Seasonal variation in benthic macroinvertebrate assemblages and water quality in an Afrotropical river catchment,northeastern Tanzania

Population growth and economic development have resulted in increased water demands, threatening freshwater resources. In riverine ecosystems, continuous monitoring of the river quality is needed to follow up on their ecological condition in the light of water pollution and habitat degradation. However, in many parts of the world, such monitoring is lacking, and ecological indicators have not been defined. In this study, we assessed seasonal variation in benthic macroinvertebrate assemblages in a tropical river catchment in northeastern Tanzania, which currently experiencing an increase in agricultural activities. We examined the potential of in-stream environmental variables and land-use patterns to predict the river macroinvertebrate assemblages, and also identified indicator taxa linked to specific water quality conditions. Macroinvertebrate abundance, taxon richness and TARISS (Tanzania River Scoring System) score were higher in the dry season most likely due to higher surface runoff from agricultural land and poorer water quality in the wet season. In the wet season macro invertebrates seem to be limited by chlorophyll-a, oxygen and phosphorous while in the dry season, when water flow is lower, nitrogen and turbidity become important. Substrate composition was important in both seasons. Given the fact that different selective filters limit macroinvertebrate assemblages in both seasons, a complete picture of water quality can only be established by monitoring in both seasons. Riparian buffer zones may help to alleviate some of the observed negative effects of agricultural activities on the river system in the wet season while limiting irrigation return flows may increase water quality in the dry season.     

Marine ciliate community in relation to eutrophication of coastal waters in the Yellow Sea

We assessed the potential of marine ciliate community as an indicator to coastal water quality using water samples collected from four stations in the Yellow Sea in the summer 2000. The four stations were characterized by different levels of pollution. The ciliate communities consisted primarily of tintinnids and aloricate ciliates that were <30 μm. A total of 78 species were classified: 55 species at Station 2, 51 species each at Stations 1 and 4, and 47 species at Station 3. The mean number of species at each site was 29.2±2.0 (Station 1), 28.5±2.9 (Station 2), 27.8±1.7 (Station 3), and 24.5±2.3 (Station 4). The abundance was highly variable: 19 331±11 187 ind./L at Station 1, 7 960±5 639 ind./L at Station 2, 29 015±12 999 ind./L at Station 3, and 8 190±4 658 ind./L at Station 4. Our results suggest that neither the simple chemical analysis (e.g. chemical oxygen demand, dissolved inorganic nitrogen, and phosphate) nor the eutrophication/pollution index adequately described the water quality at the four stations. The same was true of the number of species and their abundance, both of which had no correlation with the chemical indices. In contrast, Margalef’s diversity index values (3.12 at Station 2, 2.89 at Station 1, and 2.64 at Stations 3 and 4) generally discriminated the water quality status of the four stations. The difference in water quality among the stations was strongly supported by the pattern of species richness (i.e. the total number of species) of ciliates at each station. Our evaluation was consistent with the results of long-term water quality monitoring at the four stations. With increasing eutrophication, we observed also a compositional and functional shift in the ciliate assemblages from algivorous oligotrich/choreotrich to nonselective-omnivorous gymnostomatids to bacterivorous-detrivorous scuticociliatids. Thus, ciliates may be used to indicate the coastal water quality status of a given site.     

Biological assessment of rivers in the Manawatu‐Wanganui region of New Zealand using a predictive macroinvertebrate model

This study presents a river invertebrate and classification system (RIVPACS) type bioassessment methodology for the Manawatu‐Wanganui region of New Zealand. Aquatic macroinvertebrates and related physico‐chemical data were collected at 127 sites, with minimal human impacts (reference sites) in 2000. The reference sites were classified into five groups based on their macroinvertebrate data using TWINSPAN. These biotic groupings were then applied to their corresponding physico‐chemical data and discriminant functions were obtained to assign sites into the biotic groups using the physico‐chemical data. The discriminant functions correctly allocated 72% of the sites to the correct classification group using a jack‐knife validation. The probabilities from the discriminant functions were used to predict macroinvertebrate assemblages and these were compared with observed macroinvertebrate assemblages. The model was then used to assess the health of 29 test sites with known impacts. All test sites were assessed as impacted based on the 10th percentile of the reference data. To evaluate the temporal reliability of the model, data available for 11 sites sampled in 1997 and 2000 were run through the model. The results of this comparison showed little variation in O/E ratios over time and the two sites classed as impacted in 1997 were also classed as impacted in 2000.     

