Dominance Of Tolerant Species Research Articles

Ecological Status of a Tropical Inland Water Using Macroinvertebrate Feeding Groups and Sediment Characteristics

Changing environmental conditions have an important influence on the functional and structural organization of macroinvertebrates in water. The involvements of macroinvertebrates in Bio-monitoring have focused largely on their distribution pattern in water while neglecting the functional and feeding structure. This study aims to use the structure and habitat preferences of macroinvertebrates to provide reliable information on the ecological integrity of Atori Reservoir. Macroinvertebrates were sampled once every two months from selected sample stations in Atori Reservoir for a period covering both wet and dry seasons of an annual cycle. The collected macroinvertebrates were categorized into functional groups using feeding patterns, habitat preferences and mode of locomotion. The reservoir sediment was also analyzed for selected physico-chemical characteristics. Predators (feeding pattern) and Skaters (locomotion and habitat preference) were dominant in the collection. Many of the functional feeding groups were more abundant in the dry season. In fact, Collector-gatherers and shredders were recorded only in the dry season. There was no significant difference in the seasonal variation in the distribution of the macroinvertebrates in the reservoir. The physico-chemical parameters of the sediment did not vary significantly across the sample stations but paired samples T-test showed significant differences in the seasonal variations of physico-chemical parameters of the sediment in the reservoir The dominance of predators and skaters, which are known tolerant species have implications for the ecological integrity of the water. The dominance of tolerant species and the physico-chemical characteristics of the sediment suggested the presence of mild pollution in Atori Reservoir. Proactive conservative measures should be taken in order to prevent further degradation of the water quality as well as prevention of loss of biodiversity in the waterbody.

Anthropogenic impact on environmental variables and macroinvertebrates community of River Eme, South-East, Nigeria

Macroinvertebrates are good bioindicators of water quality and ecosystem health and are often used to study anthropogenic effect on aquatic ecosystems. Consequently, some environmental variables and macroinvertebrates of Eme river were studied to understand the impact of human activities on this socio-economically important ecosystem. Six stations (reflecting different anthropogenic activities) along the reaches of the river were sampled and analyzed monthly from December, 2017 to November, 2018 using standard methods. The results showed that water temperature varied from 22.00, station 1 to 28.5oC, station 6, turbidity (0.50-9.40 NTU, station 4), flow velocity (0.21, station 1-0.85m/s, station 3), pH (4.30, station 2-6.30, station 1), electrical conductivity (45.20, station 2-168.40µS/cm, station 5), dissolved oxygen (1.60, station 4-6.10mg/l, stations 3 and 4), biochemical oxygen demand (0.80-4.30mg/l, station 4), nitrate (1.10, station 3-5.6mg/l, station 4) and phosphate (0.40, station 3-4.6mg/l, station 4). Flow velocity, electrical conductivity, biochemical oxygen demand, nitrate and phosphate varied significantly between stations (p<0.05). A total of 584 individuals from 5 taxonomic groups and 23 species of macroinvertebrates were recorded. Aquarius remigis was the most abundant species (8.7%). The macroinvertebrate community was dominated by tolerant and very tolerant species, such as Aquarius remigis, Caridina africana, Pseudocloen sp. nymph, Hydrometra sp and Belostoma sp. The dominance of tolerant species, high turbidity, biochemical oxygen demand, nitrate and phosphate values and low dissolved oxygen values are strong indications of anthropogenic effect. It is suggested that adequate management attention should be paid to the river in order to prevent further deterioration.

Foraminiferal ecozones in two submarine caves of the Orosei Gulf (Sardinia, Italy)

Because submarine caves are affected by wide spatial and temporal environmental variability, they are ideal environments for studying the effects of environmental changes on ecological indicators. Benthic foraminifera are protozoa living in marine and transitional habitats, developing typical assemblages as a response to different environmental conditions. For this, they have been increasingly used as ecological indicators for environmental characterization and monitoring. This study was the first one aimed to compare benthic foraminiferal fauna of two different submarine caves of temperate areas, Bel Torrente and Bue Marino, in the Orosei Gulf (Sardinia, Italy). It resumes the main results obtained in Bel Torrente cave by a previous research, implemented by new data acquired by the study of Bue Marino cave. The caves were surveyed and sampled by GUE (Global Underwater Explorers) divers for the first 450 m to recognize distinct ecozones, their ecological significance, and to compare them as regards species composition and extent. The succession of Marine, Entrance and Transitional Ecozones was recognized in both the caves. While the Marine Ecozone pointed out environmental conditions very similar to those of shallow water marine environment, the Entrance and Transitional Ecozones indicated increasing environmental stress. In the Entrance Ecozone, the dominance of tolerant species was probably due to the high environmental variability for the episodic high energy floods and, locally, reduced oxygenation events. In the Transitional Ecozone, the decrease of seawater salinity and temperature, especially after rainy periods, probably encouraged the prevalence of agglutinated taxa, which are normally rare in Mediterranean shallow water marine environment, while they are common in high latitude basins.

