Résumé: The majority of studies on local ecological knowledge (LEK) relate to communities or groups relying on ecosystem(s) for their livelihood. In our case study, Mayotte Island, a French overseas department, very few people rely on mangrove ecosystem for natural resources but most of them are attached to it because of leisure activities and beliefs. The questions on mangrove LEK generally deal with a single aspect of ecological knowledge of surveyed people and is mixed with other information such as harvesting practices, anthropogenic impacts, and management issues. The aim of our study is to better understand the level of ecological knowledge of surveyed inhabitants of Mayotte and to assess whether factors linked to the profile of respondents have an influence on it. For this purpose, we carried out two main survey campaigns in three villages fringing two stable mangroves of Mayotte: the first one consisted of qualitative interviews and the second one, questionnaires lending quantitative results. Cross tabulations and Chi square tests of independence were carried out to determine the link between LEK and influencing factors. Results show that some LEK implying localized observation, such as the identification of mangrove trees and the knowledge of the coastal protection role of the mangrove, are well shared by surveyed people whereas others, such as the number and the name of mangrove tree species, are poorly known. The results also highlight the difficulty of questions implying observation at the landscape level and interpretation of observation. All the influencing factors selected have a significant influence on, at least, one LEK variable. The results highlight differences in LEK of villages bordering two nearby mangroves calling for a local management of these systems.

Résumé: Host-microbe interactions play crucial roles in marine ecosystems. However, we still have very little understanding of the mechanisms that govern these relationships, the evolutionary processes that shape them, and their ecological consequences. The holobiont concept is a renewed paradigm in biology that can help to describe and understand these complex systems. It posits that a host and its associated microbiota with which it interacts, form a holobiont, and have to be studied together as a coherent biological and functional unit to understand its biology, ecology, and evolution. Here we discuss critical concepts and opportunities in marine holobiont research and identify key challenges in the field. We highlight the potential economic, sociological, and environmental impacts of the holobiont concept in marine biological, evolutionary, and environmental sciences. Given the connectivity and the unexplored biodiversity specific to marine ecosystems, a deeper understanding of such complex systems requires further technological and conceptual advances, e.g., the development of controlled experimental model systems for holobionts from all major lineages and the modeling of (info)chemical-mediated interactions between organisms. Here we propose that one significant challenge is to bridge cross-disciplinary research on tractable model systems in order to address key ecological and evolutionary questions. This first step is crucial to decipher the main drivers of the dynamics and evolution of holobionts and to account for the holobiont concept in applied areas, such as the conservation, management, and exploitation of marine ecosystems and resources, where practical solutions to predict and mitigate the impact of human activities are more important than ever.

Résumé: The eastern oyster once provided major societal and ecosystem benefits, but these benefits have been threatened in recent decades by large declines in oyster harvests. In many areas, recovery of oyster aquaculture faces significant societal opposition and spatial constraints limiting its ability to meet expectations regarding future food needs and provision of ecosystem services. In Virginia, oyster aquaculture has begun to expand, concurrent with an increase in subaqueous leased areas (over 130,000 acres of grounds are currently leased). Though private leases must in theory be used for oyster production, in practice, they can be held for other reasons, such as speculation or intentional exclusion of others. These factors have led to large variation over time and space in the use of leases in lower Chesapeake Bay; and privately leased grounds are now thought to be underutilized for oyster production. This research examined potential barriers to expansion of oyster aquaculture in Virginia. We first evaluated if a lack of space was limiting industry expansion and quantified temporal and spatial trends in the use and productivity of leases. Then, differences in used and non-used leases were investigated in relation to variables thought to be related to “not in my backyard” attitudes, congestion, speculation, local economic and environmental conditions. Finally, the performance of the Virginia leasing system was compared with those in other states along the U.S. East and Gulf Coasts. We found limited evidence for spatial constraints on aquaculture leasing, but strong evidence for social and regulatory inefficiencies. Although rates of lease use increased from 2006 to 2016, only 33% of leases were ever used for oyster production and about 63% of leaseholders reported no commercial harvests. Non-used leases tended to be smaller, and were found in more populated, high-income regions, consistent with both speculative and exclusionary uses. Virginia had the second lowest level of total production of cultured oysters per leased acre among the states on the East and Gulf Coasts of the United States. These results indicate that there is room for oyster aquaculture expansion in Virginia if societal, regulatory, and economic barriers can be reduced or if existing leased areas are used more efficiently.