Biology of the upper-slope cephalopod<Emphasis Type="Italic"> Octopus salutii</Emphasis> from the western Mediterranean Sea

A total of 310 individuals (124 males, 185 females, 1 indeterminate) of the octopod Octopus salutii caught throughout the year by bottom trawlers from 25 to 800 m depth in the western Mediterranean were analysed to study some general aspects of its biology. Octopus sizes ranged from 4.0 to 13.0 cm ML and 3.5 to 16.5 cm ML in males and females, respectively. The species inhabits the lower continental shelf and upper slope, primarily between 250 and 500 m depth. The scarcity of small-sized individuals in the samples and the predominance of males and females >8 and >9 cm ML, respectively, suggest two interpretations: (1) juveniles inhabit grounds inaccessible to, or unsampled by, trawlers, or they avoid capture owing to behavioural aspects; or (2) the species meet in the trawling grounds for reproduction, because in the sizes described the majority of individuals have begun sexual maturation. The reproductive period was found to occur during spring and summer. The stomach content analysis revealed a diet composed of 33 different prey items belonging to three major taxonomic groups (crustaceans, fishes and cephalopods). Quantitatively, crustaceans (Decapoda Reptantia and Natantia groups) were the most important prey, appearing in 87% of the stomachs, followed by fish (25%) and cephalopods (10%). Finally, the paper presents data on mantle length–total weight, gonad weight–total weight and ligulae length–total weight relationships, and utilises different indexes (gonadosomatic, hepatosomatic, fullness weight and emptiness) to describe changes through the three maturity stages of both sexes.Communicated by S.A. Poulet, Roscoff     

Effects of changes in water salinity upon exercise and cardiac performance in the European seabass (<Emphasis Type="Italic">Dicentrarchus labrax</Emphasis>)

The European seabass is an active euryhaline teleost that migrates and forages in waters of widely differing salinities. Oxygen uptake (M_O2) was measured in seabass (average mass and forklength 510 g and 34 cm, respectively) during exercise at incremental swimming speeds in a tunnel respirometer in seawater (SW) at a salinity of 30 and temperature of 14°C, and their maximal sustainable (critical) swimming speed (U_crit) determined. Cardiac output (Q) was measured via an ultrasound flow probe on their ventral aorta. The fish were then exposed to acute reductions in water salinity, to either SW (control), 10, 5, or freshwater (FW, 0), and their exercise and cardiac performance measured again, 18 h later. Seabass were also acclimated to FW for 3 weeks, and then their exercise performance measured before and at 18 h after acute exposure to SW at 30. In SW, seabass exhibited an exponential increase in M_O2 and Q with increasing swimming speed, to a maximum M_O2 of 339±17 mg kg^–1 h^–1 and maximum Q of 52.0±1.9 ml min^–1 kg^–1 (mean±1 SEM; n=19). Both M_O2 and Q exhibited signs of a plateau as the fish approached a U_crit of 2.25±0.08 bodylengths s^–1. Increases in Q during exercise were almost exclusively due to increased heart rate rather than ventricular stroke volume. There were no significant effects of the changes in salinity upon M_O2 during exercise, U_crit or cardiac performance. This was linked to an exceptional capacity to maintain plasma osmolality and tissue water content unchanged following all salinity challenges. This extraordinary adaptation would allow the seabass to maintain skeletal and cardiac muscle function while migrating through waters of widely differing salinities.Communicated by S.A. Poulet, Roscoff     

Correlation between photosensitivity and downwelling irradiance in mesopelagic crustaceans

The current study determined behavioral and electrophysiological photosensitivities for three species of mesopelagic crustaceans: Pasiphaea multidentata Esmark, 1866 (Decapoda: Pasiphaeidae), Sergestes arcticus Kröyer, 1855 (Decapoda: Sergestidae), and Meganyctiphanes norvegica M. Sars, 1857 (Euphausiacea: Euphausiidae). In addition, in situ quantifications of the species vertical distributions in relation to downwelling irradiances were also determined in two locations in the northwest Atlantic Ocean, Wilkinson Basin (WB) and Oceanographer Canyon (OC). Data are from six 2-week cruises between June and September from 1995 to 2001. P. multidentata and M. norvegica were the most abundant large crustaceans in WB, and S. arcticus and M. norvegica were the most abundant large crustaceans in OC. The behavioral light sensitivity thresholds of P. multidentata and M. norvegica from WB were both 10⁷ photons cm^–2 s^–1 and those of S. arcticus and M. norvegica from OC were both 10⁸ photons cm^–2 s^–1. Electrophysiologically, P. multidentata was significantly more sensitive than M. norvegica from either location, S. arcticus was significantly more sensitive than M. norvegica from OC, and M. norvegica from WB was significantly more sensitive than M. norvegica from OC. A correlation was found between electrophysiologically measured photosensitivity and downwelling irradiance, with the most sensitive species, P. multidentata and S. arcticus, associated with the lowest irradiance at daytime depths. The photosensitivities of M. norvegica collected from the clearer waters of OC were significantly lower than those of individuals collected from the more turbid WB waters. These results indicate that downwelling irradiance has a significant impact on interspecies and intraspecies vertical distribution patterns in the mesopelagic realm.Communicated by J.P. Grassle, New Brunswick     

