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1.
D. Kim T. Okamoto T. Oda K. Tachibana K.S. Lee A. Ishimatsu Y. Matsuyama T. Honjo T. Muramatsu 《Marine Biology》2001,139(4):625-632
Although the ichthyotoxic mechanism of Chattonella marina is still unknown, several lines of evidence suggest that the reactive oxygen species (ROS), such as superoxide anion (O2-), hydrogen peroxide (H2O2), and hydroxyl radical (·OH), produced by C. marina are involved in the mortality of fish exposed to this flagellate. Recently, we found that the cell-free supernatant prepared from C. marina, which is considered to contain the glycocalyx, showed NADPH-dependent O2- generation. In this study, we prepared antiserum against the crude glycocalyx of C. marina. Using indirect immunofluorescence, it was confirmed that the antiserum specifically reacted with C. marina cells. In addition to C. marina, the antiserum also reacted with other raphidophycean flagellates such as Heterosigma akashiwo, Olisthodiscus luteus, and Fibrocapsa japonica, whereas no reactivity was observed against six other flagellate species tested. These results suggest that raphidophycean flagellates have common epitopes recognized by the antiserum. Interestingly, immunohistochemical analysis of paraformaldehyde-fixed gill lamellae from yellowtail exposed to C. marina revealed that the antiserum stained the surface of gill lamellae, while no such staining pattern was observed in control gill lamellae. These results suggest that the glycocalyx may be discharged when C. marina cells are inhaled into the fishes' mouths and then come into contact with the gill surface. Based on the present results, together with our previous findings, we propose that continuous accumulation of the discharged glycocalyx on the gill surface occurs during C. marina exposure, which may be responsible for the ROS-mediated severe gill tissue damage leading to fish death. 相似文献
2.
Microsensor studies of photosynthesis and respiration in the symbiotic foraminifer Orbulina universa 总被引:1,自引:0,他引:1
Oxygen and pH microelectrodes were used to investigate the microenvironment of the planktonic foraminifer Orbulina universa and its dinoflagellate endosymbionts. A diffusive boundary layer surrounds the foraminiferal shell and limits the O2 and proton transport from the shell to the ambient seawater and vice versa. Due to symbiont photosynthesis, high O2 concentrations of up to 206% air saturation and a pH of up to 8.8, i.e. 0.5 pH units above ambient seawater, were measured
at the shell surface of the foraminifer at saturating irradiances. The respiration of the host–symbiont system in darkness
decreased the O2 concentration at the shell surface to <70% of the oxygen content in the surrounding air-saturated water. The pH at the shell
surface dropped to 7.9 in darkness. We measured a mean gross photosynthetic rate of 8.5 ± 4.0 nmol O2 h−1 foraminifer−1. The net photosynthesis averaged 5.3 ± 2.7 nmol O2 h−1. In the light, the calculated respiration rates reached 3.9 ± 1.9 nmol O2 h−1, whereas the dark respiration rates were significantly lower (1.7 ± 0.7 nmol O2 h−1). Experimental light–dark cycles demonstrated a very dynamic response of the symbionts to changing light conditions. Gross
photosynthesis versus scalar irradiance curves (P vs E
o curves) showed light saturation irradiances (E
k) of 75 and 137 μmol photons m−2 s−1 in two O. universa specimens, respectively. No inhibition of photosynthesis was observed at irradiance levels up to 700 μmol photons m−2 s−1. The light compensation point of the symbiotic association was 50 μmol photons m−2 s−1. Radial profile measurements of scalar irradiance (E
o) inside the foraminifera showed a slight increase at the shell surface up to 105% of the incident irradiance (E
d).
Received: 26 January 1998 / Accepted: 11 April 1998 相似文献
3.
