Distribution and faunal associations of benthic invertebrates at Lake Turkana,Kenya

The benthic environment and fauna of Lake Turkana were studied during 1978–1979 to determine distribution patterns and associations of benthic invertebrates. Lake Turkana is a large, closed-basin, alkaline lake, located in northern Kenya.Detailed environmental information is currently only available for substrate variations throughout Lake Turkana. Water chemistry and other data are currently inadequate to evaluate their effects on the distribution of Lake Turkana benthic invertebrates. Three weak faunal-substrate associations were discovered at Turkana. A littoral, soft bottom association (large standing crop) is dominated by the corixid Micronecta sp. and the ostracod Hemicypris kliei. A littoral, rocky bottom association, also with a large standing crop, is dominated by various gastropods and insects. A profundal, muddy bottom association, with a very small standing crop, is dominated by the ostracods Hemicypris intermedia and Sclerocypris cf. clavularis and several gastropod and chironomid species.     

The community structure of macroalgae in a low shore mangrove forest in Selangor,Malaysia

The macroalgal communities associated with pneumatophores, basal area of tree trunks and sediment surface in the mangrove forest at Sementa, Selangor consisted of nine main species. Biomass, frequency of occurrence and relative cover of the species along a belt transect, showed two major trends, a decrease in these parameters in the landward direction for Colpomenia sp. Gracilaria blodgettii and Gracilaria crassa and an increase in the landward direction for Dictyota dichotoma, Catenella nipae, Rhizoclonium sp. and Bostrichia radicans. Algal dominance varied with substratum. Pneumatophores were dominated by Caloglossa lepreurii and sediment surface by D. dichotoma. The 40 cm zone at the base of tree trunks was dominated by two algal species. The 0–20 cm region above the sediment surface was colonized by C. nipae, while the 20–40 cm region was dominated by Rhizoclonium sp. The study identified the importance of substrate in macroalgal colonization.     

Caesium-137 and lead-210 dating of recent sediments from Mondsee (Austria)

Mean annual sedimentation rates over the last 20–30 years were determined in the pre-alpine Mondsee (Upper Austria) using Cs-137 and Pb(Po)-210 profiles for sediment core dating and two natural sediment markers. Lower sedimentation rates of about 2–3 mm yr^–1 were observed in the central part of the lake near the shore at 18–20 m and in the southern part at 30 m depth. Higher sedimentation rates of 4–7 mm yr^–1 were found in the central part of the lake at 47 and 65 m and in the northern bay at 18 and 41 m depth. At both these sites the Pb-210 profiles were strongly disturbed in the upper zone of the sediment cores, whereas the Cs-137 pattern remained intact. The higher annual sediment accumulation rates can be explained only partly by deposition of allochthonous material discharged by the streams, enhanced eutrophication in these parts of the lake, erosion and sediment focusing by turbidity currents being also probable.     

Seasonal variations in foraminiferal flux in the Southern Ocean, Campbell Plateau, New Zealand

Time-incremental sediment trap moorings were deployed at two sites across Campbell Plateau, New Zealand; one in the relatively quiet waters of the plateau interior (Pukaki Rise) and the other at the Antarctic Circumpolar Current-swept margin (eastern Campbell flank). A continuous record of particle flux over 416 days identifies marked differences in faunal composition and seasonal occurrence in response to these two dynamically different Southern Ocean settings. In the shallow and thermally isolated interior of the Pukaki Rise site, the flux of foraminifera was closely linked to the austral spring pulse of primary production, at which time 97% of the total foraminiferal production for the year occurred. This seasonal flux of foraminifera at Pukaki Rise was dominated by the species Globorotalia inflata and Globigerina bulloides. The collapse of phytoplankton production at the end of spring was most likely a result of a co-limitation of iron and silicic acid. Over the deep and dynamic eastern flank of Campbell Plateau there were four seasonal pulses of foraminiferal flux, the largest in spring when almost half of the foraminiferal production occurred. Most of the spring flux at this site consisted of Globorotalia inflata and Globigerinita glutinata. Summer at eastern Campbell flank, exhibited the lowest flux of foraminifera, but the highest species diversity, while autumn and winter fluxes were dominated by the deep-dwelling Globorotalia truncatulinoides. Although there was only a single pulse of foraminiferal flux at Pukaki Rise, its mass (g m^{− 2}d^{− 1}) was still greater than that which occurred over the flank, summed across all four seasons. However, the overall standing stock (tests m^{− 2}d^{− 1}) on the flank was more than twice that which occurred at the Pukaki Rise site.An examination of core-top material taken from gravity cores collected in the vicinity of the sediment trap locations, revealed typical Southern Ocean foraminiferal assemblages that were markedly dissimilar in proportion to those observed in the sediment traps.     

