Dispersal Of Planktonic Larvae Research Articles

Unexpected mismatches in population structure among marine mussel life‐history stages reveal the true scales of planktonic larval dispersal

AbstractStudies investigating gene flow in sessile or sedentary marine species typically draw conclusions about larval dispersal by investigating genetic structure of adults. Here, we generated microsatellite data from adults, recruits, settlers and planktonic larvae of the brown mussel, Perna perna, from the southeast coast of South Africa, and identified a consistent mismatch in genetic structure between the adults and all earlier life stages. While adults could be assigned to two major geographical groups (western and eastern), most of the early‐stage mussels were strongly affiliated with the eastern group. This suggests that few of the early‐stage individuals present in the western portion of the sampling range will eventually establish themselves in the adult population, highlighting the importance of post‐recruitment processes as drivers of population structure. Our findings caution against the exclusive use of genetic data generated from adults to assess population connectivity facilitated by the dispersal of planktonic propagules.

Population Genetic Differentiation on the Hydrothermal Vent Crabs Xenograpsus testudinatus along Depth and Geographical Gradients in the Western Pacific

Connectivity in deep-sea organisms must be considered across both depth gradient and horizontal geographical scales. The depth-differentiation hypothesis suggests that strong environmental gradients (e.g., light, temperature, pressure) and habitat heterogeneity in the deep-sea can create selection pressure, and this can result in genetic population divergence. The hydrothermal vent crab Xenograpsus testudinatus (Xenograpsidae) is common in vents at Kueishan Island, Taiwan, ranging from 10 to about 300 m depths. Xenograpsus testudinatus has also been found in shallow water vents (3–20 m) at Kagoshima and the Izu archipelago of Japan. We examine the sequence divergences in the mitochondrial COI, 16S rRNA and D-loop genes, to test the hypothesis that there is significant genetic differentiation among populations of X. testudinatus along the depth gradient at Kueishan Island (30, 200, 209–224 and 250–275 m), and among different geographical regions (Kueishan, Kagoshima and the Izu archipelago) in the West Pacific. There is neither significant population differentiation among shallow or deep-sea vents, nor between geographical locations. Vertical migration of zoea, upwelling on the eastern coast of Taiwan and the strong effect of the Kuroshio Currents has probably resulted in a high level of planktonic larval dispersal of X. testudinatus along the depth and geographical gradients in the Western Pacific.

Planktonic larvae of Luciogobius sp. (Gobiidae) in a tropical estuary

Species of Luciogobius genus (Gobiidae) are distributed along the east coast of the West Pacific, and their early life stages occur in coastal waters and bays and estuaries. Little is known about their planktonic larval dispersal and morphology. To obtain baseline information on early larval stages of Luciogobius sp., we performed monthly ichthyoplankton net collections from September 2014 to August 2015 within the Kalong estuary in northern Vietnam. Successful collections of Luciogobius denote a new southern range extension of the genus, and northern Vietnam may be the southernmost distributional range of the Luciogobius. A total of 146 larvae [preflexion to postflexion stages, 1.8–13.3 mm body length (BL)] of Luciogobius sp. were collected from the center channels of the estuary in December to February and April. The larvae collected in Kalong were similar in general morphology to congeners. Still, they were distinguished from other descriptions of Luciogobius species by their melanophores being heavier along the mid-tail vertebrae, and shorter at the dorsal midline. The abundance of Luciogobius sp. was highest in January, and at the mid-outer stations of the estuary, where smaller and earlier preflexion larvae were collected, suggesting that these larvae are likely not be from the middle or upper reaches of the Kalong River. Based on the spatial and temporal occurrence of newly hatched larvae, it suggests that the Luciogobius sp. spawning season is from December to February when the water temperatures are lowest, and the spawning grounds being within the estuary or very close to coastal area. These findings further indicate the importance of this tropical estuary as a nursery for temperate and subtropical fish. The differentiation in its morphology and geographical distributions with higher latitudinal Luciogobius species was also discussed to reveal this genus’ diversity, and suggests further investigations into examining to possibility of new species.