Short-term effects of temperature and irradiance on oxygenic photosynthesis and O2 consumption in a hypersaline cyanobacterial mat were investigated with O2 microsensors in a laboratory. The effect of temperature on O2 fluxes across the mat–water interface was studied in the dark and at a saturating high surface irradiance (2162 μmol photons
m−2 s−1) in the temperature range from 15 to 45 °C. Areal rates of dark O2 consumption increased almost linearly with temperature. The apparent activation energy of 18 kJ mol−1 and the corresponding Q
10 value (25 to 35 °C) of 1.3 indicated a relative low temperature dependence of dark O2 consumption due to mass transfer limitations imposed by the diffusive boundary layer at all temperatures. Areal rates of
net photosynthesis increased with temperature up to 40 °C and exhibited a Q
10 value (20 to 30 °C) of 2.8. Both O2 dynamics and rates of gross photosynthesis at the mat surface increased with temperature up to 40 °C, with the most pronounced
increase of gross photosynthesis at the mat surface between 25 and 35 °C (Q
10 of 3.1). In another mat sample, measurements at increasing surface irradiances (0 to 2319 μmol photons m−2 s−1) were performed at 25, 33 (the in situ temperature) and 40 °C. At all temperatures, areal rates of gross photosynthesis saturated
with no significant reduction due to photoinhibition at high irradiances. The initial slope and the onset of saturation (E
k = 148 to 185 μmol photons m−2 s−1) estimated from P versus E
d curves showed no clear trend with temperature, while maximal photosynthesis increased with temperature. Gross photosynthesis
was stimulated by temperature at each irradiance except at the lowest irradiance of 54 μmol photons m−2 s−1, where oxygenic gross photosynthesis and also the thickness of the photic zone was significantly reduced at 40 °C. The compensation
irradiance increased with temperature, from 32 μmol photons m−2 s−1 at 25 °C to 77 μmol photons m−2 s−1 at 40 °C, due to increased rates of O2 consumption relative to gross photosynthesis. Areal rates of O2 consumption in the illuminated mat were higher than dark O2 consumption at corresponding temperatures, due to an increasing O2 consumption in the photic zone with increasing irradiance. Both light and temperature enhanced the internal O2 cycling within hypersaline cyanobacterial mats.
Received: 30 November 1999 / Accepted: 11 April 2000 相似文献
4.
The production dynamics and carbon balance of Thalassia testudinum in the lower Laguna Madre, Texas, USA, were examined during the 1995 summer period based on in situ photosynthesis vs irradiance
(PI) measurements and continuous measurements of underwater photon-flux density (PFD). The validity of applying the H
sat model, used to calculate production for Zostera marina as the product of the maximum rate of photosynthesis (P
max) and daily hours of saturating irradiance (H
sat) was assessed for T. testudinum by comparison with integrated production estimates derived through numerical integration. Gross integrated production values
were combined with dark-respiration measurements of photosynthetic (PS) and non-photosynthetic (NPS) tissues and areal biomass
to generate daily whole-plant carbon balance. Production and whole-plant carbon balance are discussed in relation to surface
and underwater PFD measurements, biomass and other physical and chemical parameters collected during a 1 yr period from January
to December 1995. The H
sat model significantly underestimated production during all summer months, averaging 70% of integrated production over the entire
study period. Gross integrated production ranged between 11.5 mg C g−1 leaf dry wt d−1 in June (during a period of unseasonably low PFDs caused by a drift-alga mat covering the seagrass bed) to 26.7 mg C g−1 leaf dry wt d−1 in July. Modeled net carbon gain was highest in July at 454 mg C m−2 d−1 (1.4 g dry wt m−2 d−1), sufficient to account for measured rates of leaf production in the study area and representative of T. testudinum populations of low productivity. During part of the summer period, however, the population was in negative carbon balance.
The relatively low productivity of this population and the periods of negative carbon balance are attributed to low net photosynthesis:dark
respiration (P
net:R
d) ratios, sporadic low-light periods, the small fraction of PS tissue relative to whole-plant biomass (5 to 13%) and nutrient
limitation. Production models are sensitive to both light availability and the proportion of PS tissue supporting NPS biomass
as reflected in whole-plant P
net:R
d ratios.
Received: 13 August 1997 / Accepted: 6 March 1998 相似文献
5.
DMSP-lyase activity in five marine phytoplankton species: its potential importance in DMS production 总被引:7,自引:0,他引:7
Activity of DMSP-lyase, which cleaves dissolved DMSP (henceforth DMSPd-lyase), was examined in five axenically cultured phytoplankton species, including both DMSP-producing and non-DMSP-producing
species. High DMSPd-lyase activity was found in two DMSP producers, Heterocapsa triquetra strain NIES-7 and Scrippsiella trochoidea strain NIES-369 (Dinophyceae). The DMS production rates at 100 nM DMSPd were 0.5 fmol cell−1 min−1 for H. triquetra and 0.3 fmol cell−1 min−1 for S. trochoidea. In a non-DMSP producer, Heterosigma akashiwo strain NIES-6 (Raphidophyceae), the DMSPd-lyase activity was not found. Two DMSP-producing Prymnesiophyceae species, Isochrysis galbana strain CCMP-1323 and Gephyrocapsa oceanica strain NIES-353, did not show any obvious activity either, in contrary to other authors' findings on Phaeocystis sp., another DMSP-producing Prymnesiophyceae species. The comparison of the DMSPd-lyase activity of the two Dinophyceae species with bacterial DMSP consumption and DMS production activity in Tokyo Bay showed
that the DMSPd-lyase activity of H. triquetra and S. trochoidea could be an important mechanism for DMS production during their blooms.
