Diapause embryos in the neustonic copepodAnomalocera patersoni

The neustonic copepodAnomalocera patersoni Templeton, collected from the Gulf of Naples from January to May 1988, laid subitaneous and diapause eggs that were of equal size and dark and smooth in appearance. In January and February, most eggs were subitaneous and hatched within 2 to 3 d at room temperature. Conspicuous numbers of diapause eggs were first obtained in February when several clutches contained a second egg type which did not hatch in a subitaneous manner. By March and April, most clutches contained only diapause eggs. Transmission electron microscope studies of subitaneous and diapause eggs revealed striking morphological differences. Subitaneous eggs had a thin vitelline coat covering the plasma membrane, whereas diapause eggs were enveloped by a complex four-layer structure which is assembled after spawning and which probably serves as a protective shell during dormancy. No major morphological differences were discernible in the oogenic cycle of females spawning either of the two egg types. Diapause eggs were shown to be embryos in early stages of development, and segmentation of these embryos was arrested for the entire 6-mo period of investigation. Diapause eggs hatched after 7 mo of dormancy.     

Body burden of chromium,copper, cadmium and lead in the neustonic copepod Anomalocera patersoni (pontellidae) collected from the Mediterranean sea

The amounts of Cr, Cu, Cd and Pb in the copepod Anomalocera patersoni were determined for 47 individuals by flameless atomic absorption spectrophotometry. The following mean body burdens of these elements were obtained: Cr 0.6, Cu 13, Cd 0.5, Pb 1.5 ng individual^-1, or Cr 2.1, Cu 42, Cd 1.5 and Pb 4.8 ng mg^-1 (dry weight). Cr, Cu and Cd contents did not differ significantly between males and females, however Pb did, with males having more. The data indicate that while the Cr, Cu and Pb body Hurden in these copepods follows the logarithmic normal distribution, Cd follows a normal distribution. Thus, the arithmetic means and the modes of Cd body burden are almost the same, while for the other elements the arithmetic means differ from the geometric means. This indicates that measurements of a few individuals suffice for estimating the mean body burden of Cd. On the other hand, many measurements are necessary for the body burden estimation of other elements, especially Cu.     

Diel variations in the nutritional physiology of Calanus glacialis from Lat. 78°N in the summer

Calanus glacialis (Jaschnov) from Isfjord, western Spitzbergen, showed no tendency to pronounced diurnal vertical migration or cyclic variations in feeding activity. The samples, taken regularly over a 24-h period and at three different depths in the beginning of August, did however show considerable individual variations in feeding activity. These variations, reflected in the results of gut analyses, were not related to variations in the concentrations of particulate protein, carbohydrate or algal pigments in the water. Analyses of the activities of two digestive enzymes and the electron-transport system (ETS) indicated that those few individuals always present below the photic zone were there temporarily, and showed no signs of slowing down their metabolism. The results suggest that the population of C. glacialis, during the Arctic summer, feeds continuously in the upper water layer, but that intermittent, non-synchronous individual feeding rhythms are the rule.     

Effects of temperature and food availability on growth and reproduction in the neustonic pedunculate barnacle Lepas anserifera

To elucidate the life history of neustonic animals, growth and reproductive patterns were investigated in the hermaphroditic pedunculate barnacle Lepas anserifera in field and laboratory experiments in Wakayama, western Japan from 2006 to 2008. The effects of temperature (19, 24 or 29°C) and food availability (once or twice a week) on growth and reproduction were also studied in the laboratory. The barnacles grew and matured rapidly, especially in the field: individuals on the average grew from 3 mm to more than 12 mm in capitulum length within 15 days and some were brooding. High temperature and high food availability resulted in greater growth. High temperature also resulted in earlier maturation of both testes and ovaries, whereas the effect of food availability was less clear. The rapid growth and maturation, together with earlier maturation at higher temperatures, may be an adaptation to ephemeral floating objects to which they attach.     

