Polluted Habitats Research Articles

Additional Selection for Insecticide Resistance in Urban Malaria Vectors: DDT Resistance in Anopheles arabiensis from Bobo-Dioulasso, Burkina Faso

In the city of Bobo-Dioulasso in Burkina Faso, Anopheles arabiensis has superseded Anopheles gambiae s.s. as the major malaria vector and the larvae are found in highly polluted habitats normally considered unsuitable for Anopheles mosquitoes. Here we show that An. gambiae s.l. adults emerging from a highly polluted site in the city centre (Dioulassoba) have a high prevalence of DDT resistance (percentage mortality after exposure to diagnostic dose = 65.8% in the dry season and 70.4% in the rainy season, respectively). An investigation into the mechanisms responsible found an unexpectedly high frequency of the 1014S kdr mutation (allele frequency = 0.4), which is found at very low frequencies in An. arabiensis in the surrounding rural areas, and an increase in transcript levels of several detoxification genes, notably from the glutathione transferase and cytochrome P450 gene families. A number of ABC transporter genes were also expressed at elevated levels in the DDT resistant An. arabiensis. Unplanned urbanisation provides numerous breeding grounds for mosquitoes. The finding that Anopheles mosquitoes adapted to these urban breeding sites have a high prevalence of insecticide resistance has important implications for our understanding of the selective forces responsible for the rapid spread of insecticide resistant populations of malaria vectors in Africa.

Soil Microarthropods in a Secondary Rainforest, Rivers State, Nigeria - IV- The Impact of Oil Pollution on Their Vertical Distribution

Studies were undertaken, May, 2007-April, 2009, to document species richness, bioindicator species, abun- dance, density, vertical distribution, etc. of soil microarthropods (mites, collembolans) in unpolluted and polluted habitats in a secondary rainforest, Rivers State, Nigeria. This paper focuses on the effects of oil pollution on the vertical distribution of these mesofauna. Sampling was effected monthly by a bucket-type auger to a depth of 15.0cm in four habitat-types (un- polluted, polluted by oil spills approximately 1yr, 3yrs and 6yrs pre-study). The modified Bukard model of the Ber- lese-Tullgren funnel was used for extraction. Identifications were undertaken using standard keys and unidentified speci- mens were compared to type specimens. In the unpolluted and polluted (3 and 6yrs pre-study) habitats, there was an inverse relationship between mite/ collembolan abundance/density (except in the Prostigmata) and soil depth; however, the correla- tions were not significant. In contrast, there was a significant direct correlation between mite abundance/density and depth in the habitat, polluted 1yr pre-study (F=29.11; df=1.3; p 0.05). In the unpolluted habitat, approximately 90% of all collembolans were found above a depth of 10.0cm; this declined to 30% in the habitat, polluted 1yr pre-study, and rose to 50% and 85% in the habitats, polluted 3 and 6yrs pre-study.

High tolerance to abiotic stressors and invasion success of the slow growing freshwater snail, Melanoides tuberculatus

Considerable research has been conducted to determine traits common to invasive species with the goal of predicting, preventing, or managing invasions. The importance of physiological tolerance to abiotic stressors in the ability of invasive species to establish and displace native species has been hypothesized to be important although there are few actual tests of the hypothesis in the literature. In freshwater molluscs it has been suggested that high fecundity is the most important trait for invasion success and that physiological tolerance to abiotic conditions is unlikely to play a significant role. We examined the tolerance to abiotic stressors using a known invasive snail species (Melanoides tuberculatus) that has a much slower growth rate and fecundity than a native species it has displaced (Biomphalaria glabrata). We tested the hypothesis that M. tuberculatus would have significantly greater tolerance to natural and anthropogenic abiotic stressors (cadmium, malathion, temperature extremes, and desiccation) which may provide a mechanism for displacement of B. glabrata. A time-to-event analysis was used to determine relative tolerance between species. M. tuberculatus was significantly more tolerant to the tested abiotic stressors than B. glabrata with the exception of low temperature (5°C). Stress tolerance may partly explain the ability of M. tuberculatus to displace B. glabrata despite having a much lower growth rate and fecundity. These results also suggest that M. tuberculatus is likely to have a strong advantage in disturbed or polluted habitats. Identifying those traits most important for the invasion success of particular species could be used to better inform removal strategies and may allow for improved predictions of invasion potential.

