Dinoflagellate Cyst Associations Research Articles

Environmental control of interannual and seasonal variability in dinoflagellate cyst export flux over 18 years in the Cape Blanc upwelling region (Mauritania)

The increasing threat of anthropogenic environment and climate change amplifies the urgency to investigate the effect of these changes on marine ecosystems. We provide information about the export flux of organic-walled dinoflagellate cysts between 2003 and 2020 in the upwelling ecosystem off Cape Blanc (Mauritania), one of the world’s most productive regions. We compared the cyst export flux with variability in environmental parameters, such as wind speed, wind direction, dust emission, sea surface temperature (SST), SST difference between trap location and open ocean (SSTa), and chlorophyll-a concentration. This information is valuable to determine the ecological signal of dinoflagellate cysts that could be applied in recent and paleo records. The total export production of dinoflagellate cysts fluctuated between 0 - 1.18 x 105 cysts m-2 d-1 for the heterotrophs and 0 - 1.06 x 104 cysts m-2 d-1 for the photo-/mixotrophs. The export productions of both groups were in line with changes in upwelling intensity, which in most years, intensified in spring - summer. Dinoflagellate cyst association was dominated by heterotrophic taxa that formed an average of 94% of the association throughout the sediment trap record. A strong interannual variation in the cyst export fluxes, as well as the association composition was observed in the record. We identified five groups that showed comparable variability in export production with changes in environmental conditions: (1) maximal upwelling; Echinidinium delicatum/granulatum, E. transparantum/zonneveldiae, Echinidinium spp., Trinovantedinium spp., and Protoperidinium latidorsale, (2) combined maximal upwelling and dust input; Archaeperidinium spp., P. americanum, P. stellatum, and P. subinerme, (3) upwelling relaxation; Gymnodinium spp. and L. polyedra, (4) warm surface waters; Bitectatodinium spongium and Protoceratium reticulatum, (5) species with no specific relationship to the studied environmental variables; Brigantedinium spp., E. aculeatum, Impagidinium aculeatum, P. conicum, P. monospinum, Pentapharsodinium dalei, and Spiniferites spp. The sediment trap record documented a gradual shift in the cyst taxa association that co-occurred with the gradual increase of Saharan dust input to the region, notably after 2008. The cyst association contained five photo-/mixotrophic taxa that were formed by potentially toxic dinoflagellates. The latter could cause threats to the socio-economy of coastal communities.

Late Quaternary palaeoenvironmental evolution and sea level oscillation of Santa Catarina Island (southern Brazil)

Abstract. Sea level oscillation during the Quaternary played a major role in the geomorphology and vegetation dynamics of coastal areas in southern Brazil, encompassing ecosystems that often have a unique biodiversity. Understanding the natural evolution of these areas is essential for decision making regarding land use regulations towards sustainable development, as well as to preserve the uniqueness of the coastal ecosystems. The southern Brazil coastal plain is formed by marine, transitional and continental Quaternary deposits controlled by past variations of the sea level. These variations shaped the coastal landscape and influenced the development of different Atlantic rainforest formations, such as mangroves and restingas. In particular, the restinga formation corresponds to a specific ecosystem that covers sandy soils of marine and fluvial–marine origin formed during the Quaternary on the Brazilian coastal plain. In this contribution, we present high-resolution palynological and stable isotope data from a Holocene core retrieved from the coastal plain of Santa Catarina Island (southern Brazil). We were able to identify four different environmental zones for the last 6520 yr BP. The first zone (6520–2920 cal yr BP) is characterized by a lagoon with large marine-water influence. Notably, the observed dinoflagellate cyst association suggests that marine waters entering the region had their origin in the relatively warm and saline Brazil Current waters. During the second zone (2920–1520 cal yr BP), marine-water contribution to the lagoon decreased until it became disconnected from the sea. The third zone (1520–550 cal yr BP) was marked by the decrease of the water level until it dried out and led to the colonization of herbaceous vegetation over the palaeo-lagoon. The last zone (550 cal yr BP–recent) is characterized by the consolidation of the coastal-plain Atlantic rainforest (restinga vegetation). Our results form an example of the strong sensitivity of southern Brazilian ecosystem change caused by relative sea level variations. As such, this study might contribute to the debate about the potential effects of current climate change induced by global sea level variations.

Middle Miocene (Serravallian; upper Badenian–lower Sarmatian) dinoflagellate cysts from Bad Deutsch-Altenburg, Vienna Basin, Austria

Middle Miocene (Serravallian; upper Badenian–lower Sarmatian) strata recovered in 10 cored boreholes (83 samples) from Bad Deutsch-Altenburg, Vienna Basin, Austria, were analysed palynologically for the first time. The strata belong to the Rabensburg Formation of the Baden Group. The lateral distribution of the boreholes in reference to a Mesozoic ridge makes this area interesting for studying various aspects such as distribution of deposits, stratigraphy and palaeoenvironmental reconstruction. A diverse and well-preserved in situ dinoflagellate cyst association has been identified. Middle Miocene age-diagnostic species including Cannosphaeropsis passio, Cerebrocysta poulsenii, Habibacysta tectata, Labyrinthodinium truncatum, Operculodinium? borgerholtense and Unipontidinium aquaeductum are recorded. Their occurrences allow correlation with dinoflagellate cyst biozonations on a regional scale. Based on the identified dinoflagellate cysts and by correlation with calcareous nannoplankton and ostracods, from the same set of samples, a Serravallian age – corresponding to a late Badenian and early Sarmatian age (regional Paratethys stages) – is confirmed. Reworked (Cretaceous and Paleogene) dinoflagellate cyst assemblages, also well preserved, were recorded abundantly from boreholes HA 521 and HA 573 (south-west of the Mesozoic ridge). In accordance with ostracods, the Badenian–Sarmatian boundary can be traced in the upper part of borehole HA 66 based on an abrupt change in the dinoflagellate cyst assemblages. The upper Badenian strata were deposited in a coastal to inner shelf environment with terrigenous (siliceous sand and clay) and carbonate sediments. The recorded dinoflagellate cysts reflect marine, tropical to warm-temperate climatic conditions. The composition of the recorded dinoflagellate cyst assemblages is very close to that of the Middle Miocene assemblages of the Mediterranean, indicating water exchanges between the Central Paratethys and the Mediterranean during the late Badenian (early Serravallian).

Late Triassic dinoflagellate cysts from the Northern Carnarvon Basin, Western Australia

The Late Triassic radiation of cyst-forming dinoflagellates in the Southern Hemisphere is investigated in the Northern Carnarvon Basin, Western Australia. This major depocentre, situated on the southern margin of the Tethys Ocean, accumulated extensive deltaic and shallow marine successions at this time, that frequently host early dinoflagellate cyst assemblages. Numerous petroleum exploration wells in the basin have penetrated the fluvially dominated Mungaroo Formation and shallow marine Brigadier Formation, of Anisian–Norian and Rhaetian ages, respectively. Consequently, huge numbers of cuttings and sidewall core samples from these northwest prograding deltaic systems are available for study. Many of the dinoflagellate cysts from the Mungaroo and Brigadier formations have not been taxonomically formalised, including many forms that are used in open nomenclature within the oil and gas industry. This study formally documents these occasionally abundant and diverse dinoflagellate cyst assemblages with the aim of providing a consistent taxonomic framework for future work on the Upper Triassic successions of the Northern Carnarvon Basin. This will aid the recognition of individual flooding events via their characteristic palynomorph signatures and help to build on significant recent advances in regional sequence stratigraphy. One new genus, 14 new dinoflagellate cyst species and one new subspecies are described from the most diverse Late Triassic dinoflagellate assemblage yet published. A further nine genera and 15 dinoflagellate species are also recorded from the Carnian–Rhaetian R. wigginsii, W. listeri, H. balmei, R. rhaetica and D. priscum dinoflagellate zones. The documented assemblages are not only significant biostratigraphically, but it is also postulated that high diversity Triassic dinoflagellate cyst associations were paleoclimatically controlled, and were likely confined to the temperate and cool temperate paleolatitudes.

The Middle Jurassic palynostratigraphy of the northern Lusitanian Basin, Portugal

A composite largely Middle Jurassic succession spanning the Toarcian-Aalenian transition to the lowermost Bathonian exposed at Cabo Mondego and Sao Giao in the northern Lusitanian Basin, western Portugal, was examined palynologically. The 129 samples are correlated to ammonite biozones spanning Pleydellia aalensis to Zigzagiceras zigzag. The Cabo Mondego succession comprises the type section of the Cabo Mondego Formation and spans virtually the entire interval studied. This is a significant interval because it includes the Global Stratotype Section and Point (GSSP) and the Auxiliary Stratigraphical Section and Point (ASSP) for the Bajocian and Bathonian stages respectively. The Cabo Mondego Formation largely yielded relatively abundant palynomorph associations in the 68 productive samples recovered. By contrast, the Povoa da Lomba Formation at Sao Giao only includes the Toarcian-Aalenian transition; the 21 productive horizons produced sparse assemblages. The uppermost Toarcian to lowermost Bajocian is characterised by a low diversity dinoflagellate cyst association, typified by Nannoceratopsis. Above this is a markedly more diverse assemblage. This influx, in the Witchellia laeviuscula ammonite biozone AB, represents a global evolutionary radiation which may be linked to sea level rise. The trend of increasing dinoflagellate cyst diversity continued at the Bajocian-Bathonian transition. The Middle Jurassic dinoflagellate cyst assemblages of the Lusitanian Basin are significantly less diverse than coeval palynobiotas from eastern and northern Europe, and the Arctic. The Toarcian Oceanic Anoxic Event (T-OAE) profoundly inhibited cyst-forming dinoflagellates in this depocentre, and the recovery was protracted. Hence the T-OAE may have suppressed dinoflagellate cyst diversity well into the Middle Jurassic. This phenomenon may have been exacerbated by the absence of typically Arctic taxa through latitudinal controls and/or global cooling during the early Aalenian. These low levels of dinoflagellate cyst species richness may also be related to the palaeogeography of the Lusitanian Basin. This relatively isolated deepwater depocentre close to the Proto Atlantic, may have precluded extensive biotal exchange with the widespread shelfal areas of the western Tethys. The absence of Dissiliodinium giganteum in the Lusitanian Basin is consistent with this scenario. The pollen and spores observed in this study are typical of Middle Jurassic assemblages worldwide. Araucarian pollen, largely Callialasporites, diversified and became prominent during the Aalenian.

