Level Of Environmental Disturbance Research Articles

Assessing the resilience of hermit crabs to extrinsic and intrinsic environmental change

The resilience of communities to environmental change depends on the interplay between extrinsic and intrinsic factors that may have contrasting outcomes for constituent species. We investigated the resilience of two co-occurring species of hermit crab (Clibanarius spp.) to different levels of environmental disturbance (i.e., burial depth and sediment type as extrinsic factors) and resource quality (i.e., shell encrustation and adequacy as intrinsic factors), which may interact to affect survival outcomes in intertidal environments. Results showed that for both species, the ability to emerge from mud was dramatically less than sand, suggesting that human activities which increase the deposition of fine sediments may be detrimental for entire populations. Secondly, deeper burial events had a negative effect on emergence, although this was more profound for C. antillensis than the more abundant species C. vittatus. To explore the interplay between extrinsic factors and intrinsic characteristics, we expanded our comparisons to include shell quality (clean vs. encrusted gastropod shells) and a continuous variable describing shell adequacy (i.e., shell fit for a given size of crab). This analysis was done using Generalized Linear Mixed Models (GLMM's), with results indicating that the factors governing the emergence of C. antillensis were mostly extrinsic, while those for C. vittatus were more complex and modulated by aspects of shell quality. Overall, our models highlight the interplay between extrinsic and intrinsic factors in response to environmental variability which may affect species in unpredictable ways that can undermine the resilience of entire communities.

Linking chemical and physical parameters of a coastal water ecosystem with macrobenthic assemblages to assess environmental disturbance

Environmental disturbance, whether natural or anthropogenic, may change the structure of macrobenthic assemblages (across various spatial and temporal scales) in terms of taxa richness, animal abundance, and animal biomass. Such changes may be used as an indicator and can provide a quantitative basis when assessing the levels of disturbance. This study is aimed to assess environmental disturbance caused by fish farming by linking chemical and physical parameters to differences in the structure of macrobenthic communities. The study sites comprised coastal water ecosystems in the Awerange Gulf, South Sulawesi, Indonesia. The study compared macrobenthic communities associated with polyculture and monoculture farming against reference sites. The tendency of reduction in their abundance occurred at polyculture and monoculture sites, compared to the reference site, i.e. 5882 ind.m-2, 3531 ind.m-2, 2112.5 ind.m-2, respectively. The results from multivariate and graphical methods using NMDS plots, k-dominance curve, and ABC curves, tend to be in accordance with the results from index values, thus both methods may be used as a apart of rapid assessment of level of environmental disturbance in coastal water ecosystem. Carbon and nitrogen contents in sediment and dissolved oxygen (DO) were the most chemical and physical parameters influencing structure of macrobenthos (r=0.457; BIO-ENV).

Assessment of disturbance at three spatial scales in two large tropical reservoirs.

Large reservoirs are an increasingly common feature across tropical landscapes because of their importance for water supply, flood control and hydropower, but their ecological conditions are infrequently evaluated. Our objective was to assess the range of disturbances for two large tropical reservoirs and their influences on benthic macroinvertebrates. We tested three hypotheses: i) a wide variation in the level of environmental disturbance can be observed among sites in the reservoirs; ii) the two reservoirs would exhibit a different degree of disturbance level; and iii) the magnitude of disturbance would influence the structure and composition of benthic assemblages. For each reservoir, we assessed land use (macroscale), physical habitat structure (mesoscale), and water quality (microscale). We sampled 40 sites in the littoral zones of both Três Marias and São Simão Reservoirs (Minas Gerais, Brazil). At the macroscale, we measured cover percentages of land use categories in buffer areas at each site, where each buffer was a circular arc of 250 m. At the mesoscale, we assessed the presence of human disturbances in the riparian and drawdown zones at the local (site) scale. At the microscale, we assessed water quality at each macroinvertebrate sampling station using the Micro Disturbance Index (MDI). To evaluate anthropogenic disturbance of each site, we calculated an integrated disturbance index (IDI) from a buffer disturbance index (BDI) and a local disturbance index (LDI). For each site, we calculated richness and abundance of benthic macroinvertebrates, Chironomidae genera richness, abundance and percent Chironomidae individuals, abundance and percent EPT individuals, richness and percent EPT taxa, abundance and percent resistant individuals, and abundance and percent non-native individuals. We also evaluated the influence of disturbance on benthic macroinvertebrate assemblages at the entire-reservoir scale. The BDI, LDI and IDI had significantly greater average scores at São Simão than at Três Marias Reservoir. The significantly greater differences in IDI scores for São Simão Reservoir were reflected in 10 of the 13 Ekman-Birge dredge biotic metrics and in 5 of 13 of the kick-net biotic metrics. We also observed clear ranges of disturbances within both reservoirs at macro (BDI) and mesoscales (LDI) and in water quality, but an insignificant range in MDI results. However, we found no significant relationship between the benthic macroinvertebrate metrics and the BDI, LDI, and IDI among sites within a single reservoir. Hence, we believe that benthic macroinvertebrate distributions in those reservoirs were influenced by other factors or that reservoir macroinvertebrates (dominated by chironomids) were poor indicators of disturbance at the site scale.

