Egg production and early development of the subarctic copepods Neocalanus cristatus,N. plumchrus and N. flemingeri

Reproduction and early development of the large subarctic copepods Neocalanus cristatus, N. plumchrus and N. flemingeri were investigated in the laboratory. All three species produced eggs at intervals of 5.0 to 14.7 days, depending on species and temperature. The females of N. flemingeri released the fewest clutches of the three species, but with the largest clutch size. Clutch size of N. cristatus was smallest with longest intervals between clutches. Mean±1 S.E. of total fecundities were 386±116 eggs for N. cristatus, 840±214 eggs for N. plumchrus, and 924±346 eggs for N. flemingeri. The egg laying period of a female at 2°C was estimated to be 91 days for N. cristatus, 60 days for N. plumchrus and 47 days for N. flemingeri. The color and outer characteristics of eggs and nauplii of these species were quite different. C : N ratios of the eggs were 9.3–10.5, which were slightly higher than that of females or CV. Egg hatching times for each species were 4.6–5.7 days at 2°C and decreased with increasing temperature at a Q₁₀ of 2.8–3.0. N. cristatus nauplii developed to copepodid stage I (CI) without feeding, and the developmental time in days from hatching to CI was expressed as a Bělehrádek equation, D_CI=17068×(T+14.7)^−2.05. Reproduction strategies of the three species of Neocalanus are discussed with reference to their life history strategies.     

Jurassic subsidence history in the Hebrides,N.W. Scotland

Geohistory analyses have been applied to the generally well-dated Triassic-Jurassic successions of three areas in the Hebrides Basin, north-west Scotland, and the importance of making corrections for decompaction, palaeobathymetry and eustatic changes of sea level are assessed. The thermo-tectonic subsidence patterns in the Skye areas (north) suggest a three-phase history of crustal stretching, though only the first phase is well developed in the Mull area (south).Episodes of relatively rapid subsidence are:

• 1.(1) Late Triassic (c210 Ma) until earliest Toarcian (186 Ma);
• 2.(2) Latest Toarcian (180 Ma) until late Bathonian (c161 Ma);
• 3.(3) Early Oxfordian (154) Ma) until at least early Kimmeridgian (incomplete.).

These are separated by Toarcian (186-180 Ma) and latest Bathonian-Callovian(c161-154 Ma) episodes of either little subsidence or of uplift (but at slower rates than eustatic rise of sea level). The intervals between phases, at 30 Ma and 26 Ma, are remarkably similar but the wider significance of this remains to be established.     

Geographical Variation of Body Size of Neocalanus cristatus, N. plumchrus and N. flemingeri in the Subarctic Pacific and Its Marginal Seas: Implications for the Origin of Large Form of N. flemingeri in the Oyashio Area

Size distributions of Neocalanus cristatus, N. flemingeri and N. plumchrus were investigated in the eastern and the western subarctic gyres and three marginal seas of the North Pacific during the diapause period to examine the geographical variation in body size of Neocalanus species and to clarify the origin of the large biennial N. flemingeri which has been observed in the Oyashio region. There were significant among region variations in body sizes for all three species of Neocalanus. Generally, the body sizes of the copepods were larger in the marginal seas and marginal areas of the open ocean. In the open ocean, the body sizes increased westward. These patterns of variation in the body sizes roughly correlated with local food availability. Distribution of biennial N. flemingeri was restricted to the Sea of Japan, the Okhotsk Sea and the Oyashio region. The large-sized biennial N. flemingeri were abundantly observed in the Okhotsk Sea, and the medium-sized biennial individuals were observed in the Sea of Japan. These facts strongly suggest that the large biennial N. flemingeri in the Oyashio region are advected from the Okhotsk Sea.     

Sedimentary environments and Pleistocene chronology of the Botany Basin,N.S.W., Australia

The sedimentary sequence of the Pleistocene deposits of the Botany Basin were investigated using borehole samples and seismic data. A succession of environments from marine to terrestrial, separated by erosional surfaces, were recognized and, although absolute dating is not possible, a relative “minimum” chronology was established correlating erosional surfaces with sea-level fluctuations. Seismic surveys and borehole material from other sites indicate that the model presented here is applicable to other estuaries of N.S.W.     