Distribution of Albian dinoflagellate cyst associations along a proximal–distal transect across the Iberian margin

The analysis of Albian dinoflagellate cysts, or dinocysts, along an inshore–offshore transect across the Iberian Margin reveals the environmental influence on the assemblages composition. Two biodiversity metrics are used to analyze changes in the assemblage structure. The stress associated to environmental instability is identified as the main factor influencing the dinocyst biodiversity. The relative frequency distribution of dinocysts is analyzed to identify associations of taxa sharing similar environmental preferences. Seven dinocyst associations are identified. The environmental affinities of the seven dinocyst associations are inferred from lithological data and assemblage structure. Association 1 dominated the most proximal and unstable environments. Associations 2 and 3 characterized inner-middle neritic environments. Taxa in the Association 2 preferred stable mesotrophic conditions, whereas, taxa in the Association 3 were tolerant to variations in salinity and nutrient input. Associations 4 and 5 are indicative of open marine distal environments. Taxa in the Association 4 were tolerant to limited environmental fluctuations. Taxa in the Association 5 were restricted to stable open marine conditions. The widespread distribution of taxa in the Association 6 is interpreted as revealing their ubiquitous character. The taxon in the Association 7 is considered as cosmopolitan because its widespread distribution was conditioned to nutrients availability.

Species-specific sensitivity of dinoflagellate cysts to aerobic degradation: A five-year natural exposure experiment

Post-depositional sedimentary dinoflagellate cyst associations undergo species-selective degradation under oxic conditions. However, there is little known about the temporal relationship between oxygen concentration and bulk dinocyst degradation rate over the time scale of several years, and if this degradation is mainly microbial or chemical. Whilst the overall sensitivity of heterotrophic dinoflagellate cysts is well documented, sensitivity differences within this group have not been studied. Here we examine the rates of cyst degradation of heterotrophic species over short temporal scales across an anoxic–oxic gradient. Sediment with a known dinoflagellate cyst association largely dominated by heterotrophic dinoflagellates, were connected to trap arrays at two different locations, Cap Blanc (NW Africa) and Gotland Basin (central Baltic Sea) and exposed to four different ambient oxygen concentrations representing a complete oxic gradient from 5.1mL/L to sulphate bearing anoxic waters. Two treatments of either gauze or dialyse membrane in triplicate were established to investigate the effects of chemical or bacterial degradation. Cyst loss was significant at oxic settings, rapidly occurring within the first year of exposure (32%) whereas no significant degradation was observed for suboxic and anoxic exposures. Compiling the degradation rates of individual species under the different exposure settings reveals an overall species sensitivity ranking amongst cysts of heterotrophic species. Species of average resistance: Bitectatodinium spongium, Brigantedinium spp., Echinidinium spp., Echinidinium aculeatum, and Gymnodinium trapeziforme. Species more resistant than average: Stelladinium robustum and Trinovantedinium applanatum. We observe that oxic degradation of cysts of heterotrophic dinoflagellates is fast and selective with maximal cyst association changes during the first year of oxic exposure. These aspects have to be taken into account in palaeoenvironmental and palaeoceanographic reconstructions where bottom/pore water conditions of the upper sediments are oxygenated.

Similarities of the K/Pc dinoflagellate cyst associations between South Atlantic and Indian proto-oceans

In this contribution we present the composition of the Late Cretaceous / Paleocene dinoflagellate cyst assemblages found in the Pelotas Basin, southern Brazil in order to provide a first paleobiogeographical comparison between this location, India and other former Gondwana continents: South America (Argentina and Uruguay), Africa (Nigeria and Western Ghana), Antarctica, Australia, and New Zealand. A total of 13 taxa, some endemic and other cosmopolitan were identified. The paleoenvironment of the Gondwana former members basins, as previously presented and attested by the dinoflagellate cysts are marginal marine nearshore, varying from neritic to shallow neritic and lagoonal or coastal swamps, which permitted the deposition of sediments in anoxic marine conditions. The present analysis of similarity between K/Pc dinoflagellate cyst associations allowed the establishment of paleobiogeographic distribution.

