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1.
In this study, we investigated the long-term (2-year) response of a detritus-based food web to resource depletion simulated in microcosms filled with lake sediment. The effects of resource depletion on the food web were estimated from the biomass responses of a simplified, size-based trophic network comprising three trophic levels: (1) bacteria, (2) bacterivorous meiofauna, and (3) omnivore/predacious nematodes and oligochaetes. The results showed that sediment bacteria and organic carbon stock were not affected by resource depletion, whereas oligochaetes, large nematodes and some bacterivores, such as rotifers and ostracods, decreased dramatically. At the same time, resource depletion had no negative effect on minute bacterivorous nematodes and harpacticoid copepods, suggesting their release from competition with other bacterivores and/or their release from potential predation by large nematodes and oligochaetes. Our results globally confirmed classical trophic dynamics models in which a shortage in resources dampens food-chain length. Yet, low resources did not completely eliminate all large invertebrates, and did not affect the standing stock of detritus and bacteria, suggesting that detritus-based food webs could show a remarkable resilience to the effects of resource depletion.  相似文献   

2.
160 taxa of macrozoobenthos were recorded in the Danube River (R. km 1880-1704) riparian zone. Many typical Danubian and Pontocaspian representatives were found. The Slovak section of the Danube represents the border between its epipotamal and metapotamal stretches with different flow velocity and other environmental variables related to it. This paper characterises some abiotic ecological factors influencing the distribution of benthic taxa in five sampling sites along the longitudinal profile of the Danube. The benthic community composition was more strongly influenced by hydrological parameters than by oxygen and temperature regimes, as well as by the water quality conditions. In other words, the bottom substrate, flow velocity, water level fluctuation and discharge changes had the predominant effect on the taxocoenoses of macrozoobenthos. Three characteristic groups of macrozoobenthic organisms were recorded, as far as corresponding trophic guilds are concerned. Shredders and scrapers predominated in high flow velocity conditions with coarse substrate particles. Collectors of fine organic matter preferred slow-flowing conditions caused by damming or by a reduction of current due to the presence of bedrock. Filterers prevailed in the lower section of the Danube stretch monitored. Predators occurred independently of the environmental variables studied.  相似文献   

3.
Meiofauna serves as a link between microbial production and higher trophic levels, such as macroinvertebrates and juvenile fish. However, the role of meiofauna in the freshwater food web has not been accurately evaluated, and the influence of shrimp predation on freshwater meiofaunal assemblages is unknown. In this study, the predation effects of Neocaridina davidi, an ornamental freshwater shrimp native to inland water bodies in Asia, on meiofaunal density, biomass, structure, and secondary production were examined using model ecosystems (microcosms) that were sampled repeatedly over 42 days. Shrimp predation altered the structure of the meiofaunal community over the course of the experiment, in particular the density, biomass, and secondary production of nematodes, microcrustaceans, and oligochaetes. An analysis of the stomach contents of N. davidi indicated a high degree of omnivory and the frequent consumption of meiofaunal organisms. The results indicated that predation by the freshwater shrimp N. davidi depresses the overall abundance, biomass, and secondary production of meiofaunal assemblages. Moreover, they also provide insights into food-web ecology and the first evidence of freshwater shrimp predation on meiofaunal assemblages.  相似文献   

4.
Short and long term effects of a fuel oil spill from a grounded ship "M V Sea Transporter" on meiofauna of a sandy beach of central West Coast of India were investigated. A significant reduction in the absolute abundance of meiofauna was observed immediately after 3 days of spillage particularly at Sinquerim beach, the site of spillage. The reduction was most pronounced in density of nematodes and harpacticoid copepods, which were the most dominant groups. Long-term response showed no apparent oil-induced changes at major taxa levels. The population density improved considerably after the cessation of monsoons with a parallel decrease in petroleum hydrocarbon concentration in the sediment. Nematodes recovered more quickly than benthic copepods. No evidence for this could be due to reproductive dynamics in meiobentos. Although the effect of the oil on meiofauna could be seen initially it could not be proved conclusively on a long-term basis. The effects of the oil spill were confounded with seasonal monsoon effects and beach dynamics. The nematode:copepod ratio and the index of trophic diversity (ITD) were inadequate for detecting oil pollution effects. Therefore it may be concluded that in the presence of other environmental factors acting strongly, the effects of oil on meiofauna was strong but of a temporary nature.  相似文献   

