Should only live diatoms be used in the bioassessment of small mountain streams?

Gillett, Nadezhda D.; Pan, Yangdong; Parker, C.

doi:10.1007/s10750-008-9624-5

Cited by 34 publications

(17 citation statements)

References 25 publications

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“…Our results highlighted the importance to include in the sampling process also those areas where water velocity is null. Even though the collection of diatoms from depositional zones implicates the inclusion of dead frustules in the samples, it has been demonstrated that this does not affect the reliability of the diatom indices final score (Gillett et al, 2009;Barthès et al, 2014). The sampling of lentic MHs leads also to the inclusion of an important component of the community that would be otherwise underestimated, i.e.…”

Section: Discussionmentioning

confidence: 99%

Suggestions for diatom-based monitoring in intermittent streams

Falasco

Piano

Bona

2016

Knowl. Manag. Aquat. Ecosyst.

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-Over the last decades, river lentification processes and droughts have been dramatically spreading worldwide, due to global and local drastic changes due to human activities. Under this scenario, the evaluation of physical disturbance caused by intermittency and droughts has become more and more relevant. In this research, we compare samples collected in Mediterranean streams following both traditional and experimental approaches with the aim of understanding if diatom indices calculated from a new sampling strategy could provide additional information for the physical disturbance assessment. Moreover, we also evaluated the response of functional metrics. Our results demonstrated that even though an enhanced sampling method better reflects hydrological disturbance than the traditional one, diatom indices do not detect it. Conversely, functional traits proved to be important metrics for the hydrological disturbance assessment. In particular, benthic diatom chlorophyll a showed significantly lower values in sections more subject to droughts. With respect to ecological guilds, the motile taxa proved to be linked to depositional areas, which resulted important microhabitats (MHs) to be explored in rivers affected by lentification. Including different MHs in the sampling process improves the information we can obtain from the analysis of the diatom community and presents important implications in documenting species distribution and autecology.Keywords: diatom indices / functional metrics / hydrological disturbance / intermittency / Mediterranean streams Résumé -Suggestions pour la biosurveillance avec les diatomées benthiques dans les rivières intermittentes. Au cours des dernières décennies, les processus de ralentissement des rivières et les sécheresses ont été considérablement répandus dans le monde entier, en raison de changements drastiques globaux et locaux dûs aux activités humaines. Selon ce scénario, l'évaluation des perturbations physiques causées par intermittence et les sécheresses est devenue de plus en plus pertinente. Dans cette recherche, nous comparons les échantillons prélevés dans des rivières méditerranéennes suivant des approches traditionnelles et expérimentales dans le but de comprendre si les indices diatomées calculés à partir d'une nouvelle stratégie d'échantillonnage pourraient fournir des informations supplémentaires pour l'évaluation des perturbations physiques. De plus, nous avons également évalué la réponse des paramètres fonctionnels. Nos résultats ont montré que, même si une méthode d'échantillonnage améliorée reflète mieux les perturbations hydrologiques que la méthode traditionnelle, les indices diatomées ne les détectent pas. À l'inverse, les traits fonctionnels se sont avérés être des paramètres importants pour l'évaluation des perturbations hydrologiques. En particulier, la chlorophylle a des diatomées benthiques a montré des valeurs significativement plus faibles dans les sections plus exposées à la sécheresse. En ce qui concerne les guildes écologiques, les taxons mo...

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Section: Discussionmentioning

confidence: 99%

Suggestions for diatom-based monitoring in intermittent streams

Falasco

Piano

Bona

2016

Knowl. Manag. Aquat. Ecosyst.

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“…Low contribution may be associated with relatively fast moving water and lack of major dams/reservoirs along the mainstem rivers. Discerning live from dead benthic diatoms in each assemblage may help identify resident from washed-in and dead benthic taxa in an assemblage (Gillett et al, 2009). Diatom analysis focusing on the live portion of the benthic assemblage may better elucidate the relationships between diatom assemblages and environmental conditions in large river littoral zones.…”

