Abundance Of Settlers Research Articles

Temporal and small-scale spatial variation in spatfall of the mussel Mytilus edulis platensis: Basis for culture management at San Jorge Gulf, Patagonia Argentina

Despite the commercial potential of mussel populations along the Patagonian coast of Argentina, studies on mussel farming and fisheries to the south of parallel 42° S are clearly insufficient thus far. In this study, variations in mussel settlement (between sites and across depths) were monitored for 12 months at two contrasting sites in San Jorge Gulf, Argentina. The effect of depth on spat density was evaluated through monthly samples taken from artificial collectors at three depths (3, 7 and 11 m). The temporal settlement pattern was consistent at both sites, with the maximum spatfall recorded in early March (late summer), coinciding with the peak of sea water temperature. Settlement also correlated with Chl a and particulate organic carbon peak values, typically manifesting 2–3 months later and followed the initial decline in mussel condition during late spring and early summer. Significant differences between localities were detected in settlement abundance. The optimal temporal gap for mussel settlement was observed in mid / late summer, suggesting that this is the optimal time to deploy spat collectors in the field. Settlement was uniform between depths, thereby implying that the specific depth of collector placement did not appear to emerge as a key factor of settlement success.

Quantitative uncertainty estimation in biophysical models of fish larval connectivity in the Florida Keys

Abstract The impacts of seven uncertain biological parameters on simulated larval connectivity in the Florida Keys are investigated using Polynomial chaos surrogates. These parameters describe biological traits and behaviours—such as mortality, swimming abilities, and orientation—and modulate larval settlement as well as dispersal forecasts. However, these parameters are poorly constrained by observations and vary naturally between individual larvae. The present investigation characterizes these input uncertainties with probability density functions informed by previous studies of Abudefduf saxatilis. The parametric domain is sampled via ensemble calculations, then a polynomial-based surrogate is built to explicitly approximate the dependence of the model outputs on the uncertain model inputs, which enables a robust statistical analysis of uncertainties. This approach allows the computation of probabilistic dispersal kernels that are further analyzed to understand the impact of the parameter uncertainties. We find that the biological input parameters influence the connectivity differently depending on dispersal distance and release location. The global sensitivity analysis shows that the interactions between detection distance threshold, orientation ontogeny, and orientation accuracy, are the dominant contributors to the uncertainty in settlement abundance in the Florida Keys. Uncertainties in swimming speed and mortality, on the other hand, seem to contribute little to dispersal uncertainty.

Settlement and recruitment pattern variability of the mussel Mytilus galloprovincialis Lmk. from SE Bay of Biscay (Basque Country)

The annual settlement and recruitment patterns of Mytilus galloprovincialis Lmk. were assessed using collector ropes deployed at five sites along the Basque coast inhabited by wild mussel populations. The study was carried out over two periods of ten months each in three estuarine and two coastal sites, and enabled the discovery of a potential relationship between observed primary settlement and the spawning period of wild mussel populations, shedding light on the recruitment of these populations. Primary settlers were present throughout the year with highest abundances from early summer to fall. A spatial settlement pattern was also observed, with eastern estuaries showing higher settlement rates than western ones and coastal sites showing intermediate settlement rates. These spatial and temporal settlement variations could be partially explained by seasonal fluctuations in environmental factors, such as temperature and nutrients, as well as by spawning differences observed at these estuarine and coastal sites. Some inter-annual variability of settlement and recruitment was observed, with higher settlement rates in the second studied year. This inter-annual variability was consistent with the inter-annual variability of the environmental factors. The recruitment of juvenile mussels was shown to be more determined by post-settlement processes than by initial settlement abundance. Indeed, there was a substantial loss of post-larvae during fall and winter, which was due to these post-settlement processes. Thus, it is advised that ropes, which were deployed in spring and collected in winter, to be collected earlier to avoid such losses. Little space is available (i.e., due to user conflict) on the Basque Coast. Despite these limitations, these sites, particularly Bidasoa estuary, could be suitable for future seed gathering for the mussel aquaculture industry in the Basque Country.

