Planktonic Duration Research Articles

Variation in Oceanographic Resistance of the World's Coastlines to Invasion by Species With Planktonic Dispersal.

For marine species with planktonic dispersal, invasion of open ocean coastlines is impaired by the physical adversity of ocean currents moving larvae downstream and offshore. The extent species are affected by physical adversity depends on interactions of the currents with larval life history traits such as planktonic duration, depth and seasonality. Ecologists have struggled to understand how these traits expose species to adverse ocean currents and affect their ability to persist when introduced to novel habitat. We use a high-resolution global ocean model to isolate the role of ocean currents on the persistence of a larval-producing species introduced to every open coastline of the world. We find physical adversity to invasion varies globally by several orders of magnitude. Larval duration is the most influential life history trait because increased duration prolongs species' exposure to ocean currents. Furthermore, variation of physical adversity with life history elucidates how trade-offs between dispersal traits vary globally.

Planktonic Duration of the Bryozoan Cyphonautes Larva and Limits on Growth Rate Imposed by Its Form-Limited Maximum Clearance Rate.

AbstractThe form of the cyphonautes larva of bryozoans changes little during development. The ciliated band that generates the feeding current increases nearly in proportion to body length, so that the maximum rate of clearing planktonic food from a volume of water becomes increasingly low relative to body protein. This development is unlike the other larvae that produce a feeding current with bands of simple cilia. The cyphonautes' growth rate has therefore been predicted to be unusually low when food is scarce. As predicted, cyphonautes larvae of a species of Membranipora starved at concentrations of food that supported growth of pluteus larvae. Comparisons between the cyphonautes and plutei of a sand dollar were for growth from first feeding to metamorphosis, with a mix of two algal species. Another comparison was for growth of cyphonautes at an advanced stage and plutei of a regular sea urchin at an early stage, with food in seawater at a reduced concentration. The low maximum clearance rate did not prevent rapid growth and development of some cyphonautes from egg through metamorphosis when food was abundant. Twenty-nine days for development to metamorphosis in the laboratory with abundant food was close to Yoshioka's estimate of larval duration from the time lag between adult zooid density and larval abundance in a population in the Southern California Bight. Despite individual variation in growth rates and other physiological and environmental influences, simple measures of larval form predicted the differences in larval performance: scarce food extended larval duration for the cyphonautes more than for plutei.

Long-term changes in a trochid gastropod population affected by biogenic sediment stability on an intertidal sandflat in regional metapopulation context

Although destabilization and stabilization of soft sediments by macro-infauna are regarded as key to understanding benthic community dynamics, how component populations are affected concurrently by both agents was poorly investigated. On an intertidal sandflat, Kyushu, Japan during 1979 − 2014 (previous study) and 2015 − 2019, monitoring was made of the populations of the filter-feeding gastropod, Umbonium moniliferum, the burrow-dwelling ghost shrimp, Neotrypaea harmandi (destabilizer), and the tube-building polychaete, Mesochaetopterus minitus (stabilizer). Results revealed that gastropod population changes were driven by an interplay of shrimp, polychaete, and the stingray, Hemitrygon akajei, foraging for shrimp by sediment excavation. The gastropod went through high abundance (1100 m−2) in 1979, extinction during 1986 − 1997, two marked recoveries with peaks in 2001 and 2009, a slight recovery in 2016, and near extinction in 2019. These changes largely followed the fluctuation in shrimp density across a threshold of 160 m−2 inhibiting gastropod recruitment. The polychaete exhibited intermittent outbreaks with peaks in 2000, 2007, and 2016, with maximum densities of 15,000 − 24,000 m−2. Sandflat topography and sedimentary variables were measured during 2015 − 2017. Sediment stabilization by polychaete aggregations at the mid-tidal zone is suggested to have boosted gastropod recruitment. Release at sea and retrieval on shore of drift cards mimicking gastropod larvae with 3- to 9-day planktonic duration was conducted in 2008 − 2009 to specify source populations sending larvae to the present population. Potential source populations were censused in 1998 and 2017 − 2018. Their recent virtual extinction appears responsible for the present population’s decline from 2011. This raises the need for metapopulation perspective to understand local dynamics.