5.
Interannual variability (2003-2008) of meiofaunal assemblages were analyzed in sediments beneath fish cages (Impact group) and in areas not affected by aquaculture activities (Control group). Organisms responded with spatial and seasonal variation in meiofauna assemblages, with an abrupt increase of abundances in locations beneath fish cages throughout the study period. This increase was greater during the last sampling year (2008) and mainly due to high abundances of nematodes. Univariate analyses showed differences between control and impacted sites at both sites, however, only significant variations were found in Los Gigantes, which are consistent with seasonal meiofauna variations throughout the study period. These results are partially explained by differences in current velocity between both sampling areas. The Ne/Co index showed the same trend and it seems to be a reliable index in sediment slightly affected by aquaculture wastes. This index is especially recommended in oligotrophic areas (e.g. Canary Islands) where meiofaunal assemblages are poorly represented in terms of abundances.  相似文献   

6.
《Marine pollution bulletin》2012,64(5-12):318-325
Sediment quality, meiofaunal and nematode communities were monitored across six time points at two inside-harbour and three outside-harbour sites over a three-year period in Victoria Harbour, Hong Kong, after the implementation of a sewage treatment project. Twenty-one meiofaunal groups comprising mainly free-living nematodes and harpacticoid copepods and 188 species of free-living nematodes were identified. The outside-harbour area had a more diverse and significantly different nematode community structure as compared to that in the inside-harbour area. Such spatial difference was highly correlated with the total Kjeldahl nitrogen content of the sediments. Over the study period, there was no significant improvement in sediment quality within the harbour. However, in the last sampling time, an increase in meiofaunal abundance and a closer similarity in nematode composition between one of the inside- and outside-harbour sites suggested signs of recovery of the meiofauna as a response to abatement of sewage pollution.  相似文献   

7.
Sediment quality, meiofaunal and nematode communities were monitored across six time points at two inside-harbour and three outside-harbour sites over a three-year period in Victoria Harbour, Hong Kong, after the implementation of a sewage treatment project. Twenty-one meiofaunal groups comprising mainly free-living nematodes and harpacticoid copepods and 188 species of free-living nematodes were identified. The outside-harbour area had a more diverse and significantly different nematode community structure as compared to that in the inside-harbour area. Such spatial difference was highly correlated with the total Kjeldahl nitrogen content of the sediments. Over the study period, there was no significant improvement in sediment quality within the harbour. However, in the last sampling time, an increase in meiofaunal abundance and a closer similarity in nematode composition between one of the inside- and outside-harbour sites suggested signs of recovery of the meiofauna as a response to abatement of sewage pollution.  相似文献   

8.
Despite meiofauna being one of the most popular tool for detecting the ecological effects of different sources of impact, the application of structured experimental designs to this benthic component is typically neglected, especially in subtidal rocky shores. In this study, an asymmetrical design was used to detect hard-bottom meiofaunal abundance and biodiversity response to sewage discharge. Sampling was carried out at a depth of 3-4 m by SCUBA diving, by means of a modified manual corer. Six replicate cores were collected at three sites (80-100 m apart), at each of three locations (one purportedly impacted [I] and two controls [Cs]). A total of 84,994 specimens were collected. The outfall affected meiofaunal assemblages in terms of taxon richness, by determining a significant reduction of the number of taxa in the disturbed location, and community structure, by causing functional changes in terms of a decrease of the abundance of nematodes and an increase of the hydrozoan component. Nematodes and syllid polychaetes showed significant lower average abundance at I. Multivariate analyses showed that both meiofaunal assemblage and syllids were significantly different at I compared with Cs. The sewage outfall also affected patterns of spatial distribution at the scale of site (100 m apart) and of replicate units (centimetres apart), both in syllids and in nematodes. Our results provide evidence that the selection of multiple controls is crucial to prevent the widespread risk of Type II error, highlighting the need of more accurate experimental designs when dealing with meiofauna.  相似文献   

