Bloom-forming Dinoflagellate Research Articles

Inorganic carbon acquisition in red tide dinoflagellates

Carbon acquisition was investigated in three marine bloom-forming dinollagellates-Prorocentrum minimum, Heterocapsa triquetra and Ceratium lineatum. In vivo activities of extracellular and intracellular carbonic anhydrase (CA), photosynthetic O2 evolution, CO2 and HCO3- uptake rates were measured by membrane inlet mass spectrometry (MIMS) in cells acclimated to low pH (8.0) and high pH (8.5 or 9.1). A second approach used short-term 14C-disequilibrium incubations to estimate the carbon source utilized by the cells. All three species showed negligible extracellular CA (eCA) activity in cells acclimated to low pH and only slightly higher activity when acclimated to high pH. Intracellular CA (iCA) activity was present in all three species, but it increased only in P. minimum with increasing pH. Half-saturation concentrations (K1/2) for photosynthetic O2 evolution were low compared to ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) kinetics. Moreover, apparent affinities for inorganic carbon (Ci) increased with increasing pH in the acclimation, indicating the operation of an efficient CO2 concentration mechanism (CCM) in these dinoflagellates. Rates of CO2 uptake were comparably low and could not support the observed rates of photosynthesis. Consequently, rates of HCO3- uptake were high in the investigated species, contributing more than 80% of the photosynthetic carbon fixation. The affinity for HCO3- and maximum uptake rates increased under higher pH. The strong preference for HCO3- was also confirmed by the 14C-disequilibrium technique. Modes of carbon acquisition were consistent with the 13C-fractionation pattern observed and indicated a strong species-specific difference in leakage. These results suggest that photosynthesis in marine dinoflagellates is not limited by Ci even at high pH, which may occur during red tides in coastal waters.

Phytoplankton functional groups and harmful algae species in anthropogenically impacted waters of the NW Mediterranean Sea

Phytoplankton assemblages were analysed by multivariate analysis techniques in highly modified waterbodies (harbours) of the northwestern Mediterranean Sea over an annual cycle. The phytoplankton functional groups that characterise these anthropogenically impacted waters were identified and related to HAB events. Four functional groups can be distinguished from the analysis: (1) bloom-forming dinoflagellates, (2) winter diatoms, (3) summer-autumn diatoms, and (4) large dinoflagellates and elongated diatoms. The species that characterise these functional groups occurred at all sampling stations. Potentially harmful species are distributed through all the clusters. However, bloom-forming dinoflagellates occur particularly in large harbours and during summer months. The results indicate that: (1) functional groups indicate where and when there is a high risk of blooms, but they cannot determine the risk of a toxic or fish-killing event; and (2) large harbours in tideless seas must be considered as areas with a high risk of high-biomass bloom occurrences.

Strong small-scale temporal bacterial changes associated with the migrations of bloom-forming dinoflagellates

Bacterial abundances in nearshore Mediterranean planktonic environments tend to change seasonally by 10-fold. Strong daily changes in bacterial abundance, at least as large as seasonal range, occurred in the presence of large dinoflagellate populations performing daily vertical migrations. The daily variability of heterotrophic bacteria was associated with the daily migrations of a bloom of Alexandrium taylori in La Fosca Bay, and Gymnodinium impudicum in Barcelona harbor. Bacterial abundance in surface waters can change daily as much as from 1 × 10 6 to 5 × 10 6 with apparent net change rates of 0.24 h −1. We suggest that the migrating dinoflagellates create microstructures exploited by the bacteria, and that the large algal populations (>10 6 cells l −1) make this microstructure visible with conventional sampling protocols. We also show evidence of the link between dinoflagellate abundance and relative bacterial activity in these waters, as measured by the percentage of bacteria with high nucleic acid content.

Prorocentrum minimum (Pavillard) Schiller : A review of a harmful algal bloom species of growing worldwide importance

Prorocentrum minimum (Pavillard) Schiller, a common, neritic, bloom-forming dinoflagellate, is the cause of harmful blooms in many estuarine and coastal environments. Among harmful algal bloom species, P. minimum is important for the following reasons: it is widely distributed geographically in temperate and subtropical waters; it is potentially harmful to humans via shellfish poisoning; it has detrimental effects at both the organismal and environmental levels; blooms appear to be undergoing a geographical expansion over the past several decades; and, a relationship appears to exist between blooms of this species and increasing coastal eutrophication. Although shellfish toxicity with associated human impacts has been attributed to P. minimum blooms from a variety of coastal environments (Japan; France; Norway; Netherlands; New York, USA), only clones isolated from the Mediterranean coast of France, and shellfish exposed to P. minimum blooms in this area, have been shown to contain a water soluble neurotoxic component which killed mice. Detrimental ecosystem effects associated with blooms range from fish and zoobenthic mortalities to shellfish aquaculture mortalities, attributable to both indirect biomass effects (e.g., low dissolved oxygen) and toxic effects. P. minimum blooms generally occur under conditions of high temperatures and incident irradiances and low to moderate salinities in coastal and estuarine environments often characterized as eutrophic, although they have been found under widely varying salinities and temperatures if other factors are conducive for growth. The physiological flexibility of P. minimum in response to changing environmental parameters (e.g., light, temperature, salinity) as well as its ability to utilize both inorganic and organic nitrogen, phosphorus, and carbon nutrient sources, suggest that increasing blooms of this species are a response to increasing coastal eutrophication.

Relationship between biomass and enzymatic activity of a bloom-forming dinoflagellate (Dinophyceae) in southern Chile (41 S): a field approach

In a coastal area of southern Chile (41° S), the major ammonium assimilating enzyme glutamine synthetase (GS) was detected in a green dinoflagellate bloom during April 2003. High chlorophyll a concentrations (1000 μg L−1) attributable to Gymnodinium cf. chlorophorum in surface waters were associated with high and very low nitrate reductase activities. Coincident with the bloom, dissolved inorganic nitrogen concentrations were near the detection limit (NO3− + NH4+ <0.5 μM). Since GS correlates with the use of ammonium as an external nitrogen source, we suggest that GS activity seems to be a good indicator of ammonium utilization in a period dominated by a single dinoflagellate species.

Is the invasion of Prorocentrum minimum (Dinophyceae) related to the nitrogen enrichment of the Baltic Sea?

The abundance of the invasive, bloom-forming dinoflagellate Prorocentrum minimum (Pavillard) Schiller and triangular, oval, and oval-round cell shapes were examined relative to salinity, temperature, and nutrient concentrations at the selected sites in the Baltic Sea. Based on the multiple regression and multivariate statistical analysis, all cell shapes of P. minimum had highly similar distribution relative to these environmental parameters as well as chlorophyll-a, nitrite + nitrate, ammonium, total nitrogen, phosphate, total phosphorus, and silicate. The species was related positively to total nitrogen, and negatively to salinity, temperature, nitrite + nitrate, and silicate:total nitrogen ratio. The results suggest that P. minimum could well adapt to low salinity and temperature and occurred particularly in coastal waters, rich in total nitrogen relative to silicate or other inorganic nutrients. These results indicate that the recent invasion of P. minimum into the Baltic Sea could have been enhanced by the DON enrichment. The results also support the suggestion that P. minimum is one morphospecies with no distinct subtaxa.

Spatial and temporal patterns of phytoplankton composition in subtropical coastal lagoon, the Indian River Lagoon, Florida, USA

