Changes In Environmental Characteristics Research Articles

Zooplankton composition and Status of Paniyala water Pond in Roorkee Uttarakhand

The influence of water quality of Paniyala fish pond on its zooplankton composition and abundance were investigated at four stations for one year between January 2008 and December 2009. Diversity was not high: five groups of zooplankton were found which include Protozoa, Rotifera, Cladocera, Copepoda and Ostracoda. Rotifera dominated numerically (65.75±40.60 Unit/L), followed by protozoa (57.71±37.69 Unit/L) and Cladocera (47.31±28.73 Unit/L). The zooplankton was more prevalent during winter season and there were variations in the composition and abundance along the reservoir continuum. Factors such as temperature, nutrients, food availability, shape and hydrodynamics of the reservoir, as well as reproductive strategies of the organisms, strongly influence the composition and population density of zooplankton. Seasonal trends in zooplankton community composition were also related to changes in environmental characteristics of the river. Our results indicate that the changing water quality status of the Paniyala water pond affected the zooplankton diversity and abundance and such measure could be used as a biomonitoring tool to determine the ecological health of the pond. Prevention of ecological deterioration of this water body would greatly result in a more productive water body, rich in zooplankton and with better fisheries.

Enrichment and shifts in macrobenthic assemblages in an offshore wind farm area in the Belgian part of the North Sea

The growing development of offshore wind energy installations across the North Sea is producing new hard anthropogenic structures in the natural soft sediments, causing changes to the surrounding macrobenthos. The extent of modification in permeable sediments around a gravity based wind turbine in the Belgian part of the North Sea was investigated in the period 2011 – 2012, along four gradients (south-west, north-east, south-east, north-west). Sediment grain size significantly reduced from 427 μm at 200 m to 312 ± 3 μm at 15 m from the foundation along the south-west and north-west gradients. The organic matter content increased from 0.4 ± 0.01% at 100 m to 2.5 ± 0.9% at 15 m from the foundation. The observed changes in environmental characteristics triggered an increase in the macrobenthic density from 1390 ± 129 ind m−2 at 200 m to 18 583 ± 6713 ind m−2 at 15 m together with an enhanced diversity from 10 ± 2 at 200 m to 30 ± 5 species per sample at 15 m. Shifts in species dominance were also detected with a greater dominance of the ecosystem-engineer Lanice conchilega (16–25%) close to the foundation. This study suggests a viable prediction of the effects offshore wind farms could create to the naturally occurring macrobenthos on a large-scale.

Distribution of periphytic algae in wetlands (Palm swamps, Cerrado), Brazil

The distribution of periphytic algae communities depends on various factors such as type of substrate, level of disturbance, nutrient availability and light. According to the prediction that impacts of anthropogenic activity provide changes in environmental characteristics, making impacted Palm swamps related to environmental changes such as deforestation and higher loads of nutrients via allochthonous, the hypothesis tested was: impacted Palm swamps have higher richness, density, biomass and biovolume of epiphytic algae. We evaluated the distribution and structure of epiphytic algae communities in 23 Palm swamps of Goiás State under different environmental impacts. The community structure attributes here analyzed were composition, richness, density, biomass and biovolume. This study revealed the importance of the environment on the distribution and structuration of algal communities, relating the higher values of richness, biomass and biovolume with impacted environments. Acidic waters and high concentration of silica were important factors in this study. Altogether 200 taxa were identified, and the zygnemaphycea was the group most representative in richness and biovolume, whereas the diatoms, in density of studied epiphyton. Impacted Palm swamps in agricultural area presented two indicator species, Gomphonema lagenula Kützing and Oedogonium sp, both related to mesotrophic to eutrophic conditions for total nitrogen concentrations of these environments.

