A comparison of physical disturbance and pollution stressors in sandy beaches using nematode functional biological traits

Abstract

AbstractNematode functional traits and community structure approaches are receiving attention and being debated regarding the similarity in gained information. This work applied two nematode methods (i.e. functional traits, community structure) and sex ratios to investigate sandy beaches experiencing physical disturbances and anthropogenic stressors along the Alexandrian coast of Egypt. It is the first study to identify the Egyptian marine benthic nematodes to genus level yielding fourteen genera. This study addressed the following questions. (A) Which analyses of functional traits, community structure, or sex ratio could distinguish beaches experiencing natural disturbances from anthropogenic stressors? (B) What are the driving forces that govern nematode assemblages? Designated beaches were high pollution and energy (HPHE), high pollution but low energy (HPLE), and clean high energy (CHE). The study was conducted in March 2014, applying a stratified random sampling design and advanced multivariate analyses. Results revealed significant discrimination among and within beaches based on functional traits, community structure, and sex ratio. The functional traits (FBM) grouped data into two main groupings, predators and scavengers. Predators and cylindrical shape-tail types were found in high salinity moderately-sorted fine-grained sand dominant at HPHE and CHE. Scavengers and a variety of tail-shape types inhabited low saline water with well-sorted coarse sediment at HPLE. The community structure (CSM) revealed three groupings, as each beach had a specific assemblage based on its response to the measured physiochemical factors (salinity, pH, and temperature). Three genera were responsible for the high contribution across each beach Graphonema sp (HPHE), Enoplolaimus sp. (HPLE), and Oncholaimus sp. (CHE), as well as the co-sharing of Axnolaimus sp at HPLE. However, Axnolaimus sp and Oncholaimus sp showed the highest dissimilarity among beaches. The contribution of the measured factors was 53.8% (FBM) and 35.7% (CSM). Trophic guilds were anthropogenic stressors dependent and tail-shape type physically disturbing-related. However, nematode genera were species-specific to habitat type. The sex ratio was male-biased, and Juvenile-stages seemed to be temperature-dependent. The dissimilarity in the functional trait and community structure data recommend their application in biomonitoring and coastal restoration programs.