Dinoflagellate Cyst Record Research Articles

Record of Early Cretaceous dinoflagellate cysts from well JM-A, Dhansiri Valley of Upper Assam Shelf, India

A palynological study on subsurface Early Cretaceous sediments (1550–1860 m) in well JM-A located in Dhansiri Valley, Upper Assam Shelf has been carried out for determination of age and depositional environment. The palynological investigations resulted into the identification of the characteristic and diversified occurrence of Early Cretaceous dinoflagellate cysts comprising Batioladinium micropodum, Achomosphaera? neptuni, Batiacasphaera asperata, Lagenorhytis sp. cf. L. delicatula, Mendicodinium caperatum and Canningia sp. along with associated dinoflagellate cysts. The significant assemblage of spore-pollen assemblage represented by Cicatricosisporites australiensis, Ceratosporites equalis, Gleicheniidites circinidites, Contignisporites cooksonii, Microcachryidites antarcticus, Podosporites tripakshii and Callialasporites trilobatus has also been recorded. The Early Cretaceous sediments are regarded as Bamangaon Formation in Dhansiri Valley. The occurrence of dinoflagellate cysts suggests marginal marine environment for Bamangaon Formation deposited during the Early Cretaceous period corresponding to the Rift Phase. The Formation overlies the Metamorphic Basement Complex, and it is unconformably overlain by the sediments of Tura Formation of Ypresian (Early Eocene) age, deposited under subtidal to inner shelf environment during the Passive Margin Tectonic Phase.

Danian-Ypresian dinocyst biostratigraphy, fish fauna and depositional environment of the Akli Formation, Barmer Basin, western India

ABSTRACT Herein, we present a diverse record of dinoflagellate cysts from the lignite-associated sedimentary succession (belonging to the Akli Formation) at Sonari Lignite Mine, Barmer Basin, Rajasthan State, western India. The dinoflagellate cyst assemblage implies a Danian to Ypresian age for the investigated succession and argues that the deposition of lignitic sequences along India’s western margin is not coeval. We also identify two vertebrate (dominantly fish-yielding) units within the studied Akli Formation succession. The Ypresian fish genera (mainly represented by dental remains) include Ginglymostoma, Jaekelotodus, Brachycarcharias, Pycnodus and Myliobatis while the Selandian-Thanetian fish dental remains include Dasyatis. A discontinuous distribution of fish fauna during the early Paleogene (based on the temporal and spatial data) within the lignite-associated sedimentary successions of western and north India allows us to infer the prevalence of separated realms with variably restricted palaeoenvironmental conditions. Overall, the faunal evidence is indicative of dominantly estuarine to shallow marine conditions with enhanced freshwater influence during the Thanetian as compared to the Danian. Our study also argues in favour of the earliest appearance of dinoflagellate cyst Apectodinium in the near-equatorial region of the Tethys Ocean during the early Paleocene. (within Danian).

Last Interglacial (MIS 5e) sea surface hydrographic conditions in coastal southern California based on dinoflagellate cysts

The first high resolution record of dinoflagellate cysts ∼110–155 kyr over Termination II and the Last Interglacial in the Santa Barbara Basin, California from ODP Hole 893A details a complex paleoceanographic history. Variation in cyst relative abundances, concentrations, and diversity reflects climatic and ocean circulation changes, and the assemblages are used to make qualitative reconstructions of sea surface temperature (SST) and annual primary productivity. The dominance of heterotrophic Brigantedinium spp. throughout the section indicates an important influence of coastal upwelling on the basin. Based on the dinoflagellate cyst assemblages, five zones are identified, which approximately correspond to the marine isotope stage boundaries and their associated changes in SST and sea level. Cooler intervals, MIS 6 and MIS 5d, are characterized by cold-water indicator species Selenopemphix undulata whereas thermophilic taxon Spiniferites mirabilis characterizes a warm MIS 5e. In contrast to other studies in the Pacific, the data exhibits a one to two-thousand-year cooling event ∼129 kyr that correlates to the Termination II sea level still-stand of the two-step deglaciation. A significant increase in cyst concentrations in the latest MIS 5e implies enhanced primary production due to increased seasonal upwelling and the warm, nutrient rich waters entering the basin after sea level stabilizes near modern levels. The hydrological evolution and cyst signal of the Last Interglacial is similar to the development of the Holocene in the Santa Barbara Basin, but the sustained presence of Spiniferites mirabilis across MIS 5e indicates SSTs were higher than modern conditions. • First high resolution dinocyst study in temperate northeastern Pacific during MIS5e. • SST, upwelling, and sea-level changes drive dinocyst variation in the SBB. • Spiniferites mirabilis and Selenopemphix undulata are best indicators of SST change. • Dinocyst paleoecology consistent with previous geochemical and palynology signals. • Termination II and MIS5e dinocyst assemblages are comparable to Holocene SBB cysts.