A 2 year study of the phytoplankton community was carried out in the Indian River Lagoon, USA. In terms of biovolume, the phytoplankton community was generally dominated by dinoflagellates, diatoms or cyanobacteria. Mean phytoplankton standing crops were highest in the most flow-restricted regions of the lagoon, which had the lowest mean salinity values and comparatively high total nitrogen:total phosphorus ratios. In this region, blooms of dinoflagellates were common in the first year of the study, which was characterized by an El Nino event that yielded exceptionally high rainfall levels and freshwater outflow. Picoplanktonic cyanobacteria blooms became more prominent in the second year of the study, which was characterized by below average rainfall conditions. In unrestricted flow regions of the lagoon, located near inlets to the Atlantic Ocean, diatoms were most often the dominant taxa. Regions of intermediate water turnover rates and high external loading of phosphorus had a prevalence of diatom blooms. However, the average phytoplankton standing crops in the latter regions did not reach the levels experienced in the flow-restricted parts of the lagoon. In terms of individual phytoplankton taxa, the most common bloom-forming diatoms in the Indian River Lagoon system included: Skeletonema costatum, Dactyliosolen fragilissimus, Skeletonema menzelii, Cerataulina pelagica, Odontella regia, Chaetoceros lorenzianus, Rhizosolenia setigera and Thalassionema nitzschioides. The major bloom-forming dinoflagellate species included: Pheopolykrikos hartmannii, Akashiwo sanguinea, Prorocentrum micans, the potentially toxic species Pyrodinium bahamense var. bahamense and Prorocentrum minimum. Several picoplanktonic cyanobacteria were also prominent members of the phytoplankton community, including Synechococcus elongates. The spatial and temporal patterns observed in some of these dominant species were attributable to patterns in key environmental variables, including salinity, temperature and nutrient concentrations.

Dynamics of Heterocapsa circularisquama (Dinophyceae) and its viruses in Ago Bay, Japan

To examine the relationship between the bloom-forming dinoflagellate Heterocapsa circularisquama and its infectious viruses, a field survey was conducted in Ago Bay, Japan, in 2001. A H. circularisquama bloom occurred in July. The bloom peaked in mid July and disintegrated within a few days at the end of July. The abundance of viruses infectious to H. circularisquama was high from the peak of the bloom and throughout the post-bloom period, but ceased by the end of August. At the peak of the bloom, 88% of the H. circularisquama cells in the population harbored small virus- like particles (VLPs). Based on transmission electron microscopic (TEM) observation, morphological resemblance between these VLPs and the single-stranded RNA (ssRNA) virus infecting H. circularis- quama (HcRNAV: H. circularisquama RNA virus) isolated from the bloom was noticeable. The fluc- tuation patterns of the viruses indicated that at least 2 distinct types of virus with different host speci- ficity spectra coexisted. A specific increase in viral abundance in the sediments was observed in the middle of the bloom, and these viruses were likely able to maintain their infectivity for at least 3 mo. The present study provides further evidence of the possible viral impacts on the biomass and clonal composition of algal populations in the natural environment, and offers support for the hypothesis that sediments are a reservoir of algal viruses.

Transcript levels of the eukaryotic translation initiation factor 5A gene peak at early G(1) phase of the cell cycle in the dinoflagellate Crypthecodinium cohnii.

A cDNA encoding a eukaryotic translation initiation factor 5A (eIF-5A) homolog in heterotrophic dinoflagellate Crypthecodinium cohnii (CceIF-5A) was isolated through random sequencing of a cDNA library. The predicted amino acid sequence possesses the 12 strictly conserved amino acids around lysine 52 (equivalent to lysine 50 or 51 in other eukaryotes). A single 1.2-kb band was detected in Northern blot analysis. In synchronized C. cohnii cells, the transcript level peaked at early G(1) and decreased dramatically on the entry to S phase. Although this has not been previously reported, studies of budding yeast (Saccharomyces cerevisiae) and certain mammalian cell types suggest a role for eIF-5A in the G(1)/S transition of the eukaryotic cell cycle. Phylogenetic trees constructed with 26 other published eIF-5A sequences suggest that CceIF-5A, while falling within the eukaryotic branches, forms a lineage separate from those of the plants, animals, and archaebacteria. The posttranslational modification of eIF-5A by a transfer of a 4-aminobutyl moiety from spermidine to conserved lysine 50 or 51, forming amino acid hypusine, is the only demonstrated specific function of polyamines in cell proliferation. It has been suggested that polyamines stimulate population growth of bloom-forming dinoflagellates in the sea. We demonstrate here putrescine-stimulated cell proliferation. Furthermore, ornithine decarboxylase inhibitor D-difluoromethylornithine and the specific hypusination inhibitor N-guanyl-1,7-diaminoheptane exhibited inhibitory effects in two species of dinoflagellates. The possible links of polyamines and saxitoxin synthesis to the arginine cycle are also discussed.

