Production of microcystins in calcareous Mediterranean streams: The Alharabe River,Segura River basin in south-east Spain

The development of epilithic cyanobacteria communities in a Mediterranean calcareous stream in the province of Murcia (SE Spain) was studied during the course of one year in an attempt to clarify the environmental variables that influence the production of microcystins. The predominant cyanobacteria were species of Rivularia, which formed conspicuous colonies throughout the year. Seasonally, other species were abundant: Schizothrix fasciculata, Tolypothrix distorta and Phormidium splendidum. All the species collected produced microcystins to a varying degree (up to five varieties), while the benthic community as a whole produced concentrations as high as 20.45 mg m⁻². At the same time, the presence of microcystins dissolved in water was confirmed. Among environmental variables, air temperature and silicate content were positively and strongly correlated with total microcystins, while nitrite, nitrate, orthophosphate, calcium and flow were negatively correlated with them. Dissolved microcystins were negatively correlated with microcystin LR, P.A.R. and total phosphorus and positively with rainfall. The production of microcystin YR seems to be regulated by different factors from those regulating the other main varieties (microcystin LR and microcystin RR). The data obtained indicate that all the tested benthic cyanobacteria produced microcystins in this shallow calcareous stream, which may contribute to their predominance in the prevailing conditions. The accumulation of microcystins in mucilaginous colonies of other groups of algae poses new questions concerning the possible ecological function of these compounds and needs further study.     

Diatom Communities and Water Quality Assessment in Mountain Rivers of the Upper Segre Basin (La Cerdanya,Oriental Pyrenees)

Epilithic diatoms of mountain rivers from the upper Segre catchment (Oriental Pyrenees) were studied in 1998, during three different seasons: March, July and September. Four rivers, the river Segre and its three most important tributaries, Duran, Molina and Querol, were sampled in upstream and downstream stretches. The diatom communities were comparable in all upstream stretches of these mountain rivers draining siliceous substrates. Dominant taxa were Achnanthidium subatomus, Diatoma mesodon, Encyonema cf. minutum, E. silesiacum, Fragilaria arcus, F. capucina, Gomphonema calcifugum, G. pumilum, Meridion circulare and Nitzschia pura. Changes in water quality in the downstream stretches lead to the appearance of pollution tolerant taxa, such as Eolimna minima, Gomphoneis minuta, Navicula gregaria, and Nitzschia inconspicua. As a result, the values obtained with the diatom water quality indices (IPS Specific Polluosensitivity Index, CEE and IBD Biological Diatom Index) decreased. The diatom community composition and the derived water quality values did not change in the upstream stretches over the year. In contrast, significant changes were observed in the downstream stretches with best water␣quality in July, during high flows due to melting snow, and worst values in September, during low␣discharge. The diatom indices, especially the IPS, showed a good performance in these mountain rivers.     

Microfaunal communities in three lowland rivers under differing flow regimes

Microfaunal samples were collected from within the channels of three rivers in north eastern Victoria, Australia (the Murray, Ovens and Broken Rivers) as a component of a study examining the effects of flow on the biota of lowland rivers in Australia. Samples were collected from the water column of the river channel and slackwaters and from the layer of water immediately above the bottom sediment of the slackwaters. There was no connectivity between the river channel and the floodplain wetlands for all three rivers during the sampling period. Substantial numbers of microfauna were resident in the slackwaters of all three rivers, with the greatest densities occurring close to the bottom sediment, with densities often exceeding 1000 animals l⁻¹ whereas in the plankton samples densities were usually less than 500 animals l⁻¹. The presence of large and diverse microfaunal communities and the lack of connectivity between the river channel and associated floodplain wetland indicate that these communities are capable of persisting and recruiting within riverine channel slackwaters.     

