Kenneth Neil Mertens

Holocene salinity changes in the southwestern black sea: A reconstruction based on dinoflagellate cysts

Abstract Dinoflagellate cysts were used as a proxy for reconstructing the salinity variations during the Holocene in the southwestern Black Sea. The aim of this study was to determine the timing of the reconnection between the Black and Marmara seas. Core GeoB 7625-2, located 50 km northeast of the mouth of the Sakarya River, was sampled with a 200-year resolution between 7.42 and 0.52 ka BP. The lower part of the core was sampled with varying resolution. A distinct change in the dinoflagellate cyst assemblages from freshwater/brackish water to saltwater was observed between ∼ 8.25 and ∼ 7.97 ka BP, which is ∼ 0.6 ka earlier than observed in other dinoflagellate cyst studies. This discrepancy may indicate the diachronous salinification of the Black Sea. The freshwater to brackish water assemblage is dominated by Pyxidinopsis psilata and Spiniferites cruciformis, while the most important euryhaline species are Lingulodinium machaerophorum and cysts of Pentapharsodinium dalei. The average process length of Lingulodinium machaerophorum was used as a salinity proxy. Both proxies suggest a gradual reconnection between the Black and Marmara seas, and these findings confirm earlier studies. Peridinium ponticum is restricted to the Black Sea; abundance fluctuations of this species were controlled by salinity variations and changes in nutrient concentrations. Earlier studies have demonstrated that the 800 to 500 year cycles observed in the sedimentary record are related to the intensity of the discharge of the Sakarya River, and linked to the North Atlantic Oscillations. Cysts of Pentapharsodinium dalei and Spiniferites spp. fluctuated synchronously with the clay layer frequency. The poor preservation of these forms may indicate shelfal transport during periods of intense river discharge. The variation in relative abundance of heterotrophic species does not correlate with the clay layer frequency, since upwelling and nutrient supply also influenced their abundances. Lingulodinium machaerophorum shows the highest relative abundances during periods with reduced river input.

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

A 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.

Differences in the chemical composition of organic-walled dinoflagellate resting cysts from phototrophic and heterotrophic dinoflagellates

Dinoflagellates constitute a large proportion of the planktonic biomass from marine to freshwater environments. Some species produce a preservable organic‐walled resting cyst (dinocyst) during the sexual phase of their life cycle that is an important link between the organisms, the environment in which their parent motile theca grew, and the sedimentary record. Despite their abundance and widespread usage as proxy indicators for environmental conditions, there is a lack of knowledge regarding the dinocyst wall chemical composition. It is likely that numerous factors, including phylogeny and life strategy, determine the cyst wall chemistry. However, the extent to which this composition varies based on inherent (phylogenetic) or variable (ecological) factors has not been studied. To address this, we used micro‐Fourier transform infrared spectroscopy to analyze nine cyst species produced by either phototrophic or heterotrophic dinoflagellates from the extant orders Gonyaulacales, Gymnodiniales, and Peridiniales. Based on the presence of characteristic functional groups, two significantly different cyst wall compositions are observed that correspond to the dinoflagellates nutritional strategy. The dinocyst wall compositions analyzed appeared carbohydrate‐based, but the cyst wall produced by phototrophic dinoflagellates suggested a cellulose‐like glucan, while heterotrophic forms produced a nitrogen‐rich glycan. This constitutes the first empirical evidence nutritional strategy is related to different dinocyst wall chemistries. Our results indicated phylogeny was less important for predicting composition than the nutritional strategy of the dinoflagellate, suggesting potential for cyst wall chemistry to infer past nutritional strategies of extinct taxa preserved in the sedimentary record.

A new heterotrophic dinoflagellate from the North-eastern Pacific, Protoperidinium fukuyoi: cyst–theca relationship, phylogeny, distribution and ecology

The cyst–theca relationship of Protoperidinium fukuyoi n. sp. (Dinoflagellata, Protoperidiniaceae) is established by incubating resting cysts from estuarine sediments off southern Vancouver Island, British Columbia, Canada, and San Pedro Harbor, California, USA. The cysts have a brown‐coloured wall, and are characterized by a saphopylic archeopyle comprising three apical plates, the apical pore plate and canal plate; and acuminate processes typically arranged in linear clusters. We elucidate the phylogenetic relationship of P. fukuyoi through large and small subunit (LSU and SSU) rDNA sequences, and also report the SSU of the cyst‐defined species Islandinium minutum (Harland & Reid) Head et al. 2001. Molecular phylogenetic analysis by SSU rDNA shows that both species are closely related to Protoperidinium americanum (Gran & Braarud 1935) Balech 1974. Large subunit rDNA phylogeny also supports a close relationship between P. fukuyoi and P. americanum. Three subgroups in total are further characterized within the Monovela group. The cyst of P. fukuyoi shows a wide geographical range along the coastal tropical to temperate areas of the North‐east Pacific, its distribution reflecting optimal summer sea‐surface temperatures of ~14–18 °C and salinities of 22–34 psu.

A review of recent freshwater dinoflagellate cysts: taxonomy, phylogeny, ecology and palaeocology

Mertens K.N., Rengefors K., Moestrup Ø. and Ellegaard M. 2012. A review of recent freshwater dinoflagellate cysts: taxonomy, phylogeny, ecology and palaeocology. Phycologia 51: 612–619. DOI: 10.2216/11-89.1 Resting stages (e.g. cysts) play an important role in the life history and ecology of phytoplankton, e.g. the survival, reproduction, genetic recombination, and dispersal of many species. Marine dinoflagellates cysts have been intensively studied by both geologists and biologists, but freshwater cysts have received less attention. There are approximately 350 freshwater dinoflagellate species, and resting cysts have been described for 84 species. We evaluated the descriptions, and we reproduced images for each cyst type. The review highlighted the importance of cyst characters for taxonomy and phylogeny. We suggested that shape, wall ornamentation and possibly the archeopyle and color were important morphological characteristics at the generic level and above. The ecology of freshwater dinoflagellate cysts was reviewed, and the ecological role of cysts was discussed. The potential of freshwater cysts for Quaternary palaeoecological reconstructions was highlighted, revealing that these could serve as useful indicators of temperature, pH and productivity.

Cyst–theca relationship and phylogenetic positions of Protoperidinium (Peridiniales, Dinophyceae) species of the sections Conica and Tabulata, with description of Protoperidinium shanghaiense sp. nov.

Abstract: The genus Protoperidinium has been divided into several sections based on the shape of the first apical plate, the number/shape of anterior intercalary plates and the presence/absence of antapical horns/spines; however, phylogenetic relationships among these sections have not been fully explored. We examined the cyst–theca relationships of seven Protoperidinium species isolated from sediments along the Chinese coast. Ten partial nuclear-encoded large subunit ribosomal DNA (LSU rDNA) sequences were obtained by single-cell polymerase chain reaction (PCR) for seven species belonging to the Conica and Tabulata sections of the genus. New cyst–theca relationships were established for Protoperidinium biconicum and Protoperidinium humile, and the former was restricted to warmer waters. Brigantedinium majusculum was identified as the cyst of Protoperidinium pentagonum; whereas, Trinovantedinium applanatum corresponded to Protoperidinium shanghaiense sp. nov. Phylogenetic analyses based on LSU rDNA sequences were carried out using maximum likelihood and Bayesian inference and revealed that the theca-based section Conica was polyphyletic, and Tabulata was monophyletic. Surprisingly, some cyst-based genera (e.g. Brigantedinium, Selenopemphix) proved to be polyphyletic.

New dinoflagellate species Protoperidinium haizhouense sp. nov. (Peridiniales, Dinophyceae), its cyst-theca relationship and phylogenetic position within the Monovela group

The number of cingular plates has been used to differentiate Protoperidinium from Peridinium and related genera. Protoperidinium is characterized by the presence of three cingular plates plus a transitional plate (3C+t). However, many Protoperidinium species have been described that exhibit different cingular plate tabulations. How these species should be classified within the genus remains unclear. To address this question, the phylogenetic relationship of four Protoperidinium species, with three or four cingular plates and lacking a transitional plate, were examined in relationship to other Protoperidinium species. These four species were germinated from cysts deposited in surface sediments collected from the East China Sea, the Bohai Sea and the Yellow Sea. Three of the isolated species, P. tricingulatum, P. americanum and P. parthenopes, were described previously. The fourth is here described as P. haizhouense sp. nov. with the plate formula Po, X, 4′, 3a, 7′′, 3C, 6S, 5′′′, 2′′′′. Differences in the cyst stages of these four species, which can be taxonomically informative, were compared. Partial large subunit ribosomal DNA sequences were obtained by single‐cell polymerase chain reaction. Maximum‐likelihood and Bayesian inference showed that these four species, P. fukuyoi and Islandinium minutum form a monophyletic clade with maximal support. The genus as a whole, however, appeared polyphyletic. Our results suggest that the presence/absence of a transitional plate is significant in the phylogeny of Protoperidinium.

Cyst-theca relationships and phylogenetic positions of Peridiniales (Dinophyceae) with two anterior intercalary plates, with description of Archaeperidinium bailongense sp. nov. and Protoperidinium fuzhouense sp. nov

Protoperidinium species with two anterior intercalary plates were originally classified by Jörgensen in the subgenus Archaeperidinium and assigned to the sections Excentrica, Avellana and Archaeperidinium by Taylor, on the basis of the relative size of anterior intercalary plates and the extent of cingulum displacement. Phylogenetic relationships among these three sections have not been fully explored. Recently, Archaeperidinium was reinstated as a genus, but several species fitting the emended description have not been transferred formally as molecular data were not available. In the present study we examined the cyst‐theca relationship of seven species with two anterior intercalary plates: four species assigned to Protoperidinium and three to Archaeperidinium, from the China Sea. Partial large subunit ribosomal DNA sequences were obtained from these seven species by single‐cell polymerase chain reaction, and for the cyst of Protoperidinium stellatum from France. Two new species, Archaeperidinium bailongense and Protoperidinium fuzhouense, were described based on both theca and cyst morphology, and the cyst‐theca relationships of A. constrictum and P. abei var. rotunda were established for the first time. Maximum‐likelihood and Bayesian inference analyses revealed that P. fuzhouense was nested within the Protoperidinium sensu stricto clade despite having only six postcingular plates, and sections Excentrica, Avellana and the genus Archaeperidinium were all monophyletic. Our results suggest that the presence/absence of a sulcal fin and antapical horns and the displacement of the cingulum are the most stable characteristics of the motile stages within the respective clades.

Cyst–theca relationship and phylogenetic positions of the diplopsalioideans (Peridiniales, Dinophyceae), with description of Niea and Qia gen. nov.

Abstract: Nine genera have been assigned to the subfamily Diplopsalioideae, but since most have not been characterized molecularly and their cyst–theca relationships are largely unknown, the phylogenetic relationships among these genera are not well understood. Here we established the cyst–theca relationships of 11 species (Boreadinium breve, Diplopelta globula, Diplopsalis lenticula, Diplopsalopsis ovata, Lebouraia pusilla, Niea acanthocysta, Niea chinensis, Niea torta, Oblea rotunda, Preperidinium cf. meunieri and Qia lebouriae) belonging to nine genera by incubating cysts collected along the coast of China. In addition, we obtained 22 large-subunit ribosomal DNA sequences from the germinated motile cells of these 11 species by single-cell polymerase chain reaction. A new genus, Niea, was erected to encompass species with a plate formula identical to that of Oblea, that is, Po, X, 3′, 1a, 6′′, 3C+t, 5′′′, 2′′′′, but with an ortho 1′. Niea chinensis was described based on both theca and cyst morphology. The genus Oblea was emended to incorporate only species with a meta 1′. As a consequence, Oblea acanthocysta and O. torta were transferred to the newly erected genus Niea. A second new genus, Qia, was established to encompass Diplopsalis lebouriae, and the genus Diplopsalis was emended, differing from Qia in the shape of the anterior intercalary (1a) plate. Phylogenetic analyses were carried out using maximum likelihood and Bayesian inference. Molecular phylogeny revealed that the diplopsalioideans were not monophyletic and were subdivided into three clades. From our results, the shape of the first apical and anterior intercalary plates and the number of apical, anterior intercalary and antapical plates were useful characteristics to distinguish the diplopsalioideans at the genus level.

Living fossils in the Indo-Pacific warm pool: A refuge for thermophilic dinoflagellates during glaciations

How important are refugia for plankton biogeography? Here for the first time we report living cysts of the fossil dinoflagellate Dapsilidinium pastielsii from Southeast Asia: Shioya Bay (Okinawa, Japan), Koror (Palau), Ambon (Indonesia), East Vietnam Sea (Vietnam), and Masinloc (the Philippines). This species, thought to have become extinct in the early Pleistocene, is the last survivor of a major early Cenozoic lineage. Its disappearance from the Atlantic following the early Pleistocene implies cooling, and the discovery of living D. pastielsii in the Indo-Pacific warm pool suggests that this unique environment with stable temperatures served as an important refuge for thermophilic dinoflagellates with a >50 m.y. lineage. This is the first record of a refugium plankton species within the Indo-Pacific warm pool.