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1.
Uptake rates of nitrate and phosphate were measured for four species and one variety of Porphyra from Long Island Sound (USA) at two temperatures and two nutrient medium concentrations at increasing intervals over a 24- or 48-h period. Maximum uptake rates found were: V30 μM0-1 h=73.8 μmol NO3 g−1 DW h−1 and V3 μM0-1 h=16.7 μmol PO4 g−1 DW h−1, in the two thinnest Porphyra. We found that the nitrate uptake rates were significantly greater at 30 μM than 3 μM NO3 concentration, and that the uptake rates decreased with time of exposure. Temperature (5, 15, and 25 °C) did not have as strong an effect on nitrate uptake rates as did nutrient concentration. Q10 values and uptake rates at four different nitrate concentrations indicated that nutrient uptake at 5 °C was initially an active process. After 24 h, the processes involved appeared passive as Q10 values were between 1.0 and 1.3 and nitrate uptake curves were linear. Nitrate uptake rates correlated positively with the surface area/volume (SA/V) ratio. No coherent trends were found for uptake of phosphate, except that the uptake rates were significantly higher in 30 μM NO3 medium as opposed to 3 μM NO3. We did not find any significant difference in uptake rate and pattern between the summer species Porphyra purpurea (Roth.) C. Agardh, the eurythermic Porphyra suborbiculata Kjellm., the winter species Porphyra rosengurttii J. Coll and J. Cox, and the two varieties of Porphyra leucosticta Thur. Le Jol. (both winter species). 相似文献
2.
This study reports temperature effects on paralarvae from a benthic octopus species, Octopus huttoni, found throughout New Zealand and temperate Australia. We quantified the thermal tolerance, thermal preference and temperature-dependent respiration rates in 1-5 days old paralarvae. Thermal stress (1 °C increase h−1) and thermal selection (∼10-24 °C vertical gradient) experiments were conducted with paralarvae reared for 4 days at 16 °C. In addition, measurement of oxygen consumption at 10, 15, 20 and 25 °C was made for paralarvae aged 1, 4 and 5 days using microrespirometry. Onset of spasms, rigour (CTmax) and mortality (upper lethal limit) occurred for 50% of experimental animals at, respectively, 26.0±0.2 °C, 27.8±0.2 °C and 31.4±0.1 °C. The upper, 23.1±0.2 °C, and lower, 15.0±1.7 °C, temperatures actively avoided by paralarvae correspond with the temperature range over which normal behaviours were observed in the thermal stress experiments. Over the temperature range of 10 °C-25 °C, respiration rates, standardized for an individual larva, increased with age, from 54.0 to 165.2 nmol larvae−1 h−1 in one-day old larvae to 40.1-99.4 nmol h−1 at five days. Older larvae showed a lesser response to increased temperature: the effect of increasing temperature from 20 to 25 °C (Q10) on 5 days old larvae (Q10=1.35) was lower when compared with the 1 day old larvae (Q10=1.68). The lower Q10 in older larvae may reflect age-related changes in metabolic processes or a greater scope of older larvae to respond to thermal stress such as by reducing activity. Collectively, our data indicate that temperatures >25 °C may be a critical temperature. Further studies on the population-level variation in thermal tolerance in this species are warranted to predict how continued increases in ocean temperature will limit O. huttoni at early larval stages across the range of this species. 相似文献
3.
The effects of inorganic nitrogen (N) source (NH4+, NO3− or both) on growth, biomass allocation, photosynthesis, N uptake rate, nitrate reductase activity and mineral composition of Canna indica were studied in hydroponic culture. The relative growth rates (0.05-0.06 g g−1 d−1), biomass allocation and plant morphology of C. indica were indifferent to N nutrition. However, NH4+ fed plants had higher concentrations of N in the tissues, lower concentrations of mineral cations and higher contents of chlorophylls in the leaves compared to NO3− fed plants suggesting a slight advantage of NH4+ nutrition. The NO3− fed plants had lower light-saturated rates of photosynthesis (22.5 μmol m−2 s−1) than NH4+ and NH4+/NO3− fed plants (24.4-25.6 μmol m−2 s−1) when expressed per unit leaf area, but similar rates when expressed on a chlorophyll basis. Maximum uptake rates (Vmax) of NO3− did not differ between treatments (24-35 μmol N g−1 root DW h−1), but Vmax for NH4+ was highest in NH4+ fed plants (81 μmol N g−1 root DW h−1), intermediate in the NH4NO3 fed plants (52 μmol N g−1 root DW h−1), and lowest in the NO3− fed plants (28 μmol N g−1 root DW h−1). Nitrate reductase activity (NRA) was highest in leaves and was induced by NO3− in the culture solutions corresponding to the pattern seen in fast growing terrestrial species. Plants fed with only NO3− had high NRA (22 and 8 μmol NO2− g−1 DW h−1 in leaves and roots, respectively) whereas NRA in NH4+ fed plants was close to zero. Plants supplied with both forms of N had intermediate NRA suggesting that C. indica takes up and assimilate NO3− in the presence of NH4+. Our results show that C. indica is relatively indifferent to inorganic N source, which together with its high growth rate contributes to explain the occurrence of this species in flooded wetland soils as well as on terrestrial soils. Furthermore, it is concluded that C. indica is suitable for use in different types of constructed wetlands. 相似文献
4.
Clavery Tungaraza Véronique Rousseau Christiane Lancelot Willy Baeyens 《Journal of experimental marine biology and ecology》2003,292(1):19-41
This paper documents ambient concentrations of nutrients in the Belgian coastal waters of the North Sea during the spring of 1996 and 1997. The paper elaborates the differences of uptake rates of oxidised nitrogen (NO3−) and reduced nitrogen (NH4 and urea) by Phaeocystis and diatoms. The nitrogen concentrations were dominated by NO3− with a maximum concentration of 30 μM (January 1997) and 40 μM (March 1996). In 1996, Phaeocystis dominated the spring biomass with a maximum of 521 μg C l−1, while maximum diatom biomass was 174 μg C l−1. In 1997, the maximum Phaeocystis spring biomass was 1600 μg C l−1 and diatom maximum biomass was below 100 μg C l−1. A maximum bacteria biomass of about 55 μg C l−1 was observed in mid-May 1996. The maximum nitrogen uptake rates were recorded during spring and were dominated by NO3− (0.005 h−1 in 1996 and 0.032 h−1 in 1997). Maximum specific NH4 uptake rates were between 0.005 h−1 in May 1996 and 0.006 h−1 in April 1997. The NO3− uptake rates displayed exponential decrease versus increasing ambient reduced nitrogen concentrations (ammonium and urea), whereas the reduced nitrogen uptake increased but never compensated the decreased nitrate uptake. The NH4 uptake kinetics of diatoms displayed lower vmax compared to Phaeocystis. Consequently, Phaeocystis showed ability to increase their NH4 uptake capacity when more NH4 became available while diatoms failed to do so, after ammonium had exceeded their saturation concentration (>1 μM). Although reduced nitrogen has a negative effect on the uptake of NO3−, Phaeocystis have more advantage than diatoms on the uptake of ammonium. This might be contributing to the biomass domination shown by Phaeocystis over extended periods in spring. 相似文献
5.
