Dinoflagellate Cysts In Surface Sediments Research Articles

Qualitative and Quantitative Study of Dinoflagellate Cysts in Surface Sediments of the Nador Lagoon (North-East Morocco)

The qualitative and quantitative study of dinoflagellates (cysts and vegetative forms) was carried out on samples of surface sediment and water of the Nador lagoon (North-East Morocco), collected during winter in February 2019. Therefore, it was necessary to undertake a qualitative and quantitative study on dinoflagellate cysts and vegetative forms in parallel with the aim of specifying the factors that control the concentration of cysts in the sediments, as well as their specific diversities and blooms. Notably, dinoflagellates are of undeniable ecological interest and are considered as sentinel species of the quantity of water because they respond quickly to environmental changes due to their very fast life cycle. Moreover, their cysts, due to their extreme resistance and abundance in sediments, constitute an extremely important tool in the evaluation of current environments. Results showed that the total abundances of dinoflagellate cysts vary between a concentration of 720 cysts/g dry sediments (DS) and 7215 cysts/g DS. This work was mainly conducted to study the abiotic parameters of the Nador lagoon that control the concentration of cysts in the sediments and address their specific diversity and the dominance of one group over the other.

Distribution of organic-walled dinoflagellate cysts in surface sediments of the southern Caribbean and the eastern tropical Pacific and its environmental implications

Little is known about the marine palynology of the neotropical oceans. Here, we present the first comprehensive study of organic-walled dinoflagellate cyst assemblages in 52 surface marine sediment samples from the southern Caribbean (SC) and the eastern tropical Pacific (ETP) and explain how these assemblages relate to sea-surface parameters. Multivariate analyses show that of the several environmental parameters considered, sea-surface salinity (SSS), phosphate concentrations, and nitrate concentrations best explain the relative abundances and the geographic distribution of dinoflagellate cysts in the studied area. Consistent with regional differences in marine productivity, dinoflagellate cyst concentrations were markedly different in the SC (1979 ± 1053 cysts/g) and the ETP (3105 ± 1956 cysts/g). Sediments of the SC are characterized by high relative abundances of the Spiniferites spp. group, cysts of Protoceratium reticulatum, and the presence of rare dinocyst taxa. The dinocyst assemblages from the ETP are characterized by higher relative and absolute abundances of Bitectatodinium spongium, Brigantedinium spp., and Echinidinium aculeatum. This pattern is explained by the more eutrophic nature of the ETP compared to the highly saline and oligotrophic SC. Average values of the Shannon Index (H′) from the ETP are higher compared to the SC, demonstrating that dinocysts respond to the greater climatic variability that characterizes the ETP. Brigantedinium spp. abundances are negatively correlated to H′ diversity supporting its dominant character within the dinocyst community. This work fills a gap in our knowledge on modern dinocyst distribution in neotropical oceans and provides a modern reference for interpreting down core dinocyst variations and paleocenographical reconstructions in the region.

Dinoflagellate cysts in surface sediments at Van Phong Bay, Khanh Hoa Province, Vietnam: distribution, abundance and potentially harmful algal blooms

Studies on dinoflagellate cysts provide important knowledge on the ecology of dinoflagellates and harmful algal blooms (HABs). In this study, distribution and abundance of dinoflagellate cysts in surface sediments from 17 stations at Van Phong Bay were analyzed. There were 55 different types of cysts representing 3 orders and 18 genera, and 8 unidentified cyst types recorded. Peridiniales was the most diverse order with 29 cyst types, including 20 Protoperidinium cyst types. There were 10 cyst types of 7 potential toxic dinoflagellate species and 4 of bloom forming species found, indicating a potential risk of harmful algal blooms in Van Phong Bay. Number of cyst types and density ranged from 12 to 31 types and from 115 to 3,760 per gram of dry weight sediment, respectively. Cysts of Leonella granifera were dominant at stations in the mouth of the Bay, while Scrippsiella trochoidea cysts dominated at all stations. Shannon diversity index (H') was low, varying from 1.192.72. There were two distinct cyst assemblages identified with 40% Bray-Curtis similarity, assemblage I with 2 stations (VP09 and VP10), and assemblage II with the other stations.

