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Integrative and Comparative Biology Advance Access published June 4, 2012 Integrative and Comparative Biology Integrative and Comparative Biology, pp. 1–14 doi:10.1093/icb/ics090 Society for Integrative and Comparative Biology SYMPOSIUM Dispersal of Deep-Sea Larvae from the Intra-American Seas: Simulations of Trajectories using Ocean Models Craig M. Young,1,* Ruoying He,† Richard B. Emlet,* Yizhen Li,† Hui Qian,† Shawn M. Arellano,2,* Ahna Van Gaest,3,* Kathleen C. Bennett,* Maya Wolf,* Tracey I. Smart4,* and Mary E. Rice‡ *Oregon Institute of Marine Biology, University of Oregon, Charleston, OR 97420, USA; †Department of Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695, USA; ‡Smithsonian Marine Station at Downloaded from Ft. Pierce, Ft. Pierce, FL 34949, USA From the symposium ‘‘Dispersal of Marine Organisms’’ presented at the annual meeting of the Society for Integrative and Comparative Biology, January 3–7, 2012 at Charleston, South Carolina. 1 E-mail: [email protected] http://icb.oxfordjournals.org/ 2Present address: Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA 3Present address: Northwest Fishery Science Center, National Marine Fisheries Service, Newport, OR 97365, USA 4Present address: South Carolina Department of Natural Resources, Charleston, SC 29412, USA Synopsis Using data on ocean circulation with a Lagrangian larval transport model, we modeled the potential dispersal distances for seven species of bathyal invertebrates whose durations of larval life have been estimated from laboratory at D H Hill Library - Acquis S on November 25, 2013 rearing, MOCNESS plankton sampling, spawning times, and recruitment. Species associated with methane seeps in the Gulf of Mexico and/or Barbados included the bivalve ‘‘Bathymodiolus’’ childressi, the gastropod Bathynerita naticoidea, the siboglinid polychaete tube worm Lamellibrachia luymesi, and the asteroid Sclerasterias tanneri. Non-seep species included the echinoids Cidaris blakei and Stylocidaris lineata from sedimented slopes in the Bahamas and the wood-dwelling sipunculan Phascolosoma turnerae, found in Barbados, the Bahamas, and the Gulf of Mexico. Durations of the planktonic larval stages ranged from 3 weeks in lecithotrophic tubeworms to more than 2 years in planktotrophic starfish. Planktotrophic sipunculan larvae from the northern Gulf of Mexico were capable of reaching the mid-Atlantic off Newfoundland, a distance of more than 3000 km, during a 7- to 14-month drifting period, but the proportion retained in the Gulf of Mexico varied significantly among years. Larvae drifting in the upper water column often had longer median dispersal distances than larvae drifting for the same amount of time below the permanent thermocline, although the shapes of the distance–frequency curves varied with depth only in the species with the longest larval trajectories. Even species drifting for 42 years did not cross the ocean in the North Atlantic Drift. Introduction can disperse across ocean basins (Scheltema 1968, Planktonic larvae, which are found in the life cycles 1971). The issue has taken center stage recently of most benthic animals (Thorson 1964), connect with the widespread recognition that larval transport disjunct metapopulations on many spatial scales. influences recruitment, a process that is important in The potential for dispersal at these various scales is applied problems such as fisheries management, con- critically important in understanding population dy- servation, and the siting of marine protected areas. namics and biogeography in the sea (Cowen et al. The present study deals with larval dispersal in the 2006; Cowen and Sponaugle 2009; McClain and deep sea, a field that remains in its infancy. Hardy 2010). The role of larval dispersal in main- Work on genetic connectivity at hydrothermal taining the genetic structure of marine populations vents reveals little evidence for genetic structure on has been discussed from a theoretical standpoint ever moderate to large scales along the axes of ridges (re- since the discovery that some shallow-water larvae viewed by Vrijenhoek 1997, 2010) but shows ß The Author 2012. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: [email protected]. 