Paleoceanography and dinoflagellate cyst stratigraphy across the Lower\u2013Middle Pleistocene Subseries (Calabrian\u2013Chibanian Stage) boundary at the Chiba composite section, Japan

A dinoflagellate cyst record from the highly resolved Chiba composite section in Japan has been used to reconstruct sea-surface paleoceanographic changes across the Lower–Middle Pleistocene Subseries (Calabrian–Chibanian Stage) boundary at the global stratotype, constituting the first detailed study of this microfossil group from the Pleistocene of the Japanese Pacific margin. Cold, subarctic water masses from 794.2 ka gave way to warming and rapid retreat of the Subpolar Front at 789.3 ka, ~ 2000 years before the end of Marine Isotope Stage (MIS) 20. Throughout the fully interglacial conditions of MIS 19c, assemblages are consistent with warm sea surface temperatures but also reveal instability and latitudinal shifts in the Kuroshio Extension system. The abrupt dominance of Protoceratium reticulatum cysts between 772.9 and 770.4 ka (MIS 19b) registers the influence of cooler, mixed, nutrient-rich waters of the Kuroshio–Oyashio Interfrontal Zone resulting from a southward shift of the Kuroshio Extension. Its onset at 772.9 ka serves as a local ecostratigraphic marker for the Chibanian Stage Global Boundary Stratotype Section and Point (GSSP) which occurs just 1.15 m (= 1300 years) below it. An interval from 770.1 ka to the top of the examined succession at 765.8 ka (MIS 19a) represents warm, presumably stratified but still nutrient-elevated surface waters, indicating a northward shift of the Kuroshio Extension ~ 5 kyrs after the termination of full interglacial conditions on land.

The Danian Sea: Dinoflagellate cysts assemblages from Neuquén Basin, Roca Formation (Argentina) and its comparison with other southern South America localities

The study section at the Casa de Piedra locality (Neuquén Basin) is located near the Colorado River, southwestern sector of La Pampa province, Argentina. The section is assigned to the Roca Formation, which records a shallow marine environment linked with Atlantic transgressions. It includes a new record of dinoflagellate cysts of the Danian Sea, in northern Patagonia. Most of the recognized taxa have a Late Cretaceous – Danian stratigraphic range in the Southern Hemisphere. The great similarity with the dinoflagellate cysts recorded in the uppermost Pedro Luro Formation, Colorado Basin allowed inferring a Late Danian age for the Roca Formation in the Casa de Piedra section. This age is also supported by the presence of Vozzhennikovia apertura (FAD: 65.10 Ma) and Cerodinium diebelli (LAD: 61.05 Ma) and by other micofossils data including foraminifers and nannofosils. The sedimentary facies and the dinoflagellate cysts identified suggest a neritic environment ranging from marginal-marine with scarce fluvial influence to outer neritic conditions. Taking into account the sporomorphs content, the paleoenvironment conditions would be similar to those of the North-west and Colorado Basins for the Danian, with a forest of Ulmaceae (Verrustephanoporites simplex) and montane forest (Podocarpaceae, Rutaceae). The sporomorph assemblages indicate warm paleotemperatures (subtropical-tropical). The high similarity of dinoflagellate cyst records between Roca and Pedro Luro Formations would suggest a probable link between Neuquén and Colorado basins during Danian times. This connection has been postulated by several authors and could be related to the Neuquén embayment through the Huincul fault.