Growth and grazing rates of the tintinnid ciliate<Emphasis Type="Italic"> Favella taraikaensis</Emphasis> on the toxic dinoflagellate<Emphasis Type="Italic"> Alexandrium tamarense</Emphasis>

Growth and feeding activities of the tintinnid ciliate Favella taraikaensis fed the toxic dinoflagellate Alexandrium tamarense were examined in laboratory experiments. Both growth and ingestion rates of F. taraikaensis as a function of the A. tamarense concentration were fitted to a rectangular hyperbolic equation. The maximum growth and ingestion rates of F. taraikaensis were 1.0 day^–1 and 2.8 cells ind. h^–1 (carbon specific ingestion rates: 3.5 day^–1), respectively, which are both included in the range of previous data reported for Favella spp. feeding on other algae. The gross growth efficiency (GGE) of F. taraikaensis ranged from 0.26 to 0.49 (mean value 0.40) at the concentration of 10–800 cells ml^–1, which is within the range of previous data on Favella spp. Also, the growth and ingestion rates and GGE of F. taraikaensis on A. tamarense were not significantly different from the values on another non-toxic dinoflagellate (Heterocapsa triquetra) at two different prey concentrations. This indicates that the toxicity of A. tamarense probably did not influence the feeding and growth activities of F. taraikaensis at concentrations of less than ca. 800 cells ml^–1. To evaluate the grazing by F. taraikaensis on A. tamarense blooms in the field, the population dynamics of A. tamarense were simulated based on the growth and ingestion parameters of F. taraikaensis. As a result, the grazing impact by F. taraikaensis was considered to potentially regulate the development of A. tamarense blooms. If the toxicity of A. tamarense does not influence the growth and feeding activities of F. taraikaensis, the occurrence of such grazer plankton are considered to be important for predicting the course of A. tamarense bloom dynamics under natural conditions.Communicated by T. Ikeda, Hakodate     

蔬菜土壤微生物种群数量与土壤重金属含量的关系

对呈贡县蔬菜土壤微生物种群数量和土壤重金属质量分数进行大田调查分析，结果表明，土壤微生物种群数量和微生物多样性指数变化较大，土壤微生物种群数量总体水平较高，但微生物多样性指数偏低，其中以细菌占较大的优势；土壤重金属对土壤微生物数量和微生物多样性均有一定的影响，其中土壤中Pb和Cu的质量分数与土壤微生物种群数量显著相关；土壤重金属综合污染指数与真菌／细菌个数比例、真菌／放线菌个数比例与微生物多样性指数均呈显著的指数相关。随着重金属综合污染指数的增加，微生物多样性指数呈指数式地迅速下降。     

论现代科学技术中的"生态化"

对现代科学技术所出现的“生态化”现象进行了初步探讨。首先，对生态学涵义的扩展和生态化研究方法进行了研究，认为其涵义已从生态学的生物学含义发展到现代生态学的新涵义，其方法就是研究在科学技术中的“对象”与“环境”的关系问题；在此基础上，对科学技术研究目标作了生态化表述，即要建设生态-经济-社会优质复合群；然后，对科学技术所出现的生态化理论与方法进行了初步研究，并对建设普遍优质的生态-经济-社会复合群理论及其应用进行了分析；最后，对生态化的研究方法进行了总结。     

Characterization of spring phytoplankton communities in the Río de La Plata maritime front using pigment signatures and cell microscopy

