Abundance Of Cryptophytes Research Articles

High-frequency monitoring reveals phytoplankton succession patterns and the role of cryptophyte in a subtropical river reservoir

Shifts in phytoplankton biodiversity drive frequent community successions within aquatic ecosystems. While significant progress has been made in understanding the factors influencing phytoplankton growth under controlled conditions, the processes driving phytoplankton succession in natural waters remain poorly understood. To address this gap, we conducted high-frequency monitoring of the phytoplankton community in the Jiangdong River Reservoir (Southeast China) from 2021 to 2022. High-frequency data captured 17 complete cycles of phytoplankton growth and decline. Our analysis showed that cryptophytes, though not the dominant group, played a key role in shaping the temporal dynamics of phytoplankton community structure and abundance. The relative abundance of cryptophytes consistently mirrored fluctuations in total chlorophyll-a concentrations. Rainfall-induced low-light conditions enhanced the competitive advantage of cryptophytes. Throughout each cycle of phytoplankton changes, cryptophytes leveraged this short-term advantage to proliferate by utilizing available ammonia nitrogen, ascending from the fourth to the second most abundant group. However, as ammonia nitrogen levels declined to 0.1 mg/L, cryptophyte populations began to decline. These new findings highlight the critical role of cryptophytes in driving phytoplankton succession patterns.

Time-series metagenomics reveals changing protistan ecology of a temperate dimictic lake

BackgroundProtists, single-celled eukaryotic organisms, are critical to food web ecology, contributing to primary productivity and connecting small bacteria and archaea to higher trophic levels. Lake Mendota is a large, eutrophic natural lake that is a Long-Term Ecological Research site and among the world’s best-studied freshwater systems. Metagenomic samples have been collected and shotgun sequenced from Lake Mendota for the last 20 years. Here, we analyze this comprehensive time series to infer changes to the structure and function of the protistan community and to hypothesize about their interactions with bacteria.ResultsBased on small subunit rRNA genes extracted from the metagenomes and metagenome-assembled genomes of microeukaryotes, we identify shifts in the eukaryotic phytoplankton community over time, which we predict to be a consequence of reduced zooplankton grazing pressures after the invasion of a invasive predator (the spiny water flea) to the lake. The metagenomic data also reveal the presence of the spiny water flea and the zebra mussel, a second invasive species to Lake Mendota, prior to their visual identification during routine monitoring. Furthermore, we use species co-occurrence and co-abundance analysis to connect the protistan community with bacterial taxa. Correlation analysis suggests that protists and bacteria may interact or respond similarly to environmental conditions. Cryptophytes declined in the second decade of the timeseries, while many alveolate groups (e.g., ciliates and dinoflagellates) and diatoms increased in abundance, changes that have implications for food web efficiency in Lake Mendota.ConclusionsWe demonstrate that metagenomic sequence-based community analysis can complement existing efforts to monitor protists in Lake Mendota based on microscopy-based count surveys. We observed patterns of seasonal abundance in microeukaryotes in Lake Mendota that corroborated expectations from other systems, including high abundance of cryptophytes in winter and diatoms in fall and spring, but with much higher resolution than previous surveys. Our study identified long-term changes in the abundance of eukaryotic microbes and provided context for the known establishment of an invasive species that catalyzes a trophic cascade involving protists. Our findings are important for decoding potential long-term consequences of human interventions, including invasive species introduction.BaNPxYigHXA7H5uqkH8sryVideo

Temporal and spatial diversity and abundance of cryptophytes in San Diego coastal waters.

Cryptophytes (class Cryptophyceae) are bi-flagellated eukaryotic protists with mixed nutritional modes and cosmopolitan distribution in aquatic environments. Despite their ubiquitous presence, their molecular diversity is understudied in coastal waters. Weekly 18S rRNA gene amplicon sequencing at the Scripps Institution of Oceanography pier (La Jolla, California) in 2016 revealed 16 unique cryptophyte amplicon sequence variants (ASVs), with two dominant "clade 4" ASVs. The diversity of cryptophytes was lower than what is often seen in other phytoplankton taxa. One ASV represented a known Synechococcus grazer, while the other one appeared not to have cultured representatives and an unknown potential for mixotrophy. These two dominant ASVs were negatively correlated, suggesting possible niche differentiation. The cryptophyte population in nearby San Diego Bay was surveyed in 2019 and showed the increasing dominance of a different clade 4 ASV toward the back of the bay where conditions are warmer, saltier, and shallower relative to other areas in the bay. An ASV representing a potentially chromatically acclimating cryptophyte species also suggested that San Diego Bay exerts differing ecological selection pressures than nearby coastal waters. Cryptophyte and Synechococcus cell abundance at the SIO Pier from 2011 to 2017 showed that cryptophytes were consistently present and had a significant correlation with Synechococcus abundance, but no detectable seasonality. The demonstrated mixotrophy of some cryptophytes suggests that grazing on these and perhaps other bacteria is important for their ecological success. Using several assumptions, we calculated that cryptophytes could consume up to 44% (average 6%) of the Synechococcus population per day. This implies that cryptophytes could significantly influence Synechococcus abundance.

