A predictive model for freshwater bioassessment (Mondego River,Portugal)

We sampled macroinvertebrates at 75 locations in the Mondego river catchment, Central Portugal, and developed a predictive model for water quality assessment of this basin, based on the Reference Condition Approach. Sampling was done from June to September 2001. Fifty-five sites were identified as “Reference sites” and 20 sites were used as “Test sites” to test the model. At each site we also measured 40 habitat variables to characterize water physics and chemistry, habitat type, land use, stream hydrology and geographic location. Macroinvertebrates were generally identified to species or genus level; a total of 207 taxa were found. By Unweighted Pair Group Method with Arithmetic mean (UPGMA) clustering and analysis of species contribution to similarities percentage (SIMPER), two groups of reference sites were established. Using Discriminant Analysis (stepwise forward), four variables correctly predicted 78% of the reference sites to the appropriate group: stream order, pool quality, substrate quality and current velocity. Test sites’ environmental quality was established from their relative distance to reference sites, in MDS ordination space, using a series of bands (BEAST methodology). The model performed well at upstream sites, but at downstream sites it was compromised by the lack of reference sites. As with the English RIVPACS predictive model, the Mondego model should be continually improved with the addition of new reference sites. The adaptation of the Mondego model methodology to the Water Framework Directive is possible and would consist mainly of the integration of the WFD typology and increasing the number of ellipses that define quality bands. Handling editor: K. Martens     

The biological assessment of contaminated sediments — the Detroit River example

Contaminated sediments have been found in almost all water bodies which have at some time received, or are presently receiving, waste inputs from urban and industrial sources. In the Laurentian Great Lakes, sediments are classified as contaminated from bulk chemical analysis. The chemical criteria used to evaluate these results are somewhat arbitrary and only partially consider biological impacts. The absence of adequate linkage among sediment contamination, bioavailability, effects on organisms, populations, and ultimately ecosystem health, represents a major barrier to the restoration and protection of aquatic ecosystems.An integrated strategy for the assessment and delineation of contaminated sediments is proposed which provides a comprehensive evaluation of impact, as well as a cost-effective sampling and testing program. The strategy incorporates the triad approach and is to be executed in two stages. Both stages use physical, chemical and biological information; however, the second stage requires more sampling and analyses to specify the severity and extent of the associated problems. To illustrate the type of output anticipated if the strategy is used, data assembled from the Detroit River are presented. They demonstrate that combined analysis of physical, chemical and biological data can be used to link cause and effect between sediment contaminants and benthic communities.     

Collaboration in scientific research: a critical need for freshwater ecology

1. Collaboration means actively working together to achieve things which could not be done alone. This article attempts to provide an overall, unified, guiding framework for collaboration in freshwater ecology by discussing aspects of collaboration at individual and organizational levels, and addressing international linkages.
2. The essential elements of collaboration are communication and trust, and effective project management. Barriers to effective collaboration include competition, organizational cultures and organizational instabilities.
3. The success of collaboration can be measured by tangible benefits such as increased numbers of peer-reviewed publications, the production of working models and a number of intangible benefits.
4. Interactions between individuals lie at the heart of an effective collaboration; organizational arrangements should facilitate this interaction. Some governments are encouraging collaboration to increase cost efficiency and allocate accountability. This trend should continue on an international level.
5. Collaboration is a key to future research in freshwater ecology.     

Predation on snails by three species of triclad and its bearing on the distribution of Planaria torva in Britain

Dugesia polychroa, D. lugubris and Planaria torva preyed upon snails of differing morphologies and while the Dugesia spp. fed approximately in proportion to snail abundance, PL torva was more selective on Potamopyrgus jenkinsi. The incidence of feeding on four snail taxa by the Dugesia spp. was significantly correlated and differed strikingly from that of PI. torva where feeding was related to its annual life cycle. Large peaks of feeding coincided in the Dugesia spp. for the four snail types; this was attributed to snail vulnerability being increased by environmental disturbance. Comparison of feeding by Dugesia spp. in the presence and absence of PI. torva indicated that severe competition was occurring for food with PI. torva having a food refuge in P. jenkinsi. The distribution of PI. torva in Britain is largely confined to productive habitats in the Glasgow-Edinburgh and East Anglia regions. It is concluded that historical rather than ecological events have played the major part in its distribution to date. The strong association of PL torva with port areas and the canal system suggests that it is a recent introduction via the timber trade with Fennoscania.     

