Macrofaunal involvement in the sublittoral decay of kelp debris: The sea urchin Psammechinus miliaris (Gmelin) (Echinodermata: Echinoidea)     

A.P. Bedford  P.G. Moore 《Estuarine, Coastal and Shelf Science》1985,20(1):19-40

Psammechinus miliaris occurs in the Clyde Sea area in large numbers (<18 individuals per 100 g^?1 weed dry wt) on sublittoral beds of detached Laminaria saccharina. Its rôle in weed decomposition has been examined by comparing its responses (behavioural choice, growth rate, absorption efficiencies of both carbon and protein, gut retention times and rate of faecal output) to fresh and rotting weed.Younger urchins grew faster than older individuals on a diet of rotting weed but not on fresh weed. Large seasonal variation existed, however, with fast growth occurring in June–August and little, or no, growth in December–February, irrespective of diet. Starved controls did not grow. Correcting for seasonality, rotting kelp still promoted faster growth of young urchins than did fresh weed. Larger (older) individuals showed no difference. Urchins fed fresh weed had significantly longer gut retention times. Protein absorption efficiency was higher on fresh than rotting weed, varying with weed protein content and size of urchin. Very young individuals can only digest high protein weed efficiently, eg. material derived from near the frond meristem. Organic carbon content of rotting weed was significantly lower than fresh weed. Carbon absorption efficiencies were significantly higher on fresh weed which related to organic carbon content. Standard-sized urchins fed rotting weed produced larger dry weights of faeces per day, reflecting increased ingestion rate. In closed-system choice experiments urchins preferred rotting weed kinetically. Size-frequency analysis of field populations suggested that weed beds are principally colonized by larval settlement from the plankton.Mature Psammechinus have evolved different ‘strategies’ for exploiting fresh and rotting weed. Fresh weed is relatively difficult to digest and long gut retention times allow high protein absorption efficiencies to be attained. Rotting weed has microbial protein in quantities and a lower organic carbon fraction. Some bacterial protein is seemingly unavailable though and lower protein absorption efficiencies result. Thus gut retention time is shortened and more food passed through the gut. Growth remains equivalent. Substratum digestion is of paramount importance for Psammechinus feeding on either fresh or rotting weed, cf. the ‘classical’ microbe-stripping detritivore of Fenchel.  相似文献   

CHANGE AND DEVELOPMENT IN RURAL MELANESIA     

R. D. Bedford 《New Zealand geographer》1974,30(2):204-204

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Influence of industrial activity and pollution on the paleoclimate reconstruction from a eutrophic lake in lowland England,UK     

B. Lang  A. S. Medeiros  A. Worsley  A. Bedford  S. J. Brooks 《Journal of Paleolimnology》2018,59(4):397-410

Reliable estimates of Holocene temperatures are important for understanding past climate dynamics, the response of biota to climate change, and validating climate models. Chironomids in lake sediment cores are used widely to quantify past summer temperatures, for which high-latitude and/or high-altitude lakes, remote from human influence, are usually considered appropriate. Temperature inferences from lowland lakes are likely influenced by other variables, specifically eutrophication and industrial pollution, but their reliability has never been tested. We used a Norwegian chironomid-based transfer function (r ² = 0.91; RMSEP = 1.01 °C) to infer mean July air temperature over the last 200 years, using chironomid assemblages in a core collected from a polluted, nutrient-enriched lake at Speke Hall, Liverpool, England. The chironomid-inferred temperatures correlate significantly with the local instrumental temperature record and follow long-term national temperature trends. These results show that chironomids can be used to produce reliable estimates of past mean July air temperature, even when other variables have also influenced the composition of the chironomid community. These findings underline the value of chironomids as sensitive and reliable quantitative proxies for summer temperature.  相似文献   

New discoveries of the Vedde Ash in southern Sweden and Scotland     

STEFAN WASTEGÅRD  CHRIS S. M. TURNEY  J. JOHN LOWE  STEPHEN J. ROBERTS 《Boreas: An International Journal of Quaternary Research》2000,29(1):72-78

The Vedde Ash (c. 10 300 ¹⁴ C BP) provides a key time-parallel marker horizon within the Younger Dryas chronozone or GS-1 event of the GRIP stratigraphy. Until recently, the known distribution of wind-blown Vedde Ash outside Iceland was restricted to the west coast of Norway, off-shore sequences close to the Outer Hebrides and the Greenland summit GRIP ice core. The first discoveries of the Vedde Ash in Scotland were reported in 1997, following the development of a new technique for extracting rhyolitic micro-tephra particles from minerogenic deposits. Here we report on the discovery of the Vedde Ash at additional sites in Scotland and at sites in southern Sweden. The concentration of tephra particles in sediments is highest in sites in western Norway, but is also relatively high in sites in southwestern Sweden, suggesting that the main ash cloud travelled eastwards from its volcanic source of Katla, in southern Iceland. Electron microprobe analyses do not indicate any clear geochemical evolution within the samples reported here.  相似文献   