Effects of marine heatwave conditions across the metamorphic transition to the juvenile sea urchin (Heliocidaris erythrogramma)

For short development species, like the sea urchin Heliocidaris erythrogramma, the entire planktonic duration can be impacted by marine heatwaves (MHW). Developmental thermal tolerance of this species through metamorphosis was investigated over a broad range (7.6–28.0 °C), including temperatures across its distribution and MHW conditions. In controls (19.5–21.0 °C), 80% of individuals developed to metamorphosis at day 5, doubling to 10 days at 14.0 °C. The thermal range (14.4–21.2 °C) of metamorphosis on day 7 reflected the realised thermal niche with 25.9 °C the upper temperature for success (T40). By day 10, juvenile tolerance narrowed to the local range (16.2–19.0 °C), similar to levels tolerated by adults, indicating negative carryover effects across the metamorphic transition. Without phenotypic adjustment or adaptation, regional warming will be detrimental, although populations may be sustained by thermotolerant offspring. Our results show the importance of the metamorphic transition in understanding the cumulative sensitivity of species to MHW.

Global biogeography of marine dispersal potential.

The distance travelled by marine larvae varies by seven orders of magnitude. Dispersal shapes marine biodiversity, and must be understood if marine systems are to be well managed. Because warmer temperatures quicken larval development, larval durations might be systematically shorter in the tropics relative to those at high latitudes. Nevertheless, life history and hydrodynamics also covary with latitude-these also affect dispersal, precluding any clear expectation of how dispersal changes at a global scale. Here we combine data from the literature encompassing >750 marine organisms from seven phyla with oceanographic data on current speeds, to quantify the overall latitudinal gradient in larval dispersal distance. We find that planktonic duration increased with latitude, confirming predictions that temperature effects outweigh all others across global scales. However, while tropical species have the shortest planktonic durations, realized dispersal distances were predicted to be greatest in the tropics and at high latitudes, and lowest at mid-latitudes. At high latitudes, greater dispersal distances were driven by moderate current speed and longer planktonic durations. In the tropics, fast currents overwhelmed the effect of short planktonic durations. Our results contradict previous hypotheses based on biology or physics alone; rather, biology and physics together shape marine dispersal patterns.

Physiology of growth in typical and transversus echinopluteus larvae

AbstractMarine invertebrate larvae are diverse in size and shape. Understanding the functional differences among these larvae and their ecological consequences is critical for understanding the evolution of larval forms and predicting responses to varying environmental conditions. This study compared the growth physiology of two morphologically distinct feeding larvae of echinoid echinoderms: the typical echinopluteus of Strongylocentrotus purpuratus, and the less well‐known echinopluteus transversus larva of Centrostephanus coronatus. Larvae of both types were reared at 16°C with 20,000 algal cells/ml of food. Despite striking differences in morphology (with late larvae of the two species bearing eight or two arms, respectively), ciliary band length grew at similar rates in both types of larvae. Significant differences between larval types were observed in growth in midline body length and stomach size. Physiologically, the typical echinopluteus larvae of S. purpuratus exhibited higher rates of protein growth, daily ingestion of algae, and aerobic respiration than did the echinopluteus transversus larvae of C. coronatus. The relationships between ingestion rate and ciliary band length or stomach size differed as well, with ingestion rate in larvae of S. purpuratus increasing much more rapidly than that of larvae in C. coronatus in relation to both morphological features. The higher physiological rates in S. purpuratus were not at the expense of increased physiological efficiency: larvae of S. purpuratus had digestive and growth efficiencies that were up to threefold higher than those in larvae of C. coronatus. Taken together, these results demonstrate fundamental differences in performance that go beyond the readily observable differences in morphology of these two larval forms. The reduced physiological capacity and growth efficiency of transversus larvae of C. coronatus provide a physiological basis for their long planktonic duration and possible teleplanktonic dispersal capabilities. The high physiological capacity and efficiency of the typical larvae of S. purpuratus may be adaptive for growing in areas of high seasonal algal abundance.

