DISTRIBUTION AND GENETIC DIVERSITY OF THE LUCIFERASE GENE WITHIN MARINE DINOFLAGELLATES1

Dinoflagellates are the most abundant protists that produce bioluminescence. Currently, there is an incomplete knowledge of the identity of bioluminescent species arising from inter‐ and intraspecific variability in bioluminescence properties. In this study, PCR primers were designed to amplify the dinoflagellate luciferase gene (lcf) from genetically distant bioluminescent species. One of the primer pairs was “universal,” whereas others amplified longer gene sequences from subsets of taxa. The primers were used to study the distribution of lcf and assess bioluminescence potential in dinoflagellate strains representing a wide variety of taxa as well as multiple strains of selected species. Strains of normally bioluminescent species always contained lcf even when they were found not to produce light, thus demonstrating the utility of this methodology as a powerful tool for identifying bioluminescent species. Bioluminescence and lcf were confined to the Gonyaulacales, Noctilucales, and Peridiniales. Considerable variation was observed among genera, or even species within some genera, that contained this gene. Partial sequences of lcf were obtained for the genera Ceratocorys, Ceratium, Fragilidium, and Protoperidinium as well as from previously untested species or gene regions of Alexandrium and Gonyaulax. The sequences revealed high variation among gene copies that obscured the boundaries between species or even genera, some of which could be explained by the presence of two genetic variants within the same species of Alexandrium. Highly divergent sequences within Alexandrium and Ceratium show a more diverse composition of lcf than previously known.     

Cyst and radionuclide evidence demonstrate historic Gymnodinium catenatum dinoflagellate populations in Manukau and Hokianga Harbours, New Zealand

Between May 2000 and February 2001, a major bloom of the toxic dinoflagellate Gymnodinium catenatum (a causative organism of Paralytic Shellfish Poisoning, PSP) affected over 1500 km of coastline of New Zealand’s North Island. As this was the first record of this species in New Zealand, we aimed to resolve whether this represented a recent introduction/spreading event or perhaps an indigenous cryptic species stimulated by environmental/climatic change. To answer this question, we analysed for G. catenatum resting cysts in ²¹⁰Pb dated sediment cores (18–34 cm long; sedimentation rates 0.34–0.69 cm per year) collected by SCUBA divers from Manukau Harbour, where the species was first detected, and from Hokianga Harbour, where the highest shellfish toxicity was recorded, while using Wellington Harbour as a well-monitored control site. The results of this study conclusively demonstrate that abundant G. catenatum has been in northern New Zealand at least since the early 1980s, increasing up to 1200 cysts/g around the year 2000, but with low cyst concentrations possibly present since at least 1937. In contrast, Wellington Harbour cores contained only very sparse G. catenatum cysts (8 cysts/g), present only to a depth of 7 cm (surface mixed layer depth), reflecting an apparent recent range expansion of this dinoflagellate in New Zealand, possibly stimulated by unusual climatic conditions associated with the 2000 La Nina event. The significant increases since the early 1980s also of Protoperidinium cysts at Hokianga Harbour and of Gonyaulax, Protoperidinium and Protoceratium cysts at Manukau Harbour suggest a broad scale environmental change has occurred in Northland, New Zealand.     

Dinoflagellate cyst records in recent sediments from Daya Bay, South China Sea

Nine sediment cores of 8–26 cm in length were collected from two basins of Daya Bay, the South China Sea, by Tokyo University Fisheries Oceanography Laboratory core sampler in August 2001 to investigate the distribution of dinoflagellate resting cysts. In the present study, 51 different cyst morphotypes representing 22 genera were identified from 65 sediment samples. Among them, there were 21 autotrophic species and 30 heterotrophic ones. Cyst species richness in each sample varied from 12 to 29, while the values of Shannon‐Weaver diversity index (H′) were between 0.15 and 4.13. There were an obvious increase in both species richness and values of H′in 2–6 cm sediments. Cyst concentrations varied from 154 to 113 483 cysts per gram dry weight sediment, and were much higher in upper sediments. Scrippsiella trochoidea was the most dominant cyst type, which took up over 90% of cyst assemblages in the upper sediments. The abrupt increase of S. trochoidea cysts in the surface sediments reflected the bloom of this species in Daya Bay in 2000. The results from cyst assemblages showed some trend of changes in water quality in this area, and indicated a typical type of pollution caused by cultural eutrophication, which started in the 1980s and greatly accelerated in the middle of 1990s. Cysts of Alexandrium, mainly those of Alexandrium catenella and Alexandrium tamarense complex, occurred frequently and abundantly in this area, with the highest concentration and relative frequency of 503 cysts per gram dry weight sediment and 22.3%, respectively. The high abundance of Alexandrium cysts provided rich ‘seed bed’ for Alexandrium blooms and was also an important source of paralytic shellfish poisoning toxins, especially in winter.     