From spring sources to springbrook: Changes in environmental characteristics and benthic fauna

Spatial patterns in macroinvertebrate communities and some abiotic factors were examined in three rheocrene springs and their springbrooks (Krakow-Czestochowa Upland, southern Poland). The mean discharge of particular springs ranged from 5 to 11 L s−1, and its annual fluctuations were small. Water temperature was very stable at all sampling sites. In the eucrenon the number of benthic taxa was the smallest (9–14 determined to the family level), but the densities were the highest (approx. 14000 ind. m−2). The biggest changes in macroinvertebrate composition were observed in the modified hypocrenon, which is an artificial pond. The lowest number of taxa were found in a natural, short springbrook with a nondiversified bottom substrate. The density of crenophilic taxa (Drusus trifidus, Dugesia gonocephala, Elmidae) diminished along the springbrooks, while the opposite trend was observed for ubiquitous taxa (some Oligochaeta, Asellus aquaticus and Chironomidae). Even in a very short natural springbrook (30 m), Drusus trifidus, the only species of Trichoptera found in the springs discussed here, goes through the entire development cycle. The strongest influence of a big river was observed at the outflow of one of the natural springbrooks, where the highest number of riverine oligochaete species were found. The benthic fauna of the springs studied here differed from that found in other springs in this area — the absence of the typical crenophilic species Bithynella austriaca (Gastropoda) and the presence of Gianus aquedulcis (Oligochaeta) may indicate the autonomy of the spring fauna in the Mstow area, possibly resulting from the postglacial geomorphological formation of this region or differences in habitat conditions.

Dinoflagellate cyst assemblages in recent sediments of Visakhapatnam harbour, east coast of India: Influence of environmental characteristics

The distribution and abundance of dinoflagellate cysts in recent sediments from Visakhapatnam harbour, east coast of India was investigated and compared with sediment characteristics and physico-chemical variables of the overlying water column. The cyst abundance varied from 11 to 1218cystsg–1dry sediment. Changes in the cyst assemblages from phototrophic to heterotrophic forms were observed from inner to outer harbour stations, and related to changes in environmental characteristics. Enhanced cyst production of potentially harmful dinoflagellate Protoceratium reticulatum was recorded in the inner harbour stations with higher nutrient concentrations. Protoperidinium cysts were the most diversified group, and were dominant in the outer harbour stations having improved water conditions and circulation. This study points out the potential use of dinoflagellate cyst populations in providing information on environmental conditions.

Habitat preferences of the encroacher shrub, Seriphium plumosum

The ecology of Seriphium plumosum is not yet fully understood and therefore requires in-depth research to assist with the control of this encroacher plant. The habitat preferences of the plant were quantified for terrain morphological units in terms of soil fertility, saline/sodic conditions and soil–water relationships. The influence of S. plumosum density on grass production was also quantified. It is clear that the distribution (both occurrence and density) of S. plumosum is associated with soil characteristics. The study indicated the sensitivity of S. plumosum towards wet conditions, perennial and transient water tables, overly high soil pH, clay content, high soil fertility (organic matter and phosphate) and sodium chloride. The deeper the soil profile, the more favourable the habitat for S. plumosum, owing to a decrease in waterlogged conditions. The habitat prevalence of S. plumosum is possibly a reflection of not only climatologically wetness but also of topographic wetness. There was no clear general trend for the individual cations along the terrain units. A significant relationship was established between aboveground phytomass production loss of the grass sward and S. plumosum density. These results confirm the threat posted by S. plumosum in semiarid grassland areas, following changes in environmental characteristics.

Zooplankton Community Responses in a Perturbed Tropical Stream in the Niger Delta, Nigeria~!2009-07-22~!2009-10-22~!2010-04-09~!

The effect of abattoir wastes and other anthropogenic activities on the distribution and abundance of zooplank- ton and environmental variables were investigated in Orogodo River, southern Nigeria. Samples of zooplankton were col- lected for a period of six months from three stations, representing upstream of the river course, effluent discharge point and downstream of the river course. A combined total of 79 species of zooplankton were encountered in the study. Station 1 recorded the highest number (78 species), station 2 with 22 taxa and station 3 with 72 representative taxa, showing re- covery in terms of diversity and abundance of zooplankton. Rotifers of the order Bdelloidea dominated all the stations and were relatively high in station 2 indicating their tolerance to a wide range of impact. Generally, the cladocerans were abundant at all stations. However, Moina micrura, and Thermocylops neglectus were the only members of this group re- corded in station 2. The low fauna diversity experienced in station 2 throughout the period of sampling showed strong evidence of impact arising from the abattoir waste discharge and heavy human activities at that station. Local environ- mental conditions (i.e. Temperature, flow velocity, depth, dissolved oxygen, alkalinity and conductivity) accounted for 69% of variation in zooplankton assemblages using canonical correspondence analysis (CCA). Seasonal trends in zooplankton community composition were also related to changes in environmental characteristics of the river. Our re- sults indicate that the changing water quality status of the Orogodo River affected the zooplankton diversity and abun- dance and such measure could be used as a biomonitoring tool to determine the ecological health of the river.

