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1.
In this study, we explored the interactive effects of temperature and solar ultraviolet radiation (UVR) on the growth, pigment contents, photochemical efficiency and non-photochemical quenching (NPQ) of Pseudo-nitzschia pungens, which forms harmful algal blooms globally. Cells were first pre-acclimated to temperatures of 20°C, 25°C or 28°C for 10 days. They were then exposed to three different types of solar radiation for 60?min. We then measured the photochemical efficiency of the cells during the 60-min exposure and a 360-min recovery period under dim light (20?μmol?photons?m?2?s?1). In addition, we analysed the diural change in photochemical efficiency and NPQ over a 10-h period. We found that P. pungens that were exposed to higher temperatures in the short term (i.e. 20–25°C, 20–28°C and 25–28°C) or long term (i.e. 25–25°C and 28–28°C) exhibited lower levels of photoinhibition and faster recovery rates than samples exposed to a lower temperature (i.e. 20–20°C). This indicated that the deleterious effects of UVR can be minimised by both chronic and acute exposure to higher temperatures within the tolerated temperature range for P. pungens.  相似文献   

2.
ABSTRACT

The grounding of the MV Rena has highlighted the lack of information concerning the effects of oil-related compounds on New Zealand marine life. Yellowtail kingfish (YTK), Seriola lalandi, embryos were exposed in static incubations to the water-accommodated fraction (WAF) of Rena heavy fuel oil as well as a similar preparation treated with the commercial dispersant Corexit 9500. Mortality in WAF treatments generally increased in association with total polycyclic aromatic hydrocarbon (tPAH) concentration over a 24-h period. Physical abnormalities were observed in some of the larvae exposed to WAF for 48 h. There was no survival in dispersed oil treatments after 24 h of exposure. These treatments had greater tPAH concentrations (2–53?µgL?1) than equivalent WAF dilutions (0.2–1.5?µgL?1?tPAH). Indications are that significant morbidity is induced in YTK at ecologically relevant tPAH concentrations. This highlights the need for further research into oil and dispersant toxicity in New Zealand marine species.  相似文献   

3.
Tautog, Tautoga onitis, is an abundant species of fish in estuaries of the northeastern United States. Planktonic tautog larvae are abundant in summer in these estuaries, but there is little information on rates of growth of tautog larvae feeding on natural assemblages of food in the plankton. We examined abundance and growth of larval tautog and environmental factors during weekly sampling at three sites along a nearshore‐to‐offshore transect in Buzzards Bay, Massachusetts, USA during summer 1994. This is the first study of a robust sample size (336 larvae) to estimate growth rates of field‐caught planktonic tautog larvae feeding on natural diets, using the otolith daily‐growth‐increment method. The study was over the entire summer period when tautog larvae were in the plankton. The sampling sites contrasted in several environmental variables including temperature, dissolved oxygen (DO), and chlorophyll a concentration. There was a temporal progression in the abundance of tautog larvae over the summer, in relation to location and temperature. Tautog larvae were first present nearshore, with a pronounced peak in abundance occurring at the nearshore sites during the last 2 weeks in June. Larvae were absent at this time further offshore. From late June through August, larval abundance progressively decreased nearshore, but increased offshore although never approaching the abundance levels observed at the nearshore sites. The distribution and abundance of tautog larvae appeared to be related to a nearshore‐to‐offshore seasonal warming trend and a nearshore decrease in DO. Otoliths from 336 larvae ranging from 2.3 to 7.7 mm standard length had otolith increment counts ranging from 0 to 19 increments. Growth of larval tautog was estimated at 0.23 mm·day?1, and length of larvae prior to first increment formation was estimated at 2.8 mm indicating that first increment formation occurs 3–4 days after hatching at 2.2 mm. Despite spatial and temporal differences in environmental factors, there were no significant differences in growth rates at any of three given sites over time, or between sites. Because larval presence only occurred at a narrow range of temperature (17–23.5 °C) and DO (6.5–9.3 mg·l?1), in situ differences in growth did not appear to be because of differences in larval distribution and abundance patterns relative to these parameters.  相似文献   

