Larvae of ~100 species of benthic invertebrates were obtained from the vicinity of Tomales Bay and Dillon Beach, California, over a 6-year period (1971–1977). This study reports on larvae of 14 species in eight families of polychaetes: Micronereis nanaimoensis, Nereis vexillosa, Sthenelais fusca, Nephtys caecoides, Nephtys californiensis, Boccardia berkeleyorum, Polydora pygidialis, Polydora spongicola, Dipolydora cardalia, Mediomastus californiensis, Ampharete labrops, Phragmatopoma californica, Sabellaria cementarium and Pectinaria californiensis. Some species were cultured from embryos obtained from laboratory fertilizations or field-collected egg masses or capsules. Larvae of other species were obtained from meroplankton and some of these were cultured through metamorphosis. A summary table is presented documenting seasonal occurrence of 60 polychaete taxa in the meroplankton.

Polychaete abundance and assemblage structure were analysed from 144 zooplankton samples taken in eight seasonal campaigns between October 2007 and November 2008 on Babitonga Bay estuary (south Brazil). A total of 16 taxa were found, classified in three categories: (i) larvae (five taxa) dominated by Loimia sp. (Terebellidae) (up to 59 ind 100 m−3); (ii) syllid epitokes (three taxa) dominated by Procerastea sp.2 (up to 11 ind 100 m−3) and Myrianida sp. (up to 6 ind 100 m−3); and (iii) adults of typically benthic species (eight taxa) which were only occasionally sampled in low densities (<1 ind 100m−3). Larvae dominated mostly during spring and summer in the outer sector of the estuary, while syllid epitokes peaked during winter with higher abundances in the inner sector. The assemblage dynamics match the seasonal and spatial changes in the environmental conditions of the estuary. Descriptive variables explained 49.5% of the polychaetes variance according to Redundancy Analysis. Rainfall, temperature and salinity were the variables most influencing the assemblage, with rainfall and temperature regulating seasonal, and mostly salinity regulating spatial patterns, similar to meroplanktonic populations from both temperate and tropical latitudes. Dominant species had different hydrographic preferences, Loimia sp. was more abundant in warmer (>23°C) and saltier (>25) waters, Magelona papillicornis larvae were more abundant in saltier waters with intermediate temperatures (22–23°C), and the syllids were more common and abundant on lower temperatures (<20°C). In addition we highlight the occurrence of several benthic taxa suspended in the water column, probably due to bottom disturbance.

Larval survival during planktonic dispersal is crucial to the connectivity among benthic populations. Although predation has been suggested as an important cause of larval mortality, this process has rarely been quantified in the field. We measured the abundance of various larval species in the water column in St George’s Bay, Nova Scotia, Canada, on 3 different occasions in summer (August 2008, July and August 2009), the period of high larval abundance in our region. We sampled four numerically dominant predators (scyphozoans: Cyanea capillata and Aurelia aurita; fishes: Gasterosteus aculeatus and Merluccius bilinearis) and lobster larvae near the water surface with a neuston net and other larval species in the water column (3 m depth) with a ring net. Larvae found in the gut contents of the predators included various species of gastropods, crustaceans and bivalves, and these were more abundant in the scyphozoans than the fishes. We attribute these differences to variation in predation method. For certain larval taxa, we found significant differences between the proportional abundance in the guts of C. capillata and in the water column, indicating prey selectivity. This study evaluates the potential impact of predation on larval survival and indicates that the presence of predators can cause changes in abundance and consequent taxonomic shifts in species dominance of larvae, influencing their successful subsequent recruitment to the benthos.

Although thalassinidean shrimps exert considerable influence over the structure of benthic communities no ecological studies have been conducted on the larvae and adults of Lepidophthalmus siriboia and Upogebia vasquezi in the equatorial region. The aim of the present study was to identify the reproductive period of these species in an Amazonian estuary. Monthly collections were performed in the estuary of the Marapanim River (northern coast of Brazil) over the course of one year (August 2006 to July 2007) and adults were obtained from bare sandy substrate and between boulders in the intertidal zone of the estuary at four sites. Thalassinidean larvae were also sorted from plankton samples (200 μm mesh) collected monthly at six sites. Larvae of the species Callichirus major, Lepidophthalmus siriboia and Upogebia vasquezi were collected, whereas adults of only the latter two species were found. Upogebia vasquezi was the most abundant species. There was no correlation between larval density and abiotic factors (water temperature, salinity and pH); however, the density of U. vasquezi adults was negatively correlated with salinity in the burrows. Lepidophthalmus siriboia and U. vasquezi reproduce throughout the year in the Marapanim River estuary, with peaks of greater intensity in some reproductive periods of the year, mainly correlated with changes in salinity.