Life‐history variability of non‐native centrarchids in regulated river systems of the lower River Guadiana drainage (south‐west Iberian Peninsula)

Life‐history variability of two non‐native centrarchids, pumpkinseed Lepomis gibbosus and largemouth bass Micropterus salmoides, was evaluated in three stream stretches of the lower River Guadiana drainage (south‐west Iberian Peninsula) with different degrees of regulated flows. Abundance, condition and population structure differed among populations for both species, but invasion success was lower in the least regulated river. Lepomis gibbosus were abundant and had multiple age classes in the three river sites, whereas M. salmoides were less abundant and mainly represented by young‐of‐the‐year fish. Juvenile growth in L. gibbosus was similar in all three populations, though longevity was slightly greater in the population from the River Guadiana mainstream. Lepomis gibbosus exhibited a long reproductive season, but the duration of season, size at maturity and reproductive effort varied among populations. The life‐history differences found demonstrate the importance of species adaptation to local conditions which might favour their invasion success. Lepomis gibbosus were more adaptable and resilient to local conditions, whereas M. salmoides seemed dependent on reservoirs and large rivers for maintenance of riverine populations.     

Eutrophication in Australian Rivers, Reservoirs and Estuaries – A Southern Hemisphere Perspective on the Science and its Implications

Australian science has made rapid advances in the last decade in understanding eutrophication processes in inland waters and estuaries. The freshwater research on which these advances are based was triggered by well-publicised blooms of cyanobacteria during the 1980s and early 1990s, particularly a 1000 km long bloom on the Darling River. In estuaries the study which greatly enhanced our understanding but simultaneously served to stimulate further research into estuarine eutrophication, the Port Phillip Bay Study, was initially designed to address perceived problems of toxicants in the Bay but provided profound insights into drivers for, and ecosystem responses to, eutrophication. Subsequent estuarine research has largely been stimulated by management questions arising from Australia’s increasing coastal development for residential purposes. The research has shown that some of the beliefs extant at the time of the blooms were incorrect. For example, it is now clear that stratification and light penetration, not nutrient availability, are the triggers for blooms in the impounded rivers of southeastern Australia, although nutrient exhaustion limits the biomass of blooms. Again, nitrogen seems to play as important a role as phosphorus does in controlling the biomass of these freshwater blooms. The research has also shown that aspects of eutrophication, such as nutrient transport, are dominated by different processes in different parts of Australia. Many of the biophysical processes involved in eutrophication have now been quantified sufficiently for models to be developed of such processes as sediment-nutrient release, stratification, turbidity and algal growth in both freshwater and estuarine systems. In some cases the models are reliable enough for the knowledge gained in particular waterbodies to be applied elsewhere. Thus, there is now a firm scientific foundation for managers to rely upon when managing algal blooms. Whilst these findings have already been presented to managers and communities throughout Australia, there is still a considerable way to go before they are absorbed into their modus operandi.     

Seasonality in foraging behaviour of Constrictotermes cyphergaster (Termitidae, Nasutitermitinae) in the Caatinga of Northeastern Brazil

The foraging activity of Constrictotermes cyphergaster was investigated in the Caatinga of Northeast Brazil. Eight colonies were monitored for seven days, during both dry and wet seasons. Foraging activity occurred in exposed columns at night, generally between 22:00 and 05:00 h. During the wet season, foraging activity was significantly higher, with one bout every 1.6 ± 0.2 days, than the dry season, when foraging bouts were performed every 1.9 ± 0.3 days. Foraging activity throughout the study colonies presented high temporal synchronization. In both seasons, foraging was negatively correlated with air temperature and positively correlated with humidity. The foraging trails were often re-utilized and ranged from 1 to 18.5 meters in length. No difference between seasons in the area potentially utilized by the study colonies was observed. Approximately 51000 individuals participated in the foraging bout during the dry season, whereas some 87000 individuals participated in the foraging bout during the wet season. This corresponds to 43 and 74% of the estimated total nest population for the dry and wet seasons respectively. The average ratio soldiers:workers during foraging was 1:1.2 in the dry season and 1:2 in the wet season. The higher frequency and number of individuals foraging during the wet season in the present study are likely to be a strategy from C. cyphergaster to store energy reserves to be utilized during the dry season. Received 28 November 2005; revised 29 May 2006 and 16 August 2006; accepted 1 September 2006.     