Depth and Seasonal Effects on the Settlement Density of Two Mussel Species (Perna Perna and Mytilus Galloprovincialis) in Offshore, Agadir (Morocco)

A study of spat settlement of two mussel species was carried out in Agadir area on the North Atlantic Coast, between Jan 2002 and Jan 2003. The preferred depth of settlement and settlement period of both species were monitored on collectors suspended in offshore at three different depths (1, 5, 10 m). For Perna perna, the effect of season on settlement was consistent, with relatively higher settlement both in spring (286-462 spats.m-1 ) and in summer (406-594 spats.m-1 ). Similar abundances of settlers were found at 1 m and 5 m depth whatever the season, which suggests a homogeneous distribution of settlers of P. perna in the first 5 m of the sea water. For Mytilus galloprovincialis, the settlement was less patchy in time in regard to P. perna (ρ<0.05). Thus, the settlement was continuous from spring to autumn until 10 m depth. The filamentous structures (laces in polypropylene) used in this study are often designed to enhance the amount of settlers, however, the settlement densities of both species were very low. Consequently, the results suggest that larval supply has been the limiting factor in the settlement success, but not the lack of suitable substrates. Moreover, the study area has poor spat falls and seems to be not suitable for collection of mussel spat.

Settlement Patterns of Corals and other Benthos on Reefs with Divergent Environments and Disturbances Histories around the Northeastern Arabian Peninsula

Larval supply is a principal factor determining the establishment, structure, and diversity of sessile benthic assemblages on coral reefs. Benthic reef communities in north-eastern Arabia have been subject to recurrent disturbances in recent years, and subsequent recovery will be, in part, driven by variation in the supply of available colonists. Using settlement tiles deployed seasonally over one year at eight sites encompassing three environmentally divergent regions (southern Arabian Gulf, the Musandam Peninsula in the Strait of Hormuz, and the Sea of Oman) we assessed spatial and seasonal variability in settlement of benthic reef organisms. There was strong spatial variation in composition of new colonists among regions, mainly driven by the high abundance of coralline algae in the Arabian Gulf, colonial ascidians on the Musandam Peninsula and barnacles in the Sea of Oman. Seasonal differences in composition of new colonists were less important than regional differences, with seasonal variation in settlement not consistent among regions. The number of corals settling to the tiles was low compared to those reported for other regions, with mean densities ranging from 0 corals m-2 yr-1 in the Sea of Oman to 30 (± 0.6 SE) and 38 (± 0.5 SE) in Musandam and the Arabian Gulf, respectively. Peak coral settlement abundance in the Gulf occurred in summer and autumn (5 – 8 spat m-2) and in Musandam in spring (7 spat m-2). This work provides the first record of large-scale spatial and seasonal patterns of settlement in north-eastern Arabia and provides valuable information on the supply of settlers available to recolonize heavily disturbed reefs in this region. The extremely low rates of coral settlement suggest that these marginal reefs are likely to be extremely slow to recover from ongoing and future disturbances.

An experimental assessment of measures of mussel settlement: Effects of temporal, procedural and spatial variations

Much research has focused on linking larval abundance and dispersal data to observed patterns of settlement. Consequently, measures of settlement have become increasingly important in benthic marine ecology and in understanding benthic-pelagic linkages. Potentially, measures could be confounded by complex settlement behaviors and physical variables that may impact on the abundance of larvae. The effects of timing or duration of deployment and data standardization (to a mussel per day rate) on measures of mussel settlement made using standardized artificial units of habitat (Tuffies™) were tested in three seven day trials. In addition, variations in methodological deployment procedure and position on the shore were assessed. The day of deployment and duration of sampling had species- and size-specific effects on measures of mussel settlement. The abundance of settlers of large (>500μm) Perna canaliculus was highly variable over short temporal scales (one day), and longer deployment durations indicated significant peaks and falls in the number of settlers per Tuffy over seven days. By contrast, the abundance of small (<500μm) Xenostrobus pulex increased linearly and measures taken over longer time-periods well reflected overall settlement. These data suggest that samples should, where possible, be sorted into species and size-classes because different settlement patterns may mask underlying settlement processes.

