The fauna of benthic sediments from the organically enriched Oslofjord,Norway

The macrobenthic fauna of the organically enriched Oslofjord was sampled in Sept.–Nov. 1977. Seventy-six stations were sampled using a stratified random plan. A total of 146 species were identified, dominated by polychaetes, molluscs and echinoderms. The faunal data were analysed by a variety of methods including diversity indices, log-normal distribution of individuals among species, factor analysis and numerical classification. The primary aim was the detection of pollution-induced disturbance and to delimit the extent of pollution on the benthic fauna of Oslofjord. All of the methods used showed a gradient from heavy pollution at the innermost part of the fjord where few species occurred, together with high dominance and low diversity, to normal unpolluted conditions at the Drøbak sill with high species diversity. From the classification analysis a combination of both site and species data revealed a trend in species groupings which were broadly similar to data from other Scandinavian fjords and from Scotland. Hydrographical and biological data taken at the turn of the century and in the 1960's compared with the present data show declining conditions in Oslofjord, due primarily to organic enrichment combined with a naturally poor water exchange which leads to stagnation of the water mass.     

Survival,ATP pool,and ultrastructural characterization of benthic foraminifera from Drammensfjord (Norway): response to anoxia

While much evidence indicates that certain benthic foraminifera are facultative anaerobes, little is known regarding the physiologic response of foraminifera to anoxia. In order to assess their response, specimens of four foraminiferal species, collected from a typically dysoxic area of Drammensfjord, Norway (45 m water depth), were incubated in seawater purged with nitrogen. Over a time course of > 3 weeks, the specimens were extracted for adenosine triphosphate (ATP) in a nitrogen-flushed glove bag to assess their survival and ATP reserve under such conditions. For comparative purposes, similar extractions were done on conspecifics one week after their collection from the seafloor, as well as on other conspecifics, obtained from the same site, incubated in aerated conditions. The survival rates of nitrogen-treatedAdercotryma glomeratum, Psammosphaera bowmanni, and Stainforthia fusiformis were not significantly lower than those of the control specimens. However, the ATP concentrations of nitrogen-incubated A. glomeratum and S. fusiformis were significantly lower than those of their aerated conspecifics, while there was no significant difference between the [ATP] of P. bowmanni from the two treatments. Both the survival rate and the ATP concentrations of nitrogen-incubated Bulimina marginata were significantly lower than those of control specimens. The ultrastructure of B. marginata and S. fusiformis incubated in N₂ for 18 days were compared with those of specimens fixed within 15 minutes of collection. For both species, the specimens that survived the experimental treatment had ultrastructures indistinguishable from those fixed just after field collection. However, the ultrastructure of B. marginata differed from that of S. fusiformis in that it lacked the numerous peroxisome-endoplasmic reticulum (ER) complexes and what appeared to be algal chloroplasts observed in S. fusiformis. Copious arrays of paracrystals were observed in both species from the experimental treatment as well as the shipboard-fixed specimens, suggesting that neither population had extensive pseudopodial networks. When considered in combination, our results indicate that the four species respond to and survive anoxia differently, with responses including dormancy and, as yet unidentified, anaerobic metabolic pathways.     

The Foram Stress Index: A new tool for environmental assessment of soft-bottom environments using benthic foraminifera. A case study from the Saronikos Gulf,Greece, Eastern Mediterranean

Saronikos Gulf, including the industrial zone of Elefsis Bay and the Port of Piraeus, is one of the most anthropogenically impacted coastal regions of Greece. Distinct assemblages of benthic foraminifers in sediment samples, collected from this gulf in February 2012, defined three zones that reflect abiotic parameters of the sediments (e.g., organic carbon, metal content). A low-diversity assemblage, dominated by stress-tolerant Ammonia tepida and Bulimina spp., was characteristic of samples from Elefsis Bay. Samples from the western and central part of Saronikos Gulf were the most variable with respect to both abiotic parameters and the foraminiferal assemblage, characterized by a mix of stress-tolerant and more sensitive taxa, especially Bolivina spp. and Nonion fabum. Samples from the coast of Salamis and at the eastern sector of the gulf were characterized by a diverse assemblage that included Peneroplis pertusus, miliolids, and a variety of small, epiphytic rotaliid taxa. A new biotic index, the Foram Stress Index (FSI), is based on the relative percentages of two ecological groups of benthic foraminiferal species, grouped according to their tolerance/sensitivity to organic matter enrichment and weighted proportionately to obtain a formula to define five ecological-status classes. The FSI produced three rankings for these samples (Poor, Moderate and Good), that strongly correlate with the macroinvertebrate-classification tool known as the BENTIX Index. The FSI provides a new tool to assess sediment or substrata quality based upon the benthic foraminiferal assemblages, which are a significant component of living meiobenthic communities that are generally not considered in most biotic benthic indices.     

