The objective of this study was to assess the distribution patterns of dinoflagellates and ciliates communities during planktonic bloom and post-bloom development periods, in relation to environmental parameters. Their distribution was studied during spring and summer 2012, in coastal waters of Algeria at six sampling stations (four sampling layers). Overall, 116 species were identified, including 98 dinoflagellates. The species richness of microzooplankton was higher in summer (81 species: 67 dinoflagellates, seven tintinnids and seven ciliates) than in spring (76 species: 72 dinoflagellates, three naked ciliates and one tintinnid). Significant difference in total abundances was observed between spring (median = 145 ind l−1) and summer (median = 90 ind l−1) but no significance (P > 0.05, Mann–Whitney test) in Shannon–Wiener (H′spring: 3.31 bits ind−1; H′summer: 3.70 bits ind−1) and evenness (Espring: 0.77; Esummer: 0.84) indices. The ciliate average abundance was higher in summer (11.3 ind l−1) than in spring (1.95 ind l−1), whereas dinoflagellate average abundance was lower in summer (127.92 ind l−1) than spring (190.19 ind l−1). Non-metric multidimensional scaling was used to identify different sample assemblages. It showed that temperature and salinity influenced the distribution pattern in the canonical correspondence analysis followed by chlorophyll a, silicate and nitrate concentrations. Our framework provides insight regarding trait trade off with implications for feedbacks to ecosystems, aiming to bridge the gap of plankton community ecology in Algeria. It elaborates a taxonomic list of dinoflagellates and ciliates in the marine pelagic ecosystem and performs their ecological characterization in their environment.

The present paper, dedicated to the legacy of local geologist–engineer Peter Jozef (Sjeuf) Felder, who died in 2009, confirms his view that bioclasts constitute a valuable tool in the correlation of outcrops and borehole cores across the type area of the Maastrichtian Stage in the vicinity of Maastricht. His approach of interpreting changes in bioclast contents as having been influenced by Milankovitch cyclicity has here been applied successfully to the entire sedimentary complex of Maastrichtian (latest Cretaceous) age in the study area. In the present approach, results are corroborated by index fossils, mainly dinoflagellate cysts but also calcareous nannofossils, which allow correlation with the Stevns-1 core reference section in eastern Denmark. With the exception of local remnants of Belemnella obtusa Zone age, the Maastrichtian Stage in its type area encompasses the last 4.6 Ma of the Cretaceous Period (i.e. the Belemnella sumensis/Acanthoscaphites tridens Zone up to the K/Pg boundary). P.J. Felder's bioclast analyses have enabled the detection of twelve 400 kyr eccentricity cycles of Milankovitch cyclicity in the area. However, the section is not continuous; there is a hiatus of c.700 kyr between the Gulpen and Maastricht formations at the ENCI-HeidelbergCement Group quarry. In addition, smaller hiatuses, usually in the range of several 20 kyr cycles, have been detected in the upper Maastricht Formation.

Analysis of multiple proxies shows that eastern equatorial Atlantic upwelling was subdued during isotope stage 5.5, more intense during stages 4, 5.2, 5.4, and 6, and most intense early in stage 2. These findings are based on proxy measures from a core site about 600 km southwest of Liberia. The proxies include total organic carbon content, the ratio of peridinoid and oceanic organic-walled dinoflagellate cyst species, accumulation rates of calcareous dinoflagellates, estimates of sea surface paleotemperatures, the difference in stable oxygen isotope composition between two species of planktonic foraminifera that live at different water depths, and the abundance of the planktonic foraminifera Neogloboquadrina dutertrei. Most of these parameters consistently vary directly or inversely with one another. Slight discrepancies between the individual parameters show the usefulness of a multiple proxy approach to reconstruct paleoenvironments. Our data confirm that northern summer insolation strongly influences upwelling in the eastern equatorial Atlantic Ocean.

The Amsterdam glacial basin was a major sedimentary sink from late Saalian until late Eemian (Picea zone, E6) times. The basin’s exemplary record makes it a potential reference area for the last interglacial stage. The cored Amsterdam-Terminal borehole was drilled in 1997 to provide a record throughout the Eemian interglacial. Integrated facies analysis has resulted in a detailed reconstruction of the sedimentary history.

