CONTENTS
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1

Ostracoda of the Italian ricefields thirty years on: new synthesis and hypothesis
Valeria ROSSI, Giorgio BENASSI, Marco VENERI, Carlo BELLAVERE, Paolo MENOZZI, Antonio MORONI and Kenneth Glencoe McKENZIE

We compare data from a survey of ostracode species carried out during 1994-1998 from Northern Italian ricefields with data from the same area collected in the ’60s. Twentyfive species were recorded during a survey of 19 ricefields in 1994-98 as against 46 species found in 16 ricefields over thirty years ago. Three of these species (Ilyocypris biplicata, Chlamydotheca incisa and Chrissia sp.), as well as six among the 27 species found in the '60s but not recorded during 1994-1998, were found in Italy only in the ricefield habitat. Three species were recorded for the first time in Italy: Hemicypris dentatomarginata, Ilyocypris monstrifica and Chrissia sp. Eight taxa (Chlamydotheca incisa, Chrissia sp., Cypretta turgida, Dolerocypris sinensis, H. dentatomarginata, Isocypris beauchampi, Strandesia spinulosa and Tanycypris pellucida) were considered endemic to South America, Africa or Asia and are thought to have been introduced to Italy with useful plants, notably rice varieties. The recording of these species indicates once again the importance of man as an agent for passive dispersal of ostracode and the role of ricefields as a suitable habitat for new exotic colonising species. Heterocypris incongruens is the most widespread species and several other species (D. sinensis, Cypridopsis vidua, Ilyocypris gibba and Isocypris beauchampi cicatricosa) were found in more than 50% of the ricefields sampled: 40% of the species occur in just one or two ricefields. In Northern Italy today, species similarity between ricefields is inversely related to their geographic distance but is not spatially structured. This may be due to the fact that, in ostracodes, the production of passive dispersal resting eggs con­strains regional differentiation. Species richness is significantly related to the amount of cultivated area. The decrease in species richness observed over the last thirty years or so may be related to the widespread use of pesticides in local current agricultural practices.

2

Limnological characteristics of 56 lakes in the Central Canadian Arctic Treeline Region
Kathleen M. Rühland, John P. Smol, Xiaowa Wang and Derek C.G. Muir

Measured environmental variables from 56 lakes across the Central Canadian Treeline Region exhibited clear limnological differences among subpolar ecozones, reflecting strong latitudinal changes in biome characteristics (e.g. vegetation, permafrost, cli­mate). Principal Components Analysis (PCA) clearly separated forested sites from tundra sites based on distinct differences in limnological characteristics. Increases in major ions and related variables (e.g. dissolved inorganic carbon, DIC) were higher in boreal forest sites in comparison to arctic tundra sites. The higher values recorded in the boreal forest lakes may be indirectly related to differences in climatic factors in these zones, such as the degree of permafrost development, higher precipitation and runoff, duration of ice cover on the lakes, and thicker and better soil development. Similar to trends observed in DIC, substantially higher values for dissolved organic carbon (DOC) were measured in boreal forest lakes than in arctic tundra lakes. This was likely due to higher amounts of catchment-derived DOC entering the lakes from coniferous leaf litter sources. Relative to arctic tundra lakes, boreal forest lakes had higher nutrient concentrations, particularly total nitrogen (TN), likely due to warmer conditions, a longer growing season, and higher precipitation, which would enhance nutrient cycling and primary productivity. Results suggest that modern aquatic environments at opposite sides of the central Canadian arctic treeline (i.e. boreal forest and arctic tundra) exhibit distinct differences in water chemistry and physical conditions. These limnological trends may provide important information on possible future changes with additional warming.

3

Distribution and ecology of calanoid species in relation to morphometric and chemical characteristics of lakes and ponds of the Northern Apennines (Italy)
Silvia TAVERNINI, Elena FRATTA, Franco SARTORE and Giampaolo ROSSETTI

In 1999 a limnological campaign was carried out in 89 water bodies located in 8 valleys of the Northern Apennines (provinces of Genua, Piacenza, Parma and Reggio Emilia) at an altitude between 877 and 1772 m a.s.l. This survey took into account permanent lakes, but also temporary and ephemeral water bodies which had been scarcely considered in hydrobiological studies previously carried out in this area. Most of the biotopes were visited seasonally during the ice-free period (May - November). The aim of this research was to define the relationships between morphometric features, lithology, hydroperiod and chemical characteristics of the biotopes and the distribution of the three species of calanoid copepods reported in the Northern Apennines, i.e. Mixodiaptomus kupelwieseri, M. tatricus and Eudiaptomus intermedius. The two most common species, M. kupelwieseri and E. intermedius, show an overlap in their altitudinal distribution. However, the former species widely occurs in very shallow, temporary or ephemeral water bodies and the latter clearly prefers permanent, relatively deep waters. Also the water inonic concentration influences the distribu­tion of these two diaptomids, while concentrations of dissolved inorganic nutrients seem to have a negligible effect. Mixodiaptomus tatricus was found only in two shallow ponds beyond 1700 m a.s.l. Co-occurrence of E. intermedius and M. kupelwieseri has been observed only in a pond, but the two species are not found at the same time. The proportion of subitaneous and resting eggs laid in different seasons was analysed in populations of E. intermedius. The voltinism of this species varies according to the duration of the filling period and the productivity of the water bodies. The persistence of diaptomids in the study area has been evaluated through the comparison with distributional data available from the 1950s for most of the permanent lakes and some temporary habitats. Populations appear to be stable over time also in scarcely predictable environments as temporary pools, although in some cases calanoids have disappeared from biotopes severely affected by anthropogenic impacts.

4

Adaptive strategies in populations of Chirocephalus diaphanus (Crustacea, Anostraca) from temporary waters in the Reatine Apennines (Central Italy)
Graziella MURA, Giovanni FANCELLO and Secondina DI GIUSEPPE

To investigate the relationship between the adaptive strategies of Chirocephalus diaphanus (Crustacea, Anostraca) and the environmental characteristics of its habitat, we studied two populations living in high-altitude biotopes with very different characteristics, i.e. a semipermanent pool (Tilia Lake) and a temporary one (Illica Plain Pool), and we examined the essential features of their biological cycles (growth rate, reproductive biology, sex ratio and life cycle). The results show that the two populations adjust to the biotopes in which they live, fully exploiting the brief period available for development, in agreement with hypotheses formulated in studies of other colonizers of temporary environments. The strategy adopted by the Chirocephalus diaphanus population of Tilia Lake, a predictable and relatively constant environment, is similar to the k type, characterized by slow growth, late reproduction and a long life cycle. In contrast, the Illica Plain population presents rapid growth, precocious reproduction and a short life cycle, since it is highly dependent on the precariousness and unpredictability of the pool in which it lives.

 5

Absorption spectroscopy of colored dissolved organic carbon in Georgia (USA) rivers: the impact of molecular size distribution
Yosef Z. YACOBI, James J. ALBERTS, Monika TAKÁCS and Michelle McELVAINE

Dissolved organic carbon (DOC) was collected in six rivers that transect the coastal plain of Georgia in July 1999 and February 2000. DOC concentrations ranged from 4.9 to 40.7 g m^-3 and from 7.1 to 40.5 g m^-3, respectively. The absorption coefficient at 440 nm was highly correlated with DOC concentration, suggesting that the optical parameter may be utilized for rapid estimation of DOC in these waters. The isolated DOC was separated into fractions of operationally defined molecular size, using an ultrafiltration technique that yielded three fractions: <10 ("small"), 10-50 ("medium") and >50 ("large") kilodalton. The smallest fraction was the most abundant (>50%) in 4 rivers in July and in all rivers in February, and considerably more abundant than in previous years. The wavelength-dependent absorption of the total DOC and its fractions showed approximately uniform shape of a curve declining expo­nentially with the increase of wavelength. The average slope of logarithmically transformed curves was 0.0151 and 0.0159 nm^-1, for the material collected in July and February, respectively and showed a dependence on DOC molecular size. In unfractionated DOC samples, the mass-specific light absorption determined at 440 nm was on average 0.33 m² g^-1 in July, and 0.26 m² g^-1 in February. The mass-specific absorption coefficient in all fractions ranged between 0.085 and 1.347 m² g^-1 in July and between 0.085 and 1.877 m² g^-1 in February, and was positively correlated with the molecular size of the measured samples. The results of the reported study clearly suggest that the specific absorption coefficient of the yellow substance is an outcome of the relative contribution of its different size fractions.

6

Topical observations on centric diatoms (Bacillariophyceae, Centrales) of Lake Como (N. Italy)
Wolfram SCHEFFLER and Giuseppe MORABITO

In 2001 a qualitative analysis of the centric diatoms in Lake Como was made. In this work 15 taxa of the genus of Stephanodiscus, Cyclotella, Melosira, Aulacoseira and Stephanocostis were recorded. Among them the taxa Cyclotella pseudostelligera, C. comensis, C. comensis morphotype minima, C. costei, Stephanodiscus minutulus and Stephanocostis chantaicus were of special interest to us with regard to their morphological and taxonomical features. Morphological variability as well as taxonomical classification is discussed. A short appraisal of the ecological state of the Lake Como is given. Without any further critical considerations all centric taxa of Lake Como recorded from fossil to up-to-date collections are compiled.  

7

Trace element concentrations in freshwater mussels and macrophytes as related to those in their environment
Oscar RAVERA, Roberto CENCI, Gian Maria BEONE, Marta DANTAS and Paolo LODIGIANI

This study was primarily designed to contribute to the debate "Do accumulator species reflect the element contamination level of their environment?" This research was carried out: 1) to know the distribution of 15 trace elements and calcium in shell and soft tis­sues of three species of freshwater mussels and macrophytes; 2) to compare the accumulation capacity of each trace element by mus­sels and by eight species of macrophytes and 3) to test the relationships between the metal concentrations in the mussels and macrophytes and those in water and sediments. The variability of element residues in the mussels is the major limit to accumulator moni­toring. The most important causes are: seasonal cycle, physical environment and biological factors such as the size, age and growth rate. This research was designed to eliminate the consequence of variability deriving from the season and the environment. To this end the mussels and macrophytes were collected at the same time from the same habitat: Ranco Bay, Lago Maggiore, Northern Italy. In addition, the element concentrations in more size-classes of the most abundant mussel species (Unio pictorum and Dreissena polymorpha) were measured. Trace elements were analyzed by Inductive Coupled Plasma-Mass Spectrometry (ICP-MS). By arranging the data in sequences of decreasing element concentrations in the organisms as well as in water and sediments, we were able to compare the accumulating ability of the tested species and evaluate their capacity to reflect environmental availability. Nei­ther the sequences in the shell nor those in the tissues were similar to the sequence in the water. The differences between the se­quences of the mussel tissues and those of the sediments were less striking than those between shells and sediments. Similar results were obtained by macrophytes. In conclusion, the results of this study (which mimics the monitoring practice) prove that bioaccumulators cannot be used to evaluate the pollutant levels of the environment at the time of collection, since no relationship between metal concentrations in the species and those in the water was found and the relationship with the sediments was very weak. Bioaccumulators can be regarded as a useful tool in long-term studies to follow pollutant variations in the same environment or when sub­stantial differences in pollutant concentrations in different environments were found. This monitoring method yields reliable results to detect new pollutants contaminating the environment, such as artificial radioisotopes, or to follow year to year variations by ana­lyzing pollutant concentrations in the shell layers.