Diversity and distribution of dinoflagellate cysts in surface sediments from fjords of western Vancouver Island (British Columbia, Canada)

Abstract A total of 31 surface sediment samples from 16 coastal inlets in five sounds of western Vancouver Island were investigated for dinoflagellate cysts and other palynomorphs. Well-preserved and abundant dinoflagellate cysts were recovered, including a total of 32 cyst taxa belonging to four families. Total dinoflagellate cyst concentrations vary two orders of magnitude, with concentrations between 2267 and 918,584 cysts g−1. The highest values were observed in samples from Tofino Inlet. Southern sites are characterized by cysts of autotrophic dinoflagellates, mainly Operculodinium centrocarpum sensu Wall & Dale 1966. Other abundant cysts of autotrophic dinoflagellates are Spiniferites spp. and cysts of Pentapharsodinium dalei. In general, other inlets in Quatsino, Kyuquot-Nootka and Clayoquot Sounds have lower total concentrations but have more cysts of heterotrophic dinoflagellates, mainly Round brown cysts, Brigantedinium spp., and Spiny brown cysts. Neroutsos Inlet is characterized by high concentrations of Arcellacean testate amoebae. Within inlets, cyst concentrations and assemblages vary. Near the heads of the inlets, concentrations are generally lower and assemblages are dominated by cysts of autotrophic dinoflagellates, mostly O. centrocarpum sensu Wall & Dale 1966. Concentrations of cysts produced by heterotrophic dinoflagellates and their proportions in the assemblages generally increase from the head to the mouth of each inlet. Measured sedimentary biogenic silica abundances (%Opal) have consistently higher values in Clayoquot Sound and lower values in Quatsino Sound. Within individual inlets, biogenic silica generally increases in the head to mouth direction. The trend in heterotrophic cyst abundances is similar. Correlations between total organic carbon (TOC), total nitrogen (TN) and terrestrial palynomorph concentrations in the sediments indicate that the organic material at sites near inlet heads are mainly derived from terrestrial input. A significant negative correlation between biogenic silica and TOC/TN ratio was observed in the dataset, but not between the total heterotrophic cyst concentrations and relative abundances of biogenic silica. Statistical analyses (PCA, RDA) indicate that the assemblages of dinoflagellate cysts and other palynomorphs, their spatial distributions, and sedimentary geochemical measurements are related to the regional environmental setting (e.g., latitudinal trends in weather, primary productivity, and upwelling) and local characteristics of the inlets (e.g., site location relative to freshwater input, inlet morphology and bathymetry, as well as possible anthropogenic influences). Process length variation of O. centrocarpum sensu Wall & Dale 1966 was measured and it is comparable to previous measurements in similar environmental settings, allowing seawater densities to be inferred. Cysts of Alexandrium spp. were found in most of the samples, with the highest abundance in the inlet heads of Kyuquot and Quatsino Sounds.

제주 해안주변해역 표층퇴적물 중 와편모조류 시스트 군집의 분포특성

제주 해안주변해역 표층퇴적물 중 와편모조류 시스트 군집의 분포특성

Dinoflagellate Cyst Assemblages in Surface Sediments from Three Shallow Mediterranean Lagoons (Sardinia, North Western Mediterranean Sea)

