Bott, T. Primary Productivity and Community Respiration.
Academic Press, Boston. Skip to main content. Julia Larouche. Associated Researcher. Sites sampled. Download EML.
Methods Stream Ecology
Download a comma delimited csv or Excel file includes metadata and data sheets. File Details. Excel file with USt Label: X. DSt Label: X. BP Label: X. Biomonitoring activities on aquatic ecosystems, which are probably the commonest way to obtain constant aquatic macroinvertebrate samples and data, originate from fieldwork done in the daytime.
Methods in Stream Ecology, Second Edition - PDF Free Download
Any nocturnal activity is usually avoided for safety reasons, and also given the logistical constraints on researchers and technicians. Existing studies that are directly related to light and darkness dynamics in streams have generally investigated the relationship between macroinvertebrate drift and the predatory activity of fish e. In line with this, numerous macroinvertebrate taxa usually demonstrate a peak in drift activity related to darkness or nighttime conditions e.
Night is an important part of the diel cycle and several macroinvertebrates have demonstrated some form of nocturnal activity in different aquatic ecosystems e. In a North American stream, for example, it has been observed that several caddisfly larvae Sericostomatidae burrow during the day and resurface at night Bergey and Resh, Likewise, marine and transitional e.
This study evaluated and compared structural and functional metrics along the same river stretch, and different environmental variables were measured to: i provide a complete and quantitative assessment of day-to-night changes in the riverine macroinvertebrate community; ii assess the relevance of different environmental variables on macroinvertebrate compositions in different diel phases. By addressing the first objective, we can gain an understanding of whether the biological and ecological information obtained during a specific period may be representative of the general condition.
After considering the nocturnal activities of some aquatic taxa and that some physico-chemical stream variables e. We also expected to find main differences in the composition metrics values, such as aggregation. Similar results would demonstrate the consistency of the sampling data in any diel cycle stage. Changes in macroinvertebrate distribution and diel variation are crucial for gaining a clearer understanding of population dynamics in aquatic ecosystems.
Information on the diel activity patterns of macroinvertebrate larvae can enable us to understand the ecological role of particular taxa or groups, and may also prove useful when designing fieldwork studies and strategies. Throughout the article, we used the terms day and daytime to refer to daylight hours, and night and nighttime to refer to periods of darkness, which are in accordance with Helfman This kind of lotic ecosystem is widespread in continental and peninsular Italy as the Apennine Mountains extensively cover the country Gumiero et al. Dense woodlands with small scattered urban areas cover the entire catchment, where riparian deciduous vegetation is abundant.
Riverbed width is approximately 4. As artificial lights, or extended and simulated periods of light and dark conditions, can apparently influence stream communities and associated terrestrial ecosystems e. The gray arrow indicates flow direction.
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On a daily basis, five Surber samples were taken near midday and five near midnight to avoid dates with a full moon in order to maximize variation at natural light levels between night and day. Similar schedules have been considered in other studies e. Fieldwork was conducted at the end of fall, a period during which invertebrate abundance and diversity are generally higher in these ecosystems following natural leaf fall Bo and Fenoglio, The Surber sampler is a quantitative approach data refer to the sampled surface area , and is the most widely used technique in macroinvertebrate research and stream biomonitoring in Italy.
Sampling units were selected to obtain a complete representation of all the microhabitat types along the stretch. However, as benthic taxa are not expected to recolonize disturbed sediments as quickly as other aquatic taxa do e.wechsnigentdealb.tk
Morphology and Flow in Streams
By the time field activities had ended, 70 Surber units had been obtained along the studied stretch: 35 in the daytime D and 35 at nighttime N Figure 1. The use of higher taxonomic levels e. This can make measuring taxonomic richness and composition easier, which enables the study of the entire macroinvertebrate community. Moreover, macroinvertebrate family richness is generally considered one of the main biological metrics in aquatic ecosystem bioassessments e. Birk et al. The richness No.