Received: 9 April 1999 / Accepted: 10 December 1999 相似文献
6.
The physico-chemical microenvironment of larger benthic foraminifera was studied with microsensors for O2, CO2, pH, Ca2+ and scalar irradiance. Under saturating light conditions, the photosynthetic activity of the endosymbiotic algae increased
the O2 up to 183% air saturation and a pH of up to 8.6 was measured at the foraminiferal shell surface. The photosynthetic CO2 fixation decreased the CO2 at the shell down to 4.7 μM. In the dark, the respiration of host and symbionts decreased the O2 level to 91% air saturation and the CO2 concentration reached up to 12 μM. pH was lowered relative to the ambient seawater pH of 8.2. The endosymbionts responded immediately to changing light conditions,
resulting in dynamic changes of O2, CO2 and pH at the foraminiferal shell surface during experimentally imposed light–dark cycles. The dynamic concentration changes
demonstrated for the first time a fast exchange of metabolic gases through the perforate, hyaline shell of Amphistegina lobifera. A diffusive boundary layer (DBL) limited the solute exchange between the foraminifera and the surrounding water. The DBL
reached a thickness of 400–700 μm in stagnant water and was reduced to 100–300 μm under flow conditions. Gross photosynthesis
rates were significantly higher under flow conditions (4.7 nmol O2 cm−3 s−1) than in stagnant water (1.6 nmol O2 cm −3 s−1), whereas net photosynthesis rates were unaffected by flow conditions. The Ca2+ microprofiles demonstrated a spatial variation in sites of calcium uptake over the foraminiferal shells. Ca2+ gradients at the shell surface showed total Ca2+ uptake rates of 0.6 to 4.2 nmol cm−2 h−1 in A. lobifera and 1.7 to 3.6 nmol cm−2 h−1 in Marginopora vertebralis. The scattering and reflection of the foraminiferal calcite shell increased the scalar irradiance at the surface up to 205%
of the incident irradiance. Transmittance measurements across the calcite shell suggest that the symbionts are shielded from
higher light levels, receiving approximately 30% of the incident light for photosynthesis.
Received: 6 July 1999 / Accepted: 28 April 2000 相似文献
7.
Effect of temperature fluctuations and food supply on the growth and metabolism of juvenile sea scallops (Placopecten magellanicus) 总被引:1,自引:0,他引:1
On the eastern shore of Nova Scotia late summer atmospheric systems cause upwelling of shelf water; the associated temperature
variations of 10 °C with a 6 to 8 d period are comparable in magnitude to the seasonal variation. A laboratory study was undertaken
to assess the effects of these temperature fluctuations on sea scallop (Placopecten magellanicus) growth and metabolism. In a factorial design, scallops were subjected to constant (10 °C) or a variable (6 to 15 °C) 8 d
temperature cycle, and either a low (seston in filtered seawater) or high (seston supplemented with cultured phytoplankton)
food diet. During the 48 d experiment scallop mortality was low and growth positive in all treatments. Shell and total tissue
growth rate did not differ between temperature treatments, but growth in the high food treatments was 40 to 50% higher than
in the low food treatments. However, soft tissue (excluding adductor) growth did show a temperature treatment effect; growth
rates were significantly higher in the fluctuating temperature treatment, due in part to greater gonad development. Weight-standardized
rates of scallop oxygen consumption (V
sO2 , μmol O2 g−1 h−1) were 20 to 25% higher in high food than in low food treatments, consistent with the expected increase in respiration due
to the higher growth rates. Scallop metabolism did not acclimate to the fluctuating temperature cycle; V
sO2 and ammonium excretion (V
sNH+
4, μmol O2 g−1 h−1) remained dependent on ambient temperature throughout the experiment. V
sNH+
4 Q10 (2.77) was higher than V
sO2 Q10 (2.01) which was reflected in a decrease in the O:N ratio at 15 °C, indicating a shift toward increased protein catabolism
and a stressed state. At 10 °C, V
sO2 and V
sNH+
4 in the variable temperature treatments were 15 to 18% lower than in the constant temperature treatments, a difference that
was not detected in growth measurements. Results demonstrate that the metabolism of Placopecten magellanicus, unlike some bivalve species, is tightly coupled to fluctuations in ambient temperature. Although an absence of compensatory
acclimation had a minimal effect on growth in this study, if high temperatures were combined with low food conditions a reduction
in scallop production could result.