The ecology of the Turbellaria with special reference to the freshwater triclads

To attempt a complete review of turbellarian ecology in the time and space available would result in superficiality. Therefore, I have restricted this account to the four basic ecological processes which have and continue to determine flatworm distribution and abundance. These are: (1) historical or zoogeographical events which permit or prevent a species from reaching a habitat; (2) physiological limitations of the species vis à vis the habitat; (3) access to suitable energy sources and (4) the effects of competition, predation and parasitism, referred to collectively as bionomic processes.     

Praziquantel adversely affects protoscoleces of Echinococcus granulosus in vitro

Praziquantel was shown to have adverse effects on protoscoleces of Echinococcus granulosus in vitro. Exposure to one dose of praziquantel at a concentration of 10 micrograms/ml caused protoscoleces to die within 12 to 15 days. Protoscolecidal effects were more marked when cultures were exposed to the drug continuously by the addition of multiple doses. On the basis of these observations, there is a need to reappraise the metacestocidal potential of praziquantel, particularly with regard to the development of new drug regimes employing multiple dose or sustained release schedules. Possible reasons for the reduced susceptibility of protoscoleces and juvenile worms to praziquantel observed in this study are discussed.     

Observations on the comparative ecology of lake-dwelling triclads in southern Sweden,Finland and northern Britain

Summary There are more lake-dwelling species of triclad in northerm Britain (10) than in southern Sweden (7) and the distribution of some differ in the two countries over approximately comparable types of lake. Dendrocoelum lacteum (Müller) occurs in a wide range of lake types in s. Sweden but is restricted to more productive lakes in n. Britain. Polycelis nigra (Müller) (absent from Sweden) has a similar, wide occurrence in Britain. Planaria torva (Müller) is more common in s. Sweden in lakes of all types but particularly in the less productive lakes. The Polycelis species P. tenuis (Ijima) and P. hepta E. H. and Y. Melander, also the Dugesia lugubris species complex show much the same distribution in both areas. Polycelis felina (Dalyell) does not occur in Sweden. The small nuber of Finnish lakes sampled confirm the data for s. Sweden. There is significant correlation between the total abundance of triclads and both the hardness and dissolved matter contents of the Swedish lake waters. Quantitatively the s. Swedish triclad populations compare most closely with those of Mid-Scotland in the n. Britain area.

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Zusammenfassung Es gibt im Norden Britanniens eine grössere Anzahl von Tricladen (10) die Süsswasserseen bewohnen, als in Süd-Schweden (7) und einige Sorten verbreiten sich in ungefähr gleichen Arten von Seen in verschiedenem Maasse in den beiden Ländern. Dendrocoelum lacteum (Müller) erscheint in einer grossen Reihe verschiedenartiger Seen in Süd-Schweden, beschränkt sich aber im Norden Britanniens auf die Seen mit grösserem Reichtum an Lebewesen. Polycelis nigra (Müller) — in Schweden nicht vorhanden-, hat eine ähnlich weite Verbreitung in Britannien. In Süd-Schweden ist in Seen aller Art ein reicherer Bestand an PLanaria torva (Müller), besonders in den Seen mit geringerem Bestand an Lebewesen. Die Polycelis Art P. tenuis (Ijima) und P. hepta E. H. und Y. Melander und auch der Dugesia lugubris Arten-Komplex zeigen dieselbe Verbreitung in beiden Gegenden. Polycelis felina (Dalyell) kommt in Schweden nicht vor. Die kleine Zahl finnischer Seen, denen Proben entnommen wurden, bestätigen die Befunde von Süd-Schweden. Wesentlicher Zusammenhang besteht zwischen der gesamten Reichhaltigheit von Tricladen und dem Gehalt an Kalk und aufgelöster Substanz bei den schwedischen Süsswasserseen. Mengenmässig ist die Verbreitung von Tricladen in Süd-Schweden der im Norden Britanniens am echesten zu verleichen, soweit es sich um Mittel-Schottland handelt.