The present study identified and quantified dinoflagellate cysts in surface sediments from three Mediterranean lagoons. Sediment samples were recovered from 11 stations in May 2009 at Cabras Lagoon, eight stations in May 2010 at Corru S'Ittiri Lagoon, and five stations in May 2011 at Santa Giusta Lagoon. Fifty-three dinoflagellate cyst morphotypes were identified. Sixteen species are first reports for the lagoons, and two for the Mediterranean Sea. Moreover, a new Scrippsiella species was discovered in Cabras. Seven harmful algal species were identified, primarily belonging to the potentially toxic genus Alexandrium. Total cyst abundance, number of morphotypes, and assemblages varied among lagoons, and each lagoon showed a distinct morphotype composition. A degree of heterogeneity was also detected within lagoon. Cabras and Santa Giusta cyst assemblages were characterised by morphotypes belonging to the autotrophic genus Scrippsiella, whereas Corru S'Ittiri assemblages showed dominance of heterotrophic morphotypes, including Protoperidinium cf tricingulatum. Differentiation among lagoons was also evident according to environmental conditions. Salinity proved to be a fundamental variable in determining total cyst abundance, morphotype number, and composition. This study was among the first to examine dinoflagellate cyst composition in coastal lagoons, especially from the Mediterranean region, and contributed data that increased our knowledge of cyst-producing dinoflagellates in these environments.

Dinoflagellate cyst production and flux in Gamak Bay, Korea: A sediment trap study

Abstract To develop a better understanding of the species composition and production of dinoflagellate cysts, including the ecological characteristics of Polykrikos species, a sediment trap study was conducted from June 2005 to June 2006 in Gamak Bay, Korea. Thirty-two dinoflagellate cyst taxa were identified in the sediment trap samples, and the dinoflagellate cyst assemblages were found to be dominated by cysts of Polykrikos kofoidii , Scrippsiella trochoidea , Protoperidinium spp., Polykrikos schwartzii , Gymnodinium catenatum and Ensiculifera carinata . The flux of dinoflagellate cysts ranged from 0.10 × 10 5 to 35.97 × 10 5 cysts m − 2 day − 1 , and the highest flux occurred during summer, and was driven completely by the flux in the production of P. kofoidii and P. schwartzii cysts. The timing of the production of cysts of Polykrikos species seemed to be related to the appearance of G. catenatum as prey. The assemblages of dinoflagellate cysts in surface sediments from Gamak Bay, and their seasonal changes, were very similar to those in the sediment trap samples, which suggested that the monitoring of dinoflagellate cysts in sediment samples can provide information on the environmental conditions in Gamak Bay.

Occurrence and germination of dinoflagellate cysts in surface sediments from the Red Sea off the coasts of Saudi Arabia

The distribution and abundance of dinoflagellate cyst assemblages were investigated in surface sediments from south-western Red sea coasts of Saudi Arabia at six sites during March 2010. A total of 19 taxa of dinoflagellate cysts were identified from all sites. The sampling sites showed a similar cyst assemblage, but they differed in total cyst abundance (3 to 4083 cysts g−1 dry weight). Cyst abundance was strongly correlated with sediment characteristics, the highest numbers being recorded in sediments with large contents of organic carbon, silt and clay. Cyst assemblages were dominated by cysts of potentially toxic species, including Cochlodinium polykrikos, Prorocentrum minimum, Dinophysis acuminata, Alexandrium catenella and Scrippsiella trochoidea. Most cysts germinated successfully at different rates at 15 and 25° C. This study suggests that surface sediments from all Saudi Red Sea coasts should be monitored for the presence of dinoflagellate cysts to give ample warning of the presence and abundance of toxic species in a given area.

Dinoflagellate Cysts in Surface Sediments from Southern Coast of Korea

To investigate the distributions of dinoflagellate cysts in relation to environmental conditions from southern coast of Korea, surface sediment samples collected from 11 stations in Gamak Bay, Yeoja Bay and the offshore area of Yeoja Bay were analyzed. Dinoflagellate cyst assemblages observed in the study area included many species commonly reported from other temperate regions. Among them, Polykrikos cysts were dominant, together with Brigantedinium spp. and Spiniferites spp. Based on cluster analysis, dinoflagellate cyst assemblages were divided into two main groups; group I, located in Yeoja Bay and group II, located in Gamak Bay and the offshore area of Yeoja Bay. Principal component analysis identified differences in salinity levels as the main environmental factors affecting the distributional characteristics of dinoflagellate cyst assemblages in the study area. Gamak Bay is a typical eutrophied area as result of extensive human activities around the bay, and heterotrophic cysts, including Polykrikos cysts, are remarkably abundant and likely to be a useful indicator for eutrophication in Gamak Bay.