Environmental influences on the larval recruitment dynamics of snapper, Chrysophrys auratus (Sparidae)

Recruitment success in demersal fish species that settle in estuaries after a pelagic larval duration in coastal waters is dependent on (1) abiotic and biotic variables that promote good survival, and (2) local environmental conditions that facilitate and direct the transport of larvae to settlement habitats. In the present study, we described the patterns of larval abundance, pelagic larval duration and settlement of a commercially important sparid, Chrysophrys auratus, in northern New Zealand over 2 years, and investigated the relationships among pelagic larval duration or daily settler abundance and various environmental variables. Pelagic larval duration varied from 17 to 33 days and the successful spawning period that produced settled juveniles varied from 29 to 109 days among our four sites. For 91% of fish captured, the average temperature during the pelagic larval duration was &gt;18°C. Significant correlations between daily settler abundance and environmental variables varied among sites and between years; however, temperature, tidal range and on-shore winds were most strongly correlated with settlement, explaining up to 38% of the variability in settler abundance. The present results suggested that, in some locations, high water temperatures, large tides and on-shore winds are likely to increase recruitment success in C. auratus.

Relative importance of kelps and fucoids as substrata of the invasive epiphytic bryozoan Membranipora membranacea in Nova Scotia, Canada

The successful establishment of invasive species is partly dependent upon their ability to utilize effectively local resources available in the invaded ecosystem. In the rocky subtidal habitats of Nova Scotia, Canada, the invasive epifaunal bryozoan Membranipora membranacea oc- curs in high abundance on kelps, which offer high space availability but are highly dynamic. How- ever, this bryozoan also occurs on algae other than kelps, including Fucus species, which provide low space availability but higher stability than kelp. Previous research has focussed on population dynamics of the bryozoan on kelps, and the role of fucoids remains unknown. We quantified settlers and colony cover of M. membranacea on the kelps Saccharina latissima and Laminaria digitata (both native), and on Fucus evanescens (native) and F. serratus (introduced), at 4 sites in Nova Scotia, at various stages critical to the population dynamics of the bryozoan. The relative importance of kelp and fucoid substrata varied both intra- and interannually, as well as spatially. Settlement was higher on kelps than on Fucus spp. at sites where kelps were abundant; however, the abundance of settlers on Fucus spp. was similar to or greater than that on kelps at sites where kelps were sparse or spatially separated from Fucus spp. During the period of high colony cover in late autumn, cover was highest on L. digitata and lowest on Fucus spp. across all sites. After the winter, M. membranacea cover decreased by an order of magnitude on kelps, but remained stable on Fucus spp., suggesting high overwinter survival on fucoid algae. While kelps provide spatial re- sources for seasonal peaks in abundance of the invasive bryozoan, refuges can preserve local popu- lations at certain times. For example, Fucus spp. provides an important refuge for overwintering colonies, particularly where defoliation of kelps has been extensive, and characteristics of this sub- stratum probably facilitate early reproduction and local spread. Understanding the role of different components of an invaded ecosystem in the population dynamics of the introduced species can invoke possible mechanisms of successful establishment, spread and persistence.

Population dynamics of the invasive bryozoan Membranipora membranacea along a 450-km latitudinal range in the subarctic northwestern Atlantic