Water Quality Improvement Shifts the Dominant Phytoplankton Group From Cryptophytes to Diatoms in a Coastal Ecosystem

We investigated long-term variations in the dominant phytoplankton groups with improvements in water quality over 11 years in the Yeongil Bay on the southeastern coast of Korea. River discharge declined during the study period but TN from river discharge remained stable, indicating the input of enriched nutrients to the bay was fairly consistent. NH4+ levels decreased with a decrease in TN from the POSCO industrial complex. While the study region was characterized by the P-limited and deficient environment, cryptophytes dominated with the intensified P-limitations. The relative abundance of cryptophytes declined from 70% in 2010 to 10% in 2016, but that of diatoms increased from 70% in 2009 to 90% in 2016. Correlation analysis showed a positive correlation of cryptophytes with NH4+ and a negative correlation with photic depth. Generalized additive models also exhibited an increase in diatom dominance and a decrease in cryptophyte dominance with an increase in water quality, indicating that a decrease in NH4+ and increase in light favored the diatom growth but suppressed the cryptophyte growth. Thus, water quality improvements shift the dominant group in the coastal ecological niche from cryptophytes to diatoms.

Changes in the Community Structure of Under-Ice and Open-Water Microbiomes in Urban Lakes Exposed to Road Salts.

Salinization of freshwater is increasingly observed in regions where chloride de-icing salts are applied to the roads in winter, but little is known about the effects on microbial communities. In this study, we analyzed the planktonic microbiomes of four lakes that differed in degree of urbanization, eutrophication and salinization, from an oligotrophic reference lake with no surrounding roads, to a eutrophic, salinized lake receiving runoff from a highway. We tested the hypothesis that an influence of road salts would be superimposed on the effects of season and trophic status. We evaluated the microbial community structure by 16S rRNA sequencing for Bacteria, and by four methods for eukaryotes: 16S rRNA chloroplast analysis, 18S rRNA sequencing, photosynthetic pigment analysis and microscopy. Consistent with our hypothesis, chloride and total nitrogen concentrations were among the most important statistical factors explaining the differences in taxonomic composition. These factors were positively correlated with the abundance of cryptophytes, haptophytes, and cyanobacteria. Ice-cover was also a major structuring factor, with clear differences between the winter communities and those of the open-water period. Nitrifying and methane oxidizing bacteria were more abundant in winter, suggesting the importance of anaerobic sediment processes and release of reduced compounds into the ice-covered water columns. The four methods for eukaryotic analysis provided complementary information. The 18S rRNA observations were strongly influenced by the presence of ribosome-rich ciliates, but revealed a much higher degree of taxonomic richness and greater separation of lakes, seasonal changes and potential salinity effects than the other methods.

Seasonal variation in effects of urea and phosphorus on phytoplankton abundance and community composition in a hypereutrophic hardwater lake