Stepping stones to isolation: Impacts of a changing climate on the connectivity of fragmented fish populations.

In the marine environment, understanding the biophysical mechanisms that drive variability in larval dispersal and population connectivity is essential for estimating the potential impacts of climate change on the resilience and genetic structure of populations. Species whose populations are small, isolated and discontinuous in distribution will differ fundamentally in their response and resilience to environmental stress, compared with species that are broadly distributed, abundant and frequently exchange conspecifics. Here, we use an individual‐based modelling approach, combined with a population genetics projection model, to consider the impacts of a warming climate on the population connectivity of two contrasting Antarctic fish species, Notothenia rossii and Champsocephalus gunnari. Focussing on the Scotia Sea region, sea surface temperatures are predicted to increase significantly by the end of the 21st century, resulting in reduced planktonic duration and increased egg and larval mortality. With shorter planktonic durations, the results of our study predict reduced dispersal of both species across the Scotia Sea, from Antarctic Peninsula sites to islands in the north and east, and increased dispersal among neighbouring sites, such as around the Antarctic Peninsula. Increased mortality modified the magnitude of population connectivity but had little effect on the overall patterns. Whilst the predicted changes in connectivity had little impact on the projected regional population genetic structure of N. rossii, which remained broadly genetically homogeneous within distances of ~1,500 km, the genetic isolation of C. gunnari populations in the northern Scotia Sea was predicted to increase with rising sea temperatures. Our study highlights the potential for increased isolation of island populations in a warming world, with implications for the resilience of populations and their ability to adapt to ongoing environmental change, a matter of high relevance to fisheries and ecosystem‐level management.

UV-A induced delayed development in the larvae of coral Seriatopora caliendrum

Coral reefs are vulnerable to ultraviolet radiation (UVR, 280–400nm). Not only do the fluxes of UVR fluctuate daily, they are also increasing due to global ocean and atmospheric changes. The deleterious effects of UVR on scleractinian corals have been intensively studied, but much less is known about the response of corals in the early pre-settlement phase. In this study, we tested how UVR exposure affects survival and development of Seriatopora caliendrum larvae and examined the photophysiological changes induced in the symbiotic dinoflagellate Symbiodinium. Results showed that the contents of chl c and carotenoids normalized to the number of algae cells in the larvae decreased significantly when larvae were exposed to UVR compared to those protected from UVR, while the cell density of Symbiodinium was higher in UVR-exposed larvae. The effective photochemical efficiency of the symbiotic algae increased when cultured under PAR plus UV-A (here taken as 320–395nm). We further present the novel finding that during the development experiment, presence of UV-A induced a decline in the rates of metamorphosis and settlement, which disappeared when the larvae were also exposed to UV-B (here defined as 295–320nm). However, UVR had no distinguishable effect on the numbers of larvae that either survived, metamorphosed or settled by the end of the culture period. Therefore, it is concluded from this study that UV-A radiation may extend the planktonic duration of coral larvae, but not have an overall inhibitory effect on developmental outcomes.

Increased larval planktonic duration and post‑recruitment competition influence survival and growth of the bryozoan Watersipora subtorquata