Thermal environment is often regarded as a key determinant of distribution limits in marine invertebrates and hence may represent one of the most important barriers to invasion by non-indigenous species. For the first time in the subarctic northwestern Atlantic, we investigated variation in the timing and magnitude of settlement, recruitment, and colony cover of the recently (early 2000s) introduced bryozoan Membranipora membranacea on the kelp Saccharina longicruris and how this variation relates to changes in sea temperature (thermal histories) across eight sites spanning a 450-km latitudinal range between southwestern Newfoundland and southeastern Labrador, Canada. We show that (1) up to 61 % of the variation in settlement, recruitment, and colony cover was explained by sea temperature alone, with highest and lowest abundances at warmest and coldest sites, respectively; (2) between-site differences in rates of sea cooling explained 85 % of the variation in settler abundance; (3) varying the temporal window over which data were aggregated increased the explanatory power of sea temperature to as much as 98 % for settlement and recruitment, and 86 % for colony cover; (4) exposure to waves and surface area of colonies improved relationships between sea temperature and settlement and recruitment by up to 11 %; and (5) recruit abundance was a strong predictor of colony cover, explaining as much as 89 % of the variation. Consistently low abundances of settlers and recruits at the northern tip of Newfoundland and southern tip of Labrador suggest that M. membranacea is nearing its northern distribution limit in the northwestern Atlantic. Our findings extend knowledge of population dynamics of M. membranacea in the northwestern Atlantic, while highlighting the complexity of the interactions between physical and biological factors and processes that affect population dynamics in invertebrates with planktonic larvae in predominantly cold marine habitats.

Decoupling of recruitment from adult clam assemblages along an estuarine shoreline

The maintenance of populations of benthic species requires both effective (if not regular) recruitment plus sufficient post-recruitment survival through vulnerable juvenile phases. Decoupling of abundances of settlers and adults often occurs when conditions for juvenile survival are poor. For infaunal bivalves, predation can be a key process that alters the abundance or distribution of adults relative to early recruits. We examined spatial patterns of recruitment of intertidal clams along the marine-estuarine axis in Puget Sound, Washington, USA. Abundances and species richness of clam recruits were variable in space and time, but during the period of high recruitment (summer) were equal across all sites. Juvenile and adult clams, however, were consistently rare at the inner-estuarine sites relative to the outer. We hypothesized that predation was higher at our inner sites, and manipulated predator access to newly recruited clam assemblages along the estuarine gradient. Predators >1cm were excluded with mesh net from intertidal PVC tubes where recruitment of clams was allowed to occur naturally, and abundances and species richness of clams were measured after one summer season. Tubes with mesh nets over the top had significantly higher overall abundances of clams than unprotected tubes after 4months, but showed no difference in clam species richness. More strikingly, the clam assemblage at the inner-estuarine sites comprised very few individuals relative to the outer-estuarine sites, regardless of predator exclusion. Multivariate analyses showed that clam assemblages in the tubes were better explained by position along the estuarine gradient than by predator treatment. Parallel studies at these sites suggested that growth of suspension feeders is actually higher in the inner estuary. Physical gradients are much less extreme in this well-mixed fjord than in many other estuaries, but we hypothesize that physical stresses such as higher temperatures at the inner beaches in the summer may be a major contributor to juvenile mortality, decoupling recruitment from adult populations.

Influence of intermittent-upwelling on Mytilus galloprovincialis settlement patterns in the Ría de Ares-Betanzos