Phylogeographic structure and population connectivity of a small benthic fish (Tripterygion tripteronotum) in the Adriatic Sea

AbstractAimPopulation connectivity of benthic marine organisms depends strongly on planktonic larval dispersal and is controlled by geographic distance and oceanographic structure. We examine isolation by distance versus resistance to barriers (ocean current boundaries) against a background of post‐glacial habitat expansion in a small benthic fish of the Adriatic Sea.LocationAdriatic Sea, Eastern Mediterranean.TaxonTripterygion tripteronotum.MethodsWe performed population genetic analyses using mitochondrial control region sequences of 550 individuals from 25 locations sampled along the Eastern Adriatic coast. Investigations of population structure included differentiation tests, cluster analyses and distance‐based redundancy analysis. We then ran Lagrangian simulations of passive larval drift to examine correlations among population structure, geographic distance and the Adriatic gyre system. To test for signatures of a post‐glacial range expansion, we modelled the demographic history of the populations and examined the geographic distribution of genetic diversity.ResultsGenetic population structure corresponded to the Adriatic gyres without additional effect of geographic distance. Inference of northward‐biased gene flow between the northern and the Istrian gyre was consistent with simulated trajectories of passive drift, whereas the phylogeographic break coinciding with the boundary between the Central and the Northern Adriatic gyre was stronger than predicted by drift simulations. Genetic connectivity of populations within gyres was high. Genetic signatures of population expansion were consistent with a rapid post‐glacial recolonization of the northern Adriatic.Main conclusionsThe combination of dense sampling and passive drift simulation allowed us to distinguish among effects of geographic distance, oceanographic features and palaeoenvironmental changes on current population structure. Comparisons between realized and potential connectivity illustrate the value of integrating different data sources to understand population structure and inform conservation planning.

Population connectivity of the crab Gandalfus yunohana (Takeda, Hashimoto & Ohta, 2000) (Decapoda: Brachyura: Bythograeidae) from deep-sea hydrothermal vents in the northwestern Pacific

AbstractGenetic connectivity provides a basis for evaluating the resilience of animal communities by elucidating gene flow and serves as a proxy for realized dispersal through planktonic larval dispersal, settlement, and reproductive success. Gandalfus yunohana (Takeda, Hashimoto & Ohta, 2000) is a brachyuran crab endemic to deep-sea hydrothermal vents in the northwestern Pacific. Although an iconic and often dominant species, the connectivity among its populations is yet to be examined. We obtained barcoding sequences of the mitochondrial COI gene of G. yunohana from four vent fields including two on the Izu Arc, one on the northern Mariana Arc, and one in the Okinawa Trough. Genetic diversity of populations on the Izu and northern Mariana arcs were similar and shared the dominant haplotypes, showing no genetic subdivision regardless of the habitat depth. The Okinawa Trough population, for which only one specimen was available, was not genetically different from specimens from the Izu/Mariana arc populations. Estimation of the number of immigrants among populations suggests that the migration from north to south is higher than in the reverse direction. Our results resonate with previous laboratory-culture experiments, suggesting a high dispersal capability for G. yunohana. Visual observations and sampling, however, suggest that G. yunohana is exceedingly rare in the Okinawa Trough. This perhaps results from a lack of sufficient larval supply from the Izu-Bonin-Mariana Arc vents, and there may not be a reproductive population in the Okinawa Trough.