9.
Sediment chemistry and meiofaunal samples were collected in the Broughton Archipelago, British Columbia, to examine the relationship between sediment variables and meiofauna diversity across near- and far-field gradients surrounding several finfish aquaculture operations. The sediment variables examined consisted of free sulfide concentrations, redox potential (E(NHE)), organic content, and sediment grain size. A strong trend between sediment texture and organic content was observed across all sampling locations, which reflected a wide range of sediment types (sand-silt) that exist within the Broughton Archipelago. The abundance of certain meiofaunal groups (kinorhynchs, crustaceans, polychaetes) declined in an asymptotic fashion with increasing free sulfide concentrations, an indicator of benthic organic enrichment. Within these relationships, low meiofaunal abundances occurred in fine sediments associated with higher organic contents. Although other groups (nematodes, foraminifera) showed a slight decline in abundance with increasing organic enrichment, a high amount of variability in abundance was observed at high free sulfide concentrations, rendering these groups not suitable as indicators of organic enrichment. This study reports both horizontal and vertical trends in meiofaunal distributions relative to free sulfide concentrations. The abundance of nematode and crustacean taxa decreased with sediment depth as well as increasing sulfide concentration, while polycheate abundance increased with increasing free sulfide concentration. The ratio of nematodes to copepods was also shown to represent the degree of organic loading associated with aquaculture operations and its application as an indicator of benthic impact is discussed.  相似文献   

10.
Dixidae (Insecta, Diptera) are an interesting ecological component in freshwater ecosystems. They are merolimnic insects with larvae and pupae living in aquatic habitats while adults live in terrestrial habitats in close proximity to water. The goals of this study were to determine the phenology patterns of Dixidae and what influences them, to analyse their preference for microhabitats, and to determine the main ecological factors that have an influence on the composition of Dixidae. Adult Dixidae were collected monthly in the period from 2007 to 2008 at 10 sites, from 2009 to 2010 at four sites, and from 2011 to 2014 at three sites in the Plitvice Lakes National Park. Adult specimens were collected using pyramid-type emergence traps. A total of 1271 Dixidae were collected during eight years of study belonging to five species of the genus Dixa. Dixa submaculata was most abundant species at the spring and upper reach of Bijela rijeka Stream and the upper reach of Crna rijeka Stream. Dixa nebulosa was most numerous at the Kozjak-Milanovac tufa barrier site. Dixa puberula was the dominant species at the rest of the sites. Dixa puberula and Dixa submaculata were univoltine, bivoltine or trivoltine, depending on the site, while Dixa nebulosa was only univoltine. The highest diversity was recorded at the tufa barrier Kozjak-Milanovac, and the highest number of species, four species, was found at the upper reach of the Crna rijeka Stream. The greatest number of specimens was recorded at the Labudovac tufa barrier, 128 specimens in 2014. Water temperature is the main ecological factor that influences the phenology of Dixidae at the tufa barriers and lower streams. Discharge affected the abundance of Dixidae. Dixa puberula prefers moss as a substrate and a faster water velocity.  相似文献   

11.
Insects of the orders Ephemeroptera, Plecoptera, and Trichoptera (EPT) are prominent among stream biota and are associated with many ecological processes in these environments, meaning that a proper definition of their habits is essential. We studied EPT from three watersheds in Brazil (Paraguai, Paraná, and São Francisco) in order to (i) determine the trophic guilds of EPT genera sampled; (ii) determine whether trophic guilds reflect EPT phylogenetic component (taxonomic distance); (iii) compare trophic guild composition among watersheds; and (iv) verify the effect of environmental components in trophic guild composition. Eight trophic guilds were determined based on gut content analysis: detritivores, fine-detritivores, fine-detritivores/algivores, coarse-detritivores, coarse-detritivore/algivores, periphytivores, carnivores, and omnivores. Caddisflies presented the most variable diet and many genera belonged to different trophic guilds in different basins. Overall trophic guild composition did not reflect the taxonomic distance among taxa and it did not differ among the three basins. Instead, EPT guilds were related to local environmental variables, evidencing that their diet probably varies according to local resource availability, highlighting the importance of empirical assessments of diet for ecological studies.  相似文献   