Su–Su Xia An–Wei Yu Li–Dan Zhao Hui–Ying Zhang Wei–Hong Zheng Jin–Song Liu 《Journal of thermal biology》2013
Basal metabolic rate (BMR) is thought to be a major hub in the network of physiological mechanisms connecting life history traits. Evaporative water loss (EWL) is a physiological indicator that is widely used to measure water relations in inter- or intraspecific studies of birds in different environments. In this study, we examined the physiological responses of summer-acclimatized Hwamei Garrulax canorus to temperature by measuring their body temperature (Tb), metabolic rate (MR) and EWL at ambient temperatures (Ta) between 5 and 40 °C. Overall, we found that mean body temperature was 42.4 °C and average minimum thermal conductance (C) was 0.15 ml O2 g−1 h−1 °C−1 measured between 5 and 20 °C. The thermal neutral zone (TNZ) was 31.8–35.3 °C and BMR was 181.83 ml O2 h−1. Below the lower critical temperature, MR increased linearly with decreasing Ta according to the relationship: MR (ml O2 h−1)=266.59–2.66 Ta. At Tas above the upper critical temperature, MR increased with Ta according to the relationship: MR (ml O2 h−1)=−271.26+12.85 Ta. EWL increased with Ta according to the relationship: EWL (mg H2O h−1)=−19.16+12.64 Ta and exceeded metabolic water production at Ta>14.0 °C. The high Tb and thermal conductance, low BMR, narrow TNZ, and high evaporative water production/metabolic water production (EWP/MWP) ratio in the Hwamei are consistent with the idea that this species is adapted to warm, mesic climates, where metabolic thermogenesis and water conservation are not strong selective pressures. 相似文献
6.
Jesús M. Mercado F.X. Niell Rui Santos 《Journal of experimental marine biology and ecology》2003,297(1):71-84
The affinity for dissolved inorganic carbon (DIC) and the mechanisms to use HCO3− as a source of DIC for photosynthesis were investigated in two morphotypes of Zostera noltii Hornem. Both morphotypes were collected at Ria Formosa lagoon (Southern Portugal) at two different levels in the intertidal. Affinity for DIC at saturating photon fluence rate (PFR), estimated as photosynthetic conductance for CO2 (gp(CO2)), was reduced by 75% in the Z. noltii plants adapted to shade conditions (lower intertidal) in comparison to the sun morphotype (45×10−6 and 182×10−6 m s−1, respectively), indicating that the plants acclimated to sun conditions (higher intertidal) had a higher capacity to use HCO3− as DIC source for photosynthesis. Since external carbonic anhydrase activity was negligible and a large inhibitory effect was produced by Tris buffer addition, this HCO3− use was attributed to the operation of H+ ATPases creating low pH zones in periplasmic space. The photosynthetic CO2-flux supported for this mechanism was calculated to be 53 μmol O2 m−2 s−1 in sun morphotype, about 80% out of maximum photosynthesis rate. In order to determine the possible photosynthetic energy cost of the HCO3− use, the effect of decreasing light on photosynthetic rates and gp(CO2) was estimated. Photosynthetic conductance decreased in both morphotypes at non-saturating PFR. This dependence of gp(CO2) on PFR indicated the existence of a positive interactive effect between DIC and PFR which was more pronounced in the shade morphotype since the ascending slope of O2 evolution vs. PFR curves at limiting PFRs was reduced from 7.2 to 2.3 mmol O2 mol photon−1 at 4 and 0.5 mol m−3 of DIC, respectively. 相似文献
7.
E.L. Allan P.W. Froneman A.N. Hodgson 《Journal of experimental marine biology and ecology》2006,337(1):103-108
The standard metabolic rate (SMR) of the caridean shrimp Palaemon peringueyi to changes in temperature (15-30 °C), salinity (0-45‰) and a combination thereof was investigated. The rate of oxygen consumption of the shrimp was determined using a YSI oxygen meter. At a constant salinity of 35‰ the respiration rate of P. peringueyi increased with an increase in temperature and ranged between 0.260 and 0.982 μl O2 mg wwt− 1 h− 1. The Q10 value over the temperature range 15-25 °C was estimated at 3.13. At a constant temperature of 15 °C the respiration rate of P. peringueyi also increased with an increase in salinity and ranged between 0.231 and 0.860 μl O2 mg wwt− 1 h− 1. For combination experiments the absence of any significant difference in the respiration rate of P. peringueyi at the four temperatures over the salinity range 15-35‰ suggests that the shrimp is well adapted to inhabiting environments characterised by variations in salinity and temperature such as those encountered within the middle and lower reaches of permanently open estuaries with substantial freshwater inflow. On the other hand, the total mortality of the shrimp recorded at salinities < 5‰ at all four temperatures suggests that the upper distribution of the shrimp may reflect physiological constraints. Similarly, the increase in the respiration rate of the shrimp at the four temperatures at salinities > 35‰ suggests that the shrimp may experience osmotic stress in freshwater deprived permanently open and intermittently open estuaries where hypersaline conditions may develop. 相似文献
8.
