摘要:

Development, settlement, and subsequent metamorphosis on several substrata were observed in cultures ofEvechinus chloroticuslarvae. The period from fertilisation to metamorphosis ranged between 30 and 63 days for larvae collected from spawnings induced at 3 different times. Newly settled sea urchins collected from the field grew about 1 mm per month in aquaria. Correlation of the larval life span with the growth rate of newly settled sea urchins suggested that the earliest spawning could occur was mid‐November. This finding corroborates the results of previous histo‐logical studies of the gonads of adult sea urchins in the Hauraki Gulf, New Zealand.

ISSN:0028-8330    

DOI:10.1080/00288330.1984.9516060

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Macrofaunal polychaete densities across a fine‐sand intertidal flat in Pauatahanui Inlet, North Island, New Zealand, were examined seasonally from a pair of adjacent transects. Density patterns had shore‐normal trends, despite weak tidal‐cycle environmental gradients. Abundances frequently corresponded between transects separated by 15 m.Capitellasp.,Nicon aestuariensis,andScolecolepides benhamideclined in density downshore, whereasHeteromastus filiformisincreased.Microspio maoriandAxiothella serratalacked strong trends.Boccardia acus’density was affected by the size and number of the bivalveChione stutchburyi,its substratum. Basic zonation patterns of each species persisted over a 2 year period. Within the density concentrations seasonal cycles were apparent, with some population redistribution attributable to differential mortality (H.filiformis),to recruitment (M. maori, A. serrata),or to migration (N. aestuariensis, S. benhami).

ISSN:0028-8330    

DOI:10.1080/00288330.1984.9516061

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Three species of mytilid bivalves(Mytilus edulis aoteanus, Perna canaliculus, Aula‐comya maoriana)co‐exist in the eulittoral zone of some rocky shores in New Zealand. However, their distributions within this zone show micro‐geographic differences. To determine the possible role of behaviour on these diiferences, separate experiments on the species’ abilities to crawl out from under gravel and to distribute themselves in mixed‐species clusters were performed. When small mussels (1–2 cm long) were covered with 3 cm of pea gravel (0.3–0.8 cm grain size),P. canaliculuscrawled to the surface much more rapidly than did the other 2 species, which were generally similar in crawl‐out ability. When numbers of small mussels (1–4 cm long) of the 3 species were mixed together in various combinations and held in sea water,A. maorianapredominated inside the resultant clusters, whereasP. canaliculuswas judged to be slightly more abundant thanM. e. aoteanuson the outside of such clusters.

ISSN:0028-8330    

DOI:10.1080/00288330.1984.9516062

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Gomphonema novo‐zelandicumsp. nov., the dominant epiphytic diatom onCarpophyllum maschalocarpumandC. flexuosum,growing in the sublittoral fringe zone in northern New Zealand, is described and its taxonomic status determined. This diatom, although present on other macroalgae from the same zone, is predominantly epiphytic on these 2 species ofCarpophyllum,maintaining substantial populations on them throughout the year.

ISSN:0028-8330    

DOI:10.1080/00288330.1984.9516063

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Lake Rotoiti, North Island, New Zealand, is a deep (maximum depth, 126 m) lake surrounded by a mostly forested and farmland catchment. However, it currently demonstrates several attributes characteristic of enriched waters. Algal production is high relative to other deep basin lakes of the central North Island. The hypolimnion deoxygenates completely each year, and a bloom‐forming species of blue‐green algae is numerically important in the summer phytoplankton. These features appear to be recent rather than longstanding properties of the Lake Rotoiti ecosystem. A detailed comparison of limnologieal measurements from 1955 onwards reveals a consistent decline in water clarity, a large and possibly exponential increase in hypolimnetic oxygen demand, and a conspicuous shift in the summer phytoplankton community towards blue‐green algal dominance. This recently accelerated change in the trophic status of Lake Rotoiti is probably a response to the Ohau Channel inflow from Lake Rotorua.

