Exploring interactions among intertidal macrozoobenthos of the Dutch Wadden Sea using population growth models

Using data taken from three long-term monitoring programs, we modelled the population dynamics of 13 common macrozoobenthic species of the Balgzand, an approximately 50 km² intertidal area in the Dutch part of the Wadden Sea. In order to identify likely interactions among species, while accounting as much as possible for other factors influencing population dynamics, models included both ‘environmental’ (water temperature, and phytoplankton concentration) and ‘biological’ (biomass of potentially interacting species) variables. This approach appeared to be effective at identifying certain types of interactions acting over relatively short time-frames, such as predation and competition for food. Among the species we considered, the strongest effects of this kind appeared to be from what we presume to be predation by Nephtys hombergii, and from competition for food among bivalves. Several of the strongest results of our analysis corroborated expectations derived from previous small-scale surveys or experimental studies, but there were also a number of highly significant results indicating possible interactions which were not immediately explicable, including the apparent positive effect of Macoma balthica on Arenicola marina, and the apparent negative effect of Nephtys hombergii on Mya arenaria. Our results also suggest that year to year changes in Cerastoderma edule and Arenicola marina populations did not have substantial and widespread influences on the population dynamics of the majority of other common infauna, which is not to deny the likely critical importance of recruitment effects and biogenic transformation of the intertidal environment by these species over longer time frames. Our modelling approach could be applied to other long-term data sets, and will become more useful as longer time series become available.     

Deprivation and the 1991 census

"This article looks at the patterns of relative deprivation in different types of area [in England and Wales], explores the connection between deprivation and other variables which might indicate disadvantage, and suggests some further lines of research which might be explored. It explains, in an inset, how to go about calculating an index of deprivation using a Census CD-ROM and a spreadsheet."     

Reviews

THE DICTIONARY OF HUMAN GEOGRAPHY edited by R. J. Johnston. 20 x 13 cm, xix and 411 pages. Blackwell: Oxford 1983 (ISBN 0 631 13465 4) $A13.95 (limp).

THE GEOGRAPHY OF AUSTRALIAN CORPORATE POWER edited by Michael Taylor. 22 x 14 cm, ix and 230 pages. Croom Helm Australia: Sydney 1984 (ISBN 0 949614 06 8) $A24.95 (cloth).

MULTINATIONALS AS MUTUAL INVADERS: Intra‐industry Direct Foreign Investment edited by A. Erdilek. 14 x 22 cm, xii and 217 pages. Croom Helm: London 1985 (ISBN 0 7099 0935 7) $A39.95 (cloth).

UNEVEN DEVELOPMENT: Nature, Capital and the Production of Space by N. Smith. 15 x 22 cm, xv and 198 pages. Basil Blackwell: Oxford 1984 (ISBN 0 631 13564 2) $A59.95 (cloth); (ISBN 0 631 13685 1) $A18.95 (limp).

SOCIAL THEORY AND THE AUSTRALIAN CITY (Studies in Society No. 26) by L. Kilmartin, D. Thorns and T. Burke. 14 x 21 cm, ix and 218 pages. George Allen and Unwin: Sydney 1985 (ISBN 0 86861 405) $A24.95 (cloth); (ISBN 0 86861 413 0) $A12.95 (limp).

THE FUTURE OF URBAN FORM: The Impact of New Technology edited by J. Brotchie, P. Newton, P. Hall and P. Nijkamp. 14 x 22 cm, xiii and 374 pages. Croom Helm: London 1985 (ISBN 0 7099 3255 3) $A44.95 (cloth).     

Seasonal and Annual Fluxes of Nutrients and Organic Matter from Large Rivers to the Arctic Ocean and Surrounding Seas

River inputs of nutrients and organic matter impact the biogeochemistry of arctic estuaries and the Arctic Ocean as a whole, yet there is considerable uncertainty about the magnitude of fluvial fluxes at the pan-Arctic scale. Samples from the six largest arctic rivers, with a combined watershed area of 11.3?×?10⁶?km², have revealed strong seasonal variations in constituent concentrations and fluxes within rivers as well as large differences among the rivers. Specifically, we investigate fluxes of dissolved organic carbon, dissolved organic nitrogen, total dissolved phosphorus, dissolved inorganic nitrogen, nitrate, and silica. This is the first time that seasonal and annual constituent fluxes have been determined using consistent sampling and analytical methods at the pan-Arctic scale and consequently provide the best available estimates for constituent flux from land to the Arctic Ocean and surrounding seas. Given the large inputs of river water to the relatively small Arctic Ocean and the dramatic impacts that climate change is having in the Arctic, it is particularly urgent that we establish the contemporary river fluxes so that we will be able to detect future changes and evaluate the impact of the changes on the biogeochemistry of the receiving coastal and ocean systems.     