Asymmetric dispersal is a critical element of concordance between biophysical dispersal models and spatial genetic structure in Great Barrier Reef corals

AbstractAimWidespread coral bleaching, crown‐of‐thorns seastar outbreaks, and tropical storms all threaten foundational coral species of the Great Barrier Reef, with impacts differing over time and space. Yet, dispersal via larval propagules could aid reef recovery by supplying new settlers and enabling the spread of adaptive variation among regions. Documenting and predicting spatial connections arising from planktonic larval dispersal in marine species, however, remains a formidable challenge.LocationThe Great Barrier Reef, Australia.MethodsContemporary biophysical larval dispersal models were used to predict long‐distance multigenerational connections for two common and foundational coral species (Acropora tenuis and Acropora millepora). Spatially extensive genetic surveys allowed us to infer signatures of asymmetric dispersal for these species and evaluate concordance against expectations from biophysical models using coalescent genetic simulations, directions of inferred gene flow, and spatial eigenvector modelling.ResultsAt long distances, biophysical models predicted a preponderance of north–south connections and genetic results matched these expectations: coalescent genetic simulations rejected an alternative scenario of historical isolation; the strongest signals of inferred gene flow were from north–south; and asymmetric eigenvectors derived from north–south connections in the biophysical models were significantly better predictors of spatial genetic patterns than eigenvectors derived from symmetric null spatial models.Main conclusionsResults are consistent with biophysical dispersal models yielding approximate summaries of past multigenerational gene flow conditioned upon directionality of connections. For A. tenuis and A. millepora, northern and central reefs have been important sources to downstream southern reefs over the recent evolutionary past and should continue to provide southward gene flow. Endemic genetic diversity of southern reefs suggests substantial local recruitment and lack of long‐distance gene flow from south to north.

Exploring the Ecology of Deep-Sea Hydrothermal Vents in a Metacommunity Framework

Species inhabiting deep-sea hydrothermal vents are strongly influenced by the geological setting, as it provides the chemical-rich fluids supporting the food web, creates the patchwork of seafloor habitat, and generates catastrophic disturbances that can eradicate entire communities. The patches of vent habitat host a network of communities (a metacommunity) connected by dispersal of planktonic larvae. The dynamics of the metacommunity are influenced not only by birth rates, death rates and interactions of populations at the local site, but also by regional influences on dispersal from different sites. The connections to other communities provide a mechanism for dynamics at a local site to affect features of the regional biota. In this paper, we explore the challenges and potential benefits of applying metacommunity theory to vent communities, with a particular focus on effects of disturbance. We synthesize field observations to inform models and identify data gaps that need to be addressed to answer key questions including: 1) what is the influence of the magnitude and rate of disturbance on ecological attributes such as time to extinction or resilience in a metacommunity; 2) what interactions between local and regional processes control species diversity, and 3) which communities are 'hot spots' of key ecological significance. We conclude by assessing our ability to evaluate resilience of vent metacommunities to human disturbance (e.g., deep-sea mining). Although the resilience of a few highly disturbed vent systems in the eastern Pacific has been quantified, these values cannot be generalized to remote locales in the western Pacific or mid Atlantic where disturbance rates are different and information on local controls is missing.

Temporal genetic patterns of diversity and structure evidence chaotic genetic patchiness in a spiny lobster.

Population structure of many marine organisms is spatially patchy and varies within and between years, a phenomenon defined as chaotic genetic patchiness. This results from the combination of planktonic larval dispersal and environmental stochasticity. Additionally, in species with bi-partite life, postsettlement selection can magnify these genetic differences. The high fecundity (up to 500,000 eggs annually) and protracted larval duration (12-24months) and dispersal of the southern rock lobster, Jasus edwardsii, make it a good test species for chaotic genetic patchiness and selection during early benthic life. Here, we used double digest restriction site-associated DNA sequencing (ddRADseq) to investigate chaotic genetic patchiness and postsettlement selection in this species. We assessed differences in genetic structure and diversity of recently settled pueruli across four settlement years and between two sites in southeast Australia separated by approximately 1,000km. Postsettlement selection was investigated by identifying loci under putative positive selection between recently settled pueruli and postpueruli and quantifying differences in the magnitude and strength of the selection at each year and site. Genetic differences within and among sites through time in neutral SNP markers indicated chaotic genetic patchiness. Recently settled puerulus at the southernmost site exhibited lower genetic diversity during years of low puerulus catches, further supporting this hypothesis. Finally, analyses of outlier SNPs detected fluctuations in the magnitude and strength of the markers putatively under positive selection over space and time. One locus under putative positive selection was consistent at both locations during the same years, suggesting the existence of weak postsettlement selection.