Inoceramid bivalve and dinoflagellate cyst integrated biostratigraphy of the topmost Campanian–Maastrichtian in a part of the Western Fore-Balkan Mountains, northwest Bulgaria

We present the inoceramid and dinoflagellate cyst record from the topmost Campanian–Maastrichtian strata of three key sections of the Western Fore-Balkan Mountains, northwest Bulgaria. The following inoceramid zones were recognized: “Inoceramus” redbirdensis Zone, Endocostea typica Zone, Trochoceramus radiosus Zone and “Inoceramus” ianjonaensis Zone. The Campanian/Maastrichtian boundary was tentatively drawn slightly below the first occurrence of Endocostea typica. The uppermost inoceramid assemblage was confined to the lower part of the upper Maastrichtian. Dinoflagellate cyst ranges, as well as the first and the last occurrence events of dinocysts, provided valuable markers for the stratigraphic subdivision of the Maastrichtian. The first occurrence of Microdinium carpentierae was documented in proximity to the Campanian/Maastrichtian boundary. The Cerodinium diebelii Zone was recognized with a stratigraphical range from the lower Maastrichtian to the lower upper Maastrichtian. The last occurrence of Alterbidinium acutulum was recorded in the lower Maastrichtian and used as aid for tracing the lower/upper Maastrichtian substage boundary. The marked domination of delicate chorate dinocysts in all sections and the encountered low P/G ratio values are indicative of stable low-energy depositional environment and oligotrophic conditions, with normal marine productivity and nutrient availability in the basin during the Maastrichtian.

Palynology of the Cenomanian to lowermost Campanian (Upper Cretaceous) Chalk of the Trunch Borehole (Norfolk, UK) and a new dinoflagellate cyst bioevent stratigraphy for NW Europe

A high-resolution palynological analysis of the Cenomanian to Lower Campanian in the Trunch borehole, Norfolk (southern North Sea basin) is documented. This constitutes the most detailed continuous record of organic-walled dinoflagellate cysts (dinocysts) from a single Upper Cretaceous section to date. A revised stratigraphic framework for the Trunch succession is presented, integrating regional marker bed lithostratigraphy, macrofossil biostratigraphy and carbon-isotope chemostratigraphy. Palynological events at Trunch are compared to published records with an emphasis on NW Europe, and a new stratigraphy comprising 65 dinocyst events is proposed. A geochronological age model based on radioisotopic and astrochronological ages of macrofossil biostratigraphic datum levels and global carbon-isotope events (CIEs) is used to revise the age calibration of the Upper Cretaceous δ13Ccarb carbonate reference curve for the English Chalk, and to calculate absolute ages for the palynological events with an accuracy judged to be ±500 kyr. The palaeogeographic distribution of key taxa is presented based on records obtained from the PALYNODATA database and additional records, summarised to 212 sites world-wide. Endemic NW Europe, Northern Hemisphere-wide and global species distributions are demonstrated. A taxonomic and detailed stratigraphic discussion is provided to determine the likelihood that the events may be considered as global first or last appearance datum levels, or are local to regional lowest and highest occurrences. Four global, 21 Northern Hemisphere and 40 NW Europe events are tabulated, including 29 inceptions or extinctions of marker species; an additional 36 events may be of regional significance.

Dinoflagellate cyst biostratigraphy and palaeoecology of the early Paleogene Landana reference section, Cabinda Province, Angola