The resting metabolic rate (RMR) of seasonally-acclimated Mabuya brevicollis of various body masses was determined at 20, 25, 30, 35 and 40 °C, using open-flow respirometry. RMR (ml g−1 h−1) decreased with increasing mass at each temperature. RMRs increaProd. Type: FTPsed as temperature increased. The highest and lowest Q10 values were obtained for the temperature ranges 20–25 °C and 30–35 °C for the summer-acclimated lizards. The exponent of mass “b” in the metabolism-body mass relation ranged from 0.41 to 0.61. b values were lower in the autumn and winter-acclimated lizards than in spring and summer-acclimated lizards. Seasonal acclimation effects were evident at all temperatures (20–40 °C) for M. brevicollis. Winter-acclimated skinks had the lowest metabolic rates at different temperatures. The pattern of acclimation exhibited by M. brevicollis may represent a useful adaptation for lizards inhabiting subtropical deserts to promote activity during their active seasons. 相似文献
9.
In this study we assessed the growth, morphological responses, and N uptake kinetics of Salvinia natans when supplied with nitrogen as NO3−, NH4+, or both at equimolar concentrations (500 μM). Plants supplied with only NO3− had lower growth rates (0.17 ± 0.01 g g−1 d−1), shorter roots, smaller leaves with less chlorophyll than plants supplied with NH4+ alone or in combination with NO3− (RGR = 0.28 ± 0.01 g g−1 d−1). Ammonium was the preferred form of N taken up. The maximal rate of NH4+ uptake (Vmax) was 6–14 times higher than the maximal uptake rate of NO3− and the minimum concentration for uptake (Cmin) was lower for NH4+ than for NO3−. Plants supplied with NO3− had elevated nitrate reductase activity (NRA) particularly in the roots showing that NO3− was primarily reduced in the roots, but NRA levels were generally low (<4 μmol NO2− g−1 DW h−1). Under natural growth conditions NH4+ is probably the main N source for S. natans, but plants probably also exploit NO3− when NH4+ concentrations are low. This is suggested based on the observation that the plants maintain high NRA in the roots at relatively high NH4+ levels in the water, even though the uptake capacity for NO3− is reduced under these conditions. 相似文献
10.
Two extracellular chitinases (designated as Chi-56 and Chi-64) produced by Massilia timonae were purified by ion-exchange chromatography, ammonium sulfate precipitation, and gel-filtration chromatography. The molecular mass of Chi-56 was 56 kDa as determined by both SDS-PAGE and gel-filtration chromatography. On the other hand, Chi-64 showed a molecular mass of 64 kDa by SDS-PAGE and 28 kDa by gel-filtration chromatography suggesting that its properties may be different from those of Chi-56. The optimum temperature, optimum pH, pI, Km, and Vmax of Chi-56 were 55 °C, pH 5.0, pH 8.5, 1.1 mg mL−1, and 0.59 μmol μg−1 h−1, respectively. For Chi-64, these values were 60 °C, pH 5.0, pH 8.5, 1.3 mg mL−1, and 1.36 μmol μg−1 h−1, respectively. Both enzymes were stimulated by Mn2+ and inhibited by Hg2+, and neither showed exochitinase activity. The N-terminal sequences of Chi-56 and Chi-64 were determined to be Q-T-P-T-Y-T-A-T-L and Q-A-D-F-P-A-P-A-E, respectively. 相似文献
11.