Resting stages of microalgae in recent marine sediments of Peter the Great Bay,Sea of Japan

Data on the qualitative and quantitative composition of resting stages of planktonic microalgae in recent marine sediments of Peter the Great Bay (Sea of Japan) over the period 2000–2007 are presented. A total of sixty one morphological forms of resting stages represented by dinoflagellate and raphidophyte cysts and diatom spores and resting cells were recorded in the sediment samples. This study revealed cysts of the potentially toxic species Alexandrium tamarense, A. cf. minutum, Alexandrium sp., Gymnodinium catenatum (PSP toxin producers), and Protoceratium reticulatum (yessotoxin producer); resting cells of Pseudo-nitzschia sp. (potential producer of domoic acid); and cysts of bloom-forming species Cochlodinium cf. polykrikoides and Heterosigma cf. akashiwo.     

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.     

Vertical distribution and germination ability of Alexandrium spp. cysts (Dinophyceae) in the sediments collected from Kure Bay of the Seto Inland Sea, Japan

The vertical distribution of Alexandrium tamarense/ catenella (hereinafter Alexandrium spp.) cysts was investigated with special attention to living cysts filled with fresh protoplasm and empty cysts. In addition, based on the incubation experiments of Alexandrium spp. cysts, the germination ability of the cysts was examined. A sediment core 63 cm in length, collected from Kure Bay of the Seto Inland Sea, West Japan, in September 2000, was provided for an analysis on the vertical distribution of Alexandrium spp. cysts. Samples from every 1 cm interval depth from the top down to 13 cm depth of the same core were taken to examine the germination ability of the cysts. Results show that Alexandrium spp. cysts were continuously observed from 59 to 60 cm depth to the top. The cyst densities in the upper parts of the core (from 9 to 10 cm depth to the top) were much more abundant those that in the lower parts (below 10–11 cm depth). The relationship between living and empty cysts in each depth did not reveal a positive correlation with the sediment depth. Based on the sedimentation rate of the core sediment (approximately 1.6 cm/year), Alexandrium spp. cysts have been produced since 1962, and a remarkable increase of these cysts was observed from ca 1993. Such a rapid increase of Alexandrium spp. cysts has probably been as a result of dense blooms of A. tamarense occurring since 1992 in Hiroshima Bay, including Kure Bay. The germination of Alexandrium spp. cysts was observed in samples collected from the top to 12–13 cm depth of the core. It suggests that the Alexandrium spp. cysts can keep the germination ability for more than 8 years.     

Culturable bacterial diversity associated with cysts of <Emphasis Type="Italic">Eurhizococcus brasiliensis</Emphasis> (Hempel) (Hemiptera: Margarodidae)

The ground-pearl Eurhizococcus brasiliensis is an important insect pest of grapes. Nowadays, its biology is still barely known and studies related to its secondary symbionts are virtually non-existent. Our main goal was to evaluate the bacterial diversity associated with cysts of E. brasiliensis using a culture-dependent approach. Six different isolation media were used and shown to be suitable for culturing bacteria associated with E. brasiliensis. A total of 39 bacteria strains were isolated and classified into 10 different morphotypes. The ISP-4 medium was the most suitable for bacteria isolation from cysts of the ground-pearl, providing the highest number of morphotypes. 16S rDNA gene analysis demonstrated a high diversity of bacteria associated with cysts, with six Pseudomonas chlororaphis isolates (the most predominant morphotype) and three different morphotypes of Bacillus spp. as the most representative genera. The phylogenetic analysis showed close affinity between the isolated morphotypes and bacterial strains usually isolated from plant and soil samples. Sphingopyxis and Stenotrophomonas were isolated for the first time from arthropods. Although it was not possible to determine the primary source of infection by these bacteria, our data suggests that these microorganisms may be transitory and acquired from the environment.     

