Pectinases in leaf degradation by aquatic hyphomycetes I: the field study

Abstract

The colonization-pattern of aquatic Hyphomycetes on five-gram leaf packs of oak and alder submerged in a stream was quantified and compared. There were three series of alder leaves, submerged two weeks apart, and one series of oak. Colonization of leaves by pectolytic bacteria was also measured. There were marked similarities in the colonization of all four series. Total spore counts/g dry wt of leaf rose to a peak followed by a decline. The time taken to peak colonization was slower in oak than in alder, and in alder depended on the level of inoculum in the stream, as did the extent of colonization. Pectolytic bacteria counts followed the pattern of total spore counts, suggesting the exploitation of the same substrates by bacteria and fungi. Temperature and micro-environmental factors influence the overall rate of leaf degradation. Alder I was skeletonized in 10 wks, Alders II and III in 12 wks and oak in 25 wks.The resource was shown to have an upper limit of microbial colonization, and within this 'unit-community' of microbes, there was an association of four dominant species of aquatic Hyphomycetes, together with about ten occasional species. The dominant species are subject to selection from the inoculum available in the stream and the formation and maintenance of the association appears to be the result of competitive interactions between species which results in a dynamic equilibrium. There is a low degree of resource specificity. The species equilibrium is 14 for all series, and species numbers are initially low, rise to a peak, then tend to decline. There is a taxonomic similarity of about 60% between successive stands of all series and between matched stands of alder.

Aquatic hyphomycetes from different substrates: substrate preference and seasonal occurrence

“…Evidence for substrate specificity among aquatic hyphomycetes has been presented by Gonczol (1975Gonczol ( , 1989, Sridhar and Kaveriappa (1988) and, to a lesser extent, Chamier and Dixon (1982), and Bengtsson (1983) has demonstrated habitat (substrate) selection in two species of aquatic hyphomycetes. However, in a New Zealand study, Aimer and Segedin (1985) claimed to have found no evidence of substrate specificity, and Gonczol (1987) suggested that some of the specificity detected in his 1975 study had perhaps been more closely related to changes in stream-water chemistry than to leaf type.…”

“…However, in a New Zealand study, Aimer and Segedin (1985) claimed to have found no evidence of substrate specificity, and Gonczol (1987) suggested that some of the specificity detected in his 1975 study had perhaps been more closely related to changes in stream-water chemistry than to leaf type. The fungal communities of most substrates studied have been found to be dominated by 5 to 10 abundant to moderately common species of aquatic hyphomycetes, although not all substrates are dominated by the same species (Iqbal et al 1979;Sanders and Anderson 1979;Chamier and Dixon 1982;Chamier et al 1984). Chamier and Dixon (1982) and Sridhar and Kaveriappa (1988) suggested that substrate preferences may be more common among aquatic hyphomycetes than substrate specificity.…”

“…The fungal communities of most substrates studied have been found to be dominated by 5 to 10 abundant to moderately common species of aquatic hyphomycetes, although not all substrates are dominated by the same species (Iqbal et al 1979;Sanders and Anderson 1979;Chamier and Dixon 1982;Chamier et al 1984). Chamier and Dixon (1982) and Sridhar and Kaveriappa (1988) suggested that substrate preferences may be more common among aquatic hyphomycetes than substrate specificity. 0067-1940/92/020491$05 .OO The aims of the present study were ( i ) to determine whether any of the aquatic hyphomycetes found in Lees Creek are substrate-specific or whether they occur more generaIly on a wide range of substrates, and (ii) to determine whether distinct seasonal patterns of occurrence of aquatic hyphomycetes are evident and whether these differ between substrates over the year.…”

Initial Colonization, Nutrient Supply, and Fungal Activity on Leaves Decaying in Streams

“…Generally, more than 90% of all spores are produced by one to four species (6). There is some evidence of successional trends (9,20). These changes may be in response to seasonal changes in temperature (32, 42), or rare species might arrive late during the decay of a substrate (2).…”

Vegetative succession and decomposition in reservoirs

“…Maystrenko et at., 1969;Olah, 1972;lJlehlovli, 1976;Morrison et al, 1977;Chamier & Dixon, 1982;Federle & Vestal, 1982). Bacteria are typically first to colonize, and their numbers increase rapidly after a few days.…”