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 443:111-127 (2011) - DOI: https://doi.org/10.3354/meps09433 Influence of intermittent-upwelling on Mytilus galloprovincialis settlement patterns in the Ría de Ares-Betanzos Laura G. Peteiro, Uxío Labarta*, Ma José Fernández-Reiriz, X. Antón Álvarez-Salgado, Ramón Filgueira, Silvia Piedracoba Consejo Superior de Investigaciones Científicas-Instituto de Investigacións Mariñas, Eduardo Cabello 6, 36208 Vigo, Spain *Email: labarta@iim.csic.es ABSTRACT: Coastal upwelling systems can directly or indirectly affect the population dynamics of marine invertebrates due to their influence on residual circulation patterns and biological production cycles. In the present study we evaluated the influence of shelf winds and continental runoff on settlement patterns of Mytilus galloprovincialis at 2 contrasting locations in an embayment (Ría de Ares-Betanzos) located at the northern boundary of the Iberian−Canary current upwelling system. We quantified settlement at 2 depths (1 and 6 m) every 15 d for a period of 2 yr at an outer location (Miranda) with direct oceanic influence and at an estuarine dominated site in the inner ría (Arnela). We explored the instantaneous and delayed (15 and 30 d) effects of the forcing variables to infer their influence at different times in larval development. The results showed a coupling between mussel settlement and the upwelling favourable season. Wind stress and Ekman transport along the main axis of the ría affected mussel settlement patterns significantly. Instantaneous and delayed responses showed the relevance of shelf winds at different larval developmental stages. Inverse patterns were observed between the inner and outer location in response to instantaneous winds. Onshore transport caused a decrease in settlement at Miranda, while only intense offshore transport showed a detrimental effect on settlement at Arnela. With regard to the 15 d delayed effect, maximum settlement abundances matched at both locations with transport values around zero. The 30 d delayed effect on settlement abundance showed a positive linear relationship with wind stress and Ekman transport at both locations. These relationships might be directly related to physical transport processes or indirectly associated with food availability and larval survival. KEY WORDS: Coastal upwelling · Mussel · Settlement · Galician rías · NW Spain Full text in pdf format PreviousNextCite this article as: Peteiro LG, Labarta U, Fernández-Reiriz MJ, Álvarez-Salgado XA, Filgueira R, Piedracoba S (2011) Influence of intermittent-upwelling on Mytilus galloprovincialis settlement patterns in the Ría de Ares-Betanzos. Mar Ecol Prog Ser 443:111-127. https://doi.org/10.3354/meps09433 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 443. Online publication date: December 20, 2011 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2011 Inter-Research.

Are numbers enough? Colonizer phenotype and abundance interact to affect population dynamics

1. Ecologists have long recognized that the number of colonizers entering a population can be a major driver of population dynamics, but still struggle to explain why the importance of colonizer supply varies so dramatically. While there are indications that differences in the phenotype among dispersing individuals could also be important to populations, the role of phenotypic variation relative to the number of individuals, and the extent to which they interact, remains unknown. 2. We simultaneously manipulated the phenotype (dispersal duration) and abundance of settlers of a marine bryozoan and measured subsequent population structure in the field. 3. Increases in the number of colonizing individuals increased the subsequent recruitment and biomass of populations, regardless of colonizer phenotype. However, the relationship between colonizer abundance and the subsequent reproductive yield of the population was strongly reduced in populations containing individuals that had long dispersal durations. 4. The interactive effects of colonizer phenotype and abundance on the reproductive yield of populations occurred because longer dispersal durations decreased the proportion of individuals that reproduced. In fact, populations established from a few individuals with short dispersal durations had similar reproductive yield to populations c. 30 times larger established from individuals with long dispersal durations. 5. Interactions between colonizer phenotype and abundance have important implications for predicting population dynamics beyond those previously provided by numerical abundance or recruit phenotype alone.

Supply-side ecology, barnacle recruitment, and rocky intertidal community dynamics: Do settlement surface and limpet disturbance matter?

The supply of new recruits can be a critical determinant of community structure, but estimating recruitment density can be challenging due to variation in larval supply, settlement, substratum, species interactions and physical stresses. We evaluated the effect of surface type and limpet “bulldozing” on settlement and recruitment of barnacles, using replicated field experiments sampled monthly at each of four sites along the central Oregon coast in 2001, 2003, and 2008. A particular goal was to evaluate the efficacy of Saf-T-Walk, a widely used textured surface, in quantifying actual patterns and levels of recruitment. In 2001 and 2003 experiments, surfaces were bare rock (ROCK) and Saf-T-Walk (STW). In 2008 experiments, to further evaluate the influence of surface rugosity, we added two additional artificial substratum types — smooth PVC plates (no texture) and travertine plates (TRAV, low texture). Limpet activity was manipulated using barriers of anti-fouling paint. Results indicated the overwhelming importance of surface texture. Recruitment density was highest in 2001, lower in 2003, and lowest in 2008. Recruitment on STW, the most textured surface, ranged up to 87 times greater than on ROCK, and the rank order of surfaces for recruitment density was STW > ROCK > TRAV > PVC which matches that for texture. Settlement differences were even greater, with up to 1180-fold higher settlement on STW than ROCK. Limpets usually had a negative effect on recruitment of Balanus glandula on ROCK, likely due to bulldozing and direct consumption, but had a positive effect on STW. These impacts were reduced or negated when recruitment density was higher (e.g., 2001) or lower than average (e.g., 2008). Limpets had no consistent effect on Chthamalus dalli. Abundances of settlers and recruits on the different surfaces were positively correlated (explaining up to 71% of the variance), and correlations between STW and other surfaces generally were stronger in the absence of limpets. Although compared to bare rock, recruitment to STW overestimates absolute rates of recruitment, use of STW settlement plates provides an effective and relatively efficient means of determining spatial and temporal patterns of recruitment at local to geographic scales.