The surface abundance and species composition of phytoplankton communities were studied in a section across the continental shelf between the Río de La Plata and the oceanic waters of the Subtropical Convergence, during late spring (November 1999). Algal communities were examined using light microscopy and HPLC-derived (high-performance liquid chromatography) pigment concentrations. The CHEMTAX program was used to estimate the chlorophyll a (chl a) biomass of different algal classes. The inclusion of the most abundant members of the chl c pigment family (chl c₁, chl c₂, chl c₃ and chl c₂ monogalactosyldiacylglyceride esters) in the pigment matrix improved the CHEMTAX interpretation of field data. Using this novel approach four haptophyte populations were distinguished across the studied section, even though they had qualitatively similar pigment signatures, although one subtype lacked 19-hexanoyloxyfucoxanthin (Hex-Fuco). Five different phytoplankton assemblages, spatially segregated by the prevailing environmental conditions, were distinguished during the studied period. All of them showed a complex community structure, formed by a background of small-sized cells such as cyanobacteria, cryptophytes, haptophytes and prasinophyceans, on which diatom, cryptophyte or some haptophyte blooms were overlapped. In the estuarine assemblage, where maximum chl a concentrations where found, diatoms were always the dominant group (30–60% of total chl a), but cryptophytes (10–40%), prasinophyceans (2–20%) and dinoflagellates (2–12%) were also relevant. In the coastal assemblage diatoms were also the dominant group (35–45%), but haptophytes lacking Hex-Fuco were subdominant (20–35%). The continental shelf assemblage showed an almost exclusive dominance (90%) of haptophytes resembling the coccolithophorid E. huxleyi. Another haptophyte (Phaeocystis sp.) was dominant (75–85%) in the Malvinas Current assemblage. The Brazil Current assemblage was characterized by the codominance of cyanobacteria (45%) and haptophytes (35%). These results are discussed in relationship to the complex hydrographic features of the area.Communicated by O. Kinne, Oldendorf/Luhe     

Energy content at metamorphosis and growth rate of the early juvenile barnacle<Emphasis Type="Italic"> Balanus amphitrite</Emphasis>

The energetic cost of metamorphosis in cyprids of the barnacle Balanus amphitrite Darwin was estimated by quantification of lipid, carbohydrate and protein contents. About 38–58% (4–5 mJ individual^–1) of cypris energy reserves were used during metamorphosis. Lipids accounted for 55–65%, proteins for 34–44% and carbohydrates for <2% of the energy used. Juveniles obtained from larvae fed 10⁶ cells ml^–1 of Chaetoceros gracilis were bigger (carapace length: 560–616 µm) and contained more energy (5.56±0.10 mJ juvenile^–1) than their counterparts (carapace length: 420–462 µm; energy content: 2.49±0.20 mJ juvenile^–1) obtained from larvae fed 10⁴ cells ml^–1. At water temperatures of 30°C and 24°C and food concentrations of 10⁴ and 10² cells ml^–1 (3:1 mixture of C. gracilis and Isochrysis galbana) as well as under field conditions (26.9±3.1°C and 2.2±0.8 µg chlorophyll a l^–1), juveniles obtained from larvae fed the high food concentration grew faster than juveniles obtained from larvae fed low food concentration until 5 days post-metamorphosis. Laboratory experiments revealed a combined effect of early juvenile energy content, temperature and food concentration on growth until 5 days post-metamorphosis. After 10 days post-metamorphosis, the influence of the early juvenile energy content on growth became negligible. Overall, our results indicate that the energy content at metamorphosis is of critical importance for initial growth of juvenile barnacles and emphasize the dependency of the physiological performance of early juvenile barnacles on the larval exposure to food.Communicated by O. Kinne, Oldendorf/LuheAn erratum to this article can be found at     

Ecological genetics of the barnacle,<Emphasis Type="Italic"> Hexaminius foliorum</Emphasis>, within mangrove forests near Sydney,Australia

Spatial and temporal distribution of allozyme variation at three loci in a cohort of the barnacle, Hexaminius foliorum, living on leaves of Avicennia marina was studied from recruitment to adulthood at three geographical scales. Analysis of populations shortly after recruitment showed that there were significant divergences in allele frequencies at the coarsest geographical scale studied (between estuaries, 50 km apart, Wright's F statistic=0.016) and at the finest geographic scale (between sites, 50–100 m apart, Wright's F statistic=0.018). There was, however, no significant genetic divergence at an intermediate scale (between bays, 3–4 km apart, Wright's F statistic=0.002). The genetic differences between populations decreased over time due to the selection against the null homozygotes originally present at high frequency at two loci. There was sufficient mortality (ranging from 35.5 to 80%) between seasons to account for the deaths needed for the observed changes in allele frequencies. Differences in the genetic structure between estuaries may be the result of isolation and limited mixing of cyprid larvae among estuaries. Differences in the genetic structure between sites may be due to pre- and post-settlement mortality acting on H. foliorum.Communicated by G.F. Humphrey, Sydney     

广州市不同区域水稻质量状况及其污染源探讨

根据1999年度对部分水稻质量监测结果,认为产品质量为重污染级这一问题,于2001年再选择一些监测点开展水稻质量、生产环境质量监测和评价。结果表明,2001年度水稻质量仍存在受污染问题,污染因子为氟化物、铅、镉和汞,大气污染为主要原因,其次为水质污染。