Thresholds of seascape fauna composition along gradients of human pressures and natural conditions to inform marine spatial planning

Knowledge about the cumulative impacts of anthropogenic activities and environmental conditions on marine ecosystems is incomplete and details are lacking. Compositional community changes can occur along gradients, and community data can be used to assess the state of community resilience against combined impacts of variables representing human pressures and environmental conditions. Here we use a machine learning approach, i.e., Gradient Forest, to identify explanatory variable thresholds and select relevant epibenthic fauna and demersal fish species, which can be used to inform an integrated management of multiple human pressures and conservation planning in the southern North Sea. We show that a broad selection of anthropogenic and environmental variables, such as natural disturbance of the seafloor and euphotic depth, determined community composition thresholds of 67 epibenthic fauna and 39 demersal fish species along environmental conditions and human pressure gradients in the southern North Sea between 2010 and 2020. This has the potential to inform resilience assessments under the Marine Strategy Framework Directive to promote and retain a good environmental status of marine ecosystems.

The umbrella value of caribou management strategies for biodiversity conservation in boreal forests under global change

Single-species conservation management is often proposed to preserve biodiversity in human-disturbed landscapes. How global change will impact the umbrella value of single-species management strategies remains an open question of critical conservation importance. We assessed the effectiveness of threatened boreal caribou as an umbrella for bird and beetle conservation under global change. We combined mechanistic, spatially explicit models of forest dynamics and predator-prey interactions to forecast the impact of management strategies on the survival of boreal caribou in boreal forest. We then used predictive models of species occupancy to characterize concurrent impacts on bird and beetle diversity. Landscapes were simulated based on three scenarios of climate change and four of forest management. We found that strategies that best mitigate human impact on boreal caribou were an effective umbrella for maintaining bird and beetle assemblages. While we detected a stronger effect of land-use change compared to climate change, the umbrella value of management strategies for caribou habitat conservation were still impacted by the severity of climate change. Our results showed an interplay among changes in forest attributes, boreal caribou mortality, as well as bird and beetle species assemblages. The conservation status of some species mandates the development of recovery strategies, highlighting the importance of our study which shows that single-species conservation can have important umbrella benefits despite global change.

Downslope migration of free-living corals (Scleractinia: Fungiidae) in typhoon-exposed reef habitats at Okinawa, Japan

Offshore Onna Village, Okinawa Island, Japan, there is a large and densely covered coral assemblage of free-living mushroom corals (Scleractinia: Fungiidae) on a reef slope at depths from 20 m to 32 m, covering an area of approximately 350 × 40 m². From previous research, it is known that migration distances of mushroom corals may depend on coral shapes, coral sizes, substrate, and bottom inclination. However, until now there have been no published examples of regular Fungiidae movement and behavior from typhoon-exposed coastlines, such as those in the western Pacific Ocean. Our surveys across three years offshore Onna Village show that mushroom corals always move in down-slope direction from shallow to deeper reef zones. The results indicated that mushroom corals migrated faster in autumn than in other seasons, and that oval-elongate fungiids, and particularly those with a smooth underside, migrated more quickly than species with other shapes. Surprisingly, we observed a negative relationship between the presence of typhoons and migration rates. We also observed active migration by fungiid individuals to escape situations in which they were threatened to become overgrown by Acropora corals, or when they needed to escape from burial underneath coral debris.

Effect of the Hebei Spirit oil spill on intertidal meiofaunal communities in Taean, Korea

In December 2007, approximately 10,900tons of oil from a crude carrier spread rapidly onto the coast of South Korea. We studied the effects of oil on meiofauna by comparing two contaminated intertidal sites with an uncontaminated site. During 2008-2009, the density of meiofauna fluctuated among the contaminated sites but did not vary by season. Seasonal changes in density were observed at contaminated sites 3years after the oil accident. Meiofauna appeared to be more sensitive to oil pollution stress at the more heavily contaminated site than at the less contaminated site. CLUSTER analysis showed that meiofauna communities in the 3years immediately following the accident significantly differed from those sampled later. A non-metric multidimensional scaling analysis showed that nematode species composition in the first month after the accident significantly differed from those sampled later. Long-term monitoring is needed to assess the effects of oil on the meiofaunal community.

An evaluation of randomization models for nested species subsets analysis

Randomization models, often termed "null" models, have been widely used since the 1970s in studies of species community and biogeographic patterns. More recently they have been used to test for nested species subset patterns (or nestedness) among assemblages of species occupying spatially subdivided habitats, such as island archipelagoes and terrestrial habitat patches. Nestedness occurs when the species occupying small or species-poor sites have a strong tendency to form proper subsets of richer species assemblages. In this paper, we examine the ability of several published simulation models to detect, in an unbiased way, nested subset patterns from a simple matrix of site-by-species presence-absence data. Each approach attempts to build in biological realism by following the assumption that the ecological processes that generated the patterns observed in nature would, if they could be repeated many times over using the same species and landscape configuration, produce islands with the same number of species and species present on the same number of islands as observed. In mathematical terms, the mean marginal totals (column and row sums) of many simulated matrices would match those of the observed matrix. Results of model simulations suggest that the true probability of a species occupying any given site cannot be estimated unambiguously. Nearly all of the models tested were shown to bias simulation matrices toward low levels of nestedness, increasing the probability of a Type I statistical error. Further, desired marginal totals could be obtained only through ad-hoc manipulation of the calculated probabilities. Paradoxically, when such results are achieved, the model is shown to have little statistical power to detect nestedness. This is because nestedness is determined largely by the marginal totals of the matrix themselves, as suggested earlier by Wright and Reeves. We conclude that at the present time, the best null model for nested subset patterns may be one based on equal probabilities of occurrence for all species. Examples of such models are readily available in the literature.