Invasive species can cause indirect effects on native biota by modifying parasite-host interactions and disease occurrence in native species. This study investigated the role of the invasive Pacific oyster (Crassostrea gigas) in potential spillover (co-introduced parasites infect native hosts) and spillback (native or established parasites infect invasive hosts and re-infect native hosts) scenarios of recently introduced (Mytilicola orientalis) and previously established (Mytilicola intestinalis) marine parasitic copepods in two regions in northern Europe, the Dutch Delta and the Wadden Sea. By examining 3416 individuals of 11 potential host species from sympatric host populations, we found that the recently introduced parasite M. orientalis does not only infect its principal host, the invasive Pacific oyster (prevalence at infected sites 2-43 %, mean intensity 4.1 ± 0.6 SE), but also native blue mussels (Mytilus edulis; 3-63 %, 2.1 ± 0.2), common cockles (Cerastoderma edule; 2-13 %, 1.2 ± 0.3) and Baltic tellins (Macoma balthica; 6-7 %, 1.0 ± 0), confirming a spillover effect. Spillback effects were not observed as the previously established M. intestinalis was exclusively found in blue mussels (prevalence at infected locations 3-72 %, mean intensity 2.4 ± 0.3 SE). The high frequency of M. orientalis spillover, in particular to native mussels, suggests that Pacific oysters may cause strong parasite-mediated indirect impacts on native bivalve populations.

. (2015). Changes over 50 years in fish fauna of a temperate coastal sea: Degradation of trophic structure and nursery function. Estuarine, Coastal and Shelf Science, 155,[156][157][158][159][160][161][162][163][164][165][166] ABSTRACTThe ongoing daily sampling programme of the fish fauna in the Dutch Wadden Sea

13Growth variability within individuals and among groups and locations and the 14 phenomenon of summer growth reduction has been described for juvenile flatfish in a 15 variety of European coastal areas whereby the underlying causes still remain elusive.

Estuarine food webs are generally considered to be supported by marine pelagic and benthic primary producers and by the import of dead organic matter from the open sea. Although estuaries receive considerable amounts of freshwater phytoplankton and organic compounds from adjacent rivers, the potential contribution of these living and dead matter to estuarine food webs is often assumed to be negligible and, therefore, not examined. Based on stable isotope analyses, we report the importance of freshwater suspended particulate organic matter (FW-SPOM) for fuelling estuarine food webs in comparison to estuarine SPOM and microphytobenthos. This previously neglected food source contributed 50–60% (annual average) of food intake of suspension-feeding bivalves such as cockles ( Cerastoderma edule ), mussels ( Mytilus edulis ) and Pacific oysters ( Magallana gigas ) at the Balgzand tidal flats, an estuarine site in the western Wadden Sea (12–32 psu). For these species, this proportion was particularly high in autumn during strong run-off of SPOM-rich freshwater, whilst estuarine SPOM (20%-25%) and microphytobenthos (15%-30%) were relatively important in summer when the freshwater run-off was very low. These findings have implications for our understanding of the trophic interactions within coastal food webs and for freshwater management of estuarine ecosystems.