The mycoflora of peanuts in Egypt

Twenty-six genera and Sixty-six species, in addition to two varieties of Aspergillus nidulans and one variety of Humicola grisea were isolated from 80 peanut seed (uncovered or covered within shell at the time of sampling) samples and 40 samples of shells collected from different places in Egypt.At 28 °C, the broadest spectrum of genera and species was recorded in the shells (21 genera and 53 species), followed by the naked seeds (16 genera and 38 species) and the covered seeds (17 genera and 33 species). Aspergillus and Penicillium were regularly the most common genera in the three substrates. A. niger, A. fumigatus, A. flavus A. terreus, A. ochraceus and P. funiculosum were generally the most common fungal species recovered from the three substrates. A. flavus was represented in 80%, 60% and 80% of the samples constituting 16.1%, 8.4% and 27.2% of the total count of fungi of the shells, covered and uncovered seeds respectively.At 45 °C, nine genera and sixteen species were collected of which Aspergillus fumigatus was extremely dominant in the three substrates, followed by A. terreus and A. niger. Penicillium was completely eliminated.     

Genus Alexandrium Halim, 1960 (Dinophyta) from the Pacific coast of Russia: Species composition, distribution, and dynamics

At present 8 species of Alexandrium genus have been found in seas and adjacent waters of Russia: A. acatenella, A. catenella, A. insuetum, A. margalefii, A. ostenfeldii, A. pseudogonyaulax, A. tamarense, and A. tamutum. The distribution and population density of Alexandrium species varied within the surveyed area of the Pacific: in the Sea of Japan and Sea of Okhotsk, 7 species were recorded; 3 species were recorded along the Pacific coast of Kamchatka; and 2 species were found in the Bering Sea. A. tamarense was the most widespread and abundant species over the area. A. insuetum was recorded only in the Sea of Japan, and A. catenella, in the Sea of Okhotsk (Terpeniya Bay). The highest concentration of Alexandrium spp. (2–7 million cells/l) was recorded along the Pacific coast of Kamchatka and in the Bering Sea; in the Sea of Okhotsk, a rather high concentration (51000 cells/l) was registered in Aniva Bay; in the Sea of Japan, the highest concentration was recorded in Peter the Great Bay (6000 cells/l). The distribution of cysts (spores) in surface sediments of the Pacific coast of Russia as a whole reflected the pattern of distribution of vegetative cells of Alexandrium. Cysts of Alexandrium cf. tamarense prevailed all over the area, with the maximum concentration along the Pacific coast of Kamchatka. Beyond that type of cysts, insignificant numbers of cysts of Alexandrium cf. minutum were recorded in Peter the Great Bay and Aniva Bay. Analysis of seasonal dynamics revealed that cells of Alexandrium spp. occurred in Peter the Great Bay from June up to September, and along the Pacific coast of Kamchatka from April to October. In the first region, the maximum density was recorded in August; it was provided by A. pseudogonyaulax (59% of the total density of Alexandrium), A. tamarense (35%), and A. insuetum (6%). In the second region, it was recorded in July, thanks only to development of A. tamarense.     

Deltocephalinae of New Zealand (Homoptera: Cicadellidae)

The subfamily Deltocephalinae is represented in New Zealand by 3 tribes, 9 genera, and 20 species, of which 3 genera and 13 species are new to science. All taxa are described, and keys are given for their separation. Three of the genera are endemic, 3 are Australian, 2 are Holarctic, and 1 is cosmopolitan. Nesoclutha and Macrosteles are recorded in New Zealand for the first time, and the presence of Deltocephalus is authenticated. Fourteen species are endemic, 4 are Australian, 1 is widespread in the Pacific area, and 1 is Holarctic. Nesoclutha pallida, Macrosteles fieberi, and Deltocephalus hospes are recorded in New Zealand for the first time.     

