Conflicts of interests between economic and nature conservation stakeholders are increasingly common in coastal seas, inducing a growing need for evidence-based marine spatial planning. This requires accurate, high-resolution habitat maps showing the spatial distribution of benthic assemblages and enabling intersections of habitats and anthropogenic activities. However, such detailed maps are often not available because relevant biological data are scarce or poorly integrated. Instead, physiotope maps, solely based on abiotic variables, are now often used in marine spatial planning. Here, we investigated how pointwise, relatively sparse biological data can be integrated with gridded, high-resolution environmental data into informative habitat maps, using the intensively used southern North Sea as a case-study. We first conducted hierarchical clustering to identify discrete biological assemblages for three faunal groups: demersal fish, epifauna, and endobenthos. Using Random Forest models with high-resolution abiotic predictors, we then interpolated the distribution of these assemblages to high resolution grids. Finally, we quantified different anthropogenic pressures for each habitat. Habitat maps comprised a different number of habitats between faunal groups (6, 13, and 10 for demersal fish, epifauna, and endobenthos respectively) but showed similar spatial patterns for each group. Several of these ‘fauna-inclusive’ habitats resembled physiotopes, but substantial differences were also observed, especially when few (6; demersal fish) or most (13; epifauna) physiotopes were delineated. Demersal fishing and offshore wind farms (OWFs) were clearly associated with specific habitats, resulting in unequal anthropogenic pressure between different habitats. Natura-2000 areas were not specifically associated with demersal fishing, but OWFs were situated mostly inside these protected areas. We thus conclude that habitat maps derived from biological datasets that cover relevant faunal groups should be included more in ecology-inclusive marine spatial planning, instead of only using physiotope maps based on abiotic variables. This allows better balancing of nature conservation and socio-economic interests in continental shelf seas.

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The sandy seabed of shallow coastal shelf seas displays morphological patterns of various dimensions. The seabed also harbors a rich ecosystem. Increasing pressure from human-induced disturbances necessitates further study on drivers of benthic community distributions over morphological patterns. Moreover, a greater understanding of the sand ripple distribution over tidal sand waves may improve morphological model predictions. Here we analyzed the biotic abundance and ripple morphology in sand wave troughs and crests using video transects. We found that both the epibenthos and endobenthos are significantly more abundant in sand wave troughs, where ripples are less abundant and more irregularly shaped. Finally, we show that camera systems are relatively quick and effective tools to study biotic spatial patterns in relation to seabed morphology.

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We present a quick assessment method using an idealized one-dimensional linear model to explore the influence of multiple retention basins, whose construction is proposed as a measure to reduce tidal amplitudes in estuaries/tidal channels. To this end, we have developed a process-based network model for the cross-sectionally averaged water motion, including width and depth convergence (thus extending earlier studies), bottom friction, radiation damping and allowing for multiple basins at arbitrary locations. For frictionally dominated tidal channels, model results show that construction of a retention basin generally leads to a reduction of the tidal amplitude at the channel head. This reduction is stronger for larger basins and for basins closer to the landward side. Strikingly, for weak to moderate friction, a basin situated sufficiently close to the seaward side may trigger the opposite and undesired effect (tidal amplification) and nonlinear interaction among basins may occur. The model is then applied to the Ems estuary (Germany), where the construction of nine designated retention basins is currently under consideration. For parameter values representing the present-day Ems situation, constructing all nine proposed basins is estimated to result in a tidal amplitude reduction of 0.87 m (from 1.51 m to 0.64 m). A systematic model analysis of all 29 = 512 combinations shows that 86% of this reduction can be achieved by selecting only four of these basins. Importantly, shifts in the frictional regime, as experienced by the Ems in the past, may drastically change the effect of retention basins. Even though the efficiency and flexibility of this exploratory model allow for extensive sensitivity studies, we recommend to combine it with a detailed model, for the purpose of both efficiency and accuracy@en