Short-term variability in primary productivity during a wind-driven diatom bloom in the Gulf of Eilat (Aqaba)

In the northern Gulf of Eilat (Aqaba), sharp increases in the biomass of diatoms and rates of primary production occurred in April 2008. Within 24 h, diatom abundance rose from 8 × 10 3 to 228 × 10 3 cells l -1 , and photosynthetic rates concomitantly doubled from 15 to 35 µg C l -1 d -1 . Water transparency declined, as indicated by the vertical diffusion attenuation coefficient Kd for photosyn- thetically active radiation (PAR), which increased from 0.076 to 0.090 m -1 and decreased the euphotic depth from 60 to 45 m. During this time, a significant increase in silica deposition by the diatoms was also detected. We attribute the mentioned changes in environmental characteristics to wind-gener- ated surface currents. Strong winds (up to 10 m s -1 ) during the measurements enriched the surface layers with unusually high nutrient concentrations within <1 d. Hence, primary production rates were observed at a relatively eutrophic nearshore station (MP) and pelagic station (A1, 10 km towards the center of the Gulf). They were compared with rates measured on the subsequent day. Values mea- sured were twice as high as those at the pelagic station during the previous calm day. Routine moni- toring programs with monthly or semi-weekly sampling are thus likely to miss brief but significant injections of nutrients, leading to the underestimation of seasonal and annual primary production. Our results demonstrate the impacts of transient events on the function and annual yield of aquatic ecosystems.

Phytoplankton Community Responses in A Perturbed Tropical Stream in the Niger Delta

The effect of abattoir wastes and other anthropogenic activities on the distribution and abundance of phytoplankton and environmental variables were investigated in River Orogodo, southern Nigeria. Samples of phytoplankton were collected monthly from three stations designated as station 1 (upstream of the river course), station 2 (effluent discharge point) and station 3 (downstream of the river course) for a period of six months. A combined total of 46 species of phytoplankton were encountered in the study. Station 1 recorded a total of 45 species, station 2 with 18 taxa and station 3 with 42 representative species, showing recovery in terms of diversity and density of phytoplankton. The order of dominance in the river was Bacillariophyceae > Chlorophyceae >Cyanophyceae > Euglenophyceae. The blue-green algae (Cyanophyceae) were dominant in station 2 in terms of density and diversity indicating their tolerance to organic enrichment. Generally, Spirogyra, Ulothrix, Oscillatoria, and Navicula species were the preponderant species. Euglena viridis was the only member of the class Euglenophyceae recorded in the river and it occurred only sporadically in station 1. The low fauna diversity experienced in station 2 throughout the period of sampling showed strong evidence of impact arising from the abattoir waste discharge and heavy human activities at that station. Pearson correlation coefficient analysis indicated temporal trends in phytoplankton density and composition. This was related to changes in environmental characteristics of the river. Keywords: Phytoplankton, Spirogyra, Ulothrix, River Orogodo, Abattoir wastes, Environmental variables.Tropical Freshwater Biology Vol. 17 (1) 2008: pp. 37-52

Macrobenthic recovery from hypoxia in an estuarine tidal mudflat

Macrobenthic recolonisation patterns after complete defaunation resulting from exper- imentally induced hypoxia were investigated in a polyhaline, estuarine mudflat. Based on simultane- ous sampling of biotic and environmental variables in replicated 16 m 2 control and defaunated plots, with a high resolution in time during 6 mo, the ecological interactions related to the macrobenthos reassembly were elucidated. Colonisation was predominantly determined by juvenile recruitment, and 3 successional stages were identified, each characterised by different species assemblages and environmental characteristics. During recovery, a shift in functional group dominance from mobile surface deposit feeders to tube-dwelling surface deposit feeders to biodestabilising taxa occurred, while their proportional dominance remained quite stable in the control plots throughout the experi- ment. Species colonisation patterns of later colonists revealed positive interactions with early colonis- ing opportunistic tube-building polychaetes Pygospio elegans, while later successional species (Het- eromastus filiformis, Macoma balthica) adversely affected the stable, favourable conditions created by the tube-building infauna. Transitions between different successional stages were related to recruitment of species, changes in environmental characteristics (oxygenation state of the sediment), direct and indirect ecological interactions (bio(de)stabilisation, exploitation competition for food). In general, our study suggests that macrobenthic reassembly after hypoxia is related to different types of interactions, all acting in a unique manner. Hence, macrobenthic successional dynamics in a tidal mudflat habitat should be considered as a dynamic process, related to resource availability, natural temporal variation, life history traits (e.g. opportunistic behaviour) and bio-engineering capacities of the colonising species.