On the morphology of summer algae dynamics in non-stratified lakes

In the need for a model able to explain both slow and rapid changes in the behavior of algae, this paper applies a special technique to the construction of a more realistic dynamical system. The result is a transformation of a Monod type growth rate into an integrated Rabinowitch nonlinear functional form. A cusp catastrophe is subsequently unfolded from the state representation equation. Several qualitative aspects of the eutrophication phenomena then arise from the geometry of the model in a natural way. Also elucidated are the possible size of a collapsed algae biomass and the estimation of summerkill risks.     

Dynamics of the buoyant plume off the Pearl River Estuary in summer

Field measurements of salinity, wind and river discharge and numerical simulations of hydrodynamics from 1978 to 1984 are used to investigate the dynamics of the buoyant plume off the Pearl River Estuary (PRE), China during summer. The studies have shown that there are four major horizontal buoyant plume types in summer: Offshore Bulge Spreading (Type I), West Alongshore Spreading (Type II), East Offshore Spreading (Type III), and Symmetrical Alongshore Spreading (Type IV). River mouth conditions, winds and ambient coastal currents have inter-influences to the transport processes of the buoyant plume. It is found that all of the four types are surface-advected plumes by analysing the vertical characteristic of the plumes, and the monthly variations of the river discharge affect the plume size dominantly. The correlation coefficient between the PRE plume size and the river discharge reaches 0.85 during the high river discharge season. A wind strength index has been introduced to examine the wind effect. It is confirmed that winds play a significant role in forming the plume morphology. The alongshore wind stress and the coastal currents determine the alongshore plume spreading. The impact of the ambient currents such as Dongsha Current and South China Sea (SCS) Warm Current on the plume off the shelf has also assessed. The present study has demonstrated that both the river discharge and wind conditions affect the plume evolution.     

天津夏季地面O3浓度变化规律与影响因素

臭氧是城市污染大气中的首要光化学污染物,其变化规律与前体物(NO、NO2和CO)和气象因素关系密切.利用2008年夏季天津城区地面大气O3、相关前体物和气象因素等观测数据,研究了O3浓度水平和时间变化规律,重点分析了7月3日-8月5日O3与NO、NO2和CO等前体物及气象因素(气温、相对湿度和风速)的相关性.结果表明,天津城区夏季O3存在一定的污染,超标时段多发生在13:00-19:00,这一时段对应高温、低湿、大风的天气条件;NO、NO2和CO作为O3的前体物,昼间其浓度与O3浓度呈线性负相关,夜间相互作用较为复杂,相关性显著降低;气象因素对O3浓度影响明显,高温、低湿利于光化学反应的进行,O3浓度与风速呈正相关表明可能有外来源的存在.     

Vertical distribution of fish larvae in the Canaries-African coastal transition zone in summer

This study reports the vertical distribution of fish larvae during the 1999 summer upwelling season in the Canaries-African Coastal Transition Zone (the Canaries-ACTZ). The transition between the African coastal upwelling and the typical subtropical offshore conditions is a region of intense mesoscale activity that supports a larval fish population dominated by African neritic species. During the study, the thermal stratification extended almost to the surface everywhere, and the surface mixed layer was typically shallow or non-existent. Upwelling occurred on the African shelf in a limited coastal sub-area of our sampling. The vertical distributions of the entire larval fish population, as well as of individual species, were independent of the seasonal thermocline. Fish larvae and mesozooplankton were concentrated at intermediate depths regardless of the thermocline position, probably because of its weak signature and spatial and temporal variability. Day/night vertical distributions suggest that some species did not perform diel vertical migration (DVM), whereas others showed either type I DVM or type II DVM. The opposing DVM patterns of different species compensate for each other resulting in no net DVM for the larval fish population as a whole.     

Associations between seabirds and water-masses in the northern Pacific Ocean in summer

Seabirds were systematically censused during more than 6 000 transect counts from research vessels in the North Pacific Ocean and Bering Sea during the summers of 1975 to 1984. Density indices were calculated for 1^o latitude-longitude blocks for 71 species. Blocks were assigned to oceanographic regions (current systems and domains) on the bases of geography, sea surface temperature and salinity. Bird abundances across regions were patchy; concentrations occurred at boundaries. Regional avifaunas overlapped as a function of three factors: similarity of water-types, geographic adjacency, and proximity to nesting areas. Four major avifaunas were apparent: the Bering Sea (and adjacent regions), the Subarctic Current System/Transition Domain (and adjacent regions), Upwelling Domain, and North Pacific Central Water. The subarctic boundary sharply separated different avifaunas. Ocean productivity may be the factor that ultimately affects avifaunal composition.     

