Algal mat
Algal mats are one of many types of
Cyanobacteria forming algal mats
Cyanobacteria found in sedimentary rocks indicate that bacterial life began on Earth during the Precambrian age. Fossilized cyanobacteria are commonly found in rocks that date back to Mesoproterozoic.[1] Cyanobacteria are photoautotrophs in nature; they convert carbon dioxide and sunlight into food and energy via photosynthesis. Some species are also able to fix atmospheric nitrogen and convert it into the biologically-usable form of nitrate or nitrite.[2] This gives them competitive advantage over other organisms that may be limited by the shortage of biologically available nitrogen. The cyanobacteria colonies contain two types of cells, the regular cells with chlorophyll carrying out the photosynthesis, and heterocysts which fix the nitrogen. These heterocysts have thick walls and lack chlorophyll, both of which limits their exposure to oxygen, the presence of which inhibits nitrogen fixation. For the same reason, fixation may also be limited to nighttime when the light-dependent reactions of photosynthesis are shut down, minimizing oxygen production.[1]
Stromatolites
The importance of algal mats in the past
Algal mats consist largely of filaments made of autotrophic bacteria and fine-grained particles. These bacterial are well known for the formation of stromatolites. Phototrophic bacteria such as cyanobacteria are evolutionary organisms responsible for the increased oxygen levels during the Proterozoic age. The event was known as The
Negative impacts of algal mats
The rapid formation of algal mats can result in
Moreover, some HABs are harmful to the ecosystem simply by their sheer biomass accumulation. Such biomass accumulation can lead to a multitude of negative consequences. For one, their growth and proliferation can reduce the light penetration in the water column, thereby reducing habitat suitability for the growth of submersed grasses. Exceedingly high biomass can also cause fish gills to clog, leading to suffocation. High biomass blooms can also lead to the development of “dead zones”, formed when the algae begin to die and their decomposition depletes the water of oxygen. Dead zones are unable to support (aerobic) aquatic life, and are responsible for losses of millions of dollars’ worth of fish annually.[6]
Potential applications of algal mats
Third generation biofuel feedstocks are represented by both micro- and macro- algae, which present further advantages over the previous generations. (The first generation biofuels are made from edible feedstock like corn, soybean, sugarcane, and rapeseed. Second generation of biofuels from waste and dedicated lignocellulosic feedstock shave advantages over those of first generation.) Marine and aquatic biomass tentatively demonstrates high yield while requiring minimal use of arable land. Major advantages of algae are: no competition with food crops for arable land, high growth rates, and low fractions of lignin which reduces the need for energy-intensive pretreatment and compatibility with biorefinery approach implementation. It has been proven that macroalgae can reach 2–20 times the production potential of conventional terrestrial energy crops However, some disadvantages such as the presence of high water content, seasonal chemical composition and the occurrence of inhibitory phenomena during anaerobic digestion, make algal biofuels not yet economically feasible although they are more environmental friendly than fossil fuels.[7]
References
- ^ a b c BETTINA E. SCHIRRMEISTER, MURIEL GUGGER and PHILIP C. J. DONOGHUE (2015), CYANOBACTERIA AND THE GREAT OXIDATION EVENT: EVIDENCE FROM GENES AND FOSSILS, Palaeontology, Vol. 58, Part 5, 2015, pp. 769–785
- ^ PMID 11243256.
- ^ a b c d C. M. FRANTZ , V. A. PETRYSHYN , AND F. A. CORSETTI, (2015) Grain trapping by filamentous cyanobacterial and algalmats: implications for stromatolite microfabrics through time, Geobiology (2015), 13, 409–423.
- ^ Bettina E. Schirrmeister, Jurriaan M. de Vos, Alexandre Antonelli, and Homayoun C. Bagheri (2012), Evolution of multicellularity coincided with increased diversification of cyanobacteria and the GreatOxidation Event, DOI10.1073/pnas.1209927110
- S2CID 9823483.
- ^ a b Patricia M. Glibert (2013), Harmful Algal Blooms in Asia: an insidious and escalating water pollution phenomenon with effects on ecological and human health, ASIA Network Exchange.
- ^ Montingelli, ME; Tedesco, S; Olabi, A G. Biogas production from algal biomass: A review, Renewable & Sustainable Energy Reviews43 (Mar 1, 2015): 961-972.