Search Results - (Author, Cooperation:C. Turley)

2015-07-04

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

Animals ; Aquaculture ; *Aquatic Organisms ; *Carbon Dioxide ; *Ecosystem ; *Global Warming ; *Greenhouse Effect ; Health ; Humans ; Oceans and Seas ; Risk ; Travel

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] Fig. 1 Position of the Liverpool Bay and western and southwestern Irish Sea fronts. Position of anchor station (A6) and station positions along reference line are indicated. The general hydrographic and chemical features of Liverpool Bay have been described by Foster et al.4. A discontinuity or ...

Electronic Resource

1476-4687

Nature Archives 1869 - 2009

Biology

Chemistry and Pharmacology

Medicine

Natural Sciences in General

Physics

[Auszug] The deposition of detrital material within a short period of time after the spring phytoplankton bloom4'5 represents a major nutrient input to the deep-sea community, provided its organic content can be readily used by the deep-sea biota. A close coupling of sedimentation and microbial breakdown of ...

Electronic Resource

1432-1793

Springer Online Journal Archives 1860-2000

Biology

Abstract During a 25 d Lagrangian study in May and June 1990 in the Northeast Atlantic Ocean, marine snow aggregates were collected using a novel water bottle, and the composition was determined microscopically. The aggregates contained a characteristic signature of a matrix of bacteria, cyanobacteria and autotrophic picoplankton with inter alia inclusions of the tintiniid Dictyocysta elegans and large pennate diatoms. The concentration of bacteria and cyanobacteria was much greater on the aggregates than when free-living by factors of 100 to 6000 and 3000 to 2 500 000, respectively, depending on depth. Various species of crustacean plankton and micronekton were collected, and the faecal pellets produced after capture were examined. These often contained the marine snow signature, indicating that these organisms had been consuming marine snow. In some cases, marine snow material appeared to dominate the diet. This implies a food-chain short cut wherby material, normally too small to be consumed by the mesozooplankton, and considered to constitute the diet of the microplankton can become part of the diet of organisms higher in the food-chain. The micronekton was dominated by the amphipod Themisto compressa, whose pellets also contained the marine snow signature. Shipboard incubation experiments with this species indicated that (1) it does consume marine snow, and (2) its gut-passage time is sufficiently long for material it has eaten in the upper water to be defecated at its day-time depth of several hundred meters. Plankton and micronekton were collected with nets to examine their vertical distribution and diel migration and to put into context the significance of the flux of material in the guts of migrants. “Gut flux” for the T. compressa population was calculated to be up to 2% of the flux measured simultaneously by drifting sediment traps and 〈5% when all migrants are considered. The in situ abundance and distribution of marine snow aggregates (〉0.6 mm) was examined photographically. A sharp concentration peak was usually encountered in the depth range 40 to 80 m which was not associated with peaks of in situ fluorescence or attenuation but was just below or at the base of the upper mixed layer. The feeding behaviour of zooplankton and nekton may influence these concentration gradients to a considerable extent, and hence affect the flux due to passive settling of marine snow aggregates.

Electronic Resource

1432-184X

Springer Online Journal Archives 1860-2000

Biology

Abstract Diel changes in the specific growth rates of natural bacterial communities as a whole and of different groups within the communities were followed over 2 days during July 1982, in stratified waters in the vicinity of a shallow sea tidal mixing front in the Irish Sea. Waters well above (4 m) and below (60 m) the thermocline were enclosed in dialysis bags and incubated in situ. The results show that there were periods of altered growth rates of the whole bacterial community and synchronous cell division of morphological groups. An increase in mean cell volume within both 4 and 60 m communities preceded an increase in specific growth rates, with a resultant decrease in the mean cell volume. Above the thermocline the whole bacterial community, as well as the rod and coccoid forms, doubled in number once a day. The doubling time of the whole bacterial community at 60 m was 2 days and slower than that at 4 m. This was due to a slower doubling time (3 days) for the coccoid forms. Rod forms at the two depths had a similar doubling time (1 day). The time of day when maximum division rate occurred was also different in the two water masses. At 4 m more coccoid forms divided during the night, whereas at 60 m more divided during the day. Conversely, at 4 m more rod forms divided during the day, whereas at 60 m more divided at night. These data indicate that the bacterial community and members of the community may be adapted to exploit the diurnal rhythms of dissolved organic carbon (DOC) release by other organisms and that portions of the bacterial community may therefore be more active at certain times of the day. The diurnal growth of the bacterial community may thus vary between different water masses and largely reflects the differences in the chemical and biological characteristics of the two water masses investigated.

Electronic Resource

1573-5117

bacteria numbers ; [3H]-thymidine incorporation ; deep sea ; surficial sediment ; phytodetritus ; northeast Atlantic

Springer Online Journal Archives 1860-2000

Biology

Abstract The effect of water depth on bacterial biomass and their ability to synthesise DNA, by measuring their rate of [3H]-thymidine incorporation, was investigated in the northeast Atlantic at three sites of varying water depth (1100–3580 m) and sediment characteristics. Thymidine incorporation rates (y) in surficial sediments varied between 0.028 and 1.44 pmol h−1 g−1 and showed an exponential relationship with depth (x) according to the equation y= 2.05e−0.0011x (r=0.9830 for n=7, P〈0.001). However, this relationship failed when a layer of phytodetritus was found overlying the surface sediment and [3H]-thymidine incorporation rates increased by 80–339%. In contrast, bacterial numbers varied between 1.09 and 11.96 × 108 cells g−1 (dry weight) and showed no significant relationships with water depth or sediment POC/TN content. Significant exponential relationships were also found between water depth (x) and the POC (y 1) and total nitrogen (TN, y 2) content of surficial sediments according to the following equations: where y 1 = 719e−0.0003x (r=0.8700 for n=9, P〈0.01) and y 2 = 76e−0.0002x(r=0.7582 for n=9 P〈0.02). These relationships were irrespective of the presence or absence of an overlying layer of phytodetritus. This suggests that the POC and TN content of these surficial deep sea sediments is directly related to the flux of material through the water column, which significantly impacts bacterial production.

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