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 531:179-191 (2015) - DOI: https://doi.org/10.3354/meps11339 Increased larval planktonic duration and post‑recruitment competition influence survival and growth of the bryozoan Watersipora subtorquata Michael A. Sams1,2,*, Fletcher Warren-Myers1, Michael J. Keough1 1Department of Zoology, University of Melbourne, Victoria 3010, Australia 2School of Biological Sciences, University of Queensland, St. Lucia, Queensland 4067, Australia *Corresponding author: m.sams@uq.edu.au ABSTRACT: For organisms with complex life cycles, longer time spent in the plankton by dispersing propagules can cause reduced survival, growth and fecundity, which could alter interactions between neighbours in the post-dispersal environment. We compared post-settlement performance of bryozoan Watersipora subtorquata colonies that developed from larvae of different natural and experimental planktonic durations over ca. 15 wk of colony growth. Settlers were situated either near established adults of the ascidian Botrylloides leachii or without competition. Increased larval planktonic durations reduced colony growth in the absence of competition; colonies that developed from longer or delayed larval durations were 2 to 3 times smaller than those that developed from shorter durations. Colonies that developed from longer larval periods (natural or experimental) also experienced higher mortality (75 to 100%) than those that settled quickly (20 to 42%), but these effects varied between experiments and seasons. In winter, W. subtorquata colonies of longer larval planktonic durations experienced greater mortality when adjacent to established B. leachii, whereas differences in colony growth due to planktonic duration were reduced by adjacent B. leachii. The influence of B. leachii varied between experiments in different seasons, however, and did not alter colony performance in summer. Our findings demonstrate that while increased larval planktonic duration can be costly for post-dispersal growth and survival, some differences can be mediated by species interactions and environmental variability. This suggests that while connectivity among populations that take longer to disperse may be limited, it may also be influenced in complex ways by the post-recruitment environment and not simply dispersal duration. KEY WORDS: Larval dispersal · Planktonic duration · Competition · Marine bryozoan · Post-settlement · Watersipora Full text in pdf format Supplementary material 1Supplementary material 2 PreviousNextCite this article as: Sams MA, Warren-Myers F, Keough MJ (2015) Increased larval planktonic duration and post‑recruitment competition influence survival and growth of the bryozoan Watersipora subtorquata . Mar Ecol Prog Ser 531:179-191. https://doi.org/10.3354/meps11339 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 531. Online publication date: July 02, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.

Planktonic duration in fourteen species of intertidal rocky fishes from the south-eastern Pacific Ocean

The planktonic duration (PD) was determined in fourteen intertidal rocky fishes from the south-eastern Pacific Ocean by counting the otolith micro-increments from hatch check to a transition mark (TM). TMs were validated by comparing the PDs estimated from post-settlers with the total increment counts from otoliths of more recent (new) settlers. In 11 species (79%), the most common TM corresponded to a notable decrease in increment width after settlement. The PDs ranged from 45 days in the kyphosid Girella laevifrons to 135 days in the labrisomid Auchenionchus variolosus, and eight species (57%) had mean PDs of longer than three months. The mean observed size-at-settlement (SASM) values ranged from 17.5 ± 7.2 mm TL in Gobiesox marmoratus (Gobiesocidae) to 40 ± 5.5 mm TL in Calliclinus geniguttatus (Labrisomidae) and showed low variability within species of the same family. PDs were markedly longer in intertidal rocky fishes than in other littoral and reef fishes in tropical and temperate waters. A lengthy and variable duration of the pre-settlement phase, along with a relatively consistent size-at-competence within closely related species, are suggested as mechanisms through which these fishes may increase their probability to settle in the spatially restricted habitat of exposed rocky pools.

LARVAHS: Predicting clam larval dispersal and recruitment using habitat suitability-based particle tracking model

We herein explore the potential larval dispersal and recruitment patterns of Ruditapes decussatus and Ruditapes philippinarum clams, influenced by larval behavior and hydrodynamics, by means of a particle-tracking model coupled to a hydrodynamic model. The main contribution of this study is that a habitat suitability-based (ENFA, Environmental Niche Factor Analysis) settlement–recruitment submodel was incorporated into the larval dispersal model to simulate settlement behavior and post-settlement mortality. For this purpose, a specific study was carried out in the Bay of Santander (Northern Spain), a well-mixed shallow water estuary where shellfishery of both species is carried out. The model was fed with observed winds, freshwater flows and astronomical tides to obtain predictions during the clams spawning period. Dispersion of larvae from seven spawning zones was tracked, subjected to three-dimensional advection, vertical turbulent diffusion and imposed vertical migration behavior parameterized from existing literature. Three simulation periods (Spring, Summer and Autumn) and two initial releases (spring/neap tide) were combined in six different modeling scenarios. The LARVAHS model proved to be a powerful approach to estimating recruitment success, highlighting the role of habitat suitability, larval swimming behavior, planktonic duration, season (i.e. predominating winds) and spawning ground location on recruitment success together with the effect of the tidal phase at spawning. Moreover, it has proven to be a valuable tool for determining major spawning and nursery grounds and to explore the connectivity between them, having important implications for restoration strategies and shellfisheries as well as aquaculture management.

