NUTRIEN: C - CARBON MSP513: PRODUKTIVITAS PERAIRAN - SDP SIGID HARIYADI Produktivitas & Lingkungan Perairan (Proling) Dept. MSP – FPIK - IPB

FAKTOR-FAKTOR yang mempengaruhi Produksi Primer I. Faktor Abiotik II. Faktor Biotik 1. Cahaya 2. Temperatur 3. Nutrien 4. Oksigen 5. Kualitas fisika-kimia air lainnya: kekeruhan/TSS, bahan toksik 1. Kompetisi 2. Pemangsaan / grazing

Salah satu dari 11 element utama dalam produksi bahan organik: ESSENTIAL NUTRIENT Tucker, MR. 1999. Essential Plant Nutrients: their presence in North Carolina soils and role in plant nutrition Salah satu dari 11 element utama dalam produksi bahan organik: C, H, O, N, P, K, S, Na, Ca, Mg dan Cl

C C (carbon) biomass-limiting nutrients: membatasi produksi biomass rate-limiting nutrients: membatasi laju produktivitas primer C (carbon)

Nutrient supply

N2 – Nitrogen O2 – Oksigen Ar – Argon CO2 – Karbon dioksida *kelarutan pada air murni 10°C, 1 atm

Carbon Cycle

CO2 berupa gas, di atmosfer : 0,027- 0,044 % (0,033%), tetapi kelarutannya tinggi : 1194 ml/L Kelarutan CO2 dalam air murni pada berbagai temperatur

FOTOSINTESIS Bila PQ = 1,0 maka 1 mol CO2 akan menghasilkan 1 mol O2 Tetapi PQ ≠ 1  PQ = 1.2 maka 1 mol CO2 akan menghasilkan 1,2 mol O2 44 g CO2  (1,2 x 32) g O2 1 g CO2  0.873 g O2

FOTOSINTESIS

FOTOSINTESIS http://commons.wikimedia.org/wiki/File:Simple_photosynthesis_overview.PNG

C6H12O6 + 6 O2  6 CO2 + 6 H2O + energi (674 kcal) RESPIRASI C6H12O6 + 6 O2  6 CO2 + 6 H2O + energi (674 kcal) Tiap 1 mol glukosa yang dibakar (dioksidasi) menghasilkan energi 674 kcal., maka :

Bila karbohidrat sederhana terdekomposisi : RQ = O2/CO2 = 1.0 Dekomposisi & respirasi yang terjadi tidak hanya pada karbohidrat sederhana, tetapi juga lemak, protein dan berbagai bahan lainnya pada proporsi yang berbeda-beda CO2 yang diproduksi lebih kecil dari O2 terpakai Sehingga CO2/O2 < 1.0 atau RQ = 0.85 Berarti ΣO2 dikonsumsi X 0.85 = CO2 dihasilkan oleh proses dekomposisi aerobik & respirasi dalam jangka waktu tertentu (Respiratory Quotient)

Carbon concentrating mechanisms In water Cyanobacteria possess carboxysomes, which increase the concentration of CO2 around RuBisCO to increase the rate of photosynthesis. An enzyme, carbonic anhydrase, located within the carboxysome releases CO2 from the dissolved hydrocarbonate ions (HCO3–). Before the CO2 diffuses out it is quickly sponged up by RuBisCO, which is concentrated within the carboxysomes. HCO3– ions are made from CO2 outside the cell by another carbonic anhydrase and are actively pumped into the cell by a membrane protein. They cannot cross the membrane as they are charged, and within the cytosol they turn back into CO2 very slowly without the help of carbonic anhydrase. This causes the HCO3– ions to accumulate within the cell from where they diffuse into the carboxysomes. Pyrenoids in algae and hornworts also act to concentrate CO2 around rubisco

RuBisCO The enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase, most commonly known by the shorter name RuBisCO or just rubisco is used in the Calvin cycle to catalyze the first major step of carbon fixation. RuBisCO is thought to be the most abundant protein in the world since it is present in every plant that undergoes photosynthesis and molecular synthesis through the Calvin cycle. RuBisCO catalyzes either the carboxylation or oxygenation of ribulose-1,5-bisphosphate (known as RuBP) with carbon dioxide or oxygen. What makes it unique and different to every other enzyme is the fact that it can survive on its own without the need of the plant so even if it is dead it remains and helps decomposition. This is due to it not being affected by temperature or pH.

The Calvin Cycle phosphoglyceric acid glyceraladehyde-3-phosphate http://hyperphysics.phy-astr.gsu.edu/hbase/biology/imgbio/calvine.gif The Calvin Cycle phosphoglyceric acid glyceraladehyde-3-phosphate

Carbon dioxide is captured in a cycle of reactions known as the Calvin cycle or the Calvin-Benson cycle. It is also known as just the C3 cycle. Carbon dioxide diffuses into the stroma of chloroplasts and combines with a five-carbon sugar, ribulose1,5-biphosphate (RuBP). The enzyme that catalyzes this reaction is referred to as RuBisCo, a large organic molecule. This catalyzed reaction produces a 6-carbon intermediate which decays almost immediately to form two molecules of the 3-carbon compound, 3-phosphoglyceric acid (3PGA). The fact that this 3-carbon molecule is the first stable product of photosynthesis leads to the practice of calling this cycle the C3 cycle.