Marine environment, vegetation and land use changes during the late Holocene in South Kalimantan and East Java reconstructed based on pollen and organic-walled dinoflagellate cysts analysis

The pollen, spore and organic-walled dinoflagellate cyst associations of two marine sediment cores from the Java Sea off the mouths of Jelai River (S Kalimantan) and Solo River (E Java) reflect environment and vegetation changes for the last ca 3500years. A decline in primary forest taxa (e.g. Agathis, Allophylus, Dacrycarpus, Dacrydium, Dipterocarpaceae, Phyllocladus and Podocarpus) suggest that the major change in vegetation is caused by forest canopy disturbance possibly as a consequence of human activity. The successive increase in pollen of pioneer tress/shrubs and herb taxa (e.g. Acalypha, Ficus, Macaranga/Mallotus, Trema, Pandanus) indicate the development of secondary vegetation. In Java these changes started much earlier (ca at 2950calyr BP) than in Kalimantan (ca at 910calyr BP) and seem to be more severe. Changes in the marine realm, reflected by the dinoflagellate cyst association, correspond to the changes in vegetation on land. They reflect a gradual change from relatively well ventilated to more hypoxic bottom/pore water conditions in a more eutrophic environment. Near the coast of Java, the shift of the water trophic status took place between ca 820 and 500calyr BP, while near the coast of Kalimantan it occurred as late as at the beginning of the 20th century. We observe an increasing amount of the cysts of Polykrikos schwartzii, P. kofoidii, Lingulodinium machaerophorum, Nematosphaeropsis labyrinthus and Selenopemphix nephroides at times of secondary vegetation development on land, suggesting that human induced terrestrial changes possibly affected the marine environment as well, most likely through increased eutrophication and pollution.

High-resolution multi-proxy reconstruction of environmental changes in coastal waters of the Java Sea, Indonesia, during the late Holocene

ABSTRACTTo obtain insight into the natural variability of the coastal ecosystems off southern Kalimantan, late Holocene environmental conditions between ca. 2850 and 990 cal yr BP in the Java Sea were investigated. A 134-cm-long sediment core collected ∼50 km off the Pembuang River mouth was analysed for organic-walled dinoflagellate cysts, pollen/spores and biogeochemical parameters, e.g. organic carbon (Corg), total nitrogen (N) and calcium carbonate (CaCO3) as well as carbon and nitrogen stable isotope composition (δ13C, δ15N). Sediments consist of mixed terrestrial as well as marine organic matter, are characterised by low nutrient uptake and suggest generally low river discharge that is supported by very low pollen and spore concentrations (256 pollen grains cm−3 and 20 spores cm−3 at maximum, respectively). Foraminifera and coccolithophores dominated the plankton over cyst-producing dinoflagellates and diatoms. Dinoflagellate cyst assemblages are composed mainly of oxidation-resistant species of the genera Operculodinium and Spiniferites with a minor contribution of Impagidinium (mainly I. strialatum). The percentages of round brown and peridinioid cysts are low and decrease from the bottom of the core to the top. Palynological and biogeochemical data appear well correlated and synchronously reflect changes in the marine environment. It is reconstructed that after ca. 2480 cal yr BP, bottom waters became increasingly ventilated. A typical open-water dinoflagellate cyst association is gradually replaced by a more coastal association between ca. 2480 and 1530 cal yr BP that is most likely attributed to El Niño-induced seasonal differences between dry and wet periods of the year. After 1530 cal yr BP, a more pronounced influence of the Pembuang River is indicated by an increase in δ15N and decreased δ13C which is supported by the occurrence of nutrient-sensitive Lingulodinium machaerophorum and Nematosphaeropsis labyrinthus. The overall results indicate short-scale local environment fluctuations attributed to abiotic factors.

Latest Quaternary palaeoceanographic change in the eastern North Atlantic based upon a dinoflagellate cyst event ecostratigraphy