2 C. M. Young et al. significant structure on opposite sides of biogeo- Eulerian current data have been applied at hydro- graphic barriers such as the Easter Island thermal vents (e.g., Chevaldonne et al. 1997; Marsh Microplate in the South Pacific (Won et al. 2003), et al. 2001). Chevaldonne et al. (1997) used such the Blanco Transform Fault in the northeastern models to explore a perceived discrepancy between Pacific (Johnson et al. 2006; Young et al. 2008), lack of genetic structure in alvinellid polychaetes and and fracture zones on the Mid-Atlantic Ridge the presumed absence of an effective dispersal stage. (O’Mullan et al. 2001). Later work on the embryos (Pradillon et al. 2005) Seamounts, which were once considered to be iso- revealed a mechanism, developmental arrest of em- lated habitats with high endemicity (reviewed by bryos, which may explain this discrepancy. Marsh Rogers 1994; McClain 2007), demonstrate a surpris- et al. (2001) used progressive vector models to pre- ing level of genetic connectivity that probably reflects dict that tube worm (Riftia pachyptila) larvae should larval dispersal (Smith et al. 2004; Samadi et al. disperse as much as 100 km during a 5-week plank- 2006). In contrast, invertebrates on homogeneous tonic period on the East Pacific Rise. abyssal soft bottoms may have significant genetic PLD is an important parameter for all dispersal Downloaded from structure on relatively small spatial scales (Zardus models, but the estimation and use of this parameter et al. 2006). are fraught with potential errors, especially when in- Recent work (reviewed by Cordes et al. 2007; formation on larval behavior is lacking (Shanks Olu-Le Roy et al. 2007) reveals that several 2009 ). The problems are compounded for deep-sea species-complexes of methane-seep invertebrates are species. For example, whereas shallow-water larvae http://icb.oxfordjournals.org/ found in both the eastern Atlantic (Gulf of Cadiz may experience only minor fluctuations in tempera- and Gulf of Guinea) and western Atlantic ture while dispersing, deep-sea larvae potentially can (Barbados Accretionary Prism, Gulf of Mexico, and move into water of different temperatures (Young Blake Plateau). However, genetic evidence et al. 1996a, 1998), thereby experiencing changes in (Olu-LeRoy et al. 2007) shows deep divergences metabolism, feeding rate, and other vital processes. among the morphologically similar amphi-Atlantic Four different methods have been employed for es- populations, suggesting infrequent connectivity. timating PLD in the deep sea. The first is laboratory at D H Hill Library - Acquis S on November 25, 2013 CO1 sequence data provide better evidence for con- culture, which is non-trivial for deep-sea species be- nection among seeps in the southern Caribbean, cause of the difficulty of maintaining correct condi- northern Gulf of Mexico, and the Blake Plateau off tions of temperature and pressure. Very few deep-sea the seaboard of North Carolina. Those species that species have been reared all the way to settlement. have been examined in the well-studied seeps on the The second method is to compute PLD from metab- Louisiana Slope show minimal evidence of genetic olism and available energy stores. This method is structure (McMullin et al. 2003, 2010; Carney et al. only valid for lecithotrophs and requires assumptions 2006). about temperature and metabolic efficiency. The Although demographic factors, external environ- third method is to follow cohorts of larvae in the mental factors, and the distributions of disjunct hab- plankton. This is feasible only for species with itats all play roles in determining genetic structure discrete spawning seasons and is especially diffi- (Vrijenhoek 2010; Coykendall et al. 2011), larval or cult for deep-sea species with long larval life. adult dispersal by oceanic currents is implicated as Finally, PLD may be estimated by comparison of an important mechanism of connectivity in virtually settlement time and spawning time. In the deep every species that has been examined. sea, these two parameters are seldom known with Biological factors such as ontogenetic vertical mi- certainty, so this method often requires back- gration, buoyancy of embryos, predation, food avail- calculation of settlement time using juvenile growth ability, developmental rate, and physiological rates. tolerances, all play roles in determining dispersal pat- Even when PLD is known, it is easy to make large terns, but these have been studied for relatively few errors in estimating dispersal potential unless realistic deep-sea animals. However, by knowing just a single oceanographic data are used. In a recent attempt to biological parameter, the length of larval life (plank- place upper and lower limits upon potential dispersal tonic larval duration [PLD]), and the speeds and of larvae, McCain and Hardy (2010) plotted most of directions of oceanic currents, one can estimate the the known PLDs for deep-sea animals against rough likely upper limit of dispersal distance and relate estimates of high and low current speeds in the deep probable dispersal trajectories to the biogeographic sea. Their plot showed that larvae

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