Vertical Distribution Patterns of Trace Elements in an Urban Environment as Reflected by their Accumulation in Lichen Transplants

The results of an investigation about the vertical distribution patterns of selected trace elements in an urban environment, as reflected by their accumulation in lichen transplants, are reported. Thalli of the lichen Pseudevernia furfuracea were transplanted in 2 sites in the urban area of Thessaloniki (N Greece), subjected to very different traffic loads: 1) Tsimiski, downtown of Thessaloniki, at one of the busiest streets of the city, a street canyon 2) Toumba, far from the city centre, at the edge of the city, at an open street. In each site, thalli were suspended along a vertical transect at 3, 6, 9 and 12 m, and retrieved after one year. The results showed that while at Toumba the elemental composition of lichen samples was essentially influenced by natural occurrence, mainly airborne soil dust, at Tsimiski also anthropogenic input of pollutants determined by vehicle traffic was involved for some elements such as Cd, Cu, Ni, Pb and Zn. The vertical distribution patterns of heavy metals accumulated in lichens showed that in general elevation has no statistically significant influence on the concentration of most metals, but this was not true for Pb, whose concentrations increased with increasing elevation from ground. Residents may thus be more exposed to high concentrations of Pb than pedestrians.     

Diversity of Epiphytic Lichens and Hg Contents of Xanthoria parietina Thalli as Monitors of Geothermal Air Pollution in the Mt. Amiata Area (Central Italy)

The diversity of epiphytic lichens and mercury concentrations in lichen samples were measured to monitor the release of airborne pollutants from the industrial exploitation of geothermal resources in the Mt. Amiata area (Italy). The lichen biodiversity showed a general condition of moderate environmental alteration around the geothermal power plants, contrasting with the low environmental alteration of the remaining sites investigated. According to the accumulated Hg in lichen thalli, it was possible to estimate mean Hg and H₂S concentrations in the air, which resulted in very good agreement with values measured instrumentally. Based on these data and the correlation between lichen diversity values and Hg concentrations in lichens, it was possible to calculate the threshold of 8 μg/m³ H₂S as responsible for the worsening from low to moderate environmental alteration according to the biodiversity of epiphytic lichens, and to infer that around geothermal power plants, although not toxic to humans, H₂S concentrations are such to alter the nasal quality of the air. Based on the growth rate of X. parietina, it was possible to convert Hg concentrations into estimates of average Hg deposition rates, which showed fluxes of the order of 65–100 mg/ha/y, indicating a dispersions factor of about 10⁴ for the Hg emitted from the geothermal power plants.     

Sigmoid wave transitions at alpine treeline

Ecotones that are controlled by a single environmental gradient or a set of correlated environmental factors are hypothesized to show a sigmoid wave form in percentage cover as the ecotone is crossed. This study investigates the sigmoid wave hypothesis at the alpine treeline in Glacier National Park, Montana, USA. We find that approximately half of the sampled locations exhibit a sigmoid wave form in percentage cover across the ecotone. These results indicate that in some cases treeline is controlled by a single environmental gradient or a set of correlated environmental factors. However, in other cases, additional factors that are not correlated with the primary controlling gradient act to change the form of the transition. We investigated surficial geology as a possible controlling factor that would not be correlated with the primary climatic gradients found along transects across the alpine treeline. In at least some of the cases, surficial geology type was shown to be significantly associated with differences between sigmoidal and non‐sigmoidal transitions. These results support previous evidence for sigmoid wave transitions at the boreal forest—tundra ecotone, but also show that the alpine treeline case is more complex. We argue that in cases where ecotones are used as sites for monitoring the effects of climate change on vegetation, care should be taken to utilize only sites that exhibit a sigmoidal transition so as to minimize the effects of non‐climate‐related controlling factors on the interpretations.     

Mapping Lichen Diversity as a First Step for Air Quality Assessment

The evaluation of air quality is an important topic. It is well known that lichens have a set of characteristics that make them well suited for biomonitoring purposes. Sampling lichen diversity is not as expensive as chemical analysis, allowing a dense sampling grid and reducing the costs. Lichen diversity can be used to identify more disturbed areas, resulting from pollution, land use or ecological variables. In recent years, in order to enable extended use of lichens and to reduce ambiguities, i.e., variations due to unwanted environmental variables, efforts have been made to develop a feasible protocol for lichen sampling for biomonitoring purposes. This work aims at providing the information needed a priori for an air quality assessment study, in the form of a map showing areas where lichen diversity and abundance is lower. This study was done by sampling foliose and fruticulose lichen diversity and frequency, in a region in southwest Portugal (Sines) with large industrial facilities. A long-term study has been underway in the same area since the 1970s using lichens as bioindicators to evaluate air quality. In this work, we used a standard protocol to determine a lichen diversity value (LDV), to be used as an indicator of environmental quality. In order to reduce uncertainty concerning the type of disturbance affecting lichens, sampling sites were restricted using well-defined criteria. Whenever possible, sampling site variables were quantified. This method allowed us to reduce the many sources of variability affecting lichen diversity.     