Mineral cycling in a tropical palm forest

Nutrient cycling and biomass characteristics of a tropical palm forest dominated byOrbignya cohune were found to be different from thsoe of hardwood dominated forests. The cohune palm forest had a high proportion of biomass in leaves (5%), a reduced sapling layer, a large amount of standing forest litter and an exceptionally low decomposition rate factor (0.1 year^–1). Mineral concentrations in palm leaves were generally lower than in hardwood species with the exception of Na, which was exceptionally high inOrbignya cohune. Biomass was estimated at 226 tons ha^–1 containing 1173 kg ha^–1 N; 126 kg ha^–1 P; 437 kg ha^–1 K; 1869 kg ha^–1 Mg; 125 kg ha^–1 Ca, and 2177 kg ha^–1 Na. Soils of cohune association did not differ significantly from those of neighbouring hardwood dominated associations with the exception of Na which occurred in higher concentration because of bioaccumulation in the dominant. The results suggest that the growth habits and physiology of a dominant can strongly influence some of the ecological parameters used to describe aforest association.     

The response of a harpacticoid copepod community to sediment disturbance in a semi-enclosed lagoon

The harpacticoid fauna of a sandy sediment in the Sluice Dock of Ostend, Belgium, was dominated by a single species, Canuella perplexa, that attained an average annual density of over 400 ind. 10 cm^–2 in 1976 and 1977, whereas other species had a total mean density of less than 10 ind. 10 cm^–2. In the summer of 1979 a dystrophic crisis with abundant growth of Ulva occurred and in March 1980 the lagoon was drained. After refilling of the lagoon, the sediment was immediately colonized by good swimming harpacticoids, that attained densities of 200 ind. 10 cm^–2. Three months after refilling Canuella perplexa reappeared and the system returned to its original state within one month.     

Fine-fraction carbonate stable isotopes as indicators of seasonal shallow mixed-layer paleohydrography

We have measured stable isotopic compositions of Miocene pelagic fine-fraction (<63 μm) carbonates from oligotrophic deep-sea sites in the Pacific and Atlantic oceans and compared them with those of coexisting foraminifers to test their utility as near sea-surface indicators. Fine-fraction carbonates (primarily polyspecific nannofossils) and surface-dwelling planktic foraminiferal (Globigerinoides) stable isotopes both have been considered to reflect surface-water hydrographic conditions. However, our results indicate that fine-fraction stable isotopes are offset from and do not correlate well with those of Globigerinoides. In contrast, stable isotopic records of the deep-dwelling planktic foraminifer Globoquadrina are in good correspondence with the fine-fraction records in terms of long-term (ca. >1 m.y.) trends and temporal variability. On the basis of a time-series hydrography and flux study site in the oligotrophic subtropical North Atlantic, we interpret the isotopic discrepancies between fine-fraction and Globigerinoides as resulting primarily from season of calcification, as well as possible vital effects. We suggest that fine-fraction stable isotope values from oligotrophic waters reflect late winter–early spring relatively cool, nutrient-rich shallow mixed-layer conditions during the time of deep mixing (i.e., spring bloom), whereas Globigerinoides stable isotope values record conditions that prevailed in the stratified surface waters in the warmer late spring–fall. This implies that paired analyses of fine-fraction and surface-dwelling planktic foraminiferal δ¹⁸O could be applied to reconstruct paleoseasonality of the open oceans. However, because the fine-fraction δ¹³C values are not representative of the annual mean surface-water δ¹³C, we recommend use of near surface-dwelling planktic foraminiferal δ¹³C as a proxy for δ¹³C of stratified surface waters that are more or less in equilibrium with the atmosphere with respect to pCO₂.     