Pliocene benthic foraminifera from the Blake Plateau: Faunal assemblages and paleocirculation

Relative abundance of benthic foraminifera have been analyzed from core V26-145 from the Blake Plateau. The investigated sequence represents the time interval between 1.8 and 4.6 Ma. In order to determine how different sieve sizes influence the relative abundance patterns, three sediment size fractions were studied separately. It becomes difficult to maintain consistent taxonomic concepts in the fraction 63–125 μm, partly because this fraction contains high abundances of juvenile forms. However, the 63–125 μm fraction holds high abundances of the important small speciesEpistominella exigua. Due to these reasons only the two larger fractions (125–250 μm and >250 μm) were considered meaningful to analyze for relative abundance patterns. An analysis of the two larger fractions (>125 μm; >250 μm) shows no consistency in relative abundance patterns.The relative abundance patterns for the 34 most common species in the size fraction >125 μm were analyzed by means of correspondence analysis. Three benthic foraminiferal assemblages (I, II, and III) were recognized and these can be associated with water masses. Assemblage I is associated with the Florida Current and consists of shallow water species (Amphistegina gibbosa, Compressigerina sp. A,Discorbinella biconcavus, Islandiella teretis, Reussella atlantica, andSiphonina pulchra). Assemblage II contains key species for North Atlantic Deep Water (NADW) (Cibicidoides kullenbergi, Epistominella exigua, Globocassidulina subglobosa, Lenticulina peregrina, Oridorsalis umbonatus, andPlanulina wuellerstorfi). The third assemblage (III) contains species associated with the Antilles Current (Bolivina rhomboidalis, Cassidulina obtusa, Cassidulina vortex, andNuttallides umbonifera). The correspondence analysis reveals an alternation in dominance between Assemblage I and Assemblage II prior to 3.3 Ma, suggesting lateral oscillations between the Florida Current and NADW. At about 3.3 Ma Assemblage I disappears and Assemblage III increases in importance, suggesting an increasing influence of the Antilles Current in the upper part of the record.     

A benthic perspective in assessing the ecological status of estuaries: The case of the Mondego estuary (Portugal)

In transitional waters the process of defining reference conditions (in the scope of the WFD) must account for the natural great variability of such environments. Therefore, stretches reflecting different physical–chemical and biological conditions throughout the system should be defined in order to correctly establish benthic specific reference conditions. Both salinity and sediment structure are major factors controlling physical–chemical conditions and therefore organisms’ distribution within an estuary. These environmental variables (salinity, sediment grain size composition and organic matter content) patterns were studied in the Mondego estuary and some clear gradients emerged. Also, ecological indices (AMBI, Margalef and Shannon-Wiener) were applied to subtidal benthic communities of the Mondego estuary and, generally, there was not only evidence of a decrease in diversity in the estuary from the downstream section towards its inner parts, but also differences were found between areas of distinct sediment composition. After comparing environmental patterns with biodiversity trends, the information was used to define homogeneous sectors along a temperate estuary in Portugal. In the Mondego estuary six zones, covering the main physical gradients affecting benthic communities, were defined: four in the northern arm and two in southern arm. Zones established will allow future determination of benthic reference conditions adjusted for each of the sectors, according to their characteristics, and consequently the conditions they provide for benthic assemblages settlement.     

