Toxicity of Santa Barbara seep oil to starfish embryos: Part 2—the growth bioassay

The asteroid Patiria miniata was used to develop a static bioassay for various crude oil water-soluble fractions (WSF). The criterion used is the size of 48-h exposed embryos. The reasons for choosing this species and the growth criterion are discussed. Experiments show that the body length of 48-h exposed embryos is inversely proportional to hydrocarbon concentration of the WSF and the time of exposure. It is also shown that the toxicity of the WSF decreases with the age of the preparation and that the first 12 h following fertilisation are most sensitive to the effects of WSF.     

红海及亚丁湾间之海水交换

分析表观耗氧量、滴定碱度及总二氧化碳量等资料来研判红海及亚丁湾间之海水交换。结果显示,红海深层水的方解石及霰石饱和度均比亚丁湾和阿拉伯海深层水的饱和度高。红海全水柱之方解石和霰石都处於过饱和状态,亚丁湾和阿拉伯海中各深度之方解石亦呈过饱和状态,但霰石的饱和探度则大约在500m左右。分析深层水之生物体无机碳与有机碳的分解比值,可以发现此地区深层水中,大约有25％的总二氧化碳增加量是由无机碳酸钙溶解而来。     

Spatial variability in the primary productivity in the East China Sea and its adjacent waters

Primary productivity in the East China Sea and its adjacent area was measured by the¹³C tracer method during winter, summer and fall in 1993 and 1994. The depth-integrated primary productivity in the Kuroshio Current ranged from 220 to 350 mgC m⁻²d⁻¹, and showed little seasonal variability. High primary productivity (above 570 mgC m⁻²d⁻¹) was measured at the center of the continental shelf throughout the observation period. The productivity at the station nearest to the Changjiang estuary exhibited a distinctive seasonal change from 68 to 1,500 mgC m⁻²d⁻¹. Depth-integrated primary productivity was 2.7 times higher in the shelf area than the rates at the Kuroshio Current. High chlorophyll-a specific productivity (mgC mgChl.-a⁻²d⁻¹) throughout the euphotic zone was mainly found in the shelf area rather than off-shelf area, probably due to higher nutrient availability and higher activity of phytoplankton at the subsurface layer in the shelf area.     

Tide-induced residual currents with Stokes and Ekman layers over an undulatory sea floor

Residual currents induced by the tidal current flowing over a rotating ridge, which is infinitely elongated in they-direction and the width of which is so large that the nonlinear effect is weak enough, have been analysed theoretically. The currents are restrained by Stokes and Ekman layers which are given through a constant viscosity. This study shows that the direction of the cross-isobath residual current just above the sea floor varies with the value off ^*(=Coriolis parameter/tide frequency), that the along-isobath residual current forms a clockwise circulation around the rotating ridge and that it is stronger asf ^* grows larger.     

Linkages between Alaskan sockeye salmon abundance, growth at sea, and climate, 1955–2002

We tested the hypothesis that increased growth of salmon during early marine life contributed to greater survival and abundance of salmon following the 1976/1977 climate regime shift and that this, in turn, led to density-dependent reductions in growth during late marine stages. Annual measurements of Bristol Bay (Bering Sea) and Chignik (Gulf of Alaska) sockeye salmon scale growth from 1955 to 2002 were used as indices of body growth. During the first and second years at sea, growth of both stocks tended to be higher after the 1976–1977 climate shift, whereas growth during the third year and homeward migration was often below average. Multiple regression models indicated that return per spawner of Bristol Bay sockeye salmon and adult abundance of western and central Alaska sockeye salmon were positively correlated with growth during the first 2 years at sea and negatively correlated with growth during later life stages. After accounting for competition between Bristol Bay sockeye and Asian pink salmon, age-specific adult length of Bristol Bay salmon increased after the 1976–1977 regime shift, then decreased after the 1989 climate shift. Late marine growth and age-specific adult length of Bristol Bay salmon was exceptionally low after 1989, possibly reducing their reproductive potential. These findings support the hypothesis that greater marine growth during the first 2 years at sea contributed to greater salmon survival and abundance, which in turn led to density-dependent growth during later life stages when size-related mortality was likely lower. Our findings provide new evidence supporting the importance of bottom-up control in marine ecosystems and highlight the complex dynamics of species interactions that continually change as salmon grow and mature in the ocean.     