Forty-four rock samples from the Landana section, belonging to the historical Dartevelle collection of the Royal Museum for Central Africa (RMCA) at Tervuren, Belgium, were palynologically processed and analysed. Systematic analysis of the samples from the Landana sea cliff locality has revealed 90 dinoflagellate cyst taxa spanning an interval that ranges at least from the middle Paleocene to the late Eocene/early Oligocene. This locality represents the first extensive sub-equatorial African Paleogene dinoflagellate cyst record. Dinoflagellate cyst occurrences were calibrated and evaluated against newly revised foraminiferal ranges. This novel dinoflagellate cyst biostratigraphic record was compared and correlated with contemporaneous records relatively close by in the Gulf of Guinea, as well as with records from more distant locations such as Antarctica, Australia and New Zealand. A preliminary dinoflagellate cyst zonation is here proposed comprising three zones and five unzoned yet otherwise distinct intervals. The lower part of the Landana section records a large portion of the early to middle/late Selandian, which is made apparent by the presence of taxa such as Isabelidinium cingulatum, Isabelidinium? viborgense, and Spinidinium densispinatum. The Thanetian through Lutetian part of the section is more fragmentary and is devoid of any significant marker taxa normally typical for this time interval elsewhere. The upper part of the record is largely devoid of dinoflagellate cysts, with the few dinoflagellate cyst-bearing samples pointing to an Eocene to early Oligocene age. Dinoflagellate cyst assemblages are relatively variable and often largely dominated by a single particular taxon or complex. We record remarkably abundant peridinioid cysts signalling high palaeoproductivity for protracted periods of time, resulting from either heightened terrestrial influence or enhanced upwelling.

The Holocene history of the NE Black Sea and surrounding areas: An integrated record of marine and terrestrial palaeoenvironmental change

Here we present an almost complete and integrated Holocene record of marine and terrestrial palaeoenvironmental change from the NE shelf of the Black Sea. A dinoflagellate cyst record used to reconstruct Holocene sea-surface conditions highlights that the NE shelf was a brackish water environment, with a minimum salinity of 7 psu in the early-Holocene before changing at a gradual rate to a more saline environment with maximum salinities of ~18 psu being reached around 3 cal. ka. A warming phase was detected from 6 cal. ka BP, with warmest conditions between 3 and 2.5 cal. ka BP. A pollen record is used to examine the major climate and land-use changes in the eastern Black Sea region. Biome reconstructions show that the temperate deciduous forest dominates throughout the record, although with an overall decline. From early-Holocene to the first hiatus around ~9 cal. ka BP, Pinus pollen dominates, while taxa representing a mixed oak-hornbeam-beech forest are less abundant, indicating relatively cool and dry conditions. Between ~7.9 and ~6.1 cal. ka BP, a thermophilous deciduous forest established, suggesting an overall warming trend and humid conditions. From 4 cal. ka BP, Pinus dominates the pollen record, accompanied by an increase of herbs, implying an opening of the landscape, which would coincide with the beginning of the Meghalayan Age. The integrated record of the marine and terrestrial climate indicators supports the notion that this change in landscape may have been triggered by a combination of warmer and drier conditions and human activities in this region.

Dinoflagellate cysts from the ‘Anthropocene’ of Gullmar Fjord, west coast of Sweden and their potential for monitoring climate change

A small set of samples from Gullmar Fjord, on the west coast of Sweden, together with published data, has allowed the investigation of the ‘Anthropocene’ within the fjord. The dinoflagellate cyst record and its statistical analysis fails to show any marked changes within the assemblages either across the proposed boundary or indeed within the youngest sediments at the top of the sequence. However there are some small scale differences in the youngest assemblages that are of interest. In particular these include quantitative shifts in the numbers of some of the species especially Pentapharsodinium dalei, which may be indicative of somewhat cooler environments linked to the winter North Atlantic Oscillation (NAO) and extra availability of nutrients from Ekman pumping. These small scale shifts in the assemblages point to clear dynamism within the phytoplankton populations reacting to both anthropogenic and natural environmental change; evidence of the complexity of the system.The proven utility of dinoflagellate cysts in charting climate change throughout both the Pleistocene and Holocene within Gullmar Fjord, and elsewhere along the west coast of Sweden is in marked contrast to the little change at the ‘Anthropocene’ boundary. Nonetheless the geographical position of the fjords along the Skagerrak are ideal to monitor environmental change within the North Sea basin and perhaps further afield in the eastern North Atlantic Ocean; especially since further climate change threatens regime change within the marine environment affecting tourism, industry and mariculture along the coast.

