Preliminary report on radionuclide concentrations in the bottom waters at the entrance of Wakasa Bay with special reference to the Japan Sea Proper Water

Marked fluctuation of concentrations of⁹⁰Sr and¹³⁷Cs was observed in the bottom waters at the entrance of Wakasa Bay during 1987–1992, and the cause was investigated. The concentrations of⁹⁰Sr and¹³⁷Cs in the bottom waters were significantly low when the upper level of the Japan Sea Proper Water (JSPW) was high and covered the sampling depth, but high when the upper level of the JSPW was low. The cause of the fluctuation observed in the bottom waters is, therefore, suggested to be the vertical fluctuation of the upper level of the JSPW on the shelf slope, which has been little described before.     

The synchronous coupling of a third-generation wave model and a two-dimensional storm surge model

The interaction of waves and currents is studied by the dynamical coupling of a third generation wave model and a two-dimensional storm surge model. The coupling process of the two models is implemented synchronously. To estimate the effects of waves on the generation of storm surges, the theory of Janssen is used. The effects of the wave radiation stress on surge levels and the effects of storm-induced currents on waves are also investigated.The coupled wave and storm surge models have been tested by hindcasting two storm events in the northern South China Sea. The use of the Simth and Banke stress relation underestimates the surges by 10%. The inclusion of the radiation stress improves the accuracy of the computed results slightly by 2%. The introduction of a wave-dependent surface drag gives a significant improvement. The storm-induced currents clearly affect the wave characteristics at the peak stage. However, as far as the prediction of wave height is concerned, it is better not to consider the wave radiation stress in the storm surge model unless this is accompanied by a wave-dependent surface drag.     

Abundance, distribution and patch formation of zooplankton

The goal of studies described here was to determine the responses of zooplankton taxa to phytoplankton patches which develop in and near intrusions of cold, nutrient-rich Gulf Stream water. To achieve this goal we determined the horizontal and vertical distributions of abundant mesozooplankton taxa on the south-eastern continental shelf of the USA between 29°30′ and 31°N. The study period was from June 23 to August 16, 1981. Highest concentrations of zooplankton usually occurred in and near patches of phytoplankton. Increased phytoplankton appeared to trigger the formation of patches of the calanoid copepod Temora turbinata and the cyclopoid copepods Oithona spp. and Oncaea spp. The patches of zooplankton had greater alongshore than cross-shelf dimensions. T. turbinata responded rapidly to increased concentrations of phytoplankton by reproducing and aggregating in and above intruded waters. Oithonidae which were often, but not always, abundant in phytoplankton patches eventually attained high concentrations over most of the middle and part of the inner shelf. Their concentration and that of Oncaeidae increased steadily. Oncaeidae were not abundant in recently upwelled waters, as was T. turbinata but reached high concentrations in older intrusions when the abundance of T. turbinata remained level or decreased slowly. Both cyclopoid taxa are thought to reproduce slowly (egg sacs) compared to T. turbinata. Another taxon, the doliolids, became abundant far more rapidly in intruded waters (by asexual reproduction) than did the other three taxa. Doliolids were the most opportunistic intrusion zooplankton form. They do not regularly occur in low abundance on the shelf, as do the three copepod taxa, but develop in pulses in regions where T. turbinata and Oncaea are not abundant. Of the four taxa studied the abundance of doliolids increased and decreased most rapidly, whereas Oithona and Oncaea increased slowly and did not decrease during the study period. T. turbinata and Oncaea were most abundant at 60% of all stations in the intruding water. Doliolids and Oithona on the other hand, were mostly in the thermocline and intrusion. Whereas phytoplankton patches, which developed in intrusions, were physically induced (PAFFENHÖFER and LEE, 1988), patches of zooplankton were biologically induced.     

