Breeding in the freshwater crayfish paranephrops planifrons white

The breeding cycle of female Paranephrops planifrons is described. The incubation of eggs and young takes place between April and December and covers about 25–26 weeks. The winter population contains some apparently adult females which do not breed. The number of eggs laid increases with the size of the parent, and in the population studied varied from some 20 to 30 eggs at 17 mm carapace length to 150 eggs at 30 mm carapace length. After hatching the young pass through two moults while still attached to the parent.     

Larval life span of the echinoid evechinus chloroticus (val.)

Newly metamorphosed Evechinus chloroticus (Val.) were observed in three larval cultures 36, 30, and 28 days after fertilisation, indicating that the free swimming larval life may last about 1 month.     

Role of mean circulation,tides, and waves in the transport of bottom sediment on the New Zealand continental shelf

Evaluation of velocity data on water movements over the New Zealand continental shelf has revealed that the mean circulation by itself is too slow to induce transport of bottom sediments. Tides generally have higher velocities, but are still not the main transporting agent except in the tide‐dominated Cook and Foveaux. Straits. Waves have the potential to stir sediments on the inner and middle shelf (less than about 70 m deep) during annual storms, and probably down to 130 m depth during the maximum 25‐y storm.

For sediment transport to take place, energies of at least two of the major water movements would have to complement one another. Optimum conditions for transport probably occur during storm periods when wave‐suspended sediment is readily moved by tides and the mean circulation.

The direction of transport is mainly along the continental shelf and is largely in response to prevailing weather patterns coincident with the direction of the mean circulation and strongly reinforced by the appropriate phase of the tide.     

Letters to the editor

A preliminary scuba survey of oligotrophic Lake Rotoma in 1972 revealed a vegetation mainly composed of native hydrophytes in which exotics were at an early stage of colonisation. In 1973 the presence of species was recorded in 5708 quadrats (625 cm²) at 1 m intervals along a total of 50 line transects placed systematically around the lake. Water depth was measured, and quadrat cover and substrate type were subjectively estimated. Species frequency calculations showed that the dominant vegetation pattern was a characean meadow of Chara fibrosa f. acanthopitys (A.Br.) R.D.W., Nitella leptostachys var. leonhardii (R.D.W.) R.D.W., and N. pseudoflabellata var. mucosa (Nordst.) Bailey. The charophytes extended over a depth range of 1–17.5 m on a wide variety of substrates and gradients. Native vascular plants were absent from many transects, and had a depth range only from 0 to 4.5 m, with most occurring above 3.5 m. The Low Mixed Community, found in shallow water less than 1.25 m in depth at the northeast end of the lake, provided this area with a high species diversity. Exotic hydrophytes had established in many areas around the lake. The distribution of Lagarosiphon major (Ridley) Moss and Elodea canadensis Michx. appeared to coincide with boating access and fallen submerged trees over a depth range of 0–6.0 m, although much of the available habitat had not yet been exploited. Emergent species were most abundant within the southwest inlet and also in the lagoons surrounding the lake where sheltered conditions and shallow gradients prevail.     

New distribution records of macrothricid Cladocera in New Zealand

Neothrix armata is recorded for the first time from Lakes Rotorua and Rotokakahi, and Streblocerus serricaudatus from Lake Tikitapu.     

东平湖畔涝洼荒地渔农牧综合开发利用措施的探讨

东平湖畔涝洼地年仅亩产细苇400—500kg,价值10—20元。采用渔农牧综合开发利用的措施,亩产鱼、粮、猪1000kg。其措施为: 1.改涝洼荒地为台田、鱼池。2.台田种粮食。3.鱼池采用光合细菌微生物技术并产体养殖,多种鱼及蚌、珍珠等。4.产品循环利用。粮食作物的副产品做猪饲料;猪粪做鱼饲料肥料;鱼粪回田做作物的肥料。     

南四湖湖内浅槽工程施工对水环境的影响及控制措施

南四湖湖内工程是沂沭泗河洪水东调南下续建工程的单项工程,工程区位于山东省省级自然保护区内;挖泥船施工将对湖内水环境产生一定影响。本文从排泥场回水污染物、生产废水和生活污水三个方面阐述了工程施工对水环境的影响程度,并且提出了相应的控制措施。     

巢湖微囊藻毒素异构体组成的时空分布特征及影响因子

有害蓝藻释放微囊藻毒素（MCs）,严重威胁饮用水源地用水安全.为了解巢湖MCs污染状况及其异构体组成对水质的影响,于2012年夏季（8月）和秋季（11月）,2013年冬季（2月）和春季（5月）进行采样分析,研究了巢湖水体中胞内微囊藻毒素（IMCs）和胞外微囊藻毒素（EMCs）异构体的时空分布及其与环境因子的关系.结果发现,IMCs和EMCs的平均浓度变化范围分别为0.12~6.45 μg/L和0.69~1.92 μg/L.在3种常见的异构体中,MC-RR和MC-LR比例较高,MC-YR最低,MC-RR和MC-LR是巢湖水体中MCs的主要异构体类型.IMCs和EMCs的异构体浓度及其比例呈现不同的时空分布特征.微囊藻生物量、水温、总磷浓度是影响IMCs和EMCs异构体浓度及其组成变化的关键环境因子.本研究表明巢湖富营养化严重的西湖区夏季能合成更多的MC-RR异构体,而秋、冬季节偏向于释放生理毒性更强的MC-LR异构体.了解MCs异构体组成变化及其关键影响因素,有助于预测预警水体MCs污染状况和评估饮用水源地MCs风险.     

Characteristics and implications of some Loch Lomond Stadial moraine ridges and later landforms,eastern Lake District,northern England

Moraine ridges and mounds of inferred Loch Lomond Stadial (LLS) age have been mapped at three sites (Fordingdale, Swindale and Wet Sleddale) in part of the eastern Lake District, northern England, and indicate glaciers were more widespread than envisaged by Sissons (1980, Transactions of the Royal Society of Edinburgh: Earth Sciences, Vol. 71, pp. 13–27). The moraines delimit closely the downslope/downvalley limits of the former glaciers but there is no geomorphological evidence with which to define their upslope/upvalley margins. The former glaciers are considered to have been nourished within the confines of their individual valley, cirque and hillside embayment respectively, rather than being outlet glaciers of plateau icefields. Estimated equilibrium line altitudes (ELAs) are within the range of values determined previously for LLS glaciers in the Lake District and do not necessitate revision of established palaeoclimatic parameters. Individual ELAs were probably influenced by local factors; all three former glaciers had accumulation-area aspects between north and east, limiting the impact of direct solar radiation during the ablation season, and were adjacent to extensive areas of high ground to the west and/or south that would have facilitated transfer of snow to their surfaces by winds from those directions. In Fordingdale, three essentially contemporaneous depositional landforms occur upslope of the moraines and are considered to represent hillslope adjustments following wastage of glacier ice from the site. © 1998 John Wiley & Sons, Ltd.