The macroinvertebrate fauna of the drainage channels of the Gwent Levels, South Wales

SUMMARY. From a survey of the fauna at sixty sites in permanent drainage channels of the Gwent Levels during the spring of 1976 and at some of these sites (thirty-three) during the autumn, speeies and site associations were identified using classification and ordination techniques. Sites in some groups had identifiahly similar environmental characteristics and grouping seemed particularly related to the vegetational stage in the hydrosere, water How and the incidence of salt contamination from the Severn Estuary. Characteristics which were common within particular species groups and whieh, in part, explained their distributions were: adaptation to low oxygen concentrations, food preferences and dispersal mechanisms. Whilst there was some temporal stability in site groups between the spring and autumn surveys, such associations were not idenlical. The oxygen status of channels appeared a major factor determining faunal distribution. Twelve sites, representing a range of channel types, were sampled six times in a 12-month period. Far more species were colleeled within the water column and on plants than in the benthos. Several oligochaetes, e.g. Aulodrilus pluriseta, Dero digitata, Limnodrilus claparedeanus, were not recorded at most sites during the summer probably because of the SUStained lack of oxygen at these sites. Three contiguous reaches of channel were maintained during the period March—October 1977 with different plant cover (no Lemnu; complete Lemna cover: control with partial Lemna cover). The oxygen status of the reaches was different, that with complete Lemna cover being continuously anaerobic near the channel bed for several months, the control reach which had partial Lemna cover being anaerobic for a shorter period and that with no Lemna being only anaerobic at night. Whilst the distribution of macroinvertebrate species was prineipally related to this oxygen status, the control reach whieh was strueturally the most complex, having both submerged and floating plants, contained about twiee as many species as the other reaches during the summer (colleeted in the water column and on plants): benthic samples in this and the reach with complete Lemna cover contained only between zero and two species during the period May- September.     

DEVELOPMENT OF A LEXICON FOR THE DESCRIPTION OF PEANUT FLAVOR

A lexicon of terms to describe desirable as well as undesirable flavors in peanuts has been developed. The lexicon and an intensity rating scale was developed by a 13 member panel of flavor and peanut specialists representing industry and the USDA-Agricultural Research Service. This system is intended to provide definitive, common terminology for use in communicating differences in peanut flavor variables among all phases of peanut research and industry.     

MODELING DIFFERENCES BETWEEN PANELISTS IN USE OF MEASUREMENT SCALES

In sensory data sets, an important source of differences between panelists is in their use of the measurement scale. These differences can be summarized in differences in location , the overall level, and differences in dispersion , the range of the scale used. This paper discusses a method of correcting for these differences by jointly modeling location and dispersion using a see-saw algorithm. This approach is also applicable when scores are not normally distributed and when there is a (nonlinear) relationship between the dispersion and the location. The approach is illustrated with an example for flavor data of freeze-dried and hot-air dried peppers.