Can dispersions be used for discriminating water quality status in coastal ecosystems? A case study on biofilm-dwelling microbial eukaryotes

Highlights

• Dispersions of biofilm-dwelling protist communities were driven mainly by species composition.

• Heterogeneity of community pattern was significantly related to the changes of environment.

• Dispersion measures presented a close linear relationship with the traditional β-diversity index.

• β-diversity measures were remarkably related to the nutrient ammonium nitrogen and DO.

• Multivariate dispersions may be used as a robust bioindicator of water quality status.

Abstract

Multivariate dispersions are an effective ecological indicator to evaluate the environmental heterogeneity and human disturbance in global ecological research. To explore the feasibility of the dispersions for assessing water quality status, a dataset of the biofilm-dwelling microbial eukaryote communities was studied in coastal waters of the Yellow Sea, northern China at two numerical resolutions. The community dispersion patterns represented a significant variability in both community structure and species composition in response to environmental heterogeneity. Multivariate approaches revealed that the species composition was the primary contributor to the community dispersion. Mantel analysis showed that the spatial variations in both community structure and species composition were significantly correlated with the changes of the nutrients, pH, dissolved oxygen (DO) and chemical oxygen demand (COD). The dispersion measures at both numerical resolutions were found to be remarkably related to the nutrient ammonium nitrogen and DO. Thus, we suggest that multivariate dispersions of the microbial eukaryote communities may be used as a potential bioindicator of water quality status in marine ecosystems.

Introduction

Biofilm-dwelling microbial eukaryotes are the primary components of a biofilm or microperiphyton communities, and employ a vital role in the functioning of microbial food webs in aquatic ecosystems (Gold et al., 2002, Norf et al., 2009, Risse-Buhl and Küsel, 2009, Xu et al., 2012). Phototrophic microalgae (mainly benthic diatoms) devote the primary production (Xu et al., 2008, Debenest et al., 2009, Duong et al., 2010, Xu et al., 2012), whereas the heterotrophic protozoa act as variety of trophic-functional consumers, such as bacterivores, algivores, raptors and non-selectives, and transfer the flux of both elements and energy from pico- and nano-plankton to benthos (Fischer et al., 2002, Kathol et al., 2009, Norf et al., 2009, Xu et al., 2011, Xu et al., 2014a). Both structural and functional variations in the microbial eukaryote communities may significantly influence the ecological equilibrium of the aquatic food web, especially the community structures of metazoa (Patterson et al., 1989, Norf et al., 2009, Xu et al., 2012, Xu et al., 2014a). Otherwise, microbial eukaryotes play an important function in maintaining and improving water quality due to their high tolerance to the extreme environmental conditions and inhabit biotopes compared to metazoa (Patterson et al., 1989, Coppellotti and Matarazzo, 2000, Xu et al., 2008). Furthermore, with their short generation times, sensitivity to environmental changes, they have widely been used as useful bioindicators of water quality in aquatic biotopes (Khatoon et al., 2007, Dorigo et al., 2009, Dorigo et al., 2010, Morin et al., 2010, Xu et al., 2012, Xu et al., 2014a, Xu et al., 2014b, Zhong et al., 2014).

As a broad β-diversity, multivariate dispersion is a robust ecological measure to discriminate the heterogeneity within groups of communities in response to the environmental changes (Anderson et al., 2006, Anderson et al., 2008). Compared to the univariate β-diversity index, the dispersion analysis is performed in a multivariate way, and has a capacity of signifying the differences among samples. Several studies on macrobenthic assemblages have demonstrated that the multivariate dispersion is a robust ecological indicator of environmental heterogeneity (Ellingsen and Gray, 2002, Anderson et al., 2006, Xu et al., 2015). However, with regards the feasibility of multivariate dispersion for bioassessment of water quality status using biofilm-dwelling microbial eukaryotes in aquatic ecosystems, little information was known.

In our study, the multivariate dispersions of the biofilm-dwelling microbial eukaryote communities and their relationships to environmental changes were investigated based on a dataset from a coastal area within a gradient of environmental contamination of the Yellow Sea, northern China. The purpose of this study was focused on: (1) exploring the dispersions of the microbial assemblages in the areas at two numerical (species abundance and occurrence) resolutions, and (2) determining the feasibility of multivariate dispersions for assessing water quality status in marine ecosystems, using biofilm-dwelling microbial eukaryotes.