High Larval Concentrations and Onshore Transport of Barnacle Cyprids Associated With Thermal Stratification

To better understand the hydrodynamic and hydrographic conditions experienced by larvae in the nearshore (within 1 km of shore), and the role that larval behavior plays in mediating shoreward transport to adult benthic habitats, we examined the vertical distribution and concentration of barnacle cyprids in a shallow, nearshore region in southern California, United States. We collected high-resolution physical measurements of currents and temperature at 3 stations (8, 5, and 4 m depths), and high-frequency measurements of barnacle larvae at a 4 m deep station ∼300 m from shore. Larvae were sampled from distinct 1 m depth intervals between the surface and the bottom (0–1 m, 1–2 m, 2–3 m, 3 m-bottom), each hour for overnight periods that ranged between 13 to 24 h in five cruises during the summers of 2017 and 2018. Barnacle cyprids of Chthamalus fissus predominated in all samples. Thermal stratification decreased closer to shore, but when the nearshore-most station remained stratified (Δ°C m–1 ≥ 0.1), C. fissus cyprid concentrations were high to extremely abundant (exceeding 200 and 4,000 individuals m–3, respectively). There were significant positive correlations between thermal stratification and the log-transformed C. fissus concentration at cruise-to-cruise scales, and between stratification and vertical variability in the high-frequency cross-shore currents at 2-day scales. Additionally, estimated larval transport was relatively high and shoreward when nearshore thermal stratification was greatest. Significant, albeit small, diel differences in cyprid distributions were also observed, with the proportion of cyprids increasing near the surface at night, and concentrations greater during the day than at night. Collectively, these results suggest that thermal stratification increases larval supply to the nearshore, and may enhance onshore larval transport to augment chances of successful settlement and recruitment to the intertidal adult habitat.

A gigantic deep-sea Nucinellidae from the tropical West Pacific (Bivalvia: Protobranchia)

Nucinella boucheti n. sp. is described from a 1610–1580 m deep station in the Philippines (Musorstom 2 Expedition). Nucinellids are typically small, mostly not exceeding 5 mm, but the present species is 25 mm large, being by far the largest nucinellid so far known. The adaptive meaning of this case of gigantism remains open to speculation, but it may be an expression of a rapid diversification of the Holocene nucinellids. Nucinella boucheti n. sp. has numerous, thin and delicate subumbonal teeth, displaying a number of unusual shapes and contrasting with the few, rather coarse and stout teeth of the other nucinellids. This feature is believed to be due to allometric constraints related to the large size. With N. boucheti, 19 living species of nucinellids are known, 14 of which belonging to the genus Nucinella. The Central West Pacific, from Japan to South Australia, is the area with the maximum diversity of nucinellids (11 species).

A Broad Review of Variability and Persistence in the Northumberland Benthic Fauna – 1971–85

The long-term monitoring of two stations, 55 and 80 m depth, from 1971 to 1985 shows clear evidence of periods of stability interspersed with periods of change. These periods were identified by several different multivariate methods and persistence stability was quantified by the use of a between years similarity index. A short period of change at the shallow station, 1972–3, was followed by a prolonged period of stability 1974–80. The period 1981–3 witnessed a second period of change with rising total numbers and biomass with some evidence of a downward reversal in 1984–5. The deep station exhibited an essentially similar response except that the stable period 1974–80 was broken into two sub-periods 1974–6 and 1978–80 due to sequential changes in the dominant species which were regarded as evidence of biological interaction with the activities of the polychaete Ophelina acuminata possibly playing a key role. The shallow station showed little evidence of biological interaction and the majority of the species have exhibited similar responses throughout. The general rise in numbers and biomass at both stations is regarded as evidence of intermittent changes in organic flux to the bottom from the water column. The winter temperature fluctuations were shown to have short-term, but significant, effects on the diversity of the communities, bringing about year to year changes in the equitability and dominance.

Secondary production of four sublittoral, soft-sediment amphipod populations in the Bay of Fundy

Estimates of secondary production by cohort summation of losses and size–frequency methods were made on the four most abundant amphipods at an 80 m deep station on a soft sediment in the southwestern mouth of the Bay of Fundy. Production and annual turnover ratios (production:biomass ratio (P:B), in parentheses) for the 1978 year class, expressed as grams wet preserved weight per square metre per year, were as follows: Haploops fundiensis, 0.505 (1.3); Photis reinhardi, 0.370 (2.8); Casco bigelowi, 1.210 (2.5); Harpinia propinqua 0.066 (3.1). The P:B ratios found were closest to those calculated by the empirical method of Robertson when an accurate estimate of life-span was available.

Seasonal salinty variations in Cleveland Bay, northern Queensland

Weekly salinity measurements have been collected over 34 months at a 10 m deep station in Cleveland Bay. Minimum salinity during the summer wet season varied considerably from year to year and was mainly dependent on the discharge of small local rivers and the Burdekin River to the south-east. During the dry months, evaporative concentration generated a gradient of decreasing salinity from the shore across the continental shelf.

Annual temperature cycle in Cleveland Bay, Great Barrier Reef province

Weekly temperature measurements have been taken over a 55-month period at a 10 m deep station in Cleveland Bay. Temperature at the surface ranged from 19.3 to 30.9�C with a mean monthly minimum of 20.9�C in July and a mean monthly maximum of 29.0�C in January. The water-temperature curve lagged behind the 0900 h air-temperature curve by an average of 10 days. Differences between the present data and other published temperature data for Great Barrier Reef waters are discussed.