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661.
662.
O. H. Oren 《Marine Biology》1972,17(1):1-3
While examining historical data on dissolved oxygen in the Canary Current area and the Central Atlantic Ocean (areas of activity of the UNDP/FAO Regional Fisheries Survey in West Africa), a quite different pattern of distribution was found in the dissolved oxygen/water temperature relationship in two adjacent Marsden squares (MS)1, 074 and 038. Not only were the dissolved oxygen values in MS 038 considerably lower than in MS 074 but, in the former square, the oxgen/temperature distribution showed 2 dissolved oxygen minima, the latter only 1 minimum. In MS 335, situated below the Equator, near the African coast, the oxygen/temperature distribution differs from the two former squares in that the dissolved oxygen value decreased steadily, and no oxygen minimum was found down to a depth where the water temperature was 6°C. 相似文献
663.
建立我国生态环境标准体系的初步构想 总被引:9,自引:0,他引:9
我国的生态环境标准极其薄弱,建立生态环境标准体系是我国生态环境保护的迫切需要。借鉴我国目前针对污染防治的环境标准体系,提出了我国生态环境标准体系的基本框架,以及生态环境标准制订的原则和重点。 相似文献
664.
Growth and moulting of Neomysis integer (Crustacea: Mysidacea) 总被引:1,自引:0,他引:1
The growth and moulting of Neomysis integer (Leach) was investigated in the field and the laboratory. In the Ythan estuary, Aberdeenshire, Scotland, monthly samples taken from November 1976 to October 1978 revealed that the summer generation juveniles and mature individuals grew at a rate of 4 to 5 mm and 1 to 2 mm monthly, respectively. The winter generation had a growth rate of 3 to 4 mm monthly for juveniles and about 1 mm for mature individuals; during the winter there was a period of 3 mo when growth was almost completely stopped. Mysids reared in the laboratory on Artemia sp. nauplii had an average daily growth rate of 0.06 mm at 9°C and 0.09 mm at 16°C. The growth factors of N. integer ranged from 3 to 17% for mature and immature individuals, respectively. Intermoult periods ranged from 3 to 7 d in immature mysids to 12 to 18 d in mature mysids. Average laboratory growth curves calculated from information on growth factors and intermoult periods indicate that at 9°C (winter generation) it takes N. integer 277 d to grow to be a 15 mm mature individual, whereas at 16°C (summer generation) it takes 188 d. N. integer moults 24 times as it grows from a juvenile to a mature individual. 相似文献
665.
Amino acid uptake and respiration by marine heterotrophs 总被引:5,自引:0,他引:5
The concentration and turnover of dissolved free amino acids were measured in samples from 25 and 100 m on three occasions at a station 6 miles off the California (USA) coast. Individual amino acid concentrations varied from undetectable (<0.05 g/l) to 3 g/l, the total amino acid concentration from 1.8 to 8.5 g/l. The greater concentration of total amino acids was always found at 25 m. The predominant amino acids were serine, lysine, aspartate, glutamate and alanine; reliable analyses could not be made for glycine because of a high blank. For the 10 individual amino acids studied, the rate of heterotrophic turnover ranged from undetectable to 1.2 g/l day-1; serine, aspartate, alanine and glutamate showed the highest rates. In samples from 25 m, the rates were 15 to 20 times higher than those taken from 100 m. The total calculated flux of the amino acids studied varied from 0.015 to 3.2 g/l day-1 and amounted to 1–10% of photosynthetic carbon dioxide fixation. 相似文献
666.
Structural organisation,transfer and biological fate of endosymbiotic bacteria in gutless oligochaetes 总被引:1,自引:0,他引:1
From differences in size and structure, it appears there are two species of gram-negative bacteria in the gutless oligochaetes Phallodrilus leukodermatus and P. planus from Bermuda. A non-random, differentiated and consisten distribution pattern of the extracellular bacteria along the length of the worm's body underlines the regulated nature of the bacterial colonization. This emerges also from studies on the transfer of the bacteria between host generations: exceptional for oligochaetes, eggs are deposited singly in a sticky mucus sheath and not together in a cocoon. They become infected immediately at oviposition, apparently by intrusion from large stores of bacteria in a genital pad abutting the female pores. During ontogenesis, a balance is established between extracellular, active bacteria and intracellular lytic forms enclosed in vacuoles by the epidermal cells. In early developmental stages, lytic bacteria prevail, but older worms harbour mainly extracellular prokaryotes underneath their cuticle. The thick epidermis/cuticle complex is differentiated in regular zones with a progressive trend towards enclosing and digesting bacteria intracellularly in the deeper layers. These are the first results on the transfer and biological fate of endosymbiotic bacteria living in animals from sulfide biotopes. 相似文献
667.