8

Ecological profiles of wetland plant species in the northern Apennines (N. Italy)
Alessandro Petraglia and Marcello Tomaselli

Eighteen selected species occurring in the wetlands of the northern Apennines were studied by the ecological profile method. By this method, it is possible to identify the ecological factors mostly influencing species distribution within a particular vegetation. Moreover, it is possible to evaluate both ecological amplitude and ecological preferences of species. Ecological profiles were built for three factors (altitude, pH and electrical conductivity) from a data set of 265 phytosociological relevés, used for altitude, and from a set of 92 measures, carried out in selected sites, for idrochemical variables. By numerical classification, based on chord dis­tance and minimum variance, the ecological species groups for each factor were individuated. Subsequently, they were ordered by correspondence analysis for detecting relationships between ecological groups and classes of factors. By applying a goodness-of-fit test to ecological profiles, the species significantly deviating from uniformity were detected. They can be regarded as indicators for the corresponding ecological factor. We found seven indicator species for altitude (Carex nigra, C. rostrata, Juncus filiformis, J. alpino-articulatus, Eriophorum latifolium, E. angustifolium and Warnstorfia exannulata), four indicator species for electrical con­ductivity (Campylium stellatum, Carex tumidicarpa, Eriophorum latifolium and Juncus alpino-articulatus) and one indicator species for pH (Sphagnum capillifolium). The ecological profiles of the wetland species in the northern Apennines were compared with those reported in literature for the same species from the Alps (namely Dolomites). In this way, a certain degree of ecological shift in several wetland species of the northern Apennines was documented. For altitude, it is possible to explain the shift considering the reduced elevational amplitude of northern Apennine wetlands with respect to those of the Alps. For pH, Sphagnum capillifolium occurs in less acidic habitats than in the Alps, probably due to the absence of ombrotrophic mires, and Viola palustris occurs mostly in neutro-basiphytic habitats. Some hypotheses to explain the ecological behaviour of this last species were proposed.

 9

Blooms of the dinoflagellate Glenodinium sanguineum obtained during enclosure experiments in Lake Tovel (N. Italy)
Marco Cantonati, Massimiliano Tardio, Monica Tolotti and Flavio Corradini

Freshwater red tides due to dinoflagellates are less common than their marine analogues, which are usually a serious problem and can even be toxic. This was not the case for Lake Tovel in the Adamello-Brenta Natural Park (Southern Alps, Italy), where the dinoflagellate Glenodinium sanguineum Marchesoni accumulated carotenoids (astaxanthin-like compound) and caused a spectacu­lar and regular "summer reddening", which suddenly ceased in 1964. Today Lake Tovel is a temperate, meromictic (with dimictic mixolimnion), oligotrophic mountain lake, characterised by marked water level fluctuations. G. sanguineum is still present in the lake, although with markedly lower densities in comparison to the pre-1965 period. Enclosure studies were carried out to identify the main factors regulating the blooms. In 1998, by means of phosphorus enrichments, it was possible to obtain a marked increase in numbers of G. sanguineum. Phosphorus additions in similar enclosures in 1999, when weather conditions during the summer were not optimal (mostly cloudy with frequent rainfalls), did not have the same effect, since species known to thrive in spring or under ice-cover developed. In summer 2000, by attenuating light in one of the enclosures, it was shown that irradiance conditions strongly interacted with phosphorus availability in determining the species that  dominated the phytoplankton. In summer 2001, G. sanguineum increased again in the enclosure enriched with phosphorus. Nitrogen was observed to become a limiting factor only in conditions forced by phosphorus additions. From the first four years of in situ experiments, we concluded that phosphorus and light conditions were among the key factors controlling the proliferation and the dominance of G. sanguineum.

