Marine environment degradation

The floating debris and beach litter consists of many different materials that, tending to be non-degradable, endure in the marine environment for many years. 

The Degradation of Wood by Metal Fastenings and Fittings , Spring symposium 1970, University of Southampton, Deterioration of Materials in a Marine Environment, Timberlab Paper 27-1970, B.R.E. 

Compared with tar, which has a relatively short lifetime in the marine environment, the residence times of plastic, glass and non-corrodible metallic debris are indefinite. Most plastic articles are fabricated from polyethylene, polystyrene or polyvinyl chloride. With molecular weights ranging to over 500,000, the only chemical reactivity of these polymers is derived from any residual unsaturation and, therefore, they are essentially inert chemically and photochemically. Further, since indigenous microflora lack the enzyme systems necessary to degrade most of these polymers, articles manufactured from them are highly resistant or virtually immune to biodegradation. That is, the properties that render plastics so durable... 

Thompson AS, NJP Owens, JC Murrell (1995) isolation and characterization of methansulfonic acid-degrading bacteria from the marine environment. Appl Environ Microbiol 61 2388-2393. 

Lee, R.F., Ryan, C. (1979) Microbial degradation of organochlorine compounds in estuarine waters and sediments. In Proceedings of the Workshop of Microbial Degradation of Pollutants in Marine Environments. EPA-600/9-79-012. Washington, D.C. 

The environmental behaviour of LAS, as one of the most widely-used xenobiotic organic compounds, has aroused considerable interest and study. As a result, it has been determined that, under certain conditions, LAS compounds are completely biodegradable however, in the marine environment their degradation is known to be slower. The presence of metabolites of the anionic LAS surfactants, the long and short chain SPC derivatives, in the aqueous environment is well known, and as such these degradation intermediates needed to be monitored (and tested for their toxic effects). 

During the wastewater treatment, an oxidative conversion of the surfactant molecules leads predominantly to the formation of polar compounds. They display a particularly high solubility and mobility in the aqueous medium and, therefore, transportation over relatively long distances can occur if they are not further degraded, resulting in the wide dissemination of these pollutants in riverine systems and thus also to estuaries, coastal regions and ultimately the marine environment (see Chapters 6.2 and 6.3). In the latter, the final levels will mainly be influenced by dilution effects and physical removal by precipitation or adsorption [63] because of relatively low microbial activity in this ecosystem compared with fresh water environments [64]. 

The environmental relevance of anaerobic degradability as a property for surfactants is emphasised by the amount that can accumulate and potentially cause effects in anaerobic environmental compartments. The most important final recipient of surfactants not degraded through various processes is the marine environment (sediments). 

The characterisation of LAS degradation in the marine environment requires laboratory experiments, although due to the special characteristics of this compartment (e.g. its high salinity and its normally oligotrophic status) and the numerous variables that affect it, divergent results may be obtained. Marine-specific bacterial communities cannot be cultivated as a whole in standard media due to the difficulty of reproducing original ecosystem conditions where they have been... 

The presence of suspended solid materials increases the extent of LAS biodegradation [13,28], but the rate of the process remains invariable. The influence of the particulate material is due specifically to the increased density of the microbiota associated with sediments. However, suspended solids may also reduce the bioavailability of IAS as a result of its sorption onto preferential sites (e.g. clays, humic acids), although this is a secondary effect due to the reversibility of the sorption process. Salinity does not affect IAS degradation directly, but could also reduce LAS bioavailability by reducing the solubility of this molecule [5], Another relevant factor to be taken into account is that biodegradation processes in the marine environment could be limited by the concentration of nutrients, especially of phosphorus and nitrogen [34],... 

All the strains involved in APEO degradation were of marine origin (i.e. strains requiring sodium). It seems that in the marine environment, the role of freshwater strains originating from sewage is negligible. 

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