The timing and reproductive output of the commercial sea cucumber Holothuria scabra on the Kenyan coast

The sea cucumber Holothuria scabra is a widely distributed and economically important species that has been harvested in Kenya for decades. No previous studies have been carried out on the reproduction of this species in Kenya. Standard gonad index methods were used to analyze reproductive patterns of individuals collected monthly in 1998–1999, 2000–2001 and 2006–2007. Morphological characteristics, gonad tubule lengths and fecundity were also measured. Mean monthly gonad indices were significantly correlated between males and females indicating synchronous gonad development between the sexes. Gonad indices showed a biannual pattern that was consistent in all three years with a minor spawning event occurring between August and September and a major spawning event between November and December. The pattern of gonad growth showed significant variability between years and between months. Temporal changes in gonad growth correlated significantly with gonad tubule length and absolute fecundity. Monthly gonad indices also correlated significantly with monthly measurements of air temperature and light suggesting a possible role for both factors in timing gametogenesis and spawning. There was a shift in sex ratio from unity in the 1998–1999 and 2000–2001 samples to significantly more males in the 2006–2007 samples, as well as a significant reduction in mean sizes (body wall weight) and reproductive output (gonad index) which suggests that the reproductive success of this species is potentially negatively affected by fishing.     

Heavy metals in the benthic animals from hydrothermal vents: Results of neutron activation analysis

A series of samples of inhabitants of hydrothermal vents were collected during the 12th cruise of R/V Akademik Mstislav Keldysh in Guaymas Basin (the Gulf of California) and the Axial Seamount area (Juan de Fuca Ridge). The concentrations of trace and heavy metals in the tissues of Ridgeia piscesae, Riftia pachyptila, and Paralvinella palmiformis were analyzed. The neutron-activation analysis revealed significantly higher concentrations of uranium in the tissues of Paralvinella palmiformis as compared to the ambient seawater. The possible reasons for such phenomenon are discussed. The data obtained by the neutron-activation method are compared with those obtained by the atomic-absorption method for the same tissues analyzed.     

Nonlinear interaction of internal waves in the coastal zone of the Sea of Japan

Nonlinear interactions of the internal waves of a tidal period with low-frequency synoptic-scale internal waves are studied using instrumental measurements of the current in the coastal zone of the Sea of Japan. In the course of spectral analysis of the data of instrumental measurements, it is found that a maximum in the spectrum of the kinetic energy of coastal waters in the vicinity of the semidiurnal frequency ω₀ is surrounded by satellite maxima whose frequencies obey the relation ω _s = ω₀ ± Ω, where Ω is the characteristic frequency of synoptic-scale internal waves. The spectrum of the anticyclonic current component has a similar structure in the vicinities of the frequency ω₀ and its first and second harmonics. The general theory of nonlinear interactions of weakly dispersive waves is used to solve the problem of modulation and the parametric amplification of tidal internal waves in the coastal zone using low-frequency narrow-band internal waviness. As can be judged from the literature, the effect of parametric modulation of tidal internal waves by low-frequency synoptic-scale internal waves has been recorded in the coastal zone of a tidal sea for the first time.     

Distribution patterns of interstitial polychaetes in sandy beaches of southern Brazil

This study describes the distribution patterns of interstitial polychaetes along morphodynamic gradients on six exposed sandy beaches in Santa Catarina and Paraná (South Brazil). Three random transects were sampled at two points on each beach, one at the swash and another at the surf zone, in winter and summer conditions. Six sediment replicates were collected at each sampling point using a corer of 4.6 cm internal diameter that removed 10 cm into the sediment. Abundance and composition of interstitial polychaete were correlated to wave height, slope, grain size, CaCO₃, chlorophyll a , omega indexes, temperature and relative tide range using a canonical correspondence analysis (CCA). A factorial ANOVA showed that taxa richness, mean density and Shannon's diversity were significantly higher at the reflective beaches, but average values differ significantly between transects and these differences change according to the beach zones on both sampling dates. PERMANOVA showed that polychaete associations differ among transects according to the beach zones. The composition of interstitial polychaete associations was significantly correlated to beach morphodynamics and features (P < 0.01). Polychaete associations of reflective beaches were more diverse than in other morphodynamic states. Intermediate beaches may also sustain diverse associations due to temporal variability of the morphodynamic patterns. Beaches presenting extreme dissipative morphodynamics and compacted sediments appear to be unfavourable for the occurrence of interstitial polychaetes.     

