Showing papers on "Indicator species published in 1996"

Effects of Groundwater Decline on Riparian Vegetation of Semiarid Regions: The San Pedro, Arizona

Abstract: Groundwater depletion threatens many riparian ecosystems in arid and semi- arid regions of the world. The aquifer that sustains Arizona's San Pedro River riparian ecosystem, for example, is threatened by regional groundwater declines and localized pump- ing from the alluvial aquifer. This paper demonstrates the important role of shallow ground- water in structuring the San Pedro River plant community, portions of which function as reference areas that indicate site potential for a globally rare forest type (Sonoran riparian Populus-Salix forests). Several ecological indicators varied with depth to groundwater, including a weighted average wetland indicator score calculated for herbaceous and woody plant species, cover of plants within wetland indicator groups, and frequency of indicator plant species. These relationships can be used in a space-for-time substitution to predict consequences of groundwater decline. For example, the wetland indicator score changed sharply as depth to groundwater ranged from 0 to 4 m, and abundance of obligate wetland herbs (the group most sensitive to groundwater changes) declined sharply at groundwater depths below -0.25 m. Such sequential "desertification" of the riparian flora (i.e., loss or reduction in cover of species based on their probability of occurrence in wetlands) is one predicted response to groundwater decline. Other predicted impacts of groundwater decline include reduced establishment of Populus fremontii-Salix gooddingii forests, and reduced cover of herbaceous species associated with the fine-textured soils and shady conditions of floodplain terraces stabilized by these early seral tree species. High floodplain terraces (depth to groundwater of 5-8 m) had wetland indicator scores below those of upland sites and were vegetated by species (e.g., Prosopis velutina and Sporobolus wrightii) with low sensitivity to groundwater changes.

Dragonflies (Odonata) as Indicators of Biotope Quality in the Kruger National Park, South Africa

Abstract: 1. Monitoring programmes that assess ecosystem changes depend on indicator species or assemblages. Indicators should be sensitive and their response easily measured. This study assessed the suitability of adult male Odonata as indicators of biotope quality along the Sabie River in the Kruger National Park (KNP). 2. Odonate diversity was investigated at 25 sites along the Sabie River using univariate statistical procedures. The KNP supports 81 species, 59 recorded during this study (16 for the first time). 3. Sampling sites were classified by Two Way INdicator SPecies Analysis (TWINSPAN) and ordinated by DEtrended CORrespondence ANAlysis (DECORANA), based on the abundance of adult male Odonata. A predictive model relating Odonate species-groups to biotope variables, was formulated. 4. Classification led to the recognition of 10 ecologically meaningful biotope groups, each with an indicator species and a characteristic assemblage of associated species. 5. Multiple Discriminant Analysis (MDA) indicated that shade cover, permanency and flow rate could discriminate between biotope types defined by TWINSPAN. Variation in site membership between MDA and TWINSPAN suggests interaction between variables in determining species membership. 6. Biotope variables were incorporated into a model which predicted the membership of 82% of sites to the TWINSPAN groups; shade cover alone correctly predicted 44% of the sites. 7. The suitability of the Odonata as indicators of biotope quality, and its consequences for management are discussed.

How do indicator groups provide information about the relative biodiversity of different sets of areas?: on hotspots, complementarity and pattern-based approaches

