Identifying the key biophysical drivers, connectivity outcomes, and metapopulation consequences of larval dispersal in the sea

Abstract

BackgroundPopulation connectivity, which is essential for the persistence of benthic marine metapopulations, depends on how life history traits and the environment interact to influence larval production, dispersal and survival. Although we have made significant advances in our understanding of the spatial and temporal dynamics of these individual processes, developing an approach that integrates the entire population connectivity process from reproduction, through dispersal, and to the recruitment of individuals has been difficult.We present a population connectivity modelling framework and diagnostic approach for quantifying the impact of i) life histories, ii) demographics, iii) larval dispersal, and iv) the physical seascape, on the structure of connectivity and metapopulation dynamics. We illustrate this approach using the subtidal rocky reef ecosystem of Port Phillip Bay, were we provide a broadly-applicable framework of population connectivity and quantitative methodology for evaluating the relative importance of individual factors in determining local and system outcomes.ResultsThe spatial characteristics of marine population connectivity are primarily influenced by larval mortality, the duration of the pelagic larval stage, and the settlement competency characteristics, with significant variability imposed by the geographic setting and the timing of larval release. The relative influence and the direction and strength of the main effects were strongly consistent among 10 connectivity-based metrics.ConclusionsThese important intrinsic factors (mortality, length of the pelagic larval stage, and the extent of the precompetency window) and the spatial and temporal variability represent key research priorities for advancing our understanding of the connectivity process and metapopulation outcomes.Electronic supplementary materialThe online version of this article (doi:10.1186/s40462-015-0045-6) contains supplementary material, which is available to authorized users.

Larval Behavior and Longevity in the Cold-Water Coral Lophelia pertusa Indicate Potential for Long Distance Dispersal

“…The length of this period will significantly affect chances of self-recruitment onto the natal reef, with shorter pre-competency periods increasing the proportion of larvae settling locally (Treml et al, 2015). The PLD affects the geographic distance larvae will disperse with longer planktonic duration generally resulting in greater dispersal distance (Siegel et al, 2003;Selkoe and Toonen, 2011;Treml et al, 2015). The realized dispersal distance and direction can, in addition, be influenced significantly by larval behavior (Shanks, 2009).…”

“…Empirical measures of larval mortality under natural conditions are scarce despite its importance for dispersal outcomes (Treml et al, 2015). Mortality rates of larvae under laboratory conditions will not reflect mortality rates in the field where predation is an important controlling factor.…”

“…The pre-competency period, i.e., the time spent in the pelagic before larvae are competent to settle can, however, be inferred from laboratory studies. The length of this period will significantly affect chances of self-recruitment onto the natal reef, with shorter pre-competency periods increasing the proportion of larvae settling locally (Treml et al, 2015). The PLD affects the geographic distance larvae will disperse with longer planktonic duration generally resulting in greater dispersal distance (Siegel et al, 2003;Selkoe and Toonen, 2011;Treml et al, 2015).…”

“…While rapid progress is being made considering biophysical modeling, the biological data to accommodate these models are largely lacking (Davies and Guinotte, 2011;Hilário et al, 2015;Treml et al, 2015). Besides the importance of ocean currents and hydrodynamics at different scales, the species' life history traits and larval behavior significantly affect dispersal direction and distance (Shanks, 2009), and it is increasingly recognized that hydrodynamic models must include intrinsic larval properties and behavior to successfully predict dispersal routes and population connectivity (e.g., Siegel et al, 2003;Aiken et al, 2007;Cowen and Sponaugle, 2009;Moksnes et al, 2014;Fox et al, 2016).…”

“…Treml et al (2015) identified key biophysical drivers of connectivity among marine populations, using a subtidal rocky reef ecosystem as a model. The three parameters consistently found to be most influential on population connectivity were larval mortality during the dispersal phase followed by pelagic larval duration (PLD), and the extent of the pre-competency period.…”