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Temporal fluctuations of abundance (or emergence) in small benthic and planktonic crustaceans were studied in shallow subtidal
waters (1.5 to 3.5 m in tide height). The abundances were more or less rhythmic, and showed wide diversity ranging from very
clear nocturnal patterns to patterns in sychrony with the tidal cycle alone. These abundance patterns were classified into
categories relating to the degree of synchrony with day/night and tidal cycles. Nocturnal patterns were especially strong
in benthic crustaceans, which would be inactive during the daytime, being attached to algae and stones or disappearing into
rock crevices, and actively swim in the water at night. Mysis larvae also showed a clear nocturnal pattern. Their lifestyle
might be similar to that of many benthic animals. Other planktonic crustaceans drifting in the water showed weak nocturnal
patterns. In some planktonic crustaceans (e.g., Calanoida), the ratio of abundance in the surface and bottom samples was reversed
between day and night. Their pattern might be a manifestation of weak diel vertical movement between day and night. Furthermore,
most patterns of zooplankton and benthos were modified in synchrony with tides to various degrees. Small crustaceans may respond
to changes of hydrologic variables fluctuating with the tides, which may exogenously produce a weak tidal component in their
emergence patterns.
Received: 12 January 1998 / Accepted: 29 August 1998 相似文献
2.
Fractionation and solubility of cadmium in paddy soils amended with porous hydrated calcium silicate 总被引:7,自引:0,他引:7
Previous studies have shown that porous hydrated calcium silicate (PS) is very effective in decreasing cadmium (Cd) content in brown rice. However, it is unclear whether the PS influences cadmium transformation in soil. The present study examined the effect of PS on pH, cadmium transformation and cadmium solubility in Andosol and Alluvial soil, and also compared its effects with CaCO3, acidic porous hydrated calcium silicate (APS) and silica gel. Soil cadmium was operationally fractionationed into exchangeable (Exch), bound to carbonates (Carb), bound to iron and manganese oxides (FeMnOx), bound to organic matters (OM) and residual (Res) fraction. Application of PS and CaCO3 at hig rates enhanced soil pH, while APS and silica gel did not obviously change soil pH. PS and CaCO3 also increased the FeMnOx-Cd in Andosol and Carb-Cd in Alluvial soil, thus reducing the Exch-Cd in the tested soils. However, PS was less effective than CaCO3 at the same application rate. Cadmium fractions in the two soils were not changed by the treatments of APS and silica gel. There were no obvious differences in the solubility of cadmium in soils treated with PS, APS, silica gel and CaCO3 except Andosol treated 2.0% CaCO3 at the same pH of soil-CaC12 suspensions. These findings suggested that the decrease of cadmium availability in soil was mainly attributed to the increase of soil pH caused by PS. 相似文献
3.
The circatidal rhythm of intertidal animals may reflect the inequality of the tides. In addition, a light-sensitive mechanism
may be involved in their internal timing systems. To test these hypotheses, the larval release activity of the intertidal
crab Hemigrapsus sanguineus was monitored under different light conditions in the laboratory. Under a 24-h light–dark (LD) cycle with the phase similar
to the field, the activity coincided with the times of high tide in the field and showed a tidal rhythm. This rhythm free-ran
in constant, dim-light conditions, suggesting that the timing is controlled by an endogenous clock. When the population was
exposed to a 24-h LD cycle with the phase changed from that in the field, the tidal rhythm was phase-shifted; while the light
cycle advanced in phase from the field caused a phase-advance of the rhythm, that delayed in phase induced a phase-delay of
the rhythm. Thus, a light-response mechanism is definitely involved in circatidal timing systems. But the population rhythm
showed a large variability among individuals, associated with the phase-shift, and the magnitude of the phase-shift did not
accurately correspond to that of the light cycle. These results suggest that the light-response system can control the phase
of the rhythm less stronger than that in estuarine crabs. Most releases occurred at higher high tides, but the release of
some females obviously occurred at lower high tides. The larval release pattern thus could not be accounted for by a simple
synchrony with higher high tides. Hatching of H. sanguineus occurred after a “hatching program” of 49.5 to 52.5 h. This program is initiated by some factor (hatching-program inducing
stumuli: HPIS) transmitted from the female to the embryos. We speculated that this factor is effectively transmitted to the
embryos when the habitat is exposed to air, i.e., at lower low-tide periods, and that once each embryo is stimulated, hatching
occurs synchronously 2 d later during high tide. The release of HPIS is probably controlled by the circatidal clock of the
female, and the 24-h LD cycle may participate in shifting this timing to the opposite low tide.
Received: 14 January 1997 / Accepted: 18 February 1997 相似文献
4.
Huimin Wang Nobuko Saigusa Susumu Yamamoto Hiroaki Kondo Takashi Hirano Atsushi Toriyama Yasumi Fujinuma 《Atmospheric environment (Oxford, England : 1994)》2004,38(40):7021-7032
Larch forests are distributed extensively in the east Eurasian continent and are expected to play a significant role in the terrestrial ecosystem carbon cycling process. In view of the fact that studies on carbon exchange for this important biome have been very limited, we have initiated a long-term flux observation in a larch forest ecosystem in Hokkaido in northern Japan since 2000. The net ecosystem CO2 exchange (NEE) showed large seasonal and diurnal variation. Generally, the larch forest ecosystem released CO2 in nighttime and assimilated CO2 in daytime during the growing season from May to October. The ecosystem started to become a net carbon sink in May, reaching a maximum carbon uptake as high as 186 g C m−2 month−1 in June. With the yellowing, senescing and leaf fall, the ecosystem turned into a carbon source in November. During the non-growing season, the larch forest ecosystem became a net source of CO2, releasing an average of 16.7 g C m−2 month−1. Overall, the ecosystem sequestered 141–240 g C m−2 yr−1 in 2001. The NEE was significantly influenced by environmental factors. Respiration of the ecosystem, for example, was exponentially dependent on air temperature, while photosynthesis was related to the incident PAR in a manner consistent with the Michaelis–Menten model. Although the vapor pressure deficit (VPD) was scarcely higher than 15 hPa, the CO2 uptake rate was also depressed when VPD surpassed 10 hPa. 相似文献
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