Land snails from the last glacial maximum on Andikithira,southern Greece and their palaeoclimatic implications

An assemblage of land snails from an aeolianite deposit on the coast of the southern Greek island of Andikithira is shown to date to 16 000 yr BP and thus represents the period of the last glacial maximum (LGM; Oxygen Isotope Stage 2). The assemblage has no modern analogue. Five of the ten species are extinct on the island and some of these now live only at high elevations (> 950 m). Significantly cooler temperatures, some 5-8°C below present, and slightly drier moisture conditions (lower rainfall, partially offset by reduced evapotranspiration at the lower temperature) are inferred. The large temperature depression at the LGM, well documented in northern and central Europe, extended also to the Mediterranean climate of southern Europe. Late Quaternary climatic changes had a considerable impact on the fauna of this isolated island.     

Biogeography, Substrate Preference, and Feeding Types of North Adriatic Intertidal Collembola

Abstract. A survey of North Adriatic intertidal Collembola is given, including the first records of Friesea acuminata, Archisotoma interstitialis, Entomobrya dollfusi , and Pseudosinella hauseri. Granulometric and biococnological analyses of culittoral loose sediments allowed determination of the animals' substrate preference. The limitation to cuhaline habitats is tested by comparison with mixohaline shores nearby. Life-form typology is applied to elucidate the largely unknown relations of intertidal Collembola to the sediment surface or superficial strata. The different modes of nutrition are distinguished by mouthparts and by gut content analyses.     

Migration dynamics of clupeoids in the Schelde estuary: A stable isotope approach

Large numbers of young of the year herring (Clupea harengus L.) and sprat (Sprattus sprattus (L.)) typically enter and remain within North Sea estuaries during the winter months. The main purpose of this study was to examine their migration dynamics between the North Sea and the Schelde estuary using C and N stable isotopes. Prior to this, stomach contents were used to verify the isotopic differences between the food sources at the sampling stations. From May 2000 to April 2001 fish were collected monthly in the upper and lower estuary. Muscle tissue and stomach contents were analyzed for δ¹³C and δ¹⁵N using an EA-IRMS. Based on the stomach contents, it was demonstrated that δ¹⁵N could not be used as a tracer for fish migration because the longitudinal estuarine δ¹⁵N gradient had reversed completely during autumn. The δ¹³C gradient, however, was found to be reliable for studying fish movement in the Schelde estuary.Seasonal movements of clupeoids in the Schelde estuary were analyzed by separating the temporal abundance patterns into migration groups based on their muscle isotopic composition. Immigration and emigration seem to occur continuously throughout the year. Most exchange occurred in November. During winter, immigration remained high but gradually decreased. Although the herring and sprat abundance further declined in the estuary during February and March, large seaward emigration was not fully demonstrated. As temporal overlap between immigration and emigration is concluded the results support the hypothesis that migration to estuarine nurseries is individually based.     

Assembly processes in upper subtidal macroalgae: The effect of wave exposure

The structure and diversity of sixteen macroalgal assemblages originating from two coastal locations in the Northern (Kavala gulf) and Central (Maliakos gulf) Aegean in Greece were explored by examining their relative abundance distributions (RADs) and fitting five stochastic niche-based models. A mechanistic interpretation of the underpinning assembly processes was attempted by relating the assumptions of the fitted models with available abiotic data corresponding to each assemblage. The random fraction niche-based model, assuming a random niche apportionment to species, was fitted to the majority of Maliakos assemblages characterized by more evenly distributed and speciose RADs, whereas the random assortment model, assuming no relationship among species abundance and niche size, was fitted to most of the Kavala assemblages characterized by steeper RADs with fewer species. Among the possible underlying mechanisms, wave exposure seems to play a key role in macroalgal assembly processes; however factors such as biogeography and hard substrate availability must be also taken into consideration. Short-term processes as changes in resource availability (nutrients and light), known as drivers of assembly rules in other primary producers (e.g. phytoplankton), do not considerably affect macroalgae in the oligotrophic Eastern Mediterranean, possibly due to their longer life spans.     