Fine-scale spatial and temporal variation in settlement of the intertidal mussel Perna perna indicates differential hydrodynamic delivery of larvae to the shore

Scales of spatial and temporal variation in the settlement of early and late plantigrades of the mussel Perna perna to artificial substrata were measured on the south coast of South Africa. One study examined daily settlement over one month at three sites of similar tidal height and aspect. The sites were separated by 100′s of m with 5 replicated artificial settlement substrata approximately 1 m apart within each site. Early (< 0.5 mm) and large late plantigrades (1 - 3.5 mm) dominated samples with few individuals of 0.5-1 mm. Settler abundance showed clear peaks, synchronised among sites and apparently following spring tides, though the relationship between tide and settlement was not significant. Two-way ANOVA indicated significant spatial variation, which varied with time, at the 100 m-scale among sites. A second study investigated the local effects of substratum aspect. Seaward facing surfaces had consistently lower settlement (but higher adult cover) than horizontal and landward facing surfaces, this effect was significant for large late plantigrades. This suggests that either juveniles migrate after settlement, or that post-settlement mortality differs markedly among aspects. The high degree of temporal variation at the scale of days and weeks was expected, but the results also suggest a degree of pulsing in settlement, with maximum intensities around spring tide. A previous study of nearshore waters indicated a common pool of larvae at scales of 100 s m. Thus, consistent ranking of sites for all size classes of settlers indicates predictably differential hydrodynamic delivery of larvae to sites separated by 100 s m. The effect of aspect on settlement highlights the importance of smaller scale hydrodynamics, suggesting that the stronger turbulence experienced by seaward facing surfaces may affect larval settlement negatively.

Colonization process in soft-bottom macrofauna communities using azoic sediments: comparison of two wetland systems with different organic loads

The main goal of the study was to follow the colonization process of soft-bottom macrofauna commu- nities in two wetland systems with different organic inputs: a lagoon reservoir and a fish-farm system in the Ria Formosa, Portugal. After a previous treatment in the natural sediments, the resulting experimental azoic sediments were placed in suspended boxes. Two sets of boxes were used to study seven cumulative colonization periods of increasing duration, and seven colonization periods of one month each. Community structure was studied and percentage of organic matter in surface sediments was measured. Descriptors of the macrozoobenthic community included abundance, density, number of species, and diversity, dominance and evenness indices for polychaete taxa. Significant differences were observed in the community structure between colonization periods and between systems. Cumulative experiments revealed that organic enrichment is associated with sediment colonization which is marked by a macroinvertebrate community of increasing total abundance of settlers and diversity in the reser- voir, and several peaks for abundance of a few opportunistic polychaete species in the fish-farm which is typical of a highly disturbed system. Comparison of experimental and natural bottom sediments revealed that predation and organic inputs are important factors determining the community structure, for density in the case of predation and diversity in the case of organic loads. We observed that the duration of the colonization period is a key factor in the community structure of the less disturbed system, as shown by the higher diversity in bottom sediments of reservoir.

DEMOGRAPHIC CONSEQUENCES OF COALESCENCE IN SPORELING POPULATIONS OF MAZZAELLA LAMINARIOIDES (GIGARTINALES, RHODOPHYTA)(1).

