Climate is an important driver for stream diatom distributions

Abstract

Aim The species distributions of macroorganisms are widely studied, yet microbial distributions at species level remain poorly resolved. We explored the relative contributions of climatic and local environmental factors in explaining the distribution patterns of unicellular diatoms. Location A geographical gradient of c. 1200 km in Finland (60°–70° N). Methods We modelled the distributions of 157 diatom taxa sampled in 227 stream sites using climatic and local environmental predictors with four different modelling techniques: generalized linear models, generalized additive models, boosted regression trees and Random Forest. We used models with three separate sets of predictors: environment only, climate only and the full set of predictors. The model performances were evaluated using the area under the curve of a receiver operating characteristic plot and the true skill statistic values by a four‐fold cross‐validation approach. Results We found that the predictive performance of the full models was highest, indicating the importance of both the local environment and large‐scale climatic factors in diatom distribution patterns. However, climate‐only models outcompeted the environment‐only models in predicting diatom distributions. The explanatory variables had varying importance across species and growing degree days and precipitation had the highest relative importance in the full models. We also found that the predictability of the distributions varied greatly among species, but the differences among families were typically small. Main conclusions Our results suggest that at a broad geographical scale climate‐related factors are important determinants of diatom distributions and may be stronger drivers than local variables. The inclusion of both climatic and local environmental factors in species distribution modelling facilitates the understanding of the joint effects of these drivers on microorganisms in future conditions. From an applied perspective, our study demonstrated that species distribution models serve as an important tool in explaining and predicting microbial distributions.

Distribution patterns of epilithic diatoms along climatic, spatial and physicochemical variables in the Baltic Sea

“…In addition, we observed 18 common taxa that represented at least 1.0% of the identified diatom cells, and whose average abundance in sampling sites also exceeded 1.0% (Table 1) (and see Additional file 3: Supplementary material for the entire list of diatom species).Some of the species were common (>1.0% of cells) only in a particular region of the study area. For example, Navicula incertata was abundant only in the Gulf of Finland and the Archipelago Sea (sampling sites 2-13), while Bacillaria paxillifera (sampling sites [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], Diatoma monoliformis , Fragilaria fasciculata (2-21), Navicula margalithii (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19), Nitzschia frustulum , Nitzschia inconspicua and Nitzschia liebetruthii were abundant in all areas except the Bothnian Bay. Encyonema silesiacum (28)(29)(30)…”

“…The variation in diatom composition and species richness has been the subject of a large body of research both in marine and fresh waters [e.g. 2,3]. Traditionally, diatoms are thought to respond merely to local environmental variables, such as water chemistry, and in many cases, water chemistry variables, such as nutrients (nitrogen, phosphorus and silicon), pH, salinity and conductivity have been found to be the most important explanatory variables for diatom composition [e.g.…”

“…1, 2, 4]. However, the roles of climate and dispersal limitation have recently also been emphasized in explaining diatom distributions [3]. Organisms have distinct regional pools of species, and both climate and local physicochemical factors act as filters that determine the species composition in local communities [3,5].…”

“…However, the roles of climate and dispersal limitation have recently also been emphasized in explaining diatom distributions [3]. Organisms have distinct regional pools of species, and both climate and local physicochemical factors act as filters that determine the species composition in local communities [3,5]. The relative importance of climatic factors and local physicochemical factors varies with study scale: climatic factors may override the local physicochemical factors at continental scales, while at regional scales (100-3000 km) diatom communities are influenced by both climatic and local factors [5].…”

Effects of intensive agriculture in the structure and functioning of tropical headwater streams

“…Previous Benthic diatom functional characteristics were connected with seasonal/climate characteristics in tropical headwater streams. Analyzing the controlling factors of benthic diatom functional diversity, we found that functional richness and functional dispersion showed a positive relationship with water temperature, which is known to have exponential effects in nearly all rates of biological activity (BROWN et al, 2004) and has been observed in several organisms, including diatom distribution (ALLEN et al, 2002;PAJUNEN et al, 2015). Streamflow also demonstrated effects on functional richness, with higher values of functional indices on high flow periods.…”