4.
The sensitivity of abalone Haliotis midae larvae to low levels of toxicants was used to conduct a laboratoryscale experiment to determine the possibility of using chemical containment to prevent the escape of larvae from land-based culture systems, thereby reducing the environmental impact of farming operations. The cryoprotective agent, dimethyl sulphoxide or DMSO (Me2SO), was used as a toxicant and embryos were exposed to increasing concentrations (0–25.60 mol l–1) of DMSO for a period of 24 hours. Hatch-out rates of the control group (0.0% DMSO) did not differ from those obtained at 0.2% (2.56 mol l–1) and 0.4% (5.12 mol l–1) DMSO. An exposure level at and above 0.6% DMSO resulted in a significant decrease in the number of normal larvae. At an exposure concentration of 0.6% (7.68 mol l–1) DMSO, 65% (SE 3.0) of the fertilised eggs hatched, compared to only 10% (SE 2.0) at a concentration of 1.0% (12.80 mol l–1) DMSO. This study indicates the potential for use of DMSO as a form of chemical containment of abalone larvae, even at very low doses. It presents South African abalone farms with a chemical containment method that could potentially be used to prevent the unintentional escape of H. midae larvae from land-based operations.  相似文献   

5.
利用实验生态学方法研究不同个体大小的海蜇浮游幼体[平均伞径(2.5±0.1),(4.1±0.2),(11.7±0.5),(21.1±0.6)mm]对不同密度(10,30,50,80ind/L)的褐牙鲆卵[卵径(0.92±0.01)mm]和初孵仔鱼[全长(3.01±0.08)mm]的捕食率,解析海蜇浮游幼体对初孵仔鱼的捕食率随捕食时间(0.5,1,2,3,4,5h)的变化特征。结果表明,各个体组海蜇浮游幼体对卵的捕食率均显著低于对仔鱼的捕食率;它们对卵的捕食率与卵密度和海蜇个体大小的关系不显著,但对仔鱼的捕食率随海蜇个体大小及仔鱼密度的增大而显著升高;伞径21.1mm的个体对仔鱼的捕食率在开始捕食后1h时达到最大值[17.3ind/(predator.h)],此后随捕食时间的延长而逐渐下降。在自然水域中,如果二者发生时空上的匹配关系,海蜇浮游幼体对仔鱼的捕食可能影响褐牙鲆的早期存活及其资源补充量的变动。  相似文献   

6.
The effects of ozone-produced oxidants (OPO) on three developmental stages of the American oyster, Crassostrea virginica, were evaluated. Both straight-hinge (48-h post fertilisation) and setting pediveliger larvae were exposed to a series of OPO concentrations ranging from 0·05 to 0·30 mg/litre OPO (as total residual chlorine) at 25°C for 96 h. Mortality was used as the response parameter and results were quantitatively compared with the effects of chlorine-produced oxidants (CPO) obtained from the literature on these same developmental stages. Adult oysters (2- to 4-year class) were exposed to OPO concentrations ranging from 0·01 to 0·50 mg/litre at 15°C for 5 days and to the same concentration range at 25°C for two consecutive 6-day periods. Shell deposition and faecal matter accumulation were used as the response parameters for this stage.Straight-hinge larvae were significantly more sensitive to OPO than setting pediveliger larvae. Both larval stages were significantly more sensitive to CPO than to OPO. Shell deposition was significantly inhibited at all OPO concentrations for both 15°C and 25°C acclimated adult oysters. No significant differences were found between the shell deposition response of oysters at the two acclimation temperatures. Faecal matter accumulation was significantly reduced at OPO concentrations ≥ 0·05 mg/litre at both 15°C and 25°C. It was significantly (p < 0·05) greater for 25°C acclimated oysters than for 15°C acclimated oysters at OPO concentrations < 0·10 mg/litre but not at higher concentrations.  相似文献   