The role of zoobenthos in energy flow in deep,oligotrophic Lake Thingvallavatn,Iceland

Macrozoobenthos in Thingvallavatn is dominated by 42 taxa. The vertical distribution delimits 5 communities: (1) the surf zone community from 0–2 m, (2) the upper stony littoral community from 2–6 m, (3) the lower stony littoral community from 6–10 m, (4) the Nitella zone community from 10–20 m, and (5) the profundal zone community from 20–114 m. Total mean lakewide production was 78 kJ m^–2 yr^–1. Herbivores, detritivores, and carnivores contributed 59%, 38% and 3%, respectively. Respiration and ingestion were estimated according to the literature. Net production efficiency averaged 0.50. Ingestion was dominated by herbivores in the littoral zones (46–81%), while detritivores made up 93% in the profundal zone. Total zoobenthic production averaged 6% of estimated available food with a range from 10–11% in the three upper littoral zones to only 2% in the Nitella zone. The profundal fauna converted 6% of the estimated sedimentation of organic matter to secondary production. On a lakewide basis the zoobenthis utilized one third of the estimated potential food resources. Zoobenthic production made up 32% of total secondary production.     

Nitrogen and phosphorus budgets of a nymphaeid-dominated system

Summary Communities dominated byNymphoides peltata (Gmel.) O. Kuntze (Menyanthaceae) have been studied within the framework of the project on structure, dynamics and function of nymphaeid-dominated systems. VAN DER VELDE, 1980). In this summary some remarks on the quantitative distribution of N and P in an old river bed are presented with special emphasis on sites dominated by the floating-leaved macrophyteNymphoides peltata. The study area was the Bemmelse Strang, an old branch of the river Waal situated in the northern river forelands between Lent and Bemmel, north of Nijmegen. Two sampling sites were chosen,viz. one dominated byNymphoides peltata and another without macrophytes (the open water). Several compartments were distinguished in these sites,viz., water, seston, sediment and macrophytes. Water and seston samples were collected biweekly and sediment and macrophyte samples monthly from January until December 1980. In the sediment most nutrients seemed to be stored in the upper layers, so cores to a depth of 10 cm were taken. The percentage of water in the sediment, the specific mass of the sediment, the biomass of seston andNymphoides (expressed as dry weight) and the water depth were recorded at each sampling data. The dried samples of sediment, seston andNymphoides were analysed for total N and total P. In the water and interstitial water (soil extracts) total N, NH₄ ⁺, NO₃ ^––NO₂ ^–, total P and PO₄ ^3– were determined. By means of these data the quantitative distribution of nitrogen and phosphorus in the system could be established.     

History of Late Holocene vegetation at Quintana Roo,Caribbean coast of Mexico

A pollen record of a Late Holocene sediment core from the Mexican Caribbean coast (Quintana Roo) shows the development and changes of a mangrove system. Humid conditions seem to have persisted for the period approximately 2500–1500 ¹⁴C yr BP (pollen zone I), and mangrove Rhizophora mangle dominated with a good representation of elements from the nearby semi-evergreen tropical forest. During the period approximately 1500–1200 ¹⁴C yr BP (pollen zone II) the mangrove Conocarpus erecta dominated. R. mangle almost disappeared and other taxa appeared, suggesting drier climatic conditions and generally more open vegetation. This dry period coincided with the period of the Maya cultural decline. The following period (pollen zone III, approximately 1200–1000 ¹⁴C yr BP) was characterized by the recovery of R. mangle, indicating more humid conditions than in the preceding pollen zone. Pollen zone IV (approximately 1000 ¹⁴C yr BP till present) suggests a drier period reoccuring with C. erecta; this marks the transition to present day conditions.     