Benthic foraminifera and trace metal distribution: a case study from the Burullus Lagoon,Egypt

Benthic foraminifera are widely used to detect the health of their habitat, where they are very sensitive to even slight variations in the ecosystem. Therefore, the main objectives of this study are to examine the benthic foraminiferal assemblages in the sediments of Burullus Lagoon, evaluate the pollution levels and deduce the impact of trace metals on foraminifera. The continuous discharge of trace metals from agricultural, industrial and domestic sources into the lagoon may lead to a severe environmental problem. The concentrations of Mn, Cu, Cd, Zn and Pb within the sediments were measured. Recently, the assessment of contamination is principally based on the contamination indices which provide fast and simple quantitative values on the degree of pollution in a given aquatic environment. Thus, some indices, including the contamination factor, the degree of contamination, pollution load index, geoaccumulation index, ecological risk factor and potential ecological risk index are applied in this investigation. Based on the contamination factors, the sediments are very highly contaminated with Cd, considerably to very highly contaminated with Cu and Zn, moderately contaminated with Mn, low to moderately contaminated with Pb. All sites display very high values for the degree of contamination. Moreover, the values of the pollution load index are higher than 1, indicating that the lagoon is polluted. Depending on the geoaccumulation index, the contaminants are arranged as follows Cd > Zn > Cu > Mn > Pb. It is clear that Cd is the main contributor to the ecological risk factor in Burullus Lagoon. Concerning the richness of the foraminiferal assemblages, it fluctuates between 1–5 species per sample. Because of its higher tolerance to extreme conditions (changes in salinity and pollution), Ammonia tepida is the most abundant species. The occurrence of rare living individuals (25) is restricted only to sites close to El-Boughaz Inlet where higher salinity and lower levels of pollution are recorded. The same trend of distribution is shown by Cribroelphidium excavatum and miliolids, where they occur at sites with higher salinities. The occurrence of test deformities in all the studied sites may be related to the response of benthic foraminifera to trace metal. The forms of deformation include spiroconvex, reduced chambers, twisted tests, twinning, additional chamber and complex forms. The deformation depends on the nature of pollutants. Twinning and reduced chambers are the most dominant forms in areas close to the agricultural drainage (southern drains), while complex forms are abundant in areas close to industrial drainage (El-Gharbia drain). Thus, salinity and pollution may be the most regulatory factors controlling the distribution of foraminifera. This investigation confirmed the role of benthic foraminifera as a good ecological indicator in Burullus Lagoon.     

Spatial and temporal variation in reef-scale carbonate storage of large benthic foraminifera: a case study on One Tree Reef

Large benthic foraminifera (LBFs) are a vital component of coral reef carbonate production, often overlooked due to their small size. These super-abundant calcifiers are crucial to reef calcification by generation of lagoon and beach sands. Reef-scale carbonate production by LBFs is not well understood, and seasonal fluctuations in this important process are largely unquantified. The biomass of five LBF species in their algal flat habitat was quantified in the austral winter (July 2013), spring (October 2013), and summer (February 2014) at One Tree Reef. WorldView-2 satellite images were used to characterize and create LBF habitat maps based on ground-referenced photographs of algal cover. Habitat maps and LBF biomass measurements were combined to estimate carbonate storage across the entire reef flat. Total carbonate storage of LBFs on the reef flat ranged from 270 tonnes (winter) to 380 tonnes (summer). Satellite images indicate that the habitat area used by LBFs ranged from 0.6 (winter) to 0.71 km² (spring) of a total possible area of 0.96 km². LBF biomass was highest in the winter when algal habitat area was lowest, but total carbonate storage was the highest in the summer, when algal habitat area was intermediate. Our data suggest that biomass measurements alone do not capture total abundance of LBF populations (carbonate storage), as the area of available habitat is variable. These results suggest LBF carbonate production studies that measure biomass in discrete locations and single time points fail to capture accurate reef-scale production by not incorporating estimates of the associated algal habitat. Reef-scale measurements in this study can be incorporated into carbonate production models to determine the role of LBFs in sedimentary landforms (lagoons, beaches, etc.). Based on previous models of entire reef metabolism, our estimates indicate that LBFs contribute approximately 3.9–5.4% of reef carbonate budgets, a previously underappreciated carbon sink.

     

Ecological status assessment in mediterranean rivers: complexities and challenges in developing tools for assessing ecological status and defining reference conditions

Rivers in mediterranean regions are subject to hydrological extremes. They range from highly stable, perennial ground- or snow-fed systems to highly ephemeral, unpredictable ones in semi-arid environments. Spatial and temporal complexity inherent in these systems presents challenges for ecological status assessment and defining reference conditions, particularly as many areas have been extensively transformed through anthropogenic activities. Temporal variability driven by sequential and predictable, seasonal events of flooding and drying accentuates the need to take season and/or hydrological period into account. Intermittent streams, which are common in mediterranean regions (med-regions) and which have aquatic communities distinct from perennial streams, are often not incorporated in bioassessment and present distinct challenges. Med-regions are also known for their high biodiversity and rates of endemism, as well as large numbers of introduced species. Med-regions are expected to be among the most affected by global climate change and, in these systems, climate change is an additional driver influencing ecosystems that are already stressed. From this review it is evident that an understanding of responses of indices, metrics, and models to climate change in comparison to existing stresses, and the development of thermally specific bioassessment tools are needed for this region.     

Suitable sediment fraction for paleoenvironmental reconstruction and assessment of contaminated coastal areas based on benthic foraminifera: A case study from Augusta Harbour (Eastern Sicily,Italy)

Since the 1990s several studies noticed that, along coastal marine areas, the mean size of benthic foraminifera may be reduced due to heavy metal pollution, even if no biometric studies were carried out to quantify this aspect. The Augusta harbour (Sicily, Italy), is characterized by a strong contamination due to several anthropogenic activities, the most important of which are a petrochemical pole and an important industrial harbour. Taking into account the previous studies carried out in the area, which recorded small-sized foraminifera, the present study compared assemblage composition and faunal parameters in the >125 μm and >63 μm fractions of a sediment core collected in the most polluted sector of Augusta harbour. The aim was to understand if the two fractions have comparable environmental significance providing reliable information on the environmental status. In order to quantify the amount of smaller foraminifera in a community and to determine species loss between size fractions, two new indices are used: the Foraminiferal Size Index (FSI) and the Lost Species Index (LSI). Species richness, diversity and composition of the two assemblages were determined to characterize their structure. The results highlighted great depletion and different composition of the >125 μm assemblage with respect to the >63 μm one, showing a selective loss of particular ecological groups (stress-tolerant infaunal taxa). Also the better correlation of Foraminiferal Number (FN) and H’ index of >63 μm fraction with Polychlorobiphenyls (PCBs), Polycyclic Aromatic Hydrocarbons (PAHs), Barium (Ba) and Mercury (Hg), demonstrated the higher reliability of this size fraction for environmental assessment purposes.     

Recent benthic foraminifera from the continental margin of northwest Africa: Community structure and distribution

Sediment grab samples were collected at 107 locations along the continental margin of northwest Africa. These samples form a series of depth transects between the Straits of Gibraltar and Dakar, Senegal. The greater than 250 μm size fraction was retained for a census of both the live and dead foraminifera. After deleting trace occurrences, Jaccard and correlation coefficient-based cluster analyses were performed to decipher the community structure for this margin.The geographic distribution of the four major faunal provinces recognized is conventional in that for both the live and dead assemblages three are related to depth: upper slope and shelf, middle slope, and lower slope and continental rise. The biotopes and thanatotopes within these provinces are strongly restricted along vertical or latitudinal boundaries when the data are analysed using Jaccard coefficients. Dendrograms constructed from correlation coefficients emphasize depth-related faunal communities. Dominant species such asCibicides lobatulus, Trifarina fornasinii, Planulina ariminensis, Uvigerina finisterrensis, andC. wuellerstorfi are generally distributed within a definite depth range along this margin and strongly influence the correlation coefficient-based dendrograms. Other distributions are clearly not depth-related but correspond to various environmental variables, for example:Cancris auriculus — coarse substrate;Bolivina subaenariensis — oxygen minimum;Cibicidoides kullenbergi andHoeglundina elegans — low organic carbon.Uvigerina peregrina is also a notable exception to depth-dependence in that this dominant species and the province it represents are generally confined to the continental slope south of Cape Blanc. Its preference for that region may arise from the high organic carbon and fine grain-size of the sediment there, from low salinity of the bottom water, or from other unknown variables. The most important vertical faunal boundary occurs between Cape Barbas and Cape Blanc (between 22° and 21°N latitude). In contrast, the Canary Island Ridge intersects the continental margin at a saddle depth of about 1500 m, but that physiographic barrier has little effect on provincialism of the deep-water benthic foraminifera.     

Multiple deep-water sources and trophic regimes in the latest Cretaceous deep sea: evidence from benthic foraminifera

Benthic foraminifera from 24 DSDP/ODP sites were investigated to assess their global horizontal and vertical distribution in the deep-sea environment at the end of the Cretaceous period. The samples analyzed are from the late Maastrichtian and within the planktic forammiferal Abathomphalus mayaroensis Zone from a wide range of oceans and paleolatitudes, including the low-latitude Sites 10 and 384 (Atlantic Ocean), 47, 171, 305, and 465 (Pacific Ocean), the mid-latitude Sites 20, 111, 356, 363, 516, 525, 527, 548, and 605 (Atlantic Ocean), 216, 217, and 758 (Indian Ocean), and the high-latitude Sites 208 (Pacific Ocean), 689, 698, 700, 738 and 750 (Southern Ocean).Correspondence analysis, based on the 75 most common taxa, shows a clear biogeographic trend along the first correspondence axis by arranging the sites in paleolatitudinal order. The assemblages from the Tethyan Realm (i.e., low latitudes) are marked by abundant heavily calcified buliminids (such as Bulimina incisa B. trinitatensis B. velascoensis, and Reussella szajnochae) and Aragonia spp., whereas high-latitude faunas are characterized by abundant Alabamina creta, Gyroidinoides quadratus, and Pullenia coryelli.The results indicate that the faunas at low and high latitudes, respectively, were influenced by quite different environmental conditions. This is based on the much higher abundance of infaunal morphotypes at low and mid latitudes compared to high latitudes, suggesting that the biogeographic trend found in the data set coincides with the trophic regime at the various sites. The results also provide support for the hypothesis that postulates two simultaneous sources and mechanisms for deep-water formation during the Late Cretaceous, including warm, saline deep water produced by evaporation at low (equatorial) latitudes in contrast to the formation of cold deep waters at high (southern) latitudes.     

Living benthic foraminifera of the Okhotsk Sea: Faunal composition,standing stocks and microhabitats

Live (Rose Bengal stained) benthic foraminifera were investigated in surface sediment samples from the Okhotsk Sea to reveal the relationship between faunal characteristics and environmental parameters. Live benthic foraminifera were quantified in the size fraction > 125 µm in the upper 8 cm of replicate sediment cores, recovered with a multicorer at five stations along the Sakhalin margin, and at three stations on the southwestern Kamchatka slope. The stations are from water depths between 625 to 1752 m, located close or within the present Okhotsk Sea oxygen minimum zone, with oxygen levels between 0.3 and 1.5 ml l^- 1. At the high-productivity and ice-free Kamchatka stations, live benthic foraminifera are characterized by maximal standing stocks (about 1700-3700 individuals per 50 cm²), strong dominance of calcareous species (up to 87-91% of total live faunas), and maximal habitat depths (down to 5.2-6.7 cm depth). Vertical distributions of total faunal abundances exhibit a clear subsurface maximum in sediments. At the Sakhalin stations, which are seasonally ice-covered and less productive, live benthic foraminifera show lower standing stocks (about 200-1100 individuals per 50 cm²), lower abundance of calcareous species (10-64% of total live faunas), and shallower habitat depths (down to 2.5-5.4 cm depth). Faunal vertical distributions are characterized by maximum in the uppermost surface sediments. It is suggested that 1) lower and strongly seasonal organic matter flux, caused by the seasonal sea ice cover and seasonal upwelling, 2) lower bottom water oxygenation (0.3-1.1 ml l^- 1), and 3) more pronounced influence of carbonate undersaturated bottom water along the Sakhalin margin are the main factors responsible for the observed faunal differences. According to species downcore distributions and average living depths, common calcareous species were identified as preferentially shallow, intermediate and deep infaunal. Foraminiferal microhabitat occupation correlates with the organic matter flux and the depth of the oxygenated layer in sediments.     

Living benthic foraminifera of the Okhotsk Sea: Faunal composition, standing stocks and microhabitats

Live (Rose Bengal stained) benthic foraminifera were investigated in surface sediment samples from the Okhotsk Sea to reveal the relationship between faunal characteristics and environmental parameters. Live benthic foraminifera were quantified in the size fraction > 125 µm in the upper 8 cm of replicate sediment cores, recovered with a multicorer at five stations along the Sakhalin margin, and at three stations on the southwestern Kamchatka slope. The stations are from water depths between 625 to 1752 m, located close or within the present Okhotsk Sea oxygen minimum zone, with oxygen levels between 0.3 and 1.5 ml l^- 1. At the high-productivity and ice-free Kamchatka stations, live benthic foraminifera are characterized by maximal standing stocks (about 1700-3700 individuals per 50 cm²), strong dominance of calcareous species (up to 87-91% of total live faunas), and maximal habitat depths (down to 5.2-6.7 cm depth). Vertical distributions of total faunal abundances exhibit a clear subsurface maximum in sediments. At the Sakhalin stations, which are seasonally ice-covered and less productive, live benthic foraminifera show lower standing stocks (about 200-1100 individuals per 50 cm²), lower abundance of calcareous species (10-64% of total live faunas), and shallower habitat depths (down to 2.5-5.4 cm depth). Faunal vertical distributions are characterized by maximum in the uppermost surface sediments. It is suggested that 1) lower and strongly seasonal organic matter flux, caused by the seasonal sea ice cover and seasonal upwelling, 2) lower bottom water oxygenation (0.3-1.1 ml l^- 1), and 3) more pronounced influence of carbonate undersaturated bottom water along the Sakhalin margin are the main factors responsible for the observed faunal differences. According to species downcore distributions and average living depths, common calcareous species were identified as preferentially shallow, intermediate and deep infaunal. Foraminiferal microhabitat occupation correlates with the organic matter flux and the depth of the oxygenated layer in sediments.     

Magnesium and strontium compositions of Recent benthic foraminifera from the Coral Sea, Australia and Prydz Bay, Antarctica

Analyses of the Mg/Ca and Sr/Ca ratios of the modern benthic foraminifera, Cibicides wuellerstorfi (epifaunal) and Uvigerina species (infaunal) from the Coral Sea, and Cibicides refulgens (epifaunal) and Trifarina angulosa (infaunal) from Prydz Bay, Antarctica revealed relationships with temperature that have possible applications for reconstructions of bottom-water paleotemperatures. A positive relationship exists between the Mg/Ca and Sr/Ca ratios of Cibicides wuellerstorfi and Cibicides refulgens and ambient temperatures, at least within the range of 2 and 6°C. For the correlation between Mg/Ca compositions and temperature the r² values range from 0.78 (C. wuellerstorfi alone) to 0.88 (C. wuellerstorfi and C. refulgens together). At present, the Mg/Ca-temperature relationship must be regarded as tentative because of significant overlap of standard error values. The relationship between the Sr/Ca compositions of C. wuellerstorfi and bottom-water temperature yields an r² value of 0.95. These results indicate that Sr/Ca and possibly Mg/Ca ratios of Cibicides wuellerstorfi may provide useful information for the assessment of paleotemperature. Single-species data are presently insufficient to assess the influence of ambient temperature on trace-element compositions of Uvigerina species. Trifarina angulosa may have Mg/Ca compositions which are positively related to temperature, but Sr/Ca values seem unaffected by temperature. This may be due to pore-water influences on infaunal tests or to vital effects. Although more modern data are needed, our present results suggest that Sr/Ca ratios and possibly Mg/Ca ratios of some benthic foraminifera have the potential to be useful paleothermometers, at least within a temperature range of −2 to 6°C.     

Life cycles of Gammarus oceanicus and G. salinus (Amphipoda) in the Oslofjord, Norway

In the Oslofjord the amphipods Gammarus oceanicus Segerstråle, 1947 and G. salinus Spooner, 1947 were estimated to live for a maximum of 15 months. All specimens which survived during winter died in spring, mainly in May. A G. oceanicus population living on a freshwater influenced shore contained smaller specimens, had a lower proportion of the female population in breeding condition and probably produced fewer broods than a population living on a fully marine shore. The differences are discussed in relation to environmental factors and the distribution of G. salinus. Gammarus oceanicus possibly was breeding from December to May, some females even in June, resulting in an estimated maximum of three broods from December to May. Gammarus salinus showed two breeding periods, the first from December to May, a few of these females even bred in June, while new females bred from June to October, giving estimated maxima of respectively three (December to May) and five broods. Gammarus salinus females entered a reproductive resting stage in September-October. The sex ratio was mostly female dominated. A shift to male dominance was noted in one population and was related to possible infections. Information from the literature on longevity and breeding periods was compiled and compared to the Oslofjord data.     

Late Quaternary paleoproductivity and deep water circulation in the eastern South Atlantic Ocean: Evidence from benthic foraminifera

Two late Quaternary sediment cores from the northern Cape Basin in the eastern South Atlantic Ocean were analyzed for their benthic foraminiferal content and benthic stable carbon isotope composition. The locations of the cores were selected such that both of them presently are bathed by North Atlantic Deep Water (NADW) and past changes in deep water circulation should be recorded simultaneously at both locations. However, the areas are different in terms of primary production. One core was recovered from the nutrient-depleted Walvis Ridge area, whereas the other one is from the continental slope just below the coastal upwelling mixing area where present day organic matter fluxes are shown to be moderately high. Recent data served as the basis for the interpretation of the late Quaternary faunal fluctuations and the paleoceanographic reconstruction.

During the last 450,000 years, NADW flux into the eastern South Atlantic Ocean has been restricted to interglacial periods, with the strongest dominance of a NADW-driven deep water circulation during interglacial stages 1, 9 and 11. At the continental margin, high productivity faunas and very low epibenthic δ¹³C values indicate enhanced fluxes of organic matter during glacial periods. This can be attributed to a glacial increase and lateral extension of coastal upwelling. The long term glacial-interglacial paleoproductivity cycles are superimposed by high-frequency variations with a period of about 23,000 yr. Enhanced productivity in surface waters above the Walvis Ridge, far from the coast, is indicated during glacial stages 8, 10 and 12. During these periods, cold, nutrient-rich filaments from the mixing area were probably driven as far as to the southeastern flank of the Walvis Ridge.     

生态效率视角下旅游业生态福利及驱动因素——以常州市为例

经济效益最大化与环境影响最小化是绿色旅游与可持续发展的内在诉求。本文立足于生态效率模型,创新性地提出旅游业生态福利指数,据此分析1995—2017年常州市旅游业生态福利变化趋势及驱动效应,旨在为评价旅游产业绿色可持续发展能力提供新视角。研究发现:(1)1995年来常州市生态足迹呈现先增长后下降趋势,但旅游业各部门生态足迹均不断增长,游客人均资源消耗约为本地居民人均资源消耗的2.81—9.37倍,面临艰巨的节能减排压力。(2)1995年来常州市本底生态效率与旅游生态效率逐年提升,分别增加了37033元/hm²和44226元/hm²;同等资源消耗下,旅游业平均每单位产出高14409元/hm²,但游客年均消耗的自然资源却为本地居民的5.78倍。(3)1995—2007年间常州市旅游生态福利升降波动频繁,2007年来呈以直线式地骤降,受规模效益影响,旅游业的绿色生态福利和高效性不断弱化,为全市的资源节约量下降了10.7倍。(4)迪氏对数指标分解法(Logarithmic Mean Disivia Index, LMDI)揭示规模...     

Herb-rich spruce forests in W Nordland, N Norway: an ecological and methodological study

The vegetation of herb-rich spruce forests in three localities in Brønnøy municipality, W Nordland, N Norway, has been analysed using 120 sample plots, each 25 m², distributed by a restricted random method. In connection with every sample plot a set of ecological variables have been measured. The most important gradients for the differentiation of the vegetation were identified by DCA ordination and statistical analysis of the vegetational and the ecological data sets. The gradients were: (1) the nutrient gradient, (2) the soil moisture gradient and (3) the microclimate gradient. The importance of choice of ordination technique (DCA or LNMDS) relative to the importance of the choice of some parameters in DCA and LNMDS has been evaluated. Indicating from this evaluation were (1) the choice of weighting function prior to DCA ordination can be as important as the choice of ordination technique when the data set is small; (2) choice of dimensionality in LNMDS is normally not as decisive for the ordination result as the choice of ordination technique and (3) when the data set is larger, the choice of scale range is less decisive for the ordination result than the choice of dimensionality in LNMDS.