Models of Climate,Geophysical Boundary Layers,and the Active Land Layer: In Memory of V. N. Lykosov

Izvestiya, Atmospheric and Oceanic Physics - This paper is dedicated to the memory of Vasily Nikolaevich Lykosov, a prominent Russian scientist and a specialist in the field of mathematical...     

Late Holocene coastal sand movements in the Outer Hebrides, N.W. Scotland

Lithostratigraphical and biostratigraphical investigation of coastal marshes along the Atlantic coast of the Outer Hebrides from Lewis in the north to Barra in the south discloses inland-tapering sand units within marshland areas. The inland extent of each sand unit has been radiometrically dated and the units have been collectively interpreted as a proxy for past coastal storminess. The data appear to indicate that for the study sites investigated, the majority of the sand units were produced during episodes of climate deterioration both prior to and after the well-known period of Medieval warmth (MWP). Many were produced after ca. AD 1400. It is argued that the episodes of sand blow indicated by the deposits may reflect periods of increased cyclogenesis in the Atlantic associated with increased sea ice cover and an increase in the thermal gradient across the North Atlantic region.     

Sources and timing of trace metal contamination to sediments in remote sealochs,N.W. Scotland

Sediment cores from a transect of sealochs, Etive, Sunart, Nevis, Duich, Broom and Torridon in N.W. Scotland were analysed for the trace metals lead, copper, and zinc. In addition, sediment cores from the Clyde Sea Basin (Loch Fyne, the Gareloch, Clyde dumpsite) and from the Irish and Celtic Seas were analysed as possible source areas for contaminated particles. The sediment cores were dated using excess ²¹⁰Pb and ¹³⁷Cs, and Al normalisation was used to correct for sediment compositional effects. All cores showed increased concentrations of all trace metals (and M/Al) towards the surface, with a maximum of 280–500% above background being observed in Loch Etive. Only cores from Duich and Torridon (Zn/Al and Pb/Al) and Etive (Zn/Al) did not continue to show an increase in trace metals to the uppermost samples. The burden of atmospherically derived trace metals accumulated over the past 100 years was compared with similar published burdens from a series of freshwater lochs adjacent to the sealochs. Plots of excess ²¹⁰Pb (used to correct for sediment focusing) against atmospherically derived Pb showed a series of linear relationships of systematically decreasing gradient towards the north-west, away from potential urban sources of lead. It was calculated that 49% (15–77%) of the Pb but only 3% (1–4%) of the Zn and 2% (0–3%) of the Cu reached the sealochs from atmospheric sources. The remaining trace metals deposited in the sealochs came from marine particles. Using trace metal ratios as an indicator of pollutant provenance, it was shown that the trace metals came predominantly from the Irish Sea. There was no evidence of trace metals derived from the Firth of Clyde basin. It was concluded that trace metal contamination from the Clyde and the surrounding industrialised urban area was mainly deposited in the estuary and the Clyde Sea basin with its adjoining sealochs, such as the Gareloch and Loch Fyne.     

Recent sediments, sediment accumulation and carbon burial at Goban Spur, N.W. European Continental Margin (47–50°N)