BOOK REVIEWS

Book Reviewed in this article: Portable Utopia: Glasgow and the United States 1820–1920. Bernard Aspinwall. Studies in Russian Historical Geography. James H. Bater and R. A. French, eds. Water and Sanitation: Economic and Sociological Perspectives. Peter G. Bourne, ed. Green Politics. Fritjof Capra and Charlene Spretnak. The Southern Cone: Realities of the Authoritarian State. César N. Caviedes. Women in Third World Development. Sue Ellen Charlton. Land Management: New Directions. David Chiddick and Alan Millington, eds. Geography and Ethnic Pluralism. Colin Clarke, David Ley, Ceri Peach, eds. Geomorphological Hazards in Los Angeles. R. U. Cooke. Regional Impacts of United States-Mexico Economic Relations. Alfonso Corona and Lay James Gibson. eds. Patterns of Jobs and Geographic Mobility. Torvald Gerger. Cities and Sickness: Health Care in Urban America. Ann Lennarson Greer and Scott Greer, eds. Neighborhoods: Their Place in Urban Life. Howard W. Hallman. Development and the Rural-Urban Divide. John Harriss and Mick Moore, eds. Patterns of Undocumented Migration: Mexico and the United States. Richard C. Jones, ed. Central Place Theory. Leslie J. King. The Geography of Western Europe: A Socio-economic Survey. Paul L. Knox. Regions and Resources: Strategies for Development. David T. Krisge, Daniel A. Seiver, Oliver S. Goldsmith and Michael J. Scott. Geography of Crowding and Human Response. A Study of Ahmedabad City. K. M. Kulkarni. Haciendo Pueblo. The Development of a Guadalajaran Suburb. Kathleen Logan. The Imperial Lion: Human Dimensions of Wildlife Management in Central Africa. Stewart A. Marks. Water in the Hispanic Southwest: A Social and Legal History, 1550–1850. Michael C. Meyer. Imlil: A Moroccan Mountain Community in Change. James A. Miller. Tourism in Canada: Selected Issues and Options. Peter E. Murphy, ed. David Harvey's Geography. John L. Paterson. Raster Scanning, Processing and Plotting of Cartographic Documents. Donna J. Peuquet and A. Raymond Boyle. The USSR and the Muslim World: Issues in Domestic and Foreign Policy. Yaacov Ro'i, ed. Environmental Perception and Behavior: An Inventory and Prospect. Thomas F. Saarinen, David Seamon, and James L. Sell. Incised channels, Morphology, Dynamics, and Control. Stanley A. Schumm, Michael D. Harvey, and Chester C. Watson. The Gap Between Rich and Poor: Contending Perspectives on the Political Economy of Development. Mitchell A. Seligson, ed. Twentieth-Century Richmond. Planning, Politics and Race. Christopher Silver. Land Conservation and Development: Examples of Land-Use Planning Projects and Programs. F. R. Steiner and H. N. van Lier, eds. Biogeography: Recent Advances and Future Directions. J. A. Taylor, ed. Late Quaternary Environments of the Soviet Union. A. A. Velichko, ed. H. E. Wright, Jr. and C. W. Barnosky, eds.     

SANDSTONE WEATHERING THRESHOLDS IN PETRA,JORDAN

From ongoing research examining weathering rates and mechanisms in the Paleozoic sandstones of Petra, Jordan, two possible thresholds have been identified. From a carved Roman Theater built under Vitruvian standards during the first century A.D., a two-meter sampling scheme was used to measure the presently weathered surfaces from a hypothetical false datum determined through originally documented Roman engineering and construction canon. Some 526 depth measurements were made on vertical and horizontal surfaces and correlated to the intrinsic variables of sandstone matrix-to-clast ratios, overall densities, matrix chemistry (Si, Ca, Fe, Al concentrations), and to the extrinsic accumulated annual insolation receipt (mega-joules/m²).

When matrix iron concentrations exceeded 2%, an abrupt decrease in overall weatherability is indicated until weathering is found to have decreased below measurable limits at 4%. It is speculated that matrix iron acts as a sandstone-clast binding agent, reducing clast disaggregation. In sandstone strata with matrix calcium concentrations exceeding 10%, weathering was accelerated with insolation >5200–5300 megajoules/m². It is speculated that the increased heating from insolation is responsible for irregular calcite crystal expansion and contraction causing matrix/clast interface microfracturing, clast disaggregation, and subsequent weathering.