7.
Knowledge is limited on the fish larval assemblage in shallow lagoonal reefs along the Kenyan coast. Fish larvae from five lagoons, spanning 120 km on the Kenyan coast, were sampled in March 2007 and April 2008 to compare interannual spatial variations in species composition, abundance and diversity along the coast. In all, 2 644 fish larvae were sampled, comprising 26 families and 37 species in 2007 and 43 families and 73 species in 2008. The larval assemblage was dominated by Gobiidae, Blenniidae, Pomacentridae and Gerreidae during both years. Larvae hatched from non-pelagic mode of spawning constituting 92% of total numbers. Mean larval abundance (no. 100 m?3 ± SE) along the coast ranged from 5.0 ± 1.0 to 414 ± 226, with highest densities occurring on the northern sites of Watamu (414 ± 226) and Malindi (31 ± 10). Interannual variation in larval abundance between 2007 (2.17 ± 0.3) and 2008 (2.16 ± 0.1) was not significant (p > 0.05). Shannon-Wiener species diversities between sites ranged from 1.2 ± 0.4 to 2.3 ± 0.3, with highest diversities occurring in Mombasa (2.2 ± 0.5) and Nyali (2.3 ± 0.3). In 2007, the occurrence of preflexion larvae increased northwards from Mombasa (18.2%) to Watamu (86.4%), whereas in 2008, the reverse was the case with the incidence of preflexion larvae reducing northwards from Mombasa Marine Park (76%) to Watamu Marine Park (2%). These trends indicate interannual variation in larval source sites for fish species. Correspondence analysis revealed distinct larval assemblages at sites along the coast, which varied between years.  相似文献   

8.
Oxygen consumption rates (V?o2) in the grass shrimp Palaemonetes pugio were determined after a 32 day exposure to fluctuating temperatures (FT) (18–22°C) and/or dimethylnaphthalene (DMN)-contaminated food (0·24 μg DMN g wet wt?1) and again after a 16 day recovery period of stable temperatures (20°C) and uncontaminated food. Ingestion of DMN-contaminated food for 32 days resulted in elevated V?>o2 in shrimp exposed to declining oxygen concentrations. After the 32 day exposure period, FT had no significant effect on V?o2 at 15, 20 and 25°C, tissue V?o2 and V?o2 in declining oxygen. Hemolymph copper concentrations were significantly depressed in shrimp exposed to DMN-contaminated food. After the 16 day recovery period, shrimp from the FT regime exhibited depressed V?o2 when exposed to 25°C but not to 15°C. These depressed respiratory rates were offset by the stimulatory effect of DMN-contaminated food.These respiration studies were generally unproductive in explaining the previously reported effects of FT and DMN-contaminated food on the survival of P. pugio under hypoxic conditions.  相似文献   

9.
Experiments were conducted to test the effect of a range of chemicals on larval responses in swimming behaviour, attachment and metamorphosis of the black-footed abalone (Haliotis iris). The effect of antibiotics on larval survival was first tested within negative (filtered seawater) and positive (GABA at 10?5, 10?4 and 10?3 mol L?1) control assays over 3 days. This experiment corroborated the effectiveness of using antibiotics to improve survival of larvae without obvious synergistic interactions with the GABA inducer or confounding effects of potential bacterial interactions. Chemical treatments (acetylcholine, potassium chloride, dopamine and glutamine) were then tested at various concentrations for their ability to modulate swimming behaviour and induce larval attachment and metamorphosis over 14 days. Generally, larval state shifted from swimming to attached, and from attached to metamorphosed, in the control and treatments over time. However, the peak percentage of attached and metamorphosed larvae varied in time among chemicals and concentrations. While overall percent metamorphosis was minimally enhanced after 14 days of exposure to some chemical treatments at certain concentrations, all treatments displayed significant capacities to down-regulate larval swimming and induce early attachment and metamorphosis. Mortality was recorded throughout the duration of the experiment, and was generally low (<20%) across controls and most treatments for exposures of less than 12 days. Interpretations of specific results from this study are used to elucidate neurophysiological control of larval activities for this abalone species. Comparisons with other marine invertebrates highlight the specificities of chemical cues and endogenous regulatory mechanisms across relatively closely related taxa.  相似文献   