To quantify recent sediment accumulation, carbon fluxes and cycling, three N.W. European Continental Margin transects on Goban Spur and Meriadzek Terrace were extensively studied by repeated box- and multicore sampling of bottom sediments. The recent sediment distribution and characteristics appear directly related to the near-bed hydrodynamic regime on the margin, which at the upper slope break on the Goban Spur results in along-slope and periodic off-slope directed transport of particles, possibly by entrainment of particles in a detached bottom or intermediate nepheloid layer. From the shelf to the abyssal plain the surface sediments on the Goban Spur change from terrigenous sandy shelf sediments into clayey silts. ²¹⁰Pb activity decreases exponentially down core, reaching a stable background value at 10 cm (shallower stations) to 5 cm (deeper stations) sediment depth. ²¹⁰Pb profiles of repeatedly sampled stations indicate negligible annual variability of mixing and flux. The ²¹⁰Pb_xs flux to the sediment shows a decreasing trend with increasing water depth. Below about 2000 m the average ²¹⁰Pb_xs flux is about 0.3 dpm cm⁻² y⁻¹, a third of the fluxes measured on the shelf and upper slope stations. Sediment mixing rates (D_b) correlate with macro- and meiofaunal density changes and are within the normal oceanic ranges. Lower mixing rates on the lower slope likely reflect lower organic carbon fluxes there. Mass accumulation rates on Meriadzek Terrace are at maximum 80 g m⁻² y⁻¹, almost twice as high as at Goban Spur stations of comparable depth. A minimum accumulation rate of 16.6 g m⁻² y⁻¹ is found at the Goban Spur upper slope break. Organic carbon burial rates are low compared to other margins and range from a lowest value of 0.05 g m⁻² y⁻¹ at the upper slope break to 0.11 g m⁻² y⁻¹ downslope. A maximum organic carbon burial rate of 0.41 g m⁻² y⁻¹ is found on Meriadzek Terrace. Carbonate burial rates increase along the northern transect from the shelf (13 g m⁻² y⁻¹) via a low (9.3 g m⁻² y⁻¹) on the upper slope break to the deep sea (30.7 g m⁻² y⁻¹). Carbonate burial is highest on Meriadzek Terrace (44.5 g m⁻² y⁻¹). The N.W. European Margin at Goban Spur and Meriadzek Terrace cannot be considered a major carbon depocenter.     

北部湾金线鱼、深水金线鱼与日本金线鱼矢耳石形态识别的初步研究

采用2010年1～9月采自北部湾及邻近海域流刺网渔获的54尾金线鱼(Nemipterus virgatus( Houttuyn,1782))、71尾深水金线鱼(Nemi pterus bath ybius Snyder,1911)和65尾日本金线鱼(Nemi pterus ja ponicus (Bloch,1791))耳石样本,进行了椭圆傅立叶分析.耳石轮廓经图像处理后进行灰阶转换和二值化处理,消除噪点,然后解析为椭圆傅立叶标码( EFDs).采用77个EFD系数进行主成分分析和判别分析来区分3种金线鱼的耳石.结果表明,日本金线鱼幼鱼和成鱼耳石在性成熟前后存在显著的体长效应(P＜0.05),金线鱼和深水金线鱼则体长效应不显著(P＞0.05).因此在耳石椭圆傅立叶分析中,日本金线鱼采用性成熟个体样本,金线鱼和深水金线鱼采用全部样本.主成分分析中,第1、第2和第3主成分,分别解释了总变异的65.1％,15.3％和5.3％,可以将3种金线鱼耳石区分开来.EFD系数的逐步判别分析中,3种鱼的平均正判率达98.6％;交互验证结果显示,3种鱼的平均正判率达97.9％,这表明耳石椭圆傅立叶分析可以作为鱼种识别的有效工具.     

Depth-related distribution and abundance of seastars (Echinodermata: Asteroidea) in the Porcupine Seabight and Porcupine Abyssal Plain,N.E. Atlantic

The depth-related distribution of seastar (Echinodermata: Asteroidea) species between 150 and 4950 m in the Porcupine Seabight and Porcupine Abyssal Plain is described. 47 species of asteroid were identified from ∼14,000 individuals collected. The bathymetric range of each species is recorded. What are considered quantitative data, from an acoustically monitored epibenthic sledge and supplementary data from otter trawls, are used to display the relative abundance of individuals within their bathymetric range. Asteroid species are found to have very narrow centres of distribution in which they are abundant, despite much wider total adult depth ranges. Centres of distribution may be skewed. This might result from competition for resources or be related to the occurrence of favourable habitats at particular depths. The bathymetric distributions of the juveniles of some species extend outside the adult depth ranges. There is a distinct pattern of zonation with two major regions of faunal change and six distinct zones. An upper slope zone ranges from 150 to ∼700 m depth, an upper bathyal zone between 700 and 1100 m, a mid-bathyal zone from 1100 to1700 m and a lower bathyal zone between 1700 and 2500 m. Below 2500 m the lower continental slope and continental rise have a characteristic asteroid fauna. The abyssal zone starts at about 2800 m. Regions of major faunal change are identified at the boundaries of both upper and mid-bathyal zones and at the transition of bathyal to abyssal fauna. Diversity is greatest at ∼1800 m, decreasing with depth to ∼2600 m before increasing again to high levels at ∼4700 m.     

