Long-term change of meiofaunal species composition in a sandy beach, with description of 7 new species of Platyhelminthes

Abstract

Climate change and species introductions strongly changed macrobenthic community composition in the North Sea during past decades. To find out whether there was a similar change in meiofauna, I reexamined a semi-exposed sandy beach of the Island of Sylt that had been intensively studied between 1965 and 1975. These previous studies provide the baseline for temporal change. As before, the analysis of species composition focused on Platyhelminthes. Minor change in the physical properties of the beach during the past decades was compensated for by including two adjoining beaches, one slightly more sheltered and the other slightly more exposed. In due consideration of somewhat differing sample size, platyhelminth species richness barely changed over the past 50 years, and the numerical dominant species were still the same. However, roughly 10% of the 220 species found during this study were not previously recorded from the Island of Sylt. Thirteen are new to science though unpublished records indicate that half of them already occurred previously. Seven species described from elsewhere were recorded for the first time in the Sylt area. Based on their known geographical range, none of these can be unambiguously assigned an immigrant or introduced species. I conclude that (1) the platyhelminth fauna displayed high temporal stability over the past 50 years, and (2) though this beach is among the best studied in the world, a rate of 10% new species indicates our knowledge on the diverse meiofauna is still relatively poor. Seven new species of Platyhelminthes are described and three re-described: Coelogynopora multispina n. sp., Pseudostomum gracilis Westblad 1955, Nesite ptychoperoides n. gen. n. sp., Haplovejdovskya scilliensis Faubel & Warwick 2005, Haloplanella magnarhabdita n. sp., Haloplanella spiralis n. sp., Moevenbergia oculifagi n. sp., Coronhelmis inaequalis n. sp., Proxenetes inflatus den Hartog 1966, and Diascorhynchus falconis n. sp.

Nourished, Exposed Beaches Exhibit Altered Sediment Structure and Meiofaunal Communities

“…Armonies [ 59 , 60 ] repeated sampling of historical studies to investigate changes in turbellarian assemblage structure over time for a stable intertidal beach and a dynamic tidal inlet. At the former site he found little evidence for change.…”

Analysing long-term change in small benthos: geomorphological dynamics affects method selection

“…Gnathorhynchus rostellatus indivisus n. ssp. is described in this study and two species were described in its 2018 predecessor [2]; their geographical distribution outside the Sylt area is unknown. Among the remaining five species recorded for the first time near Sylt, Utelga heinckei is well known from the island of Helgoland (some 50 km south of Sylt) while Cheliplana rubescens was described from the Mediterranean [13] but intermittently has also been found in Swedish waters [14]; their natural ranges seem to enclose the North Sea.…”

“…Where sound background data are available, the degree of change can be analysed by repetition of a previous study using the same methods, and sampling the same sites, which may be an efficient method to reduce random variability when temporal changes are the target [1]. This worked quite well in the analysis of temporal change in the small benthos of a semi-exposed tidal beach that had been morphologically stable over the past decades [2]. However, problems may arise where geomorphology is highly dynamic.…”

First discovery – and a new species – of Coelogynopora (Platyhelminthes, Proseriata) in the Southern Hemisphere

“…Interstitial (meiobenthic) worms are valuable as the object of ecological, systematic, and biogeographical studies because of their low dispersal ability and strict habitat requirements (Curini-Galletti et al 2012; Armonies 2017). They have also turned out to be helpful in more applied studies, such as the environmental biomonitoring of the direct and indirect impact of human activities (Schratzberger 2012; Armonies 2017;Martínez et al 2020).…”

“…Coelogynoporidae (Platyhelminthes) includes comparatively large and slender Proseriata, usually occurring in shallow benthic environments. Among the representatives of the family, Coelogynopora Steinböck, 1924 is the most frequently reported genus and the one with the highest number of species (Jouk et al 2007(Jouk et al , 2019; Armonies 2017Armonies , 2018. The highest diversity in the genus is reached at high latitudes, and the 38 previously known, valid species have a strictly Northern Hemispheric distribution (for recent examples, see Curini-Galletti et al 2010; Armonies 2017Armonies , 2018Jouk et al 2019).…”