Consequences of the life history traits of pelagic larvae on interisland connectivity during a changing climate

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 489:43-59 (2013) - DOI: https://doi.org/10.3354/meps10432 Consequences of the life history traits of pelagic larvae on interisland connectivity during a changing climate Matthew S. Kendall1,*, Matthew Poti1,2, Timothy T. Wynne3, Brian P. Kinlan1,2, Laurie B. Bauer1,2 1NOAA National Ocean Service, National Centers for Coastal Ocean Science (NCCOS), Center for Coastal Monitoring and Assessment (CCMA), Biogeography Branch, 1305 East-West Hwy, Silver Spring, Maryland 20910-3281, USA 2Consolidated Safety Services, Inc., 10301 Democracy Lane, Suite 300, Fairfax, Virginia 22030, USA 3NOAA National Ocean Service, NCCOS, CCMA, Coastal Ocean Assessments, Status, and Trends Branch, 1305 East-West Hwy, Silver Spring, Maryland 20910-3281, USA *Email: matt.kendall@noaa.gov ABSTRACT: Many coral reef organisms possess a pelagic larval phase during which some larvae are retained near spawning sites and others are dispersed to more distant locations via ocean currents. Planktonic duration, distances traveled, and recruitment success can vary due to natural development rate, mortality rate, and sensory and swimming capabilities of particular taxa. Elevated water temperatures and acidification due to climate change can also influence recruitment by generally accelerating metabolism and growth, raising mortality rate, impairing development of calcified structures, and reducing sensory capabilities. We used hydrodynamic models and drifter data to investigate these various life history and climate-related influences on larval connectivity in and around the Samoan Archipelago. In general, virtual larvae spawned in the Samoan Archipelago seeded their natal reefs with relatively short-lived larvae, and their island neighbors to the west with longer-lived larvae. Larval duration, mortality rate, and sensory zone variables all had a significant effect on connectivity. Effect size was largest for mortality rate followed by larval duration. Shortened larval longevity due to climate change reduced interisland connectivity and changed the life history traits (and therefore taxa) that result in successful connections. Islands will generally become increasingly more reliant on self-seeding as the ocean warms, although the role of most islands primarily as a source or destination was robust to climate change. KEY WORDS: Biogeography · Climate change · Connectivity · Dispersal · Pelagic larval duration · Samoan Archipelago Full text in pdf format PreviousNextCite this article as: Kendall MS, Poti M, Wynne TT, Kinlan BP, Bauer LB (2013) Consequences of the life history traits of pelagic larvae on interisland connectivity during a changing climate. Mar Ecol Prog Ser 489:43-59. https://doi.org/10.3354/meps10432 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 489. Online publication date: August 28, 2013 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2013 Inter-Research.

