Суперечності розвитку сучасного регіоналізму: чинники, детермінанти та механізми

A mass-balanced trophic model was developed for the coral reef lagoon of Uvea atoll (New Caledonia) using the Ecopath software. The model accounts for both pelagic and soft-bottom communities to describe the whole trophic structure and biomass flows in the shallowest part of the atoll lagoon. Phytoplankton production approximately equals the benthic primary production. Benthic biomass accounts for more than 80% of the total living biomass in the shallow lagoon. The benthic domain requires input of food from the pelagic system (mainly zooplankton) and from adjacent areas to sustain the biomass of predatory fishes. Predation pressure was found to be a major force structuring the food web, but it is also suggested that water circulation within the lagoon influences the amount of primary resources, such as plankton, benthic microphytes and detritus

Trophic signature of coral reef fish assemblages : towards a potential indicator of ecosystem disturbance

Face to the increasing anthropogenic disturbances that affect coral reef ecosystems, it becomes urgent to define appropriate ecological indicators for monitoring purposes. One useful approach is to search for a simplified description of the structure of biological communities that are highly diverse and complex on coral reefs. To this end, we propose to represent the trophic structure of coral reef fish assemblages by using fractional trophic levels assigned to each fish species. Fish abundance trophic spectra (i.e., the distributions of fish abundance per trophic level) were established for the fringing reefs of two bays located in the city of Noumea (New Caledonia). The comparison of these trophic spectra revealed a similar trophic structure in the two bays, in spite of contrasted levels of fish abundance due to habitat damages. The embayment degree was characterized by changes in the fish trophic structure, reflecting a decreasing influence of urban and industrial wastes discharged in the bottom of the bays. This case of study shows the interest of using fractional trophic levels for the description of highly diverse biological communities. The trophic level-based approach offers new prospects in the search for ecological indicators, by characterizing the structure of biological communities by trophic signatures which testify to the disturbance level affecting their environment

Scaling the Effects of Ocean Acidification on Coral Growth and Coral-Coral Competition on Coral Community Recovery

Ocean acidification (OA) is negatively affecting calcification in a wide variety of marine organisms. These effects are acute for many tropical scleractinian corals under short-term experimental conditions, but it is unclear how these effects interact with ecological processes, such as competition for space, to impact coral communities over multiple years. This study sought to test the use of individual-based models (IBMs) as a tool to scale up the effects of OA recorded in short-term studies to community-scale impacts, combining data from field surveys and mesocosm experiments to parameterize an IBM of coral community recovery on the fore reef of Moorea, French Polynesia. Focusing on the dominant coral genera from the fore reef, Pocillopora, Acropora, Montipora and Porites, model efficacy first was evaluated through the comparison of simulated and empirical dynamics from 2010-2016, when the reef was recovering from sequential acute disturbances (a crown-of-thorns seastar outbreak followed by a cyclone) that reduced coral cover to ~0% by 2010. The model then was used to evaluate how the effects of OA (1,100-1,200 µatm pCO2) on coral growth and competition among corals affected recovery rates (as assessed by changes in % cover y-1) of each coral population between 2010-2016. The model indicated that recovery rates for the fore reef community was halved by OA over 7 years, with cover increasing at 11% y-1 under ambient conditions and 4.8% y-1 under OA conditions. However, when OA was implemented to affect coral growth and not competition among corals, coral community recovery increased to 7.2% y-1, highlighting mechanisms other than growth suppression (i.e., competition), through which OA can impact recovery. Our study reveals the potential for IBMs to assess the impacts of OA on coral communities at temporal and spatial scales beyond the capabilities of experimental studies, but this potential will not be realized unless empirical analyses address a wider variety of response variables representing ecological, physiological and functional domains

Predicting Responses of Geo-ecological Carbonate Reef Systems to Climate Change: A Conceptual Model and Review

[Chapter Abstract] 230Coral reefs provide critical ecological and geomorphic (e.g. sediment production for reef-fronted shoreline maintenance) services, which interact in complex and dynamic ways. These services are under threat from climate change, requiring dynamic modelling approaches that predict how reef systems will respond to different future climate scenarios. Carbonate budgets, which estimate net reef calcium carbonate production, provide a comprehensive ‘snap-shot’ assessment of reef accretionary potential and reef stability. These budgets, however, were not intended to account for the full suite of processes that maintain coral reef services or to provide predictive capacity on longer timescales (decadal to centennial). To respond to the dual challenges of enhancing carbonate budget assessments and advancing their predictive capacity, we applied a novel model elicitation and review method to create a qualitative geo-ecological carbonate reef system model that links geomorphic, ecological and physical processes. Our approach conceptualizes relationships between net carbonate production, sediment transport and landform stability, and rates knowledge confidence to reveal major knowledge gaps and critical future research pathways. The model provides a blueprint for future coral reef research that aims to quantify net carbonate production and sediment dynamics, improving our capacity to predict responses of reefs and reef-fronted shorelines to future climate change.https://nsuworks.nova.edu/occ_facbooks/1116/thumbnail.jp

Chapter 4 PREDICTING RESPONSES OF GEO-ECOLOGICAL CARBONATE REEF SYSTEMS TO CLIMATE CHANGE: A CONCEPTUAL MODEL AND REVIEW

oceanography, climate change, reefs, marine science, marine conservation, marine researc

Reciprocal facilitation and non-linearity maintain habitat engineering on coral reefs

