摘要:

The physiological behavior of various phytoplankton species has been examined under increasing and decreasing light regimes. A marked asymmetry has been found, with photosynthesis rates under rising light intensities exceeding those under dimming lights. Photoinhibition has been observed at moderate light intensities (0.4–1.0 ly/min). Variations in the asymmetry and in photoinhibition appear to be correlated with the light regimes experienced by the population. Under constant illumination by full sunlight a steady decrease in the photosynthesis rate was observed. As a result of photosynthesis measurements in fluctuating light regimes there is now evidence for photorespiration as the controlling mechanism. Data are presented which show that prolonged exposure to high light has an adverse effect on photosynthesis and indicate that14C moored bottle experiments may show reduced surface rates because of this.

ISSN:0706-652X    

DOI:10.1139/f73-286

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Photosynthesis measurements on net plankton have been carried out for the period April, 1972 to January, 1973 in Lake Ontario. The rising and falling light regimes used on the net phytoplankton (> 64 μ) give marked photosynthetic hysteresis effects in winter and in spring for diatom-dominated populations. Diel fluctuations in photosynthesis and "sun" or "shade" adaptations showed a close interaction between the phytoplankton and the surface light intensity. Systematic seasonal changes have been recorded in the magnitude of the photosynthetic hysteresis effect, saturation light intensities, compensation points, maximum photosynthesis, and respiration rates. An inverse correlation has been found between net plankton mean maximum photosynthesis rates and the rate of change of water temperature. Also phytoplankton respiration rate is largely a function of temperature.The data have been unified to give a picture of daily photosynthesis patterns at different depths in a static water column. The data compare well with14C moored bottle experiments. Predictive equations have been calculated for maximum photosynthesis rates at different times of the year.

ISSN:0706-652X    

DOI:10.1139/f73-287

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Crawling and respiration rates of the snailLittorina littoreaare increased in the presence of Bunker C oil and decreased with brief exposure to a low toxicity dispersant (Corexit 8666) in sea water at 20 C. The addition of the dispersant to an oil:seawater mixture also decreases both crawling and respiration. Behavioral traits, such as crawling, and physiological indices, such as respiration, may be sensitive measures of sublethal effects of pollutants on organisms.

ISSN:0706-652X    

DOI:10.1139/f73-288

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

A large number (2933) ofCaligus elongatus(Copepoda: Caligidae) removed from the buccal cavities of cod,Gadus morhua, off the west coast of Scotland, were examined for presence and distribution ofUdonella caligorum(Monogenea: Udonellidae). Distribution of worms was not consonant with space available for attachment. Eggs and young worms were found primarily on the posterior half of the copepod, whereas adults occupied predominantly the lateral margins of the cephalothoracic shield. It was concluded thatU.caligorumhas a feeding area and a nursery area on the copepod and carries out migrations between them. Location of the feeding area strongly suggests that the worm feeds directly on the epithelial tissues of the fish.

ISSN:0706-652X    

DOI:10.1139/f73-289

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Fingerling and adult sockeye salmon (Oncorhynchus nerka) were subjected to long periods of sustained swimming (10–20 days) in air-saturated fresh water. Energy expended was computed from change in body composition and compared with the metabolic equivalent from multiple determinations of oxygen-consumption rate. Caloric loss from body substance exceeded that estimated from total oxygen uptake by an average of 19.8%. The reasons for the difference, and the assumptions involved, are discussed. The difference apparently arises from slight excretion of partially metabolized fuels (anaerobic metabolism) and loss from sloughed body tissues. An oxycalorific equivalent of 4.8 kcal/liter O2is considered an acceptable value for fish.

ISSN:0706-652X    

DOI:10.1139/f73-290

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

The toxic effects of captan on survival, growth, and reproduction of fathead minnows (Pimephales promelas) and on survival of bluegills (Lepomis macrochirus) and brook trout (Salvelinus fontinalis) were determined in a flow-through system. In a 45-week exposure of fathead minnows, survival and growth were adversely affected at 39.5 μg/liter. Adverse effects on spawning were suspected but not statistically demonstrated at 39.5 and 16.5 μg/liter. The maximum acceptable toxicant concentration (MATC), based on survival and growth, lies between 39.5 and 16.5 μg/liter. The lethal threshold concentration (LTC) derived from acute exposures was 64 μg/liter, resulting in an application factor (MATC/LTC) between 0.26 and 0.62. LTC values for the bluegill and brook trout were 72 and 29 μg/liter, respectively. The estimated MATC is between 44.6 and 18.7 μg/liter for the bluegill and between 18.0 and 7.5 μg/liter for the brook trout.The half-life of captan in Lake Superior water with apH of 7.6 is about 7 hr at 12 C and about 1 hr at 25 C. Breakdown products from an initial 550 μg/liter of captan were not lethal to 3-month-old fathead minnows.