Evaluating the importance of demographic connectivity in a marine metapopulation

Recently researchers have gone to great lengths to measure marine metapopulation connectivity via tagging, genetic, and trace-elemental fingerprinting studies. These empirical estimates of larval dispersal are key to assessing the significance of metapopulation connectivity within a demographic context, but the life-history data required to do this are rarely available. To evaluate the demographic consequences of connectivity we constructed seasonal, size-structured metapopulation matrix models for two species of mytilid mussel in San Diego County, California, USA. The self-recruitment and larval exchange terms were produced from a time series of realized connectivities derived from trace-elemental fingerprinting of larval shells during spring and fall from 2003 to 2008. Both species exhibited a strong seasonal pattern of southward movement of recruits in spring and northward movement in fall. Growth and mortality terms were estimated using mark-recapture data from representative sites for each species and subpopulation, and literature estimates of juvenile mortality. Fecundity terms were estimated using county-wide settlement data from 2006-2008; these data reveal peak reproduction and recruitment in fall for Mytilus californianus, and spring for M. galloprovincialis. Elasticity and life-stage simulation analyses were employed to identify the season- and subpopulation-specific vital rates and connectivity terms to which the metapopulation growth rate (lambda) was most sensitive. For both species, metapopulation growth was most sensitive to proportional changes in adult fecundity, survival and growth of juvenile stages, and population connectivity, in order of importance, but relatively insensitive to adult growth or survival. The metapopulation concept was deemed appropriate for both Mytilus species as exchange between the subpopulations was necessary for subpopulation persistence. However, highest metapopulation growth occurred in years when a greater proportion of recruits was retained within the predominant source subpopulation. Despite differences in habitat and planktonic duration, both species exhibited similar overall metapopulation dynamics with respect to key life stages and processes. However, different peak reproductive periods in an environment of seasonal current reversals led to different regional (subpopulation) contributions to metapopulation maintenance; this result emphasizes the importance of connectivity analysis for spatial management of coastal resources.

Plasticity of Hatching and the Duration of Planktonic Development in Marine Invertebrates

Plasticity in hatching potentially adjusts risks of benthic and planktonic development for benthic marine invertebrates. The proportionate effect of hatching plasticity on duration of larval swimming is greatest for animals that can potentially brood or encapsulate offspring until hatching near metamorphic competence. As an example, early hatching of the nudibranch mollusk Phestilla sibogae is stimulated by scattering of encapsulated offspring, as by a predator feeding on the gelatinous egg ribbon. When egg ribbons are undisturbed, hatching is at or near metamorphic competence. Disturbance of an unguarded benthic egg mass can insert 4 or more days of obligate larval dispersal into the life history. As another example, the spionid annelid Boccardia proboscidea broods capsules, each with both cannibalistic and developmentally arrested planktivorous siblings plus nurse eggs. Early hatching produces mainly planktivorous larvae with a planktonic duration of 15 days. Late hatching produces mainly adelphophages who have eaten their planktivorous siblings and metamorphose with little or no period of swimming. Mothers actively hatch their offspring by tearing the capsules, and appeared to time hatching in response to their environment and not to the stage of development of their offspring. Higher temperature increased the variance of brooding time. Females appeared to hatch capsules at an earlier developmental stage at lower temperatures. Species that release gametes or zygotes directly into the plankton have less scope for plasticity in stage at hatching. Their embryos develop singly with little protection and hatch at early stages, often as blastulae or gastrulae. Time of hatching cannot be greatly advanced, and sensory capabilities of blastulae may be limited.

Modelling dispersal of sea scallop ( Placopecten magellanicus) larvae on Georges Bank: The influence of depth-distribution, planktonic duration and spawning seasonality

The giant sea scallop ( Placopecten magellanicus) metapopulation on Georges Bank (GB) in the northwest Atlantic constitutes an economically important fishery, which is sustained by retention of planktonic larvae that are advected among three subpopulations. Dispersal of GB scallop larvae spawned in the fall is known to be sensitive to climate-related variability in the currents. Associated changes in temperature and stratification may elicit variations in biological responses that can also affect transport and these need to be examined. Additionally, no investigation has been made into transport of larvae spawned in spring, despite this being a consistently recurring phenomenon. Here, we quantified the influence of larval depth-distribution, planktonic larval duration (PLD) and spawning phenology on the retention and exchange of P. magellanicus larvae on GB. We developed a 3-D particle-tracking model to simulate larval transport in both spawning seasons using realistic circulation fields and assumptions about both larval behavior and PLD. Results were analyzed in terms of settlement distributions and dispersal matrices. Passive vertical behavior led to unrealistic depth-distribution in fall, while pycnocline-seeking behavior improved predicted settlement distributions and altered dispersal by factors of 2–5 for certain subpopulations. Simulations examining temperature-dependent larval development demonstrated significant effects of thermal history on PLD, and that associated changes in mean PLD of a few days can greatly alter connectivity. Larval transport in the spring exhibited increased downstream losses as well as sensitivity of retention to larval depth and spawning location. Our results demonstrate that biological factors significantly influence larval dispersal, and we need to reduce the uncertainty associated with estimates of these factors in order to predict effects of climate change on population connectivity.