10.
The distribution patterns of saury eggs, larvae and early juveniles have been investigated over the continental shelf off the South-Western Cape from August 1977 to August 1978. Young saury tend to occupy water of 18°C or warmer in all seasons and are found offshore of the Benguela oceanic front when inshore upwelling is evident. Their distribution in the region appears to be linked to seasonal hydrography. Spawning in the study area occurs mainly between Cape Columbine and Cape Point, and to a lesser extent east of Cape Point. The ratio of large larvae and early juveniles to small larvae is greater off the West Coast than off the South Coast. Most spawning appears to take place in summer, with a peak abundance of larvae and early juveniles towards the end of this season. Instantaneous natural mortality was calculated: 5 – 30 mm, Z = 0,14·day?1; 30 – 100 mm, Z = 0,02·day?1. There is therefore a marked but unexplained decline in mortality shortly after the transition from the larval to the juvenile phase.  相似文献   

11.
Mytilopsis leucophaeata, an invasive bivalve species, causes fouling problems by settling on submerged constructions and in cooling water circuits in brackish water. To predict spat fall we studied the larval occurrence and settlement of this species in the brackish Noordzeekanaal canal in the Netherlands for several years (1989–1992), while measuring water temperature, salinity and chlorophyll a levels. Larvae were collected monthly by means of a plankton net drawn across the whole width of the canal. Settled spat were collected from PVC panels exposed for one month. Larvae first appeared in May or June, and reached maximum numbers in June or July, before disappearing in October, November or even December. The larval period started at a water temperature of 14 °C, reached maximum numbers at 19–23 °C and ended when it fell below 9 °C. No larvae were observed anymore until the temperature rose to 14 °C in the spring of the next year. Spat fall (June–November) was related to the water temperature in April. If the water temperature in April was lower than 12.5 °C, spat fall started in July, while if temperature was already higher in April, it started a month earlier. The spat fall period started at 15 °C, with maximum numbers at 20–24 °C, and ended when the water temperature dropped below 5 °C. Redundancy analysis (RDA) demonstrated a strong relationship between larval and spat densities and water temperature.  相似文献   

12.
L-DOPA对西施舌眼点幼虫附着变态诱导的研究   总被引：2，自引：0，他引：2  
采用试验水体中添加化学诱导物的方法研究L-DOPA(L-多巴)对西施舌(Coelomctraantiquata)眼点幼虫附着变态的诱导作用。结果表明,L-DOPA能诱导西施舌眼点幼虫变态,但对其附着的诱导效果不明显。用直径小于1 mm的细沙为附着基质,1×10-6mol/L的L-DOPA处理西施舌眼点幼虫12 h,变态率为73.3%,对照组为62.6%。浓度为1×10-7mol/L的L-DOPA处理西施舌幼虫12 h,生长速率为25.6%,对照组为14.7%,表明适当浓度的L-DOPA能促进西施舌幼虫的生长。在无沙附着的条件下,西施舌幼虫可正常附着变态,但生长速率较低且变态后死亡率高。  相似文献   

13.
The stability constants K1 and K12 of phosphoric acid were determined for artificial seawater of six different salinities (5, 10, 20, 30, 35, 40‰) and in 0.2, 0.4 and 0.7 M NaCl at three temperatures (5, 15, 25°C). The results are compared with those of Kester and Pytkowicz (1967), Atlas et al. (1976) and Dickson and Riley (1979). The ionic product of water, Kw, was determined in sodium chloride media at 5, 15 and 25°C. Complex formation among Ca2+, Mg2+, HPO42? and PO43? is discussed.  相似文献   