Received: 23 June 1998 / Accepted: 8 February 1999 相似文献
8.
We analysed growth of the Antarctic bryozoan Melicerita obliqua (Thornely, 1924) by x-ray photography and stable isotope analysis. M. obliqua colonies form one segment per year, thus attaining maximum length of about 200 mm within 50 years. In the Weddell and Lazarev
Seas, annual production/biomass ratio of M. obliqua is 0.1 yr−1, which is in the range of other Antarctic benthic invertebrate populations. Production amounts to 3.34 mg Corg m−2 yr−1 and 90.6 mg ash m−2 yr−1 on the shelf (100 to 600 m water depth), and to 0.13 mg Corg m−2 yr−1 and 36.8 mg ash m−2 yr−1 on the slope (600 to 1250 m water depth).
Received: 27 February 1998 / Accepted: 8 May 1998 相似文献
9.
The isopod Munnopsurus atlanticus occupies bathyal depths in both the Bay of Biscay (NE Atlantic; between 383 and 1022 m) and in the Catalan Sea (Northwestern
Mediterranean; between 389 and 1859 m). The species was dominant in both assemblages, reaching bathymetric peaks of abundance
on the upper part of the continental slope (400 m depth) in the Bay of Biscay and at ˜600 m in the Catalan Sea. Both the Atlantic
and the Mediterranean populations are bivoltines. Demographic analysis of the Bay of Biscay population revealed the production
of two generations per year with different potential longevity (5 mo for G1 and 11 mo for G2). The mean cohort-production interval (CPI) was estimated at 8 mo, and results of the demographic analysis were also used
to estimate production for the Catalan Sea populations. Mean annual density (D) and biomass (B) were higher in the Bay of
Biscay (D = 356.7 individuals 100 m−2; B = 0.803 mg dry wt m−2 yr−1) than in the Mediterranean (D = 16.3 individuals 100 m−2; B = 0.078 mg dry wt m−2 yr−1). Also, mean annual production was an order of magnitude higher in the Atlantic (between 4.063 and 4.812 mg dry wt 100 m−2 yr−1 depending on the method used) than in the Catalan Sea (between 0.346 and 0.519 mg dry wt 100 m−2 yr−1). M. atlanticus feeds on a wide variety of benthic and pelagic food sources. In both study areas, phytodetritus was not important in the
diet of M. atlanticus. In contrast, gut-content data suggested an indirect coupling with phytoplankton production in both areas via foraminiferans.
The life history and the recorded production are considered in respect to both the dynamics and levels of primary production
and the total mass flux in the respective study areas. Differences in the secondary production of both populations seemed
to be more consistently explained by differences in total mass flux than by differences in the primary production levels;
this is also consistent with the variety of food sources exploited by M. atlanticus.
Received: 22 February 1999 / Accepted: 3 February 2000 相似文献
10.
Recent studies demonstrated that the toxic red tide phytoplankton Chattonella spp. produce activated oxygen species such as superoxide anion (O
2
-
), hydrogen peroxide (H2O2), and hydroxyl radicals (·OH), which may be responsible for the toxicity of this flagellate. However, the mechanism behind the production of these oxygen radicals and H2O2 by Chattonella spp. is largely unknown, and the physiological significance of activated oxygen species for Chattonella spp. is also unclear. In the present study, we investigated the involvement of iron in the generation of O
2
-
and H2O2 by C. marina. The generation of O
2
-
by C. marina was related to the growth phase; the highest rate of O
2
-
production was observed during the exponential growth phase. However, no such increase during the exponential growth phase was observed in C. marina growing in an iron-deficient medium, even though the growth of C. marina was not significantly affected by iron-deficiency during the first 4 d. In addition, the iron chelator desferrioxamine (Desferal) strongly inhibited the generation of both O
2
-
and H2O2 by C. marina in a concentration-dependent manner. The growth of C. marina was also inhibited by Desferal. Furthermore, in the presence of 500 M Desferal, C. marina-induced growth inhibition of the marine bacteria Vibrio alginolyticus was almost completely abolished. These results suggest that iron is required for the generation of activated oxygen species by C. marina, as well as for its own growth. 相似文献
11.
