03 Primary Productivity.ppt
- 1. • Productivity – A rate of how much carbon is produced/ fixed per time • g Carbon / m3 / day – GROSS Productivity = Carbon fixed through Photosynthesis per time – NET Productivity = Gross Prod – Respiration • Plant Biomass – How much phytoplankton is there (mg Chl/m3) or (μg Chl/liter) Primary Productivity
- 2. •Gross primary productivity (GPP): The total solar energy used to produce biomass by the process of photosynthesis is referred to as gross primary productivity (GPP). It is the rate of production of organic matter. Some amount of GPP is utilized by the plant itself, and a very little amount is transferred to the consumers. Most of the GPP is lost due to plants’ internal metabolism or cellular respiration or growth and repair mechanism. The lost GPP is referred to as respiratory loss (R). •Net primary productivity (NPP): Net primary productivity is the amount of biomass available for the consumers or heterotrophs after respiratory loss. This biomass is stored in the plants. Net primary production forms the base of ecological food chains and is heavily manipulated by humans in the production of food, fiber, wood, and increasingly biofuels.
- 3. Gross and Net Production • The production of biomass and it’s use as a source of energy by autotrophs includes three steps: 1. Gross Production: An organism produces organic matter within it’s body 2. It uses some of this new organic matter as a fuel in respiration 3. It stores some of the newly produced organic matter for future use. 4. It used (10%) by Consumers in food chain • The amount left after use during respiration is Net Production Net Production (NPP) = Gross Production (GPP)- Respiration (Ra)
- 4. © 2011 Pearson Education, Inc. Chapter Overview • Productivity is affected by sunlight and nutrients. • Productivity is globally,site wise and seasonally variable. • Feeding relationships are represented by food chains and food webs changes the productivity. • Oceans are being overfished.
- 5. Figure Focusing in on the location of photosynthesis in a plant
- 7. © 2011 Pearson Education, Inc. Photosynthesis
- 8. Measures of Primary Production in Aquatic Ecosystems 1. Satellite: Satellite sensors are also used in aquatic ecosystems to quantify the spectral pattern of reflected light off of photosynthetic organisms, which provides an index of NPP. For example, measurement of the spectral signature of chlorophyll a in water bodies is used to estimate the productivity of aquatic primary producers (autotrophs). 2. Light/dark bottle (oxygen) method: This method measures the net production of O2 in the light to determine NPP and the consumption of O2 in the dark to determine respiration (R) in aquatic ecosystems.
- 9. Light and Dark bottle method • This method is employed to measure primary productivity in an aquatic ecosystem such as a pond. It is based upon the assumption that the amount of oxygen produced is proportional to gross production because one molecule of oxygen is produced for each atom of carbon fixed. Samples of water from different depths are placed in paired bottles. One of the paired bottles is covered with black tape or aluminium foil to exclude light and other is kept clear to admit light and allow photosynthesis. The oxygen concentration of the bottles is determined by Winkles method. The bottles are suspended to the same depth from where samples were collected with the help of string. After 24 hours the bottles are removed their oxygen concentration is determined and compared with the concentration at the beginning. The decline of oxygen in the dark bottle indicates the amount of respiration by producers and consumers where the oxygen change in the light bottle reflects the net result of oxygen consumed by respiration and oxygen produced. Adding respiration and production together or subtracting final oxygen concentration in the dark bottle from that in the light bottles give an estimate of gross productivity for 24 hours. This method has its problems. Some of the respiration attributed to phytoplankton may be bacterial. The phytoplankton population may increase in the bottle during the experimental time but not in dark bottle. Also the procedure is based on the assumption that respiration in the dark is the same as in the light.
- 10. Measurement of Productivity: C incorporation experiments
- 11. Radioactive labeled method • It is one of the most useful and sensitive method useful to estimate primary productivity in an aquatic ecosystem especially in lakes and oceans. It is based upon measurement of 14CO2 uptake. The method involves addition of radioactive carbon as carbonate to a sample of water in clear and unstable carbon are assimilated into carbohydrates and become part of the protoplasm of phytoplankton. The plankton material is removed from the water washed dried and place in a counting chamber to determine the level of radioactivity. The radioactive amount is used to calculate the amount of carbon dioxide fix in photosynthesis using the photosynthetic equation. The estimate is based on the assumption that of radioactive carbon is proportional to that of stable carbon.
- 12. determination of chlorophyll contents • This method is based upon estimation of producer from chlorophyll concentration and light intensity through the water column.The method was first to used to estimate primary productivity in large water bodies such as sea but later applied to terrestrial ecosystem as well as. • This method involves the determination of chlorophyll contents of phytoplankton in a given volume of water. Because all plant need chlorophyll to carry on photosynthesis the amount of chlorophyll in a given amount of water is a direct measure of the total biomass or standing crop of phytoplankton it contains. • The chlorophyll is extracted chemically and the amount of chlorophyll is measured. The deeper the colour the greater is the concentration of the chlorophyll and therefore phytoplankton biomass. • The technique has a problem that chlorophyll concentration varies with phytoplankton species and even within the cells of species. Further extraction technique may alter the chlorophyll.
