Marine turf of an invasive alga expels lugworms from the lower shore

Bare sandy flats at and below low tide level of the Wadden Sea (eastern North Sea, European Atlantic) were observed in 2020 to have been invaded by an introduced grass-like alga, Vaucheria cf. velutina (Xanthophyceae). A dense algal turf accumulated and stabilized mud, where resident seniors of the lugworm Arenicola marina had reworked rippled sand. Algae and worms were incompatible. Initially, rising patches with algal turf alternated with bare pits where lugworms crowded. Their bioturbation inhibited young algae, while the felt of established algal rhizoids clogged feeding funnels of worm bur- rows. Eventually, a mosaic pattern of competitors gave way to a coherent algal turf without lugworms. Concomitantly, a rich small-sized benthic fauna took advantage of the novel algal turf. This exotic Vaucheria may have the potential for drastically altering the ecological web at the lower shore

Significant predation on micro- and macrobenthos by the crab Carcinus maenas L. in the Wadden Sea

The predatory role of juvenile and adult shore crabs, Carcinus maenas L., an tidal flats in the wadden sea near the North Sea island of Sylt has been evaluated with field enclosures. Early benthic stages (2-4 mm carapace width) prey heavily an microfauna (Nematoda, Turbellaria, Ostracoda) and particularly an juvenile macrofauna. When crabs grow up they gradually shift to larger prey and a bifurcation in prey selection occurs: males concentrate an molluscs while females feed preferentially an annelids. Annual consumption expressed as dry organic matter is estimated at 3.6 g·m 2 for O-group crabs and 1.3 g·m-2 for adult crabs. Carcinus maenas is expected to cause conspicious impact an zoobenthos in the wadden sea 1. by preying always an the most abundant species, 2. by increasing juvenile mortality of high-biomass macrofauna, 3. by being a predator of highly variable abundance between years

Psychometric precision in phenotype definition is a useful step in molecular genetic investigation of psychiatric disorders

Affective disorders are highly heritable, but few genetic risk variants have been consistently replicated in molecular genetic association studies. The common method of defining psychiatric phenotypes in molecular genetic research is either a summation of symptom scores or binary threshold score representing the risk of diagnosis. Psychometric latent variable methods can improve the precision of psychiatric phenotypes, especially when the data structure is not straightforward. Using data from the British 1946 birth cohort, we compared summary scores with psychometric modeling based on the General Health Questionnaire (GHQ-28) scale for affective symptoms in an association analysis of 27 candidate genes (249 single-nucleotide polymorphisms (SNPs)). The psychometric method utilized a bi-factor model that partitioned the phenotype variances into five orthogonal latent variable factors, in accordance with the multidimensional data structure of the GHQ-28 involving somatic, social, anxiety and depression domains. Results showed that, compared with the summation approach, the affective symptoms defined by the bi-factor psychometric model had a higher number of associated SNPs of larger effect sizes. These results suggest that psychometrically defined mental health phenotypes can reflect the dimensions of complex phenotypes better than summation scores, and therefore offer a useful approach in genetic association investigations

Spread of the invasive shell-boring annelid Polydora websteri (Polychaeta, Spionidae) into naturalised oyster reefs in the European Wadden Sea

With globally growing aquaculture activities, the co-introduction of parasites alongside large-scale movements of commercial species poses an increasing risk for marine ecosystems. Here, we present the first record of the shell-boring polychaete Polydora websteri Hartman in Loosanoff and Engle, 1943 in invasive Pacific oysters Crassostrea (Magallana) gigas (Thunberg, 1793) in the European Atlantic Ocean. In October 2014, mud blisters in the shells of wild Pacific oysters and specimens of a spionid polychaete were observed in close proximity to a commercial oyster farm at the island of Sylt (Germany) in the European Wadden Sea. Subsequent investigations indicated that these blisters only occurred near the farm and that no other mollusc species were affected. Morphological and molecular analysis identified the polychaete as Polydora websteri, a species that nowadays widely occurs around the globe, but likely is native to the Asian Pacific. Later sampling activities detected P. websteri also at other locations around Sylt as well as in the Dutch part of the Wadden Sea at the island of Texel. The number of polychaetes in the oysters was, however, relatively low and mostly below 10 individuals per oyster. Together, this evidence suggests that P. websteri is currently extending its range. As the introduction of P. websteri may have severe ecological and economic implications, this study aims to alert others to look for P. websteri at Western European coasts within farmed or wild Pacific oysters to further document its spread