Oceanography promotes self-recruitment in a planktonic larval disperser.

The application of high-resolution genetic data has revealed that oceanographic connectivity in marine species with planktonic larvae can be surprisingly limited, even in the absence of major barriers to dispersal. Australia’s southern coast represents a particularly interesting system for studying planktonic larval dispersal, as the hydrodynamic regime of the wide continental shelf has potential to facilitate onshore retention of larvae. We used a seascape genetics approach (the joint analysis of genetic data and oceanographic connectivity simulations) to assess population genetic structure and self-recruitment in a broadcast-spawning marine gastropod that exists as a single meta-population throughout its temperate Australian range. Levels of self-recruitment were surprisingly high, and oceanographic connectivity simulations indicated that this was a result of low-velocity nearshore currents promoting the retention of planktonic larvae in the vicinity of natal sites. Even though the model applied here is comparatively simple and assumes that the dispersal of planktonic larvae is passive, we find that oceanography alone is sufficient to explain the high levels of genetic structure and self-recruitment. Our study contributes to growing evidence that sophisticated larval behaviour is not a prerequisite for larval retention in the nearshore region in planktonic-developing species.

Biodiversity and biogeography pattern of benthic communities in the coastal basins of India

ABSTRACTOur understanding of coastal biogeography patterns is presently limited to certain regions and marine groups. Comprehending large-scale patterns and their underlying predictors is critical due to the changing environmental conditions. The Indian coast, bounded by two contrasting seas, the Bay of Bengal and Arabian Sea, offers an excellent opportunity to determine the most important factors influencing coastal biogeography patterns. Here we use distribution data of 2581 species belonging to three benthic groups (polychaetes, gastropods and bivalves) to evaluate the role of environmental factors and coastal currents on the biogeography patterns. Data were obtained from the bioSearch database, developed by CSIR-NIO, Goa under the Census of Marine Life programme. As measures of diversity, we used species richness as well as taxonomic distinctiveness indices. Multivariate analyses were used in identifying biodiversity patterns and correlated biogeography patterns with environmental factors. This paper points out a clear difference between the eastern and western basins of India, but also within the basins. Mainland and island fauna also showed a clear distinction. The biogeography of the Indian coast is best explained by temperature, habitat heterogeneity and coastline length. Spatiotemporal variability in the boundary currents also forms an effective barrier for the dispersal of planktonic larvae of benthic fauna. This study has identified a finer scale division of the Indian coast that can help to effectively improve conservation plans. Our study is the first to attempt to understand the benthic biogeography patterns of the Indian coast. The findings will be useful in guiding future biogeography studies of this unique and underexplored marine system.

Long-distance dispersal via ocean currents connects Omani clownfish populations throughout entire species range.

Dispersal is a crucial ecological process, driving population dynamics and defining the structure and persistence of populations. Measuring demographic connectivity between discreet populations remains a long-standing challenge for most marine organisms because it involves tracking the movement of pelagic larvae. Recent studies demonstrate local connectivity of reef fish populations via the dispersal of planktonic larvae, while biogeography indicates some larvae must disperse 100–1000 s kilometres. To date, empirical measures of long-distance dispersal are lacking and the full scale of dispersal is unknown. Here we provide the first measure of long-distance dispersal in a coral reef fish, the Omani clownfish Amphiprion omanensis, throughout its entire species range. Using genetic assignment tests we demonstrate bidirectional exchange of first generation migrants, with subsequent social and reproductive integration, between two populations separated by over 400 km. Immigration was 5.4% and 0.7% in each region, suggesting a biased southward exchange, and matched predictions from a physically-coupled dispersal model. This rare opportunity to measure long-distance dispersal demonstrates connectivity of isolated marine populations over distances of 100 s of kilometres and provides a unique insight into the processes of biogeography, speciation and adaptation.