Distribution of dinoflagellate cysts in surface sediments from the northeastern Pacific Ocean (43–25°N) in relation to sea-surface temperature, salinity, productivity and coastal upwelling

Fifty-six surface sediment samples from the northeastern Pacific (43–25°N) were investigated in order to examine the spatial distribution of modern organic-walled dinoflagellate cysts in relation to hydrological conditions and marine productivity. The analyzed dinoflagellate cyst assemblages are diverse, and include over 60 taxa. Multivariate statistical analysis (CCA) of dinoflagellate cysts and environmental variables identifies annual productivity and sea-surface temperature as main factors affecting dinoflagellate cyst distribution in the region. In the studied area, marine productivity is greatly influenced by the strength of the coastal upwelling. Cyst assemblages from the coastal sites associated with active upwelling are characterized by the dominance of heterotrophic taxa, particularly Brigantedinium spp., Echinidinium spp. and cysts of Protoperidinium americanum. Taxa associated with low productivity offshore sites are Impagidinium spp., Nematosphaeropsis labyrinthus, Pyxidinopsis reticulata and Operculodinium centrocarpum. Dinoflagellate cyst species associated with warmer waters are Lingulodinium machaerophorum, Spiniferites mirabilis, S. ramosus, S. delicatus/bulloideus, Bitectatodinium spongium and Polykrikos cf. kofoidii, while those from cooler environments include Selenopemphix nephroides, Trinovantedinium variable and cysts of Pentapharsodinium dalei. Combining the present cyst dataset with other published cyst data from the Northeastern Pacific, we have compiled a “NE Pacific 188” database. This database can be used as a basis for the quantitative reconstructions of (paleo)temperature and productivity in the Northeastern Pacific.

Distribution of dinoflagellate cysts in surface sediments of the Mackenzie Shelf and Amundsen Gulf, Beaufort Sea (Canada)

In order to document long-term climate cycles and predict future climate trends for the Arctic, we need to look at the geological records to establish the link between historical and pre-historical sea-surface parameters. Dinoflagellate cysts (dinocysts) are used as proxy indicators of sea-surface parameters (temperature, salinity, sea-ice cover, primary productivity) jointly with transfer functions and a modern dinocyst reference database, to reconstruct the evolution of sea-surface conditions at decadal and millennial timescales. Here we present the surface distribution of recent dinocyst assemblages from 34 surface sediment samples collected on the Mackenzie Slope/Amundsen Gulf during the 2004 CASES (Canadian Arctic Shelf Exchange Study) cruise. Dinocyst concentrations in surface sediments are relatively high outside the Mackenzie plume area and increase gradually eastward toward Amundsen Gulf. The cysts of autotrophic dinoflagellates are dominant throughout the study area, while the maximum abundance of heterotrophic taxa is found within the Mackenzie plume. Hierarchical clustering analyses allowed defining two dinocyst assemblages. Assemblage I is located on the Mackenzie Slope and southern Amundsen Gulf, while Assemblage II is located within the Cape Bathurst Polynya area in northern Amundsen Gulf. Both assemblages are dominated by Operculodinium centrocarpum, but are distinguished on the basis of the relative abundance of Islandinium minutum, a taxon generally associated with sea ice. I. minutum is found in lower abundance in the Cape Bathurst Polynya.