The distribution and abundance of transparent exopolymer particles (TEP) was determined in and below pack ice of the Laptev
Sea from July to September 1995. Samples were collected from the lowermost 10 cm of ice floes and at 10 cm below the ice–water
interface. Abundance of bacteria, protists and TEP was determined, and the sea ice–water boundary layer was characterized
using temperature, salinity and molecular viscous shear stress. TEP, with a distinct size distribution signal, were found
in highest concentrations inside the sea ice, ranging from not detectable to 16 cm2 l−1 (median: 2.9 cm2 l−1). In the water, concentrations were one order of magnitude lower, ranged from below detection to 2.7 cm2 l−1 (median: 0.2 cm2 l−1) and decreased after the middle of August, whereas abundances of autotrophic flagellates (AF), diatoms, heterotrophic flagellates
(HF) and ciliates increased. The abundance of TEP decreased with its size in all samples following a power law relationship.
The relation of TEP to the microbial community differed between the sea ice and water, being positively correlated with bacteria
and diatoms in the ice and negatively correlated with HF in the sea water. The presence of a pycnocline significantly influenced
the abundance of organisms, diatom composition and TEP concentrations. Pennate diatoms dominated by Nitzschia frigida were most abundant inside the ice. Though bacteria have the potential to produce exopolymeric substances (EPS), the results
of this study indicate that the majority of TEP at the ice–water interface in first-year Arctic summer pack ice are produced
by diatoms.
Received: 19 August 1999 / Accepted: 4 July 2000 相似文献
12.
Artemia franciscana was grown on Isochrysis galbana Green (clone T. Iso) at saturated food concentrations (13 to 20 mg C l−1) for 11 d at 26 to 28 °C, and 34 ppt salinity. Three groups of brine shrimp were used in the feeding experiments: metanauplius
III and IV (Group 1), post-metanauplius II and III (Group 2) and post-metanauplius VIII (Group 3), corresponding to 4-, 7-
and 11-d-old animals, respectively. The ingestion rate, clearance rate and carbon balance were estimated for these stages
at different concentrations of 14C-labeled I. galbana ranging from 0.05 to 30 mg C l−1. The handling time of algae was determined for all three groups. The ingestion rate (I, ng C ind−1 h−1) increased as a function of animal size and food concentration. In all three groups, the ingestion rate increased to a maximum
level (I
max) and remained constant at food concentrations ≥10 mg C l−1 (saturated food concentrations). The clearance rate (CR, μl ind−1 h−1) increased with increasing food concentration up to a maximum rate (CR
max), after which it decreased for even higher food concentrations. The functional response of A. franciscana was most consistent with Holling's Type 3 functional response curve (sigmoidal model), which for the two oldest groups (Group 2
and 3) differed significantly from a Type 2 response (p < 0.05). The gut passage time for the three groups of A. franciscana, feeding on saturated food concentration (20 mg C l−1), varied between 24 and 29 min. As the nauplii developed to pre-adult stage the handling time of the algae increased as a
function of animal size. The assimilation rate (ng C ind−1 h−1) in the youngest stages (Group 1 and 2) increased with increasing food concentrations, reaching a maximum level close to
10 mg C l−1. At higher food concentrations the assimilation rate decreased, and the proportions of defecated carbon increased, reaching
60 to 68% in the post-metanauplius stages (Group 3). The assimilation efficiency (%) was high at the lowest food concentrations
in all three groups (89 to 64%). At higher concentrations, the assimilation efficiency decreased, reaching 56 to 38% at the
highest concentrations.
Received: 2 February 2000 / Accepted: 25 March 2000 相似文献
13.