Shifts of the Brazil-Falklands/Malvinas Confluence in the western South Atlantic during the latest Pleistocene–Holocene inferred from dinoflagellate cysts

The Brazil-Falklands/Malvinas Confluence (BFMC), a highly energetic convergence of surface currents in the western South Atlantic, has shifted southward in recent years and this shift is projected to progress in the future. Palaeoecological insights documenting past changes of these currents may help in anticipating future impacts on the environment. We used dinoflagellate cyst analyses from a marine sediment core to reconstruct environmental changes in the Argentine continental margin, western South Atlantic, during the last ca. 12,600 years. The dynamics of the BFMC were reconstructed using the relative frequency of warm-water indicators for the Brazil Current (BC) versus cold-water taxa thriving in the Falklands/Malvinas Current (FMC). We found that the latitudinal position of the BFMC was relatively stable with only minor amplitude migrations between 12.6 and 8.7 cal kyr BP, followed by periods with stronger shifts to the south and the north until 0.66 cal kyr BP. After that, the BFMC shifted continuously to the south. The increase in freshwater algae abundance after ca. 5.7 cal kyr BP suggests an increase in precipitation over the adjacent Rio de la Plata drainage basin in south-eastern South America. As previously documented, such an increase in precipitation was probably related to a higher El Niño-Southern Oscillation frequency and longer, stronger El Niño events since the mid-Holocene. The dinoflagellate cyst record indicates a phase of the enhanced presence of nutrient-rich waters over the core site between ca. 6.3 and 5.7 cal kyr BP, as well as from 0.66 cal kyr BP to the recent. The highest eutrophication in the ocean surface occurred during the last ca. 100 years, most probably due to stronger human impact in the area of the Rio de la Plata drainage basin.

Climatic and anthropogenic impacts on the Ría de Vigo (NW Iberia) over the last two centuries: A high-resolution dinoflagellate cyst sedimentary record

A high-resolution dinoflagellate cyst record spanning the period of ~1830–2012 CE from Ría de Vigo (Atlantic margin of NW Iberia) is presented. Changes in concentrations and percentages of dinoflagellate cysts and freshwater algal spores reflect climatic and anthropogenic influences on the ria, i.e. coastal inlet formed by the partial submergence of a river valley. Statistical analyses (PCA and clustering) were used to identify the main patterns of change in the cyst assemblages. The cyst record was compared with reconstructed and measured instrumental environmental data (NAO, temperatures, mean sea level, etc.) to support (palaeo)reconstructions. Four main phases were identified: the first phase (~1830–1855 CE) of lower relative sea level (RSL), temperatures and precipitations represents the last stages of the LIA (Little Ice Age); the second phase (~1855–1910 CE) is interpreted as a transition between the colder LIA and the wetter and warmer conditions that prevailed through the 20th century; the third phase (~1910–1975 CE) is characterized by strong river inputs and water stratification in the ria; and the fourth phase (~1975–2012 CE) reflects impacts of anthropogenic warming and pollution. The anthropogenic signal consists of increases in heterotrophic cyst proportions and cysts diversity, as well as of a marked decline of potentially toxic Lingulodinium machaerophorum. Increasing organic matter content, nutrients and industrial wastes have likely caused detrimental impacts on the autotrophic dinoflagellates, by increasing turbidity and toxicity. The B5-cyst record and its comparison with previously published data suggest that increased concentrations of L. machaerophorum in the 20th century were mainly related to river flow variations, that in turn were primarily driven by NAO changes, rather than cultural eutrophication. We also report high abundances of Peridinium ponticum in our record, determining that this species is not exclusive to the Black and Marmara Seas and has much wider natural distribution.