Behavioral responses of the Iberian waterfrog, Pelophylax perezi (Seoane, 1885), to three nitrogenous compounds in laboratory conditions

Several studies have assessed the effects of nitrogenous compounds on amphibian behavior. However, few have focused on the effects of their combination with other stressors or on the variation of the response to pollutants among populations. We analyzed the effect of nitrogenous compounds (NH(4)(+); NO(2)(-); NO(3)(-), both alone and in combination) on larval behavior (activity level and location in the water column) in four populations of Pelophylax perezi naturally exposed to different levels of eutrophication. Larval activity was highest and use of the bottom of the experimental beaker was lowest at lower concentrations of nitrogenous compounds acting singly, these responses being minimal and maximal, respectively, at both control and higher concentrations. This pattern appears to fit to an hormetic response. Additionally, the combination of nitrogenous compounds affected more severely the response variables than when ammonium or nitrite acted singly according to an additive model. Populations inhabiting highly polluted aquatic habitats marginally showed higher activity level than the populations from less polluted environments, especially when larvae were exposed to ammonium or when nitrite appeared in combination with other nitrogen forms. Levels of activity correlated positively with larval final mass. Moreover, for similar levels of activity, larvae from polluted populations had higher growth rates than those coming from reference populations which suggests interdemic differences in behavioral sensitivity to nitrogenous pollutants.

A comparative analysis of eco-toxicity of crude oil pollution on the chlorophyll biosynthesis in two agro-forestry species

A short-term ecological study was conducted to ascertain the degree of envisaged impact of petroleum pollution to biota (macrophyte) in a polluted habitat. The biosynthetic process in chlorophyll content reflects the level of the photosynthetic activities. It was envisaged that such biosynthetic process of pigment formation could become a sensitivity index to any polluted environment. To this end, this study has elucidated the importance of petroleum on photosynthetic capacity of two agroforestry species (Leucaena leucocephala and Bauhinia monandra). The relative accumulation of the pigments was used to evaluate the influence of petroleum on the biosynthetic process of the plant species in focus. Results have established (with the variation in the optical transmittance of the pigment) the concentration of the chlorophyll pigment in various pollution intensities. The result showed 4792 mg/g in the control for L. leucocephala. 3195 mg/g, 1118 mg/g and 958 mg/g with percentage depression of 58.6%, 68.7% and 76.5% in the respective (25, 50 and 100 ml) pollution levels. B. monandra had 1438 mg/g in the control. 1118, 958 mg/g and 479 mg/g) and (%) depression of 59.9 69.0 and 78.1 (%) respectively. The variations in the species pigment content indicate the predicament of both species and consequently their sensitivity potential to a polluted habitat. Hence such index provides a means of determining the importance of petroleum in accounting for photosynthetic rate and yield potential under environmental condition. Keywords: Leucaena leucocephala, Bauhinia monandra, chlorophyll, crude oil toxicity, oil pollutionGlobal Journal of Environmental Sciences Vol. 4(2) 2005: 127–130

Metallothionein Induction in the RTH-149 Cell Line as an Indicator for Heavy Metal Bioavailability in a Brackish Environment: Assessment by RT-Competitive PCR

Estuarine and marine near-shore environments are often subjected to heavy metal pollution. We establish a bioassay using the quantitative evaluation of metallothionein (MT) transcript in the fish hepatoma cell line, RTH-149, as a tool for detecting heavy metal pollution in brackish-marine water containing other pollutants in addition to heavy metals. RT-competitive polymerase chain reaction was used for the quantitative evaluation of the transcript in absolute units. Cadmium was used as a model pollutant to optimize two parameters of the assay: exposure periods (24, 96, 144 h) and salinity (0%, 25%, 50%, 75%, 100% sea water). Results revealed that salinity at or below 25% sea water at an exposure period of 144 h are the preferable conditions for detecting MT mRNA levels for in vitro assays employed on water samples from highly polluted brackish habitats.