Abstract Urea accounts for half of global agricultural fertiliser applications, yet little is known of its role in eutrophication of freshwater ecosystems, nor how it interacts with phosphorus (P) in regulating phytoplankton composition, especially during spring and autumn. To identify when and how urea and P inputs interact across the ice‐free period, we conducted seven monthly fertilisation experiments in 3,240‐L mesocosms from ice‐off to ice‐formation in a hypereutrophic lake. In addition, we ran bioassays with ammonium (NH4+) to compare the effects of urea with those of NH4+, the immediate product of chemical decomposition of urea. Analysis of water‐column chlorophyll a and biomarker pigments by high‐performance liquid chromatography revealed that addition of inorganic P alone (100 µg P L–1 week–1) had no significant impact on either algal abundance or community composition in hypereutrophic Wascana Lake. Instead, fertilisation with urea (4 mg N L−1 week–1) alone, or in concert with P, significantly (p < 0.05) increased algal abundance in spring and much of summer, but not prior to ice formation in October. In particular, urea amendment enhanced abundance of cryptophytes, chlorophytes, and non‐diazotrophic cyanobacteria during April and May, while fertilisation in summer and early autumn (September) increased only chlorophytes and non‐diazotrophic cyanobacteria. Comparison of urea mesocosms with NH4+ bioassays demonstrated that urea lacked the inherent toxicity of NH4+ in cool waters, but that both compounds stimulated production during summer experiments. This study showed that urea pollution can degrade water quality in P‐rich lakes across a variety of seasonal conditions, including spring, and underscores the importance of quantifying the timing and form of N inputs when managing P‐rich freshwaters.

Trophic environments influence size at metamorphosis and recruitment performance of Pacific oysters

Reproduction and recruitment of benthic invertebrates are influenced by the climate and by the ecological structure of marine ecosystems, along with local anthropogenic pressures such as eutrophication or oligotrophication. Using the Pacific oyster Crassostrea gigas as a biological model, we tested the hypothesis that the variability in prodissoconch II (PII) size (i.e. size at metamorphosis) depends on ecological functioning. Settlement and recruitment were assessed at 5 sampling sites on the French Mediterranean shellfish farmed Thau lagoon during the main summer recruitment events in 3 consecutive years (2012-2014). Hydrobiological and planktonic analyses were conducted at 3 sampling sites. Our results showed that recruitment was extremely heterogeneous, ranging from 0 to 260 +/- 27 SE ind. dm(-2) throughout the ecosystem and was linked with variability in PII size, which ranged from 180 to 296 mu m. The annual temporal pattern of PII sizes appeared to be controlled by temperature during the settlement period, whereas the spatial pattern depended on phytoplankton biomass and on the trophic functioning of the ecosystem. Smaller PII sizes were significantly correlated with the highest phytoplankton biomass, while larger PII sizes were positively correlated with mixotrophic cryptophyte abundance. We found an inverse relationship between PII size and survival after metamorphosis, showing that recruitment success was associated with smaller PII sizes. Regional climate conditions and local trophic functioning appear to be key factors in metamorphosis and consequently contribute to recruitment heterogeneity. Further studies should be performed in other ecosystems following an oligotrophication trajectory to generalize this result.

Food Web Responses to Artificial Mixing in a Small Boreal Lake

In order to simulate food web responses of small boreal lakes to changes in thermal stratification due to global warming, a 4 year whole-lake manipulation experiment was performed. Within that time, period lake mixing was intensified artificially during two successive summers. Complementary data from a nearby lake of similar size and basic water chemistry were used as a reference. Phytoplankton biomass and chlorophyll a did not respond to the greater mixing depth but an increase was observed in the proportional abundance of diatoms, and the proportional abundance of cryptophytes also increased immediately after the onset of mixing. Obligate anoxic green sulphur bacteria vanished at the onset of mixing but gradually recovered after re-establishment of hypolimnetic anoxic conditions. No major effect on crustacean zooplankton was found, but their diversity increased in the metalimnion. During the mixing, the density of rotifers declined but protozoan density increased in the hypolimnion. Littoral benthic invertebrate density increased during the mixing due to Ephemeroptera, Asellus aquaticus and Chironomidae, whereas the density of Chaoborus larvae declined during mixing and lower densities were still recorded one year after the treatment. No structural changes in fish community were found although gillnet catches increased after the onset of the study. The early growth of perch (Perca fluviatilis) increased compared to the years before the mixing and in comparison to the reference lake, suggesting improved food availability in the experimental lake. Although several food web responses to the greater mixing depth were found, their persistence and ecological significance were strongly dependent on the extent of the disturbance. To better understand the impacts of wind stress on small lakes, long term whole-lake experiments are needed.