Integrative Monitoring Analysis Aiming at the Detection of Spatial and Temporal Trends of Metal Accumulation in Mosses

Goal and Scope. The UNECE heavy metals in Mosses Surveys provide data on the accumulation of metals in naturally growing mosses throughout Europe. Using Germany as an example, this article concentrates on the elaboration and application of methods of data analysis that are necessary for a comprehensive interpretation of spatial and temporal trends in metal accumulation.Methods and Results. The sampling of mosses, and the chemical analysis of Cr, Cu, Fe, Ni, Pb, Ti, V and Zn in 1990, 1995 and 2000 are summarized briefly. The variogram analyses detect distinct autocorrelation structures in the sample data which may consequently be estimated for all sites in Germany without monitoring metal accumulation by means of ordinary kriging. A procedure for the geostatistical detection of spatial outliers was developed and applied and, after the elimination of the spatial outliers, several measurements were seen to indicate an adequate quality of the geostatistical estimations. The cluster analyses of the z-transformed estimation data result in a nominal multi-element index that indicates regional metal accumulation types over time. Percentile statistics serve for computation of an ordinal, scaled, multi-element accumulation index which is spatially differentiated over time in terms of multivariate, statistically defined ecoregions. The integrative statistical analysis reveals, from 1990 to 2000, that the metal accumulation declines up to 80% in some of the ecoregions. Hot spots of metal accumulation are mapped and interpreted by means of metadata analysis.Conclusions. Dot maps depict the spatial structure of the metal accumulation without spatial bias. This information, detailed with respect to metal species and space, should be generalized for better supporting the interpretation. The combination of geostatistical analysis and estimation, percentile and multivariate statistics is suitable for the calculation of indices that serve for a comprehensive mapping of metal accumulation in the ecoregions over time, for quantifying the bias of the surface estimation, and for mapping spatial outliers and hot spots of metal accumulation.     

Spatial Variability of Sampling: Grid Size Impact on Atmospheric Metals and Trace Elements Deposition Mapping with Mosses

This paper deals with the spatial heterogeneity structure and the influence of the precision of moss data on results interpretation as real spatial variations of atmospheric heavy metal deposition. Different sizes of map mesh net (unit I of 30 × 30 km, unit II of 10 × 10 km, unit III of 3 × 3 km) have divided an area of 90 × 90 km. The protocol used is a nested design with three levels and random draws. The statistical method of components of variance analysis estimates the associated variability for each mesh size. Our results show the poor precision of this biological tool for map purposes on a little scale (unit III). Furthermore, the high residual variance of As, Ba, Cd, Co, Cu, La, Ti, and U hides the spatial variations associated with mesh sizes. In order to obtain useful maps, it should be reasonable to use a 30 × 30 km mesh size, or even larger, to build spatial variation maps of Pb, Sb and with more caution for Cu, Sr, Rb and Zn. For V, As and Cd, the residual variability of moss data was too important to guarantee any spatial origin to the mapped variations. The cost–benefit study shows that the sampling effort has to be concentrated on unit I of 30 × 30 km to optimize future campaigns, and with a particular stress on the sampling repetitions for Cu, Pb, and Sb.     

Atmospheric Deposition of Trace Elements in Romania Studied by the Moss Biomonitoring Technique

The first systematic study in Romania of atmospheric pollution from heavy metals and other toxic elements based on moss analysis was undertaken as a Romanian–Russian–Norwegian collaboration, primarily in order to assess the general state of heavy metal pollution in Romania. An additional goal was to contribute to the European heavy metals in mosses survey, conducted under the auspices UNECE ICP Vegetation which reports to the Working Group of Effects of the Long-range Transboundary Air Pollution Convention. Samples of the moss species Hypnum cupressiforme, Hylocomium splendens and Brachytechium salebrosum and B. rutabulum were collected during the period 1995–2001. A total of 40 elements were determined using NAA and AAS. The total concentrations of arsenic, cadmium, copper, nickel, vanadium and zinc are presented in the form of contour maps. Generally, the observed concentrations in Romania are markedly higher than those observed in most other countries of Europe using the moss technique.