南海囊糠虾亚科的初步研究

囊糠虾亚科Gastrosaccinae 包括的种数并不很多，但有些种数量相当大，是经济鱼虾的天然饵料，在海洋食物链中占较重要的地位。例如黄海的漂浮囊糠虾Gastrosaccus pelagicus Ii 数量很大，普遍发现于底层鱼类胃含物中；此种及其他一些量大的种又可用作养殖鱼虾的饵料。这一亚科迄今已知共7属69种。本文根据中国科学院海洋研究所1958-60年在南海北部所采的底层浮游生物标本和中国科学院南海海洋研究所1974-81年采自西沙群岛、中沙群岛的标本写成，共发现4属12种，其中6种为中国近海的首次记录。     

Burial and scour around short cylinder under progressive shoaling waves

The results of a laboratory experimental program aimed at better understanding the scour around and burial of heavy cylindrical objects under oscillating flow on a sandy bed are described. This study was motivated by its application to the dynamics of isolated cobbles/mines on a sandy floor under nonlinear progressive waves, such as that occur in shallow coastal waters beyond the wave-breaking region. In the experiments, nonlinear progressive waves were generated in a long wave tank of rectangular cross-section with a bottom slope. Model mines (short cylinders) were placed on the sandy bottom and the temporal evolution of the bed profile and the velocity field in the near field of the object were observed. Experiments were conducted at relatively high Reynolds numbers for a range of flow conditions, which can be characterized by the Keulegan–Carpenter number and Shields parameter. Depending on the values of these parameters, four different scour regimes around the cylinder including periodical burial of cylinder under migrating sand ripples were observed; they were classified as: (i) no scour/burial, (ii) initial scour, (iii) expanded scour, and (iv) periodic burial cases. A scour regime diagram was developed and the demarcation criteria between different regimes were deduced. Semi-empirical formulae that permit estimation of the scour depth with time, the equilibrium maximum scour depth and length, and conditions necessary for the burial of the cylinder as a function of main external parameters are also proposed.     

Integration of a Multi-Stage Bulk Materials Acquisition System from the Viewpoint of Dock Operations

A multi-stage bulk materials acquisition system is examined from the viewpoint of dock operations. The whole process can be divided into four stages and treated as four subsystems: ships scheduling planning, material yard planning, dock arrangement, and material discharging. Since the structure and the complexity of each subsystem is different, the solution approaches applied are also different with respect to each. To increase operations efficiency and data consistency, an integration of the subsystems by coordinating the operations sequence and data communications for the four subsystems is discussed. The four subsystems are illustrated by using the material docks of China Steel Corporation, and the models developed in this research are also validated. The results indicate that the models developed are capable of deriving solutions better than the existing ones. Although the discussions are confined to China Steel Corporation, the models can be applied to other companies with similar operations.     

Seasonality and interannual variability of freshwater inflow to a large oligohaline estuary in the Northern Gulf of Mexico

Quantity, timing, duration, and fluctuation of freshwater inflow are important factors affecting the development and health of aquatic and adjacent wetland ecosystems in coastal estuaries. This study assessed six decades of freshwater inflow from the Amite River, Tickfaw River, and Tangipahoa River watersheds to Lake Pontchartrain, a large oligohaline estuary in the Northern Gulf of Mexico, whose flood waters caused recent damage to the city of New Orleans in the aftermath of Hurricane Katrina. By utilizing the long-term (1940–2002) river discharge and climatic data from the three major tributary watersheds, monthly and annual freshwater inflows have been quantified and their spatial and temporal variations have been analyzed. On average, the three rivers discharged (±standard error) 0.27 ± 0.04 km³ freshwater monthly and 3.29 ± 0.15 km³ freshwater annually into the lake estuarine system, with the highest inflow from the Amite River (0.16 ± 0.03 m³ mon⁻¹, and 1.91 ± 0.09 km³ yr⁻¹) and the lowest inflow from the Tickfaw River (0.03 ± 0.00 km³ mon⁻¹, and 0.34 ± 0.02 km³ yr⁻¹). A distinct seasonality was evident with over 69% of the total annual inflow occurring during December and May (wet months) and with a low flow period from August to November (dry months). The monthly inflow during the wet months was positively correlated with the monthly precipitation (r² = 0.64), while the monthly inflow during the dry months was subject to evapotranspiration. Furthermore, the study found a 20-year low flow period from 1954–1973 (2.76 ± 0.24 km³ yr⁻¹) and a 24-year high flow period from 1975–1998 (3.84 ± 0.24 km³ yr⁻¹), coinciding with both the climate variation and population growth in the watersheds.     