Effect of diel and interday variations in light on the cell division pattern and in situ growth rates of the bloom-forming dinoflagellate Heterocapsa triquetra

Heterocapsa triquetra is an important bloom-forming dinoflagellate found in estuaries and nearshore regions worldwide. In an initial time-intensive study, the shallow, tidally mixed Newport River estuary, North Carolina, USA, was sampled from a fixed point located in the middle of the estuary every 2 h for 2 wk during the development of an H. triquetra bloom. The objective of this study was to investigate how short-term, high-frequency changes in temperature, light and salinity affected diel and interday cell division patterns and in situ growth rates of H. triquetra. During this study, phytoplankton samples were preserved in buffered formaldehyde and mitotic indices determined by acridine orange staining. The diel division pattern showed a nocturnal maximum between 23:00 and 05:00 h with reduced division during the day, a pattern characteristic of most dinoflagellates. The relative proportion of binucleate cells present during the day was influenced by interday variations in total irradiance, increasing during 2 of the 3 periods when there were 3 or more consecutive high light days (>28 E m -2 d -1 ). Approximately 40 % of the overall variation in interday division rates could be accounted for by differences in daily irradiance. The interday light differences were largely due to well-developed atmospheric frontal systems that brought increased cloud cover to the study area at regular 3 to 4 d intervals. The initial study, however, was of insufficient length to determine if the transient day-to-day light limitation could significantly affect seasonal bloom formation. A second longer-term, spatially intensive study was therefore undertaken to assess the relative importance of the incident light levels and nutrient inputs in controlling H. triquetra bloom initiation. During the second study, the estuary was monitored for photosynthetically active radiation (PAR), salinity, temperature, inorganic nutrients and cell densities of H. triquetra at 9 locations every wk from 23 December 1997 to 27 March 1998. Maximal H. triquetra bloom formation occurred during a 2 wk period when daily incident light levels were at or near the annual low. This suggested that H. triquetra is well adapted for utilizing low light levels and that variation in in situ growth rates in response to daily changes in PAR had little effect on bloom development. Instead, bloom initiation began with inputs of nitrogen-rich water following a runoff event, indicating that nutrient inputs are much more important in controlling bloom development than is light.

Effects of parasitism on diel vertical migration, phototaxis/geotaxis, and swimming speed of the bloom-forming dinoflagellate Akashiwo sanguinea

Eukaryotic parasites are believed to play important roles in bloom dynamics of red-tide dinoflagellates; however, little is known about their impact on host behavior. To address this issue, we examined the influence of the parasitic dinoflagellate Amoebophrya sp. on diel vertical migration (DVM), phototaxis/geotaxis, and swimming speed of the bloom-forming dinoflagellate Akashiwo sanguinea. Uninfected A. sanguinea exhibited strong DVM, yielding subsurface aggregations during the day and evenly dispersed populations at night. DVM of parasitized A. sanguinea was compara- ble to that of uninfected host for much of the infection cycle; however, subsurface accumulations of host cells were dramatically reduced or eliminated as parasites matured. The absence of DVM in the latter part of the infection cycle appeared to be associated with changes in phototaxic response and swimming speed of parasitized cells. While uninfected A. sanguinea exhibited strong positive photo- taxis, hosts with late-stage infections exhibited strong negative phototaxis. By contrast, infected and uninfected A. sanguinea did not differ in geotaxis or sinking. Swimming speed of infected A. san- guinea decreased with parasite age, differing significantly from that of uninfected hosts 24 h after ini- tiation of infections. A. sanguinea with late-stage infections exhibited a 37.3% lower swimming speed than uninfected hosts. Results indicate that parasitism by Amoebophrya sp. disrupts 'internal' factors that control DVM in dinoflagellates. Data also suggest that modification of host behavior by para- sitism may contribute to vertical variations in phytoplankton species-composition and -abundance, particularly during epidemics when late-stage infections are prevalent.