The trophic state of Lake Ladoga as indicated by late summer phytoplankton

As a part of the joint Russian-Finnish evaluation of human impact on Lake Ladoga, we studied the phytoplankton of the lake in order to find biological indicators for eutrophication. A second aim of the investigation was intercalibration of sampling and phytoplankton counting techniques between the Russian and Finnish laboratories. Phytoplankton samples were collected from 27 sampling stations in the lake and from the rivers Volkhov and Neva in 9–13 August 1993. In surface water samples the phytoplankton fresh weight biomass varied in the range 218–3575 mg m^–33. Highest biomass values were encountered in Sortavala Bay, and lowest ones in the western central part of the lake. Phytoplankton species composition varied considerably in the lake; blue-green and green algae predominated near-shore areas and Cryptophyceae in the offshore stations. Canonical correspondance analysis revealed close grouping of eutrophy indicating communities, dominated mainly by greens and blue-greens, in the most nutrient-rich parts of Lake Ladoga, the Volkhov and Svir Bays. Samples from the vicinity of the inflows of Vuoksi and Burnaya Rivers and off Pitkaranta formed a separate group, dominated by diatoms, most of which were typical to mesotrophic or eutrophy lakes. As judged by phytoplankton biomass values and chlorophyll a concentrations, Lake Ladoga may generally be classified as mesotrophic. Eutrophicated areas are found in the northern archipelago of the lake and in the areas influenced by large rivers.     

Spatial distribution of live benthic foraminifera in the Rhône prodelta: Faunal response to a continental–marine organic matter gradient

Benthic foraminifera were collected in the Rhône prodelta (Gulf of Lions, Mediterranean Sea), an enriched zone with high organic matter content. In June 2005, sediment cores were sampled at depths ranging from 20 to 100 m. Four distinct foraminiferal assemblages were determined in the study area, reflecting the geographical distribution of the impact of river supply. The living foraminiferal faunas present a typical picture, with strongly impoverished faunas composed exclusively of stress-tolerant taxa (Fursenkoina fusiformis, Bulimina aculeata, Leptohyalis scottii, and Adelosina longirostra) in the immediate vicinity of the river mouth. This assemblage is well adapted to a high input of continental organic matter and a minimum oxygen penetration depth into the sediment. To the southwest, under the main corridor followed by the river plume, high organic input with a dominantly terrestrial signature (more refractory) may be stressful for many taxa which need organic matter of a more labile quality. In this area, Nonion scaphum, Nonionella turgida and Rectuvigerina phlegeri are present in low densities. On the edge of this area, these taxa show much higher densities. A greater proportion of marine organic carbon could explain their increasing abundances in this area. Towards the east and towards the deepest stations, in the outer part of the enriched zone, biodiversity increases. Faunas at these stations have intermediate densities and contain a number of taxa (Cassidulina carinata, Epistominella vitrea, Valvulineria bradyana, Nonionella iridea/bradyi) at the deepest stations; Bolivina dilatata/spathulata and Textularia porrecta at the eastern stations) that seem to benefit from more marine organic matter. The comparison of geochemical measurements and foraminiferal data strongly suggests that the spatial distribution of foraminifera in the Rhône prodelta is mainly governed by the quality and the quantity of organic matter reaching the sediment–water interface. Since bottom waters are well oxygenated (215–260 µmol/L), and oxygen penetration into the sediment is less than 1 cm at all stations, benthic ecosystem oxygenation appears to have only a minor impact on regional differences in faunal distribution.     

