settlement of shore crab Carcinus maenas on a mesotidal open habitat as a function of transport mechanisms

Abstract

We evaluated the patterns of larval settlement of Carcinus maenas on natural substratum and its relationships with forcing factors related to larval transport mechanisms. Settlement was estimated as colonisation of traps containing defaunated substratum. Traps were deployed at low tide for 24 to 26 h, in the intertidal of the island of Helgoland (North Sea, German Bight), every day dur- rates peaked mainly at, or 1 to 3 d after, spring tide; periods of low colonisation were short, except at the end of the settlement season. According to an existing 2-step model and to local movement of megalopae, colonisation patterns in the intertidal may reflect transport processes: (1) settlement rates on Helgoland are primarily affected by wind-driven currents: SW winds transport larvae out of Helgoland waters, leading to low settlement rates, while other wind regimes transport them towards Helgoland. In the absence of strong SW winds, peaks of settlement at or after spring tide suggest (2) selective tidal stream transport or some form of tidally mediated flow. The absence of SW winds leads to a higher influence of local movement of megalopae, as the number of larvae reaching the benthic habitat is high. In consequence, colonisation of natural substratum may reflect larval transport processes and local movement of larvae in C. maenas and other invertebrates with mobile benthic stages.

Supply of crab larvae to an estuary in the eastern Atlantic upwelling system exhibits predictable and haphazard variation at different temporal scales

“…During summer, the influence of the WIBP is reduced, but the response of the coastal ocean to upwelling winds is asymmetrical in terms of along-shore and vertical components of circulation, and eddy formation still occurs as a result of the cross-shelf displacement of the IPC with wind events of variable intensity and duration. These mechanisms may be at the base of the complex relationships between ocean circulation and supply events that we detected in the present study, and that are characteristic features of recruitment patterns in many marine populations (Jones & Epifanio 1995, van Montfrans et al 1995, Roughgarden & Smith 1996, Wing et al 2003, Shanks 2006, Giménez & Dick 2007, Siegel et al 2008. The idiosyncratic nature of many of the supply events may also be connected with spatial and temporal differences in larval production, as well as with the length of our study.…”

“…Only a few studies have collected these types of data (e.g. Goodrich et al 1989, van Montfrans et al 1990, 1995, Jones & Epifanio 1995, Wing et al 2003, Giménez & Dick 2007, Roegner et al 2007.…”

Habitat-specific size structure variations in periwinkle populations (Littorina littorea) caused by biotic factors

“…Both Sylt and Helgoland are located within the same water body. Their proximity is less than 100 km and they are linked via water currents that allow the exchange of larvae of benthic organisms (Giménez and Dick 2007). This indicates that a genetic exchange between both periwinkle populations is very likely.…”

“…1). Both sites are located in the south-eastern North Sea and linked by currents enabling exchange of pelagic larvae of benthic organisms (Giménez and Dick 2007). They represent fundamentally diVerent environments with respect to abiotic and biotic conditions.…”

German Bight residual current variability on a daily basis: principal components of multi-decadal barotropic simulations

“…Oliver et al (2015) proposed the use of multi-decadal meteorological reanalyses for a reconstruction of variations of larval connectivity patterns on the US Pacific coast. Wind-driven currents were also found to impact larval settlement rates at Helgoland (Giménez and Dick 2007). Model simulations are also useful for a better interpretation of environmental data collected during large field campaigns (e.g.…”