Soldier crab paleo-ichnology and its preservation in beach rock along the Pilbara Coast,Western Australia: its geoheritage significance

Ichnofossils, although small-scale geological features, can be of geoheritage significance. The Western Australian soldier crab (Mictyris occidentalis Unno 2008) presents an unusual and unique association between the crab and its ichnology because, as the species progresses through life, its behaviour becomes more complex and its traces commensurably more varied. The links between crab ichnology, life stage, behaviour, and environment are so direct that where traces are preserved they can be used to interpret fossil crab sizes, population structures, behaviour and paleo-environment. In this context the ichnofossils comprise important paleo-ecological and paleo-environmental indicators. Middle Holocene soldier crab ichnofossils occur in 5000 year-old beach rock at Port Hedland, Western Australia. The ichnofossils include rosettes, pustules, pellet-roofed tunnels, back-filled burrows and swirl lamination, air cavities and tidal-current-degraded discard pellets. They provide information on soldier crab population sizes and behaviour, and the nature of the environment along middle Holocene shores. The ichnofossils are of geoheritage significance in their own right for the paleontological and paleo-environmental information they present, however, given the rarity of their preservation, and the location of well-developed beach rock largely restricted to the arid Pilbara Coast, these ichnofossils are an uncommon and significant geological tool for use in paleo-environmental, paleo-ecological and paleoclimate reconstructions. They are of geoheritage significance because of their diagnostic signatures and rarity of occurrence. The limitations of current classifications of traces and ichnofossils, owing to restricted definition of terms, are highlighted by these ichnofossils as several ichnological products in the complex range of soldier crab traces are not possible to classify.     

北极阿拉斯加巴罗地区现代环境的地球化学特征研究*

本文以北极阿拉斯加巴罗地区样品分析为依据,研究泻湖、淡水湖、河流、沼泽、土壤等的环境地球化学特征。结果表明,巴罗地区融冻物理风化作用强烈,化学风化和生物地球化学作用较弱,物质以机械搬运为主,H⁺为地带性标型元素。地表水化学类型阴离子以Cl^-为主,阳离子以K⁺Na⁺为主。现代沉积物、地表土壤、沼泽泥炭层有机质含量丰富,最高可达50.07%.大量元素SiO₂含量极高,稀有稀土元素、微量元素含量偏低,但Hg、Cd、Cr的含量相对较高。     

一秋龄性成熟中华绒螫蟹的生物学──1.外部形态特征及性腺变化

本文描述了一秋龄性腺成熟中华绒螯蟹（简称河蟹）的外部特征并与一秋龄未成熟及二秋龄成熟河蟹进行比较,同时给出了体重与壳宽的回归方程．保安湖的研究结果表明,对于一秋龄雌蟹,体重大于２９．８ｇ（壳宽为４．０３ｃｍ）全部成熟,而体重小于１３．１ｇ（壳宽为３．００ｃｍ）均不成熟,体重在１３、１－２９．８ｇ之间,既有成熟又有未成熟．对于一秋龄雄蟹,体重大于２６．０ｇ（壳宽３．９１ｃｍ）,全部成熟,而于１２．０ｇ壳宽２．６６ｃｍ）均未成熟,体重在１２．０－２６．０ｇ之间,既有成熟者又有未成熟个体．对一秋龄成熟河蟹成熟系数逐月变化的观察表明,在翌年３月份达到峰值,雌蟹为１２． ３２± １． ７５％,雄蟹为 ４． ２４± ０． ０６％;此后,性腺迅速退化,至翌年七月上旬,卵巢退变成细索状结构．己无完整的卵粒．     

Enzyme variation in marine and estuarine populations of a mud crab,Macrophthalmus hirtipes (Ocypodidae)

Protein and enzyme variation in 2 populations of the mud crab Macrophthalmus hirtipes (Jacquinot, 1853) (Ocypodidae) from 1 marine and 1 estuarine habitat were investigated by poly‐acrylamide gel electrophoresis. A survey of 24 loci revealed that 22 were common to both populations; 20 were monomorphic and 2 were highly polymorphic. Two alleles were detected for each of the polymorphic loci, esterase‐2 (EST‐2) and ester‐ase‐3 (EST‐3). The frequencies of the EST‐3 alleles were similar in the 2 populations. However, the frequencies of the 2 EST‐2 alleles in the estuarine population were significantly different from those for the marine population. Expression of 1 locus, esterase‐4 (EST‐4) was confined to the estuarine population. Two alkaline phosphatase loci (AKPH‐1 and AKPH‐2) were detected in the estuarine population, but only AKPH‐1 was found in the marine population. EST‐4 and AKPH‐2 were neither sex nor age specific. These interpopulational genetic differences may reflect differences in environmental conditions measured between the 2 habitats.     