Efficacy of aqueous suspension and granular formulations of Bacillus thuringiensis (Vectobac) against mosquito vectors

The efficacy of aqueous suspension (AS) and granular (G) formulation of Bacillus thuringiensis var. israelensis (Vectobac) was tested against the immatures of mosquito vectors in the laboratory and under field conditions. Laboratory tests showed that the aqueous suspension was relatively more effective against Culex quinquefasciatus than Aedes aegypti and Anopheles stephensi, the respective LC 50 values being 0.046, 0.060 and 0.190 mg/l. In stream pools, with the application of Vectobac AS at 1.2 l/ha, more than 80% reduction in immature density of Anopheles larvae (Anopheles fluviatilis and Anopheles culicifacies) was observed for 2–8 days, and at 2.4 l/ha for 3.5–9.0 days. At the dosage of 7.0 kg/ha of the granular formulation, a reduction in immature density by more than 80% was observed for 2–9 days. In polluted habitats such as cesspits, U-drains and cement tanks, the effectiveness of Vectobac AS lasted for 1–4 days when applied at 1.2 and 2.4 l/ha, and Vectobac G was effective for 1–3 days at application rates of 7.0 and 14.0 kg/ha against C. quinquefasciatus. There was no significant difference in the effectiveness between the two formulations and the two application rates.

Effects of Cadmium and Environmental Pollution on Metallothionein and Cytochrome P450 in Tilapia

Tilapia are widely distributed freshwater fish frequently used for environmental toxicology, comparative biochemistry and physiology studies. Tilapia can persist in a highly polluted habitat and have the potential for the development as a biological monitor of environmental pollution. Metallothioneins (MTs) are a group of small-molecular-weight cytoplasmic proteins induced in many animals including fish, following exposure to metals such as cadmium, copper, zinc, and mercury. An increasing number of reports have indicated that fish MT induction is a sensitive measure of metal contamination in the environment. Fish cytochrome (P450)-dependent monooxygenases are inducible by many environmental pollutants including polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). Extensive studies have suggested that fish monooxygenase can serve as a biochemical marker for exposure to PAH- and PCB-types of pollutants. Tilapia P450 is highly responsive to the inductive effects of PAH and PCBs. Tilapia collected from a polluted section of a river showed higher levels of P450 and dependent monooxygenase activities than tilapia collected from an unpolluted section. Previous studies showed that pretreatment with Cd decreased microsomal monooxygenase activities in fish such as plaice, bass, and trout. However, direct information regarding the effects of heavy metals on tilapia P450 are not available. Reports concerning themore » effect of heavy metal on tilapia MT are scarce. The purpose of the present study was to determine the ability of cadmium to modulate P450 and MT in tilapia liver and gill. In addition, we have extended our study to feral tilapia collected from Er-Jen Stream, a polluted river in Taiwan. 16 refs., 1 fig., 2 tabs.« less

Resource-mediated effects of stream pollution on food absorption of Asellus aquaticus (L.) populations.

The role of interactions between chemical perturbations and biological constraints on detritivores occurring in polluted streams were investigated by analysing food absorption variation with stress. Absorption rate and efficiency of four Asellus aquaticus (L.) populations from differently polluted habitats were quantified with respect to the microbial guilds colonizing detritus. A twin tracer method was used. Detritus was microbially colonized in standard conditions and on each stream bottom to control for potential resource-independent variations among individuals. The relationship between length and weight was also determined on a random sample of individuals of each population. Differences of 14.6% in potential absorption efficiency and 11.3% in potential absorption rate were observed between populations from the least and the most polluted habitat. Actual ("realized") variations were much stronger: from a minimum of a 60.1% reduction in absorption efficiency to a maximum of 93.8% for the rate. The realized food absorption and the individual weight per length showed the same pattern of variation among populations. This suggested that the availability of energy to isopods in nature was related to stream pollution and resource quality. Bottomup interactions appear to be the most relevant pathway through which chemical water pollution affects the Asellus populations studied. The potential resource-independent variations among individuals are also likely to be explained by temporal cascading of resource-mediated effects.