Abstract: Regional conservation evaluation requires the effective use of available surrogate information, such as that provided by indicator taxa, for estimating the biodiversity represented by candidate protected areas. A recent study demonstrated that accumulating areas individually species-rich for one group of indicator organisms generally did not result in a set containing the areas that were species-rich for other groups. However, the requirement for a species- rich set, and not just individually-rich areas suggests an alternative assessment based on complementary- areas methods, which find a set of areas such that each of the indicator species is represented at least once. A set of areas covering all indicator taxa is assumed to be generally biodiverse. One limitation of this approach is that the set of areas species-rich for an indicator group is likely to represent many other organisms only if the members of the group span a wide range of habitats or environments. This supports the sampling of environmental pattern itself as an alternative strategy for selecting a set of biodiverse areas. Because such a pattern can be inferred from an indicator group, this same sampling strategy may extend the predictive value of such groups. Further, environmental pattern may incorporate additional useful information; for example, abundance information for the indicator taxa may improve predictions when used in this framework. These pattern strategies use the indicator group in a way that does not depend on the usual complementarity criterion in which a set is to be found that represents each indicator species. An example suggests that the complementary-areas approach may not be the best general strategy for using indicator groups in biodiversity assessment. We conclude that the current complementarity paradigm should be replaced by a more general pattern-based approach which views 'complementarity' not as a predictor, but as a general property to be predicted.

Effects of trace metals on infaunal species composition in polluted intertidal and subtidal marine sediments near a lead smelter, Spencer Gulf, South Australia

Abstract: The infauna of intertidal and subtidal marine sediments at 18 sites near a large lead-zinc smelter In Spencer Gulf, South Australia, was sampled twice about 6 mo apart. The sampled habltats were bare intertidal mudflats, intertidal seagrass [Zostera sp.) beds, subtidal seagrass (Posidonia spp.) beds, and unvegetated sedlments at 5 to 10 m depth. The Infauna consisted of 372 identifiable taxa, malnly polychaetes, molluscs and crustaceans. The number of taxa at each site and time showed no s~mple relationship with the concentrations of trace metals In sediments, habitat type or time of sampling. However, the patterns of distribution, analysed uslng frequencies of occurrence of taxa derlved from mult~variate classification and ordination techniques, were related to the sediment concentrations of As, Cu, Mn, Pb, Sb and Zn. The extremely high concentrations of these trace elements (probably mainly Pb and Zn) appeared to affect both the abundances and distribution of many infaunal species. The multivariate techniques could detect which species were affected in the most metal-polluted sites (the intertidal sites). However, in the less-polluted subtidal sites, patterns in species composition were detected but only a few individual species could be unambiguously correlated to the presence of the metals. The polluted intertidal sediments, which had some of the highest metal concentrations ever recorded in marine sediments (Pb up to 5270 pg g-' and Zn up to 16700 pg g-'), supported 42 taxa. The polychaetes Heteromastus filiformis, Capitella 'capitata' and Glycera americana, and the crustacean Tanais dulongii were very abundant in these sites; they apparently can selectively exploit the metalcontaminated conditions. C. 'capitata'and 7 dulongii were found almost exclusively in these sites. In contrast. 15 spccicb of polychaetes, 5 crustaceans and 4 molluscs found elsewhere in the study area. representing 26, 20, and 17"% of these intertidal taxa respectively, were not found in the metal-polluted sites. No tdxonomic select~vity in the effects of the metals was detected amongst the 3 major groupspolychaetes, molluscs dnd crustaceans. Future studies may, therefore, be able to sample indicator species from only one of these major groups to determine the spatial extent of ecological effects or to monitor metal effects in this area.

Use of Fish Communities to Assess Environmental Impacts in South Carolina Coastal Plain Streams

Abstract: We developed an index of biotic integrity (IBI) and a biotic index based on fish species richness (FSBI) to assess the ecological health of streams on the Savannah River Site, a 780-km2 U.S. Department of Energy facility located in the Sand Hills ecoregion on the upper coastal plain of South Carolina. To maintain the responsiveness of the IBI to a variety of impacts yet incorporate sufficient ecoregion specificity to achieve acceptable accuracy, we included metrics from each of six metric categories proven useful in other ecoregions (species number, species composition, trophic composition, local indicator species, fish abundance, and fish condition) but selected specific metrics within each category based on their ability to discriminate between disturbed and undisturbed sites in the Sand Hills ecoregion. We also developed a procedure based on species–area curves to remove the potentially confounding effects of site-specific differences in sample unit size and sampling effort from species number...