Carbon dioxide levels and photorespiration As carbon dioxide concentrations rise, the rate at which sugars are made by the light-independent reactions increases until limited by other factors. RuBisCO, the enzyme that captures carbon dioxide in the light-independent reactions, has a binding affinity for both carbon dioxide and oxygen. When the concentration of carbon dioxide is high, RuBisCO will fix carbon dioxide. However, if the carbon dioxide concentration is low, RuBisCO will bind oxygen instead of carbon dioxide. This process, called photorespiration, uses energy, but does not produce sugars.

photorespiration photorespiration is an entirely negative term because it represents a severe loss to the process of using light energy in photosynthetic organisms to fix carbon for subsequent carbohydrate synthesis. By leading to the loss of up to half of the carbon that has been fixed at the expense of light energy, photorespiration undoes the work of photosynthesis. But during hot and dry conditions, the stomata close to prevent excessive water loss and the continuing fixation of carbon in the Calvin cycle dramatically reduces the relative concentration of CO2. When it reaches a critical level of about 50 ppm the rubisco stops fixing CO2 and begins to fix O2 instead. Even though the detoured process feeds some PGA back into the cycle, the photorespiration process causes rubisco to operate at only about 25% of its optimal rate.

Carbon dioxide and rate of photosynthesis An increase in the carbon dioxide concentration increases the rate at which carbon is incorporated into carbohydrate in the light-independent reaction, and so the rate of photosynthesis generally increases until limited by another factor. As it is normally present in the atmosphere at very low concentrations (about 0.04%), increasing carbon dioxide concentration causes a rapid rise in the rate of photosynthesis, which eventually plateaus when the maximum rate of fixation is reached. http://www.rsc.org/learn-chemistry/content/filerepository/CMP/00/001/068/Rate%20of%20photosynthesis%20limiting%20factors.pdf

Limiting factors In 1905, when investigating the factors affecting the rate of photosynthesis, Blackmann formulated the Law of limiting factors. This states that the rate of a physiological process will be limited by the factor which is in shortest supply. Any change in the level of a limiting factor will affect the rate of reaction. For example, the amount of light will affect the rate of photosynthesis. If there is no light, there will be no photosynthesis. As light intensity increases, the rate of photosynthesis will increase as long as other factors are in adequate supply. As the rate increases, eventually another factor will come into short supply. The graph below shows the effect of low carbon dioxide concentration. It will eventually be insufficient to support a higher rate of photosynthesis, and increasing light intensity will have no effect, so the rate plateaus. http://www.rsc.org/learn-chemistry/content/filerepository/CMP/00/001/068/Rate%20of%20photosynthesis%20limiting%20factors.pdf

If a higher concentration of carbon dioxide is supplied, light is again a limiting factor and a higher rate can be reached before the rate again plateaus. If carbon dioxide and light levels are high, but temperature is low, increasing temperature will have the greatest effect on reaching a higher rate of photosynthesis. http://www.rsc.org/learn-chemistry/content/filerepository/CMP/00/001/068/Rate%20of%20photosynthesis%20limiting%20factors.pdf

Temp  rate of photosynthesis [CO2]  rate of photosynthesis

Peranan pH dan Alkalinitas terhadap ketersediaan Carbon

CO2 + H2O H2CO3 H+ + HCO3- H+ + CO3= 1% CO2 dalam air berdissosiasi : hidrolisa dissosiasi I dissosiasi II asam karbonat bikarbonat karbonat CO2 + H2O H2CO3 H+ + HCO3- H+ + CO3= Karena mengandung CO2 (berarti juga asam karbonat), maka air melarutkan kapur menjadi kalsium karbonat : CaCO3 + H2CO3 Ca(HCO3)2 Berkaitan dengan reaksi ini, dikenal: CO2 pengimbang -- utk mempertahankan jumlah Ca(HCO3)2 CO2 agresif = sejumlah CO2 utk melarutkan kapur lebih lanjut Bila CO2 pengimbang berkurang, maka: Ca(HCO3)2 CaCO3 + H2O + CO2

{ CO2 + H2O H2CO3 H+ + HCO3- H+ + CO3= HCO3- + H2O H2CO3 + OH- CO3= + asam karbonat bikarbonat karbonat CO2 + H2O H2CO3 H+ + HCO3- H+ + CO3= Selain kesetimbangan di atas, bikarbonat dan karbonat dalam air juga mengalami hidrolisa : HCO3- + H2O H2CO3 + OH- CO3= + H2O HCO3- + OH- H2CO3 H2O + CO2 Dissosiasi asam karbonat dapat juga dituliskan: Pada perairan basa, kesetimbangan2 di atas dapat merupakan sistem buffer (penyangga pH) perairan: { karbonat (garam) --- CaHCO3 sistem buffer = campuran & asam karbonat (asam lemah) -- H2CO3 Pada sistem buffer ini : Penambahan basa kuat bereaksi dg. H2CO3 garam + HCO3- SigidHariyadi Penambahan asam kuat bereaksi dg. HCO3- atau CO3= H2CO3

Ca(HCO3)2 CaCO3 + CO2+ H2O & H2CO3 Bentuk-bentuk CO2 di perairan alam: 100% & H2CO3 50% pH 4 5 6 7 8 9 10 11 12 Bentuk-bentuk CO2 di perairan alam: Ca(HCO3)2 CaCO3 + CO2+ H2O garam asam garam netral CO2 bebas & berupa asam : (H2CO3)  hydrated state SigidHariyadi

Isotop-isotop C pada CO2 : radioaktif non radioaktif 98,9 % 14N + n 14C + H 14C + O2 14CO2 hanya dari 12CO2 _______ 1,2 x 1012 1 neutron Isotop-isotop C pada CO2 : SigidHariyadi

Peranan pH

Peranan Alkalinitas dan pH

CO2 mg/L = 1.589 x 106 [H+] x mg/L alkalinitas total sebagai CaCO3 CO2 mg/L = 1.589 x 106 [H+] x mg/L alkalinitas sebagai HCO3 CO2 mg/L = 1.589 x 106 [H+] x mg/L alkalinitas total sebagai CaCO3 1 0.82

CO2 – Alkalinitas - pH

Referensi:    

Thanks Danke