14.
Factors affecting the development of the embryos and production of larvae of the spiny lobster Sagmariasus verreauxi were investigated. Mature lobsters were collected from the fishery in New Zealand and held in captivity until they moulted, mated, and extruded eggs. For females, moulting took place in winter (July/August) and mating occurred 58–88 days later in early spring. The ovigerous females were then held at three temperatures and embryo development monitored at approximately weekly intervals. Mean times to hatch were 55, 75, and 130 days at 20°C, 17°C, and 13°C respectively. The total number of larvae that hatched from each female ranged from 0.97 to 1.4 million. The theoretical temperature at which embryo development ceases (a biological zero) for S. verreauxi, of 9.4°C, was calculated from data on the appearance of the median eye, the eyes and the chromatophores, and the time to hatch. An eye index formula was also derived to allow prediction of time to hatch at a range of temperatures using the cumulative difference between the rearing temperature and the biological zero. First instar phyllosomas from embryos reared at 20°C were significantly smaller than those from 17°C and 13°C but there was no significant difference in fitness. This study shows that hatching can be spread over a number of months, without significantly affecting larval quality, simply by manipulating holding temperature.  相似文献   

15.
Sea-spawned saury eggs collected 20 km off the west coast of the Cape Peninsula were hatched in laboratory tanks and the larvae reared. The larvae were fed initially on nauplii of cultured copepods, Tisbe holothuriae Humes and Pseudodiaptomus hessei (Mrázek). Growth rate during the first 47 days post-hatch averaged 0,62 mm·day?1 (at 18—19°C) and between the 47th and 120th day averaged 0,45 mm·day?1 (at 14,8—15,5°C). Some observations on feeding behaviour are included.  相似文献   

16.
Hydration, ion-water interactions, and water structure effects in seawater were studied by determining differences (Δβ) between the compressibilities of test salt solutions and the compressibilities of reference solutions. The reference solutions were distilled water and seawater (35%0), and the test salt solutions were either 0.13 m or 0.26m with respect to one of the following test salts: LiCl, NaCl, KCl, CsCl, NaF, NaI, MgCl2, CaCl2, BaCl2, Na2SO4, K2SO4, and MgSO4. The compressibility measurements (to 900 bars) were carried out at 2°C and also at 15°C using a differential method in which a pressure increase or a temperature increase causes Δβ to become less negative. At 1 bar and 15°C, the Δβ (0.26 m, distilled water reference) values ranged from ?1.14 × 10?6 bar? for NaI to ?3.84 × 10?6 bar?1 for Na2SO4, and the Δβ (0.26 m, seawater reference) values ranged from ?1.30 × 10?6 bar?1 for NaCl to ?3.04 × 10?6 bar?1 for Na2SO4. The Δβ values were used to calculate hydration numbers. Entropy of transfer, excess hydrogen bond breaking (determined by NMR), and effective radii of ions are properties which can be used to describe the influence of ions on water structure. The extent to which these properties correlate with Δβ values depends upon whether the ion is an anion or a cation, and this correlation forms the thesis that anions alter water structure in a different way than do cations.  相似文献   

17.
We measured the ammonium excretion, phosphate excretion and respiration rates of the scyphomedusa Aurelia aurita from Ondo Strait, in the central part of the Inland Sea of Japan, at 28 and 20°C. The rates measured at 28°C were converted to those at 20°C using the Q10 values, i.e. 1.56, 1.57 and 2.80, for ammonium excretion, phosphate excretion and respiration rates, respectively. The composite relationships between metabolic rates and wet weight of a medusa (WW, g, range 11–1330 g) at 20°C were expressed by the following allometric equations. For ammonium excretion rate (N, μmoles N medusa−1d−1): N = 0.497WW 1.09, phosphate excretion rate (P, μmoles P medusa−1d−1): P = 0.453WW 0.84, and respiration rate (R, μmoles O2 medusa−1d−1): R = 96.9WW 1.06. Mean O:N ratios (i.e. atomic ratios of 16.9 and 11.0 at 28 and 20°C, respectively) indicated that the metabolism of A. aurita medusae was protein-dominated. These metabolic parameters enabled us to estimate the nitrogen and phosphorus regeneration rates of an A. aurita medusa population typical of early summer in the Ondo Strait (means of water temperature, medusa individual weight and population biomass: 20°C, 200 g WW and 50.8 g WW m−3, respectively). Regenerated nitrogen and phosphorus were equivalent to 10.0 and 21.6% of phytoplankton uptake rates, respectively, nearly twice that estimated for mesozooplankton, demonstrating that A. aurita medusae are key components of the plankton community, influencing the trophic and nutrient dynamics in the Ondo Strait during early summer.  相似文献   