Implementation of ARIMA Model to Asses Seasonal Variability Macrobenthic Assemblages

Human activities, including industrial and aquaculture, may have impact on water environment, especially organic enrichment. One of bioindicator of pollution that affect the quality of the water ecosystem is macrobenthic community. In general, the more diverse macrobenthic assemblages indicate the better of the waters quality. Understanding spatial and temporal distribution of macrobenthic abundance has become an important part of research in the field of ecology in understanding the level of environmental disturbance over time. This study discussed the application of the method of Autoregressive Integrated Moving Average (ARIMA) to asses seasonal variability ofmacrobentic assemblages. We found that forecasting using autoregressive integrated moving average method with the model of ARIMA (0,1,1) is obtained the smallest value of the Mean Square Deviation (MSD).

Land‐use impacts on small‐scale Mpologoma wetland fishery, eastern Uganda: A socio‐economic perspective

AbstractSmall‐scale fisheries in developing countries are characterized by uncertain futures attributable to ever‐increasing pressures on wetland resources. Data on the interconnectivity between wetland fishery, land‐use changes and the socio‐economic situation in the Mpologoma wetland, Uganda, were obtained through interviews and structured questionnaire surveys at sampling sites exhibiting differing different levels of environmental disturbance (ranging from less disturbed to highly disturbed). Rice production was the major economic activity at the highly disturbed sites, while maize production was the major activity at the less‐disturbed sites. Of the secondary activities, the Clarias gariepinus (Burchell, 1815) and Protopterus aethiopicus (Heckel, 1851) fishery was more important at the less‐disturbed sites. The high daily fish sale income ranging from US$ 8 to 12 and the high‐percentage (52%) catch preference of all large wetland fish species were observed for the less‐disturbed sites. A high percentage of respondents from the area of the less‐disturbed sites had higher annual incomes, resulting in more accumulated wealth than for the highly disturbed Nsango site, whose fishery was affected by large‐scale rice schemes. The overall socio‐economic impact of the small‐scale fishery, based on the data regarding the number of fishermen and their dependents, and the income from fish sales and other wetland activities, was low, with differences between sites being attributed to the level of wetland disturbance. The Mpologoma wetland is threatened by overexploitation of its fisheries services, but also overlooked and undervalued by policymakers because of inadequate fisheries statistics. Thus, the information derived from this study will facilitate the formulation and design of riverine wetland‐specific and small‐scale fisheries management strategies.

Response of Trophic Groups of Macrobenthos to Organically Enriched Sediments: A Comparative Study between Temperate and Tropical Regions

This study is aimed to detect the level of environmental disturbance caused by farming activities using trophic groups of macrobenthic assemblages, with emphasizes the difference between temperate and tropical regions. The samples of macrobenthic assemblages were taken from 2 (two) farm sites, i.e. Southern Spencer Gulf, South Australia, where farming of southern bluefin tuna ( Thunnus maccoyii ) takes place, representing as a temperate region (Site I) and milk fish ( Chanos chanos ) farms and mangrove area at coastal region of Mngkang Kulon, Semarang, Central Java, Indonesia, representing as a tropical region (Site II). Macrobenthic abundance was categorised based on six major trophic groups. Macrobenthic assemblages dominated by all polychaetes, they are Capitellidae, Cirratullidae, Lumbrineridae, Nephtyidae, and Spionidae at Site I (temperate region), owing to their relatively tolerance to organic enrichment, both at the farm sites and at control sites. Surface deposit feeders (SDF) dominated in abundance at both control and fish farm sites at Site I, whilst subsurface deposit feeders (SSDF) exhibited highest in proportion at Site II over the study period, in particular species of Capittelidae, indicating that both sites has been influenced by fish farm activities. The abundance of deposit feeders was significantly higher at the farm sites than at the reference sites. Organic carbon in the sediment surface is likely to correlate with deposit feeding and sub-surface deposit feeding species richness, whereas total and food particulate matter correlate with species diversity. The result of this comparative study implies that response of trophic groups of macrobenthos to environmental disturbance are considerably similar at both tropical and temperate regions.

