Ecology of the euphausiidsThysanoessa raschi,T. inermis andMeganyctiphanes norvegica in Ísafjord-deep,northwest-Iceland

The seasonal abundance, distribution, maturity, growth and population dynamics of the euphausiidsThysanoessa raschi (M. Sars, 1864),T. inermis (Krøyer, 1846) andMeganyctiphanes norvegica (M. Sars, 1857) were studied in Ísafjord-deep, a fjord in northwest Iceland, from February 1987 to February 1988. Sampling was made at nine stations along the length of the fjord at approximately monthly intervals, along with hydrographic measurements and water sampling for nutrient analysis and measurements of chlorophylla concentrations. Spring warming of the water began in late May and maximum temperatures (8° to 10°C) were observed in late July–September. The phytoplankton spring-bloom started in early April, and the highest chlorophylla levels were measured in early May (7.0 mg m^–3). A small increase was observed in the chlorophylla content in August. The greatest abundance of juveniles and males and females of all three species was observed during January and February 1988, during which period the euphausiids were concentrated in the middle and inner parts of the fjord. Euphausiid eggs were first recorded in the plankton in mid-May, and the greatest abundance ofThysanoessa spp. larvae occurred at the end of May. Larvae ofM. norvegica were not observed in Ísafjord-deep, indicating that recruitment of this species was occurring from outside the fjord.T. raschi andT. inermis had a life span of just over 2 yr; the life span ofM. norvegica was more difficult to determine. Almost all femaleT. raschi were mature at the age of 1 yr, while mostT. inermis females appeared not to mature until 2 yr of age. Most males of both species took part in breeding at 1 yr of age. The maximum carapace length ofT. raschi andT. inermis was 8 to 9 and 9 to 10 mm, respectively. The largestM. norvegica had a carapace length of 9 to 10 mm. The spawning of the euphausiids in Ísafjord-deep appeared to be closely related to the phytoplankton spring bloom; water temperature appeared to have no influence on spawning.     

Feeding preferences of periwinkles among four species ofFucus

A widely accepted view of intertidal community organizatiton in the NW Atlantic proposes that fucoid vegetation is maintained by the actions of predators which remove species competitively superior toFucus species. Herbivory is an important component of these predatory interactions, but has been studied largely with reference to the interaction betweenF. vesiculosus andLittorina littorea. There are many species of fucoids and herbivorous invertebrates on the shores of the NW Atlantic and this paper reports field and laboratory experiments performed in 1987 (in or near Halifax, Canada) on the effects of grazing by three species ofLittorina on adults and juveniles of four species ofFucus. In laboratory experiments, portions ofFucus species were presented singly (no choice) or together (multiple choice) to single species ofLittorina. AdultF. distichus was grazed to only a small extent.F. evanescens andF. vesiculosus adult tissues were heavily grazed in most laboratory experiments.F. spiralis adults were heavily grazed in no choice experiments, but were grazed only slightly in multiple choice tests. When adult fucoid tissues were exposed to a mixed suite of grazers in the field, onlyF. vesiculosus was grazed heavily. Tests done on adult tissues showed clearly thatFucus species are highly variable in their vunerability to grazers. Moreover, we found variability among periwinkle species in grazing rates on adultFucus. We also found a great disparity in the feeding rates of different periwinkle species on juveniles ofFucus. Therefore, it is not possible to extrapolate from a single periwinkle species/single fucoid species interaction when attempting to identify vegetation structuring processes.     

Results of the UNDP (SF)/FAO Regional Fisheries Survey in West Africa. report No. 2. Preliminary note on dissolved oxygen in the Canary Current

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.     

建立我国生态环境标准体系的初步构想

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。     

Growth and moulting of Neomysis integer (Crustacea: Mysidacea)

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.     

Amino acid uptake and respiration by marine heterotrophs

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.