Macrofouling

Even when their shells are closed, the animals continue to sense their environment, and as soon as the oxidant level decreases, they reopen and resume siphoning. Continuous chlorination often fails to eradicate these macrofouling creatures because of iatermptions ia the feed, which can occur for various reasons, such as chlorine tank changeover or plugging of feedlines. If the iatermption lasts long enough (1 h or possibly less), the animals have time to reoxygenate their tissues between the extended periods of chlorination. Any oxidant, such as chlorine, bromine, or ozone, eUcits the same response from these creatures. Therefore, only continuous, unintermpted appHcations are successful. 

Hypobromous acid so produced from the naturally occurring bromide in the ocean is rapidly consumed upon demand and is nontoxic to the plant. This natural process helps explain why seaweeds in the ocean are not overcome by adherent microbial biomass and macrofoulants that, for example, rapidly foul the surfaces of ships and piers in the sea. Although chloride is far more abundant than bromide, certain seaweeds preferentially make hypobromous acid in situ. The brominating activity of Laminaria digitata is shown by demonstration (Figure 3) in a replication of the work by Wever, et al.2. 

Keywords CCS technology, C02 capture technologies, C02 storage, C02 uses, macrofoul-ing... 

Macrocyclic lattice hosts, 14 111 Macrocyclic mercuracarboranes, 4 216-217 Macrocyclic oligoesters, 25 125 Macrocyclic polymers, 14 252 Macrocyclic polythioethers, 23 707 Macrocylic ligands, 7 576 Macroemulsions, 10 113 16 433-434 Macrofouling organisms, in industrial water treatment, 26 149-150 Macrolide antibiotics, 15 271-320. See also Macrolides... 

Thermal treatment. See Heat treatment copper-beryllium alloys, 3 654 nickel-beryllium alloys, 3 657-658 of macrofouling organisms, 26 150 Thermal vaporization sources, 24 727 Thermal vaporization rate, 24 725 Thermal waste treatment, 25 831-834, 843-845... 

In addition to pathogens, micro- and macrofoulers negatively impact a variety of macroalgal hosts. Biofouling by the diatom Isthmia nervosa is related to declines... 

Many macrofoulers readily settle on surfaces whether or not they are filmed with bacteria, and chemical surface characteristics mediate the settlement of many common macrofoulers.9 21 28 29 Finally, at all levels of fouling, there are some organisms that settle like dust on all surfaces.8-21 55... 

The result is that barnacles are often the first macrofoulers to colonize a protected surface.100 Once growth of barnacles on toxic metal coatings is initiated, the surface rapidly fails because barnacles act as nontoxic platforms for other organisms. As a result of these kinds of field evidence, the U.S. Navy supported basic barnacle research for almost four decades, and barnacles were the only macrofoulers included in initial studies of natural product antifoulants supported by the U.S. Navy. Most of this work was conducted by the Costlow group at the Duke University Marine Laboratory.47... 

Hadfield, M.G., Carpizo-Ituarte, E., Holm, E., Nedved, B., and Unabia, C., Macrofouling processes a developmental and evolutionary perspective, Abstract 10th International Congress on Marine Corrosion and Fouling, 1999. 

Lindner, E., The attachment of macrofouling invertebrates, in Marine Biodeterioration an Interdisciplinary Study, Costlow, J.D. and Tipper, R.C., Eds., Naval Institute Press, Annapolis, MD, 1984, 183. 

Depending on the velocity of fluid flow, the thickness varies from 10 to 100 pm, and it may cover from less than 20% to more than 90% of the metal surface. Biofilms or macrofouling in seawater can cause redox reactions that initiate or accelerate corrosion. Biofilms accumulate ions, manganese and iron, in concentrations far above those in the surrounding bulk water. They can also act as a diffusion barrier. Finally, some bacteria are capable of being directly involved in the oxidation or reduction of metal ions, particularly iron and manganese. Such bacteria can shift the chemical equilibrium between Fe, Fe2+, and Fe3+, which often influences the corrosion rate. (Dexter)5... 

Forms of corrosion of metals and alloys. It should be noted that organisms are more likely to cause localized than general corrosion because of the differential oxygen cell. In each case, the localized attack was found beneath macrofouling layers. Corrosion of copper, steel, and aluminum anodes was significantly higher when connected to cathodes on which the biofilm was allowed to grow naturally Unexpectedly rapid localized... 

Secondary metabolites are often used as part of an organism s defensive strategy. Secondary metabolites may affect bacterial numbers or promote or deter specific bacteria that provide settlement cues to potential macrofoulers. Secondary metabolites may also deter macrofoulers from settling or kill them once settled. 

In general, conditions favor the development of macrofouling communities, with a continuous flow of aerated seawater that brings food with it to sustain the colonies of living matter. In addition, there is a lack of competition from algae in culverts owing to... 

The problem of macrofouling is not usually associated with heat exchangers in cooling systems [MacNair 1979] but a brief discussion is included here because there are usually implications for the system as a whole and hence heat exchanger operation. 

Whitehouse et al [1985] describe the conditions peculiar to the development of a macrofouling community in power plants. Included are the continuous flow of seawater supplying oxygen and food and reduced salt deposition, the lack of competition from algae in the culverts and a reduction in the presence of predators. The waste products from marine life activity together with decomposition products from dead material, is a potential source of nutrients for microfouling. 

---