The patterns of decapod larvae occurrence and abundance were studied from weekly time-series data of 8 years from Stonehaven (north-east Scotland) and 4 years and 8 months from Loch Ewe (north-west Scotland). The annual cycle observed was similar in the two locations and characterized by abundance peaks, the first in spring and another in the summer, extending into autumn. During the coldest months (December to February) decapod larvae were virtually absent in the plankton. Differences in abundance and occurrence of decapod larvae between locations and the influence of temperature, salinity and chlorophyll-a in the patterns observed, were analysed by generalized least-square functions. The results showed significant differences in the abundance of decapod larvae between locations, with higher larval abundances and an earlier appearance in the plankton in Loch Ewe (west coast). In Stonehaven (east coast), from 2003 onwards, a general increasing trend in the abundance of decapod larvae was observed, related to the increasing temperatures recorded at that site. The data demonstrate the high variability of decapod larval abundance on an annual basis and the high importance of temperature and chlorophyll-a to the occurrence and abundance of decapod larvae.

Larval stages of protozoeas II and III and zoea I of Aristeus antennatus were found in low numbers near the red shrimp fishing grounds off the Balearic Islands. The discovery of the larvae in the upper water layers has led to a proposed model of reproductive dynamics, in which newly hatched larvae perform an ontogenetic migration up through the water column to surface waters, where the larval stages develop. Data on the horizontal distribution of larvae presented, can contribute to an understanding of the dynamics processes of larval dispersal of the zoeal stages.

The study presents dry mass and body measurements of the larval stages of five common barnacle species occurring in mesozooplankton catches of Southampton Water and the central Solent area of the south coast of the UK. Quantitative samples were collected with conventional 120-μm mesh plankton nets. Species-specific regression equations relating carapace width and total length with dry mass were obtained for stage II to stage VI nauplii and cyprids of Austrominius modestus, Amphibalanus improvisus, Balanus crenatus, Semibalanus balanoides and Verruca stroemia. Width–dry mass and length–dry mass regressions obtained in the present study accounted for more than 98% of the variability for naupliar stages, and length–dry mass for 80% of the variability for cyprids. The dry mass of barnacle larvae predicted from carapace width equations determined here differed by only –6% from the measured dry masses of an independent data set, suggesting these first-reported equations of barnacle larvae are useful additions to zooplankton production studies.

Temporal, spatial and diel variation in the distribution and abundance of organisms is an inherent property of ecological systems. The present study describes these variations and the composition of decapod larvae from the surface waters of St Paul's Rocks. The expeditions to the archipelago were carried out in April, August and November 2003, March 2004 and May 2005. Surface plankton samples were collected during the morning and dusk periods, inside the inlet and in increasing distances around the archipelago (~150, 700 and 1500 m). The identification resulted in 51 taxa. Seven species, six genera and larvae of the families Pandalidae and Portunidae were identified for the first time in the area. The mean larval density varied from zero to 150.2±69.6 individuals 100 m−3 in the waters surrounding the archipelago and from 1.7±3.0 to 12,827±15,073 individuals 100 m−3 inside the inlet. Significant differences on larval density were verified between months and period of the day, but not among the three sites around the archipelago. Cluster and non-metric multidimensional scaling analysis indicated that the decapod larvae community was divided into benthic and pelagic assemblages. Indicator species analysis (ISA) showed that six Brachyura taxa were good indicators for the inlet, while three sergestids were the main species from the waters around the archipelago. These results suggest that St Paul's Rocks can be divided into two habitats, based on larval composition, density and diversity values: the inlet and the waters surrounding the archipelago.