Search

This report .surnmarize the current knowledge about the phytoplankton ecology in the northern Barents Sea. The physical oceanographical and meteorological conditions are found to exert a strong control on the development of phytoplankton through the different seasons. Specially important is the formation of a stratified upper layer during spring as a condition for the development of the spring bloom is dominated mainly by two species, the diatom Chaetoceros socialis and the Phaeocystis pouchetii.The spring bloom make up to about 60% of the yearly primary production estimated to be about 90 gC m 2 year-1. The fate of the primary production seems to be strongly dependent on the prevailing climatic conditions, specially at the ice edge. During warm years most of fhe primary production ends in the pelagic foodweb. During cold years an important part of the primary production sinks out of the euphotic zone and ends either in a mesopelagic or a benthic foodweb. Based on the pattern of development of phytoplankton, four distinct biological regions are identfied in the northern B arents Sea: the Atlantic water in the central part, the Atlantic water in the eastern part, the ice edge zone and the Svalbarci bank. The report gives also a short overview over the effects of oil on phytoplankton. The spring bloom at the ice edge is identified as the most exposed process to an eventual oilspill.NORSK SAMMENDRAG:Rapporten summerer opp eksisterende informasjon om planteplanktonets økologien i det nordlige Barentshavet. Fysisk oseanografiske og meteorologiske forhold i sterk grad kontrollerer dynamikken i planteplanktonets utvikling gjennom de forskjellige sesonger. Særlig viktig i denne sammenheng er dannelsen av et stabilt overflatelag om våren som betingelse for utviklingen av våroppblomstringen. Denne er hovedsakelig dominert av to forskjellige arter, diatorneen Chaetoceros socialis og pryinriesiofyten Phaeocystis pouchetii . Våroppbloinstringen utgjør omtrent 60% av den årlige primærproduksjonen som anslåes til å være ca 90 gC m-2 år-1 . Primæiproduksjoness skjebne ser ut til å væse sterk avhengig av de klimatiske forhold, særlig ved iskanten. I varmere år går mesteparten av primærproduksjonen videre i det pelagiske næringsilettet. I kaldere år synker ei1 stor andel av produksjoilen ut av den eufotiske sonen og ned i vannsølen og gir grunnlag til enten et mesopelagisk eller et benthisk næringsnett. Basert på utviklingen av planteplanktonet, fire biologiske regioner i det nordlige Barentshavet blir identifisert : Atlanterhavsvann i de sentrale deler, Atlanterhavsvann i de østlige deler, iskantsonen og Svalbardbanken. Rapporten gir også en kort oversikt over effekter av olje på planteplanktonet. Våroppblomstringen ved iskanten betraktes som den mest utsatte prosses i tilfelle et oljespill.

Since 1987 the major part of the adult Norwegian spring spawning herring stock has been wintering in the Ofotfjord and the Tysfjord, two tributaries to the Vestfjord in northern Norway. The herring enter the fjords in August-September, and leave again in January, to start their spawning migration. The Institute of Marine Research has had regular surveys in the area in November each year since 1975, in which the herring population present has been measured acoustically. Since 1976 environmental parameters have also been recorded, including temperature, salinity, and oxygen and nitrate concentrations. This time series shows a gradual decrease in oxygen concentration in the Ofotfjord since 1987, when the herring started wintering in the fjord. High concentrations of herring are found in areas with oxygen concentrations as low as 1-2 ml1^-1. This paper presents and discusses the available data.

Faced with large variations in iodine, T4 or T3 supply, the fetal brain is able to maintain T3 homeostasis to a greater degree than apparent from changes in plasma and other tissues, such as the liver. Changes in the activity of 5'D-II play an important role in this homeostasis, although this does not exclude other regulatory mechanism(s), such as changes in type III (5D) activity, in uptake of the iodothyronines by the brain, or in cerebral iodothyronine turnover rates. T3 generated locally from T4 is more important than plasma derived T3 as determinant of the total T3 available to the brain throughout the life cycle of the rat. It is especially important during the fetal and neonatal phases of brain development, when the brain depends almost exclusively on the supply of T4. Fetal brain T3 homeostasis is maintained despite large fluctuations in the supply of T4. An excess of T3 also affects brain T3 to a lesser degree than it does other tissues. If present results are relevant to man, they suggest that overtreatment of mother of a congenital hypothyroid fetus with T4 is not likely to be harmful for the fetal brain. Treatment with T3 should be avoided, as it deprives the fetal brain of the main regulatory mechanism involved in homeostasis of brain T3, namely generation of T3 from T4.