The Processing and Impact of Dissolved Riverine Nitrogen in the Arctic Ocean

Although the Arctic Ocean is the most riverine-influenced of all of the world’s oceans, the importance of terrigenous nutrients in this environment is poorly understood. This study couples estimates of circumpolar riverine nutrient fluxes from the PARTNERS (Pan-Arctic River Transport of Nutrients, Organic Matter, and Suspended Sediments) Project with a regionally configured version of the MIT general circulation model to develop estimates of the distribution and availability of dissolved riverine N in the Arctic Ocean, assess its importance for primary production, and compare these estimates to potential bacterial production fueled by riverine C. Because riverine dissolved organic nitrogen is remineralized slowly, riverine N is available for uptake well into the open ocean. Despite this, we estimate that even when recycling is considered, riverine N may support 0.5–1.5 Tmol C year⁻¹ of primary production, a small proportion of total Arctic Ocean photosynthesis. Rapid uptake of dissolved inorganic nitrogen coupled with relatively high rates of dissolved organic nitrogen regeneration in N-limited nearshore regions, however, leads to potential localized rates of riverine-supported photosynthesis that represent a substantial proportion of nearshore production.     

The Arctic Ocean Estuary

Large freshwater contributions to the Arctic Ocean from a variety of sources combine in what is, by global standards, a remarkably small ocean basin. Indeed, the Arctic Ocean receives ∼11% of global river discharge while accounting for only ∼1% of global ocean volume. As a consequence, estuarine gradients are a defining feature not only near-shore, but throughout the Arctic Ocean. Sea-ice dynamics also play a pivotal role in the salinity regime, adding salt to the underlying water during ice formation and releasing fresh water during ice thaw. Our understanding of physical–chemical–biological interactions within this complex system is rapidly advancing. However, much of the estuarine research to date has focused on summer, open water conditions. Furthermore, our current conceptual model for Arctic estuaries is primarily based on studies of a few major river inflows. Future advancement of estuarine research in the Arctic requires concerted seasonal coverage as well as a commitment to working within a broader range of systems. With clear signals of climate change occurring in the Arctic and greater changes anticipated in the future, there is good reason to accelerate estuarine research efforts in the region. In particular, elucidating estuarine dynamics across the near-shore to ocean-wide domains is vital for understanding potential climate impacts on local ecosystems as well as broader climate feedbacks associated with storage and release of fresh water and carbon.     

塔里木盆地库鲁克塔格地区二叠纪末-中三叠世基性岩床的发现及其地质意义

新疆塔里木盆地东北缘库鲁克塔格地区的中寒武统莫合尔山组沉积地层中发现三条形成于二叠纪末到中三叠世的基性岩床。三条岩床沿沉积岩层面顺层侵入,按照从下到上的顺序,分别为辉绿岩床(厚3m)、辉长岩床(厚20m)和粗玄岩床(厚2.5m)。三条岩床的地球化学特征相似,稀土含量高(∑REE=210×10^-6~297×10^-6),轻稀土元素富集((La/Yb)_N =13.54~17.96),Eu负异常不明显(δEu=0.97~1.21),Ce稍具正异常(δCe=1.11~1.25)。大离子亲石元素(Rb、Ba、Th、Sr)富集,Sr具明显正异常; Ta、Nb和Hf具负异常。低氧化度(0.13~0.40)。三条岩床为同源岩浆活动的产物,岩浆源于上地幔或下地壳,但有下陆壳成分混染。三个样品的MgO含量在4%~6%之间,Mg^#值在37.6~55.6之间,固结指数SI值位于18.7~29.3之间,反映原始的岩浆经历了比较明显的分异作用。粗玄岩床K-Ar年龄为255.2±7.3Ma,辉绿岩床K-Ar年龄为242.8±5.7Ma,辉长岩床Ar-Ar年龄为229.7±3.7Ma。本次岩浆侵入事件发生在南天山洋闭合之后,构造背景为造山后碰撞伸展环境。