Estimating the underwater light field from remote sensing of ocean color

We present a new approach that incorporates two models to estimate the underwater light field from remote sensing of ocean color. The first employs a series of analytical, semi-analytical, and empirical algorithms to retrieve the spectrum of inherent optical properties (IOPs), including the absorption and the backscatter coefficients, from the spectrum of remote sensing reflectance. The second model computes the profile of photosynthetically available radiation E _0,PAR (z) for a vertically homogeneous water column using the information of the retrieved IOPs and the ambient optical environment. This computation is based on an improved look-up table technology that possesses high accuracy, comparable with the full solution of the radiative transfer equation, and meets the computational requirement of remote sensing application. This new approach was validated by in situ measurements and an extensive model-to-model comparison with a wide range of IOPs. We successfully mapped the compensation depth by applying this new approach to process the SeaWiFS imagery. This research suggests that E _0,PAR (z) can be obtained routinely from ocean-color data and may have significant implications for the estimation of global heat and carbon budget.     

Description of the post larva of star pipefish,halicampus punctatus (syngnathidae, gasterosteiformes) first found in the southwestern east sea, Korea

Larval specimens ofHalicampus punctatus were collected off Ulsan and Uljin in December 2002 (three specimens) and off Ulsan in December 2003 (one specimen). These specimens are characterized by the following morphological characteristics: rings, 14 + 35 = 49; subdorsal rings, 1 + 3 = 4; dorsal fin rays, 19 – 20; pectoral fin rays, 14 – 15; anal fin rays, 9; head length (HL), 5.8 – 6.7 in the standard length; snout length, 1.9 in HL; snout depth, 3.7 – 5.2 in snout length. The number of caudal fin rays 9 is less than those of the other species in the same genus 10. Wide stripe bands composed of small pigments are shown in the trunk and the tail. Melanophores are not found in the dorsal fin, the pectoral fin, and the anal fin except the caudal fin. The supraoccipital crest is on the head. The frontal ridge is on the dorsal side of front trunk. The blanched ridges on the opercular are fused with a main ridge like a tree branch. A few branched ridges that are small and narrow on the trunk and the tail are fused with the main ridges. We report these specimens as the first record in Korea and name them ‘Byeol-silgo-ki’ in Korean.     

A comparison of several wave spectra for the random wave diffraction by a semi-infinite breakwater

A comparison of the diffraction of multidirectional random waves using several selected wave spectrum models is presented in this paper. Six wave spectrum models, Bretschneider, Pierson–Moskowitz, ISSC, ITTC, Mitsuyasu, and JONSWAP spectrum, are considered. A discrete form for each of the given spectrum models is used to specify the incident wave conditions. Analytical solutions based on both the Fresnel integrals and polynomial approximations of the Fresnel integrals and numerical solutions of a boundary integral approach have been used to obtain the two-dimensional wave diffraction by a semi-infinite breakwater at uniform water depth. The diffraction of random waves is based on the cumulative superposition of linear diffraction solution. The results of predicted random wave diffraction for each of the given spectrum models are compared with those of the published physical model presented by Briggs et al. [1995. Wave diffraction around breakwater. Journal of Waterway, Port, Coastal and Ocean Engineering—ASCE 121(1), 23–35]. Reasonable agreement is obtained in all cases. The effect of the directional spreading function is also examined from the results of the random wave diffraction. Based on these comparisons, the present model for the analysis of various wave spectra is found to be an accurate and efficient tool for predicting the random wave field around a semi-infinite breakwater or inside a harbor of arbitrary geometry in practical applications.