An assessment of macroinvertebrate functional feeding groups as water quality indicators in the Buffalo River, eastern Cape Province, South Africa

Abstract: The aim of this paper was to investigate the potential for using functional feeding groups (FFGs) as indicators of water quality conditions in rivers, using the Buffalo River, South Africa, as a specific example. Multivariate classification and ordination techniques were used to investigate species and FFG distributions in relation to a number of physico-chemical variables at 16 sites from the headwaters to the estuary of the Buffalo River. Two-way indicator species analysis (TWINSPAN) of species composition ranked most of the sites sequentially down the river, irrespective of water quality conditions. Ordination of FFGs from a set of riffle samples collected in mid-late summer showed only weak relationships between FFG distribution and water quality changes, except where variables changed sequentially down the river (e.g. pH and temperature). Individual species responses to water quality gradients were examined for nine riffle-dwelling species representing diverse FFGs. Following correspondence analysis of a matrix of environmental variables and species frequencies, some species showed strong associations with defined ranges of some variables. In particular, Adenophlebia auriculata (Leptophlebiidae, Ephemeroptera) from the headwater sampling site, was associated with low pH and low temperature. Simulium damnosum occurred under conditions of high turbidity, while Afronurus harrisoni was found under high concentrations of potassium, ammonium and nitrite ions. We conclude that although there was a distinct headwaters fauna in the Buffalo River, and sequential downstream changes in species composition, most FFGs (apart from shredders) were represented down the whole length of the river. FFG classifications are therefore unlikely to provide useful indications of water quality conditions in the Buffalo River. Using a categorical approach to classifying water quality variables, and by applying correspondence analysis to the resulting matrix, we recognised nine species that could be used to define water quality. These indicator species can be used to define tolerance ranges of the fauna for water quality conditions in different parts of the Buffalo river.

A Macrophyte‐Based Rapid Biosurvey of Stream Water Quality: Restoration at the Watershed Scale

Abstract: The restoration of chemically degraded rivers, lakes, and estuaries with large watersheds and pollution sources that are primarily diffuse in nature requires the grading of thousands of kilometers of tributary streams. Many population-and community-oriented biomonitoring methods have been developed that avoid the cost limitations of chemical/biomarker/bioassay approaches and the serious limitations of single-factor analysis as related to complex systems. In this study of the coastal plain and piedmont geomorphologic provinces of the Chesapeake Bay watershed, we have demonstrated a set of quantitative measures based on analysis of macrophyte populations that provide statistically significant separation of streams in accordance with their state-issued water quality rating. Macrophytes can be abundant and diverse in lower-order streams, and they demonstrate patterns of community structure and diversity similar to those of other organisms developed for biomonitoring of stream degradation. Unlike organisms previously and extensively used in biomonitoring techniques, however, macrophytes are considerably easier to identify and quantify. In addition, macrophyte techniques provide a range of measures of increasing sensitivity from species numbers at a few sites, to the presence/absence and abundance of indicator species, and, finally, to a diversity analysis based on easily identified species at an extended number of sites. We suggest that the ease of utilization of this methodology will allow repeated surveys of all streams in large watersheds with the invertebrate, fish and diatom biomonitoring to biomarking and chemical bioassays and finally analytical chemistry, progressively applied to verify and then identify specific pollution sources (“hot spots”) in a more limited number of problem streams.

Environmental and Endocrine Control of Reproduction in Two Species of Polychaete: Potential Bio-Indicators for Global Climate Change

Abstract: An in vitro bioassay has been developed which shows that oogenesis in Harmothoe imbricata is controlled by a gonadotrophic hormone which promotes egg protein synthesis in developing oocytes. A similar endocrine control mechanism is found in Eulalia viridis and analysis of in vivo assays indicate that the hormone acts as a transducer between the environment and the gamete. The timing of gametogenesis is controlled by environmental cues in both species and may be affected by predicted global climate change. With the development of these sensitive hormone assays it is possible to test the impact of climate change on both species, providing a possible early warning system for global warming and potential bio-indicators of climate change. Harmothoe imbricata is likely to be the more sensitive indicator species.

