Birth seasonality,photoperiod, and social change in the Central Canadian Arctic

Birth seasonally at high latitudes is a complex phenomenon which is undoubtedly affected by a subtle interaction between environmental rhythmicity (most notably in photoperiod and temperature) and cultural adaption. There is intriguing evidence that human gonadotrophic activity (and hence fertility) may be affected by seasonal fluctuations in light intensity and duration. Nevertheless, cultural factors are important insofar as they mediate between environmental rhythmicity and human fertility/birth patterns. This article examines the distribution of births over several decades in an Inuit community located 300 miles north of the Arctic Circle. Several shifts in birth seasonality are noted, the most significant of which is a dramatic shift from pronounced seasonality in the 1970s to non-seasonality in the 1980s. Longitudinal ethnographic fieldwork has allowed an examination of social and economic changes accounting for the rather sudden disappearance of birth seasonality. These include increasing reliance upon wage employment and social assistance, decreased dependence upon subsistence hunting and trapping, changing attitudes on the part of young people entering their prime reproductive years, and the introduction of television, radio, and southern-style recreational activities.     

Genetic differentiation of Elysia timida (Risso, 1818) populations in the Southwest Mediterranean and Mar Menor coastal lagoon

Genetic variation at 10 enzyme loci was analysed in Elysia timida sacoglossan mollusc samples, originating from both coastal lagoon and marine sites. The observed heterozygosity ranged from 0.390 (Los Urrutias) to 0.277 (Tabarca). Marine and coastal lagoon populations were characterised by exclusive alleles.     

Dynamics and management of some coastal dune woodlands near The Hague,The Netherlands

Changes are reported of Crataegus-Betula dune woodlands between 1950–1980 from Meijendel, a calcareous coastal dune system near the city of The Hague, The Netherlands, which is used as a water catchment area. It concerns both woodlands in degradation stage and, more common, woodlands on the increase. Changes were recorded with help of successive vegetation maps, air photos and permanent plot observations. Woodland increase usually occurs on places with groundwater at or near the surface, either because of natural circumstances or as a result of artificial groundwater recharge through infiltration as part of the water catchment activities. The management of both types of woodland is discussed.Nomenclature follows Heukels-van der Meijden (1983), Flora van Nederland, 20th ed. Wolters-Noordhoff, Groningen. Nomenclature of mosses follows Margadant & During (1982), Beknopte Flora van Nederlandse Blad- en Levermossen, Thieme, Zutphen.The authors have pleasure in thanking their colleagues from the Dune Water Works who supplied data on hydrology.     

New ecological information onScytalina cerdale (Pisces: Scytalinidae) from a central California rocky intertidal zone

Synopsis New information regarding the ecology ofScytalina cerdale was obtained over a four year period as a consequence of a long-term marine ecological study at the Diablo Canyon Power Plant (DCPP), San Luis Obispo County, California. Twenty intertidal fish surveys were conducted at approximately quarterly intervals, between March 1979 and June 1983, at three separate rocky shore locations (stations). During each survey, a total of 108 square meters (36 m² per station) was searched for fish during periods of low tide. A total of 280S. cerdale were collected, identified, measured, and released back into the same 4 m² area, from the same intertidal station (Diablo Cove), throughout the study period. This limited intertidal occurrence most likely reflectsS. cerdale microhabitat requirements; a combination of intertidal elevation (mean = +0.3 MLLW), substratum specificity (loose gravel, 5–10mm size range, overlying a base of sand and shell fragments), and degree of wave exposure (semi-protected). Throughout the study,S. cerdale was seasonally more abundant during summer months (June through August) and less abundant during winter months (November through February). The only exception to this abundance trend followed the 1982 winter storms, which coincided with an El Niño event, whenS. cerdale abundance uncharacteristically dropped during the subsequent 1983 spring and summer surveys. Mean total lengths did not vary greatly, reflecting the absence of early juvenile fishes, and relatively high mean fish densities (3.5 fish per m² for 20 surveys) were recorded. Qualitative comparisons betweenS. cerdale abundance and seasonal changes in water temperature indicated an inverse relationship. Gravid females, demersal egg masses, and early juvenile individuals were never observed during the four years of the study. This suggests that unlike most other intertidal fishes, particularly other blennioids,S. cerdale may not utilize the intertidal zone for reproductive and recruitment purposes; Diablo Canyon is the most southerly reported distribution for this intertidal species, and therefore, may not entirely represent the species' biology as a whole.     

