Contribution of microspatial factors to benthic diatom communities

Abstract

Spatial factors can play important and potentially confounding roles governing the presence, the absence, and the abundance of the diatom species and consequently influence the diatom-based bioassessment. To examine how spatial factors affect diatom community and biomonitoring, diatom community was sampled in three catchments with similar river length and watershed area across a large spatial scale along the Yangtze River, China. Redundancy analysis (RDA) showed that patterns of diatom distribution could be attributed not only to environmental variables (e.g., NO 3 -N, TN, WT, and COD), but also to spatial factors (e.g., elevation, latitude, and longitude). Partial RDAs partitioned the total variance of diatom data explained (64.7%) into three parts: pure spatial variables contributed the highest proportion (19.8%), followed by pure environmental variables (5.4%), and the shared effects by environmental and spatial sets explained a large proportion of diatom variance (39.5%). Recognizing the potential influences of spatial factors, further accumulations of diatom data within different regions would allow for the development of better diatom-based monitoring methods for watershed diagnosis and management.

Hydrological and environmental variables outperform spatial factors in structuring species, trait composition, and beta diversity of pelagic algae

“…In comparison with a single catchment of this study, the previous research compared the trait and species composition at a global scale (Soininen et al., ). Generally, for species distribution, the importance of spatial effects increased with geographical distance as dispersal limitation, and at large scales, spatial effects might outperform local environmental effects (Heino et al., ; Wu et al., ). Therefore, further comparisons between trait and species composition in relation to different factors at multispatial scales are greatly needed.…”

“…The relationships between river algae and abiotic factors have been studied with a long history. Nevertheless, previous studies and biomonitoring campaigns focused mostly on local environmental variables such as nutrients (Kelly & Whitton, ; Lange, Liess, Piggott, Townsend, & Matthaei, ), pH, temperature (Çelekli, Öztürk, & Kapı, ; Wu, Schmalz, & Fohrer, ), and recently also spatial factors (Heino & MykrÄ, ; Rezende, Santos, Henke‐Oliveira, & Gonçalves, ; Tang, Niu, & Dudgeon, ; Tang, Wu, Li, Fu, & Cai, ; Wu, Cai, & Fohrer, ). By comparison, little attention has been paid to hydrological factors such as flow regime (Qu, Wu, Guse, & Fohrer, ), although many studies have shown that riverine algal communities are linked to flow velocity and discharge (Biggs, Smith, & Duncan, ; Jowett & Biggs, ; Munn, Frey, & Tesoriero, ; Riseng, Wiley, & Stevenson, ; Wu et al., ) and catchment wetness (Wu et al., ).…”

“…Dispersal limitation creates spatial structure in assemblage composition because the probability of successful movement between locations is negatively related to the geographical distance between them. Spatial variables such as altitude or geographical location can play important and confounding roles determining the presence, absence, and abundance of the algal species and consequently influence the algae‐based bioassessment (Wu et al., ). One previous view of algae distributions was that they were ubiquitous and could disperse everywhere due to the immense population sizes, especially over a long time period (Fenchel & Finlay, ).…”

Importance of sampling frequency when collecting diatoms

“…The lack of consensus between studies might be due to the fact that the community-environment relationship is dependent on spatial scale. For example, studies at large scale (e.g., national scale) often found that the geographical topography (e.g., altitude, latitude, longitude) and climate were the dominant factors regulating diatom variation11272939. In contrast, at small scales the main regulating factors have been shown to be typically hydrological factors (e.g., discharge), habitat (e.g., substrate composition, sediment input and transport), water quality (e.g., nutrient, dissolved oxygen) as well as bio-interaction (e.g., grazing, competition, parasitism)2732.…”

“…As diatoms strongly respond to environmental changes23456, they are increasingly being employed as bio-indicators to assess ecological conditions in lentic and lotic ecosystems around the world789. Diatoms are a key component of riverine algae and are often the most important primary producers of stream ecosystems46101112. They are preferred as bio-indicators for a range of reasons besides their sensitivity to subtle changes in environmental conditions due to their short life cycle2.…”