Effect of diel and interday variations in light on the cell division pattern and in situ growth rates of the bloom-forming dinoflagellate Heterocapsa triquetra

Effect of diel and interday variations in light on the cell division pattern and in situ growth rates of the bloom-forming dinoflagellate Heterocapsa triquetra

Ciliate grazing on the parasite Amoebophrya sp. decreases infection of the red-tide dinoflagellate Akashiwo sanguinea

Parasitic dinoflagellates of the genus Amoebophrya commonly infect free-living dino- flagellates, some of which cause toxic or otherwise harmful red tides. These parasites prevent repro- duction of their hosts and kill infected cells on a time scale of days. Thus, epidemic outbreaks of Amoebophrya spp. are thought to facilitate the decline of red tides by causing mass mortality of host taxa. However, little is known about biotic and abiotic factors that regulate epidemic occurrence of Amoebophrya spp. in nature. We addressed the hypothesis that grazing by ciliate microzooplankton on the infective stage of Amoebophrya sp. can regulate parasite prevalence in the bloom-forming dinoflagellate Akashiwo sanguinea. In culture, the choreotrich ciliate Strobilidium sp. rapidly in- gested and digested infective dinospores of Amoebophrya sp. ex A. sanguinea. Laboratory experi- ments also showed that grazing by Strobilidium sp. could decrease infection of A. sanguinea by 70 to 80% relative to controls. Field experiments using plankton assemblages from Chesapeake Bay, USA, indicated that grazing by natural populations of ciliates may contribute to the regulation of parasitism in A. sanguinea. Thus, grazing by ciliates and other microzooplankton may indirectly influence the occurrence of red tides by limiting the spread of parasites like Amoebophrya sp.

Seasonal niche strategy of the bloom-forming dinoflagellate Heterocapsa triquetra

Heterocapsa triquetra is one of the most common bloom-forming dinoflagellates found in estuaries and near shore regions around the world. This work examined the environmental factors associated with 3 separate wintertime H. triquetra blooms in the shallow tidally mixed Newport River estuary, North Carolina, USA. During 2 of the blooms in 1982 and 1983, the estuary was sampled from a fixed, single location every hour for 14 d. During the third study, the estuary was sampled at 9 fixed locations over its entire length each week from late December 1997 through March 1998. This time period included the formation and decline of the H. triquetra bloom. Barometric pressure, precipitation, photosynthetically active radiation, salinity, temperature, nutrient concentrations, and chl a were mea- sured in each study. During the 1997-1998 study, pigments were analyzed using HPLC to characterize the phytoplankton assemblages and the dominant dinoflagellates in each sample were counted. The prevailing environmental conditions associated with the wintertime blooms were largely the result of atmospheric forcing. Low pressure systems moved through the study area at 3 to 4 d intervals and were accompanied by low ambient air temperatures and regular rainfall. Runoff following the rainfall events supplied inorganic nutrients critical for bloom initiation and development. It also created a mesohaline frontal zone in the middle portion of the estuary with salinity and hydrodynamic conditions favorable for H. triquetra growth. Here, the H. triquetra bloom reached its maximal development with chl a levels >100 µg l -1 and cell densities between 1 and 6 × 10 6 l -1 . As the H. triquetra bloom developed, nutrient in- puts from the river became insufficient to meet growth demand and H. triquetra began feeding mixo- trophically, supplementing its nutritional requirements and reducing competition from co-occurring dinoflagellates. Cloud cover associated with the low pressure systems transiently limited H. triquetra growth as did low temperatures. More importantly though, low temperatures limited micro- and macro- zooplankton populations to such an extent that grazing losses were minimal. Hence, in order to bloom, H. triquetra optimizes a suite of factors including low grazing pressure, increased nutrient inputs, alternative nutrient sources, and favorable salinity and hydrodynamic conditions, as well as the nega- tive factors of temperature-limited growth, short day lengths, and periods of transient light limitation.

