GPP, NPP and respiration
Relationship between net and gross primary production in the Sagami Bay, Japan. S. Hashimoto1 of NPP:GPP in order to understand the ecosystem and car-. Start studying Edexcel A2 Biology [GPP and NPP]. Learn vocabulary, terms Explain the relationship between GPP, NPP and respiration. Respiration releases. In ecology, primary production is the synthesis of organic compounds from atmospheric or Gross primary production (GPP) is the amount of chemical energy as reductions in ocean NPP between 3% and 10% of current values depending.
Ecological efficiency is based on factors that are related to resource acquisition and assimilation of organisms in the ecosystem. Primary production also covers the processing and production of organic components from the atmospheric or aquatic carbon dioxide.
The processes of photosynthesis and chemosynthesis are also notable in primary production. The main source of energy in the production of chemical energy in organic compounds comes from the sunlight, but a small portion of it comes from the inorganic molecules of lithotrophic organisms. This energy is converted, mainly by plants and algae, to synthesize complex organic molecules into simpler, organic compounds like water. Simple molecules can also be synthesized to make more complicated as well, like proteins, and can be respired to perform work.
To measure these factors, gross primary production and net primary production are used. Gross primary production, or GPP, is the estimation at which the producers in an ecosystem absorb a specific amount of chemical energy as biomass in a given span of time.
Biomass is defined as the mass of organisms per unit area and is usually expressed in units of energy or dry organic matter.
It is a renewable energy source that can be used for thermal, chemical, and biochemical conversion for useful energy. The measurement is not limited to the partial organisms but also to other ecological units such as population and entire communities.
While plants cover much of the Earth's surface, they are strongly curtailed wherever temperatures are too extreme or where necessary plant resources principally water and PAR are limiting, such as deserts or polar regions. Water is "consumed" in plants by the processes of photosynthesis see above and transpiration.
Transpiration allows plants to transport water and mineral nutrients from the soil to growth regions, and also cools the plant. Diffusion of water vapour out of a leaf, the force that drives transpiration, is regulated by structures known as stomata. These structure also regulate the diffusion of carbon dioxide from the atmosphere into the leaf, such that decreasing water loss by partially closing stomata also decreases carbon dioxide gain.
Certain plants use alternative forms of photosynthesis, called Crassulacean acid metabolism CAM and C4. These employ physiological and anatomical adaptations to increase water-use efficiency and allow increased primary production to take place under conditions that would normally limit carbon fixation by C3 plants the majority of plant species.
Oceanic production[ edit ] Marine diatoms ; an example of planktonic microalgae In a reversal of the pattern on land, in the oceans, almost all photosynthesis is performed by algae, with a small fraction contributed by vascular plants and other groups.
Algae encompass a diverse range of organisms, ranging from single floating cells to attached seaweeds. They include photoautotrophs from a variety of groups. Eubacteria are important photosynthetizers in both oceanic and terrestrial ecosystems, and while some archaea are phototrophicnone are known to utilise oxygen-evolving photosynthesis.
Vascular plants are also represented in the ocean by groups such as the seagrasses. Unlike terrestrial ecosystems, the majority of primary production in the ocean is performed by free-living microscopic organisms called phytoplankton. Larger autotrophs, such as the seagrasses and macroalgae seaweeds are generally confined to the littoral zone and adjacent shallow waters, where they can attach to the underlying substrate but still be within the photic zone.
There are exceptions, such as Sargassumbut the vast majority of free-floating production takes place within microscopic organisms.
Difference Between NPP and GPP
Differences in relative photosynthesis between plankton species under different irradiance The factors limiting primary production in the ocean are also very different from those on land. The availability of water, obviously, is not an issue though its salinity can be. Similarly, temperature, while affecting metabolic rates see Q10ranges less widely in the ocean than on land because the heat capacity of seawater buffers temperature changes, and the formation of sea ice insulates it at lower temperatures.
However, the availability of light, the source of energy for photosynthesis, and mineral nutrientsthe building blocks for new growth, play crucial roles in regulating primary production in the ocean. This is a relatively thin layer 10— m near the ocean's surface where there is sufficient light for photosynthesis to occur.
Light is attenuated down the water column by its absorption or scattering by the water itself, and by dissolved or particulate material within it including phytoplankton. Net photosynthesis in the water column is determined by the interaction between the photic zone and the mixed layer. Turbulent mixing by wind energy at the ocean's surface homogenises the water column vertically until the turbulence dissipates creating the aforementioned mixed layer.
The deeper the mixed layer, the lower the average amount of light intercepted by phytoplankton within it. The mixed layer can vary from being shallower than the photic zone, to being much deeper than the photic zone. When it is much deeper than the photic zone, this results in phytoplankton spending too much time in the dark for net growth to occur.
The maximum depth of the mixed layer in which net growth can occur is called the critical depth.
As long as there are adequate nutrients available, net primary production occurs whenever the mixed layer is shallower than the critical depth. Both the magnitude of wind mixing and the availability of light at the ocean's surface are affected across a range of space- and time-scales.
The most characteristic of these is the seasonal cycle caused by the consequences of the Earth's axial tiltalthough wind magnitudes additionally have strong spatial components. Consequently, primary production in temperate regions such as the North Atlantic is highly seasonal, varying with both incident light at the water's surface reduced in winter and the degree of mixing increased in winter. In tropical regions, such as the gyres in the middle of the major basinslight may only vary slightly across the year, and mixing may only occur episodically, such as during large storms or hurricanes.
Primary production - Wikipedia
Annual mean sea surface nitrate for the World Ocean. Data from the World Ocean Atlas Mixing also plays an important role in the limitation of primary production by nutrients.Energy Flow in Ecosystems
Inorganic nutrients, such as nitratephosphate and silicic acid are necessary for phytoplankton to synthesise their cells and cellular machinery. Because of gravitational sinking of particulate material such as planktondead or fecal materialnutrients are constantly lost from the photic zone, and are only replenished by mixing or upwelling of deeper water. This is exacerbated where summertime solar heating and reduced winds increases vertical stratification and leads to a strong thermoclinesince this makes it more difficult for wind mixing to entrain deeper water.
Consequently, between mixing events, primary production and the resulting processes that leads to sinking particulate material constantly acts to consume nutrients in the mixed layer, and in many regions this leads to nutrient exhaustion and decreased mixed layer production in the summer even in the presence of abundant light. However, as long as the photic zone is deep enough, primary production may continue below the mixed layer where light-limited growth rates mean that nutrients are often more abundant.
Iron[ edit ] Another factor relatively recently discovered to play a significant role in oceanic primary production is the micronutrient iron. A major source of iron to the oceans is dust from the Earth's desertspicked up and delivered by the wind as aeolian dust.
In regions of the ocean that are distant from deserts or that are not reached by dust-carrying winds for example, the Southern and North Pacific oceansthe lack of iron can severely limit the amount of primary production that can occur.
These areas are sometimes known as HNLC High-Nutrient, Low-Chlorophyll regions, because the scarcity of iron both limits phytoplankton growth and leaves a surplus of other nutrients. Some scientists have suggested introducing iron to these areas as a means of increasing primary productivity and sequestering carbon dioxide from the atmosphere.
Difference Between NPP and GPP | Difference Between | NPP vs GPP
Gross production is almost always harder to measure than net, because of respiration, which is a continuous and ongoing process that consumes some of the products of primary production i.
Also, terrestrial ecosystems are generally more difficult because a substantial proportion of total productivity is shunted to below-ground organs and tissues, where it is logistically difficult to measure.
Shallow water aquatic systems can also face this problem. Scale also greatly affects measurement techniques. The rate of carbon assimilation in plant tissues, organs, whole plants, or plankton samples can be quantified by biochemically based techniquesbut these techniques are decidedly inappropriate for large scale terrestrial field situations.
There, net primary production is almost always the desired variable, and estimation techniques involve various methods of estimating dry-weight biomass changes over time.