Distribution of Antarctic benthic foraminifers settling on the pecten Adamussium colbecki

Summary Some benthic foraminifers in Explorers Cove, Antarctica, occur both in the sediment and on hard objects such as rocks and invertebrates. The abundances of four of these foraminiferal species have been measured from sediment samples and from the upper valve of the pecten Adamussium colbecki. The two calcareous species, Cibicides refulgens and Rosalina globularis were more abundant on the pecten shells than the sediment: the agglutinated species, Trochammina ochracea and T. malovensis were more abundant in the sediment. A zone of low foraminiferal density was observed around the outer margin of each shell, but no evidence of an influence of pecten feeding currents on the foraminiferal distributions was found. The size of the pecten shell influenced the density of epizoic foraminifers colonizing it; large shells (area >43 cm²) supported much higher densities than smaller ones.     

Non-random association of trypsin-banded human acrocentric chromosomes

Summary This paper deals with a computer-aided study of the associations between acrocentric chromosomes as well as between those other chromosomes which in our investigations were revealed to be significantly closer to each other than random. The chromosome pairs were identified by a trypsinbanding technique. The method used has been elaborated previously with the specific aim of determining associations in a manner that avoids all subjective criteria.The tendency for association between homologous chromosomes is in decreasing order: 21 and 13>1>14, 18 and 19>17. Among the nonhomologous acrocentric chromosomes the significant tendencies for associations are between D-D: 13–14>13–15>14–15; between D-G: 13–21>14–21>13–22>15–22.The implication of the different tendencies to associate are dicussed in terms of aetiology of numerical and structural chromosome abnormalities.     

Impacts of storms on Recent planktic foraminiferal test production and CaCO3 flux in the North Atlantic at 47 °N, 20 °W (JGOFS)

Planktic foraminiferal assemblages are well known to vary in accordance with seasonal fluctuations in ocean properties, periodic reproduction cycles, and variations between water masses. Here we report that storms also can significantly influence foraminiferal assemblages. During the RV Meteor cruise 21 to the Northeast Atlantic Ocean ( area), from March to May 1992, planktic foraminifera were sampled using a multiple opening-closing net. While sampling, two storms with wind forces up to 12 Beaufort caused intensified surface layer mixing with shifts in the depth of the upper ocean mixed-layer from 20–40 m to 170–240 m. Subsequently, planktic foraminiferal growth rates increased, resulting in an elevated quantity of small (100–150 μm) tests (Phase 1). When the wind strength increased a second time, the mixed-layer deepened to a depth below the former position of the pycnocline, and again the abundance of small tests increased (Phase 2). During Phase 2, the weight of calcite in specimens of the productive zone reached its maximum. In the export zone, an associated increase in empty tests occurred with a lag time depending on the test sinking velocity. In the upper export zone, down to 700 m water depth, CaCO₃ flux increased from 9.3 to 49.8 mg CaCO₃ m⁻² d⁻¹ after the first storm and from 8.9 to 19.9 mg CaCO₃ m⁻²d⁻¹ after the second storm. In the 700 to 2500 m depth interval, the flux increased from 5.1 mg CaCO₃ m⁻² d⁻¹ to about 9.2 mg CaCO, m⁻² d⁻¹. Thus, the standing stock of living foraminifera and export of empty tests from the productive zone increased after the storms, leading to pulses of CaCO₃ exported from the surface to deep water.     

Asexual propagations of introduced exotic macrophytes <Emphasis Type="Italic">Elodea nuttallii</Emphasis>, <Emphasis Type="Italic">Myriophyllum aquaticum</Emphasis>, and <Emphasis Type="Italic">M. propinquum</Emphasis> are improved by nutrient-rich sediments in China