Response of macroinvertebrate communities to abattoir wastes and other anthropogenic activities in a municipal stream in the Niger Delta, Nigeria

Impacts of co-occurring stressors (organic wastes and various human activities) on macroinvertebrate assemblages and environmental variables were investigated in a municipal stream, River Orogodo in southern Nigeria between the months of June 2004 and July 2005. Four sampling sites, each 25 m long were selected along 15 km stretch of the stream. There was a marked difference in the taxonomic composition of macroinvertebrates in the reference sites (I and IV) and those of the perturbed sites (II and III). A combined total of 78 benthic macroinvertebrate taxa were collected from the four sites of the river. The abundance and community structure patterns showed strong evidence of impact arising from the abattoir waste discharge such that the comparison of abundance values demonstrated high significance between the reference sites and the perturbed sites. Pearson correlation coefficient analysis indicated temporal trends in macroinvertebrate density and community composition. This was related to changes in environmental characteristics of the river especially BOD5 and amount of nutrients. These factors produced spatial and temporal heterogeneity and exerted major influence on the benthic communities. The preponderance of Oligochaetes and diptera and deterioration in water quality at sites II and III are attributed to the intensity of human activities at these sites. Shannon-wiener diversity and evenness were significantly higher (P < 0.05) at the reference sites I and IV. Results illustrate the need for careful consideration of the water quality and indicator organisms in restoration and remediation programmes.

Rise of oceanographic barriers in continuous populations of a cetacean: the genetic structure of harbour porpoises in Old World waters

BackgroundUnderstanding the role of seascape in shaping genetic and demographic population structure is highly challenging for marine pelagic species such as cetaceans for which there is generally little evidence of what could effectively restrict their dispersal. In the present work, we applied a combination of recent individual-based landscape genetic approaches to investigate the population genetic structure of a highly mobile extensive range cetacean, the harbour porpoise in the eastern North Atlantic, with regards to oceanographic characteristics that could constrain its dispersal.ResultsAnalyses of 10 microsatellite loci for 752 individuals revealed that most of the sampled range in the eastern North Atlantic behaves as a 'continuous' population that widely extends over thousands of kilometres with significant isolation by distance (IBD). However, strong barriers to gene flow were detected in the south-eastern part of the range. These barriers coincided with profound changes in environmental characteristics and isolated, on a relatively small scale, porpoises from Iberian waters and on a larger scale porpoises from the Black Sea.ConclusionThe presence of these barriers to gene flow that coincide with profound changes in oceanographic features, together with the spatial variation in IBD strength, provide for the first time strong evidence that physical processes have a major impact on the demographic and genetic structure of a cetacean. This genetic pattern further suggests habitat-related fragmentation of the porpoise range that is likely to intensify with predicted surface ocean warming.

Composición y estructura de la ictiofauna del Río Ceballos-Saldán (Córdoba, Argentina)

Los ríos presentan un gradiente longitudinal desde su naciente hasta su desembocadura, con los consiguientes cambios en sus características ambientales y en la composición específica. El objetivo de este trabajo fue describir esa variación longitudinal en las características de la fauna de peces del Río Ceballos-Saldán. Los muestreos se realizaron en cinco puntos, ubicados antes y después de las ciudades más importantes, durante un año. Los ensambles de peces fueron descriptos a través de la composición específica, abundancia, riqueza, diversidad y dominancia, atributos que fueron estimados para cada localidad de muestreo. Se aplicaron diferentes modelos especie/abundancia a cada ensamble de peces a lo largo del curso. Se capturaron 1.914 individuos pertenecientes a 17 especies. Once corresponden a primeras citas para este río. El orden más representativo fue el de los Siluriformes y la especie más abundante fue Hypostomus cordovae (Günther, 1880). La abundancia total fue el único atributo que varió significativamente a lo largo del curso, siendo menor antes de la ciudad de Río Ceballos. Los ensambles de peces fueron significativamente descriptos por tres modelos diferentes de abundancia poblacional, a lo largo del río.