The analyses of dinoflagellate cyst records, from the latest Quaternary sediments recovered from DSDP Core 610A taken on the Feni Ridge in the southern Rockall Trough, and part of core MD01-2461 on the continental margin of the Porcupine Seabight in the eastern North Atlantic Ocean, has provided evidence for significant oceanographic change encompassing the Last Glacial Maximum (LGM) and part of the Holocene. This together with other published records has led to a regional evaluation of oceanographic change in the eastern North Atlantic over the past 68 ka, based upon a distinctive dinoflagellate event ecostratigraphy. These changes reflect changes in the surface waters of the North Atlantic Current (NAC), and perhaps the deeper thermohaline Atlantic Meridional Overturning Circulation (AMOC), driving fundamental regime changes within the phytoplanktonic communities. Three distinctive dinoflagellate cyst associations based upon both factor and cluster analyses have been recognised. Associations characterised by Bitectatodinium tepikiense (between 61.1 ± 6.2 to 13.4 ± 1.1 ka BP), Nematosphaeropsis labyrinthus (between 10.5 ± 0.3 and 11.45 ± 0.8 ka. BP), and the cyst of Protoceratium reticulatum (between 8.5 ± 0.9 and 5.2 ± 1.3 ka. BP) indicate major change within the eastern North Atlantic oceanography. The transitions between these changes occur over a relatively short time span (c.1.5 ka), given our sampling resolution, and have the potential to be incorporated into an event stratigraphy through the latest Quaternary as recommended by the INTIMATE (INTegrating Ice core, MArine and TErrestrial records) group. The inclusion of a dinoflagellate cyst event stratigraphy would highlight changes within the phytoplankton of the North Atlantic Ocean as a fully glacial world changed to our present interglacial.

Dinoflagellate cyst distribution in the oligotrophic environments of the Gulf of Aqaba and northern Red Sea

Abstract Oligotrophic environmental systems form a major part of the marine aquatic environments on earth. Compared to mesotrophic and eutrophic environments extremely little information is available about the relationship between the distribution of organic-walled dinoflagellate cysts and physical and biological gradients in the upper water column. Here we present the first comprehensive study of the modern geographic distribution of organic-walled dinoflagellate cysts in the oligotrophic environments of the northern Red Sea and Gulf of Aqaba. We show that sediments of both regions have characteristic dinoflagellate cyst associations consisting of both heterotrophic and phototrophic species of which the latter, including both autotrophic and mixotrophic species, form the major part of the associations in both regions. The upper water environment of the Gulf of Aqaba is characterized by slightly enhanced nutrient concentrations compared to the Red Sea, due to water column mixing in winter. Its phytoplankton composition is dominated by pico- and ultra-plankton and a slight higher amount of eukaryotes compared to northern Red Sea. Its sedimentary cyst associations are characterized by higher relative and absolute abundances of the species Brigantedinium spp., Votadinium calvum, Echinidinium spp., Lingulodinium machaerophorum, Spiniferites spp., Spiniferites bentorii, Spiniferites membranaceus and Spiniferites mirabilis. Sediments of the northern Red Sea are characterized by high relative abundances of Impagidinium aculeatum, Impagidinium sphaericum, Operculodinium israelianum, Operculodinium longispinigerum, Operculodinium centrocarpum, cysts of Pentapharsodinium dalei, and Selenopemphix nephroides. A positive relationship between the distribution of the heterotrophic species Brigantedinium spp., Echinidinium spp. and V. calvum with the occurrence of other eukaryotic groups such as e.g. diatoms is documented. The distribution of S. nephroides cannot be related to the presence of diatom occurrences and it is suggested that the distribution of food sources other than diatoms affects its distribution. We document a positive relationship between the sedimentary distribution of the phototrophic dinoflagellate species L. machaerophorum and Spiniferites species and the abundance of the cyanobacteria Synechococcus in the water column. Since Synechococcus is known to be a potential prey of Lingulodinium polyedrum and members of the Gonyaulax spinifera complex (the motile forms producing these cysts) we suggest a possible cyst distribution–prey relationship of mixotrophic dinoflagellates.

Short term climate variability during “Roman Classical Period” in the eastern Mediterranean

To obtain insight into character and potential forcing of short-term climatic and oceanographic variability in the southern Italian region during the “Roman Classical Period” (60 BC–AD 200), climatic and environmental reconstructions based on a dinoflagelate cyst record from a well dated site in the Gulf of Taranto located at the distal end of the Po-river discharge plume have been established with high temporal resolution. Short-term fluctuations in accumulation rates of the Adriatic Surface Water species Lingulodinium machaerophorum, the freshwater algae Concentricystes and species resistant to aerobic degradation indicate that fluctuations in the trophic state of the upper waters are related to river discharge of northern and eastern Italian rivers which in turn are strongly related to precipitation in Italy. The dinoflagellate cyst association indicates that local sea surface temperatures which in this region are strongly linked to local air temperatures were slightly higher than today. We reconstruct that sea surface temperatures have been relatively high and stable between 60 BC–AD 90 and show a decreasing trend after AD 90. Fluctuations in temperature and river discharge rates have a strong cyclic character with main cyclicities of 7–8 and 11 years. We argue that these cycles are related to variations of the North Atlantic Oscillation climate mode. A strong correlation is observed with global variation in Δ 14C anomalies suggesting that solar variability might be one of the major forcings of the regional climate. Apart from cyclic climate variability we observed a good correlation between non-cyclic temperature drops and global volcanic activity indicating that the latter forms an additional major forcing factor of the southern Italian climate during the Roman Classical Period.