Daily patterns of settlement and individual growth rates of young-of-the-year of the rockfish Sebastes inermis in a Sargassum bed

Otolith microstructure analysis was used to reveal the temporal patterns of settlement, planktonic duration and size-at-settlement (SAS) of young-of-the-year (YOY) of the rockfish Sebastes inermis in a Sargassum bed in Sendai Bay, northern Japan, during 2000 and 2001. Individual growth rates (IGR) during the planktonic period and after settlement for each settled group were also studied and compared to those of YOY collected in a Zostera marina bed. In both years, YOY settled in distinctive groups at new and full moon phases. SAS was surprisingly invariant (21.4–22.7 mm total length) while planktonic duration varied widely (range: 73–123 days), even within settlement groups and between years (mean = 88 days in 2000; mean = 105 days in 2001). In both years, IGR were remarkably lower during the planktonic period (range: 0.09–0.29 mm/d) than after settlement (range: 0.54–0.73 mm/d), demonstrating that Sargassum and Zostera marina beds are important nursery grounds for S. inermis. In conclusion, the analysis of variation in SAS vs planktonic duration along with the selection pressures on settlement size, were the most important driving factors in the settlement dynamics of this rockfish.

A boom–bust phylum? Ecological and evolutionary consequences of density variations in echinoderms

Echinoderms play a key role in structuring many marine ecosystems and are notorious for large population density variations in so‐called “outbreak” or “dieoff” events. In a review of this phenomenon, we assess the causal factors and ecological and evolutionary consequences. We identified 28 species (6 Asteroidea, 8 Echinoidea, 10 Holothuroidea, 4 Ophiuroidea) that exhibit large (more than two population doublings or halvings) population density changes. Three generalized patterns were identified and named for exemplary species: (1) rapid decreases followed by no or slow recovery (Diadema–Paracentrotus Model), (2), rapid increase and apparent stability at a new population density (Amperima–Amphiura Model), and (3) population density fluctuations (Acanthaster–Asterias Model). Echinoderms identified were distributed from the shallow intertidal to the deep sea, and from tropical to temperate regions. In most cases, significant impacts on the respective ecosystems were observed. The most striking similarity among all species identified was possession of the ancestral‐type planktotrophic larva. This larval type was significantly overrepresented in species identified within the Asteroidea, Echinoidea, Holothuroidea, and for the combined data set. We suggest three main factors that render a life history with planktotrophic larvae a high‐risk–high‐gain strategy: (1) a strong nonlinear dependency of larval production on adult densities (Allee effects), (2) a low potential for compensatory feedback mechanisms, and (3) an uncoupling of larval and adult ecology. The alternative (derived) lecithotrophic larva occurs in 68% of recent echinoderm species, suggesting an evolutionary trend toward this larval type. Lecithotrophic development represents a more buffered life history because compensatory feedback between adult densities and larval output is likely to be more efficient. For lecithotrophic developers, direct nutritive coupling from adult to larva to the early benthic juvenile provides a buffer against starvation. Lecithotrophic larvae are independent of the vagaries of planktonic food supply, and their short planktonic duration may promote local recruitment. Anthropogenic influences contributed to the population density variations in most cases, including increased primary productivity through eutrophication or global change, disease, overfishing, and species introductions. We suggest that anthropogenic disturbance, through its influence on the frequency and/or amplitude of echinoderm population density changes, may go beyond present ecosystem impacts and alter future evolutionary trends.