Sulphate reduction in oxic and sub-oxic North-East Atlantic sediments

Abstract Oxic and sub-oxic N.-E. Atlantic sediments were examined for sulphate-reducing activity. Oxygen and/or nitrate reduction are probably the dominant mineralisation processes in the abyssal plain sediment studied. A low rate of sulphate reduction (0.1 nmol SO²⁻₄/ml/day) was recorded in the surface 5 cm of the continental slope sediment, together with the presence of a range of sulphate-reducing bacteria (SRB). A higher activity of sulphate reduction (2.2 nmol SO²⁻₄/ml/day) occurred in the continental shelf sediment which led to a small decrease in pore water sulphate and an increase in titration alkalinity. This sediment contained approx. 10²–10³ acetate, lactate and propionate oxidising SRB/ml. No low- M _r organic acids were detected in these sediments. However, amendment with 75 μM acetate stimulated sulphate-reducing activity in the shelf sediment.     

沿海防护林防海煞危害初探

通过后牧村海岸防护林带附近空气中主要盐离子飘尘的观测分析表明,林带对大气盐尘的吸附和截留作用,无林带地区平均沉降量为４．３μｇ．ｍ＾－３．１００ｍ＾－１,通过林带时为１８．４μｍ＾－３．１００ｍ＾－１。林带的吸队量与树种、枝叶形状有关,侧柏对Ｃｌ＾－和Ｎａ＾＋的吸附量分别为６３３０和３３５０ｍｇ．ｋｇ＾－１,而黑松为１５７０和９５０ｍｇ．ｋｇ＾－１,空气中盐尘受天气条件特别是风速的影响,阴天,风速     

The influence of environmental manipulations on inter– and intra–individual variation in food acquisition and growth performance of Arctic charr, Salvelinus alpinus

Repeated measurements of food intake made on juvenile Arctic charr, Salvelinus alpinus , held under different rearing conditions enabled examination of the effects of environmental manipulations on both intra– and inter–individual variations in food intake to be made. This permitted the assessment of the influences of differential food acquisition on individual growth rates and biomass gain. When charr were held in isolation individual fish showed relatively little day–to–day variability in food intake and inter–individual differences in intake were small ('base–fine' values). All fish exhibited positive rates of growth and the overall range was narrow. Nevertheless, there was a highly significant positive correlation between food intake and growth, indicating that those individuals that consumed the greatest quantities of food were also those that had the highest rates of weight gain. The rearing of charr in groups led to increases in both intra– and inter–individual variations in food intake to levels considerably above 'base–line'. This increased variability in food intake was reflected in rates of weight gain being more variable amongst the charr reared in groups, with fish that lost weight often being recorded. Manipulation of the rearing environment had marked influences upon intra–individual variability in food intake, inter–individual differences in food acquisition and rates of weight gain. High stocking densities and exposure of the fish to moderate water currents were most effective in reducing levels of variability to approach those observed under 'base–line' conditions.     

Thinopyrum distichum chromosome morphology and C-band distribution

Thinopyrum distichum is indigenous to the southern and south western coastal shores of South Africa. Like many of the Thinopyrum species it can be hybridized with wheat. The resulting progeny treated with colchicine produce fertile amphiploids. The need to distinguish the Th. Distichum chromosomes from one another and from those of wheat prompted the investigation of the C-band distribution. The chromosome pairs of Th. distichum were distiguishable from each other and from those of wheat using C-band patterns, morphology and size as identification criteria. The chromosomes ranged from heterobrachial to metacentric with interstitial and telomeric C-bands. The C-band patterns of Th. distichum were similar, but not identical, to those of other Thinopyrum species.