Callovian (Middle Jurassic) dinoflagellate cysts from the Algarve Basin, southern Portugal

The palynology of three Callovian (Middle Jurassic) limestone-marl successions from the Algarve Basin in southern Portugal was studied. These localities are Baleeira Harbour, Mareta Beach and Telheiro Quarry; they provide a composite. succession, tied to ammonite zones, through the Lower, Middle and Upper Callovian from the western and eastern subbasins of the Algarve Basin. The three sections generally yielded relatively abundant marine and continental palynofloras. Diversity is low to moderate and the dinoflagellate cyst associations are dominated by Ctenidodinium spp., the Ellipsoidictyum/Valensiella group, Gonyaulacysta jurassica subsp. adecta, Korystocysta spp., Meiourogonyaulax spp., Pareodinia ceratophora, Sentusidinium spp., Surculosphaeridium? vestitum and Systematophora spp. Some intra-Callovian marker bioevents were recorded; these include the range bases of Ctenidodinium ornatum, Gonyaulacysta eisenackii, Korystocysta pachyderma, Mendicodinium groenlandicum, Rigaudella spp. and Surculosphaeridium? vestitum. The occurrences of Endoscrinium acroferum and Impletosphaeridium varispinosum in the Early to Middle Callovian of Mareta Beach and Telheiro Quarry are also characteristic of this interval. At Baleeira Harbour, the presence of Ctenidodinium continuum and Gonyaulacysta centriconnata in the Peltoceras athleta Zone confirms the Late Callovian age of this section. The successions studied were deposited in restricted infralittoral neritic marine environments which lack deep water circulation, and possibly represent restricted embayments. The relatively low diversity nature of the dinoflagellate cyst assemblages appears to be largely due to the highly enclosed nature of this depocentre. Many Callovian index dinoflagellate cyst taxa which are found in northwest Europe are absent in the Algarve Basin. These forms may have been intolerant of enclosed palaeoenvironments which have restricted or no deep circulation. The Callovian marine palynofloras from the Algarve Basin compare well to the few other published records from the Iberian Peninsula of this age. However they are significantly less diverse than coeval floras from elsewhere in the extensive Mid Latitude Callovian phytoprovince. Many typically Callovian dinoflagellate cysts are cosmopolitan, however some provincialism is clearly manifested. The Arctic and Austral Callovian phytoprovinces are characterised by key endemic taxa such as Paragonyaulacysta retiphragmata and Ternia balmei, which are not present in the Algarve Basin and are assumed to have been polar forms.

The Benguela upwelling related to the Miocene cooling events and the development of the Antarctic Circumpolar Current: Evidence from calcareous dinoflagellate cysts

Sediment samples from ODP Site 1085 were investigated in order to obtain more information on the initiation and development of the Benguela upwelling system during the middle and upper Miocene. In particular, our intent was to establish the causes of the upwelling as well as the response of the upwelling regime to the development of the Antarctic Circumpolar Current. Based on changes in the calcareous dinoflagellate cyst association, we found an initial increase of the dinoflagellate cyst productivity, probably related to the initiation of upwelling about 11.8 Ma ago. Two distinct increases in cyst productivity in conjunction with temperature decreases of the upper water masses reflect upwelling pulses off Namibia and occur at the end of the Miocene cooling events Mi5 (about 11.5 Ma) and Mi6 (about 10.5 Ma). Both cooling events are associated with an ice volume increase in Antarctica and are thought to have led to an increase in southeasterly winds, possibly causing these two upwelling pulses. We demonstrate a decrease in dinoflagellate cyst productivity and enhanced terrigenous input via the Orange River after the Mi5 event. At about 11.1 Ma, the dinoflagellate cyst productivity increases again. The polar cyst species Caracomia arctica occurs here for the first time. This implies an influence of subantarctic mode water and therefore a change in the quality of the upwelling water which allowed the Benguela upwelling to develop into modern conditions. From about 10.4 Ma, C. arctica forms a permanent part of the association, pointing to an establishment of the upwelling regime.

The Jurassic (Pliensbachian to Kimmeridgian) palynology of the Algarve Basin and the Carrapateira outlier, southern Portugal

