Nutrient-poor environment

Muscatine, L., and Porter, J. W. (1977). Reef corals Mutalistic symbioses adapted to nutrient-poor environments. Bioscience. 27, 454—460. 

There are several other points about competition that I would like to make before going on to other kinds of Interaction. Competition between populations in certain environments might be pure—e., the only Interaction between the populations—but it might not be simple because the concentrations of two or more nutrients competed for may affect the growth rates of the populations. "Nutrients" as used here means chemicals not produced by the competing populations or by others present, so there is no question here of competition for self-renewing resources. In nutrient-poor environments, the concentrations of several... 

Morton B, Blackmore G (2001) South China Sea. Mar PoUut Bull 42(12) 1236-1263 Muscatine L, Porter JW (1977) Reef corals Mutualistic symbioses adapted to nutrient-poor environments. Bioscience 27(7) 454-460 Ni HG, Lu FH, Luo XL, Tian HY, Zeng EY (2008) Riverine inputs of total organic carbon and suspended particulate matter from the Pearl River delta to the coastal ocean off South China. Mar PoUut Bull 56(6) 1150-1157 Onstad GD, Canfield DE, Quay PD, Hedges JI (2000) Sources of particulate organic matter in rivers from the continental USA Lignin phenol and stable carbon isotope compositions. Geochim Cosmochim Acta 64(20) 3539-3546 Peng Z, Chen T, Nei B, Head MJ, He X, Zhou W (2003) Coral records as an indicator of winter monsoon intensity in the South China Sea. Quat Res 59(3) 285-292... 

Figure 5.4 Relationship between nutrient level and bacterial attachment, a A nutrient-poor environment where the nutrients can be reached on the surface, thus promoting sessile growth. High corrosion rates can be expected, b A nutrient-rich enviromnent where the nutrients can be reached within the bulk solution, thus promoting planktoitic growth. Lower corrosion rates can be expected...

After resolving the issue of matrix design, the next step was to determine a desirable anatomical location. Several considerations were used in determining possible implant sites. The first is the size of the implant and the requirement that it be placed in juxtaposition to well-vascularized tissue. A transplant matrix constructed as a porous sheet-like structure could be at most 200 mm thick, based on estimates of nutrient transport limitations (66). The size of a device required to replace about 5% of the mass of an adult liver would then be about 0.5 m2. Surgical trauma must be avoided when implanting the device, because such trauma produces fibrin clots and hematoma formation around the wounded area, which creates a poor environment for cell survival. Also, the implant may behave better if supplied by the portal circulation rather than the systemic, because the portal circulation contains potential hepatotrophic factors. For these reasons, the mesentery—the vascularized membrane which secures the intestines—was selected as the best potential site (Fig. 15). 

Eq. 5.12 shows that the biomass-specific metabolic rate of the diffusion-limited cell varies inversely with the square of its size. This means that the cell could potentially increase its specific rate of metabolism 4-fold if the cell diameter were only half as large. The smaller the cell, the less likely it is that its substrate uptake will reach diffusion limitation. Thus, at the low substrate concentrations normally found in marine environments, microorganisms avoid substrate limitation by forming small cells of <1 pm size. Thereby, the bacteria become limited by their transport efficiency of molecules across the cell membrane rather than by diffusion from their surroundings (Fig. 5.6). In the nutrient-poor seawater, where substrates are available only in sub-micromolar and even nanomolar concentrations, free-living... 

Lonisiana s coastal environment, particularly the sediment-water systems, provides a wide range of microhabitats for microbial activity. Sediments range from saline to fresh, well oxidized to strongly reduced, and nutrient poor to nutrient rich. Oxygen availability, pH, temperature, salinity, and nutrient status are a few parameters, which can vary considerably within a coastal sediment system. 

When adhesion of bacteria occurs on the surface of the prosthesis an invasive inflammatory process can be developed. If bacteria proliferation continues, a biofilm is formed, and consequently a three-dimensional structure protects bacteria against the patient s own defense system and from systemic antibiotic therapy [13]. Bacteria do not grow exponentially, but rather exist in a slow growing or starvation state. These microorganisms can produce an extracellular matrix that protects them from a hostile environment, enabling them to evade the host immune system and antibiotic treatment. This biofilm facilitates bacterial survival under nutrient-poor, stressful conditions, which occur in the host, and results in structurally-complex, heterogeneous bacterial aggregates associated with a surface [14,15]. 

The plants, animals and micro-organisms in wetlands are generally adapted to survival in wet habitats. One example is the species of the moss Sphagnum which thrive in such waterlogged, nutrient-poor and acidic environments because of various adaptations. The accumulation of biomass occms because of this saturation which provides a medium that is imsuitable for decomposer organisms (detrivores, see Section 3.6.3). The medium is even more unfavourable if conditions are acidic. Thus the rate of breakdown of organic matter is lower than its rate of accumulation and so organic... 

This profile becomes relevant as agricultural lands are converted. Because A Horizon soils from productive farms are valuable and nutrient-rich, land buyers usually treat them as a mineable resource for resale. Prior to construction, therefore, tractors and land moving equipment scrape the many tons of valuable soil off the surface and cart it away (consider a 100 square yard site scraped to the depth of just a few feet will produce around ten tons of soil at retail, 40-pound bags sell for 6 each). This leaves a far thinner layer of good soil near the surface. Even where intentional removal of topsoil is not conducted, construction typically leads to large-scale erosion of this valuable topsoil layer that, coupled with compaction from heavy equipment and machinery, later makes for a poor growing environment. ... 

This chapter has shown the complexity of the chemical and biological processes around wetland plant roots and the effects of the extreme electrochemical gradient between the root surface and surrounding soil. Models of nutrient uptake by plants in aerobic soil, which treat the root as a simple sink to which nutrients are delivered by mass flow and diffusion but the root not otherwise influencing the surrounding soil, work reasonably well for the more soluble nutrient ions. However, the complexity of the wetland root environment is such that such models are inadequate and more elaborate treatments are necessary. Many of the mechanisms involved are still poorly defined and speculative, but their potential significance is clear. 

The fate of the toxic Gonyaulax species in low-nutrient environments is also poorly understood. On the one hand, G. tamarensis cells can persist in older cultures for months without dividing, presumably under impoverished nutrient conditions. On the other hand, encystment has been observed in natural waters at relatively high nutrient concentrations (18). We thus have no firm foundation on which to base the conclusion that toxic Gonyaulax species encyst to survive the temperature or nutrient variations of temperate coastal waters. Clearly there are many phytoplankton... 

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