《Environmental and Experimental Botany》2006,55(1-2):49-60
The effect of NH4+/NO3− availability on nitrate reductase (NR) activity in Phragmites australis and Glyceria maxima was studied in sand and water cultures with the goal to characterise the relationship between NR activity and NO3− availability in the rhizosphere and to describe the extent to which NH4+ suppresses the utilization of NO3− in wetland plants.The NR activity data showed that both wetland helophytes are able to utilize NO3−. This finding was further supported by sufficient growth observed under the strict NO3− nutrition. The distribution of NR activity within plant tissues differed between species. Phragmites was proved to be preferential leaf NO3− reducer with high NR activity in leaves (NRmax > 6.5 μmol NO2− g dry wt−1 h−1) under all N treatments, and therefore Phragmites seems to be good indicator of NO3− availability in flooded sediment. In the case of Glyceria the contribution of roots to plant NO3− reduction was higher, especially in sand culture. Glyceria also tended to accumulate NO3− in non-reduced form, showing generally lower leaf NR activity levels. Thus, the NR activity does not necessarily correspond with plant ability to take up NO3− and grow under NO3−-N source. Moreover, the species differed significantly in the content of compounds interfering with NR activity estimation. Glyceria, but not Phragmites, contained cyanogenic glycosides releasing cyanide, the potent NR inhibitor. It clearly shows that the use of NR activity as a marker of NO3− utilization in individual plant species is impossible without the precise method optimisation. 相似文献
12.
Jacques Clavier Laurent ChauvaudAntoine Carlier Erwan AmiceMatthijs Van der Geest Pierre LabrosseAhmed Diagne Christian Hily 《Aquatic Botany》2011,95(1):24-30
Community respiration and primary production were measured in a dense intertidal Zostera noltii bed on the Banc d’Arguin, Mauritania (West Africa) under aerial and submerged conditions. Metabolism was studied in situ in dark and transparent benthic chambers. CO2 fluxes in the air were measured over a series of short-term incubations (3 min) using an infrared gas analyzer. Dissolved inorganic carbon fluxes were calculated from concentration changes during one-hour underwater incubations. Air and underwater irradiance levels were measured every minute throughout the experiments. Carbon respiration was lower in the air (2.2 mmol m−2 h−1) than underwater (5.0 mmol m−2 h−1); similarly, a production-irradiance model fitted to the data indicated that gross maximal photosynthetic rate was markedly lower during emergence (6.0 mmol C m−2 h−1) than under water (42.7 mmol C m−2 h−1). The δ13C values observed in shoots indicated a decrease in atmospheric CO2 contribution, compared to dissolved inorganic carbon, in Z. noltii metabolism along a depth gradient within a single location. As the seagrass bed remains under a thin layer of water at low tide at the studied site, the large difference in primary production can be mainly attributed to photosynthesis inhibition by high pH and oxygen concentration, as well as to the negative feedback of self-shading by seagrass leaves during emersion. The observed differences in respiration can be explained by the oxygen deficit at night during low tide near the sediment surface, a deficit that is consistent with the abundance of anoxia-tolerant species. 相似文献
13.
Norway spruce (Picea abies (L.) Karst.) exhibits strong ecotypic variation along altitudinal gradients in morphological traits, e.g. slenderness of crowns or arrangement of second-order branches. We were interested whether montane and lowland morphotypes differ in a key trait for the survival in cold environments, i.e. frost hardiness, and asked: (i) are montane morphotypes more resistant to frost damage and (ii) do they have a lower risk of frost damage by late frosts in spring than lowland morphotypes?We used the electrolyte leakage-method to measure frost hardiness on a monthly basis from October 2006 to May 2007 in stands of the montane and lowland morphotypes at Mt. Brocken in the Harz Mountains, Germany.LT50 (i.e. the temperature that results in 50% of maximum electrolyte leakage) was assessed by freezing treatments in a frost chamber and was significantly influenced by morphotype, month and minimum ambient temperatures. LT50 was significantly lower in the montane than in the lowland morphotype, with −107 °C and −49 °C, respectively. However, the interactions between morphotype with minimum ambient temperature or month were not significant. Thus, as frost hardiness of the two morphotypes responded to temperature in the same way, both morphotypes can be supposed to be exposed to the same risk of frost damage during hardening in autumn and dehardening in spring. 相似文献
14.