An increasing number of recent studies indicate that multiple interacting factors can affect the invasion of plants. However, few studies have focused on asexual propagation and the interaction of propagation with environmental factors that regulate the invasive potential of introduced exotic species in aquatic habitats. This study was designed to investigate the differences in asexual propagation between introduced exotic and non-invasive native aquatic macrophytes in nutrient-poor and nutrient-rich sediments and to test the hypothesis that differences in asexual propagation (stem fragment production) and propagule establishment between introduced exotic and non-invasive native macrophytes are driven by sediment nutrient levels. Three exotic aquatic macrophytes (Elodea nuttallii, Myriophyllum aquaticum, and M. propinquum) recently introduced to China and their non-invasive native counterparts (Hydrilla verticillata, M. oguraense, and M. ussuriense) were used for comparison in nutrient-poor (TN 0.59 and TP 0.03 mg g⁻¹) and nutrient-rich (TN 2.35 and TP 0.10 mg g⁻¹) sediments. After 8 weeks of growth, the exotic species tended to produce more total biomass, branch biomass and apical shoots and have higher relative growth rate (RGR) than their native counterparts in nutrient-rich sediment. Rooting efficiency and root growth of exotic fragments were higher than that of native counterparts in nutrient-rich sediment, although the survival rates of fragments did not differ between native and exotic species. In addition, superior traits (rooting efficiency and root growth) of exotic species were also observed in nutrient-poor sediment, but to a lesser degree than in nutrient-rich sediment. These results suggest that asexual propagation of these three introduced exotic macrophytes is more effective in nutrient-rich sediment than in nutrient-poor sediment in China.     

Paleoenvironmental change at the Danian–Selandian transition in Tunisia: Foraminifera, organic-walled dinoflagellate cyst and calcareous nannofossil records

In the present study, we document paleoenvironmental change across the Danian–Selandian transition (planktic foraminiferal interval P2–P3b; calcareous nannofossil Zone NP4, Subzones NTp6–NTp8A; 61–59 Ma) in NW Tunisia. Diversifications of Paleogene planktic foraminifera with the evolution of the muricate and photosymbiotic lineages Morozovella, Acarinina and Igorina and of the biostratigraphically important nannofossils genus Fasciculithus are recorded within this interval. The present study aims to understand early Paleogene environmental changes in the southern Tethys, by analyzing the evolution of surface-water and–to a lesser extent–seafloor conditions. Three localities were investigated: Ain Settara, Elles and El Kef, all representing outer neritic deposition in the same basin, the Tunisian Trough. Paleoenvironmental changes are explored by combining planktic foraminiferal, organic dinocyst and calcareous nannofossils assemblages and several proxy parameters (planktic/benthic ratio, numbers of planktic foraminifera per gram, peridinioid/gonyaulacoid ratio; terrestrial/marine palynomorph ratio). In addition, also some geochemical parameters (calcite content and stable isotopes) are examined. Our records indicate that the environment evolved from an initially oligotrophic, open marine, deep outer neritic setting in P2–P3a towards a shallower and nutrient-rich setting from the base of Subzone P3b. This change is seen in the foraminiferal assemblages, with the substitution of Praemurica by Morozovella among the planktic foraminifera and an upward decrease in deeper benthic taxa. Also the organic-dinocyst assemblages show a peak of peridinioid cysts (Cerodinium and Lejeunecysta). Associated to these dinocyst assemblages, the lowest occurrence of Apectodinium is recorded, which seem to have evolved in this region, possibly in response to enhanced nutrient levels on the shelf. Additionally, a distinct change in calcareous nannofossil assemblages is also described, marked by the lowest appearance of Chiasmolithus edentulus, the lowest consistent occurrence of Fasciculithus and a slight increase in near-shore taxa (essentially Pontosphaera).This project provides an accurate understanding of paleoenvironmental change across the Danian–Selandian transition in Tunisia. Especially, integrating different proxies demonstrates a paleobathymetric shallowing from the Danian to the Selandian, associated to increase surface paleoproductivity. Furthermore, the results are compared with those from other localities along the Southern Tethyan margin (Egypt and Jordan) and a more regional paleoclimatic/paleoceanographic perturbation in the Southern Tethys is suggested.     