High levels of spatial heterogeneity in the biodiversity of soil prokaryotes on Signy Island, Antarctica

In a previous study, soil bacterial diversity at environmentally distinct locations on Signy Island was examined using denaturing gradient gel electrophoresis (DGGE) profiling, and a range of chemical variables in soils was determined in order to describe variations between them. The dominant bacterial communities of all locations were found to be significantly different, although higher levels of similarity were observed between locations with similar physico-chemical characteristics, such as at penguin rookeries, seal wallows and vegetated soils. Extending this study, here soil prokaryote biodiversity was compared between 15 distinct locations in order to elucidate any interaction between four general habitat types on Signy Island (South Orkney Islands, maritime Antarctic) and any influence of previous human impacts at these sites. Specific sites were selected to represent the range of different soil environments present and to cover a range of environmental factors present in the maritime Antarctic which are known to influence bacterial community composition in soils elsewhere. A diverse prokaryote community is described, again with the majority of excised and sequenced bands belonging to the Bacteroidetes. Although DGGE profiling identified significant differences in prokaryotic biodiversity between all sampling sites, aggregations of banding patterns were also apparent across the different soil environments examined. Correlations between specific DGGE profiles and 10 selected soil parameters suggested that much of this variation could be explained by differences in the levels of environmental disturbance and soil pH. In particular, a greater proportion of variation in soil bacterial diversity was explained by differences in soil properties at human-disturbed locations than at undisturbed locations, with higher explanatory values by edaphic factors in the former and soil metal content in the later. In general, our data indicate that small-scale variation is an important factor in understanding patterns of prokaryotic distributions in soil habitats in the maritime Antarctic environment.

Ecological, anatomical and physiological traits of benthic macroinvertebrates: Their use on the health characterization of freshwater ecosystems

Ecological, anatomical, and physiological traits of benthic macroinvertebrates: their use on the health characterization of freshwater ecosystems After some studies made in Northern Portuguese freshwater ecosystems using the benthic macroinvertebrate communities for water quality evaluation, it has been possible to see that only the analysis of some characteristics allowed to distinguish different levels of environmental disturbance. The studies of some characteristics of the macroinvertebrates and the comparison with the results of the physico-chemical pa- rameters analysed show that the more disturbed the ecosystems had, the lower dissolved oxygen concentration and organisms with greater independence from this concentration. The objective of this work is to define groups of organisms, attending to some of their characteristics that are related to getting oxygen. The groups were defined through bibliographic information and from direct observation of their behaviour. The ability of these groups to distinguish different types of ecosystems was analysed by comparison of the obtained results on their distribution in a group of sampling sites located along gradients of contamination, with the results obtained by the calculation of biological indices, descriptive metric analyses of the community, and the water chemical quality. After this study, it is possible to say that the results obtained with the use of respiratory groups can be more informative than that obtained with the analysis of the physico-chemical parameters or other biological parameters.

AN APPROACH TO COMPILING ECOLOGICAL MAPS OF THE USSR

The authors analyze the relationship between aspects of land use, settlement, and production technologies, on the one hand, and estimates of the resistance of landscapes to human disturbance, on the other. This provides a basis for compiling maps depicting various levels of environmental disturbance. Examples of such maps (of environmental conditions within the USSR) compiled at the Institute of Geography at a scale of 1:8,000,000 are described. Translated by Larry Richardson, Glendale, CA 91202 from: Izvestiya Akademii Nauk SSSR, seriya geograficheskaya, 1990, No. 4, pp. 61-70.

High Altitude Photos for Inactive Mines

The utility of high altitude, 1:120,000-scale, color, infrared aerial photographs for inventorying inactive surface mines and assessing their environmental conditions was demonstrates for a 200 sq mile (500 km²) area in Pennsylvania. Some 60 surface mines that had been abandoned with little or no reclamation were detected using 1971, 1973, and 1975 photographs. Revegetation was the primary indicator. Through stereoscopic analysis of the photographs, each inactive mine was characterized by mining method, topographic features, erosion, mass wasting, revegetation, water quality, and visibility from roads or populous areas. Numerical values were assigned to these characteristics in order that a rating could be calculated for each mine. This rating reflected the mine’s overall level of environmental disturbance or potential environmental hazard.