Ricardo A. González Fernando Díaz Alexei Licea Ana Denisse Re L. Noemí Sánchez Zaul García-Esquivel 《Journal of thermal biology》2010
Final temperature preferendum of white shrimp adults were determined with acute and gravitation methods. The final preferendum was similar, independent of method (26.2–25.6 °C). A direct relationship was determined between the critical thermal maxima values and the acclimation temperatures (P<0.05). The end point of Critical Thermal Maxima (CTMax) for adults was defined as the loss of righting response (LRR). The acclimation response ratio (ARR) for adults of white shrimp had an interval of 0.36–0.76, values that agreed with others obtained for crustaceans from tropical and subtropical climates. The oxygen consumption rates increased significantly (P<0.05) from 39.6 up to 90.0 mg O2 kg−1 h−1 wet weight (w.w.) as the acclimation temperature increased from 20 to 32 °C. The range of temperature coefficient (Q10) of the white shrimp between 23 and 26 °C was the lower 1.60. The results obtained in this work are discussed in relation to the species importance in the reproductive scope and maintenance of breeders. 相似文献
15.
Sweet flag (Acorus calamus L.) and yellow flag (Iris pseudacorus L.) have been used increasingly in constructed wetlands (CWs) for treatment of eutrophic wastewater. In order to properly match plant species with the type of wastewater being treated, it is important to know the performance of plant species under different NO3−/NH4+ ratios. We investigated dry matter (DW) production and N content of A. calamus and I. pseudacorus under five NO3−/NH4+ ratios (100/0, 75/25, 50/50, 25/75, and 0/100) in a hydroponic system. Results showed that the two species exhibited different preferences for NO3− and NH4+. Total DW, shoot DW, and N content were greater with NO3−/NH4+ ratios of 50/50 and 75/25 than otherwise for A. calamus, but these parameters were only higher under the sole NO3− treatment in I. pseudacorus. We conclude that A. calamus could be best used for treating wastewater in constructed wetlands with NO3−/NH4+ ratios between 50/50 and 75/25, while I. pseudacorus for treating wastewater with NO3− only to achieve the highest biomass production and efficiency in the removal of N. 相似文献
16.
Growth chamber studies with soybeans (Glycine max [L.] Merr.) were designed to determine the relative limitations of NO3−, NADH, and nitrate reductase (NR) per se on nitrate metabolism as affected by light and temperature. Three NR enzyme assays (+NO3−in vivo, −NO3−in vivo, and in vitro) were compared. NR activity decreased with all assays when plants were exposed to dark. Addition of NO3− to the in vivo NR assay medium increased activity (over that of the −NO3−in vivo assay) at all sampling periods of a normal day-night sequence (14 hr-30 C day; 10 hr-20 C night), indicating that NO3− was rate-limiting. The stimulation of in vivo NR activity by NO3− was not seen in plants exposed to extended dark periods at elevated temperatures (16 hr-30 C), indicating that under those conditions, NO3− was not the limiting factor. Under the latter condition, in vitro NR activity was appreciable (19 μmol NO2− [g fresh weight, hr]−1) suggesting that enzyme level per se was not the limiting factor and that reductant energy might be limiting. 相似文献
17.