Distribution and mortality of diapause eggs from calanoid copepods in relation to sedimentation regimes

Distribution, abundance and age of diapause eggs from three species of calanoid copepods (in particular from Acartia spp. most likely Acartia tonsa, and Centropages hamatus and less numerous from Temora longicornis) were recorded in sediment profiles by enumerating hatched nauplii from incubated sediment samples. Phytoplankton pigments and ²¹⁰Pb and ¹³⁷Cs analyses indicated that the sedimentation regimes were different between two southern and two northern stations of the island Funen, Denmark. Significant variations in vertical distribution, abundance and mortality of diapause eggs were found between the stations. Dating of the sediment cores suggested a ~70-year maximum age of viable eggs on the northernmost stations, and ~28 year at the southernmost stations. The eggs exhibited a significantly higher mortality rate at the southernmost stations compared with the northernmost, 0.35–0.53 year⁻¹ vs. 0.07–0.08 year⁻¹ with no systematic pattern among species. The differences in abundance, mortality and age of the diapause eggs are suggested to be due to the sediment characteristics in which they are buried.     

春、夏季长江口海域营养盐的时空分布特征及营养结构分析

2009年春季（5月）和夏季（8月）分别对长江口海水中的营养盐（DIN、SiO32--Si、PO43--P）进行调查,分析其时空分布特征,探讨其影响机理,并对富营养化水平进行了评价。结果表明：春、夏季表、底层DIN、SiO32--Si的平面分布有从近岸向离岸逐渐降低的特点,而PO43--P则表现出一种缓冲现象;各营养盐在表、底层的质量浓度春季均小于夏季,且DIN的主要存在形式均为NO3-_N;DIN、SiO32--Si主要来源于径流输入,PO43--P则有多种来源。春、夏季表、底层SiO32--Si/PO43--P、DIN/PO43--P均远大于Redfield值,具有营养盐比例不平衡的特征,且DIN/PO43--P、SiO32--Si/DIN、SiO32--Si/PO43--P在长江口海域的分布不均匀;从浮游植物吸收DIN/PO43--P的配比分析,PO43--P是春、夏季长江口海域潜在性营养限制因子;春、夏季E值均远大于富营养化阀值,该海域富营养化现象严重。     

Some aspects of the circulatory physiology of the spiny lobster Panulirus interruptus

The blood circulatory system and the circulatory dynamics of the spiny lobster Panulirus interruptus (Randall) have been examined in detail. A mean absolute blood pressure of 36.5 cm-H₂O and a mean pulse pressure of 27 cm-H₂O, show this species to have the highest pressure-driven circulation yet measured in decapod crustaceans. Mean blood velocities have been directly measured in intact animals for the first time. These velocities range from over 10 cm/sec in the large arteries to less than 1.0 cm/sec in the sinuses. Total blood volume is variable but averages near 30% of the wet weight, while heart volume averages 0.3% of the wet weight. The blood velocity and volume data are used to compute circulatory parameters such as cardiac output, stroke volume and turnover time. Comparisons with other animals suggest that the so-called “open-system” characteristic of crustaceans may be much more effective than previously supposed.     

Anchorage of embryos in Spirorbinae (Polychaeta)

Methods of incubation are taxonomically important in Spirorbinae. About half of the known species incubate in the operculum, but the remainder are usually described simply as incubating within the tube. Studies of tube incubation show that the embryos are anchored in various ways. They form an egg string, which is attached to the tube by a posterior filament in Spirorbis and Spirorbella; they adhere more generally to the tube wall in Circies and Paradexiospira; they are attached to specialised thoracic stalks in Protolaeospira, Helicosiphon and Romanchella; they adhere to the body surface in Metalaeospira and probably in Eulaeospira; they are not attached to either body or tube in Paralaeospira. Tube incubation is found predominantly in temperate or cold waters. In most species from the southern hemisphere, embryos are anchored to the bodies of the parents, but in most species from the northern hemisphere, embryos are fixed to the walls of the parent tubes.     