12.
Feeding interactions among functional feeding groups (FFGs) of macroinvertebrates are robust indicators of aquatic ecosystem interactions. They provide information regarding organic matter processing, habitat condition and trophic dynamics. In tropical rivers with pronounced wet and dry seasons, macroinvertebrate based ecological monitoring tools are explicitly focused on metrics and indices, while ignoring interactions of FFGs. Therefore, the objective of this study was to investigate the functional feeding type metrics, diversity indices and feeding interactions among FFGs of macroinvertebrates along the water pollution gradient in Gilgel Gibe watershed, Ethiopia. Water quality parameters and macroinvertebrate community attributes were assessed for samples collected from upstream sites (15 sites), urban-impacted stretches (12 sites) and wetland-affected river zones (7 sites) of the watershed during the rainy (July) and dry (February) seasons. To understand the effect of pollution on the feeding interactions, stable carbon and nitrogen isotopes were analyzed. Macroinvertebrate-based diversity indices and functional feeding type metric showed deterioration of ecological integrity at the urban-impacted sites and substantial recovery in the wetland-affected downstream sites. Omnivorous feeding behavior of macroinvertebrates was noted for the upstream sites, whereas clear trophic guilds of FFGs were suggested for the wetland-affected river zones by the stable isotope results. The results of pollution gradient analysis and feeding interactions among FFGs revealed that the urban-impacted sites showed weaker interactions when compared to upstream and wetland influenced sites. This affirms the potential importance of feeding interactions among FFGs of macroinvertebrates in water quality monitoring.  相似文献   

13.
A two-year study was conducted in the vicinity of a harbour in sub-tropical Hong Kong, to examine the progress of recovery of macrobenthic community, based on analyses of both life-history traits and trophic guilds of polychaetes, upon cessation of organic pollution caused by sewage discharge. Seventy seven out of 83 species collected were classified under four ecological groups based on the life-history traits and sensitivity to organic gradients. The mean ATZI marine biotic index (AMBI) derived from these ecological groups showed spatial difference among the five sampling locations. In particular, the presence of different percentages of polychaete species from Groups III (unbalanced community) and IV (polluted community) suggested the presence of pollution stress in certain degree at all sampling locations. However, no significant temporal changes were noted over the study period. From all polychaete species identified, they were classified into 13 feeding guilds. The mean diversity of these feeding guilds at most of the sampling locations was significantly higher than that at one of the inside-harbour locations. The composition of feeding guilds was also significantly different spatially. At one of the inside-harbour locations, the dominant feeding guilds were motile/discretely motile surface deposit feeders with tentaculates or unarmed pharynx, and motile omnivores with jawed pharynx in the first year of study, but were replaced by motile, jawed carnivores in the second year of study. The increased proportion of carnivores over the study period can be seen as a sign of recovery in the community structure since abundance of predators is commonly higher in habitats with better environmental quality. The implications of using life-history traits and feeding guild analyses for benthic community are discussed.  相似文献   

14.
Within the shallow littoral zones of lakes, periphyton is an essential component, representing an important source of primary production and a food resource for herbivores. Periphytic communities are abundantly inhabited by meiofaunal organisms, which are mostly dominated by nematodes. During the last 3 decades, consumer–resource interactions between herbivore consumers and periphytic components (mainly algae) have been intensively studied. Although whole grazer community and single species effects on periphyton are known from field and laboratory experiments, the importance of single, dominant grazer taxa in direct comparison to whole community impacts is unknown. To investigate the continuity of grazing effects of a single, dominant macrograzer (Theodoxus fluviatilis, Gastropoda, Prosobranchia) on epilithic meiofauna and algae with respect to the whole grazer community, a temporally structured field experiment was carried out in Lake Erken (Sweden). Grazer impacts on periphytic algae and meiofauna were tested by controlling macrograzer access to littoral periphyton communities for 8 weeks in an exclosure/enclosure experimental design. Overall, the results showed macrograzer presence to have temporally constant, strongly negative effects on algal biomass as well as meiofaunal abundance and community composition. Moreover, T. fluviatilis alone accounted for up to 80% of the grazing effects, indicative of their ability to regulate periphytic communities in lakes. The present study yields new insights into the effects of a single grazer species and stressed temporal patterns of consumer–resource interactions in freshwater lakes.  相似文献   

15.
Among the most important impacts of trawling is the disturbance of the benthic environment as well as the mortality of the larger benthic organisms, which is caused by the passage of the fishing gear. Meiofauna, which are among the smallest benthic organisms, may be more resistant to disturbance by trawling since they are likely to be re-suspended rather than killed by trawls. Their short generation times allow populations to withstand elevated mortality. In this study, we determined the effect of trawling disturbance, season and sediment type on the structure of meiofaunal communities in a commercial fishing ground in Thermaikos Gulf, north Aegean Sea, Greece. The trawling season is limited to 8 months between October and May. A grid of five nearshore stations was chosen along a north–south productivity gradient and an additional offshore station was included as a reference point. Sediment chemistry and meiofaunal community structure were studied before the trawling season started, as well as 1 and 4 months after the initiation of the fishing period. Results showed that there were no short term (30 days) trawling impacts on meiofauna in terms of abundance and community structure but that there were recognizable effects on the community structure of nematodes and the abundance of polychaetes. In contrast, most meiofaunal taxa displayed significant seasonal variability, 4 months after the initiation of the fishing period; however, other closely related factors such as temperature, sediment particle size and primary productivity are more likely to be responsible for the observed patterns.  相似文献   