Modern Dinoflagellate Cysts Distribution off the Eastern Part of Geoje Island, Korea

Distributional characteristics of dinoflagellate cysts in surface sediments were investigated in relation to environmental factors in the eastern part of Geoje Island, Korea. Samples were collected from 10 stations in February of 2004 and water temperature and salinity were measured in February, May, September and November of 2004. Total 30 taxa of dinoflagellate cysts were identified representing 19 genera, 28 species and 2 unidentified species. Among these dinoflagellate cysts,Brigantedinium spp. of which relative proportion in the total dinoflagellate cysts was 23.5%, was the most abundant at all stations except St. 1, and was followed bySpiniferites bulloideus (8.6%),Lingulodinium machaerophorum (8.2%) andDiplopsalis lenticula (6.7%). In addition, ellipsoidal cysts of the genusAlexandrium (Alexandrium catenella - tamarense type) andGymnodinium catenatum, known to be causative organisms for PSP, occurred with high concentrations.Scrippsiella trochoidea was also found; however, its cyst concentration was low. Generally, species composition in the study area was similar to these reported from Jinhae Bay and Busan Harbor and several dinoflagellate cysts reflected the eutrophic condition. Cyst distribution in the eastern part of Geoje Island seems to be influenced by the Tsushima Warm Current flowing from the southwest. The mean water temperature was 12.0°C in February, 14.7°C in May, 20.9°C in September and 17.2°C in November, which was most favorable forAlexandrium spp. growth. The abundances of dinoflagellate cysts ranged from 528 to 2,834 cysts/g dry sediment. Higher concentrations were recognized in sediments of west area of the Jisimdo than at other stations. The cyst composition of this area was closely related to these of Jinhae Bay and Busan Harbor from which currents flow into this area. Higher cyst concentration in the west area of Jisimdo might be due to formation of the gyre.

The distribution of sterols and organic-walled dinoflagellate cysts in surface sediments of the North-western Adriatic Sea (Italy)

The distributions of sterols and organic-walled dinoflagellate cysts (dinocysts) in five NW Adriatic Sea surface sediment samples were investigated. Samples are representative of areas differently influenced by freshwater inputs, mainly coming from the Po River. All the investigated samples exhibit the same suite of principal sterols, with cholest-5-en-3β-ol (cholesterol), 4α,23,24-trimethyl-5α-cholest-22 E-en-3β-ol (dinosterol), 24-ethylcholest-5-en-3β-ol (sitosterol) and 24-methylcholesta-5,22 E-dien-3β-ol (brassicasterol or epibrassicasterol) displaying the highest concentrations and relative abundances. The distribution of sterols in the samples is not related to their distance from the coast and/or with the C/N ratios and suggests a prevalent input of marine, autochthonous organic matter in the surface sediments. In particular, the high abundance of dinosterol underlines the importance of dinoflagellate productivity in this area and its contribution to the organic matter in sediments. However, absolute and relative abundances of dinosterol do not follow the trend observed for dinocyst concentrations in the investigated samples, with the exception of Spiniferites spp. cysts and cysts produced by Gonyaulax species.

The seasonal occurrence of dinoflagellate cysts in surface sediments from Koljö Fjord, west coast of Sweden – a note

The opportunistic collection of the flocculent layer, over the spring to late summer seasons, has provided information on the seasonal dinoflagellate cyst sedimentation in Koljö Fjord, on the west coast of Sweden. The dinoflagellate cyst assemblages within the flocculent layer can be both diverse and contain many cysts. The cyst assemblages do not remain constant over time but demonstrate seasonality. Our very limited dataset of six samples suggests that the spring bloom is characterised by round, brown Protoperidinium cysts together with subsidiary Pentapharsodinium dalei and Protoperidinium conicum. The early summer assemblage differs in containing higher proportions of P. dalei with fewer round, brown Protoperidinium cysts together with relatively minor amounts of Lingulodinium polyedrum and Polykrikos schwartzii. The late summer cyst flora is co-dominated by Lingulodinium polyedrum and round, brown Protoperidinium cysts, together with minor amounts of P. dalei and Spiniferites spp. including Spiniferites bentorii. Cyst production within the different species occurs at times of the year when the surface water conditions within the fjord are suitable. This probably reflects, all or in part, the stability of the upper water column, the relative availability of nutrients and the overall phytoplankton productivity.