Mid‐Piacenzian Variability of Nordic Seas Surface Circulation Linked to Terrestrial Climatic Change in Norway

AbstractDuring the mid‐Piacenzian, Nordic Seas sea surface temperatures (SSTs) were higher than today. While SSTs provide crucial climatic information, on their own they do not allow a reconstruction of potential underlying changes in water masses and currents. A new dinoflagellate cyst record for Ocean Drilling Program (ODP) Site 642 is presented to evaluate changes in northward heat transport via the Norwegian Atlantic Current (NwAC) between 3.320 and 3.137 Ma. The record is compared with vegetation and SST reconstructions from Site 642 and SSTs from Iceland Sea ODP Site 907 to identify links between SSTs, ocean currents, and vegetation changes. The dinocyst record shows that strong Atlantic water influence via the NwAC corresponds to higher‐than‐present SSTs and cool temperate vegetation during Marine Isotope Stage (MIS) transition M2–M1 and KM5. Reduced Atlantic water inflow relative to the warm stages coincides with near‐modern SSTs and boreal vegetation during MIS M2, KM6, and KM4–KM2. During most of the studied interval, a strong SST gradient between Sites 642 and 907 indicates the presence of a proto‐Arctic Front (AF). An absent gradient during the first half of MIS KM6, due to reduced Atlantic water influence at Site 642 and warm, presumably Atlantic water reaching Site 907, is indicative of a weakened NwAC and East Greenland Current. We conclude that repeated changes in Atlantic water influence directly affect terrestrial climate and that an active NwAC is needed for an AF to develop. Obliquity forcing may have played a role, but the correlation is not consistent.

Dinocyst assemblage constraints on oceanographic and atmospheric processes in the eastern equatorial Atlantic over the last 44 kyr

Abstract. A new 44 kyr long record of dinoflagellate (phytoplanktonic organisms) cysts (dinocysts) is presented from a marine sediment core collected on the Congolese margin with the aim of reconstructing past hydrological changes in the equatorial eastern Atlantic Ocean since Marine Isotopic Stage (MIS) 3. Our high-resolution dinocyst record indicates that significant temperature and moisture variations occurred across the glacial period, the last deglaciation and the Holocene. The use of specific dinocyst taxa, indicative of fluvial, upwelling and Benguela Current past environments for instance, provides insights into the main forcing mechanisms controlling palaeohydrological changes on orbital timescales. In particular, we are able, for the last 44 kyr, to correlate fluvial-sensitive taxa to monsoonal mechanisms related to precession minima–obliquity maxima combinations. While upwelling mechanisms appear as the main drivers for dinoflagellate productivity during MIS 2, dissolved nutrient-enriched Congo River inputs to the ocean also played a significant role in promoting dinoflagellate productivity between approximately 15.5 and 5 ka BP. Finally, this high-resolution dinocyst study permits us to precisely investigate the suborbital timing of the last glacial–interglacial termination, including an atypical warm and wet oceanic LGM signature, northern high-latitude abrupt climate change impacts in the equatorial eastern Atlantic, as well as a two-step decrease in moisture conditions during the Holocene at around 7–6 and 4–3.5 ka BP.

Steps in the intensification of Benguela upwelling over the Walvis Ridge during Miocene and Pliocene

Upwelling is a significant part of the ocean circulation controlling largely the transport of nutrient-rich cold waters to the surface and therefore influencing ocean productivity and global climate. The Benguela upwelling system (BUS) is one of the major upwelling areas in the world. Previous reconstructions of the BUS mainly focused on the onset and intensification in southern and central parts, but changes of the northern part have been rarely investigated in detail. Using the Late Miocene to Pliocene organic-walled dinoflagellate cyst record of ODP Site 1081, we reconstruct and discuss the early upwelling history over the Walvis Ridge with a special focus on the movement of the Angola-Benguela Front (ABF). We suggest that during the Late Miocene the Angola Current flowed southwards over the Walvis Ridge more frequently than today because the ABF was probably located further south as a result of a weaker meridional temperature gradient. A possible strengthening of the meridional gradient during the latest Miocene to early Pliocene in combination with uplift of south-western Africa intensified the upwelling along the coast and increased the upwelling’s filaments over the Walvis Ridge. An intermediate period from 6.2 to 5.5 Ma is shown by the dominance of Habibacysta tectata, cysts of a cool-tolerant dinoflagellate known from the northern Atlantic, indicating changing oceanic conditions contemporaneous with the Messinian Salinity Crisis. From 4.3 Ma on, the upwelling signal got stronger again and waters were well-mixed and nutrient-rich. Our results indicate a northward migration of the ABF as early as 7 Ma and the initial stepwise intensification of the BUS.