Impacts of forestry planting on primary production in upland lakes from north‐west Ireland

Planted forests are increasing in many upland regions worldwide, but knowledge about their potential effects on algal communities of catchment lakes is relatively unknown. Here, the effects of afforestation were investigated using palaeolimnology at six upland lake sites in the north-west of Ireland subject to different extents of forest plantation cover (4-64% of catchment area). (210)Pb-dated sediment cores were analysed for carotenoid pigments from algae, stable isotopes of bulk carbon (δ(13)C) and nitrogen (δ(15)N), and C/N ratios. In lakes with >50% of their catchment area covered by plantations, there were two- to sixfold increases in pigments from cryptophytes (alloxanthin) and significant but lower increases (39-116%) in those from colonial cyanobacteria (canthaxanthin), but no response from biomarkers of total algal abundance (β-carotene). In contrast, lakes in catchments with <20% afforestation exhibited no consistent response to forestry practices, although all lakes exhibited fluctuations in pigments and geochemical variables due to peat cutting and upland grazing prior to forest plantation. Taken together, patterns suggest that increases in cyanobacteria and cryptophyte abundance reflect a combination of mineral and nutrient enrichment associated with forest fertilization and organic matter influx which may have facilitated growth of mixotrophic taxa. This study demonstrates that planted forests can alter the abundance and community structure of algae in upland humic lakes of Ireland and Northern Ireland, despite long histories of prior catchment disturbance.

The ciliate Mesodinium rubrum and its cryptophyte prey in Antarctic aquatic environments

For growth, the mixotrophic ciliate Mesodinium rubrum sequesters organelles from ingested prey. Feeding in the field is poorly known; however, isolates of an Antarctic M. rubrum strain are maintained in culture on a diet of Teleaulex/Plagioselmis/Geminigera-like cryptophytes, suggesting that cryptophyte presence may be an important factor controlling M. rubrum distribution and abundance in nature. We augmented field surveys with published findings to establish the distribution of both M. rubrum and a Geminigera-like cryptophyte in a range of East Antarctic aquatic environments. We also studied their overwinter abundances in Ace Lake to determine whether a predator–prey relationship existed between the two species in this natural enclosed ecosystem. The ciliate and the cryptophyte co-occurred in the majority of sites sampled which ranged widely in salinity (2.2–150 ‰) and temperature (−3.0–16 °C). We observed a cyclic relationship in species abundances in Ace Lake, implying population growth for M. rubrum responded to changed cryptophyte abundance. Mesodinium rubrum likely exerts top-down pressure on cryptophyte abundances in natural enclosed ecosystems especially under low-light winter conditions. The ciliate can be considered an apex predator in highly truncated food webs.

Cryptophyte bloom in a Mediterranean estuary: High abundance of &lt;em&gt;Plagioselmis&lt;/em&gt; cf. &lt;em&gt;prolonga&lt;/em&gt; in the Krka River estuary (eastern Adriatic Sea)

During the June 2010 survey of phytoplankton and physicochemical parameters in the Krka River estuary (eastern Adriatic Sea), a cryptophyte bloom was observed. High abundance of cryptophytes (maximum 7.9×106 cells l–1) and high concentrations of the class-specific biomarker pigment alloxanthine (maximum 2312 ng l–1) were detected in the surface layer and at the halocline in the lower reach of the estuary. Taxonomical analysis revealed that the blooming species was Plagioselmis cf. prolonga. Analysis of the environmental parameters in the estuary suggested that the bloom was supported by the slower river flow as well as the increased orthophosphate and ammonium concentrations. The first record of a cryptophyte bloom in the Krka River estuary may indicate that large-scale changes are taking place in the phytoplankton community. Such changes could have a major impact on the natural ecosystem dynamics and the mariculture production in the area.

Sublethal Effects of Crude Oil on the Community Structure of Estuarine Phytoplankton

While the ecological impacts of crude oil exposure have been widely studied, its sublethal effects on phytoplankton community structure in salt marsh estuaries have not been well documented. The purpose of this study was to simulate oil spill conditions using a microcosm design to examine short-term (2 day) changes in phytoplankton community composition and total biomass following exposure to crude oil obtained from the Deepwater Horizon oil spill and a mixture of Texas crude oils. Microcosm experiments were performed in situ in North Inlet Estuary near Georgetown, SC. A control and six replicated experimental treatments of crude oil additions at final concentrations of 10, 50, or 100 μl l−1 of either Deepwater Horizon spill oil or the Texas crude mixture were incubated under in situ conditions. Photopigments were analyzed using high-performance liquid chromatography and community composition was determined using ChemTax. Total phytoplankton biomass (as chl a) declined with increasing crude oil concentrations. Prasinophytes, the most abundant microalga in both experiments, showed no response to oil exposure in one experiment and a significant negative response in the other. Diatoms euglenophytes and chlorophytes appeared relatively resistant to oil contamination at the exposure levels used in this study, maintaining or increasing their relative abundance with increasing oil concentrations. Chlorophytes and cyanobacteria increased in relative abundance while cryptophyte abundance decreased with increasing oil concentrations. The results of these experiments suggest that low levels of crude oil exposure may reduce total biomass and alter phytoplankton community composition with possible cascade effects at higher trophic levels in salt marsh estuaries.