Linking organism groups – major results and conclusions from the STAR project

Here we summarize results of the EU funded research project STAR concerning the suitability of different organism groups (fish, benthic invertebrates, macrophytes, diatoms) for monitoring European rivers. In a general way, the suitability of the organism groups is classified by monitoring type, stress type, river type, temporal scale and taxonomic resolution. For example, although all organism groups are affected by acidification, the relatively low species richness of fish and macrophytes in small mountain streams makes these two groups less suitable, and, hence, we argue that benthic diatoms and/or invertebrates may be considered as more robust indicators. Similar, lines of reasoning are given for a number of stressor and stream types.     

Responses of lotic periphyton to pulses of phosphorus: P‐flux controlled growth rate

1. The response of stream periphyton to the addition of limiting nutrients has been the focus of many studies. However, the influence of pulsed nutrient additions has not previously been examined. This study investigates the biomass accrual and physiological responses of phosphorus‐limited lotic periphyton to hourly phosphate fluxes. 2. Two pulsing experiments were conducted: (i) a variable flux trial that compared variable hourly P‐fluxes, delivered either continuously at different concentrations or at the same concentration but in pulses of differing duration per hour and (ii) a constant flux trial that compared periphyton responses at a set hourly P‐flux but delivered in pulses of varying concentration and duration. 3. Growth response and alkaline phosphatase activity during the variable flux experiment showed that periphyton responds to the hourly integrated flux of phosphorus, regardless of whether the nutrient is supplied in short concentrated pulses or continuously at much lower concentrations. 4. The constant flux experiment examined the pulse period required to attain maximum biomass for a given phosphorus flux. Periphyton response to 5‐min pulses of phosphate per hour approximated the maximum biomass as that attained when the same hourly flux was added continuously. Compared with the control, there was also a substantial increase in biomass with pulses of only 1 min each hour. These results demonstrate that the hourly average phosphate concentration to which periphyton communities are exposed is paramount in determining P‐limited growth dynamics. 5. Species composition was not significantly different among treatments in each experiment; however, the design was to evaluate monotonic response with increasing phosphorus flux and species diversity may not respond monotonically. The data are therefore preliminary but suggest the need to determine if species diversity is generally lower when there are brief pulses of phosphate. Unlike pulse experiments that mimic lentic situations, nutrient additions were not used to completion and species success and composition was more dependent on their ability to acquire limiting nutrients rapidly rather than on their ability to take up nutrients at the lowest concentration.     

Ochoterenella esslingeri n. sp. (Nematoda: Onchocercidae: Waltonellinae) from Bokermannohyla luctuosa (Anura: Hylidae) in Minas Gerais,Brazil, with notes on Paraochoterenella Purnomo & Bangs, 1999

The waltonelline Ochoterenella esslingeri n. sp., a filarial parasite of the anuran Bokermannohyla luctuosa in Minas Gerais, Brazil is described. Several characters distinguish this new species from the 15 species presently included in the genus: the cuticular ornamentation of the female that is restricted to the posterior region of the body, the irregular arrangement of the small, rounded bosses, the postoesophageal vulva, the short glandular oesophagus, the size and shape of the microfilariae, the long left spicule and high spicular ratio. Irregularly arranged, tiny, rounded bosses are common in the monotypic genus Paraochoterenella from an Indonesian ranid, which is not well defined but likely valid. In the Neotropical Realm, the type hosts of the species of Ochoterenella are Hylidae (O. esslingeri n. sp.), Leptodactylidae (two species) and the remaining 13 species were described from the giant toad Rhinella marina (Bufonidae).