Trophodynamic function of copepods,appendicularians and protozooplankton in the late summer zooplankton community in the Skagerrak

The study was carried out in the Skagerrak during late summer when population development in the pelagic cycle culminated in the yearly maximum in zooplankton biomass. The cyclonic circulation of surface water masses created the characteristic dome-shaped pycnocline across the Skagerrak. The large dinoflagellate Ceratium furca dominated the phytoplankton biomass. Ciliates and heterotrophic dinoflagellates were the major grazers and, potentially, consumed 43–166% of daily primary production. The grazing impact of copepods was estimated from specific egg production rates and grazing experiments. The degree of herbivory differed between species (14–85%), but coprophagy (e.g. feeding on fecal pellets) and ingestion of microzooplankton were also important. The appendicularian Oikopleura dioica was present in lower numbers than copepods, but cleared a large volume of water. The grazing impact of copepods and O. dioica was estimated to 57±24% and 12±12% of daily primary production, respectively. Sedimentation of organic material (30 m) varied between 169 and 708 mg C m^–2 day^–1, and the contribution from the mesozooplankton (copepod fecal pellets and mucus houses with attached phytodetritus of O. dioica) was 5–33% of this sedimentation. Recycling of fecal pellets and mucus houses in the euphotic zone was 59% and 36%, respectively. However, there was a high respiration of organic material by microorganisms in the mid-water column, and 34% of the sedimenting material actually reached the benthic community in the deep, central part of the Skagerrak.     

Caste determination and differential diapause within the first brood of Halictus rubicundus in New York (Hymenoptera: Halictidae)

Summary The partially bivoltine, primitively eusocial sweat bee Halictus rubicundus produces two female castes, gynes and non-gynes, in its first brood in New York. Castes in this brood differentiate within the first few days of adult life, with gynes leaving the population to overwinter as early as mid-June (non-gynes further differentiate into replacement queen and worker subcastes, with older females typically dominant). Analysis of possible mechanisms of caste determination reveals that although gynes average significantly larger than non-gynes within the first brood, this appears largely due to a late mean emergence data coupled with an increase in the size of emerging females over the course of brood emergence, rather than a causal relationship. A strong correspondence between male abundance (relative to newly-emerged females) and the pattern of gyne production, along with data from dissections, suggests that females that mate when young become diapausing gynes, while those that do not mate promptly become non-gynes and do not diapause even though many mate later. Although alternatives to this simple mechanism cannot be ruled out entirely, it nevertheless offers profound implications for theoretical and empirical understanding of the evolutionary origins of the worker caste.     

A summer heat wave decreases the immunocompetence of the mesograzer, Idotea baltica

Extreme events associated with global change will impose increasing stress on coastal organisms. How strong biological interactions such as the host–parasite arms-race are modulated by environmental change is largely unknown. The immune system of invertebrates, in particular phagocytosis and phenoloxidase activity response are key defence mechanisms against parasites, yet they may be sensitive to environmental perturbations. We here simulated an extreme event that mimicked the European heat wave in 2003 to investigate the effect of environmental change on the immunocompetence of the mesograzer Idotea baltica. Unlike earlier studies, our experiment aimed at simulation of the natural situation as closely as possible by using long acclimation, a slow increase in temperature and a natural community setting including the animals’ providence with natural food sources (Zostera marina and Fucus vesiculosus). Our results demonstrate that a simulated heat wave results in decreased immunocompetence of the mesograzer Idotea baltica, in particular a drop of phagocytosis by 50%. This suggests that global change has the potential to significantly affect host–parasite interactions.     