Lithophaga date mussels from three species (L. lessepsiana, L. simplex and L. purpurea) were removed from their stony coral hosts in the Red sea at Eilat, Israel. Spawning, observed in the laboratory on several occasions during 1987–1988, appeared to be closely tied to lunar periods, occurring primarily during the last quarter and the new moon. Embryonic and larval development was typical of that described for other mytilids and, except for pigmentation differences, which could be discerned during embryogenesis, the developmental stages of the three species were indistinguishable. Development to the pediveliger stage took 3 to 4 wk in standard culture conditions, but raising the temperature to 27.5 °C increased the growth rate of larvae of L. lessepsiana by as much as three-fold, so that the pediveliger stage was attained in 16 d. Larvae resulting from spawning by L. simplex adults removed from the coral Astreopora myriophthalma grew significantly faster in culture than larvac from adults removed from the coral Goniastrea pectinata (comparison of slopes, p<0.05). The latter individuals showed a 6-d growth plateau at the early umbone stage. Metamorphically competent larvae were capable of delaying metamorphosis for up to 4mo, which would allow an extended period for dispersion and would increase the chance of finding a suitable substratum in the natural environment. 相似文献
668.
The importance of species interactions and recruitment variability was examined during the first year and a half of primary succession (1988–1989) on an exposed rocky seashore near Halifax, Nova Scotia. Previous work suggested that emergent rock on these shores is normally dominated by fucoid rockweeds because predatory whelks control the sessile animal competitors, mussels and barnacles, and because herbivorous littorinids control ephemeral algal competitors. Abundances of all species except seasonal ephemeral algae were very small throughout this experiment and we found no significant effects of carnivory, herbivory, plant-animal competition or plant-plant competition. A slight facilitation of Fucus recruitment is attributed to a thin mat of ephemeral, blue-green algae. Very few other studies have directly manipulated intertidal ephemeral algae. As primary succession may be very rare in this assemblage, these results may be specific to these circumstances, but they highlight the varying importance of species interactions with variable recruitment. In particular, it appears that variations in recruitment success may be important to community structure, even when recruitment is not limited by propagule supply. The scale of the study also provides insight into successional processes occurring after the recent, extensive ice-scour of exposed seashores in this region. 相似文献
669.
Oxygen consumption rates of the deep-sea fish Sebastolobus altivelis were measured in situ on pelagic juveniles at mesopelagic depths (608 m) and on demersal adults at bathyal depths (1 300 m) in the Santa Catalina Basin in March 1982. Two pelagic juveniles were individually collected, and respiration was measured continuously for approximately 2 d with a slurp gun respirometer manipulated from the submersible “Alvin”. Oxygen consumption rates of these juveniles were highly variable and were 1.5 to 1.8 times higher during the night than during the day. Gut contents of the juveniles were mainly euphausiids (Euphausia pacifica and Nematoscelis difficilis). Four demersal adults were collected by “Alvin” and individually placed in fish-trap respirometers on the bottom where respiration was measured continuously for approximately 1 d. Weight-specific O2 consumption rates for adults decreased with increasing body weight and were consistent in magnitude throughout the incubation period. Population O2 consumption for demersal S. altivelis (calculated from abundance, size-frequency distribution, and O2 consumption regression equation) was 11.01 μl O2 m-2 h-1, which is two orders of magnitude less than the O2 consumption rate for the population of the most abundant epibenthic megafaunal species in the Santa Catalina Basin, the ophiuroid Ophiophthalmus normani. O. normani is a principal prey for adults of S. altivelis based on gutcontent analysis. Given the population O2 consumption rate as an estimate of food energy demand, the demersal population of S. altivelis would assimilate only 0.007% of the standing crop of O. normani per day. 相似文献
670.
Stability of sea urchin dominated barren grounds following destructive grazing of kelp in St. Margaret's Bay,Eastern Canada 总被引:2,自引:0,他引:2
A. R. O. Chapman 《Marine Biology》1981,62(4):307-311
Kelp regeneration was observed for the first time in St. Margaret's Bay, Nova Scotia, Canada in an area known to have been devoid of macroalgae for several years. The regeneration was destroyed by sea urchins within 10 months. Experimentally induced kelp regeneration met a similar fate under normal grazing pressure. At the lowest sea urchin biomass and density encountered re-establishment of mature kelp stands seems highly unlikely. The sea urchin population required to suppress kelp regeneration is fed by benthic microalgae. Diatoms and other pioneer algal community species were found in the guts of sea urchins. The mean standing crop of benthic microalgae was found to be, 2.2 g C m-2 and production estimated as ca 15 g C m-2yr-1 at 8m depth. Most of the primary production of St. Margaret's Bay has been lost with the disappearing kelp populations. 相似文献