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Ocean Biological Deserts
Published in Ajai, Rimjhim Bhatnagar, Desertification and Land Degradation, 2022
The next zone is mesopelagic or the mid-water zone or the ‘twilight zone', which ranges between 200 and 1,000 m in depth. As the name suggests, the amount of sunlight reaching the oceanic water in this region reduces drastically. Consequently, the photosynthesis declines, leading to reduced primary production and so the oxygen also gets severely depleted. Still, life forms with more efficient gills or minimal movements such as squids, swordfish, etc. are in plenty here. In addition to this, bioluminescent organisms also live in this zone. The next zone, the bathypelagic zone, is known as the ‘midnight' or the ‘aphotic' zone because of the absence of light, as light cannot penetrate this far. No primary production is possible in this region, at a depth of 1,000–4,000 m. Further beneath this zone, between 4,000 and 6,000 m, is another zone called abyssopelagic. This zone is pitch-black and is normally expected to be devoid of life. However, many such organisms which feed on detritus (dead marine organisms, called marine snow) exist here. The final zone, called the benthic zone, is the lowest level of the ocean. The benthic zone is home to ‘benthos' or bottom-dwellers. They are mostly scavengers or detritivores, organisms that feed on dead organic material.
Succession Theory, Eutrophication, and Water Quality Management
Published in J. Rose, Water and the Environment, 2017
Diane B. Rosenberg, Stephen M. Freedman
Another assumption involves the accumulation and cycling of nutrients. As biological systems develop and mature their capacity to store and cycle nutrients increases, and the role of detritivores in nutrient regeneration increases.12 In terrestrial systems the turnover rate of nutrients tend to accumulate within long lived plant structures. In contrast, it has been thought that as a lake fills in and becomes more shallow, the exchange of nutrients between the surface and deep water accelerates.2
The Emergence of Temporal Order in the Economy
Published in Pier Luigi Gentili, Untangling Complex Systems, 2018
The scheme sketched in Figure 6.1 represents how the linear economy works: it transforms natural resources into waste, but also into the physical and immaterial psychic well-being of humans. The linear economy is driven by the ambition of relentless exponential growth: the GDP of a nation must always increase. Commonly it is said that a linear economy is affected by the “bigger-better-faster-safer” syndrome, which means progress, emotion and fashion to satisfy the endless human thirst for well-being. Companies make profits if they contrive, produce, and sell appealing and cheap goods or services. Unfortunately, the growth-mania of the linear economy determines an unavoidable fast depletion of natural resources. In fact, our planet, Earth, is like a spaceship (Georgescu-Roegen 1976). The “spaceship earth” is embedded in the gravitational fields of our closest star and moon; its fuels are the flow of electromagnetic energy coming from the sun and the thermal energy produced by the decays of unstable nuclei under the terrestrial crust. Within the “spaceship earth” there are stocks of mineral resources, fossil fuels, and all other chemicals that are finite. In a thermodynamic sense, the earth may be conceived, approximately, as a closed system.6 We might delay the exhaustion of natural resources by choosing a strategy of de-growth, which corresponds to negative growth. This radical program proposed by Georgescu-Roegen (1976) wanted to downsize the world economy to the point where it makes use of a very minimum of exhaustible resources. Such proposal has remained unexplored in societies grounding their economy in the accumulation of capital and mass consumption. A valid alternative is the strategy of sustainable growth. Economic growth is sustainable when growth can be maintained without exhausting natural resources and creating environmental problems, especially for future generation. In the last decades, societies have become aware that sustainable growth is feasible if economy mutates from linear to circular. A circular economy works as if it were an ecosystem. Any ecosystem grounds on solar energy (see Figure 6.2). Plants, algae, and phytoplankton feed on solar radiation. They photosynthesize carbohydrates from CO2 and water. They use carbohydrates as chemical fuel for themselves and for the primary consumers that are the herbivores. The herbivores are the food of carnivores. Both plants and herbivores and carnivores produce dead organic matter through their metabolism. Their waste products feed the detritivores that are fungi and bacteria. The detritivores decompose waste products more effectively and release products that feed the producers. Nothing is wasted.
Vermiremediation – Remediation of Soil Contaminated with Oil Using Earthworm (Eisenia fetida)
Published in Soil and Sediment Contamination: An International Journal, 2021
Like any other bioremediation technology vermiremediation also has some limitations which are but not limited to; In highly toxic soils earthworms may fail to survive, so vermiremediation is only limited to relatively less contaminated soils (Rodriguez-Campos et al. 2014; Shi, Tang, and Wang 2019b).Vermiremediation is limited to certain depths of the soil depending upon the type of specie used for bioremediation. Earthworms are classified as epigeic (0.1–0.3 m depth), anecic (3 m depth), and endogenic (0.2 m depth) on the basis of their habitats. E. fetida is epigeic as it lives on the top layers of soil and has specific feed preferences. It usually feeds on plant litter and organic material (debris) present in top layers of soil and also known as detritivores. Whereas, anecics are considered as phyto – geophagous and endogenic are considered as geophagous (Bhattacharya and Kim 2016). Which means vermiremediation is also restricted by food preferences of earthworms (Bonkowski, Griffiths, and Ritz 2011; Curry and Schmidt 2007).If proper disposal does not occur or mismanagement happens contaminants accumulated in earthworms might be transformed into the food chain (Shi, Xu, and Hu 2014).Furthermore, earthworms are sensitive to any change in climate, season and environmental conditions. Hence, affecting the overall efficiency of process of the vermiremediation.In order to survive and perform their action efficiently earthworms need Earthworms need an adequate amount of food (Klok 2007; Rodriguez-Campos et al. 2014).Additionally, enormous number of earthworms i.e. ~ 10 worms/50 gm of soil that are required for vermiremediation might be another limitation (Contreras-Ramos, Álvarez-Bernal, and Dendooven 2006) as they require adequate moisture to perform their normal functions.The multiplication rate of earthworms is 28 which is every individual produces 256 worms every six months. And multiplication of each of these 256 worms at the same rate, as a result producing a large biomass in this short period.In order for the earthworms to perform their burrowing action, the moisture content must be 8–57% (Richardson, Snyder, and Hendrix 2009).