Ethnobotany of folk medicinal aquatic plants in Jordan

Eighty-seven species belonging to 59 genera and 33 plant families identified in the study area are presented. The three families with the most species represented were Labiatae (nine aquatic species), Compositae (seven species), and Salicaceae (seven species). The genera most represented wereMentha (six species),Polygonum (five species), andSalix (five species). Sixty-three folk-medicinal aquatic species (73.3%) had similar therapeutic uses in neighboring countries, while the 24 remaining species (26.7%) did not show therapeutic similarity with their use in other countries. Emerged species (plants rooted in soil under water but which emerge partially above the water’s surface) were the most recorded, while amphibious, submerged, and floating species were the least recorded. The folk-medicinal importance of the recorded aquatic species were classified by rank-order priority (ROP). Twenty-one species (24%) had ROP values higher than 50, indicating the highest popularity level in folk-medicinal potentiality; 26 species (29.9%) had therapeutic effects informed by fewer than three informants and were therefore excluded from further consideration; 40 species (46.1%) had ROP values of less than 50, and were thus classified as nonpopular medicinal plants.     

PATTERNS IN HOST RANGE FOR TWO STRAINS OF AMOEBOPHRYA (DINOPHYTA) INFECTING THECATE DINOFLAGELLATES: AMOEBOPHYRA SPP. EX ALEXANDRIUM AFFINE AND EX GONYAULAX POLYGRAMMA1

The endoparasitic dinoflagellate Amoebophrya ceratii (Koeppen) Cachon uses a number of its free‐living relatives as hosts and may represent a species complex composed of several host‐specific parasites. Two thecate host–parasite systems [Amoebophrya spp. ex Alexandrium affine (Inoue and Fukuyo) Balech and ex Gonyaulax polygramma Stein], were used to test the hypothesis that two strains of Amoebophrya have a high degree of host specificity. To test this hypothesis, a series of cross‐infection experiments were conducted, with 10 thecate and three athecate dinoflagellate species as potential hosts. Surprisingly, the two strains of Amoebophrya lacked host specificity and had wider host ranges than previously recognized. Among the host species tested, Amoebophrya sp. ex Alexandrium affine was capable of infecting only species of genus Alexandrium (Alexandrium affine, Alexandrium catenella, and Alexandrium tamarense), while the parasite from Gonyaulax polygramma infected species covering five genera (Alexandrium, Gonyaulax, Prorocentrum, Heterocapsa, and Scripsiella). In the context of previous reports, these results suggest that host specificity of Amoebophrya strains varies from extremely species‐specific to rather unspecific, with specificity being stronger for strains isolated from athecate hosts. Information on host specificity of Amoebophrya strains provided here will be helpful in assessing the possibility of using these parasites as biological control agents for harmful algal blooms, as well as in defining species of Amoebophrya in the future.     

Distribution of arbuscular mycorrhizal fungi in marshy and shoreline vegetation of Deepar Beel Ramsar Site of Assam,India

Arbuscular mycorrhizal fungal (AMF) symbiosis was thought to be rare in wetland plant roots, although several recent studies suggested that this association might be important in wetland ecosystems. In this research work we have studied the distribution of AMF in the marshy and shoreline vegetation of Deepar Beel Ramsar site of Assam, India. The study reveals the percentage of mycorrhizal colonization in the roots of different plant species which were observed from 20.89 to 86.47% and particularly found larger among the members of the family Poaceae. The Vetiveria zizanioides L. from the family Cyperaceae showed the highest (86.47%) percentage of root colonization, however, only one plant species viz. Scirpus lateriflorus Gmel. from the same family was found to be nonmycorrhizal. The rhizospheric soil samples of most of the plant species were found to be dominated by Glomus morphotypes. All total 18 AMF morphotypes were recorded which comprises four genera viz. Glomus (66.67%), Acaulospora (16.66%), Gigaspora (11.11%) and Scutellospora (5.56%). The observation of diversity of AMF in 25 different plant species among the wetland plants gives a glimpse of AMF diversity and their host selectivity in the said ecosystem.     