Se analizaron 1182 estómagos de bacalao capturados durante el mes de julio de 1989 en Flemish Cap (Div. 3M de la NAFO). Fueron estudiados los tipos de presa, los índices de ocurrencia y de diversidad, así como varios índices cuantitativos, todos ellos por clases de edad. Se prestó especial atención a la predación del bacalao sobre la gallineta. En la dieta de los bacalaos jóvenes, de 1 a 3 años, las presas más frecuentes fueron los Anfípodos (Hipéridos). La presencia de los peces en la dieta del bacalao se incrementa con la edad, siendo la presa más abundante los juveniles de la gallineta nórdica (Sebastes spp.). La predación sobre la gallineta nórdica fue intensa, alcanzando un 53.7% del peso de los contenidos estomacales en todo el rango de edades estudiado. Considerando juveniles de gallineta y bacalao como presas alternativas (Lilly, 1985), se puede explicar la baja tasa de canibalismo (0.01% estimada. La correlación entre las tallas del predador (bacalao) y las de la presa (gallineta nórdica) fue de r=0.69 (p, Cod feeding (Gadus morhua) in the Flemish Cap in Summer. 1182 cod stomachs collected in the Flemish Cap during July 1989 were studied. The feeding intensity was high and the cannibalism rate very low (0.01%). For each Cod age class the prey types, feed intensity, prey occurrence index and gravimetric index were determined. The Amphypoda (Hyperiidae) were the main food component of the juvenile cod. The importance of fish food in cod feeding grows with the size increasing. The most important fish prey was the juvenile redfish. The predation upon the juvenile redfish was high, up to the 53.7% in weight of the stomach contents. This year the active predation upon the redfish can explain the low rate of cannibalism. The correlation index between the predator size and prey size was 0.69. In 1988 and 1989 cannibalism was not important but the predation upon the redfish juveniles can be a source or redfish mortality which influence the year classes size.

In the second half of May 1991 a bloom of the flagellate Chrysochromulina leadbeateri (Prymnesiophyceae) in the Vestfjord and surrounding areas, North Norway, occassionated significant fish death in several fishfarms. The total losses were 742 tons of salmon with an estimated value of 3,5 million US dollar. A large monitoring and research program was carried out during the bloom in order to map the distribution of the algae and collect data that could lead to a better understanding of this unusual algae bloom. The Institute of Marine Research in Bergen, Norway, through its Department of the Marine Environment, arranged on the 18-19 of September 1991, a scientific working meeting in the city of Svolvær in order to gather all the knowledge obtained during the bloom . The aims of the meeting were to obtain a detailed description of the bloom and an updating of the biology of C.leadbeateri and its effects on farmed fish and the natural flora and fauna. Altogether 30 persons participated in the meeting that comprised 11 scientific presentations and a general discussion and summary. This proceedings presents some of the contributions to the meeting. NORSK SAMMENDRAG: I andre halvdel av mai 1991 førte en oppblomstring av flagellaten Chrysochromulina leadbeateri (Prymnesiophyceae) i Vestfjorden og tilstøtende områder til betydelig fiskedød i flere fiskeoppdrettsanlegg. Det totale tap ble 742 tonn oppdrettslaks til en verdi av ca. 22,5 millioner kroner. En betydelig overvåknings- og forskningsinnsats ble satt i gang for å kartlegge algeutbredelsen og skaffe data som kunne gi en bedre forståelse av denne uvanlige oppblomstringen. Havforskningsinstituttet, Senter for Marint Miljø, arrangerte den 18-19 september 1991 et faglig arbeidsseminar i Svolvær for å samle den kunnskapen som ble oppnådd under oppblomstringen. Hensikten med seminaret var å best mulig å kunne gi en detaljert beskrivelse av blomstringens forløp samt en ajourføring av C. leadbeateri biologi og dens effekter på oppdrettsfisk og den naturlige flora og fauna. I alt omkring 30 personer deltok i seminaret som bestod av presentasjonen av 11 faglige innlegg samt en generell diskusjon og oppsummering. Denne rapporten presenterer de fleste av de enkelte bidragene til seminaret. Vi vil gjerne takke Fiskeridepartementet, Norges Fiskeriforskningsråd, Direktoratet for Naturforvaltning, Miljøverndepartementet og HOV for deres økonomisk støtte til seminaret. Takk også til J. Erices for hans hjelp med figurene.

For years it has been generally accepted that the mammalian placenta is virtually impermeable to the natural iodothyronines, thyroxine (T4) and 3,5,3’ triiodothyronine (T3). Although some placental transfer might occur, it would be physiologically irrelevant, with the pituitary-thyroid system being already functional and autonomous before birth 1–3. In most babies with congenital hypothyroidism, prompt onset of treatment with thyroid hormones soon after birth prevents most manifestations of brain damage. From this observation, and the idea that no thyroid hormone had been available to the fetus with an impaired thyroid, the conclusion has been drawn that thyroid hormones are not necessary for normal human brain development until birth 3, 4.

Hydrography, currents, nutrients, water transparency, in situ chlorophyll fluorescence and primary production were studied during a cruise with R/V "G.O. Sars" to the west coast of Denmark, Skagerrak and Kattegat from 27. November to 6. December 1989. The Jutland Current (JC) was partly blocked during this period, probably because of an intensified inflow of water from the central and northern North Sea ( Northern Jutland Current, NJC). This suggests that the NJC can exert a substantial dynamic control of the outflow of nutrientrich water from the coastal areas of the southern North Sea.