Connectivity, neutral theories and the assessment of species vulnerability to global change in temperate estuaries

One of the main adaptation strategies to global change scenarios, aiming to preserve ecosystem functioning and biodiversity, is to maximize ecosystem resilience. The resilience of a species metapopulation can be improved by facilitating connectivity between local populations, which will prevent demographic stochasticity and inbreeding. This investigation estimated the degree of connectivity among estuarine species along the north-eastern Iberian coast, in order to assess community vulnerability to global change scenarios. To address this objective, two connectivity proxy types have been used based upon genetic and ecological drift processes: 1) DNA markers for the bivalve cockle (Cerastoderma edule) and seagrass Zostera noltei, and 2) the decrease in the number of species shared between two sites with geographic distance. Neutral biodiversity theory predicts that dispersal limitation modulates this decrease, and this has been explored in estuarine plants and macroinvertebrates. Results indicate dispersal limitation for both saltmarsh plants and seagrass beds community and Z. noltei populations; this suggests they are especially vulnerable to expected climate changes on their habitats. In contrast, unstructured spatial pattern found in macroinvertebrate communities and in C. edule genetic populations in the area suggests that estuarine soft-bottom macroinvertebrates with planktonic larval dispersal strategies may have a high resilience capacity to moderate changes within their habitats. Our findings allow environmental managers to prioritize the most vulnerable species and habitats to be restored.

Detecting the Influence of Initial Pioneers on Succession at Deep-Sea Vents

Deep-sea hydrothermal vents are subject to major disturbances that alter the physical and chemical environment and eradicate the resident faunal communities. Vent fields are isolated by uninhabitable deep seafloor, so recolonization via dispersal of planktonic larvae is critical for persistence of populations. We monitored colonization near 9°50′N on the East Pacific Rise following a catastrophic eruption in order to address questions of the relative contributions of pioneer colonists and environmental change to variation in species composition, and the role of pioneers at the disturbed site in altering community structure elsewhere in the region. Pioneer colonists included two gastropod species: Ctenopelta porifera, which was new to the vent field, and Lepetodrilus tevnianus, which had been rare before the eruption but persisted in high abundance afterward, delaying and possibly out-competing the ubiquitous pre-eruption congener L. elevatus. A decrease in abundance of C. porifera over time, and the arrival of later species, corresponded to a decrease in vent fluid flow and in the sulfide to temperature ratio. For some species these successional changes were likely due to habitat requirements, but other species persisted (L. tevnianus) or arrived (L. elevatus) in patterns unrelated to their habitat preferences. After two years, disturbed communities had started to resemble pre-eruption ones, but were lower in diversity. When compared to a prior (1991) eruption, the succession of foundation species (tubeworms and mussels) appeared to be delayed, even though habitat chemistry became similar to the pre-eruption state more quickly. Surprisingly, a nearby community that had not been disturbed by the eruption was invaded by the pioneers, possibly after they became established in the disturbed vents. These results indicate that the post-eruption arrival of species from remote locales had a strong and persistent effect on communities at both disturbed and undisturbed vents.

Egg-laying behaviour and intracapsular development of Argobuccinum pustulosum (Gastropoda: Ranellidae) in temperate waters at the South coast of Chile