The first record of calcareous dinoflagellate cysts from the Upper Cretaceous of the Volga River Region.

The taxonomic position of the microproblematics previously considered to be Foraminifera or Calcisphaerulidae is established. The first record from Russia of calcareous cysts of Dinoflagellata is presented. The microfossils originate from the Maastrichtian siliceous clay of the Volga River Region.

High resolution dinoflagellate cyst record of environmental change in Effingham Inlet (British Columbia, Canada) over the last millennium

We present a high resolution sedimentary record of dinoflagellate cysts spanning the last ~900years recovered from Effingham Inlet, a glacial fjord on the west coast of Vancouver Island, Canada. The combination of seasonal coastal upwelling supporting high levels of marine primary productivity in surface waters, together with restricted bottom water circulation in the silled fjord, fosters the preservation of laminated sediments in the inner basin of Effingham Inlet. Geochemical data are used to assess the sedimentary facies of the core, which is composed primarily of laminated units (50.2%) occasionally interrupted by “seismites” (39.5%) and homogenous units (10.2%). The chronology of the ~2m-long core is based on varve counting and fifteen 14C dates, and is anchored by a seismite previously dated at AD 1946.The dinoflagellate cyst assemblages are diverse (total of 47 taxa), abundant (average concentrations of 102,900cystg−1 of dry sediment), and characterized by a proportionally equal contribution of autotrophic and heterotrophic cyst taxa in most samples. Overall, cyst assemblages are characterized by Operculodinium centrocarpum (36.2%) accompanied by Brigantedinium spp. (18.0%) and Dubridinium spp. (6.6%). Multivariate analyses are used to extract the dominant patterns of variability in autotrophic and heterotrophic dinoflagellate cyst assemblages separately, and help in identifying the temperature and primary productivity gradients encoded in the cyst sedimentary record in this particular estuary.Specific intervals identified in the dinoflagellate cyst record are interpreted to represent the local expression of the “Medieval Climate Anomaly” (from the base of the record, ~AD 1090 to 1230), the “Little Ice Age” (~AD 1230 to late 19th century) and warming in the second half of the 20th century. The timing of these intervals are consistent with the regional paleoclimate and help constrain past climatic and oceanographic variability on the west coast of Vancouver Island. The origin of homogenous units in the sedimentary record of Effingham Inlet and paleoseismicity in the region are also discussed.

Palynological evidence for late Quaternary climate and marine primary productivity changes along the California margin

AbstractA high‐resolution sedimentary record of dinoflagellate cysts from Ocean Drilling Program Hole 1017E (off Point Conception, California margin) reflects how marine primary productivity has changed in response to major shifts in climate and ocean circulation along the California margin over the past 42 kyr. Throughout the studied sequence, dinoflagellate cyst assemblages are dominated by upwelling‐related taxa, signifying the continued presence of coastal upwelling on the margin during the late Quaternary. The cyst record suggests that marine primary productivity was enhanced during the Holocene and Bølling, and to a lesser extent, during the late glacial and most Dansgaard‐Oeschger events, while an apparent reduction in primary productivity can be seen during the Younger Dryas. The best analogue technique, based on a modern dinoflagellate cyst assemblage database from the northeast Pacific, was used for quantitative reconstruction of past sea surface conditions. It points to dynamic changes in annual marine primary productivity (~235–331 g C m−2 yr−1) and sea surface temperature (~10.1–12.6°C in winter; ~13.1–14.3°C in summer), while sea surface salinity appears to be confined to a narrower range (~32.9–33.4 in summer). Our results also indicate noticeable climate variability during the Holocene in this region.