Survey of the mycoflora of barley grains in Egypt

The fungi of 40 samples of barley grains collected from Upper Egypt were estimated using the dilution- and the grain-plate methods. 33 genera and 109 species, in addition to 2 varieties of Aspergillus nidulans, one variety of Aspergillus flavus and one variety of Penicillium cyclopium were identified. The spectrum of fungal genera and species collected by the grain-plate method (29 genera and 94 species+3 varieties) was broader than by the dilutionplate method (27 genera and 71 species+3 varieties), but the order of frequency of occurrence of fungal genera and species was basically similar in the two methods. The most frequent genera were Aspergillus (25 species+3 varieties), Penicillium (32 species+1 variety), Rhizopus (2 species), Alternaria (2 species), Fusarium (6 species) and Drechslera (5 species) and were represented (as assayed by the grainplate method) in 100 %, 77.5 %, 85 % 62,5 %, 60 % and 52.5 % of the samples constituting 60.4 %, 10.2 %, 7.7 %, 3.7 %, 5 % and 2.3 % of the gross total count of fungi respectively. From the preceding genera A. niger, A. fumigatus, A. flavus, A. sydowii, P. notatum, P. citrinum, F. oxysporum, F. moniliforme, F. solani, R. stolonifer, A. alternata and D. spicifera were the most frequent.     

Dinoflagellate cysts in recent marine sediments of the western coast of the Bering Sea

The quantitative and qualitative composition of live dinoflagellate cysts was studied in the upper two-centimeter layer of recent marine sediments that were collected at 19 stations in the coastal waters of the western Bering Sea. A total of 28 types of identified cysts belonged to the following 11 genera: Alexandrium, Diplopsalis, Ensiculifera, Gonyaulax, Gyrodinium, Pentapharsodinium, Polykrikos, Preperidinium, Protocera- tium, Protoperidinium, and Scrippsiella. The morphology of dinoflagellate cysts from recent sediments of Russian seas, such as the shape, the size, and also the structure of the phragma, including the processes and the archeopyle, was described comprehensively for the first time. Cysts of the species Gonyaulax spinifera, Pentapharsodinium dalei, Protoceratium reticulatum, Protoperidinium americanum, P. conicoides, P. subinerme, Scrippsiella crystallina, and S. trochoidea were the most widespread. Those of the potentially toxic species Alexandrium tamarense were also widely distributed and prevailed in the studied area. Their concentration varied from 0 to 25 860 cells/cm³; the maximum concentration was recorded in Pavel Bay, Koryak Okrug, and Kamchatka.     

Population dynamics of potentially harmful algal blooms in Bizerte Lagoon,Tunisia

The population dynamics of potentially harmful phytoplankton in the semi-closed, coastal Bizerte Lagoon, Tunisia, in the south-western Mediterranean, were examined from November 2007 to February 2009 at six sampling stations, three situated in areas of mussel and oyster farming. The harmful species monitored included the potential producers of amnesic shellfish poisoning (Pseudo-nitzschia spp.), paralytic shellfish poisoning (Alexandrium spp.), diarrheic shellfish poisoning (Dinophysis spp. and Prorocentrum spp.), ichthyotoxins (Cochlodinium polykrikoides, Akashiwo sanguinea and Karenia mikimotoi), yessotoxins (Gonyaulax spinifera) and the discolouration of water (Neoceratium lineatum and Protoperidinium sp.). These were numerically dominated by potentially toxic species of the diatom genus Pseudo-nitzschia, which were present year-round at all stations. Prorocentrum spp., Dinophysis spp. and Neoceratium lineatum were the most abundant and recurrent harmful dinoflagellates, exhibiting their highest densities at the shellfish farming stations. Alexandrium spp. bloomed only on one occasion, reaching its highest densities at a shellfish farming station. Canonical correspondence analyses revealed significant relationships between the harmful phytoplankton species monitored and the environmental conditions. The widespread distribution of harmful phytoplankton in Bizerte Lagoon, with the permanent presence of Pseudo-nitzschia spp. and the high frequency of dinoflagellate blooms in the shellfish areas, suggests a potential risk of shellfish poisoning events in the region.     