A comprehensive analysis of the effects of offshore oil and gas exploration and production on the benthic communities of the Norwegian continental shelf

Abstract: Multivariate statistical analyses of data on environmental variables and benthic fauna from 14 oil and gas fields obtained from 24 surveys collected between 1985 and 1993 are presented. At all fields oil-based drilling mud was used. The purpose of this study was to investigate contamination gradients, assess effects on benthic fauna both spatially and temporally and to evaluate measures such as diversity indices, indicator species and multivariate analysls techniques in assessment of pollution. Results from analyses of baseline surveys of environmental variables and fauna were charactensed by a lack of distinct gradients in station placement, having a typical shot-gun pattern in PCA-, DCAand MDS-ordination analyses. Likewise there was no consistency in which environmental variables correlated with the fauna. Contamination was assessed using all the physical and chemical data in classification and PCA-ordination analyses Clear patterns were found using 4 categories, conveniently termed initial, moderate, severe and gross. The categories were usually apparent as rings radiating from the platform. Initial contamination of the outermost areas at most fields was shown as elevated levels of barium and total hydrocarbons (THC) and sometimes also by elevated levels of zinc, copper, cadmium and lead. Three fields were studied in particular and showed contaminated areas of over 100 km2 (Valhall), over 15 km2 (Gyda) and over 10 km2 (Veslefrikk). After a period of 6 to 9 yr contamination had spread, so that nearly all of the outermost stations 2 to 6 km away from the platforms showed evidence of contamination. Thus, the existing sampling design is no longer suitable for assessment of the area contaminated. Effects on the fauna showed, as with contamination, 4 categories. Analyses hnking fauna and environmental variables indicated that the effects were mainly related to THC, barium and strontium, but also to metals like zinc, copper, cadmium and lead, which are all discharged in drill-cuttings. Effects on the fauna closely followed the patterns of contamination with only a few stations at each field that were contaminated not showing effects. Thus the areas showing effects were only slightly less than the areas contaminated. Subsequent to cessation of discharges biodegradation of oil and reduced concentrations of THC were observed. Yet there was an extension of areas where the fauna was affected several years after cessation of dnll-cutting discharges This may indicate that barite and related compounds associated with the discharges also have an environmental impact. However, preliminary results from fields using only water-based mud clearly indicate a reduction in environmental contamination and biological Impact, compared to effects reported here, for oil-based drill-cuttings. Diversity indices appl~ed to the data did not show the extent of effects and such Indices alone should not be used to interpret changes. The consistent patterns that the multlvariate techniques were able to detect showed that these methods were far superior. Analyses of the initial effects on the fauna showed that there were no consistent patterns in changes in species composition over fields or time, and thus the search for 'universal' sensitive indicator species does not seem to be rewarding. Yet under gross effects of pollution there were consistent patterns with the same species dominating. Finally, the initial effects of pollution included severe reductions in organisms that are key components of the benthic communities and also food for bottom-living fish, and are thus ecologically important. The new fauna which establishes in the contanunated sedirnents close to platforms, often with high abundance, will probably be less valuable as a food source for fish populations since it is of small size and lives sub-surface.

Inventory and Floristics of Sandhills Fens in Cherry County, Nebraska

Abstract: The Sandhills of north-central Nebraska and south-central South Dakota are the largest sand-dune area in the Western Hemisphere. In 1991 and 1992, an inventory of Sandhills fens in Cherry County, Nebraska, documented 39 fens ranging in size from 4 to 280 ha. The majority of these sites had been ditched and were used as hay meadows. In 1996, a detailed floristic survey of six fens in Cherry County ~ocum~nted 191 species and one subspecies of vascular plants, mcludmg 21 species considered rare in Nebraska. Fifteen Sandhills fen indicator species were identified. The Sandhills populations of the indicator species are disjunct from their primary ranges to the north and east of the Great Plains suggesting these populations to be glacial relicts. '

