Late Quaternary contourites and glaciomarine sedimentation in the Fram Strait

Two sites in the eastern Fram Strait, the Vestnesa Ridge and the Yermak Plateau, have been surveyed and sampled providing a depositional record over the last glacial‐interglacial cycle. The Fram Strait is the only deep‐water connection from the Arctic Ocean to the North Atlantic and contains a marine sediment record of both high latitude thermohaline flow and ice sheet interaction. On the Vestnesa Ridge, the western Svalbard margin, a sediment drift was identified in 1226 m of water. Gravity and multicores from the crest of the drift recovered turbidites and contourites. ¹⁴C dating indicates an age range of 8287 to 26 900 years BP (Early Holocene to Late Weichselian). The Yermak Plateau is characterized by slope sediments in 961 m of water. Gravity and multicores recovered contourites and hemipelagites. ¹⁴C ages were between 8615 and 46 437 years BP (Early Holocene to mid‐Weichselian). Downcore dinoflagellate cyst analyses from both sites provide a record of changing surface water conditions since the mid‐Weichselian, suggesting variable sea ice extent, productivity and polynyas present even during the Last Glacial Maximum. Four layers of ice‐rafted debris were also identified and correlated within the cores. These events occurred ca at 9, 24 to 25, 26 to 27 and 43 ka, asynchronous with Heinrich layers in the wider north‐east Atlantic and here interpreted as reflecting instability in the Svalbard/Barents Ice sheet and the northward advection of warm Atlantic water during the Late Weichselian. The activity of the ancestral West Spitsbergen Current is interpreted using mean sortable silt records from the cores. On the Vestnesa Ridge drift the modern mass accumulation rate, calculated using excess ²¹⁰Pb, is 0·076 g cm^?2 year^?1. On the Yermak Plateau slope the modern mass accumulation rate is 0·053 g cm^?2 year^?1.     

厦门湾沉积物中有害有毒甲藻休眠孢囊及塔玛亚历山大藻的潜在危害

本工作通过分析厦门湾表层沉积物中的甲藻休眠孢囊，发现了1种有毒塔玛亚历山大藻(Alexandrium tamarense)休眠孢囊，及两种有害甲藻休眠孢囊：锥状斯氏藻(Scrippsiella trochoidea)、具刺膝沟藻(Gonyaulax spinifera)．对塔玛亚历山大藻进行了培养。并初步研究了该藻的毒性及贝类对其毒素的积累．研究结果表明，厦门海域沉积物中的塔玛亚历山犬藻是有毒的．它的较适宜生长环境条件是：水温20～25℃．盐度为25～30，光照度为3000～50001x．塔玛亚历山大藻在每年的4月26日至6月10日、10月11日至11月20日可能会形成有害藻华，危害厦门海域的海洋生物并可能威胁到人类的健康和生命安全．     

南海甲藻卡氏前沟藻的生长特性研究

从海南省三亚海域收集分离了甲藻卡氏前沟藻Amphidinium carterae藻种,并在实验室成功进行了人工培养,同时对其生长特性进行了研究。实验结果表明,接种初始的细胞密度对其生长率和最高细胞密度影响很小,实验室培养和大量养殖可以采取低密度接种;最适宜培养的环境条件盐度为34,温度为26℃,营养盐浓度为2K。在温度为18—30℃、盐度为26—42、K培养液浓度系列为1/16—2 K的条件下都可存活,最大指数期平均生长率为0.958分裂.d-1,获得的最大细胞密度为7.27×105cells.ml-1。实验结果与属温带的胶州湾同物种对比,表明该藻种生长特性与温带品系有明显差异。     

Alkaline Phosphatase Activity in the Red-Tide Dinoflagellate, Ptychodiscus brevis

Abstract. Alkaline phosphatase activity (APA) was found in a nearshore, natural population of the red-tide dinoflagellate Ptychodiscus brevis. Initial hydrolysis rates were enhanced by two orders of magnitude within 24 h upon addition of ammonium. Other nutrient (additions) or no additions also lead to a higher, although less pronounced increase in activity. Enhanced growth after nutrient additions combined with specific APA indicated that the bloom was both N and P limited. Since the natural population was a mixture of diatoms and the dinoflagellate, APA was also measured in unialgal cultures of P. brevis. APA was not reduced but enhanced by the addition of low concentrations of orthophosphate (0.5 and 1 μM). Higher orthophosphate concentrations (5 to 20 μM) reduced APA, although activity returned to control levels within 2 to 6h. Repression occurred within 30 sec after a 20 μM orthophosphate addition. Cells which had APA repressed by an orthophosphate addition regained their initial activity within 2 h after washing with phosphate-free media. Phosphorus-deficient cells of P. brevis possess an alkaline phosphatase system which is capable of continued activity at low in situ orthophosphate levels.     