Coalescing macroalgae are ecologically important members of intertidal and shallow subtidal communities. However, we still lack quantitative information on the demographic consequences of coalescence. Using demographic models developed for modular invertebrates, we studied the demography of settlement and early recruitment in the coalescing macroalga Mazzaella laminarioides (Bory) Fredericq. Permanently marked microscopic fields on laboratory-incubated and field-incubated plates were monitored regularly (at 15, 30, 45, and 60 d) using image analysis techniques to evaluate the relative importance of settler abundance, mortality, coalescence (fusion), and fission on the changes in size and numbers of recruits. On the plates, spores settled individually or in groups. Over time, spores in close proximity may coalesce, resulting in a mixture of unisporic and multisporic crusts. When new spores arrive, they may or may not coalesce with previously settled crusts. Coalescence and mortality reduce the number of sporelings, but coalescence increases the size of the sporelings, thereby reducing further probability of sporeling mortality. Crust fissions are negligible in frequency, while the frequency of coalescence increases from ∼25% after only 3 d, to ∼75% after 60 d. Thus, as a result of variable settlement, mortality, and coalescence, any area colonized by M.laminarioides would contain a mixture of crusts of different sizes, ages, and genetic constitution. The interactions between the above three processes create a more complex survivorship curve than the ones known for unitary organisms.

Temperature explains settlement patterns of the introduced bryozoan Membranipora membranacea in Nova Scotia, Canada

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 344:95-106 (2007) - DOI: https://doi.org/10.3354/meps06924 Temperature explains settlement patterns of the introduced bryozoan Membranipora membranacea in Nova Scotia, Canada Megan Saunders*, Anna Metaxas Department of Oceanography, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada *Email: msaunders@dal.ca ABSTRACT: Settlement is a critical life-history stage for benthic invertebrates with a planktonic larval form, and is important for understanding mechanisms of larval supply and population dynamics. We examined spatial (metre to kilometre scales) and temporal (weekly to yearly scales) patterns in abundance of settlers of the introduced bryozoan Membranipora membranacea on the numerically dominant kelp Saccharina longicruris, at 2 sites in St. Margarets Bay, Nova Scotia, Canada. Relationships between patterns in settlement and indices of the temperature regime, such as average weekly temperature, temperature fluctuations, water column stratification and thermal history (growing degree-day) were determined using multiple linear regressions. Although settler abundance varied interannually, it was highest in early autumn, and was generally higher at depth (12 and 8 m) than in the shallows (4 m). Abundance was an order of magnitude greater after a significantly warmer winter. Growing degree-day accounted for up to 81% of the variability in settler abundance, whereas average temperature, temperature fluctuations and stratification were less important. The strong positive relationship between thermal history and settlement of this ecologically important species suggests that abundance of established introduced marine species may increase with the increased temperatures predicted to result from climate change. KEY WORDS: Larval settlement · Temperature · Thermal history · Stratification · Bathymetric patterns · Benthic invertebrates · Introduced species · Climate change Full text in pdf format PreviousNextCite this article as: Saunders M, Metaxas A (2007) Temperature explains settlement patterns of the introduced bryozoan Membranipora membranacea in Nova Scotia, Canada. Mar Ecol Prog Ser 344:95-106. https://doi.org/10.3354/meps06924 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 344. Online publication date: August 23, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Variability in settlement and recruitment of 0-group dab Limanda limanda L. in Port Erin Bay, Irish Sea

Inter-annual variability in settlement and recruitment of 0-group dab Limanda limanda L. was investigated between 1996 and 2003 on Port Erin Bay, Isle of Man. The annual settlement index of post larvae dab (ind ≤ 20 mm) varied considerably between years with a corresponding coefficient of variation of 97%. The timing of the settlement of dab was associated with metamorphosis and varied significantly with temporal variation in estimated spawning activity. Inter-annual variation in the numbers of settling post larvae was strongly associated with stage one larvae abundance indices from adjacent offshore waters. 0-group abundance indices were significantly correlated with the index of settlement abundance, but not however, with larvae indices. These relationships suggest that the strength of the recruiting year-class of 0-group dab in Port Erin Bay is established early in life, during or before the pelagic phase, in the waters west of the Isle of Man. Inter-annual variability in 0-group mortality rates suggests a possible density-dependent process operating during the nursery ground phase.