The palynology of the Jurassic (Upper Pliensbachian to Lower Kimmeridgian) fill of the Algarve Basin and the Carrapateira outlier, southern Portugal was investigated. Samples were collected from Armação Nova Bay, Mareta Beach, Cilheta Beach and the Carrapateira outlier. At Armação Nova Bay the Upper Pliensbachian–Lower Toarcian succession proved barren, or yielded sparse, non age-diagnostic palynomorphs. Dinoflagellate cysts are confined to the Upper Bajocian to Upper Callovian sedimentary rocks exposed at Mareta and Cilheta beaches and the Lower Kimmeridgian strata of the Carrapateira outlier. At Mareta Beach, the Upper Bajocian, Bathonian and Callovian produced relatively low to moderate diversity dinoflagellate cyst assemblages. Several key bioevents confirm the Bathonian and Callovian ages of the succession; no age-significant Late Bajocian bioevents were noted. The Upper Callovian of Cilheta Beach yielded moderately diverse dinoflagellate cyst associations dominated by Ctenidodinium spp. Key Late Callovian bioevents confirm the age of this succession. Many familiar marker forms known from northwest Europe were not encountered. No typically Arctic forms were recovered throughout the Upper Bajocian to Callovian of this part of the Algarve Basin. It is clear that there was no significant Late Bajocian to Late Callovian dinoflagellate cyst provincialism within southern and northern Europe and adjacent regions. The Carrapateira outlier yielded a moderately diverse Early Kimmeridgian dinoflagellate cyst flora. The Early Kimmeridgian age assessment based on corals and foraminifera is confirmed. Amphorula and Histiophora are present; these are typical of the Late Jurassic of the Tethyan Realm, and their presence is consistent with Late Jurassic provincialism within Europe. The relatively low diversity nature of these Late Bajocian to Early Kimmeridgian dinoflagellate cyst floras is probably mainly due to the relatively deep water, partially enclosed depositional setting. The partially enclosed nature of this part of the Algarve Basin and the Carrapateira outlier seems to have prevented the free migration of dinoflagellates between southern Portugal and elsewhere in Europe.

Environmental significance of dinoflagellate cysts from the proximal part of the Po-river discharge plume (off southern Italy, Eastern Mediterranean)

To determine the relationship between region specific dinoflagellate cyst distribution in the Po-river discharge area and oceanic environmental conditions, surface sediments of 48 sites in the middle and distal part of the discharge plume area have been studied. Establishing such a relationship is a prerequisite to create reconstructions of the eutrophication history as well as the palaeoclimatic and palaeoceanography history of the area. Literature based information about the sedimentation rates based on 210Pb dating methods are available for 18 sites. This enables the calculation of cyst accumulation rates of individual cyst species which reflect their cyst production. Correlation of the accumulation rates of individual species with environmental parameters of the upper waters allows us to adapt and refine the ecological characteristics of a selection of cyst species. This latter is trivial since the current concepts on the ecological significance of dinoflagellate cyst have to be revised as a result of the current developments in the dinoflagellate research field. These developments have elucidated that a considerable part of the relative abundance datasets that form the basis for the present day ecological concepts of dinoflagellate cysts might have suffered from so called “closed sum effects” and have been overprinted by early diagenetic processes. The dinoflagellate cyst association reflects both upper and bottom water circulation. Based on the relative abundance data four associations can be distinguished that are characteristic for the major oceanographic settings in the region. (1) River discharge association. This association consists of Echinidinium spp., Lejeunecysta sabrina, Lingulodinium machaerophorum, Polykrikos kofoidii, Polykrikos schwarzii, cysts of Protoperidinium stellatum, Selenopemphix quanta and reworked cysts. These species have high relative abundances in sites where bottom waters are low in oxygen and upper waters are influenced by river discharge waters that are characterized by high productivity and relative low salinity. (2) Warm water association. This association consists of Spiniferites mirabilis, Spiniferites pachydermus, Spiniferites ramosus and Spiniferites spp. which have their highest relative abundances in the sites at the plume margin that are characterized by relative warm upper waters and intermediate chlorophyll- a concentrations. (3) Oxygenated bottom water group. Species of this group; Impagidinium aculeatum, Impagidinium patulum, Impagidinium sphaericum, Operculodinium centrocarpum and Operculodinium israelianum have their highest relative abundances at sites where bottom waters are formed by well ventilated Adriatic Deep Water or Eastern Mediterranean Deep Water. (4) Golfo di Taranto group consisting of round brown cysts produced by Protoperidinium species (grouped as Brigantedinium spp .). The variation in accumulation rates can be related to gradiental changes in the trophic state of the surface waters linked to river outflow. Most species show a positive relationship between cyst production and nutrient/trace element availability in upper waters. No negative correlation between cyst production and nutrient/trace element availability could be documented. Production of Brigantidinium spp., Echinidinium spp., L. sabrina, L. machaerophorum, P. kofoidii/schwarzii, Spiniferites spp., S. mirabilis and S. quanta shows the most pronounced increase with increasing nutrient/trace element availability. These species can be considered as valuable indicators for reconstructing changes in the trophic state of the upper waters within the Po-river area in palaeo-environmental studies.

Preservation and organic chemistry of Late Cenozoic organic-walled dinoflagellate cysts: A review

Within the last decade considerable information has become available on the effects of early diagenesis on the taphonomy of organic-walled dinoflagellate cysts. Here, we review the information currently available on this topic. After discussing organic matter degradation in general, an overview on the effects of different laboratory treatments on the dinoflagellate cyst association is given. Hereafter, the rates and amount of species-selective degradation in modern and fossil natural environments are discussed. It appears that the availability of oxygen in the sediments is the most important diagenetic variable. Some of the modern dinoflagellate cyst species survive thousands of years in well oxygenated sediments and are as such among the most refractory types of organic matter. Most (but not all) of these refractory species are phototrophic gonyaulacoids. However, the refractory cysts form only a part of the modern gonyaulacoid or phototrophic cyst producing taxa. The modern species most vulnerable to degradation are often produced by heterotrophic peridinioids. Again, these vulnerable species form only a part of the heterotrophic species and species with a peridinioid plate configuration. To get insight in the intrinsic properties of the cysts bringing about the selective preservation, we continue with reviewing the understanding of algal cell walls and dinoflagellate cyst walls at the molecular level. The review documents that cysts of Mesozoic age have different preservation characteristics than Late Cenozoic to Modern species. We propose that over long periods, taphonomic processes on a molecular level substantially change the cyst wall macromolecular structure and herewith cyst degradability. Having described the impact of selective preservation on the dinoflagellate cyst assemblages, we continue summarising the methods presently available for the recognition of and correction for this diagenetic overprint. Subsequently, we take advantage of the selective preservation by using it for reconstructing past export production. Since the rates of dinoflagellate cyst degradation are strongly related to the bottom water oxygen concentration, this opens the way for a new proxy to reconstruct deep-ocean oxygen concentrations. The importance of the rate of deep-ocean ventilation within the marine global carbon cycle and its relationship with climate change, make this use of selective dinoflagellate cyst preservation an important though unexpected application.

Integrated stratigraphy and palaeoecology of the Lower and Middle Miocene of the Porcupine Basin

AbstractA high-resolution palynological analysis and a detailed palaeomagnetic study of a marine sequence recovered during IODP Expedition Leg 307 in the Porcupine Basin southwest of Ireland provide new insights into the regional depositional history and palaeoenvironmental evolution during Early Neogene times. The Hole 1318B studied was drilled on the upper slope of the continental margin in a water depth of 409 m, upslope from a province of carbonate mounds (the Belgica mound province). The diverse and well-preserved dinoflagellate cyst associations consist typically of deep neritic and oceanic species, mixed with a neritic component transported from the shelf, reflecting the deep depositional setting at the continental margin. The palaeomagnetic record together with the ranges of key dinoflagellate cyst species constrain the age of the studied sequence between 16.7 Ma and 12.01 Ma, that is, between the late Burdigalian and late Serravallian. The distinct unconformity terminating the Miocene sequence correlates to the global sequence boundary Ser4/Tor1 dated at 10.5 Ma, and represents, according to previous extensive seismic studies, a basin-wide erosional event. The overlying sediments are of Middle Pleistocene or younger age. Downslope from IODP Site 1318, carbonate mounds root on the erosional surface. The dinoflagellate cyst associations from the Porcupine Basin distinctly mirror the global cooling phase following the Middle Miocene Climatic Optimum. Cooling phase Mi3, a short-lived glaciation, is particularly well expressed and here dated at 13.6 Ma. The palynomorph record furthermore indicates a reduction of the productivity and an increase of oceanic oligotrophic species after 14 Ma, suggesting a reduction or perhaps even a shutdown of the upwelling.

The Early and Middle Miocene transgression at the southern border of the North Sea Basin (northern Belgium)

The Lower–Middle Miocene Berchem Formation of northern Belgium is an essentially sandy sequence with a varying glauconite content and often abundant shelly intervals. The formation was deposited in a shallow marine environment and rests unconformably on stiff Rupelian clays or Chattian sands. The lithological recognition of the four members (Edegem Sands, Kiel Sands, Antwerpen Sands and Zonderschot Sands members) of the Berchem Formation solely based on lithological criteria proved to be difficult, especially in boreholes. The geometry of the Formation in the subsurface of northern Belgium remained largely unknown. Diverse and well preserved dinoflagellate cyst associations have been recovered from the four members in seven boreholes and two outcrops, and allow a refinement of the biostratigraphy of these deposits. A Miocene biozonation defined in mid-latitude shallow marine deposits in the Atlantic Coastal Plain of the USA (Salisbury Embayment, Maryland) is readily applicable to this material, and has led to a detailed stratigraphic assessment of each member. Three detailed profiles depicting the distribution of the biozones in the subsurface of northern Belgium allow the reconstruction of the geometry and depositional history of the Berchem Formation. The oldest Miocene deposits are of early Burdigalian age and they testify to a transgression, which invaded Belgium from a north–northwestern direction. The maximum flooding took place during early Serravallian times. The upper boundary of the formation is a major erosional surface of late Serravallian or (slightly) younger age. Copyright © 2005 John Wiley & Sons, Ltd.