High resolution sedimentary record of dinoflagellate cysts reflects decadal variability and 20th century warming in the Santa Barbara Basin

We present a continuous record of dinoflagellate cysts from a core of laminated sediments collected in the Santa Barbara Basin (SBB), off Southern California. The core spans the last ∼260 years and is analysed at biennial (two-year) resolution. Variations in dinoflagellate cyst assemblages are compared with 20th century historical changes, and are used to examine changes in primary productivity and species composition, which are bound to the variability in upwelling and sea-surface temperature (SST) in the region.Cysts produced by heterotrophic dinoflagellates dominate the assemblages. In particular, Brigantedinium spp. (on average 64.2% of the assemblages) are commonly associated with high levels of primary productivity, typically observed under active upwelling conditions, when nutrient supply is higher. Other heterotrophic taxa such as cysts of Protoperidinium americanum, Protoperidinium fukuyoi, Protoperidinium minutum and Archaeperidinium saanichi, all Echinidinium species, Quinquecuspis concreta and Selenopemphix undulata are more abundant in the early part of the record (∼1750s–1870s). These taxa are generally associated with high primary productivity and are observed predominantly during intervals marked by relatively variable conditions of SST, stratification and nutrient loading. The 20th century is marked by an increase in several species of autotrophic affinity, primarily Lingulodinium machaerophorum and Spiniferites ramosus. In recent surface sediments from the region, these species are more abundant in the Southern California Bight, and they are associated with conditions of relaxed upwelling in the SBB (typically observed during summer and fall), when SST is higher and nutrient supply is moderate. Their increasing concentrations since the early 20th century reflect warmer SST and possibly stronger stratification during the warmest season. Taken together, the changes in cyst assemblages provide further evidence that persistently warmer conditions in the SBB began affecting marine populations by the late 1920s.Decadal-scale variations in primary productivity are encoded in the heterotrophic dinoflagellate cyst record, with higher (lower) concentrations of heterotrophic taxa occurring during “cool” (“warm”) phases of the Pacific Decadal Oscillation (PDO) index. Wavelet analysis of heterotrophic taxa concentrations suggests a weaker influence of the PDO on biota of the region during the 19th century.

Natural and cultural eutrophication of Sluice Pond, Massachusetts, USA, recorded by algal and protozoan microfossils

Microfossil studies from Sluice Pond, Massachusetts, identified two environmental perturbations that impacted algal and protozoan communities: (1) natural eutrophication and water column mixing driven by the mid-Holocene drought and (2) cultural eutrophication, increasing bottom water anoxia, and toxicity accompanying human settlement. SP09 KC2 from the deep basin of this partially meromictic pond has an abundant and diverse record of dinoflagellate cysts spanning 11,400 years. Bottom water anoxia appears to have prevented benthic protozoans from colonizing until lake levels fell throughout New England during the mid-Holocene drought. Lower lake levels allowed mixing of the water column and a thecamoebian fauna rich in centropyxids, Pontigulasia compressa, and Difflugia oblonga to flourish in SP09 KC2. This lowstand is marked by an unconformity spanning the mid-Holocene hemlock minimum (5400–3500 cal. BP) in SP07 PC4 and by an increase in nutrients in the water column allowing mesotrophic–eutrophic dinoflagellate taxa ( Peridinium cf. gatunense and Peridinium willei) to increase at the expense of Peridinium wisconsinense. Rising lake levels in response to the warm, wet climate are recorded by increasing abundances of protozoa tolerant of lower dissolved oxygen (DO) throughout Sluice Pond ~2200 cal. BP – the thecamoebians Arcella vulgaris, Difflugia protaeiformis, and Cucurbitella tricuspis and the ciliate Codonella cratera. Subsequent decline in lake level associated with late Holocene aridity allowed a diverse thecamoebian community to thrive until around 300 years ago when a more intense phase of eutrophication resulted from human impact. Bottom water anoxia due to enhanced biochemical oxygen demand (BOD) is recorded by the dominance of C. tricuspis in sediments rich in ragweed pollen and other weedy plants. Peak cyst concentrations in this interval in SP07 PC4 reflect cultural eutrophication leading to high primary productivity and low DO, promoting cyst preservation. Low microfossil concentrations in the surface sediments are attributed to low DO and toxicity.