摘要:

South Maria Ridge (34°S) is a 1500 km2submarine ridge and bank system, less than 500 m deep, slowly accumulating photic and sub‐photic, clean skeletal carbonate gravels and sands having over 80%, and generally over 95%, CaCO3, mainly calcite. Contributing factors include the negligible supply of terrigenous sediment, the availability of stable rocky substrates for colonisation by epibenthos, and the prominent upwelling of nutrient‐rich waters, stimulating organic growth. Sediments comprise fragmental remains of diverse bryozoan colonies (10–74%), with lesser amounts of mainly infaunal bivalves (2–20%), gastropods (2–10%), ahermatypic corals (0–18%), calcareous red algae (1–16%), and benthic foraminifers (3–15%), and small contributions from serpulids, barnacles, echinoids, brachiopods, sponges, and pteropods. Major species are identified. The distribution of skeletal types is controlled initially by substrate, bathymetry, and energy level, and subsequently by topographically influenced tidal flow dispersal. However, the present sediment distribution pattern has been complicated by eustatic sea level changes. Modern zones of carbonate production are centred mainly on the shallower portions of the ridge, in the vicinity of Three Kings and Middlesex Banks. Below 150–200 m depth the skeletal sediments become increasingly relict. A rough bathymetric zonation of faunal types remains, but their depths are on average 100–150 m below their modern counterparts, supporting emplacement during the low sea level of the Last (Otiran) Glaciation. The skeletal deposits are temperate‐latitude limestones in the making, with properties significantly different from their better known tropical counterparts but closely analogous to many Cenozoic limestones in New Zealand.

ISSN:0028-8330    

DOI:10.1080/00288330.1984.9516044

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The in situ acetylene‐reducing (nitrogen‐fixing) activities within the sediments of 2 eutrophic lakes were examined to determine whether this process plays a significant role in enhancing nutrient enrichment of these lakes. Estimates of the N‐fixing potential on a sediment dry‐weight basis were 10.9–112.1 ng g‐1h‐1or on an area basis were 45.3–99 ng m‐2h‐1. The distribution of C2H2reducing activity within the sediment paralleled the distribution of Kjeldahl N, total organic carbon, and microbial biomass and was inversely related to NH+4—N in interstitial water. A seasonal variation in the activity was observed in the top most sediment strata, with the highest rates occurring during winter. Estimates of the total N input reveal that this is of little quantitative importance compared to inputs of combined N from other sources.

ISSN:0028-8330    

DOI:10.1080/00288330.1984.9516045

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Harmonic tidal constants, calculated from sea surface elevation observations at Jackson Bay on the West Coast of the South Island, are consistent with available semi‐diurnal and diurnal tidal phase distributions. Current observations taken over a 111 day period at mid‐depth in 1505 m of water on the southern flank of the Challenger Plateau and over a 240 day period in 1430 m of water on the South Island western coast continental slope, are subject to tidal analysis. At both sites there is a component of energy flux directed across the isobaths and only at the northern site for the M2tide is the phase consistent with a dominant progressive barotropic tide. The successive 30 day harmonic constants at the southern continental slope site exhibit a trend in the M2tidal ellipse speed and ellipticity suggesting the presence of a regular internal tide. Superposition of ‘internal tidal’ and barotropic tidal flows, as prescribed from progressive‐ and standing‐wave elevations, to fit the observations indicates that the ‘internal tide’ is probably associated with the first baroclinic mode. At the current‐meter depths the speeds of the ‘internal tide’ for the M2tide are about the same as the barotropic speeds, whereas, the S2‘internal tide’ speeds are larger than those of the barotropic tide. The consistency of the trend in ellipse parameters lends support to the theoretical progressive trapped barotropic tidal flows being a good approximation to the actual barotropic tide. Some support for the hypothesis that the S2tide on the West Coast of New Zealand has a substantial standing wave contribution is given by the northern observations, where the ratio of the S2: M2internal tidal ellipse current amplitudes are substantially larger than the ratio of the elevations, the internal tide being generated by across‐isobath flows.

ISSN:0028-8330    

DOI:10.1080/00288330.1984.9516046

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The freshwater calanoid copepodsBoeckella triarticulataandB. hamatawere found in ponds near Napier. These are the first records ofB. triarticulatain the North Island, New Zealand and ofB. hamatain the east coast, North Island.

ISSN:0028-8330    

DOI:10.1080/00288330.1984.9516047

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor