Replacement of large copepods by small ones with eutrophication of embayments: cause and consequence

Species and size compositions of the planktonic copepod community were compared between two eutrophic embayments, Tokyo Bay and Osaka Bay. Within these bays, the median body weight of the community was lowest at the innermost station and increased gradually offshore. In Tokyo Bay, which is more eutrophic than Osaka Bay, the dominant species was Oithona davisae and the median carbon weight of the community was ca 0.1 µg. In Osaka Bay, Paracalanus sp., Calanus sinicus and Corycaeus spp. were dominant and the median weight was 1–2 order of magnitude higher (2–78 µg) than in Tokyo Bay. Some 40 years ago, when eutrophication was less prominent, Acartia omorii, Paracalanus sp. and Microsetella norvegica comprised a considerable portion of the community in Tokyo Bay. The proliferation of O. davisae might have been caused with the recent change in food particle composition and/or dissociated life cycle of this species from the benthic anoxic layer. Decrease in the size composition of the copepod community may make the embayment ecosystem unfavorable for planktivorous fish, but not for jellyfish, e.g. Aurelia and Bolinopsis. This may also result in an acceleration of the flux of biogenic materials from the embayment to the outer ocean.     

Effect of seasonal hypoxia on the benthic foraminiferal community of the Louisiana inner continental shelf: The 20th century record

A species census in sediment core samples reveals significant changes in the composition of the Louisiana-shelf benthic foraminiferal community in the past century; these changes can be explained by an increase in the severity of seasonal hypoxia in bottom waters. Agglutinated and porcelaneous orders living in water depths less than 60 m suffered a noticeable decline during this time. In particular, the genus Quinqueloculina was severely affected by the progression of hypoxia, and nearly disappeared from parts of the study area. In contrast, several hyaline taxa, especially Nonionella basiloba, Buliminella morgani, and Epistominella vitrea, tolerated the progressive oxygen depletion well. Results of cluster and principal components analyses of the foraminiferal assemblage data match the observed species distribution trends and indicate that seasonal hypoxia on the Louisiana shelf, related to eutrophication and water stratification, worsened in the past century, even near the outer edge of the present-day zone of spring and summer oxygen depletion. The temporal trends in the foraminiferal record correspond to that of fertilizer use in the U.S. and nitrogen loading in the Mississippi River, suggesting that the anthropogenic factor has been particularly strong in the development of coastal hypoxia since the early 1940s.     

Development of modern benthic ecosystems in eutrophic coastal oceans: The foraminiferal record over the last 200 years,Osaka Bay,Japan

The ecosystem dynamics of a modern benthic community in Osaka Bay was studied by analyzing sediment cores and fossil foraminifera deposited during the past 200 years. The results suggest that the high-density/low-diversity assemblage has appeared in the early 1900s, coinciding with the eutrophication of the bay resulting from the Japanese industrial revolution. This assemblage proliferated during the period 1960 to 1970 when the eutrophication and bottom-water hypoxia were most pronounced. The development of the assemblage has been characterized by an increase in the relative and absolute abundance of eutrophication-tolerant species (Ammonia beccarii, Eggerella advena, and Trochammina hadai) and a decrease in many other foraminiferal species, such as Ammonia tepida, Elphidium, Miliolinella subrotunda, and Valvulineria hamanakoensis, that are unable to tolerate low-oxygen conditions. Approximately thirty years after the imposition of discharge restrictions in the 1970s, this assemblage continues to predominate in the inner part of the bay, and E. advena is currently found across the entire bay. These records make a significant contribution to understanding the long-term relationship between anthropogenic impact and ecosystem change.     

渤海莱州湾表层沉积物中底栖有孔虫分布特征及其环境意义

对渤海莱州湾海域240个站位表层沉积物中底栖有孔虫群落进行了分析,共鉴定常见的底栖有孔虫42种。结果表明,莱州湾表层沉积物中底栖有孔虫主要以玻璃质壳为主(平均丰度达70.9%),瓷质壳含量次之,胶结壳含量最低;玻璃质壳占有孔虫全群的百分含量,随水深的增加而增加;从黄河口向外海方向,有孔虫分异度和丰度都逐渐增大。该海域底栖有孔虫平面分布的主要控制因素为盐度和底质沉积物类型,大体可分为两个组合分区,I区为Ammonia beccarii-Quinqueloculina spp.组合,代表盐度较低的近岸海陆过渡浅水环境;II区为Cribrononionsub-incertum-Protelphidium tuberculatum组合,代表盐度较高的远岸内陆架环境。     

The relative influence of hypoxia, anoxia, andassociated environmental factors as determinants ofmacrobenthic community structure in aNorthern Gulf of Mexico estuary

Seasonal patterns (i.e., December 1986, and April and October 1987) in benthic macroinfaunal abundance,distribution, and taxa composition at 19 sites in Perdido Bay, AL/FL, are evaluated to assess the relative importance of environmental factors as determinants of community structure. A total of 46 taxa from five phyla were collected with diver-held bottom corers. Polychaetes were numerically dominant followed by crustaceans. Seventeen taxa co-occurred in samples during all three study periods. Maximum animal densities and taxa richness showed no statistically significant bay-wide seasonal pattern,however, a bay-wide trend was detected where these response parameters tended to be greater in April than December or October. Deeper upper bay stations were depauperate during December and October. Low dissolved oxygen (DO) largely explained the depauperate pattern. Mean taxa richness per core(10 cm dia.) ranged from 0.0 to 5.0, 1.2 to 4.6, and0.0 to 4.4 in December, April and October,respectively. Mean densities ranged from zero to 368,0 to 960, and 0 to 430 individuals per 0.1 m² in December, April, and October, respectively. Results of a three-season statistical regression model indicated that DO deficiency was a primary determinant of taxa richness (partial R ²: 0.27) but was less important in explaining animal densities (partialR ²: 0.16). For December, when additional environmental variables were measured, DO was supplanted by weight loss on ignition (R ²: 0.24)and the sediment C:N ratio (R ²: 0.44) as highest explanatory factors for taxa richness and density,respectively. Application of a benthic index of environmental condition indicated wide-spread ecological stress on the benthic macroinfaunal assemblages. This revised version was published online in July 2006 with corrections to the Cover Date.     

Paleoceanographic implications of smaller benthic and planktonic foraminifera from the Eocene Pazin Basin (Coastal Dinarides,Croatia)

Summary Smaller benthic and planktonic foraminifera from the clastic sediments of the Pazin Basin (Istria, Croatia) were studied in order to obtain more data about paleoceanographic conditions that existed in the Middle Eocene Dinaric foreland basin. The succession investigated corresponds to the Middle Eocene planktonic foraminiferal zones Globigerapsis kugleri/Morozovella aragonensis (P11), Morozovella lehneri (P12), and Globigerapsis beckmanni (P13). Benthic foraminiferal assemblages from the clastic succession are dominated by epifaunal trochospiral genera suggesting oligotrophic to mesotrophic conditions and moderately oxygenated bottom waters. Planktonic foraminiferal assemblages indicate mesotrophic to eutrophic conditions of the surface waters, with increased eutrophication in the upper part of the section. Water depth, based on the ratio between planktonic and epifaunal benthic foraminifera and on the recognized species of cosmopolitan benthic foraminifera, was estimated to have been between about 900 and 1200 m. The basin was elongated and open to marine currents on both sides allowing good circulation and ventilation of the bottom water.     

南黄海近岸底栖有孔虫分布与环境因子转换函数的建立

本文对南黄海西北陆架边缘的300个表层沉积物样品中的底栖有孔虫数据,与相应站位的水深、底层水温、盐度、沉积物粒度、有机碳含量等环境参数作了分析研究。除趋势对应分析(DCA)、典型对应分析(CCA)表明有孔虫种群分布与水深、夏季底层水温(Ts)和冬季底层水盐度(Sw)之间存在着显著的数值对应关系。利用加权平均偏最小二乘回归方法(WA-PLS)建立了底栖有孔虫数据与上述环境因子之间的数值转换函数。水深、Ts与Sw转换函数的预测均方根误差(RMSEP)分别是10.8%、11.5%和12.5%,与利用其他指标建立的此类转换函数水平(8%—20%)相当。利用此类统计建模方法建立近岸底栖有孔虫分布与浅海环境因子之间的数值关系是一项新的尝试,结果表明在我国近海底层水体古环境研究中底栖有孔虫转换函数是一种具有一定潜力的研究方法。     

Ammonia beccarii and Ammonia tepida (Foraminifera): morphofunctional arguments for their distinction

New observations from Yeu Island and the Bay of Bourgneuf on the Atlantic coast of France show that Ammonia beccarii s.s. and Ammonia tepida have different morphofunctional adaptations to their habitats and environments. Adult A. beccarii s.s. may be epiphytic, living on the calcareous alga Corallina officinalis or on the red alga Gigartina acicularis along rocky shores, while A. tepida is endopelic, living in sediments of brackish environments. Rapid 3-D emission of pseudopodia from interlocular spaces on both umbilical and spiral sides of adult A. beccarii s.s. can support its test within the seaweed framework. This behaviour is characteristic of phytal species. Thus, it appears that the major difference between A. beccarii s.s. and A. tepida is the presence of large interlocular spaces on spiral side of the former, corresponding to a potential morphofunctional adaptation to the epiphytic mode of life. We believe that these observations could help to solve the long-lasting A. beccarii problems of specific distinction.     

The chemical environment of tubificid and lumbriculid worms according to the pollution level of the sediment

In Lake Geneva (Switzerland), 14 tubificid and 2 lumbriculid worm species were collected in a total of 170 samples of sediment. The sediment was analysed through ten chemical variables: organic carbon, total phosphorus, Cd, Zn, Sn, Pb, Hg, Cu, Cr, Mn. The chemical environment characterizing the presence of every worm species was defined by the mean value of each of these ten variables in all samples where the species was found. The multivariate comparison of the chemical environment typical of every species enabled six groups of species to be distinguished, each characterized by the high value of one chemical variable: (1) Peloscolex ferox, Potamothrix hammoniensis, Limnodrilus claparedeanus, and Cd. (2) Psammoryctides barbatus, and Zn. (3) Limnodrilus hofmeisteri, L. udekemianus, L. profundicola, and total P. (4) Potamothrix heuscheri, Aulodriluspluriseta, A. limnobius, Tubifex tubifex, Ilyodrilus templetoni, Stylodrilus heringianus, and organic C. (5) Potamothrixvejdovskyi, and, Hg. (6) Peloscolex velutinus, Stylodrilus lemani, and Mn. Pollution level of the sediment decreased from group 1 to 6, so each of these groups may be used to define a different level of pollution. The pooled coefficient of variation of the ten chemical variables used to define the chemical environment of each species diminished from group 1 to 6: the most opportunistic species colonized the most polluted areas.     

厦门西港现代底栖有孔虫一新属

记述了产于厦门西港海域现代底栖有孔虫的１个新属－－似异形虫属Ａｅｏｌｏｍｏｒ ｐｈｅｌｌｏｉｄｅｓ ｇｅｎ．ｎｏｖ．及１个新种Ａｅｏｌｏｍｏｒｐｈｅｌｌｏｉｄｅｓ ｘｉａｍｅｎｅｎｓｉｓ ｇｅｎ．ｅｔ ｓｐ． ｎｏｖ．。     

Ocean acidification induces biochemical and morphological changes in the calcification process of large benthic foraminifera

Large benthic foraminifera are significant contributors to sediment formation on coral reefs, yet they are vulnerable to ocean acidification. Here, we assessed the biochemical and morphological impacts of acidification on the calcification of Amphistegina lessonii and Marginopora vertebralis exposed to different pH conditions. We measured growth rates (surface area and buoyant weight) and Ca-ATPase and Mg-ATPase activities and calculated shell density using micro-computer tomography images. In A. lessonii, we detected a significant decrease in buoyant weight, a reduction in the density of inner skeletal chambers, and an increase of Ca-ATPase and Mg-ATPase activities at pH 7.6 when compared with ambient conditions of pH 8.1. By contrast, M. vertebralis showed an inhibition in Mg-ATPase activity under lowered pH, with growth rate and skeletal density remaining constant. While M. vertebralis is considered to be more sensitive than A. lessonii owing to its high-Mg-calcite skeleton, it appears to be less affected by changes in pH, based on the parameters assessed in this study. We suggest difference in biochemical pathways of calcification as the main factor influencing response to changes in pH levels, and that A. lessonii and M. vertebralis have the ability to regulate biochemical functions to cope with short-term increases in acidity.     

Habitat variables determining the occurrence of large benthic foraminifera in the Berau area (East Kalimantan, Indonesia)

Knowledge of the assemblage composition of large benthic foraminifera (LBF) in relation to environmental conditions is needed to interpret fossil records. In this study the assemblage composition of LBF is described for a carbonate shelf with a barrier reef system and some reefs outside the barrier. In a total of 140 samples, 34–35 species of LBF were found. Four clusters, roughly corresponding to substrate type were identified. Several small groups of samples were recognized that were collected locally inside, on, or outside the barrier. Microscale environmental gradients within the substrate or in the benthic boundary layer resulted in spatial differentiation of the microhabitat of each species.     

Recent benthic foraminiferal assemblages in deep high-energy environments from the Gulf of Cadiz (Spain)

The benthic environment in the Gulf of Cadiz, north-eastern Atlantic, is strongly affected by the Mediterranean outflow water undercurrent (MOW) which flows northwards along the western Iberian Margin at 500–1500 m water depth. Foraminiferal census counts of living and dead assemblages from 27 surface samples ranging from 103 to 1917 m water depth, and the examination of hard substrates reveal a close correlation of the fauna with the local hydrography and sediment facies. Four different faunal groups are separated by factor analysis of the living fauna. Assemblage 1 contains typical lower slope species and dominates samples from the lower MOW core layer and in the North Atlantic deep water below. Shelf edge foraminifera are common in assemblage 2a which shows the highest proportions in samples from 103 to 272 m. Assemblage 2b is dominated by upper slope species and suspension-feeders that are frequent in the upper MOW core layer and in distal settings between 396 and 901 m. Species from assemblage 3 prefer epibenthic habitats and are recorded with high proportions exclusively in the immediate flow paths of the upper MOW between 496 and 881 m. Colonisation structures and species composition of epibenthic assemblages from the proximal facies largely differ from those in distal settings. In general, epibenthic foraminifers only use elevated substrates under the influence of near-bottom flow. Under high current velocities, epibenthic foraminifers prefer large and heavy objects. They colonise high attachment levels where a maximum yield of advected food particles can be achieved. In distal settings at lower flow velocities, the elevation height does not exceed 20 mm above the surrounding sediment surface. This level is related to a hydrologic transition layer with high concentrations of suspended particles. The comparison of microhabitat preferences and faunal structure under high and low current velocities reveal that substrate stability may be a confining environmental variable for endobenthic and shallow epibenthic foraminifers. The observations also indicate that the preferential settling height of epibenthic foraminifera is related to the highest lateral flux rates of food particles within reach from the sea floor. A dynamic selection of elevated microhabitats is only used by 7.8% of all species recognised in the Gulf of Cadiz area.     

Integrated magnetobiochronology of the Early/Middle Eocene transition at Agost (Spain): Implications for defining the Ypresian/Lutetian boundary stratotype

In this paper, we present an integrated study of a 115‐m‐thick section that spans the Ypresian/Lutetian boundary at Agost (Betic Cordillera, SE Spain). Our study includes magnetostratigraphic results and biostratigraphic and palaeoenvironmental data derived from planktic foraminifera, small and larger benthic foraminifera, and calcareous nannofossils. Our results demonstrate that the Agost section is continuous and spans from Zones P9 to P12 (E7 to E10), Zones CP11 to CP14a (NP13 to NP16), Zones SBZ11 to SBZ15, and Chrons C22n to C19r. The first occurrence (FO) of H. nuttalli (base of P10) and the FO of G. nuttalli (base of E8) are found within Chron C20r, at a much younger age (3–5 Myr) than previously considered in standard calibration schemes. Similarly, the boundary between SBZ12 and SBZ13 is located within Chron C21n, also at a younger age than previously considered. On the contrary, the FO of B. inflatus (base of CP12b) is found within Chron C21r, which conforms to the magnetostratigraphically calibrated age of ca. 48 Ma (middle part of C21r) considered in standard calibration schemes. These results corroborate earlier studies and indicate that all the events that have been proposed to mark the Ypresian/Lutetian boundary appear at different stratigraphic intervals and have different ages. Based on our results from Agost and on data from other sections elsewhere, we suggest that the Ypresian/Lutetian boundary might be approximated by the FO of B. inflatus (base of CP12b). The Agost section might be considered as a potential candidate to locate the Global Stratotype Section and Point (GSSP) of the base of the Lutetian Stage, because it includes all the events that might be selected as marker events for the Ypresian/Lutetian boundary and it fulfils most of the geological, biostratigraphic and infrastructure requirements demanded for definition of a GSSP.     

Palaeoenvironments of deposition of Neogene laminated diatom mat deposits from the eastern equatorial Pacific from studies of benthic foraminifera (sites 844, 849, 851)

Massive sedimentation of mats of the diatom Thalassiothrix longissima forming laminated diatom mat deposits (LDM) occurred intermittently in the equatorial Pacific throughout the Neogene from at least 15 to 4.8 m.y. ago. The background deposition was otherwise calcareous nannofossil diatom ooze (NO). Benthic foraminifera have been used to reconstruct the benthic environment of deposition and the role of both surface waters (as a source of food) and bottom waters (including their corrosivity) during LDM deposition. Three LDM events were studied: Site 844 (11.4 Ma, early Tortonian), Site 849 (4.8 Ma, early Zanclian and 6.6–6.8 Ma, early Messinian). A control section of NO spanning the 4.8 Ma event was studied from Site 851. In addition, the carbonate high NO immediately preceding the 4.8 Ma event was examined in Site 849. From the foraminiferal evidence it can be shown that the LDM was deposited under conditions of normal oxygenation because infaunal taxa are present throughout and there was an increase in epifaunal taxa such as Cibicides spp. However, there was a reduction in test size probably because only those smaller than 250 μm were able to move through the restricted sediment pore spaces caused by the diatom mat meshwork. The rate of accumulation of tests is highest in LDM interval and may reflect reduced predation from macrofaunal endobenthos. Among the epifaunal taxa, Nuttallides spp. show a decrease in abundance in the LDM and even immediately preceding it. This may be linked to a greater influence of corrosive AABW. Species known to feed opportunistically on phytodetritus (Epistominella exigua and Alabaminella weddellensis) are common in both NO and LDM. The increased relative abundance of A. weddellensis in the LDM may be due to this species being smaller than E. exigua and better able to exploit the food resource within the restrictive mat meshwork. The foraminiferal results corroborate the previous interpretation that preservation of lamination in the LDM is due to the physical exclusion of macro endobenthos rather than oxygen depletion of the bottom waters.     

The benthic foraminiferal communities of the northern Adriatic continental shelf

Off the Po Delta in the northern Adriatic, three different foraminiferal associations were identified in the fraction >0.125 mm of 25 sediment samples. The first association concerns sample stations between depths of 5 and 13.5 m in the shallow, nutrient-rich belt and is characterised by dominant Ammonia beccarii. The second occupies the 29.5–38.5-m-deep, nutrient-rich zone of clay-rich sediment, where inputs from the Po are concentrated, and is dominated by Nonionella opima. The third association, in the 21–46-m-deep and nutrient-poor zone, is dominated by Textularia agglutinans. The same distribution of communities was obtained using total associations (living and dead specimens) and biocenosis (stained individuals). The good correspondence with the foraminiferal distributions described in the past indicates that, in spite of the occurrence of anoxic and dysoxic events, the environmental state in the northern Adriatic may be considered stable.