorophyll |
Quick, Easy |
|
|
| Remote Sensing |
Large-scale, Fast |
Less accurate, Satellite dependency |
*Key Points*
1. Direct Biomass: Time-consuming, but accurate.
2. Chlorophyll: Quick, but indirect measure.
3. Remote Sensing: Large-scale, but less accurate.
*Memory Tips:*
1. "Standing Crop = Phytoplankton Biomass"
2. "mg C/m² = Measure of Phytoplankton"
Important Terms:*
1. Autotrophs
2. Heterotrophs
3. Photosynthesis
4. Respiration
5. Chemosynthesis
6. Primary Productivity
7. Gross Primary Productivity (GPP)
8. Net Primary Productivity (NPP)
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