Feeding, metabolism and growth in the Antarctic limpet, Nacella concinna (Strebel 1908) 总被引:2,自引:0,他引:2
Post-prandial increases in metabolism, the specific dynamic action of feeding (SDA), were evaluated in the Antarctic limpet
Nacella concinna. O2 consumption rose to a peak value 2.3 times higher than pre-feeding standard metabolic rates. This peak rise is low for marine
ectotherms, but is typical of polar species. There were three peaks in the SDA, the first lasted only for the 1st day, was
caused by handling, and was minor. The second was the major peak. It lasted from post-prandial days 4–9 inclusive, and accounted
for around 70% of the SDA response. The third peak lasted from day 11 to day 15 and accounted for 30% of the total SDA. A
15-day SDA is much longer than values for temperate species, but is again typical for polar marine ectotherms. NH3 excretion declined post-prandially from around 0.4 μmol animal−1 h−1 to values between 0.025 and 0.223 μmol animal−1 h−1 throughout the SDA. The total O2 consumed in the SDA was 90.2 μmol O2, which converts to 44.7 J of energy. This was 45–50% of the energy consumed in the meal (93.5 J). Pre-feeding O:N ratios,
after 26 days without food, were around 1, indicating protein as the sole metabolic substrate prior to initiating the SDA.
After feeding, O:N ratios rose to between 2.5 and 19, indicating significant use of lipid or carbohydrate from the food. Experiments
were conducted in ambient seawater with enhanced levels of Sr (SrCl added at 800 mg kg−1), and limpets were fed microalgal films also grown in enhanced Sr media. Sr incorporated in the shells during the experiment
allowed the measurement of shell increments deposited during the SDA. Between five and eight microgrowth bands were present
in the Sr-enhanced increments, which was similar to the number of days in the second SDA peak. The mean shell increment laid
down was 17.6 μm. Estimating tissue deposition from measured growth increments and published ash-free dry mass (AFDM) to length
relationships produced a value of 0.81 mg AFDM, which converted to 26.4 J of energy, or 25–30% of the energy ingested in the
meal. Estimates of growth increments associated with a single SDA have not previously been possible. Overall energy used in
the SDA and tissue deposition accounted for 75–80% of the energy ingested; the remainder was probably accounted for by unmeasured
costs such as mucus production.
Received: 6 June 2000 / Accepted: 20 September 2000 相似文献
14.
As part of the evaluation of fluxes between the water column and a rich benthic community of the Dover Strait (Eastern English
Channel), laboratory measurements of oxygen consumption were carried out on a common ophiurid, Ophiothrix fragilis (Abildgaard), from February 1993 to February 1995. The mean O2-consumption rate was evaluated at 0.31 mg O2 g−1 h−1 (ash-free dry weight). Simultaneous measurements of O2 consumption and CO2 production using the pH-alkalinity method revealed an average respiratory quotient of 0.69 proved suitable for converting
oxygen demand to carbon flux. A seasonal trend in respiration data was demonstrated by sinusoidal curves fitted to O2-uptake and CO2-release data as a function of time. The influence on respiration rate of two seasonal parameters (temperature and food availability)
is discussed; linear regression indicated a highly significant relationship between O2 consumption (or CO2 production) and temperature; both O2-consumption and CO2-production rates decreased with starvation. The average O:N ratio was estimated at 8.46, close to the theoretical value when
proteins constitute the catabolic substrate. The annual carbon respired by the O. fragilis community examined and the estimated annual primary production by phytoplankton indicate that the respiration of the O. fragilis community could supply 35% of phytoplankton carbon requirements.
Received: 1 August 1996 / Accepted: 4 September 1996 相似文献
15.
The amphipod Corophium multisetosum (Corophiidae) in Ria de Aveiro (NW Portugal). II. Abundance, biomass and production 总被引:2,自引:0,他引:2
The abundance and biomass of Corophium multisetosum Stock, 1952 were determined from benthic corer samples collected monthly over 1 yr in the upper reaches of Canal de Mira
(Ria de Aveiro, Portugal). Both density and biomass over the sampling period were negatively correlated with water temperature
and positively correlated with chlorophyll a concentration in the sediment. C. multisetosum density was significantly negatively correlated with plant biomass and positively correlated with salinity. The nature of
the sediment, favourable environmental conditions, high availability of food and low interspecific competition allowed the
population to reach a maximal density of 200 × 103 individuals m−2 and a maximal biomass (ash-free dry wt, AFDW) of 62 gAFDW m−2. The population was highly productive, especially during the autumn/winter period. Production, estimated by two different
methods (Hynes method: 251 gAFDW m−2 yr−1; Morin–Bourassa method: 308 gDW m−2 yr−1), was much higher than the values reported for other Corophium species. The annual P:Bˉ ratio (10) was high, but similar to values reported for Swedish populations of C. volutator and lower than the values estimated from Mediterranean populations of C. insidiosum.