Mean recession rates ranged from 13 to 66 mm/millennium on horizontal surfaces and from 7 to 18 mm/millennium on vertical surfaces. Gross differences in recession rates were attributed to the extrinsic influences of moisture availability (slope) and insolation (aspect), while minor differences were attributed to intrinsic characteristics of matrix chemistry (Fe, Ca), sandstone density, and clast/matrix ratios. [Key words: sandstone, weathering, erosion, Petra, Jordan.]     

具彩色斑纹颅形贝在广西桂林下石炭统黄金组中的发现:兼论颅形贝属的地质地理分布

文中描述了产自广西桂林地区下石炭统黄金组下部的颅形贝属一新种,桂林颅形贝(Cranaena guilinensis)。新种以平直的前结合缘和背壳上发育中槽为特征。在4枚标本上发现保存有放射状的彩色条带,表明该种当时生活在温暖海域的浅水环境。对该属70个种的地质地理分布和生物多样性变化的初步分析表明,该属可能起源于早泥盆世欧美大陆西北缘的老世界区,之后的地理分布和生物多样性发展以北美地区为中心,经历了中泥盆世—晚泥盆世早期和早石炭世2次比较明显的辐射演化、迁移扩散高峰和晚泥盆世晚期的1次严重衰退。第1次高峰是中泥盆世—晚泥盆世早期,该属的生物多样性达到巅峰,生物地理分布范围扩大到欧美大陆之外的西伯利亚板块、哈萨克斯坦板块和华南板块等;第2次高峰是早石炭世,该属的生物多样性虽不及前一次,但获得了最广泛的地理分布,不仅在北方大陆有分布,而且已进入到冈瓦纳大陆边缘。晚泥盆世晚期该属的1次严重衰退显然与F/F灭绝事件有关。早石炭世之后,该属进入衰退阶段,最终在二叠纪初灭绝。     

North Cape — a ‘nursery area’ for the packhorse rock lobster,Jasus verreauxi (Deeapoda: Palinuridae)

In the North Cape area (34°26'S, 173°07'E) there appears to be a concentration of late juvenile packhorse rock lobsters, Jasus verreauxi (H. Milne Edwards'), which subsequently contributes significantly to the nearby fishery for adult J. verreauxi off Cape Reinga. Evidence for this is based on the overall smaller size and fewer mature rock lobsters at North Cape compared to areas nearby, and on the results of tagging experiments carried out during 1976–77. Rock lobsters tagged at North Cape moved 21–514 km, mainly west and south, before recapture at minimum rates of 0.03–2.00 krn.d^‐1. For females at least, the movement away from North Cape usually occurs at about the time that sexual maturity is attained. Rock lobsters tagged near Cape Reinga moved 3–34 km west at minimum rates of 0.04–0.35 km.d^‐1.

Although the closure of the North Cape grounds to rock lobster fishing restricts the taking of the small number of legal‐sized fish available in the area, the restriction ensures less mortality and damage to the undersized fish due to handling.     

Variability in estuarine water temperature gradients and influence on the distribution of zooplankton: a biogeographical perspective

Structure and variability of water temperature gradients and potential influence on distribution of two tropical zooplankters (the mysid Mesopodopsis africana and the copepod Acartia natalensis) and their temperate congenerics (M. wooldridgei and A. longipatella) was investigated over a 10-year period in the Mgazi Estuary, South Africa. Intra- and inter-monthly water temperatures were highly variable, driven primarily by the interactive effects of river runoff, tidal exchange and mouth state. Variability was greatest in summer, temperatures ranging between <13 °C (linked to nearshore upwelling and a wide open mouth) and >30 °C when the mouth was near-closed. A strong horizontal temperature gradient characterised the estuary, the upper reaches remaining consistently warmer compared to the lower estuary. In winter, abundance of the tropical zooplankters showed a positive and significant correlation with increasing distance upstream. No pattern was evident in summer. The temperate species reflected a negative trend in abundance moving upstream during both seasons, but correlations were not significant. In terms of climate change, future population responses remain uncertain. This uncertainty is primarily linked to ongoing changes in the relative dominance of key drivers influencing estuarine water temperatures. Estuary mouth state will also respond to changes in nearshore wind regimes and morphodynamics of the adjacent beach.