Spiders as indicator species :lessons from two case studies

Abstract: Spiders as indicator species : lessons from two case studies . Spiders have been used as indicator species in at least two ways . The first approach examines spiders at the species lever, using known ecological preferences in order to determine how spider communities react to environmental change or disturbance. In the second approach, species richness of spider communities is used as a synthetic indicator of the quality of natural habitats . An example for the first approach is the analysis of the tyrphobiont species of a series of European peat-bogs ; the second approach is illustrated by the analysis of a case study on the effect of reed bed burning and mowing on species richnesss and composition. Both case studies are discussed and the following lessons are drawn when individual species are used, excellent basic information on their distribution and ecology is a prerequisite for the choice of indicator taxa ; a high standard in sampling design is needed for indicator species applications ; precise definition of the kinds of perturbations that are expected to influence the indicator taxa is to be recommended .

Zooplankton Community and Distributions of Copepods in Relation to Eutrophic Evaluation in Chinhae Bay

Abstract: Spatio-temporal variations in zooplankton community and ropepod indicator species were investigated along with the interaction between zooplankton distribution and environmental factors in Chinhae Bay. Zooplankton samples were monthly collected at 7 stations from February to September in 1993. A NORPAC net was vertically hauled from bottom to surface, At the same station, environmental factors such as temperature, salinity and COD (chemical oxygen demand) were measured at two different water layers, surface and bottom. In August and September, salinity declined below , while eutrophic parameters such as COD showed the higher concentrations than those in other months, with higher concentrations at inner bay stations. Salinities were, however, higher at bay mouth areas. These distributional patterns were believed to be caused by input and dispersion of organic matters from nearby land. Zooplankton communities were composed of . Of these, Noctiluca scintillans was predominant and occupied of total zooplankton abundance. Cladocera and Copepoda were secondly abundant taxa. Among 6 to 10 copepod species appeared, Acartia omorii and A. hudsonics were most common species during the survey months except March and September. Species diversities were greater, in general, at inner bay than outer bay. The lowest diversity index was observed in February, while the highest in July. Cluster analysis could divide the study area into 2 or 4 zones for each month. Zone 1, mouth area of the bay, was characterized by the influence of offshore waters. Zone II was mixing area. Zone III and IV seemed to be affected by nearby land.

Ciliates in rapid gravity filters of waterworks exploiting deep groundwaters.

Abstract: Potable water is increasingly produced from deep (>100 m) tertiary groundwaters which often are completely reduced and contain high amounts of ammonium, methane, and hydrogen sulphide. They thus require special treatment which includes oxygenation and removal of the reduced contaminants by the biofilm developing in rapid gravity filters. The biofilm is heavily colonized with ciliates and microinvertebrates. A total of 38 species of ciliates was found in 42 samples taken from 4 waterworks in Germany during a period of 2 years. Only six species occurred in high numbers and in more than half of the samples: Acineria uncinata, Aspidisca lynceus, Cinetochilum margaritaceum, Colpidium colpoda, Glaucoma scintillans, and Holosticha pullaster. Five to thirteen species occurred per sample, and up to 6,000 individuals ml−1 biofilm were counted. There was a considerable fluctuation in the number of species and individuals, which could not be related to specific process parameters. The number of species and individuals decreased markedly from the filter surface to its centre. Colonization of the filters very likely occurs randomly via impure surface waters. The ciliate communities found consist mainly of alphamesosaprobic to polysaprobic species and thus closely resemble those known from activated-sludge processes. This is explained by the specific conditions near and in the biofilm, which is probably microaerobic and highly productive, providing microaerobic bacterial feeders with copious food. Obviously, it is the microenvironment which determines the occurrence of certain species. Thus, future research on the autecology of the indicator species used in the saprobic system should concentrate on their microenvironments. © 1996 Wiley-Liss, Inc.