A submersible study in the western Blanco fracture Zone,N.E. Pacific: Structure and evolution during the last 1.6 Ma

During July and August 1991, the French-American Blanconaute dive program used the French submersibleNautile to investigate the West Blanco Depression (WBD), a deep, elongate trough located at the intersection of the Blanco Transform Fault Zone with the southern Juan de Fuca Ridge (JdFR). Twenty dives were carried out along the north wall of the WBD, which exposes the upper oceanic crust over a 65 km distance, from the JdFR axis (to the west) to the oblique trace of an ancient propagator (to the east, crustal age around 2 Ma). Thirteen of these dives were precisely located within a 13 × 7 km zone of the north wall, covered by a high-resolution sonar mapping operation during the Blancotrough cruise in 1987. This series of geological traverses, plus 4 dives across the south wall of the WBD (one dive) and the adjacent Parks Plateau (3 dives), collected 242 rock samples. We report here the main results of the dive program and preliminary laboratory studies:

1. Transform-related tectonic activity has recently abandoned the southern margin of Parks Plateau, and is presently located inside the WBD area, mainly along its northern wall. The tectonic features observed are compatible with a right-lateral strike-slip system, with a NE-SW extensional component.
2. Three main lithological units are exposed along the north wall of the WBD. From top to bottom, they are: (1) a Volcanic Unit, forming a steep upper cliff, made of massive and pillow flows and basaltic dikes, with an estimated average thickness of 800 m; (2) a less steep Transition Zone, about 150 to 400 m thick, largely masked by rubble but exposing both diabase outcrops and pillow flows; and (3) a massive Diabase Unit, exposed over 700–800 m, with a dike complex structure visible from place to place, and cut by a net of hydrothermal veins. Deep crustal rocks such as gabbros were not observed.
3. Spectacular mass-wasting features are visible all along the north wall of the WBD. About 60% of the face of the wall is masked by talus cones, rubble, rock avalanche deposits and slide blocks. Three main landslides, of approximately one km³ in volume each, were tentatively identified. One of them was mapped in detail and consists of an approximately 300 m thick (0.85 km³), coherent slide block detached from a zone where intense hydrothermal alteration and faulting have obviously weakened the bedrock, that is in places entirely altered to blue clays.
4. The basaltic lavas of the WBD north wall show a remarkable evolution with time, from east to west. Around the tip of the ancient propagator, they are restricted to primitive, olivine-rich picritic basalts. Proceeding westward, they exhibit a wide range of differentiation, including highly fractionated, FeTi-rich ferrobasalts at about 35–45 km from the JdFR axis. When approaching the JdFR axis, the FeTi enrichment decreases gradually, and the ferrobasalts evolve towards slightly differentiated MORB-type basalts, typical of the southern JdFR. This magmatic evolution marks the transition from the end of a propagating rift regime to a steady-state accretion regime.
5. The WBD north wall also permits the study of weathering and hydrothermal alteration processes and their evolution in space and time. Vertically, the alteration products evolve from oceanic weathering and zeolite facies (Volcanic Unit) to the greenschist facies (Transition Zone and Diabase Unit). Horizontally, the evolution with time is mainly a general hydration of the crust that is, however, very irregularly distributed.
6. Several vertical magnetic traverses along the north wall of the WBD, using a bottom magnetometer attached to the basket of the submersible, have shown a sharp 5000 to 7000 nT positive anomaly at about 3500 m depth. This anomaly corresponds exactly to the first appearance of extrusive pillow-lava outcrops, and confirms the dramatic decrease in magnetic anomaly amplitude below that depth, detected during the Blancotrough cruise in 1987. The vertical magnetic profiles thus appear to have imaged the base of the magnetic source layer.