Section: Nitzschiamentioning

confidence: 99%

Non-wadeable river bioassessment: spatial variation of benthic diatom assemblages in Pacific Northwest rivers, USA

et al. 2012

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Current bioassessment efforts are focused on small wadeable streams, at least partly because assessing ecological conditions in non-wadeable large rivers poses many additional challenges. In this study, we sampled 20 sites in each of seven large rivers in the Pacific Northwest, USA, to characterize variation of benthic diatom assemblages among and within rivers relative to environmental conditions. Analysis of similarity (ANOSIM) indicated that diatom assemblages were significantly different among all the seven rivers draining different ecoregions. Longitudinal patterns in diatom assemblages showed river-specific features. Bray-Curtis dissimilarity index values did not increase as a function of spatial distance among the sampled reaches within any river but the Malheur. Standardized Mantel r of association between assemblage similarity and spatial distance among sites ranged from a high of 0.69 (Malheur) to a low of 0.18 (Chehalis). In the Malheur River, % monoraphids, nitrogen-tolerant taxa, and beta-mesosaprobous taxa all decreased longitudinally while % motile taxa, especially Nitzschia, showed an opposite trend, reflecting a strong in-stream water quality gradient. Similar longitudinal trends in water quality were observed in other rivers but benthic diatom assemblages showed either weak response patterns or no patterns. Our study indicated that benthic diatom assemblages can clearly reflect among-river factors. The relationships between benthic diatom assemblages and water quality within each river may depend on the strength of the water quality gradients, interactive effects of water quality and habitat conditions, and diatom sampling design.

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“…Boxes are inter-quartile ranges, lines are medians, whiskers indicate 10th and 90th percentiles, and circles are outliers. P-values are from two-sample t-tests for significant differences between impairment categories conducted separately on EHS and MHS diatoms in riffle and depositional habitats have been debated (Cox, 1998;Round, 1998;Gillett et al, 2009). However, research has shown that relationships of diatom assemblages with environmental gradients are similar regardless of correcting diatom counts for the number of dead diatoms (Gillett et al, 2009).…”

Section: Similarity Between Mhs and Ehsmentioning

confidence: 99%

“…P-values are from two-sample t-tests for significant differences between impairment categories conducted separately on EHS and MHS diatoms in riffle and depositional habitats have been debated (Cox, 1998;Round, 1998;Gillett et al, 2009). However, research has shown that relationships of diatom assemblages with environmental gradients are similar regardless of correcting diatom counts for the number of dead diatoms (Gillett et al, 2009). Also, some research has shown that including dead diatoms in counts provides greater integration of the temporal and spatial variations in environmental variables (Stevenson & Pan, 1999).…”

Section: Similarity Between Mhs and Ehsmentioning

confidence: 99%

Using diatoms to assess human impacts on streams benefits from multiple-habitat sampling

Smucker

Vis

2010

Hydrobiologia

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Benthic diatoms are important indicators of human impacts on streams. Epilithic diatoms are collected most often for bioassessments, but potentially important ecological information from other habitats could be missed. Within our study region, substrata ranged from 100% rock to 100% sandy silt at 61 sites, leading us to question the appropriateness of sampling solely epilithic surfaces in riffles. We compared two protocols for collecting diatoms:(1) epilithic habitat samples (EHS) within riffles and (2) multi-habitat samples (MHS), which proportionately included different habitats (e.g., riffles and pools) and substrata (e.g., sand, silt, and rock). Three streams were not compared because rocks were absent. Nonmetric multidimensional scaling indicated that diatom communities from EHS and MHS responded similarly to alkalinity and agricultural gradients, and Procrustes analysis showed that ordinations were similar (P \ 0.01). Percent motile diatoms and metrics indicating high or low P and N from MHS showed stronger relationships with land use variables than those metrics from EHS. Bray-Curtis (BC) similarity between the protocols increased as diversity and richness decreased in MHS, as agricultural impacts increased, and as motile diatoms became more abundant in EHS, which likely indicated greater habitat homogeneity or an overriding effect of water chemistry. The two protocols classified 78% of sites concordantly as minimally impacted or impacted. Multi-habitat sampling is preferred where stream habitats vary greatly because it assessed land use impacts more effectively than EHS, while indicating water chemistry impacts as effectively. Multiple habitats also contained greater species diversity, which is important to documenting species distributions, and were always available for sampling, whereas epilithic habitats could be sparse or absent.

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Should only live diatoms be used in the bioassessment of small mountain streams?

Cited by 34 publications

References 25 publications

Suggestions for diatom-based monitoring in intermittent streams

Suggestions for diatom-based monitoring in intermittent streams

Non-wadeable river bioassessment: spatial variation of benthic diatom assemblages in Pacific Northwest rivers, USA

Using diatoms to assess human impacts on streams benefits from multiple-habitat sampling

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