Effects of two strains of the parasitic dinoflagellate Amoebophrya on growth, photosynthesis, light absorption, and quantum yield of bloom-forming dinoflagellates

Eukaryotic parasites are believed to play important roles in bloom dynamics of red-tide dinoflagellates; however, little is known about their impact on host physiology and behavior. To address those issues, we examined the influence of parasitic dinoflagelates, Amoebophrya spp., on growth, photosynthesis, light absorption, and quantum yield of the bloom-forming dinoflagellates Akashiwo sanguinea and Gymnodinium instriatum. Parasites of the 2 host species differed in their site of infection, developing in the nucleus of A. sanguinea but in the cytoplasm of G. instriatum, and had divergent effects on host photophysiology. Neither host species appeared competent to repro- duce once infected, as growth of fully infected populations was negligible and cell division of infected hosts was never observed. Uninfected populations of both host species exhibited strong diel period- icity in photosynthesis, with parasitized cultures showing distinctly different patterns. Infected A. sanguinea displayed little or no photosynthetic periodicity, whereas diel periodicity continued in par- asitized G. instriatum but was less pronounced than that of uninfected host. Chlorophyll a (chl a) con- tent of A. sanguinea declined steadily over the infection cycle, while per cell and per chl a photo- synthetic rates decreased sharply until 16 h and then stabilized at ~50 pgC cell -1 h -1 and ~1 mgC (mgchla) -1 h -1 , respectively. By comparison, chl a content of infected G. instriatum was comparable with that of uninfected cells, with photosynthetic performance remaining high (~80% of uninfected hosts) until very late in the infection cycle. Light absorption by hosts increased in the blue region and decreased in the red region of the spectrum during the infection cycle, consequently enhancing chl a- specific absorption coefficients relative to uninfected cells by as much as 22 to 56% for A. sanguinea and 59% for G. instriatum. Furthermore, parasitism lowered maximum quantum yields in photosyn- thesis of both hosts by a factor of ~2, particularly in late infection stages. The contrasting effects of intranuclear and intracytoplasmic strains of Amoebophrya on photosynthetic performances and photo- physiological properties of host cells suggest that these parasites may exert somewhat different influ- ences on primary production and microbial activities during epidemic outbreaks in natural systems.

Effects of cyst resuspension on germination and seeding of two bloom-forming dinoflagellates in the Baltic Sea

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 216:57-66 (2001) - doi:10.3354/meps216057 Effects of cyst resuspension on germination and seeding of two bloom-forming dinoflagellates in the Baltic Sea Anke Kremp* Department of Ecology and Systematics, Division of Hydrobiology, PO Box 17, 00014 University of Helsinki, Finland and Tvärminne Zoological Station, 10900 Hanko, Finland *E-mail: anke.kremp@helsinki.fi ABSTRACT: The implications of cyst resuspension on germination and subsequent seeding of the 2 spring-bloom dinoflagellates Scrippsiella hangoei (Schiller) Larsen and Peridiniella catenata (Levender) Balech from the Baltic Sea were investigated in a field study and laboratory experiments. Sedimentation of resuspended cysts was monitored by an automated sediment trap in 2 consecutive winters prior to and throughout the germination period off the SW coast of Finland. The effects of increased irradiances and water motion on germination and germling survival were tested by incubating cysts at different light levels and in turbulent water. Cyst fluxes of both species were low during the calm and cold winter of 1998/1999. In 1999/2000, heavy storms caused strong resuspension of S. hangoei cysts. Light significantly increased the germination frequency of S. hangoei cysts and supported germling survival and cell division. In P. catenata, the percentage of excystment was not significantly influenced by light and germination was successfully completed in both darkness and light. Subsequent growth of the species, however, required light, although maximum cell numbers were encountered at an irradiance as low as 10 µmol m-2 s-1. Small-scale turbulence reduced the germination frequency of S. hangoei but did not affect excystment in P. catenata. No negative effects on subsequent growth were detected. The favourable effects of light on germination and germling survival of S. hangoei emphasize that resuspension would be advantageous for the bloom initiation of this species. Cyst resuspension seems to be less important in P. catenata population dynamics, since germination can be successfully completed in darkness and the amount of cysts transported to the water surface is insignificant even with strong turbulent mixing. It is concluded that cyst resuspension may be advantageous for dinoflagellate bloom initiation, depending on its extent and timing and the specific germination requirements of the respective organism. KEY WORDS: Cysts · Dinoflagellates · Germination · Peridiniella · Resuspension · Scrippsiella turbulence Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 216. Online publication date: July 06, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.

