Different marine species and their larvae have characteristics that can expand or contract their potential dispersal, which can add complexity to the management of species assemblages. Here we used a ...multi-scale biophysical modeling framework, the Connectivity Modeling System, for the analysis of network connectivity for 5 Caribbean coral reef-associated species in order to gauge similarities and dissimilarities among species as well as among Caribbean regions. We estimated local dispersal and retention to assess regional exchanges, and our results revealed that the population structures of coral and fish are different and should thus have dissimilar management requirements in many regions, with some notable exceptions. Populations of Porites astreoides corals appear fragmented, suggesting that loss of adult colonies in any region may significantly impact regional recruitment success and connectivity. At the other end of the spectrum, populations of bluehead wrasse Thalassoma bifasciatum are highly connected, and removal of adults in any single region would not imply future recruitment failure in that region. We suggest using a ‘diversity of exogenous settlement’ index as a proxy of recolonization potential, which is related to the stability of regional connectivity networks. We demonstrate that resolving multispecies larval transport dynamics helps identify regions of both network stability for multi-generational connectivity (e.g. stable larval sources and corridors) pertinent to regional-level management and network inconsistencies among species which are pertinent to the success of local management.
Surfing, spinning, or diving from reef to reef Paris, Claire B.; Chérubin, Laurent M.; Cowen, Robert K.
Marine ecology. Progress series (Halstenbek),
10/2007, Volume:
347
Journal Article
Peer reviewed
Open access
Coral reef fish have considerable larval behavioral capabilities that can lead to successful completion of the early pelagic life phase. In particular, vertical migration during ontogeny increases ...retention near natal reefs and decreases losses due to transport by currents. For those larvae that are not returning home, the relative influence of behavior (biology) and currents (physics) on their arrival pattern among adjacent and distant reefs is not known. Moreover, interactions of the naturally small-scale larval movements with those of larger-scale currents need to be evaluated with regard to the spatial patterns of recruitment. We used an offline Lagrangian stochastic modeling approach to explore the relative influence of physical (i.e. eddy perturbation, diffusion) and biological processes (i.e. vertical movement, mortality) on the connectivity of the coral reef fish population in the western Caribbean, a region with complex geomorphology and circulation. This study revealed that the impact of larval behavior extends beyond enhancing the process of self-recruitment by changing population connectivity patterns. Connectivity was significantly influenced by larval vertical movement, survival, and by the eddy field, all controlling arrival patterns near reefs. A sensitivity analysis was done to gauge the robustness of the results by varying the model parameters. We found that particle-tracking models with homogeneous parameterization of the sub-grid motion tended to bias dispersal from and along the reef track, which can be mitigated by using spatially explicit parameters calculated from the Eulerian velocity fields. Finally, larval survival emerged as a key component for connectivity estimates, the study of which poses a great challenge in tropical ecosystems.
Behavior such as ontogenetic vertical migration (OVM) limits the transport of marine larvae with short pelagic larval durations (PLDs), but its effect on the supposed long-distance dispersal of ...larvae with long PLDs is unknown. We conducted laboratory tests of ontogenetic change in larval phototaxis and examined size-specific patterns of larval distribution in the plankton to characterize OVM in the Caribbean spiny lobsterPanulirus argusduring its long (6 mo) PLD. We then used a coupled biophysical model to explore the consequences of OVM and hydrodynamics on larvalP. argusdispersal in the Caribbean Sea. Larvae reared in the laboratory were positively phototatic for the first 2 mo and then avoided light thereafter, similar that seen in the planktonic distribution of same-sized larvae. Simulations of larval dispersal from 13 spawning sites in the Caribbean Sea predicted that twice as many larvae would recruit to nurseries if they displayed OVM compared with passive dispersers. Larvae with OVM typically settled <400 km from where they were spawned, while passive dispersers often settled >1000 km away. OVM also produced an asymmetrical bimodal pattern of dispersal dominated by larvae that settled near their origin (~60%), but showed a second peak of larvae that dispersed over long distances (~20%). Hydrodynamics created subregional differences in the potential for self-recruitment. Our findings suggest that (1) larval behavior constrains the dispersal of even long-lived larvae, particularly in tandem with retentive oceanographic environments, and (2) larval sources ofP. argusin the Caribbean Sea cannot be estimated from passive transport and surface circulation.
Scaling of Connectivity in Marine Populations Cowen, R. K.; Paris, C. B.; Srinivasan, A.