After the Saalian ice mass had disappeared from the area, a large, deep lake had come into being, fed by the Rhine river. At the end of the glacial, the lake became smaller because it was cut off from the river-water supply, and eventually only a number of shallow pools remained in the Amsterdam basin. During the early Eemian (Betula zone, El), a seepage lake existed at the site. The lake deepened under the influence of a steadily rising sea level and finally evolved into a silled lagoon (late Quercus zone, E3). Initially, the lagoon water had fairly stable stratification, but as the sea level continued to rise the sill lost its significance, the lagoon becoming well mixed by the middle of the Corylus/Taxus zone (E4b). The phase of free exchange with the open sea ended in the early Carpinus zone (E5), when barriers developed in the sill area causing the lagoon to become stratified again. During the Late Eemian (late E5), a more dynamic system developed. The sandy barriers that had obstructed exchange with the open sea were no longer effective, and a tidally-influenced coastal lagoon formed.

The Eemian sedimentary history shown in the Amsterdam-Terminal borehole is intimately connected with the sea-level history. Because the site includes both a high-resolution pollen signal and a record of sea-level change, it has potential for correlation on various scales. Palaeomagnetic results show that the sediments predate the Blake Event, which confirms that this reversal excursion is relatively young. The U/Th age of the uppermost part of the Eemian sequence is 118.2±6.3 ka.

An oceanographic cruise conducted during June 2008 in the Gulf of Gabes revealed the existence of different water masses; the Modified Atlantic Waters (MAW) circulated in the upper 100 m in the offshore area, the Mixed Mediterranean Water (MMW) was confined to the inshore region and the Ionian Water (IW) was in deep offshore water. The thermal stratification was indicated by the vertical profiles of temperature generated from a coast-offshore section. Phosphorus limitation was induced by the thermal stratification as shown by the high N/P ratio. Heterotrophic and mixotrophic dinoflagellates were the major contributors to total phytoplankton biomass. Ciliates were less abundant and dominated by tintinnids. Small planktonic copepods (≤1.45 mm) contributed to 93.64% of total copepod abundance in the inshore area as a result of the high density of Oithona similis, Oithona nana, Clausocalanus furcatus and Euterpina acutifrons in this area characterized by warm and salty MMW. In fact, small copepods were significantly correlated to both temperature and salinity. Small copepod fraction prevailed also in the MAW contributing to 71.05% of total copepod abundance as a result of the dominance of O. nana and C. furcatus. Nonetheless, the large copepod Nannocalanus minor was more adapted to the deep IW where it contributed to 44.05% of total copepod abundance. Invasive species were encountered in the offshore region intruded by the Atlantic waters. The Atlantic copepods were scarce and less abundant reflecting the weakening of the Atlantic flow in the eastern basin of the Mediterranean.

Phytoplankton (>15 µm) was investigated in three shallow coastal areas at Admiralty Bay (AB) between the summers of 2002–03 and 2008–09. Phytoplankton abundance was low (103 cells l-1) and, over time, the prevailing cell size decreased due to a shift in phytoplankton dominant species from diatoms to dinoflagellates. In situ and remote sensing data showed that oscillations in sea surface temperature, precipitation, ice formation/melting, irradiance (cloud cover) and bottom circulation (indexed by the Antarctic Oscillation Index; AAO) were shown to govern the structure of the phytoplankton. Under negative AAO, diatoms prevailed, with the dominance of large (>80 µm) benthic diatoms (e.g. Corethron pennatum and Navicula directa) in periods of low production (102 cells l-1 in 2002–03), and medium-sized (31–80 µm) centrics (e.g. Thalassiosira spp. and Stellarima microtrias) when the abundance was higher (104 cells l-1 in 2003–04). Conversely, positive AAO led to the co-dominance of dinoflagellates and planktonic diatoms (e.g. Pseudo-nitzschia spp.) in the summers of 2007–08 and 2008–09. These results suggest that the AAO can be a good predictor of phytoplankton in coastal areas around the western Antarctic Peninsula, and may help our understanding of changes in other trophic levels of the food web.

There have been recent attempts to improve our knowledge about dinoflagellates of the order Dinophysales either in Mexican marine waters or worldwide, and although new records and even new species have reliable illustrations and descriptions, this group is so diverse that it needs to be studied in more detail. This paper is the product of the analysis of net phytoplankton material collected from coasts of the tropical Mexican Pacific (Gulf of California, Central Mexican Pacific and Gulf of Tehuantepec), and the southern Gulf of Mexico. Material was studied using light microscopy and scanning electron microscopy (SEM). Eleven taxa (10 species and one variety) of the section Hastata were fully identified, with nine species studied for the first time by electron microscopy (only Dinophysis hastata and D. schuettii had been previously studied by SEM), and including seven new records for the Mexican Pacific (Dinophysis monacantha, D. nias, D. phalacromoides, D. pusilla, D. swezyae, D. uracantha var. mediterranea, and D. uracanthoides), and one new record for the Gulf of Mexico (Dinophysis uracanthoides). Two species remain as unidentified, as only one specimen of each was found. Additionally, we studied in detail the new species, Dinophysis conjuncta sp. nov., for which a full description is provided. Descriptions, measurements, illustrations and local distribution data are provided for each species.

Surface sediments from six box cores along the north-eastern Antarctic Peninsula document the dinoflagellate cyst (= dinocyst) and other non-pollen palynomorph (NPP) content soon after overlying ice shelves collapsed. Prince Gustav Channel (PGC) and Larsen-A (LA) areas exhibited markedly different dinocyst abundances, concentrations being low in LA (0–20 cysts g-1) and high in PGC (2600–9100 cysts g-1, average: c. 3800 cysts g-1). Since similar water masses impact both areas, differences may be due to low biological productivity, limited sediment accumulation, and/or restricted fine-grain deposition at Larsen-A. Islandinium minutum (Harland & Reid in Harland et al.) Head et al. dominated dinocyst assemblages, occurring as both excysted and encysted forms (lesser abundance). Other taxa (Echinidinium cf. transparantum Zonneveld, Impagidinium pallidum Bujak, Bitectatodinium tepikiense Wilson, Operculodinium centrocarpum Wall & Dale, Brigantedinium spp., Selenopemphix antarctica Marret & de Vernal, Polykrikos? sp. A, and Polykrikos schwartzii Bütschli) were rare. Such assemblage composition is unusual compared to previously published Southern Ocean data, but may be specific to ice shelf and/or recently ice-free environments. Alternatively, it may be attributable to excessive production facilitated by environmental factors and/or abundant food, or similar cyst morphologies produced by different dinoflagellates. Accompanying NPPs included zooplankton remains, acritarchs, and freshwater algae. Tintinnid loricae were most abundant (max. 800 g-1), followed by foraminiferal linings (max. 320 g-1), and the acritarch Palaeostomocystis fritilla (Bujak) Roncaglia (max. 150 g-1). Collectively, NPPs were more abundant in PGC compared to LA samples.

Grazing experiments targeting the determination of in situ grazing rates are standard. In two separate experiments the effect of the frequently used siphon filling technique on the abundance of microzooplankton during the set-up of grazing experiments was investigated and compared to results from an alternative filling method. Hereby, water containing natural communities from Helgoland Roads, Germany (54°11.3′N 7°54.0′E), was transferred into incubation bottles using a funnel system (funnel-transfer technique (FTT)). The impact of pre-screening with a 200 µm net for excluding larger mesozooplankton grazers from the incubations was evaluated. Results show that the ciliate community was strongly affected by siphoning and pre-screening, leading to significant differences in abundance and Margalef diversity. The most affected ciliates were Lohmanniella oviformis and Myrionecta rubra, both important species in the North Sea. Dinoflagellates did not show any significant response to either siphoning or pre-screening with the exception of one athecate species. Such artificial bias in ciliate assemblages is very problematic for biodiversity consideration and grazing investigations. Simply changing the method of filling during the experimental set-up can ensure the measurement of accurate grazing rates of field abundances of microzooplankton. We thus recommend using conservative filling approaches like the FTT in experiments, especially when sensitive species are present, in order to avoid shifts in the overall microzooplankton community. Furthermore, we recommend introducing a control to evaluate the degree of changes in the target community due to the experimental set-up.

In aquatic food webs zooplankton constitutes an important link between primary producers and higher trophic levels. Copepods often dominate the zooplankton in coastal oceans and are the prey of the majority of planktivorous fish. Feeding behaviour, as well as the food quantity and quality are recognized factors that affect copepod growth, and therefore, the energy transfer efficiency throughout food webs. The natural occurrence and magnitude of these growth factors and their combined effects on marine copepods, as keystone grazers in the pelagic marine realm, are poorly understood. Here, we assessed how these different factors vary throughout the year, and then examine their relative influence upon copepods maximal growth rates. A multiple regression model, including all variables previously selected, and the inclusion of the sea temperature allowed us to estimate the pure influence of the studied factors, and the environmental effect on copepod growth rates. The results imply that ingestion of diatoms may induce a positive effect on specific growth rates of copepods, and the quality of this food item (high PUFA and HUFA availability) might explain such effect. Therefore, seasonal variability in diatom abundance, possibly driven by changes in the oceanographic regime, should be considered a critical factor controlling copepod growth in productive coastal ecosystems.

Trypanosomatid parasites possess 2 distinct iron-containing superoxide dismutases (Fe-SODs) designated SODA and SODC, both of which are targeted to their mitochondria. In contrast to SODAs that carry typical mitochondrial transit peptides, SODCs have highly unusual mitochondrial targeting signals. Our analyses clearly show that these pre-sequences are bipartite possessing a signal peptide-like domain followed by a transit peptide-like domain. Consequently, they resemble N-terminal extensions of proteins targeted to multi-membrane plastids, suggesting that trypanosomatids once contained a eukaryotic alga-derived plastid. Further support for this hypothesis comes from striking similarities in length, hydropathy profile, and amino acid composition of SODC pre-sequences to those of Euglena and dinoflagellate plastid proteins. To account for these data, we propose that the Trypanosomatidae initially possessed a gene encoding a mitochondrial Fe-SOD with a classical mitochondrial transit peptide. Before or after plastid acquisition, a gene duplication event gave rise to SODA and SODC. In a subsequent evolutionary step a signal peptide was linked to SODC, enabling its import into the plastid. When the trypanosomatid plastid subsequently was lost, natural selection favoured adaptation of the SODC N-terminal signal as a mitochondrial transit peptide and re-targeting to the mitochondrion.

Despite a recent revision of the dinoflagellates of the order Dinophysiales on Mexican coasts and a checklist of dinoflagellates from the Mexican Pacific, many records still need to be confirmed, for there are very few reliable illustrations and/or descriptions. In this paper, species composition and distribution of dinoflagellates belonging to the Dinophysiales, the product of the analysis of net phytoplankton material collected from coasts of the tropical Mexican Pacific (Jalisco to Chiapas) are presented. The material has been studied using light microscopy, although a few species were also studied by scanning electron microscopy (SEM). Forty-one species from five genera were identified, with two new records annotated for the Mexican Pacific: Amphisolenia thrinax and Metaphalacroma skogsbergii, and two new species of the genus Amphisolenia, Amphisolenia fusiformis sp. nov. and Amphisolenia michoacana sp. nov. Illustrations, dimensions and distribution data are provided for each species, and descriptions of the new species are also given. Amphisolenia palmata, A. rectangulata, A. truncata, Dinophysis apicata, D. hindmarchii, Histioneis biremis, H. crateriformis, H. pulchra, Ornithocercus cristatus, O. heteroporoides and O. orbiculatus are illustrated for the first time in the waters of the Mexican Pacific. The number of species found in this study is relatively low. The species Dinophysis norvegica and D. sacculus, reported in previous papers, do not seem to occur in Mexican waters, as their distribution is rather limited to the Mediterranean Sea and the North Atlantic, respectively. Finally, the identity of certain species of Dinophysis and the nature of the new species described here are discussed.

Organic-walled palynomorph assemblages from the Kasterlee Formation in northern Belgium provide new insights into the Late Miocene depositional history and palaeoenvironments of the southernmost North Sea Basin. Ranges of key dinoflagellate cysts constrain the unit between 7.5 and 5.32 Ma, that is, a latest Tortonian to Messinian age. The palynomorph assemblage is characterized, amongst others, by Geonettia clineae, an opportunistic species that thrives in mesotrophic, coastal embayments with a low sediment influx. This environmental setting is corroborated by the notable presence of Gramocysta verricula, a species with preference for shallow marine environments. The occurrence of species of the fresh water green alga Pediastrum indicates manifest river discharge in a near-shore environment or embayment. The coastal depositional environment mirrored by the palynomorphs of the Kasterlee Formation succeeds the distinct transgressive and fully marine environments of the underlying Diest Formation in the Campine area. The results from the palynological study, combined with lithological and geophysical data, show that both Upper Miocene formations are two distinct depositional cycles separated by an erosional or regressive phase. The upper boundary of the Kasterlee Formation is correlated with the Me2 sequence boundary at 5.73 Ma. The Kasterlee Formation is herein formally moved from the Lower Pliocene series to the Upper Miocene series. The coastal environment, probably characterized by a shoaling phase, recorded at the border of the southern North Sea Basin, matches the global record of regressive phases in Messinian sedimentary sequences, which are linked to cooling and increasing global ice volume.