MOLECULAR PHYLOGENY OF THE HETEROTROPHIC DINOFLAGELLATES,PROTOPERIDINIUM, DIPLOPSALIS AND PREPERIDINIUM (DINOPHYCEAE), INFERRED FROM LARGE SUBUNIT rDNA1

The genera Protoperidinium Bergh, Diplopsalis Bergh, and Preperidinium Mangin, comprised of species of marine, thecate, heterotrophic dinoflagellates in the family Protoperidinaceae Balech, have had a confused taxonomic history. To elucidate the validity of morphological groupings within the Protoperidinium and diplopsalids, and to determine the evolutionary relationships between these and other dinoflagellates, we undertook a study of molecular phylogeny using the D1–D3 domains of the large subunit (LSU) of the rDNA. Based on morphology, the 10 Protoperidinium species examined belonged to three subgenera and five morphological sections. Two diplopsalid species were also included. Single‐cell PCR, cloning, and sequencing revealed a high degree of intraindividual sequence variability in the LSU rDNA. The genus Protoperidinium appeared to be recently divergent in all phylogenetic analyses. In maximum parsimony and neighbor joining analyses, Protoperidinium formed a monophyletic group, evolving from diplopsalid dinoflagellates. In maximum likelihood and Bayesian analyses, however, Protoperidinium was polyphyletic, as the lenticular, diplopsalid heterotroph, Diplopsalis lenticula Bergh, was inserted within the Protoperidinium clade as basal to Protoperidinium excentricum (Paulsen) Balech, and Preperidinium meunieri (Pavillard) Elbrächter fell within a separate clade as a sister to the Oceanica and Protoperidinium steidingerae Balech. In all analyses, the Protoperidinium were divided into two major clades, with members in the Oceanica group and subgenus Testeria in one clade, and the Excentrica, Conica, Pellucida, Pyriforme and Divergens sections in the other clade. The LSU rDNA molecular phylogeny supported the historical morphologically determined sections, but not a simple morphology based model of evolution based on thecal plate shape.     

Differential abundance and core members of the bacterial community associated with wild male Zeugodacus cucurbitae fruit flies (Insecta: Tephritidae) from three geographical regions of Southeast Asia

Zeugodacus cucurbitae (Coquillet) is one of the most significant and widespread tephritid pest species of agricultural crops. This study reports the bacterial communities associated with Z. cucurbitae from three geographical regions in Southeast Asia (Thailand, Peninsular Malaysia, and Sarawak). The bacterial microbiota were investigated by targeted 16S rRNA gene (V3–V4 region) sequencing using the Illumina Mi-Seq platform. At 97% similarity and filtering at 0.001%, there were seven bacterial phyla and unassigned bacteria, comprising 11 classes, 23 orders, 39 families and 67 genera. The bacterial diversity and richness varied within and among the samples from the three geographical regions. Five phyla were detected for the Sarawak sample, and six each for the Thailand and Peninsular Malaysia samples. Four phyla—Actinobacteria, Bacteroidetes, Firmicutes, and Proteobacteria—were represented in all the fruit fly specimens, forming the core members of the bacterial community. Proteobacteria was the predominant phylum, followed by Bacteroidetes, Firmicutes, and Actinobacteria. Fifty-three genera were represented in the Thailand sample, 56 in the Peninsular Malaysia sample, and 55 in the Sarawak sample. Forty-two genera were present in all the three geographical regions. The predominant core members were order Enterobacteriales (Proeteobacteria), and family Enterobacteriaceae (Enterobacteriales). Klebsiella (Enterobacteriaceae) was the predominant genus and K. oxytoca the predominant species with all specimens having?>?10% relative abundance. The results indicate the presence of a great diversity as well as core members of the bacterial community associated with different populations of Z. cucurbitae.

     

Late Quaternary Protoperidinium cysts as indicators of paleoproductivity in the northern Arabian Sea

The reliability of organic-walled cysts of the heterotrophic dinoflagellate Protoperidinium as paleoproductivity indicators and the influence of bottom water oxygenation on cyst preservation is assessed by using Arabian Sea records of the past 125 kyr as a natural laboratory. Multidisciplinary geochemical, micropaleontological and palynological datasets are integrated to analyze the relationship between Protoperidinium cyst concentrations and other paleoproductivity proxies. Differential preservation potential is quantified in order to establish threshold oxidative degradation values for a possible application of quantitative Protoperidinium cyst records in paleoenvironmental reconstructions. Results indicate that variations in Protoperidinium cyst concentration closely correspond to other marine productivity and/or upwelling proxies. Although oxygenation will lead to significant cyst degradation, and thus decreased concentrations, down-core patterns in Protoperidinium cyst concentration still primarily reflect changes in sea surface productivity. In view of differential preservation among dinoflagellate cysts, down-core variations in relative abundance of Protoperidinium should be treated with caution.