Management of the coastal-sea-zone-ecosystem model

We present a model of the processes of development in the ecosystem of the coastal zone of the sea constructed by the method of adaptive balance of causes (ABC-method). The model contains nine variables (phyto- and zooplankton, fish larvae, fishes, oxygen, carbon dioxide, salinity, biogenic elements, and detritus) affected by the solar radiation, surface wind, sea temperature, and river discharge. The equations of the model contain control agents governing the dependences of the elements of the food chain on the vitally important resources and environmental conditions. The scenarios of the processes of development are constructed for the simulated annual courses of external actions. The possibility of management of fish resources by regulating the flows of biogenic elements and detritus with river discharge is discussed. A mechanism of management based on the monitoring of the concentration of dissolved oxygen in seawater is proposed. The numerical experiments show that the ABC-model of the processes of development in the ecosystem of the coastal zone of the sea makes it possible to simulate the scenarios of regulation of the flows of biogenic elements and detritus into the sea with an aim of preservation of of fish resources. Translated from Morskoi Gidrofizicheskii Zhurnal, No. 1, pp. 36–49, January–February, 2009.     

Rapid visualization of plankton abundance and taxonomic composition using the Video Plankton Recorder

Traditional methods for determining spatial distributions of planktonic taxa involve net, pump, and bottle collections followed by the tedious and time-consuming task of plankton sample analysis. Thus, plankton ecologists often require months or even years to process samples from a single study. In this paper, we present a method that allows rapid visualization of the distribution of planktonic taxa while at sea. Rapid characterization of plankton distributions is essential in the dynamic physical environment, where biological and physical patterns can change quickly. Such a “sample-and-observe” capability is necessary for mapping ephemeral features (such as patches, eddies, jets, plumes) and determining appropriate locations to conduct more localized sampling, including in situ observational studies. We describe the techniques used in imaging the plankton, analyzing the video, and visualizing the data. We present an example of at-sea data analysis conducted aboard R.V. Columbus Iselin on Georges Bank in May 1994 and visualizations of the 3-dimensional distribution of selected planktonic taxa in a 2 × 2 km × 90 m volume of seawater. A video of the image processing and visualization is included on the CD-ROM accompanying this volume and is an essential part of this paper.     

Formation and distribution of manganese nodule deposit in the northwestern margin of Clarion-Clipperton fracture zones,northeast equatorial Pacific

In the northwestern margin of the Clarion and Clipperton fracture zones, manganese nodules are latitudinally variable in character, resulting from the progressive (re)generation of nodules since the Oligocene as the Pacific Plate migrates northwestward beneath the equatorial production zone. Complemented by the surface water productivity, bottom current activities have concentrated nodules in the Oligocene to Miocene siliceous clay. Resedimentation processes on nodules form three types of nodules with concentric structures and 10 Å-manganaterich bottoms, by periodically causing the diagenetic growth of nodules within the topmost sediment layer.     

Near-surface seismic facies at the Korea Strait shelf margin and trough region

High-resolution seismic profiles across the shelf margin and trough region of the Korea Strait reveal five shallow, near-surface facies units. These are relict coastal deposits, relict delta deposits, slumps and slides, and trough lag deposits. Most deposits represent a lowstand systems tract, formed during the last lowstand of sea level. Relict coastal deposits represent a linear sediment body along the present shelf margin at water depths of 120–150 m, whereas relict delta deposits occur on the gentle, southwestern slope of the trough at water depths of about 150–200 m. Slumps and slides are dominant at the base of slope in the central trough region. Sediments on the central trough floor were partly eroded and redistributed by strong currents, resulting in lag deposits.     

Interannual Variation of Eddy Kinetic Energy from TOPEX Altimeter Observations

Monthly mesoscale eddy kinetic energy (EKE) per unit mass has been computed for four years, 1993-1996, from TOPEX altimeter data in the Indian Ocean. It ranges from 50 cm²/s² to 2,700 cm²/s² (about 4,000 cm²/s² near the Somali region in a few months). In the Arabian Sea and the Bay of Bengal, regions of high energies associated with various current systems under the influence of monsoonal winds have been delineated. Monthly variation of EKE near the Somali region has been studied. In this region the maximum EKE per unit mass has been observed during August every year, with variations in magnitude from year to year. The mesoscale eddy kinetic energy computed from TOPEX altimeter-derived SSH during 1993-1996 is highest near the Somali region during the SW monsoon, due to formation of mesoscale eddies and also because of upwelling. In the Bay of Bengal, high eddy kinetic energy is seen toward the western side during nonmonsoonal months due to the western boundary current. In the South Indian Ocean, it is high at a few places in some of the months. A large part of the Indian Ocean exhibits low eddy kinetic energy (less than 300 cm²/s²) year-round.