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481.
A method was developed for measurement of active oxygen production in embryonic stages of the brown seaweed Fucus spiralis, using the label CM-DCFH-DA. Active oxygen species convert the label into the green fluorescent CM-DCF (exc/em 488/530 nm)
that is detected via confocal laserscan microscopy and quantitative image analysis. Loading of the label did not harm the
embryos; loading efficiency was age-independent, and the esterases needed for conversion to CM-DCFH were not inhibited by
the effective UV dose (2 W m−2) applied in the experiments. After correction for daily variation of the laser power, and calibration with DCF standard solutions,
this automated analysis of confocal images rendered active oxygen concentrations in fucoid embryos (μM DCF). An experiment
was designed for the assessment of active oxygen production following irradiance stress in the light-sensitive embryos. Dim-light-acclimated,
1-, 2- and 4-day-old embryos were transferred for 60 min to defined high-light conditions (4π-irradiance 300 μmol photons
m−2 s−1), optionally without UV radiation, including UVA, or including UVA plus UVB. PSII yield measurements (PAM fluorometer) were
carried out in order to assess the degree of photoinhibition under these light conditions. The imposed light stress initially
caused a rapid decrease of the PSII yields (ΦP). With increasing embryo age, minimum ΦP values attained under light stress remained higher. Consequently, electron transport rates (ETR) would increase with embryo
age, i.e., with the development of their photosynthetic apparatus. Active oxygen production increased with ETR, and when UVB
was included, relatively greater amounts of active oxygen were produced. A slow, second-phase decrease of ΦP under light stress that was proportional to active oxygen production indicated that some photooxidative damage was caused,
in particular during UVB exposure. Recovery from light stress was a rapid process in the absence of UVB; in such cases ΦP was almost restored to the initial values within 60 min. The relative state of recovery of ΦP was correlated with both the effective UV dose and active oxygen production rate (DCF). Recovery was slowest in embryos exposed
for 60 min to an experimental UVB dose, which was representative of a situation at low tide, on a sunny day. The results suggest
that active oxygen may cause an in situ inhibition of growth of the earliest life stages of F. spiralis.
Received: 26 January 2000 / Accepted: 4 September 2000 相似文献
482.
We examined the vertical distributions of scallop (Placopecten magellanicus) veligers in deep (0.6 m diameter, 9.5 m deep) polyethylene mesocosms from December 1991 to January 1992. In the mesocosms
temperature stratification varied from 0 to 1.5 °C. Profiles of vertical distribution revealed several repeated patterns.
Peaks in veliger numbers often appeared at the water surface and just above the thermocline. Higher density patches were seen
below the surface peaks, and revealed the presence of bio-convective cells. Distribution away from these discontinuities was
usually even. Distribution of veligers was affected by thermoclines above 1.0 °C. Responses to thermoclines varied with larval
age and time of day, and 28 to 30 d veligers passed in both directions through a 1.5 °C thermocline. We conclude that larval
behaviour is a major determinant of whether veligers pass through a thermocline. Kinematic viscosity may play a role in perception
of temperature changes. Two potential consequences of such behaviour are (1) remaining in more productive upper water layers,
where feeding opportunities are enhanced, and (2) increased horizontal transport in the region of the thermocline, which may
enhance recruitment.
Received: 15 May 1996 / Accepted: 11 May 2000 相似文献
483.
Anna-Kaija Eisto † Markku Kuitunen Antti Lammi ‡ Veli Saari Jukka Suhonen Susanna Syrjäsuo and Päivi M. Tikka§ 《Conservation biology》2000,14(5):1413-1421
Abstract: Data from several animal species and a few plant species indicate that small populations face an elevated risk of extinction. Plants are still underrepresented in these studies concerning the relation between population size and persistence. We studied the effect of population size on persistence among natural populations of the rare bellflower Campanula cervicaria in Finland. We monitored 52 bellflower populations for 8 years and found that the mean population size decreased from 24 to 14 during this period. Small populations with ≤5 individuals were more prone to losing all fertile plants than were larger ones. Reduction in population size was nevertheless unrelated to the degree of population isolation, measured as the distance to the nearest known population. To test the hypothesis that offspring fitness is lower in small populations, we germinated bellflower seeds from different-sized populations in a laboratory and found that seed germination ability was independent of population size. The seedlings raised from seeds of small populations grew faster than those taken from larger populations. Population size was negatively related to the amount of shade in the habitats. In conclusion, decreasing population sizes of C. cervicaria seemed not to be caused by lowered germination ability or growth rate in small populations; rather, population size reductions appeared to be due to closing of vegetation in the habitats. 相似文献
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489.
For this study, field measurements of current profiles, buoy trajectories and the lag of two tidal stations were performed to explore the flow characteristics of Taichung Harbour. in order to distinguish the effects of wind drift current on circulation inside Taichung Harbour, field surveys during both summer and monsoon (winter) season were completed separately. the speed of the drift current was about 3.5% that of the, wind speed, based on the field data. the horizontal dispersion coefficients were close to Bowden's (1965) formula for the tidal current. the water temperature showed a two-layer profile, with the mixing thickness about 4 to 6 metres for the upper layer. the corresponding Richardson number was about 70. the tidal lag between the two tidal stations was 9.68 minutes. All the results agree well with the theoretical results. 相似文献
490.
Use of otoliths and eye lenses for measuring trace-metal incorporation in fishes: a biogeographic study 总被引:1,自引:0,他引:1
The otoliths and lenses of the temperate damselfish Parma microlepis (Günther) (Pomacentridae) showed similar differences in trace-metal profile for selected locations along the coast of New
South Wales, Australia. Otoliths and lenses displayed a differential ability to accumulate metals. Metal concentrations were
ranked differently in the two structures (e.g. Sr > Ba > Pb > Rb > Hg in otoliths, and Hg > Sr ≃ Rb > Pb > Ba in lenses),
and where similar metals were accumulated, they were accumulated at vastly different concentrations (e.g. Ba concentrations
in otoliths are a thousand-fold greater than in lenses). Analyses of the otoliths and lenses of P. microlepis from locations close to Sydney and up to 100 km from the city were able to distinguish amongst these locations with respect
to a number of metals, namely Ba, Mn and Hg. Multivariate analyses of otolith and lens data gave similar results among locations
(agreement was obtained for 11 out of 15 pair-wise comparisons), and differences were attributable to the differential ability
of the two structures to accumulate metals such as Mn and Hg. Trace-metal differences between locations were found to coincide
with the proximity of sewage (including industrial waste) and petroleum storage facilities to the different locations.
Received: 23 June 1997 / Accepted: 4 August 1997 相似文献