- 13. So Chl concentration is reasonable estimation of primary productivity in surface waters
- 14. July Chlorophyll
- 16. Cyanobacteria such as Trichodesmium , Hammatoidea, Heterohormogonium, Albrightia, Scytonematopsis, Thalopophila, Myxocarcina and Colteronema give thermal springs and geyser pools beautiful color patterns - from red to purple and the complete visible spectrum of colors between
- 17. Measures of Primary Production in Terrestrial Ecosystems 1. Primary production is measured differently in terrestrial versus aquatic ecosystems. 2. CO2 Method: this method measures the net consumption of CO2 in the light to determine NPP and the production of CO2 in the dark to determine respiration (R) 3. Harvest Method: This method is based on measuring the standing crop biomass at two different times. The difference between each time is the NPP. 4. Satellite: Satellite sensors quantify the spectral pattern of reflected light off of photosynthetic organisms, which provides an index of NPP. In terrestrial ecosystems measurement of visible and near-infrared wavelengths reflected off vegetation (Normalized Difference Vegetation Index; NDVI) is used to estimate the productivity of terrestrial autotrophs.
- 18. CO2 Method • Primary productivity is usually determined by measuring the uptake of carbon dioxide or the output of oxygen. Production rates are usually expressed as grams of organic carbon per unit area per unit time. • Scientists use several complementary tools for quantifying terrestrial gross and net primary production at ecosystem to global scales. On-the-ground inventory based methods are commonly used in cropland, grassland, and forested ecosystems to measure NPP. • This approach requires estimates of biomass production through periodic measurements of root, stem, leaf, and fruit growth. • The growth over time of all plant tissues within a terrestrial ecosystem is equal to NPP. • In this approach, aboveground (ears, stalks, leaves) and belowground (roots) corn biomass yield over a single growing season is equal to annual NPP of this crop ecosystem.
- 19. Estimation of terrestrial primary production using meteorological towers that measure the uptake or emissions of CO2 by ecosystems (Figure 2). Meteorological towers measure net ecosystem CO2 exchange (NEE), which is equal to GPP minus ecosystem respiration or the quantity of CO2 respired by both autotrophs (plants) and heterotrophs (primarily microbes). GPP and NPP are calculated indirectly by adding ecosystem and heterotrophic respiration, respectively, to NEE. Meteorological approaches are employed worldwide in forest, agricultural, grassland, and desert ecosystems to track terrestrial primary production.
- 20. The incoming and outgoing CO2 from the leaf chamber is measured by infrared spectroscopy with an infrared gas analyzer. The difference gives us the amount of CO2, from which the rate of photosynthesis can be calculated. Fourier transform infrared spectroscopy (FTIR) is a technique which is used to obtain infrared spectrum of absorption, emission, and photoconductivity of solid, liquid, and gas.
- 21. Standing Crop: Plant Biomass
- 22. Harvest method- Agriculture crops , grasslands • widely used to estimate in terrestrial ecosystem. • most useful for estimating the production of cultivated land range and communities of annual plants were production starts from zero at seedling or planting time becomes maximum at harvest and is subject to minimal use by consumers. • The technique involves removing vegetation at periodic intervals and drying the samples to a constant weight. To obtain n accurate estimate the production of plant biomass must be sampled throughout the growing season and the contribution of each species must be determined. Different species of plants reach their peak production at different times during the growing season. • The difference in standing crop biomass between harvests periods expressed as grams per square meter per unit time provides an estimate of net primary productivity. • Caloric value of the material can be determined through use of a calorimeter and biomass can be converted to calories. Net primary productivity is then expressed as kilocalories per square meter per year.
- 23. Grass clippings after 1 week: Productivity
- 24. Ecosystem Productivity (Annual net productivity)
- 25. Controlling Primary Production • Primary production is controlled by different factors in terrestrial versus aquatic ecosystems. • Water: Influences terrestrial (aquatic systems are not water limited) ecosystems are largely influenced by water – greater precipitation/soil moisture increases primary production. • Temperature: terrestrial and aquatic; higher temperatures increase primary production (think about how temperature increases chemical reaction rates). • Light: production in aquatic systems is limited by light because light is quickly attenuated at depth; terrestrial systems are not as limited as aquatic systems by light, but since light and temperature are related, light does play an indirect role in terrestrial systems via temperature. • Nutrients: terrestrial and aquatic; increased nutrient availability results in greater primary production; productivity in terrestrial systems tends to be limited by nitrogen, whereas productivity in aquatic systems tends to be limited by phosphorus.
- 26. Gross Productivity • Varies across the surface of the earth • Generally greatest productivity – In shallow waters near continents – Along coral reefs – abundant light, heat, nutrients – Where upwelling currents bring nitrogen & phosphorous to the surface • Generally lowest productivity – In deserts & arid regions with lack of water but high temperatures – Open ocean lacking nutrients and sun only near the surface
- 27. Factors Affecting Primary Productivity • Nutrient availability – Nitrate, phosphorous, iron, silica – Most from river runoff – Productivity high along continental margins – Redfield ratio – C:N:P (carbon, nitrogen and phosphorus (106:16:1) found in phytoplankton and throughout the deep oceans).
- 28. Figure 13.8
- 30. Factors Affecting Primary Productivity • Solar radiation directly proportional to PP – Uppermost surface seawater and shallow seafloor – Compensation depth – net photosynthesis becomes zero – Euphotic zone—from surface to about 100 meters (330 feet)
- 31. Light Transmission in Ocean Water • Visible light of the electromagnetic spectrum • Blue wavelengths penetrate deepest • Longer wavelengths (red, orange) absorbed first at surface area
- 32. Polar Ocean Productivity • Isothermal waters – little mixing (no mixing ) • Plankton remain at surface • Blue whales migrate to feed on maximum zooplankton productivity.
- 33. © 2011 Pearson Education, Inc. Temperate Ocean Productivity • Highly seasonal pattern • Winter : low Productivity – Many nutrients, little sunlight • Spring :high Productivity – Spring bloom • Summer: low Productivity – Few nutrients, abundant sunlight • Fall: high Productivity – Fall bloom
- 34. Latitudinal effects on seasonal variations of Primary productivity