ISSN:0028-8330    

DOI:10.1080/00288330.1984.9516064

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The processes of nitrate removal from the stream waters of 2 headwater catchments were studied. In study stretches where the stream channels were vegetated with thick mats of grass (Gly‐ceria fluitans),nitrate removal processes were particularly active. In such grassed stream channels, c. 75% of the nitrate removal was attributable to plant uptake and the remainder to denitrifica‐tion. Both of these nitrate removal processes were linearly dependent on nitrate concentration, resulting in an exponential decline of nitrate level from the springs along the stream's length. Regeneration of nitrogen, by plant decay within the stream channel, results in export of dissolved organic nitrogen and paniculate nitrogen from the catchments. The overall impact of vegetated stream channels in modifying nitrogen exports from catchments is discussed.

ISSN:0028-8330    

DOI:10.1080/00288330.1984.9516065

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Nitrate concentrations in urban streams at Rotorua are much higher than those in nearby rural streams. The loads of nitrogen are consistent with the loads discharged to septic tanks in the stream catchments. Phosphorus concentrations are no higher than in rural streams, and phosphorus loads in the streams are less than 2% of the load on the septic tanks. Nitrate in the streams is slowly decreasing now that the sewerage reticulation system is almost complete.

ISSN:0028-8330    

DOI:10.1080/00288330.1984.9516066

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Water bodies can be characterised optically by the euphotic depth, zeu(1% of surface light), the diffuse attenuation coefficients,Kdfor down‐welling light andKufor upwelling light, and the reflectance coefficient,R(ratio of upwelling to downwelling light), all in terms of photosyntheti‐cally active radiation (PAR). The estimation of all of these quantities from underwater PAR measurements is simple in principle but very difficult in practice under changing ambient light conditions caused by drifting cloud patches. A method of PAR measurement using a two‐channel instrument which records the ratio of the response of 2 PAR sensors and thus overcomes the problems of changeable ambient light is described. Relative PARQ(z)/Qr,whereQ(z)is PAR (either upwelling or downwelling) at depth z, andQTis reference (downwelling) PAR, is much less dependent on ambient light when the reference sensor is located in water than when located in air (deck sensor). The profiles of relative PAR can be used to calculate zeu,Kd,andKu. Rcan be measured directly as the ratio of upwelling to downwelling PAR.

ISSN:0028-8330    

DOI:10.1080/00288330.1984.9516067

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Ohiwa Harbour is a 24 km2estuarine lagoon impounded by the 6 km long Ohope spit in the west and the 0.7 km long Ohiwa spit in the east. These barrier sand spits are presently separated by a c. 340 m‐wide inlet channel where the maximum harbour depth of 14 m occurs. Seventy percent of the harbour consists of tidal flats supporting a rich shelly benthos and diversified by stands of mangrove and backed locally by salt marsh. Lower harbour sediments in barrier beach, dune, and entrance shoal and channel environments are well sorted, negatively‐skewed, medium to fine sands. In contrast, upper harbour sediments are poorly to very poorly sorted, positively‐skewed, medium to very fine (silty) sands, the coarser of these deposits occurring in channel and restricted harbour beach environments, and the finer in inter‐tidal flat, creek, and channel bank areas. The terrigenous mineralogy is consistent with a dominantly acid volcanic provenance, directly from the tephra mantle of the catchment and, most importantly, indirectly from the oceanic littoral zone. Sediment dispersal is dominated by tidal currents. Speeds decrease systematically up‐harbour from maximum values of 100–150 cm s‐1at the inlet channel to 5–10 cms‐1in upper‐harbour reaches. Current ripples, megaripples, and sand waves characterise the higher energy, current‐dominated lower harbour deposits, hereas small‐scale current and wave ripples, together with biogenic markings and burrows, characterise the lower energy, inner harbour deposits. Small amplitude, wind‐forced waves are important for resuspending and moving sediment in intertidal areas, particularly on the upper tidal flats. Most areas of the harbour are affected by biological processes. Rapid growth of Ohope barrier spit resulted from increased eastwards transport of littoral sands around Whakatane Heads, west of Ohiwa Harbour. The probable cause of this was the infilling of the up‐drift Rangitaiki Plains embayment which was essentially completed soon after the time of the Taupo Pumice eruption (AD 131). Over the last 2000 years Ohope spit has accreted laterally eastwards at an average rate of about 3 m y ‘, Ohiwa spit has concomitantly eroded, and there has been accelerated infilling of Ohiwa Harbour.

ISSN:0028-8330    

DOI:10.1080/00288330.1984.9516068

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0028-8330    

DOI:10.1080/00288330.1984.9516069

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor