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Many marine protists form resting stages that can remain viable in coastal sediments for several decades. Their long-term survival offers the possibility to explore the impact of changes in environmental conditions on population dynamics over multidecadal time scales. Resting stages of the phototrophic dinoflagellate Pentapharsodinium dalei were isolated and germinated from five layers in dated sediment cores from Koljö fjord, Sweden, spanning ca. 1910-2006. This fjord has, during the last century, experienced environmental fluctuations linked to hydrographic variability mainly driven by the North Atlantic Oscillation. Population genetic analyses based on six microsatellite markers revealed high genetic diversity and suggested that samples belonged to two clusters of subpopulations that have persisted for nearly a century. We observed subpopulation shifts coinciding with changes in hydrographic conditions. The large degree of genetic diversity and the potential for both fluctuation and recovery over longer time scales documented here, may help to explain the long-term success of aquatic protists that form resting stages. [ABSTRACT FROM AUTHOR]

Round brown spiny cysts are common elements of Recent and Quaternary dinoflagellate cyst records and are often used to infer past climate conditions. Echinidinium and Islandinium, two cyst-based genera composed of round brown spiny cysts, are believed to have affinities within the Protoperidiniaceae. However, their biological counterparts are still virtually unknown. In this study, we examined the cyst-theca relationship of an Echinidinium-like cyst isolated from recent sediments of the Portuguese coast. The cysts (25-34 μm) had an intercalary theropylic archeopyle and numerous processes (4-9 μm) with tapered stems and minutely expanded tips. Germinated cells were identified as Protoperidinium minutum on the basis of theca morphology and tabulation. This taxon has a complicated taxonomic history and most likely represents a complex of species with very similar thecae but different cyst morphologies. To provide a first step in elucidating the phylogeny of P. minutum and its evolutionary relationship among the Protoperidiniaceae, we undertook the first molecular study of this taxon on the basis of small-subunit (SSU) and large-subunit (LSU) ribosomal (r)DNA genetic sequences obtained through single-cell polymerase chain reaction. On the basis of SSU rDNA analysis, P. minutum formed a clade together with the Diplopsaloideae, not grouping together with the other Protoperidinium species. LSU rDNA-based phylogenies indicate P. minutum as early divergent within the Protoperidiniaceae. The evolutionary significance of round brown spiny cysts produced by P. minutum-like species and diplopsalids is discussed. [ABSTRACT FROM AUTHOR]

Abstract: A biometrical analysis of the dinoflagellate cyst Lingulodinium machaerophorum [Deflandre, G., Cookson, I.C., 1955. Fossil microplankton from Australia late Mesozoic and Tertiary sediments. Australian journal of Marine and Freshwater Research 6: 242–313.] Wall, 1967 in 144 globally distributed surface sediment samples revealed that the average process length is related to summer salinity and temperature at a water depth of 30 m by the equation (salinity/temperature) = (0.078⁎average process length+0.534) with R 2 =0.69. This relationship can be used to reconstruct palaeosalinities, albeit with caution. The particular ecological window can be associated with known distributions of the corresponding motile stage Lingulodinium polyedrum (Stein) Dodge, 1989. Confocal laser microscopy showed that the average process length is positively related to the average distance between process bases (R 2 =0.78), and negatively related to the number of processes (R 2 =0.65). These results document the existence of two end members in cyst formation: one with many short, densely distributed processes and one with a few, long, widely spaced processes, which can be respectively related to low and high salinity/temperature ratios. Obstruction during formation of the cysts causes anomalous distributions of the processes. From a biological perspective, processes function to facilitate sinking of the cysts through clustering. [Copyright &y& Elsevier]

Changes in dinoflagellate cyst forming species composition, abundance and morphology along the surface salinity gradient in the Baltic Sea, Kattegat and Skagerrak were investigated and compared with detailed surface salinity data. A strong positive correlation was found between species diversity and surface salinity ( R 2 = 0.94; n = 7) in the Baltic Sea–Kattegat–Skagerrak system. The most pronounced decrease in dinoflagellate cyst diversity occurred between Kattegat and the Arkona basin, where the surface salinity also steeply declined. Overall, the total cyst abundance decreased along the salinity gradient. However, in the Gotland and particularly in the Northern Central basin cyst concentrations were elevated compared to the surrounding basins and the cyst community was dominated by heterotrophic cyst-producing dinoflagellate species. Possible factors behind this observation are discussed, with increased nutrient supply as the most likely primary cause. In addition, surface salinity was also confirmed to influence process length development of Operculodinium centrocarpum ( R 2 = 0.86; n = 145), which was the most abundant species in this study. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we describe a new species, Archaeperidinium saanichi sp. nov. within the Archaeperidinium minutum Jörgensen 1912 species complex. We examined the morphological variation of the cyst and motile stage by incubation experiments from sediment samples collected in coastal British Columbia (Canada), and compared it to closely related species. The theca of A. saanichi is differentiated from related species by overall size, the asymmetry of the intercalary plates and the right-sulcal plate (S.d.) not touching the cingulum. We provide a key to differentiate all closely related species. A. saanichi can be readily distinguished from A. minutum by a distinctively large cyst with a broad 2a type archeopyle and regularly spaced processes with relatively broad bases and aculeate process tips. Molecular phylogenetic analyses of large and small subunit (LSU and SSU) rDNA sequences demonstrated a close affinity of this species to A. minutum; however, the relatively high level of sequence conservation in dinoflagellate rDNA sequences made these particular markers inadequate for distinguishing one species from the other. Sediment-trap data suggest that A. saanichi has a preference for cooler temperatures and lowered salinities. [Copyright &y& Elsevier]

Abstract: Resting cysts attributed to the freshwater dinoflagellate genus Peridinium were found in surface sediments from Severn Sound, southeastern Georgian Bay (Lake Huron, Laurentian Great Lakes of North America). Two distinct cyst morphotypes were present and they were assigned to Peridinium wisconsinense Eddy, 1930 and Peridinium willei Huitfeldt-Kaas, 1900 by establishing cyst–theca relationships through germinations and single-cell LSU rDNA analysis on an excysted cell of Peridinium willei. Sediments recovered from deep, sheltered portions of Severn Sound and restricted basins like Honey Harbour contained between ~750 and 8500 cysts/cm3. However, winnowing by bottom currents and high concentrations of dissolved oxygen adversely impact the dinoflagellate cyst record on the lakebed, and cyst concentrations in easily remobilized muds on bathymetric highs were <100 cysts/cm3. Down-core changes in the relative abundances of these two cyst morphotypes were attributed primarily to cultural eutrophication related to land-use changes around Severn Sound over the last six centuries. Cysts of Peridinium willei, a cosmopolitan dinoflagellate species that occurs in a broad range of temperature, pH and nutrient conditions, comprise 60–74% of the cysts identified in Ambrosia (ragweed)-rich sediments in the upper 20cm of a gravity core taken from Honey Harbour. Euro-Canadian settlement and land-clearing that began in the Midland-Penetanguishene region around A.D. 1840 are evident in the increase in Ambrosia (ragweed), Gramineae (grasses) and other herbs (non-arboreal pollen) that mark the base of the Ambrosia zone (pollen zone 4) as well as an overall increase in terrigenous flux. In addition to siltation, this terrigenous flux increased the availability of limiting nutrients to the previously oligotrophic waters of Severn Sound, leading to increased cyst flux in Honey Harbour peaking at nearly 3000 cysts/cm2/y in A.D. 1966, an order of magnitude higher than cyst fluxes prior to the Euro-Canadian Ambrosia zone. Peridinium wisconsinense was the more common dinoflagellate cyst species in Honey Harbour prior to Euro-Canadian settlement, when cyst flux was an order of magnitude lower. This is consistent with the restriction of this species to relatively warm, oligotrophic to mesotrophic lakes in North America. An earlier increase in P. willei at the expense of P. wisconsinense in the core from Honey Harbour within pollen zone 3d (~700 to ~150yBP) is attributed to earlier land-clearing by the Wendat (“Huron”), who practiced agriculture in the Penetanguishene peninsula between ~A.D. 1450–1650. The cysts of these freshwater dinoflagellates thus appear to be sensitive to cultural eutrophication. [Copyright &y& Elsevier]