Received: 8 October 1999 / Accepted: 22 June 2000 相似文献
16.
Cadmium accumulation in the female shore crab Carcinus maenas during the moult cycle and ovarian maturation 总被引:2,自引:0,他引:2
The influence of moulting and ovarian maturation on cadmium accumulation in the tissues of female shore crabs Carcinus maenas exposed to 1 mg Cd l−1 in the water was investigated. Cadmium accumulation in all tissues examined was markedly increased in crabs in the postmoult
stages (A and B) compared to crabs in all other moult stages. During the moult cycle, average cadmium accumulation in the
midgut gland ranged from 29 μg Cd g−1 dw at premoult stage (D2) to 589 μg Cd g−1 dw at postmoult stage (A). Average cadmium concentrations in the haemolymph ranged from 0.56 μg Cd ml−1 at intermoult stage (C4) to 4.6 μg Cd ml−1 at postmoult stage (A), while the gills accumulated from 103 μg Cd g−1 dw in intermoult stage (C3) to 352 μg Cd g−1 dw in postmoult stage (A). Cadmium concentration in gills and haemolymph was also significantly higher in crabs in late premoult
stage (D3) compared to C4-crabs, while midgut gland cadmium concentration remained elevated in C1- and C3- intermoult stages relative to C4. During ovarian maturation the cadmium accumulation in midgut gland, gills, ovaries and haemolymph decreased. Average cadmium
concentration in the midgut gland decreased from 63 μg g−1 dw in ovarian Stage I to 19 μg g−1 dw in ovarian Stage VI. The same pattern was observed for gills, haemolymph and ovaries. The present study demonstrates that
cadmium accumulation in the female shore crab strongly depends on the physiological status of the animal. A possible association
between physiological calcium requirements and cadmium accumulation during moulting is discussed.
Received: 20 January 2000 / Accepted: 20 July 2000 相似文献
17.
Andrew McMinn Andrew Pankowskii Chris Ashworth Ranjeet Bhagooli Peter Ralph Ken Ryan 《Marine Biology》2010,157(6):1345-1356
Primary production at Antarctic coastal sites is contributed from sea ice algae, phytoplankton and benthic algae. Oxygen microelectrodes
were used to estimate sea ice and benthic primary production at several sites around Casey, a coastal area in eastern Antarctica.
Maximum oxygen export from sea ice was 0.95 mmol O2 m−2 h−1 (~11.7 mg C m−2 h−1) while from the sediment it was 6.08 mmol O2 m−2 h−1 (~70.8 mg C m−2 h−1). When the ice was present O2 export from the benthos was either low or negative. Sea ice algae assimilation rates were up to 3.77 mg C (mg Chl-a)−1 h−1 while those from the benthos were up to 1.53 mg C (mg Chl-a)−1 h−1. The contribution of the major components of primary productivity was assessed using fluorometric techniques. When the ice
was present approximately 55–65% of total daily primary production occurred in the sea ice with the remainder unequally partitioned
between the sediment and the water column. When the ice was absent, the benthos contributed nearly 90% of the primary production. 相似文献
18.
One concept of evolutionary ecology holds that a living fossil is the result of past evolutionary events, and is adapted
to recent selective forces only if they are similar to the selective forces in the past. We describe the present environment
of the living coelacanth Latimeria chalumnae Smith, 1939 at Grande Comore, western Indian Ocean and report depth-dependent cave distribution, temperature, salinity and
oxygen values which are compared to the fish's distribution and its physiological demands. We studied the activity pattern,
feeding behaviour, prey abundance and hunting success to evaluate possible links between environmental conditions, feeding
ecology and evolutionary success of this ancient fish. Transmitter tracking experiments indicate nocturnal activity of the
piscivorous predator which hunts between approximately 200 m below the surface to 500 m depth. Fish and prey density were
measured between 200 and 400 m, both increase with depth. Feeding tracks and feeding strikes of the coelacanth at various
depths were simulated with the help of video and laser techniques. Along a 9447 m video transect a total of 31 potential feeding
strikes occurred. Assuming 100% hunting success, medium-sized individuals would obtain 122 g and large females 299 g of prey.
Estimates of metabolic rates revealed for females 3.7 ml O2 kg−1 h−1 and for males 4.5 ml O2 kg−1 h−1. Today coelacanths are considered to be a specialist deep-water form and to inhabit, with their ancient morphology, a contemporary
environment where they compete with advanced, modern fish.