The Quiet Revolution: Transformations in Migration Policies, Flows and Outcomes, 1999–2004     

Richard Bedford 《New Zealand geographer》2004,60(2):58-62

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Celebrating Geography: Home and Away     

Richard Bedford 《New Zealand geographer》2001,57(1):1-2

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Lasco Observations of Disconnected Magnetic Structures Out to Beyond 28 Solar Radii During Coronal Mass Ejections     

G. M. Simnett  S. J. Tappin  S. P. Plunkett  D. K. Bedford  C. J. Eyles  O. C. St. Cyr  R. A. Howard  G. E. Brueckner  D. J. Michels  J. D. Moses  D. Socker  K. P. Dere  C. M. Korendyke  S. E. Paswaters  D. Wang  R. Schwenn  P. Lamy  A. Llebaria  M. V. Bout 《Solar physics》1997,175(2):685-698

Two coronal mass ejections have been well observed by the LASCO coronagraphs to move out into the interplanetary medium as disconnected plasmoids. The first, on July 28, 1996, left the Sun above the west limb around 18:00 UT. As it moved out, a bright V-shaped structure was visible in the C2 coronagraph which moved into the field-of-view of C3 and could be observed out to beyond 28 solar radii. The derived average velocity in the plane of the sky was 110 ± 5 km s^-1 out to 5 solar radii, and above 15 solar radii the velocity was 269 ± 10 km s^-1. Thus there is evidence of some acceleration around 6 solar radii. The second event occurred on November 5, 1996 and left the west limb around 04:00 UT. The event had an average velocity in the plane of the sky of ∼54 km s^-1 below 4 R⊙, and it accelerated rapidly around 5 R⊙ up to 310 ± 10 km s^-1. In both events the rising plasmoid is connected back to the Sun by a straight, bright ray, which is probably a signature of a neutral sheet. In the November event there is evidence for multiple plasmoid ejections. The acceleration of the plasmoids around a projected altitude of 5 solar radii is probably a manifestation of the source surface of the solar wind. Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1004994214697  相似文献   

Use of probiotic bacteria to improve growth and survivability of farmed New Zealand abalone (Haliotis iris)     

JA Hadi  AC Alfaro  RD Roberts 《新西兰海洋与淡水研究杂志》2014,48(3):405-415

The effects of two probiotic feeds containing two and three bacterial isolates were evaluated on the growth performance of New Zealand abalone (Haliotis iris). Probiotic bacteria were isolated from the guts of healthy adult abalone. The isolates were screened qualitatively and quantitatively according to their ability to hydrolyse nutrients (i.e. proteins, starch and alginate), produce acid and resist bile salts. Based on the screening results, we developed a multi-strain conglomerate of 2- and 3- probiotic bacterial strains that were supplemented into a commercial abalone feed to use in our experiments. The 2-probiotic conglomerate consisted of Exiguobacterium JHEb1 and Vibrio JH1, and the 3-probiotic conglomerate consisted of Exiguobacterium JHEb1, Vibrio JH1 and Enterococcus JHLDc. The probiotic feeding trial involved abalone juveniles (20–30 mm in maximum shell length). Both probiotic feeds significantly improved abalone growth compared to that of the unsupplemented feed. The 3-probiotic supplemented feed produced a significant shell length increase of 20.9%, a wet weight gain of 19.8% and a five-fold reduction in mortality compared to the controls. The 2-probiotic supplemented feed resulted in significant increases in shell length (15.4%) and reduced mortality (five-fold), but not in weight gain, compared to controls.  相似文献   

Novel and toxin-producing epiphytic dinoflagellates isolated from sub-tropical Raoul Island,Kermadec Islands group     

L Rhodes  K Smith  T Harwood  C Bedford 《新西兰海洋与淡水研究杂志》2013,47(4):594-599

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Lateglacial cryptotephra detected within clay varves in Östergötland,south‐east Sweden          下载免费PDF全文

A. MACLEOD  L. BRUNNBERG  S. WASTEGÅRD  T. HANG  I. P. MATTHEWS 《第四纪科学杂志》2014,29(7):605-609

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