Occurrence of UVA- and UVB-absorbing compounds in 152 species (206 strains) of marine microalgae

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 189:35-51 (1999) - doi:10.3354/meps189035 Occurrence of UVA- and UVB-absorbing compounds in 152 species (206 strains) of marine microalgae S. W. Jeffrey1,*, H. S. MacTavish1,2,3, W. C. Dunlap4, M. Vesk2, K. Groenewoud1,2 1CSIRO Division of Marine Research, GPO Box 1538, Hobart, Tasmania 7001, Australia 2Electron Microscope Unit, Sydney University, New South Wales 2006, Australia 3Department of Agricultural Science, University of Tasmania, Tasmania 7001, Australia 4Australian Institute of Marine Science, PMB 3, Townsville, Queensland, 4810, Australia *E-mail: s.w.jeffrey@marine.csiro.au ABSTRACT: Marine microalgae (152 species, 206 strains) from 12 classes were examined for the presence of UVA- and UVB-absorbing compounds. Cultures were grown under white fluorescent light without supplementary UVA or UVB radiation and were extracted after harvest in tetrahydrofuran:methanol (20:80, v/v). Ratios of UV absorbance (280 to 390 nm) to chlorophyll a (chl a) (665 nm) obtained by spectrophotometry ranged from 0.18 to 6.75. Three groups of species were distinguished: those with low UV:chl a ratios (0.18 to 0.9, diatoms, green algae, cyanophytes, euglenophytes, eustigmatophytes, rhodophytes, some dinoflagellates, some prymnesiophytes), those with intermediate ratios (0.9 to 1.4, chrysophytes, some prasinophytes, some prymnesiophytes) and those with very high ratios (1.4 to 6.75, surface bloom-forming dinoflagellates, cryptomonads, prymnesiophytes and raphidophytes). UV-absorbing pigments varied across species of the same algal class and strains of the same species. HPLC analysis of extracts of 5 species (1 diatom, 2 bloom-forming raphidophytes and 2 bloom-forming dinoflagellates) showed suites of mycosporine-like amino acids in 4 of them, which included mycosporine-glycine, asterina-330, shinorine, porphyra-334 and palythine. The dinoflagellate Gymnodinium catenatum also contained major quantities of unknown UV-absorbing compounds. KEY WORDS: Ultraviolet radiation · Microalgae · Dinoflagellates · Cryptomonads · Prymnesiophytes · Raphidophytes · Mycosporine-like amino acids · Bloom-forming species · Gymnodinium catenatum Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 189. Publication date: November 26, 1999 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1999 Inter-Research.

Use of Discriminant and Fourth-Derivative Analyses With High-resolution Absorption Spectra for Phytoplankton Research: Limitations at Varied Signal-to-Noise Ratio and Spectral Resolution