Ecosystem engineers that create habitats facilitate the coexistence of many interacting species. This biotic response to habitat engineering may result in non-intuitive cascading interactions, potentially including feedbacks to the engineer. Such feedback mechanisms, either positive or negative, may be especially important for the maintenance of biogenic habitats and their community-wide facilitation. Here, we describe the complex interactions and feedbacks that link marine habitat-forming engineers, the reef-building corals, and a group of herbivores, the parrotfishes; the latter preventing the overgrowth of macroalgae, a major competitor of corals. Using density data of eight parrotfish species on a Caribbean reef, we first describe the form of the response of parrotfish abundance to increasing topographic complexity generated by coral growth. Topographic complexity enhanced parrotfish abundance by promoting habitat suitability, but the shape (linear vs asymptotic) and strength of this response varied across species and size. Parrotfish grazing intensity, estimated from data on abundance and species-, size- and life phase-specific grazing rates also increased with topographic complexity despite an increase in the surface area over which parrotfish graze. Depending on fish species, this functional response was found to be linear or asymptotic. Using a simple analytical model we then explored the effects of topographic complexity and fishing pressure on coral-algal competition, with particular emphasis on the implications of non-linearities in the intensity of grazing. Simulations demonstrate that fishing and habitat degradation impair the performance of grazing, but that an asymptotic response of grazing intensity to topographic complexity increases the ecological resilience of coral reefs. Parrotfish and corals are mutually beneficial by creating a loop of positive, indirect feedbacks that maintain their own structure and function: coral growth promotes habitat suitability for parrotfish, concordantly enhancing grazing intensity, which in turn facilitates coral growth by reducing competitive exclusion by macroalgae. We conclude that the resilience of biogenic habitats is enhanced by non-linear biotic responses to engineering and by the emergence of reciprocal facilitation linking habitat engineering and response organisms. © 2012 The Authors. Oikos © 2012 Nordic Society Oikos

Les poissons des récifs coralliens de Nouvelle-Calédonie (estimations d' abondance, relations habitat-poissons, interactions trophiques et indicateurs écologiques)

AIX-MARSEILLE2-Stat.Mar. Endoume (130552206) / SudocPARIS-BIUSJ-Thèses (751052125) / SudocBANYULS/MER-Observ.Océanol. (660162201) / SudocPARIS-Museum-Bib. d'ichtyologie (751052306) / SudocRENNES-Agrocampus-Bibl. Linné (352382308) / SudocPARIS-BIUSJ-Sci.Terre recherche (751052114) / SudocSudocFranceF

Synergistic impacts of global warming on the resilience of coral reefs

Recent epizootics have removed important functional species from Caribbean coral reefs and left communities vulnerable to alternative attractors. Global warming will impact reefs further through two mechanisms. A chronic mechanism reduces coral calcification, which can result in depressed somatic growth. An acute mechanism, coral bleaching, causes extreme mortality when sea temperatures become anomalously high. We ask how these two mechanisms interact in driving future reef state (coral cover) and resilience (the probability of a reef remaining within a coral attractor). We find that acute mechanisms have the greatest impact overall, but the nature of the interaction with chronic stress depends on the metric considered. Chronic and acute stress act additively on reef state but form a strong synergy when influencing resilience by intensifying a regime shift. Chronic stress increases the size of the algal basin of attraction (at the expense of the coral basin), whereas coral bleaching pushes the system closer to the algal attractor. Resilience can change faster—and earlier—than a change in reef state. Therefore, we caution against basing management solely on measures of reef state because a loss of resilience can go unnoticed for many years and then become disproportionately more difficult to restore

Integrating socio-economic drivers in an explicit-time, qualitative fisheries model: EcoMata

International audienceEcoMata is an explicit-time, qualitative modelling tool for assessing the ecosystem impacts of fishing and evaluating options for fishery management. EcoMata relies on the theory of timed automata, an original approach for modelling and verifying discrete-event systems where timing is important. Early developments of EcoMata have focused on the dynamics of predator-prey responses in a food web, under a variety of fishing intensities and natural disturbances. The dynamics of these interacting modules (food web, fishing and external disturbance) are ruled by explicit timing constraints on state transitions, with the possibility of integrating time delays in their execution. System states and properties can be verified over time using efficient model-checking techniques with the help of a dedicated high-level query language. EcoMata provides non-expert users (i.e., managers) with a friendly interface that allows the expression of user-oriented queries for testing the sustainability of fishery policies. Here, the model is being developed further by integrating simple socioeconomic drivers in the fishery system. Specifically, we introduce a new module of automata that describes the profits associated to a specific fishing intensity and specific timing. This new module allows the evaluation of management strategies that are economically viable. The approach is illustrated on a coral-reef fishery in the Pacific that has been the focus of previous modelling work. Timed automata offer a unified formalism for describing a variety of processes in which timing is critical. We show that ecological, economic and social drivers can be easily integrated in the EcoMata framework for exploring the sustainability of fisheries in a data-poor context

Plan de gestion Méditerranée (complément)

Bien que les Calendriers d’Activité ne soient pas réalisés pour définir précisément les paramètres d’effort de pêche (par métier en zone d’activité, en période d’activité, ou en nombre de navire) l’analyse de cette source d’information permet une première caractérisation pertinente des activités concernées par les plans de gestion. En fonction de la géographie très variable des différents plans de gestion (dimension, forme) il sera nécessaire de réaliser des focus ou d’utiliser des référentiels plus détaillés lors des prochaines enquêtes de terrain destiner à reconstituer les Calendriers d’Activité pour pouvoir disposer d’un outil d’observation plus précis sur les métiers concernés. Cette approche Calendrier d’Activité n’a pas vocation et ne doit pas se substituer aux obligations de déclaration statistique, qui est un processus continu et qui implique directement chaque pêcheur déclarant vis-à-vis de l’administration