Population dynamics of Marginopora kudakajimensis Gudmundsson (Foraminifera: Soritidae) in the Ryukyu Islands, the subtropical northwest Pacific

The population dynamics of Marginopora kudakajimensis Gudmundsson, a dinoflagellate endosymbiont-bearing soritid foraminifer, was studied in the Ryukyu Islands, the subtropical northwest Pacific. Macroalgal samples were collected monthly between November 1995 and November 1996 at a 1-m-deep lagoonal site colonized by this species. Monthly variations in the size–frequency distributions and population density indicate that this foraminiferal population replaces itself in one year. Asexual reproduction occurs twice a year, in late spring and winter; in late spring, some of the adult individuals reproduce by multiple fission simultaneously. As a result, two cohorts (a late spring and a winter cohort) are found in the population during a year. Life span of the former cohort is up to one year, while that of the latter cohort is up to six months. Megalospheric specimens comprise up to 99% of the population with a few microspheric individuals throughout the year. The life tables and survivorship curves revealed that size-specific mortality rates were very low during the first several size classes and increased thereafter, indicating low juvenile mortality with high mortality later in life. The carbonate production rate by this Marginopora population is approximately 5 kg CaCO₃ m⁻² yr⁻¹, which is extremely higher than those reported for other larger foraminiferal species.     

Stable oxygen and carbon isotope information on the establishment of a new, opportunistic foraminiferal fauna in a Swedish Skagerrak fjord basin, in 1979/1980

Significant faunal changes reported from recent, coastal environments, which are not directly influenced by urban and industrial impact, are rarely seen. In Gullmar Fjord on the Swedish west coast, a significant foraminiferal fauna change occurred in connection with severe low-oxygen conditions that evolved in the winter of 1979/1980. A foraminiferal fauna marked by common Skagerrak–Kattegat species, which had previously characterised the deep fjord basin, was replaced by the opportunistic, low-oxygen tolerant species Stainforthia fusiformis (Williamsson).To study this phenomenon further we performed stable oxygen and carbon isotope analyses on the indicator species itself, S. fusiformis, both on specimens from sediment cores representing approximately the last 85 years and on living (stained) individuals taken from a transect across the deep fjord basin. Our purpose was to detail how and why S. fusiformis, came to dominate the fauna.The oxygen isotope results suggest that salinities and temperatures in the deep basin have been relatively constant over the last c. 85 years, while the carbon isotopes show a significant change towards more negative values in association with the faunal shift of 1979/1980. The combined results from both the cores and the surface sediments suggest that S. fusiformis did not inhabit the deep basin until 1980. Before then, almost all specimens of S. fusiformis were small sized and their carbon isotope values suggest they were re-deposited shallow-water specimens that had been transported down to the central, deep basin as part of a suspension load. After a major faunal extinction in 1979–1980, S. fusiformis of all sizes suddenly appeared in large numbers and their carbon isotopic values were similar to the signal from registered in the recent, living fauna within the deep basin. This suggests that the opportunistic S. fusiformis established itself in the deep basin as a consequence of the severe low-oxygen event and the faunal crash of the previously dominating Skagerrak–Kattegat fauna.     

Nutrient (N,P, Si) fluxes between marine sediments and water column in coastal and open Adriatic

Nutrient benthic fluxes, as well as sediment phosphorus concentration at the open sea and coastal water stations of the Central and South Adriatic were studied during 1997–98. The fluxes were in the ranges: 0.16–2.67 mmol m^–2 d^–1 (silicate); –0.031–0.164 mmol m^–2 d^–1 (phosphate); –0.51–2.03 mmol m^–2 d^–1 (ammonia); and –1.32–1.62 mmol m^–2 d^–1 (nitrate + nitrite). Silicate flux showed a gradient from the coastal area to the open sea. Ammonia was the main nitrogen species in the flux at the estuary and bay stations, while the sum of nitrate and nitrite was predominant at the open sea stations. Relationships between phosphate and ammonia fluxes (r = 0.699, p<0.01) as well as phosphate and silicate (r = 0.529, p<0.01) were established.