In order to complement our analysis and to consider functional information, each collected taxon was assigned to a functional feeding group FFG: scrapers, shredders, gatherers, filterers and predators , as set out by Merritt and Cummins Each richness group value No. This is the official multimetric index used in Italy for assessing water course quality status according to European legislation for further details, see Buffagni et al. The index values were obtained and investigated for both the D and N periods. To characterize the study areas and to assess the relevance of different factors, specific site variables water velocity, depth, substrate size and coarse particulate organic matter CPOM amount were measured at each sampling point corresponding to each Surber and were used in the multivariate analysis.
Current velocity was measured with an Eijkelkamp To examine the diel differences in different community descriptors abundance, family richness, Shannon Index, biomonitoring results and functional role richness , t -tests on the transformed data log or square root were run. In these cases, analyses were performed by nonparametric Wilcoxon tests.
To investigate if the daytime and nighttime communities presented different aggregation levels, the Morisita Index of Intraspecific Aggregation Morisita, ; Krebs, was resorted to. In order to assess the differences in the aggregation values between D and N, we examined the differences obtained with what would be expected by chance alone.
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To do this, we compared the difference in the aggregation values obtained in our samples D value vs. A nonmetric multidimensional scaling NMDS analysis was performed to visualize possible dissimilarities or patterns between the macroinvertebrate communities from the different sampling periods D or N using the entire dataset No. Bray-Curtis distance was used as a dissimilarity measure, and stress was employed to test goodness of fit.
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The significance of the fitted vectors was assessed by a permutation procedure permutations. A Permanova analysis Anderson, was carried out using Bray-Curtis distance to test whether there was a significant difference between the a priori proposed division D and N in terms of macroinvertebrate communities.
At the same time, the 2. This analysis evaluates the affinity of each taxon for each a priori -defined group and provides an indicator value herein called IV. All the analyses were performed with the R 3.
The current velocity, depth, CPOM and mean diameter of the substrate of the studied stretch were 0. Each one had more than individuals in all Table 1. The nonparametric estimator of species richness chao2 suggested that at least The results showed that the data sets compiled for the Lemme stream stretch as a whole could be considered realistically complete if compared to the values proposed by other authors e. Table 1 Taxa list and number of individuals obtained in the Lemme stream Order and Family, except Hydrachnidia.
Forty-two taxa were obtained in the daytime and 46 at nighttime. In both cases Chironomidae Diptera and Taeniopterygidae Plecoptera were the most abundant taxa. The biomass mean values for each Surber were 0. According to the intraspecific aggregation values obtained by the Morisita index, the daytime community gave a higher value 1. However, the difference 0.
The NMDS ordinations of the macroinvertebrates communities Figure 2 , first two axes displayed showed no clear clustered patterns, but the daytime and nighttime sites completely overlapped. The final stress value for the three-dimensional ordination was 0. In each case, velocity was the most important variable to be related with community compositions in terms of explained data variance.
Table 2 Results of the t -test between the daytime and nighttime data. Table 3 Correlations of environmental variables with the NMDS ordinations of macroinvertebrates D and N separately and the significance of the correlation based on the envfit function permutations.
In both cases, ecological status always varied between the Good and High classes, with a prevalence of the latter and their p.
Finally, the indicator value analysis did not identify strong groups of indicator taxa for the two community conditions under study D and N. No indicator taxa were obtained for the daytime community, and all the other families displayed low values with no significant relationships found in both cases.
This study analyzed macroinvertebrate communities from daytime and nighttime samplings. No relevant differences were found when taxonomic, functional and biological information was considered. In this freshwater ecosystem Northern Apennine stream , the information obtained at the family level even for biomonitoring purposes during a period daytime or nighttime was representative of the entire diel cycle and macroinvertebrate community.
When focusing on an intermittent small stream in Australia, Dell et al. Similarly, few or no diel differences in invertebrate densities were found in a British river Copp et al. Our findings contrast with our initial prediction.