Abstract
Nematodes are highly susceptible to environmental change and possess a wide array of morphological and functional characteristics for the assessment of the “Good Environmental Status”, within Marine Strategy Framework Directive. However, while the taxonomic sufficiency of nematodes in detecting spatial gradients and related ecological niche conditions is well recognized, very little is known about nematodes functional morphometric attributes in response to environmental drivers. To explore this knowledge gap, we aimed to assess the efficacy and efficiency of nematode morphometric attributes (length, width, length/width ratio, biomass) in detecting spatial patterns along a Portuguese estuarine gradient, and compare it with the taxonomic approach. We hypothesized that abundance data weighted by the morphometric attributes will have a higher explanatory power in detecting spatial patterns than using abundance of morphometric data alone.Based on the recent recommendations regarding the time and cost related efficacy of methods in biomonitoring and ecological assessments we also hypothesized that a reduced dataset based on the most common genera will suffice to capture the same distributional patterns displayed by the whole assemblage.Our results demonstrated that dataset solely based on genera abundances had consistently better explanatory power than combined datasets or morphometric datasets alone, however, combined dataset provided different spatial patterns and performed better at discriminating estuary areas. The main gradients described by the taxonomy-based dataset were related to the sediment particle size and water depth. Considering combined datasets, spatial discrimination was mainly driven by the variation in dissolved oxygen % saturation, pointing out to the importance of this variable in determining estuarine conditions substantial for nematodes morphometric distributional patterns.The same analysis repeated for the most frequent genera resulted in similar distributional patterns as for the whole assemblage dataset, clearly demonstrating that spatial estuarine gradients can be sufficiently described by using only the most frequent genera. Such information may substantially increase the efficiency of bio-assessment surveys by reducing the cost and work associated with identification and measurements of all of the individual nematode genera.
Highlights
Nematodes are key components of benthic ecosystems largely contributing to organic matter mineralization and energy provision to higher trophic levels (Coull, 1999; Schmid-Araya et al, 2016; Schratz berger and Ingels, 2018)
While the use of functional traits has demonstrated to be highly complemen tary in relation to taxonomy-based approaches (Alves et al, 2014; Franzo and Del Negro, 2019; Schratzberger et al, 2007), its combined usage to explain spatial patterns has never been addressed for meio fauna
Our initial hypothesis was that genera-based abundance dataset weighted by the morphometric traits would better reflect the assem blage distribution patterns along an estuarine gradient, when compared to the traditional taxonomic approach based solely on genera abun dances
Summary
Nematodes are key components of benthic ecosystems largely contributing to organic matter mineralization and energy provision to higher trophic levels (Coull, 1999; Schmid-Araya et al, 2016; Schratz berger and Ingels, 2018). These abundant metazoans are highly sus ceptible to environmental variation, which turns them efficient indicators of ecological change associated to natural or anthropogenically-induced disturbance (Hoss et al, 2011; Moreno et al, 2011; Semprucci and Balsamo, 2012; Semprucci et al, 2015). To date only few studies investigated the diversity-function relationship of nematodes in response to environmental drivers, leav ing this research field largely unexplored (Alves et al, 2014; Franzo et al, 2019; Franzo and Del Negro, 2019)
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