Temporal and spatial dynamics of Cryptophytes biomass in the north of Lake Taihu

The variation of the abundance of Cryptophytes was analyzed using monthly monitoring data during 2005-2009in large shallow eutrophic Lake Taihu in China.The environmental factors and variations in cyanobacterial biomass were analyzed to explain the spatial and temporal distribution of Cryptophytes at three stations in Lake Taihu(Zhushan Bay,Meiliang Bay and Gonghu Bay).The results showed that: The mean biomass of the Cryptophytes in Zhushan Bay(1.89mg/L) was much higher than that of Meiliang Bay(0.87mg/L) and Gonghu Bay(0.43mg/L);The average biomass of Cryptophytes in 2008-2009(2.12mg/L) was much higher than that in 2005-2007(0.28mg/L);Principally,Cryptophytes were most prevalent in Zhushan Bay which was marked by higher nutrient levels,higher organic matter and suspended solid concentrations.The succession of Cryptophytes was mainly affected by the grazing of zooplankton in Gonghu Bay.Furthermore,Cryptophytes and Cyanobacteria abundances were found to be inversely correlated,temporally,in Lake Taihu.Cyanobacteria seem able to reduce the biomass of Cryptophytes.

Melting sea ice for taxonomic analysis: a comparison of four melting procedures

The influence of four melting procedures on the taxonomic composition of the sea-ice algal community in Kobbefjord, south-west Greenland, was investigated in April 2008. Direct melting (at 4 and 20°C) was compared with melting in buffering seawater (with salinities of 10 and 30). The sea-ice algal community consisted of diatoms, cysts and several flagellate groups. Direct melting at 20°C differed significantly from one or more of the other melting procedures regarding the flagellate groups chrysophytes, chlorophytes, dinoflagellates and unidentified flagellates, whereas diatom, cyst and cryptophyte abundance was similar, regardless of the melting procedure. Apart from chrysophytes, the three other melting procedures (direct melting at 4°C and buffered in seawater with salinities of 10 and 30) were not statistically different. It is recommended that direct melting at 20°C is avoided, whereas the three slow melting procedures are all comparable. This will enable the future comparison of data from a wide geographic and historical range, thereby increasing our knowledge of sympagic algal communities.

Melting sea ice for taxonomic analysis: a comparison of four melting procedures

The influence of four melting procedures on the taxonomic composition of the sea-ice algal community in Kobbefjord, south-west Greenland, was investigated in April 2008. Direct melting (at 4 and 20°C) was compared with melting in buffering seawater (with salinities of 10 and 30). The sea-ice algal community consisted of diatoms, cysts and several flagellate groups. Direct melting at 20°C differed significantly from one or more of the other melting procedures regarding the flagellate groups chrysophytes, chlorophytes, dinoflagellates and unidentified flagellates, whereas diatom, cyst and cryptophyte abundance was similar, regardless of the melting procedure. Apart from chrysophytes, the three other melting procedures (direct melting at 4°C and buffered in seawater with salinities of 10 and 30) were not statistically different. It is recommended that direct melting at 20°C is avoided, whereas the three slow melting procedures are all comparable. This will enable the future comparison of data from a wide geographic and historical range, thereby increasing our knowledge of sympagic algal communities.

Appearance of Dinophysis fortii following blooms of certain cryptophyte species

We examined the possibility that dinoflagellates belonging to genus Dinophysis acquire plastids from certain species of cryptophytes. We measured the abundance of cryptophytes over a 3 yr period in Okkirai Bay, northern Japan by fluorescent in situ hybridization (FISH), using an oligonucleotide probe that specifically binds to the Dinophysis plastid small subunit ribosomal RNA. A high density of FISH-probed cryptophytes always occurred prior to peak occurrences of D. fortii, although the density of FISH-probed cryptophytes did not correlate well with the density of D. fortii. Although further investigation is needed, monitoring of these cryptophyte species may be useful for predicting Dinophysis growth and subsequent outbreaks of diarrhetic shellfish poisoning.

