Estuarine meiobenthic community diversity. Molecular and morphological analyses of estuarine meiobenthic community diversity

The assessment of benthic communities as biological quality elements in environmental quality monitoring traditionally requires time-consuming morphology-based identification techniques to identify areas of environmental impact. Herein, we describe the complementary use of morphology-based identification and DNA barcoding technology on environmental community samples to assess biodiversity and changes in the benthic meiofauna community in response to the salinity gradient and environmental quality, focussed on an Irish transitional estuarine water body. We show that morphology-based nematode species richness and DNA barcoding-derived nematode and whole benthic community richness decline from both freshwater and marine salinities to converge mid-estuary at a diversity minimum between 6 and 11 practical salinity units (psu). We also find that community composition and dominance change along the salinity gradient, distinguishing communities at low ( 18 psu) salinity zones, using both morphology-based species and molecular operational taxonomic unit (MOTU, 3% difference cut-off) community composition. DNA barcoding is sufficiently accurate to be advocated as a viable alternative to morphology-based identification studies, offering additional insight into ecosystem food webs and the identification of recognised indicator species.