The presence of intracellular bacteria in the dinoflagellate Gyrodinium instriatum Freudenthal & Lee has previously been described but the bacterial flora associated with this species has not been characterized. In this study, new results of transmission electron microscopy (TEM) and in situ hybridization using several bacterial group-specific oligonucleotide probes are presented. The long-term association of endocytoplasmic and endonuclear bacteria with G. instriatum has been confirmed. All endonuclear and most of the endocytoplasmic bacteria labelled were identified as belonging to the betaproteobacteria. Large clusters of Cytophaga-Flavobacterium-Bacteroides (CFB) were labelled and observed in the cytoplasm of the dinoflagellate cells, but were absent from the nucleus. Gammaproteobacteria were only observed outside the dinoflagellates. No alphaproteobacteria were detected either free-living or intracellular. Empirical observation of intracellular CFB reflected a degradation process of moribund dinoflagellate cells, whereas the systematic colonization of dinoflagellate nucleoplasm by betaproteobacteria suggested a true symbiotic relationship. Natural colonization may have occurred, perpetuated by vertical transmission of intracellular bacteria to the dinoflagellate daughter cells, via a pool of bacteria sequestered within the nucleus. Dividing bacteria were observed in the nucleus and equilibrium may be maintained by release of endonuclear bacteria to the cytoplasm through nuclear envelope constrictions.

There is increasing evidence that bacterial–algal interactions play a role in Harmful Algal Bloom (HAB) ecology. Bacteria that are associated with bloom-forming algal species, specifically toxic dinoflagellate algae, have been implicated in the production and biotransformation of paralytic shellfish toxins (PSTs). To clarify the role that these bacteria may play in the production of PSTs, it is desirable to identify and localize the bacteria associated with the dinoflagellates and enumerate them during the course of the algal blooms that the toxic dinoflagellates produce. Because 16S rRNA-targeted probes offer the possibility of both, we previously made and tested probes for some putatively toxigenic bacteria isolated from cultures of the PSP-related dinoflagellates Alexandrium tamarense, A. affine and A. lusitanicum. The bacteria isolated from the dinoflagellates belong primarily to the alpha-proteobacterial group of Roseobacter and the gamma-proteobacterial group of Alteromonas. Here, we report the successful application of these probes to Lugol's-fixed seawater samples. We detected these bacteria in high numbers in the water column when Alexandrium spp. were both present and absent, and during periods when mussels contained PSTs.

The ultrastructure of Peridinium cinctum, was examined by serial sectioning with particular emphasis on the detailed construction of the flagellar apparatus. The pusular system of P. cinctum included two sac pusules in open connection with the flagellar canals; disorganized material was found inside the pusules and near the flagellar pores, indicating excretory activity of the pusules. Several cells had replicated basal bodies, which were oriented toward the cell apex. The functional basal bodies formed an angle of about 65° and were linked by a layered connective, a structure so far seen only in peridinioids. A transverse microtubular root looped around the transverse flagellar canal and nucleated several rows of microtubular extensions that lined most of the transverse sac pusule. A single-stranded root was associated with the surface of the longitudinal basal body almost at a right angle to the basal body triplets. A fibrous connective between the transverse striated root and the longitudinal microtubular root was absent. The striated collars encircling the flagellar pores had a complex structure and were linked by a large connective; a smaller fibrous connective was also found in one cell. An extension of the longitudinal striated collar lined part of the longitudinal sac pusule; it showed a tubular substructure and was perhaps contractile. Bacteria were present in the peripheral cytoplasm of the cell, enveloped by several unit membranes and surrounded by vacuoles; near the sac pusules they appeared disorganized with aggregated ribosomes, possibly the result of digestion.

Batch culture experime nts were conducted with Alexandrium ostenfeldii, a toxic, marine dinoflagellate common in Danish waters. Growth occurred at 11·3–23·7 °C and from 10 to 40 psu.Maximum division rates of more than 0·3 di visions d−1took place at 20 °C and 15–20 psu. Growth phase variations resulted in mean cell sizes from 12 × 103 to 20 × 103 μm3. Variations in cell size were observed at differ ent temperatures and salinities, and mean cell size was closely correlated with division rate for all temperatures investigated (11·3–23·7 °C) and for salinities between 10 and 30 psu. Sexual stages, fusing gametes and planozygotes were observed in nutrient-deficient cultures of A. ostenfeldii from New Zealand, but mixing of two Danish nutrient-deficient, clonal cultures did not result in mating. Sexual fusion did not lead to the formation of resting c ysts, which are presently known only from nature. Temporary cysts were very common in ageing cultures and in unfavourable environmental conditions that did not permit growth. These cysts showed a high degree of morphological variability. When st ained with calcofluor, the cysts revealed a surface pattern. Germination of temporary cysts caused the release of a naked, biflagellate stage. At germination, the transverse flagellum was located outside the cingulum, next to the longitudinal fl agellum. The transverse flagellum became positioned in the cingulum only after the cell was clear of the cyst wall.