Interactions between nematode biodiversity and anthropogenic disturbances on European sandy beaches (poster)

The European coastline consists for more than 30% of sandy beaches. In spite of their rather barren and arid view, these European coasts harbour a highly diverse fauna and flora and some of them are even highly productive. In contrast to tropical sandy beaches little is known about the structural and functional diversity of the different benthic components. This project firstly aims to get an idea about the structural and functional diversity of meiobenthos (all Metazoans between 1mm and 38µm), emphasizing on free-living marine nematodes, of three European sandy beaches (i.e. Belgium, Poland and Italy).European sandy beaches are under strong anthropogenic pressure (e.g. pollution, eutrofication, coastal fisheries and tourism), which has substantial impact on the interstitial life and functioning of the sandy beach ecosystem. Nematodes are very suitable for monitoring and will be used in the second part of this study to compare diversity and productivity between ‘disturbed’ and ‘undisturbed’ sandy beaches of three European coasts. Finally, indicator species will be identified based on their occurrence in disturbed sediments. Those indicator species could be used in further investigation as a tool for measuring disturbance of sandy sediments and could also be useful in coastal conservation. In order to document the structural and functional diversity of meiobenthos of the above-mentioned European sandy beaches, quantitative samples along transects from the upper to the lower beach are collected at the end of the touristic season. Meiobenthic communities will be followed during a one year cycle by means of monthly sampling campaigns along the same transect between mean high and low water level on both disturbed and undisturbed parts of the beaches. Meiobenthos will be processed and determined by standard procedures and further analysed by means of statistical and multivariate techniques. Only nematodes will be enumerated and analysed at species level. In addition, productivity of nematodes will be calculated.Some field experiments to investigate effect of disturbance on sediment will be set up in order to monitor the recolonization of pristine beaches after different degrees of disturbance

Nematode diversity and zonation patterns on sandy beaches

The European coastline consists for more than 30 % of sandy beaches. In spite of their rather barren and desert-like apperance, these European coasts harbour a highly diverse fauna and flora and some of them are even highly productive. On the other hand these beaches are subjected to strong anthropogenic pressure (e.g. pollution, eutrophication, coastal fisheries and tourism), which has substantial impact on the interstitial life and functioning of the sandy beach ecosystem. In contrast to the well-documented tropical sandy beaches, little is known about the structural and functional diversity of the different benthic components. This study aims to get an idea about the structural and functional diversity of meiobenthos (all Metazoans between 1 mm and 38 µm), emphasizing on free-living marine nematodes, of three European sandy beaches (i.e. Belgium, Poland and Italy). Nematodes are very suitable for monitoring and will be used in the second part of this study to compare and evaluate the diversity and productivity between ‘disturbed’ and ‘undisturbed’ sandy beaches. In order to document the structural and functional diversity of the meiobenthos of the above-mentioned European sandy beaches, quantitative samples along transects have been collected on both disturbed and undisturbed parts of the beaches. Meiobenthos was processed and identified by standard procedures and further analysed by means of statistical and multivariate techniques. Only nematodes have been analysed at species level. 12 different meiofaunal and around 150 species of free-living marine nematodes in total have been recognized on these beaches. Nematodes dominated almost all sampling stations. Among the free-living marine nematodes several new species have been found, indicating the very poor knowledge of the European sandy beach nematofauna. The nematode biodiversity was highest on the Belgian beaches (ca 90 species), followed by the Italian beaches (ca 40 species) and Polish beaches (ca 20 species). Nematode zonation patterns have been detected as well

Meiofauna as descriptor of tourism-induced changes at sandy beaches

Tourism has long been considered as a ‘clean industry’ with almost no negative effects on the environment. This study demonstrated, in two different coastal systems (Mediterranean and Baltic), that tourism related activities are particularly affecting the sandy beach meio- and nematofauna in the upper beach zone, the specific ecotone in which many meiofauna species from both the marine and the terrestrial environment congregate. Tourist upper beaches are characterized by a lower % total organic matter (%TOM), lower densities, lower diversities (absence of Insecta, Harpacticoida, Oligochaeta, terrestrial nematodes and marine Ironidae nematodes) and higher community stress compared to nearby non-tourist locations. The %TOM was found to be the single most important factor for the observed differences in meiofauna assemblage structure at tourist versus non-tourist beaches in both the Mediterranean and the Baltic region. The free-living nematode assemblages from tourist upper zones depart significantly from expectations based on random selections from the regional nematode species pool. Furthermore upper zone assemblages are characterised by a low species diversity consisting of taxonomically closely related nematode species with r-strategist features. Generally, faunal differences between tourist and non-tourist beaches are decreasing towards the lower beach zones

Revealing species assembly rules in nematode communities

Species assemblages are not randomly assembled from a local species pool; they often show segregated or aggregated distribution patterns. These patterns may be attributed to both biotic and abiotic factors. On a large scale abiotic factors may be important, while on a smaller scale other factors such as species interactions may become essential. Here we will focus on small-scale patterns in nematode communities. Species patterns are generally revealed by null models based on presence/absence data. Since there is an increasing chance of falsely rejecting the null hypothesis of a random assembled community with increasing matrix size, we used an algorithm generating independent null matrices and applied a large number of swap attempts to build a null matrix. Moreover, we applied an additional test to reveal the susceptibility of the analyses of checker and the C-, T- and Vscore to a Type I error for randomised data. To minimise the influence of the abiotic environment, we restricted the swapping algorithm of the null model to the replicate samples of one sampling event. Since stronger species interactions are expected for species of the same functional type, the nematode data was split according to the four feeding types defined by Wieser (1953). Our data indicate that species tend to aggregate and co-occur more often in some replicate samples than would be expected from a random species distribution of the local species pool. This is in accordance with the patchy distribution patterns known for nematode species. These aggregated patterns are also found for the different feeding types. The factors causing these aggregated patterns cannot be established since they are not included in the data, but the data do indicate that competitive exclusion is unlikely at the scale of a sample core