Distribution of macroinvertebrate assemblages in the Azul‐Quemquemtreu river basin, Patagonia, Argentina

Longitudinal and seasonal changes in physical and chemical variables, and macro‐invertebrate community structure‐function were examined in the Azul‐Quemquemtreu river system in the subantarctic forest of Patagonia, Argentina. Patagonian mountain streams have a marked seasonal discharge pattern and may have high suspended sediment loads because of forestry and other land‐use practices. The main physical differences among sites were in substrate size (boulder‐pebble/ sand), mean width (3–37 m), discharge (<1–80 m3 s–1), total alkalinity (275–1210 meq litre–1) and conductivity (31–137 #GMS cm–1). Species richness and Ephemeroptera, Plecoptera, and Trichoptera richness decreased from upstream sites to the mouth of the river system and were affected by land use. Macroinvertebrate assemblages were influenced by physical (substrate size, width, discharge, current velocity) and chemical (alkalinity and conductivity) variables, and mean density of macroinvertebrates was significantly higher at the Quemquemtreu sites than the Azul sites. Canonical Correspondence Analysis indicated that seasonal trends in macroinvertebrate community composition were related to changes in environmental characteristics of the river, especially water temperature and discharge. The composition of benthic communities in rivers of the Patagonian Andes largely reflect characteristics related to stream size, but factors at the reach scale best explain variation in abundance data. Collector‐gatherers were the dominant functional feeding group at all sites. Faunas have similarities with those of New Zealand in taxonomic‐functional composition, with a predominance of Chironomidae (Diptera), Leptophlebiidae (Ephemeroptera), and Gripopterygidae (Plecoptera).

Structure of the invertebrate fauna in salt marshes of the Wadden Sea coast of Schleswig-Holstein influenced by sheep-grazing

Results of investigations on the influence of five different sheep grazing intensities on the invertebrate fauna of two mainland salt marsh sites of the German Wadden Sea coast are presented for the years 1990 and 1991. The investigation of the invertebrate fauna has been carried out since 1989 in thePuccinellia maritima zone, and theFestuca-Puccinellia as well as theFestuca-Armeria zones, with trapping transects arranged along an inundation gradient. Apart from specific biotic effects, grazing causes changes in environmental characteristics. Effects on microclimate comprise higher ranges of variance in soil-surface temperature on grazed sites. Decreasing food resources caused by grazing bring disadvantages to herbivores, the major part of the invertebrate fauna, due to merotope destruction (e. g. inflorescences ofAster tripolium) and the decline of host plant stands (e. g.A. tripolium, Plantago ssp.). Flower visitors and pollen feeding species that depend onA. tripolium have become extinct. Increasing food resources, caused by grazing, lead to higher population densities of a few specialized grass-feeding and surface-grazing invertebrates (e. g.Mayetiola ssp.,Psammotettix putoni, Bledius tricornis). Soil characteristics in the lower salt marsh have not been altered significantly by grazing; hence, the direct effect of grazing and trampling leads to a decrease in population density of many species such asAssiminea grayana, Orchestia gammarellus and collembolans. The biomass and abundance of detritivores and many herbivores increased from 1990 to 1991 on the totally grazed fields, whereas predators diminished in numbers at the same time. A descriptive model is presented, involving grazing, winter temperature, and precipitation as basic factors.

Automatic Data Correction System for TV Camera Measurement of Linear Sizes

The paper presents a digital system for correction of data from the measurement of linear sizes of moving objects - trunks, planks, etc. by TV cameras. The measurement is implemented by counting the impulses from a pulse generator in a sector, proportional in time to the measured linear size. The frequency of the generator is controlled and corrected through comparision of data received during the measurement of a model size. An algorythm is produced for the work of the system in mode "measurement" and in mode "correction". The system ensures the data correctness notwithstanding the remoteness of the object from the camera focuses as well as with disfocusingdue to changes in environmental characteristics.

Fatores ocupacionais associados à dor muscoloesquelética em professores

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