Internal borders for managing invasive marine species

Summary This study discusses theoretical and practical issues around the definition of internal borders for the management of marine pests, drawing on principles from freshwater and terrestrial pest management. Internal borders are defined as post‐border intervention points around which vector management and related activities, such as pest surveillance and incursion response, can be undertaken. Internal borders can be identified in marine systems based on knowledge of natural barriers to the dispersal or establishment of pests, including planktonic life stages. We highlight opportunities to define internal borders at broad spatial scales according to oceanographic features or environmental conditions. At smaller spatial scales, habitat barriers based on relatively permanent features (e.g. substratum) could be defined for target organisms (or suites of similar organisms), especially those having both restricted habitat requirements and a limited planktonic duration. Where internal borders are identified, risk‐based approaches can be used to determine vector management priorities, incorporating knowledge of the connectivity and strength of interactions between hubs of vector activity. However, greater biosecurity and biodiversity benefits may arise from approaches that combine risk‐based measures for target pests, with generic measures (e.g. vessel hull anti‐fouling) that are applied equally across all human‐mediated invasion pathways. Case studies of high‐profile marine pests in New Zealand illustrate situations where the benefits of internal border management have been realized. The challenge now is to identify how practical it is to widely apply internal borders in a marine biosecurity context, and to identify new internal borders around which management can practically be undertaken. Synthesis and applications. Effective control of pest species in marine environments is possible even when they become relatively widespread and established. The definition of internal borders provides an approach to marine biosecurity that assists in elucidating opportunities and priorities for management. Although marine systems are regarded as relatively open, the principles and approaches necessary for the successful management of marine pests are conceptually the same as those applied in freshwater systems and on land.

Modeling spiny lobster larval dispersion in the Tropical Atlantic

Spiny lobsters have a relatively long larval phase with a planktonic duration of about 1 year. Phyllosomas lack efficient swimming ability and large-scale oceanic geostrophic currents are responsible for long-distance transport of larvae away from the spawning area. This raises the possibility that adult stocks might be connected across large distances by larvae transport. We investigated larval dispersion across the Tropical Atlantic (20°N–15°S; 15°E–45°W) using a simple advection–diffusion model. The model updates the position of each virtual larva every day, over 365 days using the surface geostrophic velocity fields derived from satellite altimetry. The diffusive part of the model was calculated from drifting buoy velocities. We calculated the mean zonal and meridional diffusivity ( kx = 3.97 × 10 7 cm 2/s and ky = 2.05 × 10 7 cm 2/s) to incorporate into the model. The velocities obtained from the altimeter data were correlated with drifting buoy velocities resulting in a good agreement for both zonal ( r = 0.94, p = 0.05) and meridional ( r = 0.65, p = 0.05) components. This suggests that satellite-derived geostrophic flow is a good estimation for the real mean surface velocity field in the study region. Simulations indicate that Brazilian continental shelf adult stocks are connected to larvae released from oceanic islands, such as São Pedro and São Paulo Archipelago, Atol das Rocas and Fernando de Noronha Archipelago. Simulations also indicate that virtual larvae from the Ivory Coast are retained in the eastern side of the basin, whereas Cape Verde Archipelago virtual larvae do not spread far from the spawning area because of the local mesoscale eddy activity.

Modelling the effect of temperature on hatching and settlement patterns of meroplanktonic organisms: the case of octopus

The duration of embryonic development and the planktonic stage of meroplanktonic species is highly temperature dependent and thus the seasonal temperature oscillations of temperate regions greatly affect the patterns of hatching and benthic settlement. Based on data from the literature on embryonic development and planktonic duration of Octopus vulgaris (common octopus) in relation to temperature, and on observed temperature patterns, several models of hatching and settlement patterns were created. There was a good fit between observed settlement patterns and model predictions. Based on these models we concluded that in temperate regions: (1) when temperature is increasing (from early spring to mid summer) the hatching and settlement periods tend to shorten, while when the temperature is decreasing (during autumn) the hatching and settlement periods tend to lengthen; (2) hatching and settlement peaks are narrower and more intense than a spring spawning peak but wider and less intense than an autumn spawning peak; (3) at lower latitudes, hatching and settlement patterns tend to follow the spawning pattern more closely, (4) the periodic temperature pattern of temperate areas has the potential to cause a convergence of hatching during spring.