Short-timescale variability of picophytoplankton abundance and cellular parameters in surface waters of the Alboran Sea (western Mediterranean)

The Alboran Sea (western Mediterranean) is characterized by a well-defined hydrological structure, the Almeria (Spain)–Oran (Algeria) geostrophic front. During the Almofront-2 cruise (November 22, 1997 to January 18, 1998), high frequency sampling (Δt = 0.5 h) of autotrophic picoplankton in surface waters was performed for 17 days (December 24 to January 9) using an automatic sampler. Cell abundance and several cellular parameters were measured by flow cytometry (FCM): forward and right-angle light scatters (FALS, RALS), phycoerythrin (PE) and chlorophyll (Chl) fluorescence. Analysis of abundance of Prochlorococcus, Synechococcus and picoeukaryotes allowed the distinction of two major types of systems: mesotrophic conditions (with waters characterized by detectable nutrients) dominated by picoeukaryotes and more oligotrophic areas (with low to undetectable nutrient levels) dominated by Prochlorococcus and, to a lower extent, Synechococcus. Most of the cellular parameters exhibited a clear diel periodicity, suggesting that cell growth and division processes were tightly coupled to the daily light cycle despite strong gradients of temperature and salinity. Cell growth for both Synechococcus and picoeukaryotes began at dawn and stopped at dusk. In contrast, the increase of Prochlorococcus light scattering only began in late afternoon, a very unusual behaviour that was apparently associated with strong quenching of Prochlorococcus Chl fluorescence during the day. Our data also suggested Chl quenching in Synechococcus but not in picoeukaryotes. Fourier analysis established unambiguously the 24 h diel periodicity for all cellular parameters as well as for cryptophyte abundance, but not for the abundance of other phytoplankters. The burst of division for picophytoplanktonic cells, inferred from the timing of the decrease of light scatter, occurred at dusk for both Synechococcus and picoeukaryotes, and later at night for Prochlorococcus. The ratio between maximum and minimum scatter (RALSmax/min) was useful in assessing the physiological state of the different picoplankters: high values suggested that populations probably had high division rates, especially picoeukaryotes, suggesting a quasi-optimal physiological activity of the cells in all water types encountered during this cruise despite strong hydrological gradients. This study reveals that the growth rate of the populations may be very little in these ecosystems.

Predicting grazing mortality of an estuarine dinoflagellate, Pfiesteria piscicida

Grazing can prevent or substantially decrease net growth of phytoplankton populations if grazing coefficients are similar to or greater than growth coefficients of the phytoplankter. Poten- tial grazing by microzooplankton on small dinoflagellates ( 2 d -1 , indicating that microzooplankton grazing had the potential to regulate densities of non-toxic zoospores. Potential grazing was positively correlated with salinity, abundance of photosynthetic and heterotrophic dinoflagellates and with abundance of < 20 µm planktonic ciliates. Grazing on zoospores was negatively associated with abundance of cryptophytes. Approximately 26% of the variation in grazing coefficient could be predicted from salinity, whereas 67% of the variation could be predicted from abundance of cryptophytes, dinoflagellates and small ciliates. Net growth of non- toxic zoospore populations is most likely in low-salinity waters with abundant cryptophytes but with low concentrations of microzooplankton.

Short‐term effects of linear alkylbenzene sulfonate on freshwater plankton studied under field conditions

AbstractThe toxic effects of linear alkylbenzene sulfonate (LAS) on several planktonic freshwater organisms were studied over a 5‐d period using small in situ enclosures. The experimental setup, an unreplicated regression design, made it possible to calculate no effect concentrations (NEC), an environmental risk assessment. The NEC varied several orders of magnitude between the different groups of organisms, with ciliates and heterotrophic nanoflagellates being the most sensitive groups (NEC as low as 0.02 mg LAS/L). The high sensitivity of the protozoans makes their exclusion from most ecotoxicological studies questionable, and this must be reconsidered in the future. Most other planktonic organisms were only affected at concentrations higher than normally found in aquatic habitats. Exceptions to this general trend were the photosynthetic activity of the phytoplankton and cryptophyte abundance, which both were nearly as sensitive parameters as the protozoan abundance. The toxicity of LAS was generally higher in the present investigation, compared with the vast majority of laboratory‐derived results, indicating a limited relevance of the latter and the need for field experiments in order to determine impacts of xenobiotics in the aquatic environments.

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.