10

Ecology of some mire and bog plant communities in the Western Italian Alps
Luca MISERERE, Franco MONTACCHINI and Giorgio BUFFA

During a mire vegetation study, conducted mainly in the subalpine-alpine sector of the Western Italian Alps, the ecology of sev­eral plant communities and numerous moss species of this kind of vegetation was evaluated. The study area covered the Piedmontese sector of the Graian Alps, the eastern sector of the Aosta Valley as well as certain localities of the Pennine Alps, the Canavese district and the Maritime Alps. They have a rocky substratum representative of the various regional lithologies and include the main sectors characterised by the highest precipitation. Three hundred and twenty two relevées were made using the phytosociological method and the pH and the conductivity of the water table and its depth were measured directly. Cluster Analysis allowed a classifi­cation of the samples and the identification of various groups of plant communities. Ordination performed by DCA and CCA allowed us to identify the ecological features of the various plant communities by using the values of the main environmental parameters, measured directly in the field, and certain climatic parameters (altitude and mean annual precipitation) available. The use of cli­matic parameters is an important result for identifying communities which show greater oceanicity, something that is underlined also by the presence of indicator species such as Sphagnum papillosum and S. subnitens. Furthermore the communities are arranged in a "poor-rich" gradient, and are also profoundly influenced by depth to water table which is inversely correlated to the pH. Therefore we find certain kinds of communities all with a very low water table and which are little affected by its chemistry. Other groups share the fact that the water table is outcropping or near the surface and are distinguishable for their pH values and conductivity. We dis­cuss the different response of the bryophytes and vascular plants of these communities to the environmental parameters considered, in light of their anatomic and functional differences. Bryophytes are more sensitive to environmental and climatic parameters whilst vascular plants are mostly ubiquitous in the relevées with a greater ecological plasticity.

11

Ecological distribution of pelagic copepods and species relationship to acidification, liming and natural recovery in a boreal area
Jens Petter NILSSEN and Svein Birger WÆRVÅGEN

Distribution and ecology of pelagic copepods were studied in a boreal area strongly affected by acidification in southern Norway. Differential regional composition of bedrock geology and Quaternary deposits combined with liming have produced aquatic sites with contrasting acidification and recovery histories. The omnivorous species Eudiaptomus gracilis showed a striking ability to tolerate both acidification and chemical recovery. The predominantly carnivorous species Heterocope saliens increased numerically during acidification, both because it is tolerant to acidic environments and because fish predation diminished or disappeared alto­gether. After chemical recovery, H. saliens, having an endogenous egg-bank, most readily produced viable populations with numeri­cal abundance depending upon fish predation pressure. Thermocyclops oithonoides and Cyclops scutifer were negatively affected by strongly acidic environments, whereas Mesocyclops leuckarti tolerated acidic conditions better. All three cyclopoid species increased in abundance after chemical recovery, most probably from small residual populations. The hypolimnetic C. scutifer faced dispersal problems in reestablishing following liming. Deep lakes (>20 m) harboured considerable residual populations of C. scutifer which recovered rapidly to pre-acidic conditions. Cyclops abyssorum inhabited the pelagial during early recovery of formerly chronically acidified lakes as a fugitive species, probably due to rapid dispersal capacities. Littoral cyclopoids, such as Acanthocyclops vernalis and Diacyclops nanus, were commonly distributed in the free waters of the most acidic lakes (pH = 4.5-4.8), but disappeared from the pelagial shortly after chemical recovery. The total community of pelagic copepods forms a promising tool to identify historical acidification and trajectories of recovery in the freshwater environment.

12

Autumn physical limnological experimental campaign in the Island Mainau littoral zone of Lake Constance
Irina CHUBARENKO, Boris CHUBARENKO, Erich BÄUERL⁾, Yongqi WANG and Kolumban HUTTER

From October 12^th to November 19^th 2001 a hydrophysical field measurement campaign was carried out in the littoral zone of Lake Überlingen and the Upper Lake Constance around the Island Mainau and in the adjacent aquatic area. Measurements involved (i) deployment of current meters, thermistors and thermistor chains at fixed positions, (ii) CTD-towing with the boat in the subsur­face layer, (iii) CTD profiling at selected positions and deployment of drifters at selected depths and positions around the Island Mainau. The measurements that were conducted are described and illustrated by typical plots. The data as well as closer description of the campaign are public domain and can be downloaded for use through Internet.