DOI: 10.5061/dryad.vt4b8gtq8
title: Data from: Restoring marine ecosystems: spatial reef configuration triggers taxon-specific responses among early colonizers

description: 1. The longstanding debate in conservation biology on the importance of
 single large or several small (SLOSS) habitats for preserving biodiversity
 remains highly relevant, given the ongoing degradation and loss of natural
 habitats worldwide. Restoration efforts are often constrained by limited
 resources, and insights from SLOSS studies therefore have important
 implications if restoration efforts can be optimized by manipulating the
 spatial configuration of restored habitats. Yet, the relevance of SLOSS
 for habitat restoration remains largely unexplored. 2. Here, we report the
 effects of spatial reef configuration on early colonization of marine
 organisms after restoring boulder reef habitats. Reefs were restored in
 single large (SL) and several small (SS) designs in the western Baltic
 Sea, where century-long boulder extraction has severely degraded large
 reef areas and likely exacerbated regional declines in commercially
 important gadoids (Gadidae spp.). We sampled the field sites using remote
 underwater video systems in a before-after control-impact (BACI) design
 and obtained probabilistic inferences on restoration and SLOSS effects
 from Bayesian hierarchical models. 3. Probabilities of a positive
 restoration effect were high (&gt;95%) for gadoids, labrids and
 demersal gobies, moderate (60-75%) for species richness and sand gobies,
 and low (&lt;5%) for flatfish abundance. Notably, gadoid abundance
 increased 60-fold and 129-fold on average at SL and SS, respectively. The
 species composition at restored reefs deviated from control sites, mainly
 driven by large-bodied piscivores. 4. Spatial reef configuration had the
 strongest effect on small-bodied mesopredators, including gobies, which
 were more abundant and driving a distinct species assemblage at SS. In
 addition to providing suitable conditions for reef species, results
 suggest that SS can also benefit soft-bottom taxa, possibly through a
 dispersed predator-mediated effect relative to SL.
     5. Synthesis and applications. This study
 demonstrates that boulder reef restoration can strongly promote the
 abundance of exploited gadoids and is therefore a promising management
 tool to support top-down controls by predatory fishes in degraded marine
 systems. The higher abundance of mesopredators at SS reefs suggests that
 SLOSS could have long-term implications for trophic structure and
 resilience of restored habitats, and should therefore become an important
 facet within restoration strategies.
        
description: The data used in this study were collected with use of remote
 underwater video systems (RUVS). Specifically, these systems included a
 mono-camera setup (using GoPro Hero 3, 3+ and 4) attached to a timer (Time
 Lapse Intervalometer or BlinkX; Cam Do Solutions; https://cam-do.com) to
 trigger the camera to record two-minute hourly video clips. Video clips
 were analyzed in VLC Media Player (https://videolan.org) with adjusted
 video filters to attain natural coloration and increased brightness if
 necessary (mostly for twilight recordings). No artificial light sources
 were used with the video systems and all night sequences were hence
 discarded.  
description: The Bayesian hierarchical models used in the univariate part
 of this study were run in parallel on high-performance computing (HPC)
 servers, with an average model convergence time of 2-3 days per model. Due
 to the high computational demands associated with running MCMC using the
 Hamilton Monte Carlo (HMC) algorithm, we strongly recommend that users of
 our script and dataset similarly make use of HPC servers if
 available.