Science (American Association for the Advancement of Science),
01/2006, Volume:
311, Issue:
5760
Journal Article
Peer reviewed
Defining the scale of connectivity, or exchange, among marine populations and determining the factors driving this exchange are pivotal to our understanding of the population dynamics, genetic ...structure, and biogeography of many coastal species. Using a high-resolution biophysical model for the Caribbean region, we report that typical larval dispersal distances of ecologically relevant magnitudes are on the scale of only 10 to 100 kilometers for a variety of reef fish species. We also show the importance of the early onset of active larval movement mediating the dispersal potential. In addition to self-recruitment, larval import from outside the local area is required to sustain most populations, although these population subsidies are very limited in particular systems. The results reveal distinct regions of population isolation based on larval dispersal that also correspond to genetic and morphological clines observed across a range of marine organisms.
Celestial patterns in marine soundscapes Staaterman, Erica; Paris, Claire B.; DeFerrari, Harry A. ...
Marine ecology. Progress series (Halstenbek),
08/2014, Volume:
508
Journal Article
Peer reviewed
Open access
Soundscape ecology is the study of the acoustic characteristics of habitats, and aims to discern contributions from biological and non-biological sound sources. Acoustic communication and orientation ...are important for both marine and terrestrial organisms, which underscores the need to identify salient cues within soundscapes. Here, we investigated temporal patterns in coral reef soundscapes, which is necessary to further understand the role of acoustic signals during larval settlement. We used 14 mo simultaneous acoustic recordings from 2 reefs, located 5 km apart in the Florida Keys, USA to describe temporal variability in the acoustic environment on scales of hours to months. We also used weather data from a nearby NOAA buoy to examine the influence of environmental variables on soundscape characteristics. We found that high acoustic frequencies typically varied on daily cycles, while low frequencies were primarily driven by lunar cycles. Some of the daily and lunar cycles in the acoustic data were explained by environmental conditions, but much of the temporal variability was caused by biological sound sources. The complexity of the soundscape had strong lunar periodicity at one reef, while it had a strong diurnal period at the other reef. At both reefs, the highest sound levels (~130 dB re: 1 μPa) occurred during new moons of the wet season, when many larval organisms settle on the reefs. This study represents an important example of recently-developed soundscape ecology tools that can be applied to any ecosystem, and the patterns uncovered here provide valuable insights into natural acoustic phenomena that occur in these highly diverse, yet highly threatened ecosystems.
The present study investigated the larval fish dispersal along an estuarine-ocean gradient to explore connectivity between ocean and estuaries. During spring 2009, a combined ocean-estuarine survey ...was conducted along the Lima estuarine salinity gradient and in two transects off the adjacent coast (northwestern Iberian Peninsula), until the 100 m isobaths. Salinity, total particulate matter, particulate organic matter, total dissolved carbon, and dissolved organic carbon reached higher values at the ocean, and chlorophyll a and nutrients increased at the estuary. From the total 56 taxa identified, 14 were present along the gradient, including estuarine species (ES), marine stragglers (MS), and migrants (MM). Canonical correspondence analysis showed that species were separated along the gradient according to their ecological functional classification. MM associated with high salinity were separated from ES correlated with lower salinities and high chlorophyll a concentrations of inner estuary. Flounder (Platichthys flesus) showed a typical spatial gradient of MM, with abundance increasing from the ocean towards inner estuary. The dispersal of larvae along the Lima estuarine-ocean gradient was indicative of connectivity between habitats, emphasizing the need to consider this feature in management plans, mainly for species exploited by commercial fisheries.
Variability in environmental conditions and ocean currents can influence population connectivity and the exchange of larvae among locations. This is especially true for species that spawn in ...aggregations during a limited temporal window, such as many of the commercially and ecologically valuable species of snapper (Lutjanidae) in Cuba. Biophysical modeling has been used for over a decade to describe the pelagic pathways, sources, and sinks of lutjanid larvae. Here, we build on earlier studies by incorporating more advanced modeling techniques, higher resolution oceanography, and an expanded temporal scope using circulation from 2004 to 2013. Our goal was to revisit the relative linkages of Cuban snapper larvae among regions of the Cuban shelf and neighboring countries by investigating their interannual variability and spatial patterns. Biophysical simulations suggest the majority of larvae produced from snapper spawning aggregations are retained on-island, often within the region where they were spawned, with the exception of an aggregation in northwest Cuba. We used multinomial logistic regression to identify consistency in patterns of simulated biophysical larval transport, and to determine the number of years of simulation required to approximate connectivity. The best fit model correctly identified major connections from each spawning location to greater Caribbean destinations for each species. However, connections at smaller spatial scales were less predictable, and variance increased if fewer years of larval transport were considered. While the magnitude of settlement varies annually, the spatial arrangement of connectivity is relatively consistent such that modeled pathways from spawning aggregations can effectively inform connectivity planning, such as the placement of spawning reserves.