Received: 5 July 1999 / Accepted: 11 November 1999 相似文献
19.
Polychaetes belonging to the genus Capitella are often present in high numbers in organic-rich sediments polluted with, e.g., oil components, and Capitella spp. may have a great impact on the biogeochemistry of these sediments. We examined the influence of Capitella sp. I on microbial activity in an organic-rich marine sediment contaminated with the polycyclic aromatic hydrocarbon, fluoranthene.
Capitella sp. I were added to microcosms (10 000 ind m−2) and the impact of a pulse-sedimentation of fluoranthene-contaminated sediment (3 mm layer) was studied for a period of 12
d after sedimentation. The sediment oxygen uptake and total sediment metabolism (TCO2 production) increased in cores with worms (71 to 131%), whereas the anaerobic activity, measured as sulfate reduction rate
12 d after sedimentation, was lower compared to cores without worms. The effect of fluoranthene on sulfate reduction was most
pronounced in the presence of worms, with a 34% reduction versus 16% in cores without worms. The reduced sulfur pools in cores
with worms were smaller than in cores without worms, suggesting that the reduced anaerobic activity was caused by increased
oxidation of the sediment, which may favor O2 and other electron-acceptors (e.g. NO3
−, Fe3+, Mn4+) in organic matter decomposition. The sediment oxygen uptake and TCO2 production did not show significant changes due to fluoranthene treatment, indicating that these parameters were either less
sensitive to fluoranthene stress or recovered more rapidly (i.e. within 48 h) than sulfate reduction rates. Bioturbation by
Capitella sp. I altered the depth profile of fluoranthene such that fluoranthene was found in deeper sediment layers (down to 2 cm)
where diffusional loss and microbial breakdown probably are reduced relative to surface layers. In cores without worms, fluoranthene
was found down to 1 cm, with 75% remaining in the upper 5 mm.
Received: 5 December 1996 / Accepted: 11 February 1997 相似文献
20.
Ammonium concentrations of ∼1 M are commonly cited as being the threshold for inhibition of NO3
− uptake, but the applicability of this threshold to phytoplankton from different taxonomic classes has rarely been examined.
Additionally, little is known about the influence of environmental variables (e.g. growth temperature) on the interaction
between ambient NH4
+ and NO3
− uptake. Four species of estuarine phytoplankton, two diatom [Chaetoceros sp., and Thalassiosira weissflogii (Grunow) Fryxell et Hasle] and two dinoflagellate [Prorocentrum minimum (Pavillard) Schiller, and Gyrodinium uncatenum Hulburt], were grown on NO3
− at several different temperatures (4, 10, 15, or 20 °C), and the impact of NH4
+ additions on NO3
− uptake/assimilation (non-TCA-extracted) and assimilation (TCA-extracted) was assessed. For all species at all temperatures,
NO3
− uptake/assimilation and assimilation rates decreased in a roughly exponential manner with increasing NH4
+ concentrations but were not completely inhibited even at elevated NH4
+ concentrations of 200 μM. Estimated half-inhibition concentrations (K
i) were significantly greater in the diatom species (mean ± SE; 2.70 ± 0.67 μM) than in the dinoflagellate species (1.26 ± 0.55 μM). Half-inhibition constants were positively related to temperature-limited relative growth rate although not significantly.
The observed inhibition of NO3
− uptake and assimilation, as a percentage of NO3
− uptake in the absence of NH4
+, averaged about 80% and ranged from 49 to 100%. For all species, a significant (P < 0.001) positive correlation was found between percent inhibition of NO3
− assimilation and temperature-limited relative growth rate. Two experiments on Chesapeake Bay phytoplankton during an April
1998 diatom bloom showed that in short-term (∼1 h) temperature manipulation experiments, percent inhibition of NO3
− uptake/assimilation was also positively related (P = 0.05) to experimental temperature. The observed relationships between temperature-limited relative growth rate and percent
inhibition of NO3
− assimilation rates for the species tested suggest that at the enzyme level, the inhibitory mechanism of NO3
− assimilation is similar among species, but at the whole cell level may be regulated by species-specific differences in the
accumulation of internal metabolites. These findings add not only to our understanding of species-specific variability and
the role of growth temperature, but also provide additional data with which to evaluate current models of NH4
+ and NO3
− interactions.
Received: 31 August 1998 / Accepted: 7 December 1998 相似文献