Calcareous dinoflagellate cysts in surface sediments from the Mediterranean Sea: distribution patterns and influence of main environmental gradients

The distribution of calcareous dinoflagellate cysts in surface sediments from the Mediterranean Sea was quantitatively analysed. The samples contain 11 cyst species and the vegetative coccoid Thoracosphaera heimii. Cyst abundance increases towards the deeper parts of the basins and is generally higher in the eastern Mediterranean Sea. Three major distribution characteristics exist: (1) different assemblages in oceanic and neritic regions, (2) little agreement with the associations of areas studied so far like the Atlantic Ocean, and (3) a unique oceanic assemblage in the eastern Mediterranean Sea. A gradual change in cyst assemblages from the western to the eastern Mediterranean Sea was observed and statistically compared with the main environmental gradients in the upper water column. Temperature, nitrate concentration and possibly salinity appear to be the most important factors controlling cyst production. Three groups containing cysts with similar environmental preferences can be distinguished: (1) an eastern Mediterranean group related to relatively high temperature and salinity but low nitrate concentration, (2) a group of more or less consistently abundant cosmopolitan species tolerating or even preferring relatively low temperature and salinity but high nitrate concentration, and (3) a group containing species that are possibly adapted to neritic environments and have probably been transported from coastal areas into the studied regions. In contrast to other calcareous plankton, calcareous dinoflagellate cysts correlate strongly with the main environmental gradients in the Mediterranean Sea, bearing a high potential for palaeoenvironmental reconstructions.

Influence of benthic and pelagic environmental factors on the distribution of dinoflagellate cysts in surface sediments along the Swedish west coast

Abundance and frequency of dinoflagellate cysts in 19 surface sediment samples from the northern part of the Swedish west coast has been related to physical and chemical characters of the sediment, hydrography of the overlying water column, and plankton species data from the area. Density of cysts varied between 5000 and 101 000 cysts g -1 dw, and the most commonly encountered species were Lingulodinium polyedrum and Protoceratium reticulatum. In all, 46 environmental variables were tested for their relation to dinoflagellate cyst densities, proportion of autotrophic and heterotrophic taxa, and individual species distribution and frequency. The outcomes of multivariate analyses, projection to latent structures (PLS) and canonical correspondence analysis (CCA) were consistent with each other and the actual cyst count. The density of the total cyst assemblage (>90% autotrophic taxa) was primarily related to surface temperature, macronutrients, and inversely to phytoplankton competitors, such as diatoms. The abundance of heterotrophic taxa was governed by the preferences of their prey, i.e. diatom-favourable conditions, and, in most cases, higher propor- tions of heterotrophic taxa were found at well-mixed sites. Some possible effects of anthropogenic contaminants were also noted. Several taxa showed distinct distribution patterns with respect to the environmental variables. A discrepancy between the species constituting the planktonic and the benthic community was revealed when data from 6 yr of plankton monitoring was compared to the data on distribution of dinoflagellate cysts. In particular, cyst-forming species were only a minor part of the plankton, suggesting that these dinoflagellates spend much of their life in the sediments.

Distribution of organic-walled dinoflagellate cysts in surface sediments of the Southern Ocean (eastern Atlantic sector) between the Subtropical Front and the Weddell Gyre

Thirty-two surface sediment samples from the Southern Ocean (eastern Atlantic sector), between the Subtropical Front and the Weddell Gyre, were investigated to provide information on the distribution of modern organic-walled dinoflagellate cysts in relation to the oceanic fronts of the Antarctic Circumpolar Current (ACC). A clearly distinguishable distribution pattern was observed in relation to the water masses and fronts of the ACC. The dinoflagellate cysts of species characteristic of open oceanic environments, such as Impagidinium species, are highly abundant around the Subtropical Front, whereas south of this front, cosmopolitan species such as Nematosphaeropsis labyrinthus and the cysts of Protoceratium reticulatum characterise the transition from subtropical to subantarctic surface waters. The subantarctic surface waters are dominated by the cysts of heterotrophic dinoflagellates, such as Protoperidinium spp. and Selenopemphix antarctica. The cysts of Protoperidinium spp. form the dominant part of the assemblages around the Antarctic Polar Front, whereas S. antarctica concentrations increase further to the south. The presence of S. antarctica in sediments of the Maud Rise, a region of seasonal sea-ice cover, reflects its tolerance for low temperatures and sea-ice cover. A previously undescribed species, Cryodinium meridianum gen. nov. sp. nov., has a restricted distribution pattern between the Antarctic Polar Front and the ACC–Weddell Gyre Boundary.