We investigated whether six arctic plant species have the potential to induce nitrate reductase (NR) activity when exposed to NO3
--nitrogen under controlled environment conditions, using an in vivo assay that uses the rate of NO2
--accumulation to estimate potential NR activity. We also assessed the effect of low root temperatures on NR activity, growth and nitrogen uptake (using 15N applications) in two of the selected species. Five of the six species (Cerastium alpinum, Dryas intergrifolia, Oxyria digyna, Saxifraga cernua and Salix arctica) were capable of inducing NR activity when exposed to solutions containing 0.5 mM NO3
- at 20°C for 10 days. Although in vivo NR activity was not induced in Saxifraga oppositifolia under controlled conditions, we conclude that it was capable of growing successfully on NO3
-, due to the presence of moderate rates of NR activity observed in both NH4
+-grown and NO3
--treated plants. Exposure of O. digyna and D. integrifolia to 3°C root temperatures for two weeks, with the shoots kept at 20°C, resulted in root and leaf NR activity rates of NO3
--treated plants being reduced to rates exhibited by NH4
+-grown plants. Although these decreases in NR in both species appeared to be due to limitations in NO3
--uptake and growth rate (rather than direct low-temperature inhibition of NR synthesis per se), direct low-temperature inhibition of root NR synthesis could not be ruled out. In contrast to the temperature insensitivity of NH4
+ uptake in D. integrifolia, NO3
--uptake in D. integrifolia was inhibited by low root temperatures. We conclude that the selected arctic species have the genetic potential to utilize NO3
--nitrogen, and that low root temperatures, in conjunction with other environmental limitations, may be responsible for the lack of induction of NR in D. integrifolia and Salix arctica under field conditions. 相似文献
18.
Kate K. Steger 《Journal of experimental marine biology and ecology》2007,344(2):181-192
The porcelain crab Petrolisthes elongatus is a particulate suspension feeding species common to coastal areas of New Zealand (NZ). Consistent with the responses of other suspension feeding species, it is likely to be negatively influenced by elevated suspended sediment concentrations. Laboratory experiments were conducted to quantify the effect of temperature (12 °C, 15 °C and 18 °C) and suspended sediment concentration (total particulate matter (TPM): low < 100 mg L− 1; medium 100-1000 mg L− 1; high > 1000 mg L− 1) on the clearance rate (CR in L h− 1), oxygen uptake rate (VO2 in mL h−1), net absorption efficiency (AE), and net energy budget (NEB in J h− 1) of P. elongatus across a range of sizes. Variation in CR and AE was independent of temperature and of body size, but were significantly different (P < 0.05) at low and medium suspended sediment concentrations compared with high suspended sediment concentrations. CR responded in a non-linear manner to changes in TPM, increasing with TPM up to a maximum value at medium-low concentrations (approximately 250 mg L− 1) and then decreasing thereafter. CR had almost completely shut down at TPM concentrations of > 1000 mg L− 1 and at particulate organic matter (POM) concentrations of > 250 mg L− 1. AE was zero at approximate TPM and POM values of 1200 mg L− 1 and 300 mg L− 1, respectively. VO2 was positively correlated with body size and with temperature, but was independent of TPM. NEB values for P. elongatus were low (approx 110 J g− 1 h− 1) at low sediment concentrations, were high (approx 320 J g− 1 h− 1) at medium sediment concentrations, and were negative (approx − 114 J g− 1 h− 1) at high sediment concentrations. These findings indicate that P. elongatus is likely to be food-limited at sediment concentrations of < 100 mg L− 1, and severely negatively affected at sediment concentrations of > 1000 mg L− 1, at least for the duration of such events which may persist for 2-3 days in coastal environments where this crab occurs. 相似文献
19.
