Final Report Summary - PSICOPOPS (Post-settlement events influence on coral population structure: A multi-scale analysis along a latitudinal gradient)
Post-settlement events influence on coral population structure: A multi-scale analysis along a latitudinal gradient (PSICOPOPS)
Albeit recruitment processes are known to influence spatial patterns of adult coral assemblages, the relative influence of recruitment processes versus post-settlement events in population maintenance remains poorly known. Yet, understanding how populations are maintained is prerequisite for efficient management. This programme proposed to study the influence of post-settlement events on adult population structure in several habitats and islands of three regions following a latitudinal gradient, namely in the Australian Great Barrier Reef, New Caledonia and French Polynesia. This would allow for better understanding of the influence of early post-settlement events on population maintenance at local, insular and regional scale. In this goal, recruit and juvenile mortality and growth of several coral taxa with different life history traits were assessed as well as adult population structure, following a hierarchical sampling design. This programme was a collaborative project between the Unité Mixte de Recherche (UMR), Centre National de la Recherche Scientifique (CNRS), Ecole Pratique des Hautes Etudes (EPHE), Université de Perpignan Via Domitia (UPVD) 5244 'Tropical and Mediterranean biology and ecology' in Perpignan (France) and the Australian Research council (ARC) Centre of Excellence for Coral Reef Studies in Townsville, Australia. Both of these teams were at the cutting edge of coral reef ecology, respectively ranked first in Europe and first in the world.
The distribution and abundance of most marine organisms showed strong spatial heterogeneity at multiple scales, which was governed by a variety of physical and biological processes that varied in frequency, intensity and scale (Done 1983; Adjeroud 1997; Connolly et al. 2005). Larval supply was widely recognised as one of the major factors structuring adult assemblages (Caley et al. 1996; Armsworth 2002). However, there were often strong dissimilarities between settlement patterns and the distribution and abundance of adult corals (Bak and Engel 1979; Hughes et al. 1999; Miller et al. 2000). This suggested that distribution patterns established at settlement might be highly modified by spatial and temporal variation in post-settlement growth and mortality (Smith 1997; Edmunds 2000; Hughes and Tanner 2000; McClanahan et al. 2005). One of the key questions for ecologists was then to determine the degree to which spatial heterogeneity in the abundance of adult corals were influenced by pre- versus post- settlement processes (Caley et al. 1996; Fraschetti et al. 2002).
Coral recruitment fluctuations and their effect on adult coral assemblages was extensively studied over the last few years (Glassom et al. 2004; Vermeij 2005; Nozawa et al. 2006; Adjeroud et al. 2007a; Penin et al. 2007). Nevertheless, the relative contribution of pre-settlement processes, e.g. habitat selection by larvae, larval mortality and hydrodynamic process, and post-settlement events, e.g. competition, predation, facilitation and disturbance, on distribution and size of adult populations was still unclear. The importance of larval choice or supply in the structure of adult communities was evident in some situations (Baird and Hughes 1997; Mundy and Babcock 2000; Baird et al. 2003; Baird and Morse 2004; Glassom and Chadwick 2006; Norström et al. 2007), while post-settlement events, in particularly differential rates of early post-settlement growth and survivorship, were important in others (Connell 1973; Smith 1997; Baird and Hughes 2000; Miller et al. 2000; Vermeij 2006); however, the relative importance of pre- and post- settlement events was never tested.
Regions where adult abundance and percent cover were comparable could present profound differences in terms of functioning and particularly different recruitment and mortality rates (Hughes et al. 1999). As a consequence, there was a need to investigate implication of early post-settlement mortality in population size, i.e. the number of adults, and structure, i.e. their distribution in size classes, for different habitats and ecosystems.
Albeit recruitment processes are known to influence spatial patterns of adult coral assemblages, the relative influence of recruitment processes versus post-settlement events in population maintenance remains poorly known. Yet, understanding how populations are maintained is prerequisite for efficient management. This programme proposed to study the influence of post-settlement events on adult population structure in several habitats and islands of three regions following a latitudinal gradient, namely in the Australian Great Barrier Reef, New Caledonia and French Polynesia. This would allow for better understanding of the influence of early post-settlement events on population maintenance at local, insular and regional scale. In this goal, recruit and juvenile mortality and growth of several coral taxa with different life history traits were assessed as well as adult population structure, following a hierarchical sampling design. This programme was a collaborative project between the Unité Mixte de Recherche (UMR), Centre National de la Recherche Scientifique (CNRS), Ecole Pratique des Hautes Etudes (EPHE), Université de Perpignan Via Domitia (UPVD) 5244 'Tropical and Mediterranean biology and ecology' in Perpignan (France) and the Australian Research council (ARC) Centre of Excellence for Coral Reef Studies in Townsville, Australia. Both of these teams were at the cutting edge of coral reef ecology, respectively ranked first in Europe and first in the world.
The distribution and abundance of most marine organisms showed strong spatial heterogeneity at multiple scales, which was governed by a variety of physical and biological processes that varied in frequency, intensity and scale (Done 1983; Adjeroud 1997; Connolly et al. 2005). Larval supply was widely recognised as one of the major factors structuring adult assemblages (Caley et al. 1996; Armsworth 2002). However, there were often strong dissimilarities between settlement patterns and the distribution and abundance of adult corals (Bak and Engel 1979; Hughes et al. 1999; Miller et al. 2000). This suggested that distribution patterns established at settlement might be highly modified by spatial and temporal variation in post-settlement growth and mortality (Smith 1997; Edmunds 2000; Hughes and Tanner 2000; McClanahan et al. 2005). One of the key questions for ecologists was then to determine the degree to which spatial heterogeneity in the abundance of adult corals were influenced by pre- versus post- settlement processes (Caley et al. 1996; Fraschetti et al. 2002).
Coral recruitment fluctuations and their effect on adult coral assemblages was extensively studied over the last few years (Glassom et al. 2004; Vermeij 2005; Nozawa et al. 2006; Adjeroud et al. 2007a; Penin et al. 2007). Nevertheless, the relative contribution of pre-settlement processes, e.g. habitat selection by larvae, larval mortality and hydrodynamic process, and post-settlement events, e.g. competition, predation, facilitation and disturbance, on distribution and size of adult populations was still unclear. The importance of larval choice or supply in the structure of adult communities was evident in some situations (Baird and Hughes 1997; Mundy and Babcock 2000; Baird et al. 2003; Baird and Morse 2004; Glassom and Chadwick 2006; Norström et al. 2007), while post-settlement events, in particularly differential rates of early post-settlement growth and survivorship, were important in others (Connell 1973; Smith 1997; Baird and Hughes 2000; Miller et al. 2000; Vermeij 2006); however, the relative importance of pre- and post- settlement events was never tested.
Regions where adult abundance and percent cover were comparable could present profound differences in terms of functioning and particularly different recruitment and mortality rates (Hughes et al. 1999). As a consequence, there was a need to investigate implication of early post-settlement mortality in population size, i.e. the number of adults, and structure, i.e. their distribution in size classes, for different habitats and ecosystems.