海洋有毒甲藻Coolia monotis的研究 II.培养条件的测定

1 998年 5— 9月 ,通过培养实验 ,研究了海洋底栖性有毒甲藻Cooliamonotis人工培养生长所需的理化条件。结果表明 ,培养水体深度较小而水平横截面积较大有利于获得较高产量。温度 1 6— 3 2℃、盐度 2 4— 3 8、K培养液浓度系列 1 /8K— 2K、培养液pH为 6 .5— 9.5都可存活 ,最大指数期平均生长率为 0 .6 9division·d- 1 ,获得的最大细胞密度为 6× 1 0 4 cells·ml- 1 ,是一种适应性较强的微藻。保种条件以温度 2 4℃、盐度 3 4、培养液浓度K ,pH为8.0为佳。     

Multi-proxy evidence of long-term changes in ecosystem structure in a Danish marine estuary, linked to increased nutrient loading

This paper presents a study of changes in eutrophication over the past 100 years in a fertile estuary. The Danish estuary Mariager Fjord is a long, narrow sill-fjord with a permanently anoxic basin. In 1997 anoxia spread from the basin to the entire inner estuary, killing almost all eukaryotes and prompting debate on the causes. This paper reports a multi-proxy survey of ²¹⁰Pb-dated sediment cores from the anoxic basin. Analyses of diatoms, dinoflagellates, pigments and geochemical proxies were used to determine changes in ecosystem structure over the past 100 years. The aim was to establish ‘base-line conditions’, for management purposes, of the biological structure prior to 1900, and to examine possible causes of changes observed. Geochemical proxies total nitrogen (TN), total carbon (TC) and biogenic silica (BSi) were consistently high throughout the sediment record. Increased concentrations of pigments and natural isotopes (δ¹³C, δ¹⁵N) suggested increasing production and nutrient loading. The main changes in the biological proxies occurred between 1915 and the 1940s, and indicated that the estuary has been somewhat eutrophic since 1900, but that the eutrophication process increased over the past 100 years. A reconstruction of TN concentration by a diatom-based transfer function supports this interpretation, with inferred TN ca. 1900 around 60 μmol l⁻¹, and an increase in TN concentration over the past century to ca. 130 μmol l⁻¹ by 1995. Inferred TN decreased to ca. 100 μmol l⁻¹ by 2001, similar to present day monitoring data.     

Aptian to Coniacian (Early–Late Cretaceous) palynostratigraphy of the Gustav Group, James Ross Basin, Antarctica

The Gustav Group of the James Ross Basin, Antarctic Peninsula, forms part of a major Southern Hemisphere Cretaceous reference section. Palynological data, chiefly from dinoflagellate cysts, integrated with macrofaunal evidence and strontium isotope stratigraphy, indicate that the Gustav Group, which is approximately 2.6 km thick, is Aptian–Coniacian in age. Aptian–Coniacian palynofloras in the James Ross Basin closely resemble coeval associations from Australia and New Zealand, and Australian palynological zonation schemes are applicable to the Gustav Group. The lowermost units, the coeval Pedersen and Lagrelius Point formations, have both yielded early Aptian dinoflagellate cysts. Because the overlying Kotick Point Formation is of early to mid Albian age, the Aptian/Albian boundary is placed, questionably, at the Lagrelius Point Formation–Kotick Point Formation boundary on James Ross Island, and this transition may be unconformable. Although the Kotick Point Formation is largely early Albian on dinoflagellate cyst evidence, the uppermost part of the formation appears to be of mid Albian age. This differentiation of the early and mid Albian has refined the age of the formation, previously considered to be Aptian–Albian, based on macrofaunal evidence. The Whisky Bay Formation is of late Albian to latest Turonian age on dinoflagellate cyst evidence and this supports the macrofaunal ages. Late Albian palynofloras have been recorded from the Gin Cove, lower Tumbledown Cliffs, Bibby Point and the lower–middle Lewis Hill members. However, the Cenomanian age of the upper Tumbledown Cliffs and Rum Cove members, based on molluscan evidence, is not supported by the dinoflagellate cyst floras and further work is required on this succession. The uppermost part of the Whisky Bay Formation in north-west James Ross Island is of mid to late Turonian age and this is confirmed by strontium isotope stratigraphy. The uppermost unit, the Hidden Lake Formation, is Coniacian in age on both palaeontological and strontium isotope evidence. The uppermost part of the formation appears to be early Santonian based on dinoflagellate cysts, but strontium isotope stratigraphy constrains this as being no younger than late Coniacian. This refined palynostratigraphy greatly improves the potential of the James Ross Basin as a major Cretaceous Southern Hemisphere reference section.     