M. Bartoli D. Longhi S. Como P. Magni P. Viaroli 《Journal of experimental marine biology and ecology》2009,381(2):105-113
The effects of short term hypoxia on bioturbation activity and inherent solute fluxes are scarcely investigated even if increasing number of coastal areas are subjected to transient oxygen deficits. In this work dark fluxes of oxygen (O2), dissolved inorganic carbon (TCO2) and nutrients across the sediment-water interface, as well as rates of denitrification (isotope pairing), were measured in intact sediment cores collected from the dystrophic pond of Sali e Pauli (Sardinia, Italy). Sediments were incubated at 100, 70, 40 and 10% of O2 saturation in the overlying water, with both natural benthic communities, dominated by the polychaete Polydora ciliata (11.100 ± 2.500 ind. m− 2), and after the addition of individuals of the deep-burrower polychaete Hediste diversicolor. Below an uppermost oxic layer of ~ 1 mm, sediments were highly reduced, with up to 6 mM of S2− in the 5 mm layer. Flux of S2− and O2 calculated from pore water gradients were 8.61 ± 1.12 and − 2.27 ± 0.56 mmol m− 2 h− 1, respectively. However, sediment oxygen demand (SOD) calculated from core incubation was − 10.52 ± 0.33 mmol m− 2 h− 1, suggesting a major contribution of P. ciliata to O2-mediated sulphide oxidation. P. ciliata also strongly stimulated NH4+ and PO43− fluxes, with rates ~ 15 and ~ 30 folds higher, respectively, than those estimated from pore water gradients. P. ciliata activity was significantly reduced at 10% O2 saturation, coupled to decreased rates of solutes transfer. The addition of H. diversicolor further stimulated SOD, NH4+ efflux and SiO2 mobilisation. Similarly to P. ciliata, the degree of stimulation of SOD and NH4+ flux by H. diversicolor depended on the level of oxygen saturation. TCO2 regeneration, respiratory quotients, PO43− fluxes and denitrification of added 15NO3− were not affected by the addition of H. diversicolor, but depended upon the O2 levels in the water column. Denitrification rates supported by water column 14NO3− and sedimentary nitrification were both negligible (< 0.5 µmol m− 2 h− 1). They were not significantly affected by oxygen saturation nor by bioturbation, probably due to the limited availability of NO3− in the water column (< 3 µM) and O2 in the sediments. This study demonstrates for the first time the integrated short term effect of transient hypoxia and bioturbation on solute fluxes across the sediment-water interface within a simplified lagoonal benthic community. 相似文献
20.
S. Nayar G.J. Collings S. Bryars 《Journal of experimental marine biology and ecology》2009,373(2):87-95
Productivity measurements from carbon uptake have been suggested as good indicators of the physiological health of seagrasses. As seagrasses acquire carbon from the surrounding water, the rate of uptake often provide a good measure of the efficiency at which seagrasses meet their resource demands for growth. This rate is often used to assess the photosynthetic efficiency of the plants, a proxy for the physiological status of seagrass. This has special relevance to the Adelaide region as over 5000 ha of seagrasses have been lost from Adelaide coastal waters over the last 70 years, with much of this loss attributed to nutrient inputs from wastewater, industrial and stormwater discharges. This study used an in-situ inorganic carbon isotope-labelling and spike approach to obtain ecologically relevant estimates of seasonal variability in carbon uptake and its allocation in two species of temperate seagrass common to this coast (Amphibolis antarctica and Posidonia angustifolia). Uptake of carbon by the seagrass complex (leaves, roots, phytoplankton and epiphytes) was affected by both season and species. Carbon uptake rates of phytoplankton were generally higher than other components of the system. Uptake rates ranged from 0.01 mg C g− 1 DW h− 1 (summer) to 0.61 mg C g− 1 DW h− 1 (spring) in Posidonia and 0.02 mg C g− 1 DW h− 1 (summer) to 0.93 mg C g− 1 DW h− 1 (winter) in Amphibolis. Carbon uptake by the Amphibolis complex was higher than in the Posidonia complex. The Amphibolis complex had higher uptake rates in summer whereas the Posidonia complex was higher in spring. Fine sediments probably from a nearby dredging operation, are likely to have resulted in lower carbon uptake and a reduction in the above-ground and below-ground biomass in summer. 相似文献