The fate of recently settled populations of soft-bottom invertebrates depends not only on dispersal of pelagic larvae by tidal currents but also on other physical (
e. g. resuspension) and biological ...mechanisms (
e.g. habitat selection and adult-recruit interactions) acting at the water-substratum interface. To assess the relative importance of such processes under megatidal conditions in the
Abra alba community of the eastern Baie de Seine (English Channel), flume experiments were conducted on post-larvae of the dominant polychaete species,
Pectinaria koreni. Habitat selection by post-larvae of
P. koreni was determined in a first set of experiments, where individuals were sowed either on a suitable or on an unsuitable substratum. Once resuspended, post-larvae were given a choice between two highly contrasting treatments with a natural organic-rich muddy sand and a bare flat PVC surface.
P. koreni post-larvae were able to leave an unfavourable substratum into which they had initially burrowed and reach a more suitable substrate by drifting (induced by the secretion of mucus) before final settlement. The influence of adults on habitat selection and survival of
P. koreni post-larvae was analysed in a second set of experiments, where individuals were sowed onto a suitable sediment with adults (test treatment) or without (control treatment). The presence of conspecific adults induced a high resuspension rate of the post-larvae. Drifting occurred mainly just after the introduction of the current and affected the whole experimental population, regardless of size. Such a response seems to be related to the intense bioturbation caused by the sub-surface deposit-feeding habit of the adults, which alters the boundary-layer flow. In contrast, the presence of adults of
Owenia fusiformis, another dominant polychaete of the
Abra alba community, led to an enhanced recruitment by a reduction in post-larvae resuspension. In fact, at low shear velocities, dense aggregates of tubes stabilize the sediment and so act as particle traps. Thus, in the megatidal environment of the Baie de Seine, physical conditions and behavioural responses interact and contribute to structuring the benthic community.
Recent investigations on the recruitment of marine benthic invertebrates have highlighted the ability of postlarval and juvenile stages to re-enter the water column and undergo a consequent dispersal ...following primary settlement. In the eastern part of the Bay of Seine (English Channel), abundances of Pectinaria koreni postlarvae within the water column were measured hourly at 1 station over 2 time series of 93 and 92 h conducted in May 1991 and 1992 to determine the magnitude and frequency of postlarval transport and its dependency on current velocity and bottom shear stress. Postlarval numbers varied strongly with the state of the tide; mean densities were consistently larger, by at least one order of magnitude, during flood than during ebb. Maximum densities were observed with about a 2 h delay relative to the tidal current speed and bottom shear stress maxima. No diurnal rhythm of migratory activity was observed. The interaction of postlarval drifting and tide generates a net landward transport which could partly reduce the demographic consequences of larval dispersal. This mechanism is proposed to be one of the major processes which explain the spatial and temporal stability of the adult population in a highly advective and dispersive environment. The potential effects of other environmental factors (e.g. wind events) are also discussed.
The distribution of
Pectinaria korenilarvae in the Seine river plume was studied in June 1992 in the course of three inshore–offshore transects. Plume waters were characterized by a higher turbidity ...and a well-developed phytoplankton biomass. The hydrological structure varied greatly among surveys, principally due to lunar tidal cycle and wind events.
Pectinaria korenilarval densities were consistently larger, by at least one order of magnitude, in plume waters than they were in ambient shelf waters. The frontal structure of the plume, acting as a physical boundary, may favour transport along a coastal band which offers rich trophic resources and limits offshore export. Nonetheless, some mixing processes were observed between water masses. Wind events were also able to break up the front and induce a large-scale dispersal of larvae. In frontal zones, larval and phytoplankton aggregation was quite variable and this cannot be explained by a calculated index of potential convergent velocities.
The distribution of Pectinaria koreni larvae in the Seine River plume was studied in June 1992 in the course of three inshore-offshore transects. Plume waters were characterized by a higher turbidity ...and a well-developed phytoplankton biomass. The hydrological structure varied greatly among surveys, principally due to lunar tidal cycle and wind events. Pectinaria koreni larval densities were consistently larger, by at least one order of magnitude, in plume waters than they were in ambient shelf waters. The frontal structure of the plume, acting as a physical boundary, may favour transport along a coastal band which offers rich trophic resources and limits offshore export. Nonetheless, some mixing processes were observed between water masses. Wind events were also able to break up the front and induce a large-scale dispersal of larvae. In frontal zones, larval and phytoplankton aggregation was quite variable and this cannot be explained by a calculated index of potential convergent velocities.
We report on the isolation of dinucleotide microsatellites from the polychaete Pectinaria koreni using (GT)(10) and (CT)(10) olignonucleotide probes. Compound and particularly imperfect ...microsatellites are predominant in this species. In most cases the associated element is (AT)(n) leading to AT microsatellites being the most frequent class after GT repeats. Obtaining single-copy polymerase chain reaction products in the expected size range proved to be difficult, and only 24% of the primer pairs tested produced polymorphic single-locus markers. We obtained five highly variable loci with 16 to 41 alleles and an observed heterozygosity ranging from 0.29 to 0.81. Amplifications have also been obtained from the earliest postlarval stage. These highly informative markers will allow studies of the population structure of P. koreni at fine spatial and temporal scales.
In the Bay of Seine (English Channel) the polychaete Pectinaria koreni exhibits interannual stability in its abundance, despite its isolated distribution and its bentho-planktonic life cycle. To test ...the hypothesis of a high level of recruitment related to high survival rate of the post-larvae due to metamorphosis in the water column (transformation of metatrochophore into aulophore), we undertook a study of the morphology and the dynamics of the aulophore stage during May and June 1987. The morphological study showed that aulophore larvae do not possess all the morphological features needed for benthic life on their first contact with the substratum. Fifteen days are needed to complete this development, and during this time the mortality rate is high. The possible role of this delayed metamorphosis on the transport of aulophore larvae towards sites favourable to adults is also discussed.
Pectinaria (Lagis) koreni (Malmgren) is an abundant, deposit-feeding, infaunal inhabitant of shallow-water marine environments in northern Europe. Laboratory experiments were performed to quantify ...the polychaete's sediment processing in 2 distinct sediments, 1 fine-grained and high in combustibles, the other coarse-grained and low in combustibles. Gut passage time and time to pseudodefecation were predictable only in coarse-grained sediment. In both sediments, reworking rate increased with worm size and over time, although temporal patterns differed in the 2 sediments. The ratio of pseudodefecated sediment to defecated sediment did not differ significantly over time in either sediment, but the ratio was greater in the fine-grained sediment during the first measurement period. Another thrust of this study was to investigate possible size-selective ingestion of sediment particles by P. koreni. Results corroborated previous workers' findings that pectinariids selectively ingest large particles, a behavior at variance with current perceptions of optimal foraging by deposit feeders. These experiments were supplemented by natural history observations of the worm's infaunal behavior and particle-handling techniques.
Materials of YugNIRO on trophic structure and species diversity of Polychaete community in various biotopes of the Kerch Strait in the Black Sea are given. The highest number of Polychaete was traced ...in the silt, the lowest one - on the sand - is 5.4±1.6 times less. The lowest biomass is in the sand biotopes.
Изложен имеющийся в ЮгНИРО материал по трофической структуре и видовому богатству сообщества полихет в различных биотопах Керченского предпроливья Черного моря.
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