Lithology and palynology of Neogene sediments on the narrow edge of the Kitakami Massif (basement rocks), northeast Japan: Significant change for depositional environments as a result of plate tectonics

Abstract A controversial stratigraphic section, the Taneichi Formation, is exposed along the Pacific Coast of northeastern Honshu, the main island of the Japanese Archipelago. Although most sediments of the formation have long been dated as late Cretaceous, the northern section of it has been assigned to (i) the Upper Cretaceous; (ii) the Paleogene; or (iii) the Neogene. In the present report, we present the data of palynological and sedimentological studies, showing that the northern section should be assigned to the Neogene. A more important point in the present study is that we invoke some basic principles of fluvial sedimentology to resolve this stratigraphic subject. The lignite layers full of Paleogene–Miocene dinoflagellate cysts and pollen assemblages drape over the boulder‐sized (>40 cm in diameter) clasts in the northern section. However, the layers totally consist of aggregates of small lignite chips, indicating that the lignites are allochthonous materials. The mega‐clasts with derived microfossils in the lignites are thought to have been deposited as Neogene fluvial (flood) sediments in the newly formed Japanese Archipelago. Prior to the Miocene, the northern Honshu was part of the Eurasian Plate, thus the boulder‐sized clasts cannot be envisaged as long river flood deposits along the continental Paleogene Pacific Coast. Instead, the mega‐clasts with the draping lignites were probably derived from nearby Miocene highlands in the newly born island arc.     

牡蛎对浮游植物群落下行控制作用的围隔实验研究

牡蛎的滤食作用不但能控制浮游植物丰度，还能通过摄食选择性影响群落结构。通过在较高营养水体的围隔实验表明，牡蛎养殖在持续磷限制条件下，促使浮游植物群落由甲藻向小型硅藻优势转变。实验结束时对照组中浮游植物群落由扁压原甲藻主导，占总丰度的77%；而牡蛎养殖组新月柱鞘藻丰度占比达到93%。牡蛎养殖组中，甲藻去除速率随养殖密度增长，但是硅藻最终丰度在高密度牡蛎组最高。研究结果说明大量的贝类养殖能够提升小型链状硅藻的优势度，增加此类赤潮发生风险。     

Organic-walled dinoflagellate cyst records from a prospective Turonian – Coniacian (Upper Cretaceous) GSSP,Słupia Nadbrzeżna,Poland

A river section at Słupia Nadbrzeżna, central Poland, has been proposed as a candidate Turonian – Coniacian (Cretaceous) GSSP, in combination with the Salzgitter-Salder quarry section of Lower Saxony, Germany. Results of a high-resolution (25 cm) palynological study of the boundary interval in the Słupia Nadbrzeżna section are presented. Terrestrial palynomorphs are rare; marine organic-walled dinoflagellate cysts dominate the palynological assemblage. The dinoflagellate cyst assemblage has a low species richness (5–11 per sample; total of 18 species recorded) and diversity (Shannon index H = 0.8–1.4), dominated by four taxa: Circulodinium distinctum subsp. distinctum; Oligosphaeridium complex; Spiniferites ramosus subsp. ramosus; Surculosphaeridium longifurcatum. Declining proportions of O. complex and S. ramosus subsp. ramosus characterise the uppermost Turonian, with an increased dominance of S. longifurcatum in the lower Coniacian. The Turonian – Coniacian boundary interval includes an acme of C. distinctum subsp. distinctum in the upper Mytiloides scupini Zone, a dinoflagellate cyst abundance maximum in the Cremnoceramus walterdorfensis walterdorfensis Zone, and the highest occurrence of Senoniasphaera turonica in the basal Coniacian lower Cremnoceramus deformis erectus Zone. Most previously reported Turonian – Coniacian boundary dinoflagellate cyst marker species are absent; a shallow-water oligotrophic epicontinental depositional setting, remote from terrestrial influence, likely limited species diversity and excluded many taxa of biostratigraphic value.