中国渤海海域甲藻孢囊的种类多样性和生态地理分布

在渤海湾24个站位采集0–10 cm表层沉积物144份样品, 进行甲藻孢囊的种类多样性和生态地理分布研究, 并分析渤海海域水体的富营养化趋势。在渤海海域共采集鉴定出6类32种甲藻孢囊, 包括原多甲藻类孢囊11种、裸甲藻类孢囊6种、膝沟藻类孢囊7种、钙质类孢囊5种、翼藻类孢囊2种及Tuberculodinioid类孢囊1种。其中, 自养型甲藻孢囊17种, 优势种为锥状斯氏藻(Scrippsiella trochoidea)孢囊, 丰富的孢囊库为锥状斯氏藻赤潮提供种源, 可作为该海域发生锥状斯氏藻赤潮的参考依据; 异养型甲藻孢囊15种, 优势种为无纹多沟藻(Polykrikos schwartzii)和锥形原多甲藻(Protoperidinium conicum)孢囊; 发现1种产麻痹性贝类毒素的孢囊--塔玛亚历山大藻(Alexandrium tamarense)孢囊, 但是仅在S6、S8和S14三个站位发现, 且孢囊数量较少。渤海甲藻孢囊组成与世界其它海域相似, 异养型甲藻孢囊种类丰富, 提示渤海海域富营养化程度较高。每个站位沉积物样品分为3层(每层约3 cm), 春夏两季表层、中层和底层之间孢囊组成差异不大, 平均种类数为5.58–7.29, 孢囊的平均密度范围在58.82–103.57 cysts·g^–1 DW之间; 孢囊种类丰富的站点, 孢囊密度也较高, 如S9、S14站位。对渤海海区表层沉积物中甲藻孢囊的生物多样性进行了统计分析, 发现表、中、底3层甲藻孢囊的平均种类多样性指数在春季(5月)分别为1.69、1.61和1.52; 略低于夏季(8月)的1.83、1.89和1.60。     

High diversity dinoflagellate cyst assemblages from the Late Triassic of southern England: new information on early dinoflagellate evolution and palaeogeography

Abundant and diverse dinoflagellate cyst assemblages from the Rhaetian of southern England are characterized by the occurrence of a new species of Rhaetogonyaulax, some undescribed taxa and numerous forms with Arctic and Australasian affinities. The dinoflagellate cyst assemblages permit a discussion of the palaeogeographic distribution of dinoflagellate cysts in the Late Triassic. The hypothesis on a Late Triassic migration event of organic walled microplankton from higher latitudes to the Boreal domain is presented.     

Distributions of calcareous dinoflagellate cysts in surface sediments of the western equatorial Atlantic Ocean,and their potential use in palaeoceanography

Only very few studies focus on recent calcareous dinoflagellate cyst diversity, geographic distribution and ecology, so that information on the distribution patterns and environmental affinities of individual cyst species is extremely limited. This information is, however, essential if we want to use calcareous dinoflagellate cysts for palaeoenvironmental reconstruction. Surface sediment samples from the generally oligotrophic western equatorial Atlantic Ocean, offshore northeast Brazil, were therefore quantitatively analysed for their calcareous dinoflagellate cyst content, including the calcareous vegetative coccoid Thoracosphaera heimii. Seven calcareous dinoflagellate cyst species/morphotypes and T. heimii were encountered in high concentrations throughout the area. Substantial differences in the distribution patterns were observed. The highest concentrations of cysts are found in sediments of the more oligotrophic, oceanic regions, beyond the influence of Amazon River discharge waters. Dinoflagellates producing calcareous cysts thus appear to be capable of surviving low nutrient concentrations and produce large numbers of cysts in relatively stable and predictable environments affected by minimal seasonality. To test for the environmental affinities of individual species, distribution patterns in surface sediments were compared with temperature, salinity, density and stratification gradients within the upper water column (0–100 m) over different times of the year, using principal components analysis and redundancy analysis. T. heimii and four of the seven encountered cyst species (Sphaerodinella? albatrosiana, two morphotypes of Sphaerodinella? tuberosa and Scrippsiella regalis) relate to these parameters significantly and the variations in the cyst associations appear to be associated with the different surface water currents characterising the area. The results imply that calcareous dinoflagellate cyst distributions can potentially be used to distinguish between different open oceanic environments and they could, therefore, be useful in tracing water mass movements throughout the late Quaternary.     

大窑湾养殖区赤潮甲藻孢囊种类组成及分布的研究

2006—2007年对大窑湾养殖区的甲藻孢囊进行了研究,结果检出10种甲藻孢囊,分属于4大类9种甲藻孢囊,其中原多甲藻类孢囊2种,膝沟藻类孢囊5种,钙质类孢囊1种,裸甲藻类孢囊1种,一种艉杆藻(Ensiculifera Balech)和一种易碎藻(Fragilidium mexicanum)是中国沿海新记录的两个种类,此外还有一种无法鉴定到种的一种原多甲藻孢囊。膝沟藻类孢囊的种类数占绝对优势,占50%,其次是原多甲藻类孢囊占30%,钙质类孢囊和裸甲藻类孢囊各占10%。10种孢囊中有3种异养型孢囊和7种自养型孢囊。并发现两种产麻痹性贝毒(PSP)的孢囊—塔玛亚历山大藻/链状亚历山大藻复合体(Alexandrium tamarense/A.catenella)和链状裸甲藻(Gymnodinium catenatum)。孢囊密度的季节分布呈现明显的双峰型,在2007年1月份和2007年的8月份出现了两个高峰。2007年的1月份达到了调查全年的孢囊密度最高值,达到了1.09×103 cysts/g湿重,2007年的8月份出现的第二次高峰期孢囊密度达到了0.86×103 cysts/g湿重。孢囊密度最低值出现在2007年的10月,只有280 cysts/g湿重。全年孢囊平均密度为695.5 cysts/g湿重。甲藻孢囊的多样性指数除了2007年的9月和10月以外,相差不大,变化范围为0.17—0.55,全年的平均值为0.46。     

First report of fossilized cysts produced by the benthic Bysmatrum subsalsum (Dinophyceae) from a shallow Mexican lagoon in the Gulf of Mexico

Cysts belonging to the benthic dinoflagellate Bysmatrum subsalsum were recovered from palynologically treated sediments collected in the Alvarado Lagoon (southwestern Gulf of Mexico). The cysts are proximate, reflecting the features of the parent thecal stage, and their autofluorescence implies a dinosporin composition similar to the cyst walls of phototrophic species. This finding is important for our understanding of B. subsalsum life cycle transitions and ecology. Encystment may play an important role in the bloom dynamics of this species as it can enable the formation of a sediment cyst bank that allows reinoculation of the water column when conditions become favorable. This is the first report of a fossilized cyst produced by a benthic dinoflagellate recovered from sub‐recent sediments.     

Organic-walled dinoflagellate cysts from the Upper Cretaceous–lower Paleocene succession in the western External Rif,Morocco: New species and new biostratigraphic results

Palynological investigation of the Upper Cretaceous–lower Paleocene succession from the Tahar section near Arba Ayacha in northwestern Morocco (westernmost External Rif Chain) reveals the presence of rich, diverse and well-preserved dinoflagellate cyst assemblages. For the first time in the study region, biostratigraphic interpretations based on the dinoflagellate cyst assemblages from the studied interval allow the recognition of the upper Maastrichtian and Danian. Relevant upper Maastrichtian–Danian global dinoflagellate cyst events include: the First Appearance Datum of the upper Maastrichtian species Disphaerogena carposphaeropsis, Glaphyrocysta perforata, and Manumiella seelandica; the Last Appearance Datum of the Cretaceous taxa Dinogymnium spp., Isabelidinium cooksoniae, and Pterodinium cretaceum; and the First Appearance Datum of the earliest Danian markers Carpatella cornuta, Damassadinium californicum, Membranilarnacia? tenella, and Senoniasphaera inornata. We formally describe the biostratigraphical range and potential of two new dinoflagellate cyst species, namely Nematosphaeropsis silsila Guédé and Slimani nov. sp., and Pterodinium ayachensis Guédé and Slimani nov. sp. Both species are found in the westernmost External Rif Chain and are restricted to the upper Maastrichtian.     

THE UNIQUE,MICRORETICULATE CYST OF THE NAKED DINOFLAGELLATE GYMNODINIUM CATENATUM1

Gymnodinium catenatum Graham is an unarmored dinoflagellate responsible for episodes of paralytic shellfish poisoning. This species forms a resting cyst that is unique in several ways. The outer surface of the spherical, brownish cyst is microreticulate and composed of hundreds of 1-3 μm polygons. In several regions, these polygons are smaller, more uniform in shape, and oriented in distinct bands that define morphological features. These features on the cyst reflect the cingulum, sulcus, flagellar pore complex, and acrobase of the motile stage precursor to the cyst. The archeopyle is irregularly but extensively developed. Its margin is generally smooth and extends almost completely around the circumference of the cyst, though not consistently in the plane of the equator. The cyst wall is resistant to acetolysis and standard palynological preparation techniques. Gymnodinium catenatum Graham is emended to include the details of the cyst stage. The significance of this cyst is that it is the first described cyst of a naked dinoflagellate that bears oriented surface ornamentation reflecting features of the motile dinoflagellate. Its microreticulate surface ornamentation is unique to dinocysts, naked or armored, living or fossilized. Resistance of the cyst wall to harsh processing techniques suggests the presence of sporopollenin-like material commonly associated with cysts of armored dinoflagellates. From an ecological standpoint, the existence of a G. catenatum cyst has important implications with respect to species bloom dynamics and geographic distribution. In addition, the distinct differences between this cyst and those of the armored saxitoxin-producing gonyaulacoid species argues against a proposed evolutionary linkage.     

Modern dinoflagellate cysts in hypertrophic coastal waters of Tokyo Bay, Japan

A survey of dinoflagellate resting cysts in surface sedimentsamples was carried out in Tokyo Bay, Japan, to document theirhorizontal distribution. At least 21 different cyst types werefound. Dominant cyst types allowed the recognition of assemblageswhich form three different dinoflagellate cyst communities:the innermost part of the Bay, the central area and the moutharea. In all stations in Tokyo Bay, heterotrophic dinoflagellatecysts always occupied more than half of the cyst populations.Cysts of Polykrikos schwartzii/kofoidii are the most abundantheterotrophic species. These assemblages may reflect highlynutrient-enriched (hypertrophic) and turbulent water conditions.Among the cyst types found were probable ellipsoidal cysts ofAlexandrium tamarense. This is the first record of toxic Alexandriumspecies cysts in Tokyo Bay sediments.     

Callovian (Middle Jurassic) marine microplankton from southwestern Germany: Biostratigraphy and paleoenvironmental interpretations

Late Middle Jurassic dinoflagellate cyst assemblages are documented from a section in Kandern and in samples from additional localities in southern Germany. The changes in the composition of the marine microfloras through the Callovian sections are related to fluctuations in sea-levels and changes in depositional environments. The Lower Callovian claystones, which represent inner shelf, soft bottom deposits, contain rich, diverse and well preserved dinoflagellate cyst assemblages. In the Kandern section a marked transition from the Lower Callovian claystone facies to the Anceps-oolite occur within the Calloviense zone. This transition was caused by a regression, and coincides with the LZA−3.1/LAZ−3.2 boundary on the cycle chart of Haq et al. (1987). Diverse dinoflagellate cyst assemblages also occur in the Anceps-oolite, but they are not so abundant as the acritarchs which dominate the overall palynofloras. The Anceps-oolite is interpreted as representing an offshore, but shallow marine environment. The transition to the overlying Upper Callovian “Renggeri Clay” is more gradual, but accompanied by marked changes in the overall composition of the marine microfloras. The “Renggeri Clay”, which represent an outer shelf, soft bottom depositional environment, shows a higher species diversity and abundance of dinoflagellate cysts than the underlying sequences. The distribution pattern of selected species through the Kandern section indicates that some species were related to specific environments, i.e. open marine forms, and that others could have been opportunistic forms, tolerating more shallow marine environments.

The distribution of the dinoflagellate cysts from southern Germany is related to the standard Northwest European ammonite zonation. The ranges of selected biostratigraphic key species are compared with ranges previously reported from the British and northwest European Jurassic. There are several discrepancies with respect to the earliest appearance and extinction datums, the only relevant Callovian palynostratigraphic “events” coinciding in southern Germany and Britain being: The extinction of Aldorfia aldorfensis at the top of the Calloviense zone, and the earliest incoming of Belodinium spp. and Liesbergia scarburghensis at the base of the Lamberti zone.     

Quaternary (Flandrian?) dinoflagellate cysts from the Grand Banks,off Newfoundland,Canada

A well-preserved assemblage of dinoflagellate cysts, probably of Flandrian age, was recovered from two piston cores on the Grand Banks, off Newfoundland, Canada. The assemblage, dominated by the dinoflagellate cyst species Operculodinium centrocarpum, is regarded as a mixed Gulf Stream/North Atlantic Drift—Labrador current association.     

Cyst formation,sedimentation, and preservation: Factors affecting dinoflagellate assemblages in recent sediments from trondheimsfjord,Norway

Plankton records and 25 samples of Recent sediment from Trondheimsfjord and the adjoining shelf were studied to investigate production, sedimentation, and preservation of cysts, as factors which influence the eventual composition of dinoflagellate cyst assembleges. All sediment samples were examined for dinoflagellate cysts using routine semiquantitative palynological procedures. In addition, fjord sediments were subjected to a limited sediment analysis, and, for three samples, results from preparations both with and without acid treatments were compared. For the first time, cyst assembleges from Recent sediments were directly compared with extensive plankton records from overlying waters. Results indicate that approximately 20% of the 55 locally recorded dinoflagellate species contribute cysts to bottom sediments. Once formed, cysts behave as fine silt particles in the sedimentary regime, increasing in abundance as the percentage abundance of finer sediment increases, usually with increased water depth. Cyst-forming species are almost entirely restricted to a few genera, particularly Gonyaulax and Peridinium, within the order Peridiniales. For some groups, reasonably good correspondence was found between percentage abundances of dinoflagellates in plankton and their cysts in sediment, though plankton records covering at least five years were required to establish this. Gonyaulax grindleyi Reinecke (Von Stosch 1969) appeared to be consistently overrepresented by cysts in sediment relative to available plankton evidence; possible explanations are suggested. At least 30% of the cyst species present, including most Peridinium species, were eliminated, or rendered unreliable for semiquantitative palynology, by application of routine palynological preparation treatments. Such cysts may provide useful, non-quantitative, palynological information from Recent and possibly Quaternary sediments, but their persistence would seem unlikely. Thus, factors of preservation probably further restrict the dinoflagellate fossil record. Cyst assemblages from Trondheimsfjord are comparable with those previously recorded from the northeastern coast of U.S.A., and from Scotland and northeastern England. Fjord assemblages are dominated by small, simple, spinose cysts which would be regarded as acritarchs if culture experiments had not proved that they are dinoflagellate cysts. Much potential biogeographic and palaeoenvironmental information was included within the less abundant species.Attention is drawn to the role which future culture experiments may be expected to play in helping to resolve taxonomic difficulties currently affecting dinoflagellate studies. Palynological significance of results from the present study is discussed especially with reference to recent work by Von Stosch which strongly suggests that cysts may be hypnozygotes formed routinely in sexual cycles of dinoflagellates.     

Preservation of organic-walled dinoflagellate cysts in different oxygen regimes: a 10,000 year natural experiment

The occurrence of organic-walled dinoflagellate cysts in (fossil) sediments depends on several factors, including as the ecological preferences of the cyst-forming dinoflagellates, cyst production, transport and preservation. Although laboratory experiments have shown that several cyst species are sensitive to chemical treatment, no information about the selective preservation of dinoflagellate cyst species in natural environments has previously been presented. Here, we present data on the effects of oxygen availability in bottom sediments on a cyst assemblage from the ungraded Madeira Abyssal Plain f-turbidite of which only the upper layer has been oxidized. Based on differences in species composition between the oxidized and underlying, unoxidized layers of this turbidite, the influence of oxygen availability on the preservation of individual species has been estimated. Cyst species have been classified in ascending order of resistance to oxygen availability in sediments as: (1) highly sensitive (cysts formed by Protoperidinium species), (2) moderately sensitive (e.g. Spiniferites species), (3) moderately resistant (e.g. Impagidinium paradoxum and Nematosphaeropsis labyrinthus) and (4) resistant (e.g. Impagidinium aculeatum).     

Description, host-specificity, and strain selectivity of the dinoflagellate parasite Parvilucifera sinerae sp. nov. (Perkinsozoa)

A new species of parasite, Parvilucifera sinerae sp. nov., isolated from a bloom of the toxic dinoflagellate Alexandrium minutum in the harbor of Arenys de Mar (Mediterranean Sea, Spain), is described. This species is morphologically, behaviourally, and genetically (18S rDNA sequence) different from Parvilucifera infectans, until now the only species of the genus Parvilucifera to be genetically analyzed. Sequence analysis of the 18S ribosomal DNA supported P. sinerae as a new species placed within the Perkinsozoa and close to P. infectans. Data on the seasonal occurrence of P. sinerae, its infective rates in natural and laboratory cultures, and intra-species strain-specific resistance are presented. Life-cycle studies in field samples showed that the dinoflagellate resting zygote (resting cyst) was resistant to infection, but the mobile zygote (planozygote) or pellicle stage (temporary cyst) became infected. The effects of light and salinity levels on the growth of P. sinerae were examined, and the results showed that low salinity levels promote both sporangial germination and higher rates of infection. Our findings on this newly described parasite point to a complex host-parasite interaction and provide valuable information that leads to a reconsideration of the biological strategy to control dinoflagellate blooms by means of intentional parasitic infections.     

Impact of grazing and bioturbation of marine benthic deposit feeders on dinoflagellate cysts

The impact of benthic deposit feeders on marine dinoflagellate cysts was studied by adding a concentrated natural Swedish cyst assemblage to sediment with different deposit feeders in replicate 4-l aquaria. The deposit feeders used were the bivalve Abra nitida, the echinoderm Amphiura filiformis, and the polychaetes Melinna cristata and Nereis diversicolor. These species occur naturally near the Swedish west coast and were selected to represent different ways of feeding. The results showed a significant relative decrease of unfossilizable cyst species; whereas, the common fossilizable species Lingulodinium polyedrum significantly increased in the cyst assemblage after grazing. This work suggests that differences in dinoflagellate cyst compositions can in part be caused by different animal grazing behaviors.     

The Early Jurassic palynostratigraphy of the Lusitanian Basin,western Portugal

A comprehensive investigation of the Early Jurassic stratigraphical palynology of the Lusitanian Basin in western Portugal was undertaken, with most emphasis placed on dinoflagellate cysts. A total of 214 samples from an upper Sinemurian to upper Toarcian composite section based on six successions were examined. The Sinemurian material examined was barren of dinoflagellate cysts; however, the Pliensbachian and Toarcian successions are characterised by relatively low diversities where Luehndea spinosa, Mancodinium semitabulatum, Mendicodinium microscabratum, Nannoceratopsis gracilis, Nannoceratopsis senex, and Scriniocassis priscus are relatively common and biostratigraphically significant. Luehndea spinosa dominates the lowermost Toarcian (Dactylioceras polymorphum ammonite Biozone), and is an index species. At the base of the Hildaites levisoni ammonite Biozone, the effects of the Toarcian Oceanic Anoxic Event (T-OAE) caused Luehndea spinosa to become extinct. At the same time, dinoflagellate cyst abundance and diversity markedly decreased. After the T-OAE, during the middle and late Toarcian, phytoplankton recovery was prolonged and slow in the Lusitanian Basin. The Luehndea spinosa and Mendicodinium microscabratum dinoflagellate cyst biozones are defined, both of which are subdivided into two dinoflagellate cyst subbiozones.     

2006年冬季长江口海域表层沉积物中甲藻孢囊的分类学研究

于2006年12月23日至2007年2月3日,采集长江口海域(121° ～127°E, 30°～32.5°N)19个站位0～10cm的底泥样品,根据孢囊的形态特征共鉴定出分属5大类的27种甲藻孢囊类型.其中自养型孢囊10种,异养型孢囊17种,9种为国内首次报道,它们是Scrippsiella sp.、Scrippsiella crystallina、Pentapharsodinium tyrrhenicum、Scrippsiella sp.1、Scrippsiella sp.2、Cochlodinium sp.cf.Geminatum、 P.sp.1、P.sp.2 和Gotoius abei,并发现了Alexandrium tamarense/A.catenella complex、 A.minutum/A.affine complex两种有毒种,Polykrikos kofoidii、Gonyaulax spinifera complex (Spiniferites mirabilis*)和Gonyaulax spinifera complex (Spiniferites cf.ramosus*)3种有害种.各站位孢囊物种数在1～15种之间,M4-13和N11-4最低,O7-6最高,且种类组成上基本以异养型甲藻孢囊为主.在长江口、苏北、杭州湾、舟山海域、外海海域分别鉴定出15、15、12、15、13种甲藻孢囊类型.对每种孢囊的分类学特征和分布情况进行了详细的描述,丰富了长江口海域甲藻孢囊种类记录,对研究该海区的甲藻群落结构及其目标赤潮生物的种群动力学具有重要意义.     

Seasonal distribution of dinoflagellate resting cysts in surface sediments from Changjiang River Estuary

In order to understand the distribution of dinoflagellate cysts, surface sediments were collected from 15 stations in Changjiang River Estuary from 122°E to 123.5°E and from 29°N to 32°N in four cruises from May 2002 to February 2003. In the present study, 38 different cyst morphotypes representing 21 genera and 6 groups were identified, while 1 type was not identified into genus level. Species number and cell density of dinoflagellate cysts ranged from 10 to 25 species and from 12 to 587 per gram of dry weight, respectively. There were no obvious differences in cyst composition and density among seasons. However, the highest cyst species number and density were recorded in summer and winter, respectively. Cysts of heterotrophic dinoflagellates, which held 55.7% of the overall cyst density averagely, dominated cyst assemblages. Cyst density and species number increased from the west to the east, from the north to the south within the study area. Cysts of toxic dinoflagellates Alexandrium cat‐enella and Alexandrium tamarense complex distributed widely and were observed in almost all stations, with the maximum cell density of 81 per gram of dry weight.     

Protoperidinium tricingulatum sp. nov. (Dinophyceae), a new motile form of a round,brown, and spiny dinoflagellate cyst

A small, broadly ovoidal and heterotrophic dinoflagellate containing round, brownish, and spiny cyst was found in the water column of Huibertsplaat in the Wadden Sea off the coast of the Netherlands. This dinoflagellate had these conspicuous morphological characters: a five‐sided first apical plate (1′), only three cingular plates, and an extremely small first antapical plate. Based on these morphological features, Protoperidinium tricingulatum Kawami, vanWezel, Koeman et Matsuoka is described as a new species. The flagellar pore of P. tricingulatum is covered with a small fin, which rises from the left side of the right sulcal plate to the large V‐shaped posterior sulcal plate. This feature suggests that P. tricingulatum is assigned to the Abé's Monovela Group. The cyst stage of P. tricingulatum was positively linked to the vegetative stage by comparison of the ribosomal 5.8S rDNA, internal transcribed spacers (ITS1 and ITS2). Living cysts of P. tricingulatum are round, brownish, and covered with many slender spines bearing capitate or cauliforate distal ends. The cyst also possesses a theropylic archeopyle formed by a slit corresponding to parasutures between three apical and two apical intercaraly plates. These morphological characters indicate that this species is morphologically related to two dinoflagellate cyst‐genera Islandinium and Echinidinium.     

Biodiversity and Association of Dinoflagellates in Coral Reef Rubble,Carrie Bow Cay,Belize

The species diversity and distribution of benthic dinoflagellates are illustrated from the back reef sand habitats at Carrie Bow Cay. Sand appears an ideal environment for nurturing a variety of species. Sand supported blooms of toxic, nontoxic, and parasitic assemblages of dinoflagellates. Morphology of dinoflagellates is illustrated in SEM and LM pictures; including the life cycle of a parasitic dinoflagellate's vegetative stage, sporogenetic stages, and the morphology of the feeding organelle. The feeding organelle of the primary dinoflagellate cysts is a hold fast and a peduncle‐like infestation tube, a ‘sucker organelle’, that inserts itself into copepod eggs. The parasitic dinoflagellate continues feeding on crustacean eggs since it is the only food source during vegetative cell division within the cyst. This is the first observation of the presence of parasitic dinoflagellates in shallow coral reef water. The study attempts to provide new knowledge on dinoflagellate associations and morphology of sand‐welling species in the microscopic food web of shallow warm tropical waters. Even, sand‐inhabiting invertebrates are not exempt from parasitic dinoflagellates.     

Temporal changes in the cyst densities of Pyrodinium bahamense var. compressum and other dinoflagellates in Manila Bay, Philippines

Temporal variation in the type and abundance of dinoflagellate cysts in Manila Bay, Philippines, is established using ²¹⁰Pb-dated sediment cores. At least 17 dinoflagellate cyst species, including those of the toxic species, Pyrodinium bahamense var. compressum, were identified. P. bahamense may have been present in the area since at least the 1920s. Total cyst density has increased beginning about 1988 to 1998 coinciding with records of P. bahamense blooms in the area. Heterotrophs have always dominated the cysts assemblage. These changes in the dinoflagellate record and the P. bahamense blooms in recent years may have been induced by the interplay of warmer temperatures, high rainfall leading to higher river discharge and less turbulent waters due to passage of few tropical cyclones.