18.
Feeding periodicity, consumption rate, absorption efficiency, respiration rate and ammonia excretion were measured as functions of wet body mass in abalone collected from the western and southern Cape coasts. A well developed diel feeding rhythm was evident, consumption being restricted to the period 16h00–08h00. Food intake averaged 8,1 per cent of wet flesh mass·d?1 at 14°C and 11,4 percent at 19°C. The daily consumption rate was related to body mass by the relationships C(g) = 0,54 W(g)0,67 at 14°C and C(g) = 0,35 W(g)0,77 at 19°C. Absorption efficiency averaged 37 per cent and was independent of body size. Equations relating respiration rate to wet body mass were R(m? O2·h?1) = 0,03 W(g)0,83 at 14°C and R = 0,03 W(g)0,94 at 19°C. No significant differences were detected between day and night rates or between fed and starved individuals. The rate of ammonia excretion (μmole·h?1) was related to wet body mass (g) by the equations U = 0,22 W0,43 at 14°C and U = 0,03 W0,85 at 19°C.  相似文献   

19.
Rates of respiration and ammonia excretion of Euphausia hanseni and Nematoscelis megalops were determined experimentally at four temperatures representative of conditions encountered by these euphausiid species in the northern Benguela upwelling environment. The respiration rate increased from 7.7 µmol O2 h?1 gww ?1 at 5 °C to 18.1 µmol O2 h?1 gww ?1 at 20 °C in E. hanseni and from 7.0 µmol O2 h?1 gww ?1 (5 °C) to 23.4 µmol O2 h?1 gww ?1 (20 °C) in N. megalops. The impact of temperature on oxygen uptake of the two species differed significantly. Nematoscelis megalops showed thermal adaptations to temperatures between 5 °C and 10 °C (Q10 = 1.9) and metabolic constraint was evident at higher temperatures (Q10 = 2.6). In contrast, E. hanseni showed adaptations to temperatures of 10–20 °C (Q10 = 1.5) and experienced metabolic depression below 10 °C (Q10 = 2.6). Proteins were predominantly metabolised by E. hanseni in contrast to lipids by N. megalops. Carbon demand of N. megalops between 5 and 15 °C was lower than in E. hanseni versus equal food requirements at 20 °C. It is concluded that the two species display different physiological adaptations, based on their respective temperature adaptations, which are mirrored in their differential vertical positioning in the water column.  相似文献   

20.
Larvae of the decapod Crangon uritai were reared in the laboratory in a factorial experiment employing three temperatures (9, 12 and 15 °C) and three salinities (29‰, 32‰ and 35‰) from hatching to the post‐larval stage. The effects of temperature and salinity on survival, intermolt period (IP) and molt increment (MI) were investigated. Larvae from one brood were subdivided into groups of 20 and reared in glass bowls containing filtered sea‐water at a number of temperature–salinity combinations. The reared larvae were transferred daily to the clean bowls prepared with newly hatched Artemianauplii, and number of molts and mortality within each bowl were recorded. The zoeal size (carapace length) was determined from exuvia and dead larvae, and the IP was also recorded. Larvae of C. uritai completed larval development only at 15 °C temperature. The first zoeal stage completed their development at all temperature–salinity combinations and exhibited the highest survival rate. IP at each stage increased with increasing size and greatly decreased with increasing temperature, and intermolt duration (range of days) increased with larval development especially at the lower temperature. Although the MI decreased with increasing size, it was little affected by temperature. This led to a better growth rate with increasing temperature.  相似文献   

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