Variation of diffuse attenuation coefficient of downwelling irradiance in the Arctic Ocean

The diffuse attenuation coefficient(Kd) for downwelling irradiance is calculated from solar irradiance data measured in the Arctic Ocean during 3rd and 4th Chinese National Arctic Research Expedition(CHINARE), including 18 stations and nine stations selected for irradiance profiles in sea water respectively. In this study, the variation of attenuation coefficient in the Arctic Ocean was studied, and the following results were obtained. First, the relationship between attenuation coefficient and chlorophyll concentration in the Arctic Ocean has the form of a power function. The best fit is at 443 nm, and its determination coefficient is more than 0.7. With increasing wavelength, the determination coefficient decreases abruptly. At 550 nm, it even reaches a value lower than 0.2. However, the exponent fitted is only half of that adapted in low-latitude ocean because of the lower chlorophyll-specific absorption in the Arctic Ocean. The upshot was that, in the case of the same chlorophyll concentration, the attenuation caused by phytoplankton chlorophyll in the Arctic Ocean is lower than in low-latitude ocean. Second, the spectral model, which exhibits the relationship of attenuation coefficients between 490 nm and other wavelength, was built and provided a new method to estimate the attenuation coefficient at other wavelength, if the attenuation coefficient at 490 nm was known. Third, the impact factors on attenuation coefficient, including sea ice and sea water mass, were discussed. The influence of sea ice on attenuation coefficient is indirect and is determined through the control of entering solar radiation. The linear relationship between averaging sea ice concentration(ASIC, from 158 Julian day to observation day) and the depth of maximum chlorophyll is fitted by a simple linear equation. In addition, the sea water mass, such as the ACW(Alaskan Coastal Water), directly affects the amount of chlorophyll through taking more nutrient, and results in the higher attenuation coefficient in the layer of 30–60 m. Consequently, the spectral model of diffuse attenuation coefficient, the relationship between attenuation coefficient and chlorophyll and the linear relationship between the ASIC and the depth of maximum chlorophyll, together provide probability for simulating the process of diffuse attenuation coefficient during summer in the Arctic Ocean.     

Bio-Optical Properties of Seawater in the Western Subarctic Gyre and Alaskan Gyre in the Subarctic North Pacific and the Southern Bering Sea during the Summer of 1997

Chlorophyll a concentrations (chla) and the absorption coefficients of total particulate matter [a _p()], phytoplankton [a _ph()], detritus [a _d()], and colored dissolved organic matter: CDOM [a _CDOM()] were measured in seawater samples collected in the subarctic North Pacific and the southern Bering Sea during the summer of 1997. We examined the specific spectral properties of absorption for each material, and compared the light fields in the Western subarctic Gyre (area WSG) with those in the Alaskan Gyre (area AG), and the southern Bering Sea (area SB). In the area WSG, the irradiance in the surface layer decreased markedly, indicating high absorption. In the area AG, the radiant energy penetrated deeply, and the chl a and absorption values were low throughout the water column. In the area SB, light absorption was high in the surface layer on the shelf edge and decreased with increasing depth; on the other hand, light absorption was low in the surface layer in the shelf area and increased with increasing depth.     

A Comparison of the Seasonality and Interannual Variability of Phytoplankton Biomass and Production in the Western and Eastern Gyres of the Subarctic Pacific Using Multi-Sensor Satellite Data

This study documents the results of a multi-sensor satellite investigation aimed at comparing the seasonality and interannual variability of phytoplankton biomass and primary productivity (PP) in the western and eastern gyres of the subarctic Pacific. Satellite data helped discern several features, most importantly the existence of significant east-west gradients in the supply of nitrate in winter, in the consumption of nitrate by phytoplankton and in phytoplankton production and biomass accumulation over the growth season. In the western subarctic gyre many of these features appear to be regulated by the strength of sea surface winds through increased iron and nitrate inputs. Multiple regression analysis of data extracted from 12 boxes spanning different hydrographic regimes in the subarctic Pacific, showed that over 65% of the variations in PP in the subarctic Pacific could be explained solely on the basis of changes in the strength of sea surface winds and the intensity of incident irradiance (PAR). The dependence of PP on sea surface wind stress was far greater in the western subarctic Pacific Gyre (WSG), than in the Alaskan Gyre (ALG) due to diminishing impact of surface winds towards the east. Spring accumulation of phytoplankton biomass was greater in the WSG than in the ALG despite the higher rates of PP in the latter. This study assumes particular significance because it helps ascertain the existence of several sub-regions within the two broader domains of the WSG and the ALG. In addition, large interannual variations in phytoplankton biomass and PP were observed in the subarctic Pacific following the onset of the El-Niño event of 1997 and the transition to La-Niña conditions in 1999. These variations were largely the result of differences in meteorological and oceanographic conditions across the subarctic Pacific following the development of the El-Niño.     

Biology of three Malacostraca (Decapoda) in a Mediterranean lagoon with particular emphasis on the effect of rapid environmental changes on the activity (catchability) of the species

The activity of three Malacostraca (Decapoda), Crangon crangon, Carcinus aestuarii and Paleamon squilla, was studied following rapid environmental changes in a Mediterranean lagoon linked temporarily with the sea. Nekton was sampled every 2–3 days using fixed fyke nets. A canonical analysis and a stepwise multiple regression were computed to determine which factor(s) can predict or account for the catch of these three decapods. In spite of rapid environmental changes no exceptional mortality was observed in each of the three species. Temperature is the environmental factor with major impact on the activity of C. crangon. Activity of P. squilla is controlled by water depth. At a depth of less than 20 cm two factors, salinity and phase of the moon, have a significant influence on the activity of this species. At depths deeper than 20 cm the activity is inhibited. There is only a weak relationship between the catch of C. aestuarii and salinity. Additional data on the life cycle of these species are given. The limitations of a monthly sampling period are discussed and the need for more short-term, consecutive sampling periods is stressed in order to understand the dynamics of systems with rapid environmental fluctuations.