We examine the hypothesis that reef fish larvae have some direct influence on their own dispersal and ability to recruit to their natal reef by tracking cohorts of bicolor damselfish (Stegastes ...partitus) from hatching to settlement onto the reef, about 30 d later. We conducted high-resolution sampling during two consecutive years in a small area (15 km × 20 km) off the west coast of Barbados, extending from depths of 0 to 100 m. Observations of discrete stage-specific larval patches of mean size of 29.4 and $13.2\ \text{km}^{2}$ for preflexion (1-5-d old) and flexion/postflexion (>5-d old) stages extending ca. 30 m in the vertical indicated that larvae initially dispersing as patches tend to stay in coherent patches throughout their pelagic duration. Highest concentrations of preflexion larvae within a patch were in the upper 20 m, while those of older larvae were always deeper. Downward migration of about 60 m throughout ontogeny within stratified currents represented a retention mechanism for locally spawned larvae. Most of the variability in estimated retention rates between daily cohorts occurred during the earliest stages as a result of the dynamic nature of surface currents experienced by larvae prior to the onset of vertical migration. Differences in residence time between experiments were consistent with observed intermonthly variability in recruitment strength, implying that pelagic processes can explain recruitment rates. These results provide empirical evidence for larval retention of coral reef fishes and stress the role of active behavior in larval transport.
Larval dispersal is common in benthic marine organisms, but the environmental cues guiding the final larval stages to settlement habitat remain largely unknown. Caribbean spiny lobster Panulirus ...argus spend 5 to 12 mo at sea as pelagic phyllosome larvae before transitioning into rapidly swimming and non-feeding puerulus postlarvae. Spiny lobster postlarvae are specialized to seek settlement habitat, making them an ideal model for studying orientation behavior during the transition to benthic environments. We observed the swimming orientation of P. argus in the open ocean during all hours of the day and across tidal phases using a circular behavioral arena deployed at sea. Contrary to laboratory observations of only nocturnal activity, swimming and orientation occurred during both the day and the night in open waters ca. 6 to 8 km offshore in the Florida Straits. Individual postlarvae swam directionally with similar accuracy in all hours. The mean orientation direction was significantly different with tidal phase. Postlarvae oriented to the southeast (163.5°) during flood tide, and to the southwest during ebb flow (225.1°), placing them on a shoreward trajectory. Postlarval behavior was circatidal, and during ebb tide, innate swimming behavior beneficial to finding settlement habitat was triggered. Postlarvae also oriented relative to the wind, potentially using the sea breeze to orient towards the coast. A change in behavior tied to ubiquitous coastal signals is a strategy likely used by other pelagic larvae searching for a benthic home.
Larval coral-reef fishes have good orientation abilities. Through-water orientation of larvae in some species is location-dependent at meso-scales <10s of km, whereas other species have ...location-independent orientation at meso-scales. In situ observation of the damselfish Chromis atripectoralis showed that settlement-stage larvae swam in a southerly direction (mean = 175 ± 11°) at 100 to 1000 m from shore, both east and west of Lizard Island, northern Great Barrier Reef (NGBR), in 10 datasets from 1998 to 2008. Wind direction did not directly influence through-water swimming direction at NGBR. During 2014, in situ diver observation tested if orientation of C. atripectoralis differed regionally in the central Great Barrier Reef (CGBR), 620 km south of NGBR, and in the New Caledonia reef lagoon (NCRL), 1950 km east of CGBR. In all 3 regions, >90% of larvae swam directionally with similar precision and speeds, and with significant among-individual orientation. Yet through-water orientation was easterly at CGBR (72 ± 30°) and NCRL (87 ± 20°), and significantly different from NGBR. Over-bottom orientation (i.e. the result of current and larval swimming), measured by GPS at start and end of observing each larva, was weak east-southeasterly at NGBR (116 ± 40°, p = 0.045), not significantly directional at CGBR, and strongly westerly at NCRL (246 ± 28°, p = 0.0006), indicating that dispersal of C. atripectoralis is both current- and behaviour-dependent. This is the first report of location-dependent larval fish orientation at a regional scale. This might be an evolutionary response to regional hydrodynamic conditions to limit downstream dispersal.
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