Egg-laying behaviour, egg masses and intracapsular development of the ranellid snail Argobuccinum pustulosum are described here. Snails were collected by diving, at Corral Bay (39°53′S; 73°25′W) in the south of Chile, and adult individuals were reared in tanks with circulating seawater at ambient temperature to obtain their egg masses. The spawn produced is an irregular flat mass, taking between 3 and 9 days for the females to complete the egg deposition. Peduncleless tube-shaped capsules of 9–12 mm in length, amounted to 47–149 per mass (average = 100; n=9 masses). Eggs measured 168 µm in mean diameter. Number of eggs/embryos per capsule varied between 2500 and 5400. At mean temperatures of about 11.2–11.7°C, the intracapsular development lasted approximately 54–56 days, with the hatching of numerous planktotrophic veliger larvae of about 260 µm in shell length. Maximum production of larvae by a female is estimated at over 650,000 per spawn, and under multiple spawns it could exceed a million per breeding season. Capsule wall (100 µm thickness) consists of six laminae with protein fibres whose laminar arrangement permits a high light transmittance, accounting for the marked transparency of these capsules. Attributes of the development and of their hatching larvae, suggest a long period of planktonic larval dispersal for this snail. This would promote connectivity among geographically separated populations, thus in turn explaining the wide geographic distribution showed by this species in Southern oceans.

Mitochondrial genetic structure of two populations of Uca urugayensis fails to reveal an impact of the Rio de la Plata on gene flow

The Rio de la Plata. located between Uruguay and Argentina, generates a tremendous freshwater influx from the estuary into the coastal sea. It is thus suggested to constitute a biogeographic barrier for many taxa exhibiting a marine planktonic larval dispersal. However, evidence for corresponding intraspecific dispersal constraint has yet to be provided. We compared mitochondrial haplotypes of ten individuals for each of two populations of Uca (Leptuca) uruguayensis north and south of the estuary to examine the potential effect of the Rio de la Plata on the species' distribution. The populations are separated by nearly 2,000 km and were collected in Sao Paulo State (Brazil) and Mar Chiquita (Argentina). We found no significant indication for restricted gene flow between them, based on 823 basepairs of the mitochondrial cytochrome c oxidase subunit I gene. The structure of the corresponding haplotype network and the estimated nucleotide diversities, however, suggest that the Argentinean population is genetically more diverse than the one from Brazil. In order to establish possible significant differences in haplotype distribution, further research including more populations and larger sample sizes will be necessary.

Effects of geography and life history traits on genetic differentiation in benthic marine fishes

Dispersal of planktonic larvae can create connections between geographically separated adult populations of benthic marine animals. How geographic context and life history traits affect these connections is largely unresolved. We use data from genetic studies (species level FST) of benthic teleost fishes combined with linear models to evaluate the importance of transitions between biogeographic regions, geographic distance, egg type (benthic or pelagic eggs), pelagic larval duration (PLD), and type of genetic marker as factors affecting differentiation within species. We find that transitions between biogeographic regions and egg type are significant and consistent contributors to population genetic structure, whereas PLD does not significantly explain population structure. Total study distance frequently contributes to significant interaction terms, particularly in association with genetic markers, whereby FST increases with study distance for studies employing mtDNA sequences, but allozyme and microsatellite studies show no increase in FST with study distance. These results highlight the importance of spatial context (biogeography and geographic distance) in affecting genetic differentiation and imply that there are inherent differences in dispersal ability associated with egg type. We also find that the geographic distance over which the maximum pairwise FST between populations occurs (relative to total study distance) is highly variable and can be observed at any scale. This result is consistent with stochastic processes inflating genetic differentiation and/or insufficient consideration of geographic and biological factors relevant to connectivity.

A heuristic simulation model of Lake Ontario circulation and mass balance transport

The redistribution of suspended organisms and materials by large-scale currents is part of natural ecological processes in large aquatic systems but can contribute to ecosystem disruption when exotic elements are introduced into the system. Toxic compounds and planktonic organisms spend various lengths of time in suspension before settling to the bottom or otherwise being removed. We constructed a simple physical simulation model, including the influence of major tributaries, to qualitatively examine circulation patterns in Lake Ontario. We used a simple mass balance approach to estimate the relative water input to and export from each of 10 depth regime-specific compartments (nearshore vs. offshore) comprising Lake Ontario. Despite its simplicity, our model produced circulation patterns similar to those reported by more complex studies in the literature. A three-gyre pattern, with the classic large counterclockwise central lake circulation, and a simpler two-gyre system were both observed. These qualitative simulations indicate little offshore transport along the south shore, except near the mouths of the Niagara River and Oswego River. Complex flow structure was evident, particularly near the Niagara River mouth and in offshore waters of the eastern basin. Average Lake Ontario residence time is 8 years, but the fastest model pathway indicated potential transport of plankton through the lake in as little as 60 days. This simulation illustrates potential invasion pathways and provides rough estimates of planktonic larval dispersal or chemical transport among nearshore and offshore areas of Lake Ontario.

