Use of riverine through reef habitat systems by dog snapper (Lutjanus jocu) in eastern Brazil

The early life history of Western Atlantic snappers from the Southern hemisphere is largely unknown. Habitat use of different life stages (i.e. size categories) of the dog snapper (Lutjanus jocu) was examined across the largest South Atlantic reef–estuarine complex (Abrolhos Shelf, Brazil, 16–19° S). Visual surveys were conducted in different habitats across the shelf (estuary, inner-shelf reefs and mid-shelf reefs). Lutjanus jocu showed higher densities on inner-shelf habitats, with a clear increase in fish size across the shelf. Individuals <7 cm were associated with both the estuary (mangrove and rocky habitats) and inner-shelf reefs (particularly shallow fore-reefs and tide pools). Individuals ranging 10–30 cm were broadly distributed, but consistently more abundant on inner-shelf reefs. Individuals between 30 and 40 cm were more common on mid-shelf reefs, while individuals >40 cm were recorded only on mid-shelf reefs. Literature data indicate that individuals ranging 70–80 cm are common on deep offshore reefs. This pattern suggests that the dog snapper performs ontogenetic cross-shelf migrations. Protecting portions of the different habitats used by the dog snapper during its post-settlement life cycle is highlighted as an important conservation and management measure.     

The feeding and diet of the deep-sea shrimp Aristeus antennatus off the Balearic Islands (Western Mediterranean): Influence of environmental factors and relationship with the biological cycle

Spatio-temporal variation of feeding intensity and diet in the red shrimp Aristeus antennatus was studied at two locations around the island of Mallorca (Balearic Islands, Western Mediterraean) in August, September, and November 2003, and in February, April and June 2004 at depths between 550 and 750 m. The two areas, with different oceanographic conditions, were respectively located in the northwest (Sóller) and the south (Cabrera) of Mallorca. Off Sóller, feeding intensity of A. antennatus showed a significant increase from February to April and June 2004 in all the three size-classes studied (small shrimps: CL < 30 mm; medium: CL between 30 and 40 mm; large: CL ? 40 mm). Off Cabrera, the highest fullness was recorded in November 2003 among small and medium shrimp, while only large specimens showed patterns similar to that found off Sóller. Off Sóller, the diet of both small (CL < 34 mm) and large (CL ? 34 mm) A. antennatus was mainly influenced by season, with three dietary groups corresponding to August-September 2003, to November 2003/February 2004, and to hauls from April to June 2004. Off Cabrera, hauls (representing diets) were grouped by depth, never by season. The most remarkable seasonal shift in the diet of A. antennatus off Sóller was the increase of mesopelagic prey in April-June relative to other months. In all size categories there was an increase off Sóller in the energy intake of prey ingested from February to June 2004, an increase not found off Cabrera. Degree of digestion of mesopelagic prey indicated nocturnal feeding on mesopelagic fauna. These prey probably have a shallower depth distribution at night than found in our daylight sampling, and possible migratory movements among prey and A. antennatus at night would explain the lack of correlation between prey abundance in guts and in the environment found during daylight periods for most micronekton mesopelagic prey (euphausiids, myctophids and sergestids). Off Sóller, fullness and diet were significantly linked to temporal changes in water column productivity (e.g., Chl a readings, fluorescence) and to changes in the shrimp biology (lipid content of hepatopancreas, Gonado-somatic Index, GSI). Off Cabrera, we found a higher dependence of fullness and diet with T and S, both variables in turn related to depth. The increase of stomach fullness and dietary energy intake in pre-reproductive females from February to April-June 2004 found off Sóller, coupled with the consumption of mesopelagic prey, was parallel to a significant increase of the gonad weight (GSI, fecundity) in June. Most individuals attain gonad development in the period May-June, after two months of the peak of primary production at the surface. The strong link found between pelagic resources and reproductive processes in a deep-sea species such as the shrimp Aristeus antennatus, situated near the top of the trophic web, suggests a rapid energy flow via mesopelagic fauna between surface primary production and bathyal megabenthic communities at oligotrophic insular areas. In contrast to mainland areas off the Catalan coasts submitted to the influence of submarine canyons, around the island of Mallorca the empoverishment of benthos biomass may enhance consumption of micronektonic prey and a possible accumulation of pre-reproductive females of A. antennatus in areas (e.g., steep slopes and persistent frontal systems found off Sóller) with high zooplankton aggregations.     

Altered Benthic Prey-Availability Due to Episodic Oxygen Deficiency Caused by Drifting Algal Mats

Abstract. Large quantities of drifting algal mats have become a common phenomenon on shallow sandy bottoms in the northern Baltic Sea. A decomposing algal mat rapidly induces hypoxic or anoxic conditions in the underlying sediment and interferes with the normal living-mode of the benthos, i.e., mobility, feeding, and predator-prey relationships. Field surveys have shown that bivalves, such as Macoma balthica , avoid the unfavourable anoxic conditions by emerging at the sediment surface. Due to low reburrowing rates these bivalves are exposed to epibenthic predators once the drift algae disperse. A series of aquarium experiments were conducted to test for differences in the survival of M. balthica when exposed to continuous predation without prior stress and short-term predation after hypoxic stress induced by algae (= 20% 02-saturation). Sublethally stressed adult M. balthica , that normally are outside the size-range of the isopod predator Saduria entomon , became significantly more susceptible to predation when lying exposed at the sediment surface. The same effects were found with two other predators, the brown-shrimp Crangon crungon and the flounder Platichthysflesus . Drift algal mats induced an escape-reaction in the infauna more rapidly than mere hypoxia. This response is affected by temperature. which further underlines the importance of drift algae influencing prey availability. This paper discusses the role of the drift algae as a regulating factor for the infauna and demonstrates the importance of external structuring factors, such as hypoxic stress and algal mats, on predator-prey interactions.     

