How Much Do Marine Connectivity Fluctuations Matter?

Abstract

There is growing awareness that fluctuations in larval flux (connectivity) depress the long-run growth of marine metapopulations, but by how much is unclear. Here, we explore how reproductive schedule and larval behavior affect how much connectivity fluctuations depress growth. We combine larval dispersal simulations from the Florida Keys with theoretical results to calculate the effect of fluctuations on bicolor damselfish (Stegastes partitus). We find that fluctuations depress growth only slightly (∼2%), but the effect would be much stronger for an organism that spawned only part of the year. Larval behavior can also matter, as vertical migration allows larvae to become entrained in eddies. Eddies synchronize connectivity fluctuations, further decreasing growth. However, here, they also divide the Keys into largely independently fluctuating regions, mitigating the effects of local synchrony. Therefore, in situations where connectivity fluctuations matter, the presence of independently fluctuating regions due to larval behavior may be important.

Drift in ocean currents impacts intergenerational microbial exposure to temperature

“…Their position in the ocean was tracked (backward in time) for 500 d before their arrival at their destination grid, and their thermal histories were averaged for analysis, using the wellestablished and open-source Connectivity Modeling System (28). This software has been extensively validated [e.g., in "physical oceanography mode" the amount of water carried by particles through the Indonesian Throughflow very closely resembles the Eulerian flux through the straits (29)] and is widely used in both physical oceanography and marine ecology and biology studies (30)(31)(32). We compared the magnitude of virtual particle velocities, based on the trajectories at each grid cell, with observed drifters in the ocean (33).…”

“…These particles were then tracked backward in time using the Connectivity Modeling System v1.1 (28). The Connectivity Modeling System has been extensively tested and widely applied in oceanographic and biological studies (30,31). In particular, its trajectories have been explicitly validated in the tropical Pacific (29).…”

Patterns and scales of connectivity: temporal stability and variation within a marine metapopulation

“…In particular, genetic approaches based on dispersal over multiple generations (e.g., Gilg andHilbish 2003, Palumbi 2003) integrate multiple dispersal events and thus cannot provide information on interannual variation in connectivity. Therefore, a combination of single-generation approaches of connectivity and other methods operating at different scales (e.g., genetic and hydrodynamic models) could provide a deeper understanding of metapopulation dynamics under fluctuating connectivity, particularly for population persistence, distribution, and species coexistence (Carson et al 2011, Salau et al 2012, Watson et al 2012, Snyder et al 2014. Our results are also consistent with those analyzing geochemical tags to determine connectivity on similar species (e.g., Carson et al 2010, Lopez-Duarte et al 2012, despite slight methodological differences in the quantification of certain processes (e.g., sampling period, post-settlement mortality; Le Corre et al 2012).…”

“…However, simulation studies predict that when dispersal is mostly driven by circulation, dispersal patterns can show great temporal variability due to the stochasticity of oceanographic transport processes (Gilg andHilbish 2003, Cowen et al 2006). Despite a few empirical and theoretical studies suggesting its importance (Cowen and Sponaugle 2009, Carson et al 2010, Hogan et al 2012, Watson et al 2012, Snyder et al 2014, temporal variability in patterns and scales of connectivity remains uncertain. Variability in connectivity is difficult to measure in coastal systems, especially for species characterized by a long pelagic larval phase Sponaugle 2009, Le Corre et al 2012).…”

Does behaviour affect the dispersal of flatback post-hatchlings in the Great Barrier Reef?

“…If the post-hatchlings were spending most of the time drifting near the surface, they would be swept directly into the EAC and dispersed into the Coral Sea. In contrast, if they were developing prolonged dives near reefs, the internal currents could increase their retention, as it happens with fish larvae and other small organisms [64]. However, if this was the case, we would expect to find more records of predated or stranded flatback turtles within the adjacent coral cays and islands of the Capricorn Bunker Group and Swain Reefs (figure 1 b )—both of which are areas with high rates of reef-based dive and fishing operations.…”