Nutrient regime, N:P ratios and suspended solids as key factors influencing fish tolerance, trophic compositions, and stream ecosystem health

The objectives of this study were to determine the effects of stream nutrient regime, N:P ratios and suspended solids on fish tolerance/trophic compositions and stream ecosystem health, based on multi-metric model, during 2008–2013. Also, stream ecosystem health was evaluated in relation to chlorophyll-a (CHL) as a measure of algal productivity or indicators of trophic state to water chemical parameters. Total number of sampled fish species were 50 and showed a decreasing trend from 2008 to 2013. The minnow of Zacco platypus, based on the catch per unit effort (CPUE), was the most dominant species (25.9%) among the all species. Spatial heterogeneity was evident in the fish tolerance guilds that showed the dominance of sensitive species (89%) in the headwaters (S1) and the dominance of tolerant species (57%) in the urban. These conditions were directly influenced by concentrations of nutrients and organic matter (COD). The N:P ratios, as a barometer of water pollution, had a negative linear function (R 2 = 0.40, P 0.05) to the two compositions, but phosphorus influenced directly the two guilds [slope (a) = -32.3, R 2 = 0.25, P < 0.01 in the In; a = 40.7, R 2 = 0.19, P < 0.01 in the Om]. Such water chemistry and fish trophic guilds determined the stream ecosystem health, based on the multi-metric fish model.

Macrophytes, epipelic biofilm, and invertebrates as biotic indicators of physical habitat degradation of lowland streams (Argentina)

Our objective was to assess the effect of the physical habitat degradation in three lowland streams of Argentina that are subject to different land uses. To address this matter, we looked into some physical habitat alterations, mainly the water quality and channel changes, the impact on macrophytes' community, and the structural and functional descriptors of the epipelic biofilm and invertebrate assemblages. As a consequence of physical and chemical perturbations, we differentiated sampling sites with different degradation levels. The low degraded sites were affected mainly for the suburban land use, the moderately degraded sites for the rural land use, and the highly degraded sites for the urban land use. The data shows that the biotic descriptors that best reflected the environmental degradation were vegetation cover and macrophytes richness, the dominance of tolerant species (epipelic biofilm and invertebrates), algal biomass, O2 consumption by the epipelic biofilm, and invertebrates' richness and diversity. Furthermore, the results obtained highlight the importance of the macrophytes in the lowland streams, where there is a poor diversification of abiotic substrates and where the macrophytes not only provide shelter but also a food source for invertebrates and other trophic levels such as fish. We also noted that both in benthic communities, invertebrates and epipelic biofilm supplied different information: the habitat's physical structure provided by the macrophytes influenced mainly the invertebrate descriptors; meanwhile, the water quality mainly influenced most of the epipelic biofilm descriptors.

From forests to cattail: how does the riparian zone influence stream fish?

The aim of this study was to verify whether taxonomic and functional composition of stream fishes vary under three different preservation conditions of riparian zone: preserved (PRE), intermediate condition (INT), and degraded (DEG). Five stream stretches representing each condition were selected. Samples were taken from each stream in three occasions during the dry seasons from 2004 to 2007. Electro fishing (PRE and INT), sieves, dip nets, and hand seines (DEG) were used according to the characteristics of each sampled site. Overall, 46 species were registered. Differences in the taxonomic and functional species composition among groups were found, following the condition of riparian zones. The ichthyofauna recorded in the PRE was typical to pristine environments, consisting of species with specialized habits, notably benthic insectivores, intolerant, and rheophilics. In the INT group, replacement of riparian forest with shrubs and/or grasses created environmental conditions which favor the occurrence of tolerant species but also harbor a residual fauna of sensitive species. DEG streams presented mostly detritivores, tolerant, small sized fishes which occupy the surface and preferred slow water flux. Changes in the species composition were represented by the occurrence and dominance of tolerant species in detriment of the more sensitive and specialist species, following the gradient of degradation in the riparian zone. Forested streams act as unique habitats to many specialized species and it can be presumable that the degradation of riparian vegetation can generate biotic homogenization which may reduce species diversity and ecosystem services.