Encounter with mesoscale eddies enhances survival to settlement in larval coral reef fishes

Abstract

Oceanographic features, such as eddies and fronts, enhance and concentrate productivity, generating high-quality patches that dispersive marine larvae may encounter in the plankton. Although broad-scale movement of larvae associated with these features can be captured in biophysical models, direct evidence of processes influencing survival within them, and subsequent effects on population replenishment, are unknown. We sequentially sampled cohorts of coral reef fishes in the plankton and nearshore juvenile habitats in the Straits of Florida and used otolith microstructure analysis to compare growth and size-at-age of larvae collected inside and outside of mesoscale eddies to those that survived to settlement. Larval habitat altered patterns of growth and selective mortality: Thalassoma bifasciatum and Cryptotomus roseus that encountered eddies in the plankton grew faster than larvae outside of eddies and likely experienced higher survival to settlement. During warm periods, T. bifasciatum residing outside of eddies in the oligotrophic Florida Current experienced high mortality and only the slowest growers survived early larval life. Such slow growth is advantageous in nutrient poor habitats when warm temperatures increase metabolic demands but is insufficient for survival beyond the larval stage because only fast-growing larvae successfully settled to reefs. Because larvae arriving to the Straits of Florida from distant sources must spend long periods of time outside of eddies, our results indicate that they have a survival disadvantage. High productivity features such as eddies not only enhance the survival of pelagic larvae, but also potentially increase the contribution of locally spawned larvae to reef populations. population connectivity | selective mortality | otolith microstructure | mesoscale eddies | reef fish settlement

Larval fish dispersal in a coral-reef seascape

“…Observed rates of self-recruitment were much higher in 2005 (~60%) than in 2007, 2009 or 2011, for which measured rates in each of the three years were < 5%. Eddies have been hypothesized to play important roles in the successful return of larval coral-reef fishes to benthic habitats 38 and in the survival of reef fish larvae 39 . It is possible that mesoscale eddies are similarly influencing connectivity patterns in Kimbe Bay.…”

DNA barcoding of fish eggs collected off northwestern Cuba and across the Florida Straits demonstrates egg transport by mesoscale eddies

“…Based on long‐term satellite ocean color measurements, Zhang, Hu, Liu, Weisberg, and Kourafalou (2019) revealed strong seasonality of mesoscale cyclonic eddy occurrence in the Florida Straits with the highest occurrence in the summer and lowest occurrence in the winter. These cyclonic eddies are highly productive ecosystems that are rich in nutrients, phytoplankton, and copepods (Hitchcock et al., 2005; Lee, Clarke, Williams, Szmant, & Berger, 1994) and can influence cross‐shelf transport of fish larvae (Lane, Smith, Graber, & Hitchcock, 2003; Lee et al., 1992; Limouzy‐Paris, Graber, Jones, Röpke, & Richards, 1997; Shulzitski, Sponaugle, Hauff, Walter, & Cowen, 2016; Shulzitski et al., 2017; Sponaugle, Lee, Kourafalou, & Pinkard, 2005). Sponaugle et al.…”

Florida’s Oceans and Marine Habitats in a Changing Climate

“…Frontal eddies of the Florida Current also coincide with multi-taxa (29 fish families) larval coral reef fish recruitment in the upper Keys (Sponaugle et al 2005) from spawning sites in the Dry Tortugas (Lee and Williams 1999). Reef fish larvae entrained into eddies along the Florida Current exhibit higher growth rates due to greater resource availability, which ultimately correspond to high survival rates and recruitment onto the reef (Shulzitski et al 2016). There is new evidence that even large game fish (permit) are recruited from local spawning sites in the southern Keys (Dry Tortugas region) rather than from spawning locations within the Caribbean (Bryan et al 2015).…”

“…Further, reef fish are sensitive to extraction and loss of reef structure and adjacent habitats, including the coral-seagrass-mangrove complex. In Florida, eddies associated with coastal currents transport larval invertebrates, including coral, shrimp, and fish from local spawning grounds (e.g., Tortugas, Pulley Ridge Reefs) to Florida Reef Tracts (Lee and Williams 1999;Sponaugle et al 2005;Ault et al 2014;Shulzitski et al 2016;Vaz et al 2016) and local estuaries (e.g., Florida Bay pink shrimp; Criales et al 2007). Thus, predictions of a slowing AMOC and Gulf Stream system under climate change that reduce the Florida and Loop currents by 25% and weaken accompanying gyres are likely to have wideranging consequences for population dynamics, fisheries management, and overall secondary productivity of Florida's coral reefs and associated estuary, bay, and lagoon ecosystems.…”