ISSN:0706-652X    

DOI:10.1139/f73-291

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Estimates of the abundance of the four planktonic stages of lobster larvae (Homarus americanus) taken in a large surface plankton net show that production and survival of larvae in Northumberland Strait in 1962 and 1963 were the lowest on record. Examination of diurnal fluctuations in abundance, and sampling below the surface and at various depths to the bottom, confirm that larvae are concentrated at the surface during daylight hours. The time to next molt of stage IV larvae, captured and retained alive, indicates that settlement takes place about midway through stage IV. Reexamination of earlier results together with these new data now suggests there is some evidence for a relationship between stage IV larval abundance and subsequent commercial lobster stocks, but that sampling errors are too great to permit accurate prediction.

ISSN:0706-652X    

DOI:10.1139/f73-292

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

Estimates were made of the increase in live and dry weights and in the content of ash, organic matter, carbohydrate (as glucose), and nitrogen when juveniles of the clamSaxidomus giganteuswere fed for 21 days at various concentrations ofTetraselmis chui,Isochrysis galbana, andPhaeodactylum tricornutum. The condition index (organic weight as a percent of total dry weight) increased in all the experimental conditions with a mixture ofI.galbanaandT.chui, yielding a significantly higher index than either species on its own. The relative gain in glucose was greater than the increase in live weight or in nitrogen. The increase in live weight was such that the nigrogen content was approximately constant at 6–7 μgN/mg live weight irrespective of the feeding conditions. The N:glucose ratio decreased with increasing concentrations ofI.galbanaandP.tricornutum, and at the higher concentrations, where the maximum growth rate of clams occurred, the ratios were lower than in any of the clams fed onT.chui.

ISSN:0706-652X    

DOI:10.1139/f73-293

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

EighteenBathyraja richardsoni(Garrick 1961), 95–174 cm in total length were taken by bottom longline from southern Labrador to Georges Bank, 17 at 1810–2360 m, and one at 1370–1500 m. These are the first records for the western Atlantic. Studies of morphometries, of numbers, of form, and arrangement of spines, dermal denticles, and teeth, and of body color in these skates amplify the description of the species, known previously only from New Zealand (the holotype) and the northeast Atlantic (eight specimens). There is, however, appreciable variation in the distribution and abundance of dermal denticles between the new specimens and the holotype. These specimens also have middorsal caudal spines instead of the middorsal caudal row of fleshy oval structures (some with a central tubercle of enamel) of the holotype, which are related in this paper to scar areas from lost spines.Some information is provided on weight–length, liver weight, and fatness, vitamin A of liver oil, and length at sexual maturity. Food was mainly fish.The trematodeOtodistomum veliporumoccurred in 5 of 16 stomachs and the cestodeOnchobothrium pseudouncinatumin 6 of 16 intestines. A copepod, tentatively identified asLernaeopodina longimana, was found on the gills of one of five specimens.

ISSN:0706-652X    

DOI:10.1139/f73-294

出版商:NRC Research Press    

年代:1973

数据来源: NRC

摘要:

At low oxygen tensions in sediment–water aquaria systems, concentrations of 3-trifiuoromethyl-4-nitrophenol (TFM) in the range 5–10 mg/liter were reduced to 3-trifluoromethyl-4-aminophenol (RTFM) in 5–20 days. This reduction resulted in loss of the characteristic yellow color of TFM as measured by the optical density at 395 nm. The reduced form was apparently stable, although inconclusive evidence suggested that some additional breakdown of RTFM may have occurred within 3 months under anoxic conditions. Under aerobic conditions, no significant degradation of TFM was observed for periods of up to 2.5 months. Sorption of TFM by sediments was observed to some extent and appeared to vary with the sediment source.

ISSN:0706-652X    

DOI:10.1139/f73-295

出版商:NRC Research Press    

年代:1973

数据来源: NRC