Dinoflagellate cyst assemblages in surface sediments of the Laptev Sea region (Arctic Ocean) and their relationship to hydrographic conditions

AbstractThe occurrence and distribution of dinoflagellate cysts in surface sediments from the Laptev Sea shelf and the adjacent continental margin have been studied in relation to surface water conditions. Assemblages were interpreted by visual inspection and Q‐mode factor analysis. The inner Laptev shelf is a type‐area for polar environments because of the near absence of relatively warm waters from the Pacific or Atlantic oceans and an extensive seasonal sea‐ice cover. Assemblages are of low diversity and are dominated by the cold water taxon Islandinium minutum and related morphotypes. The common occurrence of distinctive polykrikoid cyst morphotypes is an indicator of polar environments. Furthermore, a strong supply of fresh water in summer influences the surface water conditions, and is a major factor controlling the occurrence and distribution of dinoflagellate cysts. The dinoflagellate cysts Nematosphaeropsis labyrinthus and Operculodinium centrocarpum are restricted to the continental margin, suggesting a relation to the inflow of relatively warm Atlantic waters along the Eurasian continental margin. An abundance maximum of Brigantedinium spp. at the shelf break is related to the mean position of the marginal ice zone. Copyright © 2001 John Wiley & Sons, Ltd.

Distribution of organic‐walled dinoflagellate cysts in surface sediments from transects across the Polar Front offshore southeast Greenland

AbstractThe Polar Front along the southeast Greenland Margin denotes the contrasting hydrographic properties of the polar and Atlantic water masses on either side. The remains of planktonic organisms in underlying sediments are expected to reflect these contrasts. To test this, we quantitatively analysed the organic‐walled dinoflagellate cyst (dinocyst) assemblages in surface sediments from transects across the present‐day Polar Front on the southeast Greenland Margin.Proportional differences are found between the composition of the dinocyst assemblages on either side of the Polar Front. The influence of polar water can be traced in the dinocyst record as high abundances of Algidasphaeridium? minutum and the presence of Pentapharsodinium dalei. The influence of Atlantic water is reflected in the presence of Operculodinium centrocarpum and Selenopemphix quanta. All samples include taxa from both environments, but the quantitative composition of the cyst assemblages clearly reflects the hydrographic features of the overlying surface water masses. Copyright © 2001 John Wiley & Sons, Ltd.

Distribution of dinoflagellate cysts in surface sediments from the Yellow Sea and East China Sea

The distribution of dinoflagellate cysts in surface sediment samples of the Yellow Sea and East China Sea has been examined from 48 samples. Emphasis has been placed on ellipsoidal cysts of the genus Alexandrium. Results show two concurrent cyst distribution trends in latitudinal and longitudinal directions. In the latitudinal trend, cysts are most abundant north of 34°N in the Yellow Sea, where Spiniferites bulloideus (Deflandre et Cookson) Sarjeant, and ellipsoidal Alexandrium cysts generally dominate. Cyst concentration decreases towards both sides of the northern East China Sea in a longitudinal direction. Various factors such as cyst production, particle size of sediment and sedimentation rates may contribute to the dinoflagellate cyst distribution in the Yellow Sea and northern East China Sea. The protoperidinioid/gonyaulacoid (P/G) ratio, which is considered to increase in proportion with increasing primary production, is of limited use in comparing with other areas because its value remains high in both high and lower primary production areas in our study.