Intense and localized benthic marine pollution around McMurdo Station, Antarctica

Benthic sediments and animals are highly modified by human activities at McMurdo Station, the largest human settlement in Antarctica. The quantity of anthropogenic debris, contamination of marine sediments with hydrocarbons and metals, and gross changes in benthic communities are largely confined to Winter Quarters Bay, adjacent to the former dump site and the ice dock used by visiting ships. Levels of purgeable hydrocarbons in bay sediments are as high as 4500 ppm. Metal levels are mostly high within the bay, but are not greater than in the most polluted temperate habitats. Levels of anthropogenic chemicals are significantly higher in the back bay compared to stations established at different distances from the bay (along three potential contamination gradients), including reference sites many kilometres away. There are significant negative correlations between the total number of infauna or epifauna and the concentrations of hydrocarbons and most metals in sediments. The few animals living in the back bay are motile polychaete worms with opportunistic life histories, primarily Capitella capitata antarcticum and Ophryotrocha claparedii. Fortunately, the local physical setting apparently permits little transport of contaminated sediments from the bay, which is flanked on one side by a large submarine ridge and on the other by Hut Point. Hut Point also protects the bay from oceanic conditions. The back bay is over 30 m deep and the ridge top is only 18 m deep. The gradient of chemical and community change is extremely steep, but there are observable ecological impacts outside the bay along the front of the station. Although most historical inputs of pollution are removed or reduced and continued cleanup is planned, Winter Quarters Bay may require many decades to recover.

Seasonal changes in metal levels (Cu, Pb, Cd, Zn and Ca) within the grey field slug, Deroceras reticulatum, living in a highly polluted habitat

Slugs ( Deroceras reticulatum) (Muller)) were collected from a disused Pb/Zn mine site for a period encompassing 3 years. The analysis of whole body replicates, collected monthly for a period of one year, demonstrated a large variability in metal concentrations for each of the five metals (Cu, Pb, Cd, Zn and Ca) analysed. Nevertheless, a number of significant monthly differences in metal levels were found, the most regular being for Ca, and the least regular for Cu. Significant differences in metal body burdens were also found between slugs collected during the same month, but in consecutive years. The presence of such large and irregular variability greatly restricts the potential value of terrestrial slugs as biomonitors of heavy metal contamination.

Comparison of mussels and crustacean plankton to monitor heavy metal pollution

The ability of freshwater organisms (mussels — Unio pictorum L. and crustacean plankton —Cladocera and Copepoda species) to monitor heavy metal pollution was compared under field conditions, near the effluent discharge of a sewage water treatment plant at Lake Balaton (Hungary). The mussels were transferred from their less polluted habitat to the study area. The crustacean plankton was collected at this site The concentrations of Hg Cd Cr Cut Pb, Zn, and Fe were measured m the gills of the transplanted mussels as well as the natural zooplankton in the summer period, using the AAS method. Both mussel gills and the zooplankton showed periodically high Fe-, Zn-, and Cu-concentrations. An elevated level of Hg was only observed in mussels, while high Pb- and Cr-concentrations were found only in crustacean plankton. Accordingly the zooplankton seems a more suitable model for monitoring heavy metal pollution under these field conditions.

Utility ofBacillus sphaericusin controllingCulex tritaeniorhynchusbreeding

Freeze-dried powder preparation of a streptomycin-resistant (Str) mutant of Bacillus sphaericus B.42 was applied against Culex tritaeniorhynchus larvae breeding in paper factory effluent. Whether applied as single, double or triple sprays on days 0, 1 and 2, respectively, a complete control of larvae was observed only until day 7 post application. Though the applied strain of B. sphaericus persisted (in the sprayed pits) at least until 91 days, as evident from larval resurgence, the sprayed B. sphaericus did not recycle in paper factory effluent. Whenever the heat-resistant spore counts dropped below approx. 600/ml, a build-up in larval population was observed. The Str mutant strain of B. sphaericus used in the present study seems to be an effective biocide capable of persisting and controlling C. tritaeniorhynchus larvae breeding in such a highly polluted water habitat as paper factory effluent.