论全球岩石圈板块构造的动力学机制

全球板块构造的动力学机制问题是一个热门但至今尚未解决的难题。本文首先回顾了近百年来大地构造学的各种主要假说和近四十年来板块构造学说的许多新进展。在上述研究的基础上, 受Rampino和Stothers关于陨击作用可引起地表重大灾变事件思想的启发,笔者提出了一个新的假说。基于中、新生代(200 Ma以来)每隔33 Ma太阳系就会穿越一次银河系星际物质密集的银道面,诱发太阳系内部引力场的巨变,使部分小行星失稳,从而撞击地球。笔者根据用以描述中生代以来全球板块构造的七种不同的运动模式, 提出了巨大陨星在不同地点、以不同角度撞击地表岩石圈,可能诱发地幔底辟的形成,从而推动板块呈放射状或单向运移的假说,也即在200、170、100、65和0.78 Ma等时期的陨击事件基本上是垂直地表面而撞击的,从而诱发地幔底辟的形成和岩石圈板块的放射状张裂和运移;138 Ma的陨击事件可能是指向印度板块的斜向撞击;而35 Ma时期的微玻璃陨石撞击事件则是陨石以极低角度撞击地球表面的表现。陨石撞击地球,这是太阳系内部各星体之间引力作用变化的表现,因而此假说不是什么外因作用论。     

The vertical distribution of maraena whitefish (Coregonus maraena) early juveniles in different times of day in a newly created oligotrophic lake

Diel vertical distribution of strictly pelagic juvenile (23–47 mm total length) maraena whitefish Coregonus maraena (Bloch, 1779) was repeatedly investigated in spring primarily using hydroacoustics in the artificial post-mining Most Lake in the Czech Republic. At the same time, an ichthyoplankton trawl was used to identify acoustical targets. During the day, fish performed extensive shoaling behaviour in depths between 2 and approximately 40 m and were not accessible for trawling. By evening, with decreasing light intensity, shoals started to disintegrate and at night fish were relatively homogeneously distributed in the water column from the surface down to a depth of 40 m. Juvenile maraena whitefish could be caught by trawl as the only fish species at night. Shoaling behaviour started again approximately 1.5 h before sunrise. The data showed steep decreases in fish density between the two surveys in spring which indicates significant mortality of early juvenile coregonids as a result of poor availability of zooplankton in a highly oligotrophic post-mining lake.     

Sediment and hydrodynamics of the Tauranga entrance to Tauranga harbour

To relate the textural characteristics of the bottom sediments of a tidal inlet to hydrodynamics, 45 sediment samples from the Tauranga Entrance to Tauranga Harbour were analysed for textural parameters, and tidal currents and waves were monitored. Tidal currents dominate sediment transport processes near the Tauranga Entrance although swell waves are significant on the ebb tidal delta, and wind waves may influence intertidal sediments within the harbour. The bulk of the sediment is probably derived from marine sand from the Bay of Plenty continental shelf, but tidal currents and waves have changed its textural character. In areas of swift tidal currents, particularly in the inlet channel itself, sediment is coarser, more poorly sorted, and more coarsely skewed than that in areas of slower currents.     

贾湖史前人类迁移行为的初步研究——锶同位素分析技术在考古学中的运用

位于河南省舞阳县的贾湖遗址是一处著名的新石器时代遗址,距今7800～9000年。遗址中出土了大量的人和动物的骨骼与牙齿,这为研究史前时期中国中部地区人类的迁移情况提供了很好的材料。在本次研究中,共分析了26个人和动物样品,包括12个人体骨密质样品、9个人牙釉质样品和5个猪牙釉质样品。测定了每个样品的锶同位素浓度和87Sr/86Sr比值,结果表明猪牙釉质的锶同位素浓度（平均值为196±51ppm,n=5,1σ）高于人牙釉质的浓度（平均值为110±61ppm,n=9,1σ）,人骨骼的锶同位素浓度（平均值为444±173ppm,n=12,1σ）明显地高于人牙釉质的浓度。根据5个猪牙釉质样品87Sr/86Sr平均值±2倍的标准偏差确定的当地锶同位素比值范围（0.712205～0.712420）,发现14个人类个体中有5个是外来迁入的,并且从第1期到第3期人口的迁移率有增加的趋势。这是在国内首次利用锶位素分析方法对古人类的迁移现象进行研究,同时也表明此方法可以很好地判断古人类迁移行为。