16.
The influence of raw domestic sewage on density and distribution of meiofauna in the sea bottom sediments in the Northern Adriatic Sea, in the area of Rovinj (Yugoslavia), was investigated, comparing meiofaunal density at the stations which are under direct influence of sewage and the stations which are far from the source of pollution. It is concluded that raw domestic sewage does not have a negative influence on the density and distribution of meiofauna, but Parker's index of pollution indicates that meiofauna at these stations were under stress.  相似文献   

17.
The effect of recent drilling operations (fluid and well cuttings) on polychaete feeding guilds from the continental shelf off Atlantic City, New Jersey, was examined. Although there were some adverse effects on macrobenthos from 2160 metric tons of cuttings and mud solids discharged into the marine environment, the composition of polychaete feeding guilds remained essentially unchanged. This key trophic relationship between polychaetes and the changing environment due to the drilling operation was apparently uninterrupted. This relationship remains to be examined in other natural and perturbed habitats.  相似文献   

18.
We compare foraminifera and macrofauna as bio-indicators of oil-based drill mud disposal site off Congo. The most polluted sites are characterized by poor faunas, dominated by some very tolerant taxa. Slightly further from the disposal site, there is an area with strongly increased densities, heavily dominated by opportunistic taxa. Still further, macrofauna appears to be similar to that at the reference area, but the foraminiferal meiofauna still suggests a slight environmental perturbation. The foraminiferal FIEI index, based on the species distribution in the study area, appears to be more discriminative than the macrofaunal ITI index, based on a priori definitions of the trophic guilds of the various taxa. Our comparative approach allows us to point out the benefits of (1) the use of macrofauna and foraminifera together and (2) the definition of the species groups used in biotic indices on the basis of observations made directly in the study area.  相似文献   

19.
The hunter-fly genus Limnophora (Muscidae: Coenosiinae) is an important component of running water assemblages. Both adults and larvae are predators, the adults mostly feeding on blackflies (Simuliidae) and other small aquatic insects. This study was conducted at two tufa barriers in Plitvice Lakes National Park (NP) (tufa barrier Labudovac and tufa barrier Kozjak-Milanovac) and at two tufa barriers in Krka National Park (NP) (tufa barrier Roški slap and tufa barrier Skradinski buk). Adults were collected monthly from February 2007 until December 2013 at Plitvice Lakes NP and from September 2013 to October 2014 at Krka NP, using pyramid-type emergence traps. Over the 7-year study period at the Plitvice Lakes tufa barriers, a total of 193 specimens belonging to 6 species were collected, while during the 1-year study period at the Krka tufa barriers a total of 848 specimens belonging to 4 species were collected. Abundance of Limnophora specimens at the Krka NP sites was up to 30 times higher than at the Plitvice Lakes NP sites, which could be attributed to higher levels of potential food and higher water temperatures. The dominant species at the Plitvice Lakes sites were Limnophora pulchriceps and Limnophora riparia. At the Krka tufa barriers, the dominant species at site Roški slap was Limnophora croatica and at site Skradinski buk Limnophora riparia. The highest numbers of emerging specimens at all sites were present in the summer months. At the Plitvice Lakes sites most species were univoltine or bivoltine, while at the Krka sites most species were multivoltine. Water temperature was the main factor influencing the timing of emergence and the duration of the flight period. The highest abundance of Limnophora species was recorded over moss substrate. A significant positive correlation emerged between the numbers of emerging prey and the numbers of emerging specimens of Limnophora. These results give a new insight into the microhabitat preferences and prey-predator relationships of Limnophora.  相似文献   

20.
Polychaete feeding guilds have recently been examined as potentially useful parameters in environmental impact assessment. Densities of polychaete species from three studies in the lower Chesapeake Bay were classified into feeding guilds and correlated with water depth, median phi size and percent silt-clay of the sediment. Polychaete densities were also grouped randomly and correlated with environmental variables. For two of the three studies a feeding guild classification did not give significantly more correlations than expected from random groupings. Problems associated with using polychaete feeding guilds as composite biological variables are discussed.  相似文献   

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