SELF-REGULATING MECHANISMS IN CANNIBALISTIC POPULATIONS OF JUVENILE SHORE CRABS CARCINUS MAENAS

Juvenile cannibalism may play an important role in population regulation of marine organisms with juvenile stages that aggregate in nursery habitats. I conducted a series of field and laboratory experiments to assess whether three potential density-dependent mechanisms could regulate local recruitment of juvenile shore crabs Carcinus maenas in Swedish nursery areas: (1) intracohort cannibalism, (2) juvenile cannibals' functional response to smaller conspecific prey densities, and (3) juvenile cannibals' numerical effect on prey survival. Juvenile cannibals in mesocosms displayed a type III (sigmoid) density-dependent functional response, resulting in significantly higher proportional mortality of smaller conspecifics at high prey densities. Consistent with the laboratory result, cage-enclosed juvenile cannibals in a field experiment eliminated conspecific settlement peaks in mussel habitats and decoupled the relationship between larval and settlement abundance within three days. Density-dependent interference between cannibals in mesocosms decreased per capita predation rates, but conspecific prey mortality still increased with cannibal densities when the abundance of cannibals passed a critical threshold, suggesting that the recruitment success of consecutive cohorts may be negatively correlated. This was supported in a field experiment where the abundance of juvenile cannibals explained 71% of the variation in settlement loss from uncaged mussel habitats. Density-dependent cannibalism also occurred within juvenile cohorts even though food was provided in excess, but the resulting mortality was too low to eliminate initial density patterns over a 30-day period. The results demonstrate that cannibalism between juvenile shore crabs can cause high and strongly density-dependent mortality at natural densities, and that both a functional response and a numerical effect of larger cannibals can regulate the recruitment of new cohorts within days of settlement. A coupling of cannibal and settlement densities on a regional scale is expected to decrease recruitment variability within and between local populations. Moreover, the interaction between the type III functional response, mutual interference, and density-dependent dispersal of cannibals is predicted to reduce cannibalistic rates at low prey and high cannibal densities, respectively, and stabilize local population dynamics in relation to the abundance of juvenile habitats, consistent with field observations of shore crab populations in the study area.

Temporal and spatial settlement patterns of sympatric hermit crabs and the influence of shell resource availability

Larvae of marine organisms often need specific resources or environments at settlement, and their success at settlement might be strongly influenced by the abundance and distribution of such specific resources. The larvae of hermit crabs need small shells to settle, so it is thought that the distribution and abundance of small shells influence the settlement pattern of hermit crabs. To investigate the influence of small shell distribution on the settlement of pagurid hermit crab larvae, we conducted a field experiment at an intertidal rocky shore in Hakodate Bay, Japan. From the line-transect sampling in the field, we found that Pagurus middendorffii settled extensively in the offshore side of the intertidal zone while P. nigrofascia settled in the uppermost area of the intertidal zone. Small shells were most abundant in a narrow shallow trough, slightly offshore from the uppermost area of the intertidal zone. For both species, settler abundance was high where adults were abundant, but settler abundance did not appear to be related to shells abundance. An experiment to clarify settlement patterns showed that larval recruits tended to be similar to those in the line-transect sampling of settlers. Thus shells may not be a primary factor affecting settlement patterns at relatively large scale within the intertidal flat. However, when we analyzed the relationship of settlers and shells separately within each transect, the distribution of settlers was well explained by shell resource availability. Therefore on a smaller scale, shell availability may influence the number of settlers. Settlement periods of P. middendorffii and P. nigrofascia fully overlapped, so their larvae probably were affected by similar transport factors, such as current and tidal movement. Nevertheless they showed different spatial patterns of settlement.