Future management efforts aimed at inhibiting harmful algal blooms will require extensive temporal and spatial monitoring of phytoplankton community composition. A cost-effective approach to delineating phytoplankton community composition may be through analysis of absorption spectra, measured in situ with instruments deployed on moorings or by remote sensing. Classification techniques relying on absorption spectra include discriminant and fourth-derivative analysis. We investigated how well these techniques performed theoretically at varied signal-to-noise ratio and spectral resolution representative of a new absorption and attenuation instrument called HiStar. Our findings suggest that discriminant analysis of absorption spectra is a highly useful technique for categorizing green algae, cyanobacteria, noxious bloom-forming dinoflagellates, diatoms, and other chrysophytes. For the purposes of discriminating dinoflagellates from the other algae groups, discriminant analysis worked well with either low- or high-resolution spectral data. The discriminant analysis technique was able to delineate a noxious bloom-forming dinoflagellate species, Prorocentrum minimum, at signal-to-noise ratios as low as ~17. The current noise level in the HiStar, however, is ~28-fold too high to allow correct classification of this dinoflagellate at concentrations where shellfisheries are closed. Improvements to the discriminant analysis (e.g., inclusion of scatter properties) or to the HiStar must be accomplished before this technique becomes useful for harmful algal bloom management applications. Fourth-derivative analysis of absorption spectra, also a useful classification technique and a possible approach to assess physiological state of some algae, required at least 4 nm spectral resolution for assessment of chlorophylls a and b. The spectral resolution of HiStar (3.3 nm) meets this requirement.

Fluorescence excitation spectra and light utilization in two red tide dinoflagellates

We compared the impact of structural changes in the light‐harvesting machinery of two bloom‐forming dinoflagellates (Prorocentrum minimum and Heterocapsa pygmaea) by quantifying photophysiological changes in order to define the alternative mechanisms of photoacclimation. There are species‐specific and photoacclimative differences in the abundance and composition of functional light‐harvesting complexes (including photosystem 1‐ and 2‐enriched bands) which are reflected in spectral changes in absorption, and photosystem 2 (PS2) fluorescence excitation spectra of whole cells, thylakoid micelles, and discrete photosynthetic pigment‐protein complexes. DCMU‐induced variations in fluorescence excitation spectra are evident in whole cells but not in isolated thylakoid micelles or functional chromoproteins; such variations indicate that intracellular self‐shading which causes variable fluorescence is eliminated in subcellular preparations. We developed a scaling procedure of PS2‐related in vivo fluorescence excitation spectra relative to Chl a‐specific absorption coefficients and used the chromoprotein differences to illustrate how the chromoprotein composition alters cellular fluorescence properties. We also examined the energy transfer efficiency of photosynthetic pigments and the photoprotective role and location of diadinoxanthin.

Mixotrophy in the dinoflagellate Prorocentrum minimum

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 152:1-12 (1997) - doi:10.3354/meps152001 Mixotrophy in the dinoflagellate Prorocentrum minimum Stoecker DK, Li A, Coats DW, Gustafson DE, Nannen MK Prorocentrum minimum (formerly also known as P. mariae-lebouriae) is a common bloom-forming, photosynthetic dinoflagellate in Chesapeake Bay, USA. It is also capable of ingesting other cells. In Chesapeake Bay, P. minimum usually co-occurs with cryptophytes. Ingested cryptophyte material is observable in the dinoflagellate under an epifluorescent microscope as orange-fluorescent inclusions (OFI). During April and May, the frequency of OFI was <=10% in both surface and pycnocline assemblages. In summer, up to 50% of the P.minimum contained OFI. The frequency of OFI was positively correlated with cryptophyte abundance, but OFI were not frequent in all populations of P. minimum when cryptophyte densities were high. On-deck experimental incubations were done to determine the conditions that influence feeding. Light level and inorganic nutrient availability over the previous 24 h affect feeding.Incidence of feeding is lower when populations are maintained in the dark for 24 h than on a natural light:dark cycle. Addition of nitrate and phosphate together can inhibit feeding. Ingestion has a diel pattern, with frequency of OFI highest in the afternoon and evening and lowest in the morning. Feeding is influenced by a complex of factors, but the spatial-temporal pattern of ingestion and the experiments both suggest that feeding is primarily a mechanism for obtaining limiting inorganic nutrients rather than a mechanism for supplementing carbon nutrition during light limitation. Ingestion of other protists, including competitors for light and nutrients, may be an important strategy which allows bloom-forming dinoflagellates to dominate plankton assemblages for extended periods and during changing nutrient regimes. Prorocentrum · Dinoflagellates · Cryptophytes · Mixotrophy · Chesapeake Bay Full text in pdf format NextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 152. Publication date: June 26, 1997 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1997 Inter-Research.