High Genetic Variability With No Apparent Geographic Structuring in the mtDNA of the Amphidromous River Shrimp Cryphiops caementarius (Decapoda: Palaemonidae) in Northern-Central Chile

Abstract Freshwater organisms with an amphidromous life cycle are generally thought to disperse widely through marine planktonic larval stages, but only few studies on genetic population structure of amphidromous shrimp exist. We used a 640-basepair region of the mitochondrial gene cytochrome c oxidase I (Cox1) from the amphidromous river shrimp Cryphiops caementarius from five rivers in northern-central Chile to test whether large distances between estuaries (up to 700 km) limit gene flow between populations and result in genetic differentiation among populations. The results revealed high haplotype diversity with no significant geographical structuring, suggesting that gene flow occurs regularly over several hundreds of kilometres, also connecting populations north and south of the Atacama Desert. Seemingly, the terrestrial barrier is overcome by planktonic larval dispersal through the sea, suggesting wide dispersal rather than “stepping-stone” dispersal between estuaries. The population from the southe...

Variable reproductive success in fragmented populations

Marine habitats are naturally patchy and anthropogenic disturbance can further fragment them. Many marine animals are sessile as adults or obligate inhabitants of particular habitats, so populations living in isolated patches of habitat are linked largely by dispersal of planktonic larvae. Theoretically, larvae are more likely to find and settle into large patches of habitat than small patches, thus small habitat patches may experience a more discontinuous supply of recruits resulting in small populations with unusual size- or age-structures or odd sex ratios — conditions where Allee effects on reproductive success are likely. We tested this hypothesis for the Caribbean spotted spiny lobster ( Panulirus guttatus), an obligate inhabitant of coral patch reefs whose mating dynamics are size-dependent. We found that P. guttatus were less abundant on small reefs where their size structure and per capita reproductive success were significantly more variable, particularly among large females that are susceptible to sperm limitation that diminishes fertilization rates. These results are indicative of Allee effects and provide a mechanistic understanding of how size-dependent mating dynamics influence reproductive success in ways that alter population dynamics in patchy habitats.

High-frequency coastal upwelling events influence Octopus vulgaris larval dynamics on the NW Iberian shelf

Planktonic larval dispersal affects the structure, management, and conservation of many fish and coastal invertebrate populations. The dynamics in coastal upwelling areas favour transport of larvae to the open ocean during upwelling episodes, and concentration of larvae in coastal waters un- der upwelling relaxation or downwelling conditions. Recent work provides evidence that pelagic lar- val stages in upwelling areas are influenced by specific larval behaviour, biogeography, and life his- tory parameters among others. Nevertheless, very few of these studies have addressed these findings quantitatively. Here, we present a general approach for assessing the influence of high-frequency up- welling events on Octopus vulgaris planktonic larvae. Specifically, we analyse the rates of change in abundance and biomass of the O. vulgaris early larval phase in the NW Iberian coast, where upwelling events occur with a frequency of 10 to 20 d from April to September. Our analysis indicates that the in- crease in larval abundance and biomass is significantly correlated with the simultaneous decrease of water column integrated nitrate, ammonium and chlorophyll levels. These conditions occur during the early stage of the relaxation phase of coastal upwelling events, when nutrient salts are consumed to produce biogenic matter, which is retained in the system and transferred through the food web.