Life-history parameters and vertical distribution of Maurolicus muelleri in Masfjorden in summer

Population characteristics, individual life-history variables, feeding and vertical distribution of the mesopelagic fish Müller's pearlside Maurolicus muelleri collected in 1990 in Masfjorden, western Norway, are reported as well as environmental variables from the fjord. Minimum size at maturity was far smaller than reported from previous investigations in the same region. Fecundity was size-dependent and total egg numbers were higher than reported from other investigations of M. muelleri world wide, while the number of maturing eggs was far lower than observed in the same region earlier. Food concentration in the fjord was an order of magnitude lower than previous early summer observations, and several factors indicated that feeding opportunities may have been low for a long period. Daily feeding rate (g prey g^-1 fish) decreased with increasing fish size. These observations fit well with a model of maximizing fitness by means of a flexible size at maturity. Minimum age at maturity seems to be achieved at the expense of fecundity. M. muelleri was concentrated in a 20 to 30 m deep sound scattering layer (SSL). The SSL stayed close to the surface during the night and at 100 to 180 m during the daytime. The vertical position of the SSL varied instantaneously with changes in surface light intensity, remaining at 10^-3 to 10^-4 mol m^-1 s^-1 at the top of the SSL. Stomach fullness was highest during the night; feeding intensity seems to have been peaked at dusk. Cladocerans were the main prey ranked by number, copepods by biomass. Intake of large copepods increased with fish size.     

Dynamics and physiology of saxitoxin production by the dinoflagellatesAlexandrium spp.

Toxin content (fmol cell^–1) and a suite of elemental and macromolecular variables were measured in batch cultures of the dinoflagellatesAlexandrium fundyense, A. tamarense andAlexandrium sp. from the southern New England region, USA. A different perspective was provided by semicontinuous cultures which revealed sustained, steady-state physiological adaptations by cells to N and P limitation. Two types of variability were investigated. In batch culture, changes in nutrient availability with time caused growth stage variability in toxin content, which often peaked in mid-exponential growth. A second type of variability that could be superimposed on growth stage differences is best exemplified by the high toxin content of cells grown at suboptimal temperatures. Calculations of the net rate of toxin production (R _tox ; fmol cell^–1 d^–1) for these different culture treatments and modes made it possible to separate the dynamics of toxin production from cell division. Over a wide range of growth rates, cells produced toxin at rates approximating those needed to replace losses to daughter cells during division. The exception to this direct proportionality was with P limitation, which was associated with a dramatic increase in the rate of toxin production as cells stopped dividing due to nutrient limitation in batch culture. Growth stage variability in batch culture thus reflects small imbalances (generally within a factor of two) between the specific rates of toxin production and cell division. N limitation and CO₂ depletion both affect pathways involved in toxin synthesis before those needed for cell division; P limitation does the opposite. The patterns of toxin accumulation were the same as for major cellular metabolites or elemental pools. The highest rates of toxin production appear to result from an increased availability of arginine (Arg) within the cell, due to either a lack of competition for this amino acid from pathways involved in cell division or to increased de novo synthesis. There were no significant changes in toxin content with either acclimated growth at elevated salinity, or with short term increases or decreases of salinity. These results demonstrate that toxin production is a complex process which, under some conditions, is closely coupled to growth rate; under other conditions, these processes are completely uncoupled. Explanations for the observed variability probably relate to pool sizes of important metabolites and to the differential response of key biochemical reactions to these pool sizes and to environmental conditions.     

河北省夏玉米气候适宜度及其变化特征分析

采用逐日气象要素和统计方法,建立了河北省夏玉米（Zea Mays）各生育期气候适宜度评价模型,计算了河北省1981—2010年逐年夏玉米各生育期气温、降水、日照、气候适宜度值,并对夏玉米各生育期气候适宜度特征及变化趋势进行了分析。结果表明：夏玉米生长期间气温适宜度最高,日照次之,降水最低且变异系数最大。气温适宜度以夏玉米灌浆期最低,变异系数最大;日照和降水适宜度均以抽雄期最低且变异系数最大。多年适宜度变化趋势为：全生育期日照适宜度明显下降（下降速率为0.047/10a）;气温适宜度基本持平;降水适宜度波动较大,无明显变化规律。幼苗和灌浆期气候适宜度呈下降趋势（下降速率分别为0.015/10a,0.024/10a）,其中幼苗期气候适宜度下降由期间气温和日照适宜度下降引起;灌浆期气候适宜度下降由日照和降水适宜度下降引起。