PATTERNS OF ALGAL SUCCESSION IN A PERTURBATED MARINE INTERTIDAL COMMUNITY1

ABSTRACTPatterns of algal succession for a sewage‐polluted and an unpolluted habitat near Wilson Cove, San Clemente Island, California, were studied from December 1974 to June 1977. Resident populations were analyzed for 56 fully denuded and 34 undisturbed control quadrats during 11 assessment periods. The denuded quadrats in the perturbated (polluted) habitat showed recovery within 1.0 mo as determined by cover, percent similarity and species diversity comparisons with control plots. The short recovery times of the algal populations dominating the perturbated habitat indicate that these species maintain relatively constant overall abundances due to their potential for rapid recruitment and growth. Denuded quadrats in the unpolluted habitat did not show recovery even after 30.0 mo. These quadrats were dominated during the first 1.3 mo by algae characteristic of the perturbated area, including filamentous Ectocarpaceae, colonial diatoms and bluegreen algae. Petalonia fascia (Müll.) Kuntze (1.3–3.0 mo), and Scytosiphon lomentaria (Lyngb.)J. Ag. and Colpomenia sinuosa (Roth) Derb. & Sol. (1.3–5.0 mo) were abundant shortly following plot denudation and provided thick growths that may have excluded other algae. The similarity between the species occupying the sterilized plots during the first few months and those that provide the majority of cover in the perturbated area supports the hypothesis that the dominant algae of the upper and midintertidal regions of this habitat consist largely of early successional or opportunistic species with high capacities for growth and reproduction. Additionally, these experiments suggest that algal populations described for other perturbated epilithic systems also represent resilient subclimax associations.

Influence of Domestic Wastes on Energetic Pathways in Rocky Intertidal Communities

SUMMARY (1) The calorific contents of eighteen macroinvertebrates and thirty-six macrophytes'were determined in an unpolluted rocky intertidal habitat and in a nearby polluted habitat. (2) Much of the variation in the calorific values of macrophytes was related to life span. The algae that characterized the unpolluted community usually contained comparatively fewer calories per unit weight. These forms had relatively more structural tissues and hence allocated relatively less energy to rapid growth and reproduction. In the polluted habitat, fugitive or opportunistic algal species were more prevalent; these had more rapid growth rates and higher productivities and tended to have relatively high calorific contents. Encrusting forms, that are easily accessible to many herbivores, had thallus constituents with lower calorific values, suggesting that these algae may have evolved reduced palatability. (3) The major taxonomic groups of algae yielded the following sequence of mean calorific values: Chlorophyta, 4-78 kcal g- I ash-free dry weight; Rhodophyta, 4 39; Cyanophyta, 4 38; Phaeophyta, 4 22. (4) In nearly every case, macroinvertebrate populations exposed to domestic sewage had higher energy contents than did corresponding populations from the unpolluted habitat. (5) Macroinvertebrates in the polluted habitat grazed greater proportions of blue-green algae and bacteria. Omnivores and suspension feeders in the polluted habitat appeared to utilize energy-rich compounds in the sewage effluent; this may explain the greater standing stocks of omnivores and suspension feeders in the peripheral regions of the outfall plume.

Studies of tolerance to heavy metals in the flora of the rivers Ystwyth and Clarach, Wales

SummaryA survey of the river Ystwyth demonstrated that it was polluted with metals especially below the areas of old lead mines. Hormidium spp. Kütz in particular Hormidium rivulare Kütz were the most tolerant filamentous green algae present. Scapania undulata (L.) Dum. was a tolerant bryophyte on the Ystwyth and Clarach rivers and was found alone in polluted sites, but was less frequent in cleaner areas. Metal extracts of this bryophyte mirrored the variation in metal concentrations of the environment to some extent. In general, lower levels of Fe, Pb and Mn were found in Scapania as compared with the less tolerant Fontinalis squamosa Hëdw. When the latter was transplanted to polluted sites an increase in its Pb, Cu, Zn and Mn content occurred within 6 weeks and the plant started to die and decay after 18 weeks. Scapania survived when it was transplanted from its natural polluted habitat to a less polluted area, and there was no marked change in its metal content. Zn65 tracing experiments, in the laboratory, demonstrated that both plants had similar uptake patterns for the metal, but that the amount taken up was slightly higher in the less tolerant Fontinalis. There was no change in the number of diatoms found upon Scapania when it was transplanted, but a reduction in numbers occurred on the transplanted Fontinalis when it started dying. The composition of these diatom floras was different in polluted sites as compared to that in the cleaner areas.