Distribution Of Dinoflagellate Cysts Research Articles

The distribution of dinoflagellate cyst assemblages in recent sediments of the Oualidia Lagoon, Morocco, with a focus on toxic species

Harmful algal blooms (HABs) are becoming widely distributed and more frequent, threatening socioecosystems and human health. We determined species composition, abundance and spatial distribution of dinoflagellate cysts in the upper sediment of the Oualidia Lagoon located on the Atlantic coast of Morocco. Sediment samples were collected in 2017 at 51 stations, and environmental parameters were measured together with microphytoplankton abundance. Sediment characteristics including water percentage, organic matter content and grain size were determined. Fourteen dinoflagellate cyst morphotypes were identified, with Lingulodinium polyedrum (50%) and Gonyaulax spinifera (22%) dominating the assemblages. Total cyst densities ranged from 0 to 293 cysts g−1 dry sediment. Cyst densities were positively correlated with water content and organic matter content and increased with decreasing sediment grain size. We revealed the presence of three neurotoxic dinoflagellate species: Alexandrium minutum, the Alexandrium tamarense species complex, and Gymnodinium catenatum. Numerous cysts had accumulated in the sediment, and, because they are likely responsible for the initiation of HABs in Oualidia Lagoon, they should be monitored.

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.

Drivers of dinoflagellate benthic cyst assemblages in the NW Patagonian Fjords System and its adjacent oceanic shelf, with a focus on harmful species

In recent decades, the alteration of coastal food webs (via aquaculture, fishing, and leisure activities), nutrient loading, and an expansion of monitoring programs have prompted an apparent worldwide rise in Harmful Algae Blooms (HABs). Over this time, a parallel increase in HABs has also been observed in the Chilean southern austral region (Patagonia fjords). HAB species like Alexandrium catenella—responsible for Paralytic Shellfish Poisoning (PSP)—are of great public concern due to their negative socioeconomic impacts and significant northward geographical range expansion. Many toxic dinoflagellate species (like A. catenella) produce benthic resting cysts, yet a holistic understanding of the physical-chemical and biological conditions influencing the distributions of cysts in this region is lacking. In this study, we measured a combination of hydrographic (temperature, salinity, and dissolved oxygen) and sediment physical-chemical properties (temperature, pH and redox potential), in addition to meiofaunal abundances –as sediment bioturbators and potential cyst predators– to determine the factors influencing dinoflagellate cyst distribution, with emphasis on A. catenella in and around a “hotspot” area of southern Chile. An analysis of similarities (ANOSIM) test revealed significant differences (p < 0.011) in cyst assemblages between the fjords and oceanic environments. Permutational Analysis of Variance (PERMANOVA) showed significant effects of sediment temperature and silt proportion in explaining differences in the cyst assemblages. A generalized linear model (GLM) indicated that sediment temperature, silt/sand, anoxic conditions, and low abundances of Harpacticoida —a meiofauna herbivore group and potential bioturbator— are associated with the higher resting cyst abundances of the harmful species A. catenella. The implications for A. catenella resting cysts dynamics are discussed, highlighting physical-chemical and biological interactions and their potential for PSP outbreak initiation.

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.

Eutrophication Driven by Aquaculture Fish Farms Controls Phytoplankton and Dinoflagellate Cyst Abundance in the Southern Coastal Waters of Korea

We examined the dynamics of dinoflagellate cyst and phytoplankton assemblages in eutrophic coastal waters of Korea, adjacent to fish and shellfish farms. Water temperature showed seasonality, whereas salinity and pH remained relatively consistent. Dissolved inorganic nutrient levels were higher in September and at the inner stations, where aquaculture fish farms are located than those in May and at the outer stations. Canonical correspondence analysis and artificial neural network analysis revealed multiple environmental factors that affect the distribution of phytoplankton and dinoflagellate cysts. Diatoms dominated in the phytoplankton assemblages, while the protoperidinioid group dominated in the dinoflagellate cyst assemblages. Cyst abundance was higher at the outer stations than at the inner stations due to transport by fast currents, and phytoplankton abundance was positively correlated with cyst abundance. An increase in diatom abundance led to an increase in heterotrophic/mixotrophic cyst abundance, indicating that excessive uneaten food and urinary waste from the fish farms caused eutrophication in the study region and fast growth of diatoms, thereby contributing to the growth of heterotrophic/mixotrophic dinoflagellates and consequently, high abundance of heterotrophic/mixotrophic dinoflagellate cysts.

Dinoflagellate cyst distribution in surface sediments of Ambon Bay (eastern Indonesia): Environmental conditions and harmful blooms

The present study aimed to document dinocyst ecological preferences in Ambon Bay, Eastern Indonesia, and to investigate if the bay sediments serve as a seedbank for toxic bloom events. To this end, dinocyst and geochemical analyses of surface sediment samples were performed, along with physicochemical water column parameters. Twentythree dinocyst species were identified, and high dinocyst concentrations (up to ~12,000 cysts g−1 dry sediment) were found in the inner bay. Environmental factors such as surface water temperature and salinity generally played an important role in dinocyst distribution. The concentration of Polysphaeridium zoharyi cysts showed a strong positive correlation with phosphorus. A statistically significant correlation was also found with the concentration of other autotrophic dinocysts in the sediments, and an inverse correlation was observed with the sediment C/N ratio. Cysts may serve as seedbanks for Pyrodinium bahamense blooms in the area.

Dinoflagellate cyst assemblages in surface sediment from Jakarta Bay

Dinoflagellate cysts play an essential role in the initiation, recurrence and geographical expansion of harmful algal blooms (HABs). The horizontal distribution and abundance of dinoflagellate cysts in marine sediments provide essential information in giving early warnings of the presence of toxic species and possible continuing recurrence of HABs in a given area. This research carried out in the waters of Jakarta Bay. Sediment samples collected from thirteen sampling stations using TFO gravity corer 2.1 cm diameter from sediment thickness 0-4 cm. The results showed that resting cysts belong to Gonyaulax, Alexandrium, Scrippsiella, Protoperidinium, Gymnodinium, Gyrodinium. Two of them, namely Gymnodinium sp and Alexandrium sp, known as toxic species. Cysts in the sediment thickness 0-4 cm mainly dominated by the group of Gonyaulax (Gonyaulacoid). Cyst abundance in the sediment depth-layer 0-2 cm is higher than in depth-layer 2-4 cm. The number of dino-cysts in sediment layer 0-2 cm ranged from 2.984 – 22.298 cysts cm−3 while in the layer 2-4 cm the amount varies from 1.063 – 8.132 cysts cm−3 of wet sediment. The result revealed that dino-cyst abundance is higher in the deposit collected from locations near to the coast. The assemblages of dinoflagellate resting cysts seemed to have a relation with some hydrological parameters.

Short-Term Sea Level Changes of the Upper Cretaceous Carbonates: Calibration between Palynomorphs Composition, Inorganic Geochemistry, and Stable Isotopes

Widespread deposition of pelagic-hemipelagic sediments provide an archive for the Late Cretaceous greenhouse that triggered sea level oscillations. Global distribution of dinoflagellate cysts (dinocysts) exhibited a comparable pattern to the eustatic sea level, and thus, considered reliable indicators for sea level and sequence stratigraphic reconstructions. Highly diverse assemblage of marine palynomorphs along with elemental proxies that relate to carbonates and siliciclastics and bulk carbonate δ13C and δ18O from the Upper Cretaceous Abu Roash A Member were used to reconstruct short-term sea level oscillations in the Abu Gharadig Basin, southern Tethys. Additionally, we investigated the relationship between various palynological, elemental, and isotope geochemistry parameters and their response to sea level changes and examined the link between these sea level changes and Late Cretaceous climate. This multiproxy approach revealed that a long-term sea-level rise, interrupted by minor short-term fall, was prevalent during the Coniacian-earliest Campanian in the southern Tethys, which allowed to divide the studied succession into four complete and two incomplete 3rd order transgressive-regressive sequences. Carbon and oxygen isotopes of bulk hemipelagic carbonates were calibrated with gonyaulacoids and freshwater algae (FWA)-pteridophyte spores and results showed that positive δ13Ccarb trends were consistent, in part, with excess gonyaulacoid dinocysts and reduced FWA-spores, reinforcing a rising sea level and vice versa. A reverse pattern was shown between the δ18Ocarb and gonyaulacoid dinocysts, where negative δ18Ocarb trends were slightly consistent with enhanced gonyaulacoid content, indicating a rising sea level and vice versa. However, stable isotope trends were not in agreement with palynological calibrations at some intervals. Therefore, the isotope records can be used as reliable indicators for reconstructing changes in long-term sea level rather than short-term oscillations.

Distribution of peridiniacean dinoflagellate cysts from cores of organic rich shales of the Duwi and Dakhla formations of Egypt

The Campanian-Maastrictian black shales in Egypt comprise a significant part of the worldwide belt of organic-rich shales. These dark-colored shales stretch from the Dakhla in the Western Desert to Safaga area in the east along the Red Sea and are well known in the Middle East and North Africa. A palynological study of these shales hosted mostly in the Duwi and Dakhla formations yields a Campanian to Maastrichtian age. The extracted palynomorph assemblage from the Abu Tartur and Quseir boreholes, which is dominated by dinoflagellate cysts (dinocysts) representing a well-preserved peridinioid association (>90% of the total dinocysts), is indicative of marine origin and very high paleoproductivity. The common dinocysts are Andalusiella mauthei, Andalusiella gabonensis, Cerodinium diebelii, Senegalinium bicavatum, Senegalinium laevigatum, Palaeocystodinium golzowense and Palaeocystodinium australinum. This assemblage is comparable with the dinoflagellate cyst records of the Campanian-Maastrichtian low latitude strata in northwest Africa (Morocco and Tunisia) and southern Europe. The dinocyst distribution in the Abu Tartur and Quseir borehole sections suggests an isochronous signature during the early Maastrichtian age.

Distribution of dinoflagellate cysts along the salinity gradient in two tropical estuaries along the West coast of India

Abstract Dinoflagellate cysts are known to be potential seed banks which have an essential role in providing bloom history and also serve as useful indicators of eutrophication in marine environments. The present study is focused on the surface distribution of dinoflagellate cysts along the salinity gradient in two tropical estuaries, namely Chapora and Sal in Goa along the West coast of India. Surface sediments and water samples were collected monthly from February 2016–March 2017 which included all three seasons (pre-monsoon, monsoon, post-monsoon). A total of sixteen species of dinoflagellate cysts belonging to the order, Gymnodiniales, Gonyaulacales, and Peridiniales were recorded in the surface sediments. Cysts of heterotrophic dinoflagellates dominated the assemblage in both estuaries. Based on Redundancy Analysis (RDA), it was observed that the distribution of the dinoflagellate cysts were influenced by various physico-chemical parameters in both estuaries with salinity and grain size being the main explanatory variable. Nitrate limitation is noted to be a triggering factor for dinoflagellate cyst formation. Also, yessotoxin producer species, such as Gonyaulax spinifera, encountered in both estuaries showed an inverse relationship with nitrate concentration. This suggests that, high nitrate input in these estuaries might lead to excystment of Gonyaulax spinifera eventually leading to harmful blooms under eutrophic conditions.

An overview and brief description of common marine organic-walled dinoflagellate cyst taxa occurring in surface sediments of the Northern Hemisphere

Abstract Organic-walled resting cysts of planktonic dinoflagellates occur commonly in modern marine sediment where they represent, with rare exceptions, the only geologically preservable part of the life cycle. Although many species do not produce fossilizable resting cysts, upper Quaternary sediments contain a diverse cyst record that is used frequently for paleoenvironmental reconstruction and stratigraphic analysis. Reconstructions of past sea-surface conditions rely on an understanding of the distributions of dinoflagellate cysts in modern sediments linked to their respective environmental parameters, underpinned by sound taxonomy and standardized nomenclature. Stratigraphic studies additionally require knowledge of morphological details to distinguish extant from similar extinct taxa. Here, 51 dinoflagellate cyst species and two informal cyst morphotypes that are commonly encountered during routine palynological analysis of upper Quaternary marine sediments from the Northern Hemisphere are briefly described taxonomically and illustrated. In addition, their lowest stratigraphic occurrences are provided.

Dinoflagellate cyst distribution in surface sediments from the South China Sea in relation to hydrographic conditions and primary productivity

The geographical distribution of dinoflagellate cysts was investigated in palynologically treated surface sediments from the South China Sea (SCS) to understand the driving environmental factors associated with specific taxa. The western SCS generally has higher total cyst concentrations (>300 cysts g−1) than the eastern region (<200 cysts g−1). The highest concentrations (>1000 cysts g−1) occur off southern Vietnam, whereas the lowest cyst concentrations are off Luzon. The ratio of heterotrophic to autotrophic taxa has inverse distributional patterns to total cyst concentrations, and is likely to be related to an increase in relative abundances of autotrophic taxa when nutrient inputs increase. Brigantedinium spp., Selenopemphix nephroides, and Stelladinium reidii have their highest relative abundances and concentrations off Borneo. Their concentrations are significantly positively correlated with January sea-surface temperature (SST-Jan). In contrast, concentrations of Selenopemphix undulata, Spiniferites hyperacanthus, Dapsilidinium pastielsii and Operculodinium?longispinigerum are negatively correlated with SST-Jan. Lejeunecysta sabrina, cysts of Protoperidinium spp., Votadinium spp., Quinquecuspis concreta and Selenopemphix quanta are positively correlated with chlorophyll-a (chl-a) concentrations and are found in the high primary productivity regions of the SCS. Total Impagidinium, Impagidinium aculeatum, Impagidinium paradoxum, Impagidinium patulum, Nematosphaeropsis labyrinthus, and Polysphaeridium zoharyi are positively correlated with water depth. Their highest abundances are recorded in the northern slope-deep basin that is influenced by the Kuroshio Current, and this cyst assemblage indicates an open-ocean environment.

Dinoflagellate cysts stratigraphy and paleoecology from some Lower Miocene rocks, GS9-1X well, northern Gulf of Suez, Egypt

Palynological analysis of a Lower Miocene section from the GS9-1 well, northern Gulf of Suez, Egypt, has yielded significant dinoflagellate cysts of stratigraphic significance such as Exochosphaeridium insigne, Sumatradinium soucouyantiae and Hytrichokolpoma rigaudiae, which enabled age dating of the well section as Lower Miocene. Two distinct palynofacies are recognised. Palynofacies “A” was recovered from the basal part of the section from the Nukhul Formation. It is dominated by amorphous organic matter (AOM) and contains frequent translucent and opaque phytoclasts indicating a kerogen type II. Palynofacies “B” was recovered from the overlying interval of the well from the Rudeis Formation. It shows an inverse pattern, where phytoclasts are the main components and AOM declines markedly indicating a kerogen type III. Palynomorphs (mostly dinoflagellates) occur in both facies but with lesser percentages than palynodebris. Paleoenvironmental implications are inferred in the light of the recently established information from the distribution of modern-day dinoflagellate cysts (e.g. Zonneveld et al. 2013) since many of the recovered dinoflagellate cysts from the investigated well section still thriving today. A normal (shallow) marine environment is generally inferred for the studied Miocene section, with more peridinioid dinoflagellate cysts than gouyaulacoids. Higher up in the section, terrestrial palynomorphs dominate the dinoflagellate cysts; the latter are rare or missing. This suggests development of a marginal basin that is probably connected to local uplift or sea regression.

Middle Jurassic palynology of the southwest Tabas Block, Central-East Iran

Diverse and moderately to poorly preserved palynofloras occur in the lower Middle Jurassic strata of the Hojedk Formation in the Chahrekhneh, southwest of Tabas, east central Iran. The palynofloras comprise 56 species including spores (15 species allocated to seven genera), various types of pollen (30 species designated to 16 genera), dinoflagellate cysts (five representatives of three genera), and one acritarch. The vertical distribution of miospores allows the erection within the Hojedk Formation of one biozone, the Klukisporites variegatus—Callialasporites trilobatus Assemblage zone, based on the first observed occurrence and the last observed occurrence of selected taxa. Moreover, the vertical distribution of dinoflagellate cysts allows the erection within this formation of one biozone, the Nannoceratopsis sp. cf. N. gracilis Interval zone. These biozones are compared with palynozones from approximately coeval strata in Iran and elsewhere. Abundance of ferns and cycadophytes in the parent floras implies that the host strata accumulated under a moist warm climate during the early Middle Jurassic in this locality. Based on various data of ecogroups in Chahrekhneh, it is considered that there were several environments of upland, warmer lowland, wetter lowland, rivers and delta. Furthermore, based on the occurrence of dinoflagellate cysts it can be concluded that Chahrekhneh is located at the south coastal boundary of the Iran Plate, along the Tethys Ocean.

From bi-polar to regional distribution of modern dinoflagellate cysts, an overview of their biogeography

This paper examines the distribution of 91 modern dinoflagellate cyst taxa from 3636 locations across the world's oceans. Patterns of distributions among the taxa included bi-polarity, cosmopolitan, northern versus southern hemispheres, and geographically restricted. Of the 91 taxa, three dominate these 3636 assemblages at the global scale, Brigantedinium species, Operculodinium centrocarpum sensu Wall and Dale 1966 and some species of Spiniferites . Whereas Brigantedinium is a true cosmopolitan taxon, with high abundances in each ocean, Operculodinium centrocarpum sensu Wall and Dale 1966 shows high abundances in polar to temperate regions in the Northern Hemisphere, and in tropical to sub-tropical waters in the Southern Hemisphere. Spiniferites species show highest occurrences in the Southern Hemisphere. This study also highlights three true bi-polar species, Impagidinium pallidum , Islandinium minutum and cyst of Polarella glacialis . Only a few taxa are strictly endemic, either being relics of ancient seas such as the Paratethys ( Spiniferites cruciformis ) or linked to specific environmental conditions. However, recent studies have shown recent worldwide dispersal of these endemic species possibly due to human activities. Overall, this compilation has highlighted the progress made since the early 1970s on our understanding of these important tracers of environmental conditions but also gaps in our knowledge of their distribution in pelagic regions of the Pacific and Indian Oceans as well as under Arctic sea ice. • 3636 assemblages of modern dinoflagellate cysts were compiled to discuss patterns of distribution. • Of the 91 taxa, only three dominate globally, Brigantedinium spp., Operculodinium centrocarpum and Spiniferites species. • Only three taxa are truly bi-polar: Impagidinium pallidum , Islandinium minutum and Polarella glacialis.

Distribution of harmful dinoflagellate cysts in the surface sediments of Daya Bay of the South China Sea and their relationship to environmental factors

To investigate the distribution of dinoflagellate cyst and their relationship with environmental factors, surface sediments were collected from 14 stations of Daya Bay of the South China Sea. In total, 44 cyst species and 3 uncertain taxa were identified and the total abundance ranged from 79 to 819 cysts g−1 dry weight (DW), showing a decreasing trend from the north-west to the south-east of the bay. Based on cluster analysis, three zones were identified. In Zone I (inner bay), the heterotrophic cyst dominated and warm-water species (Alexandrium minutum/affine and Gonyaulax spinifera) were observed. In Zone III (bay mouth), cyst assemblage was characterized by halophilic taxon Protoperidinium subinerme. Correlation analysis showed that seawater temperature, salinity and sediment particle size had the greatest impacts on the composition and distribution of cyst assemblage. Furthermore, several toxic species, including Lingulodinium polyedrum, Alexandrium spp. and Gymnodinium catenatum, were observed at most stations, indicating a wide distribution and potential risk of harmful algal blooms in Daya Bay.

Pyrodinium bahamense One the Most Significant Harmful Dinoflagellate in Mexico

Pyrodinium bahamense produces saxitoxins and can cause paralytic shellfish poisoning (PSP). This species has caused more human illnesses and fatalities than any other toxic dinoflagellate in Mexico. The distribution of dinoflagellate cysts with their vegetative stage is wide, mainly along Mexican Pacific coasts, from the central Gulf of California to Chiapas; and, in the southern Gulf of Mexico, and the Mexican Caribbean Sea on the Atlantic coast. Cysts, from southern, Gulf of California exhibit thermophilic (20°C to 35°C) and euryhaline characteristics. Blooms occurred typically during summer rainy season, inside of restricted shallow lagoons surrounded by mangrove forests. The local strain toxicity has only been corroborated in one isolate from the southern Gulf of California, which exhibited a high saxitoxin concentration of 95 pg STX eq cell-1. After dinoflagellate blooms, the PSP outbreaks linked with P. bahamense in the Gulf of Tehuantepec, caused at least ~267 human intoxications, and ~21fatalities from 1989 to 2010. This mini-review ends with a viewpoint of management and research strategies to better understand the factors that play essential roles in the bloom dynamics and toxicity of this species.

Ammonites, Microfauna, and Palynomorphs from the Lower Part of the Upper Bajocian Parkinsoni Zone of the Basin of the Bolshoi Zelenchuk River, Northern Caucasus

This paper contains the results of a comprehensive study of the standard Rarecostites subarietis Subzone of the upper Bajocian Parkinsonia parkinsoni Zone in sections on the Kyafar River (a tributary of the Bolshoi Zelenchuk River, Karachay-Cherkessia, Russia). The subzone is represented by shales with marl interbeds and sideritic concretions of the upper member of the Djangura Formation. The taxonomic composition and distribution of ammonites, foraminifers, ostracodes, dinoflagellate cysts, and miospores are established. The characteristic assemblages recognized of microfauna and palynomorphs enabled the recognition of foraminiferal and dinocyst biostratigraphic units for this Middle Jurassic interval. The index fossils are illustrated.

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.

Dinoflagellate cyst abundance is positively correlated to sediment organic carbon in Sydney Harbour and Botany Bay, NSW, Australia.

There is growing public concern about the global expansion of harmful algal bloom species (HABs), with dinoflagellate microalgae comprising the major portion of the harmful taxa. These motile, unicellular organisms have a lifecycle involving sexual reproduction and resting cyst formation whereby cysts can germinate from sediments and 'seed' planktonic populations. Thus, investigation of dinoflagellate cyst (dinocyst) distribution in sediments can provide significant insights into HAB dynamics and contribute to indices of habitat quality. Species composition and abundance of dinocysts in relation to sediment characteristics were studied at 18 stations in two densely populated temperate Australian estuaries, Sydney Harbour (Parramatta River/Port Jackson; PS) and Botany Bay (including Georges River; GB). Eighteen dinocyst taxa were identified, dominated by Protoceratium reticulatum and Gonyaulax sp.1 in the PS estuary, together with Archaeperidinium minutum and Gonyaulax sp.1 in the GB estuary. Cysts of Alexandrium catenella, which is one of the causative species of paralytic shellfish poisoning (PSP), were also detected in both estuaries. Out of the measured sediment characteristics (TOC, Cd, Cr, Cu, Fe, Pb, Mn, Ni, Zn and polycyclic aromatic hydrocarbons), TOC was the parameter explaining most of the variation in dinocyst assemblages and was positively correlated to most of the heavy metals. Given the significant relationship between sediment TOC and dinocyst abundance and heavy metal concentrations, this study suggests that sediment TOC could be broadly used in risk management for potential development of algal blooms and sediment contamination in these estuaries.