Egg production of Calanus finmarchicus—A basin-scale study

Egg production of Calanus finmarchicus was studied during joint basin-scale surveys in April–June 2003 in the Norwegian Sea. Surveys covered the whole Norwegian Sea and were conducted from Norwegian, Icelandic and Faroese research vessels. Stations were classified as being in pre-bloom, bloom or post-bloom phase according to levels of chlorophyll a and nitrate. Individual egg production rates and population egg production rates were calculated and compared between areas. Both individual egg production rates (eggs female⁻¹ day⁻¹) and population egg production rates (eggs m⁻² day⁻¹) were significantly higher in bloom areas compared with pre-bloom and post-bloom areas. However, when integrated over an estimated duration of the three phases, the time-integrated egg production (eggs m⁻²) in most years was highest in the pre-bloom phase, and this was explained by the longer duration of this phase compared with the two other phases.     

Developing a Marine Information System by Integrating Existing Ocean Models Using Object-Oriented Technology

Information systems developed for different applications within the environmental domain have common characteristics, which can potentially be abstracted for sharing and reuse of design and software modules. This article presents an approach to designing for reuse by abstracting commonalities in the design of a Marine Information System (MIS), facilitating data management in a prototype operational monitoring, forecasting, and management system for the North Atlantic and the Nordic Seas. A detailed study of the requirements and data analysis was carried out, and Object-Oriented Technology (OOT) is employed to encapsulate abstractions and to promote reuse of code and design. This article identifies the Object-Oriented Frameworks (OOFW) required to build the MIS. It also provides guidelines to environmental scientists for restructuring legacy software and employing modern programming techniques.     

Management of a shallow temperate estuary to control eutrophication: The effect of hydrodynamics on the system’s nutrient loading

The Mondego estuary, a shallow warm-temperate intertidal system located on the west coast of Portugal, has for some decades been under severe ecological stress, mainly caused by eutrophication. Water circulation in this system was, until 1998, mainly dependent on tides and on the freshwater input of a small tributary artificially controlled by a sluice. After 1998, the sluice opening was effectively minimised to reduce the nutrient loading, and the system hydrodynamics improved due to engineering work in the upstream areas. The objective of the present study was to evaluate the effect of the mitigation measures implemented in 1998. Changes to the hydrodynamics of the system were assessed using precipitation and salinity data in relation to the concentrations of dissolved inorganic nutrients, as well as the linkage between dissolved N:P ratios and the biological parameters (phytoplankton chlorophyll a concentrations, green macroalgal biomass and seagrass biomass). Two distinctive periods were compared, over a ten year period: from January 1993 to January 1997 and from January 1999 until January 2003. The effective reduction in the dissolved N:P atomic ratio from 37.7 to 13.2 after 1998 is a result of lowered ammonia, but not the oxidised forms of nitrogen (nitrate plus nitrite), or increased concentrations of dissolved inorganic phosphorus. Results suggest that the phytoplankton is not nutrient limited, yet maximum and mean biomass of green macroalgae was reduced by one order of magnitude after the mitigation measures. This suggests that besides lowering the water residence time of the system, macroalgal growth became nitrogen limited. In parallel to these changes the seagrass-covered area and biomass of Zostera noltii showed signs of recovery.     

Longitudinal strength of a high-speed ferry

The longitudinal strength of the high-speed ferry was investigated by subjecting the ship's hull girder to long-term loads obtained from a frequency-domain panel code. Prior to the statistical analysis, linearly computed transfer functions were corrected for nonlinear effects, yielding two sets of transfer functions valid for different wave amplitudes. One set corresponded to the hogging condition; the other set, to the sagging condition. Two regular equivalent design waves were specified that resulted in loads representing the most severe global design load conditions. The still-water loading condition, yielding a still-water vertical bending moment in hogging, was superimposed on the wave-induced loads to obtain the total (design) loads in hogging. For the sagging condition only, additional impact-related loads were superimposed to obtain the total (design) loads in sagging. A finite element model of the ship's structure was subjected to pressure distributions according to the two regular design waves. For comparison with classification society rule values, a simple beam theory strength analysis of the ship's midship section was performed first, and then another finite element analysis was carried out, whereby the imposed loads were tuned to the rule values of vertical bending moments. Rule-based magnitudes of nominal maximum longitudinal stress deviated significantly (25–39%) from comparable stresses obtained by the panel code based finite element analysis. However, stresses obtained from the rule-based finite element analysis agreed more favorably, especially in hogging. In the uppermost deck, for example, the panel code based compressive stress was only 9% larger than the comparable stress from the rule-based finite element analysis.