%0 Journal Article %J Marine Ecology Progress Series %D 2020 %T Highly variable taxa-specific coral bleaching responses to thermal stresses %A McClanahan, T.R. %A Darling, E.S. %A Maina, J.M. %A Muthiga, NA %A D'agata, S. %A Leblond, J. %A Arthur, R. %A Jupiter, S.D. %A Wilson, S.K. %A Mangubhai, S. %A Ussi, A.M. %A Mireille M.M. Guillaume %A Humphries, A.T. %A Patankar, V. %A Shedrawi, G. %A Pagu, J. %A Grimsditch, G. %K acclimation %K Adaptation %K Climate Change %K community structure %K Geography %K Stress responses %X Complex histories of chronic and acute sea surface temperature (SST) stresses are expected to trigger taxon- and location-specific responses that will ultimately lead to novel coral communities. The 2016 El Niño-Southern Oscillation provided an opportunity to examine largescale and recent environmental histories on emerging patterns in 226 coral communities distributed across 12 countries from East Africa to Fiji. Six main coral communities were identified that largely varied across a gradient of Acropora to massive Porites dominance. Bleaching intensity was taxon-specific and was associated with complex interactions among the 20 environmental variables that we examined. Coral community structure was better aligned with the historical temperature patterns between 1985 and 2015 than the 2016 extreme temperature event. Additionally, bleaching responses observed during 2016 differed from historical reports during past warm years. Consequently, coral communities present in 2016 are likely to have been reorganized by both long-term community change and acclimation mechanisms. For example, less disturbed sites with cooler baseline temperatures, higher mean historical SST background variability, and infrequent extreme warm temperature stresses were associated with Acropora-dominated communities, while more disturbed sites with lower historical SST background variability and frequent acute warm stress were dominated by stress-resistant massive Porites corals. Overall, the combination of taxon-specific responses, community-level reorganization over time, geographic variation, and multiple environmental stressors suggest complex responses and a diversity of future coral communities that can help contextualize management priorities and activities. %B Marine Ecology Progress Series %V 648 %P 135 - 151 %8 27-08-2020 %G eng %U https://www.int-res.com/abstracts/meps/v648/p135-151/ %! Mar. Ecol. Prog. Ser. %R 10.3354/meps13402 %0 Journal Article %J Progress in Oceanography %D 2018 %T Plankton food-web functioning in anthropogenically impacted coastal waters (SW Mediterranean Sea): An ecological network analysis %A Meddeb, M. %A Grami, B. %A Chaalali, A. %A Haraldsson, M. %A Nathalie Niquil %A Pringault, O. %A Sakka Hlaili, A. %K Algae %K anthropogenic effect %K Anthropogenic impacts %K Anthropogenic pressures %K Bizerte %K Bizerte Bay %K Chemical analysis %K Chemical contamination %K coastal water %K community structure %K Ecological network analysis %K Ecology %K ecosystem function %K ecosystem modeling %K Ecosystems %K eutrophication %K food web %K Food webs %K Functional properties %K Inverse problems %K Lakes %K Linear inverse models %K Markov processes %K Mediterranean coastal waters %K Mediterranean ecosystem %K Mediterranean sea %K Monte Carlo methods %K network analysis %K Phytoplankton %K Plankton %K primary production %K Tunisia %K Zooplankton %X The study is the first attempt to (i) model spring food webs in three SW Mediterranean ecosystems which are under different anthropogenic pressures and (ii) to project the consequence of this stress on their function. Linear inverse models were built using the Monte Carlo method coupled with Markov Chains to characterize the food-web status of the Lagoon, the Channel (inshore waters under high eutrophication and chemical contamination) and the Bay of Bizerte (offshore waters under less anthropogenic pressure). Ecological network analysis was used for the description of structural and functional properties of each food web and for inter-ecosystem comparisons. Our results showed that more carbon was produced by phytoplankton in the inshore waters (966–1234 mg C m−2 d−1) compared to the Bay (727 mg C m−2 d−1). The total ecosystem carbon inputs into the three food webs was supported by high primary production, which was mainly due to >10 µm algae. However, the three carbon pathways were characterized by low detritivory and a high herbivory which was mainly assigned to protozooplankton. This latter was efficient in channelling biogenic carbon. In the Lagoon and the Channel, foods webs acted almost as a multivorous structure with a tendency towards herbivorous one, whereas in the Bay the herbivorous pathway was more dominant. Ecological indices revealed that the Lagoon and the Channel food webs/systems had high total system throughput and thus were more active than the Bay. The Bay food web, which had a high relative ascendency value, was more organized and specialized. This inter–ecosystem difference could be due to the varying levels of anthropogenic impact among sites. Indeed, the low value of Finn's cycling index indicated that the three systems are disturbed, but the Lagoon and the Channel, with low average path lengths, appeared to be more stressed, as both sites have undergone higher chemical pollution and nutrient loading. This study shows that ecosystem models combined with ecological indices provide a powerful approach to detect change in environmental status and anthropogenic impacts. © 2018 %B Progress in Oceanography %I Elsevier Ltd %V 162 %P 66-82 %G eng %U https://www.sciencedirect.com/science/article/abs/pii/S0079661117300782 %R 10.1016/j.pocean.2018.02.013 %0 Journal Article %J Journal of Biogeography %D 2017 %T Structural bias in aggregated species-level variables driven by repeated species co-occurrences: a pervasive problem in community and assemblage data %A Hawkins, Bradford A. %A Leroy, Boris %A Rodríguez, Miguel Á. %A Singer, Alexander %A Vilela, Bruno %A Villalobos, Fabricio %A Wang, Xiangping %A Zelený, David %K community structure %K community weighted means %K geographical ecology %K intrinsic variables %K spatial analysis %K species co-occurrence %K species composition %K species richness gradients %K trait analysis %X Aim Species attributes are often used to explain diversity patterns across assemblages/communities. However, repeated species co-occurrences can generate spatial pattern and strong statistical relationships between aggregated attributes and richness in the absence of biological information. Our aim is to increase awareness of this problem. Location North America. Methods We generated empirical species richness patterns using two data structures: (1) birds gridded from range maps and (2) tree communities from the US Forest Service's Forest Inventory and Analysis. We analysed richness using linear regression, regression trees, generalized additive models, geographically weighted regression and simultaneous autoregression, with ‘random intrinsic variables’ as predictors generated by assigning random numbers to species and calculating averages in assemblages. We then generated simulations in which species with cohesive or patchy distributions are placed with respect to the North American temperature gradient with or without a broad-scale richness gradient. Random intrinsic variables are again used as predictors of richness. Finally, we analysed one simulated scenario with random intrinsic variables as both response and predictor variables. Results The models of bird and tree richness often explained moderate to large proportions of the variance. Regression trees, geographically weighted regression and simultaneous autoregression were very sensitive to the problem; generalized additive models were moderately affected, as was multiple regression to a lesser extent. In the virtual data, the variance explained increased with increasing species co-occurrences, but neither range cohesion, a richness gradient nor spatial autocorrelation in predictors had major impacts on the variance explained. The problem persisted when the response variable was also a random intrinsic variable. Main conclusions Repeated species co-occurrences can generate strong spurious relationships between richness and aggregated species attributes. It is important to realize that models utilizing assemblage variables aggregated from species-level values, as well as maps illustrating their spatial patterns, cannot be taken at face value. %B Journal of Biogeography %8 02/2017 %G eng %U http://dx.doi.org/10.1111/jbi.12953 %R 10.1111/jbi.12953