Spring Diatom Bloom Research Articles

Can intense storms affect sinking particle dynamics after the North Atlantic spring bloom?

AbstractThe sinking of large particles (i.e., marine snow) has long been recognized as a key pathway for efficient particulate organic carbon (POC) export to the ocean interior during the decline of spring diatom blooms. Recent work has suggested that particles smaller than marine snow can also substantially contribute to POC export. However, a detailed characterization of small and large sinking particles at the end of blooms is missing. Here, we separately collected suspended and small and large sinking particles using Marine Snow Catchers and assessed their biogeochemical composition after the North Atlantic spring bloom in May 2021. During the 3 weeks of sampling, when four intense storms (maximum wind speeds 37–50 kt) created high turbulent kinetic energy dissipation rates and deepened the mixed layer, we observed two distinct sedimentation events. At first, sinking particles were dominated by small (diameter < 0.1 mm), slowly sinking ( 18 m d−1), particles rich in silica that carried a moderate POC flux (< 6 mmol C m−2 d−1) to 500 m depth. Once the storms ceased, the volume of large (diameter > 0.1 mm), fast‐sinking (> 75 m d−1), carbon‐rich marine snow aggregates (not fecal pellets) increased exponentially and POC fluxes at 100 m depth were more than fourfold greater (30 ± 12 mmol C m−2 d−1) than those during the previous event. The aggregates consisted of a mixed post‐bloom plankton community. Our data suggest that the storms shaped the timing, type, and magnitude of POC flux at the end of this spring phytoplankton bloom.

Multi-year three-dimensional simulation of seasonal variation in phytoplankton species composition in a large shallow lake

Multi-year three-dimensional simulation of seasonal variation in phytoplankton species composition in a large shallow lake

Marine particle microbiomes during a spring diatom bloom contain active sulfate-reducing bacteria.

Phytoplankton blooms fuel marine food webs with labile dissolved carbon and also lead to the formation of particulate organic matter composed of living and dead algal cells. These particles contribute to carbon sequestration and are sites of intense algal-bacterial interactions, providing diverse niches for microbes to thrive. We analyzed 16S and 18S ribosomal RNA gene amplicon sequences obtained from 51 time points and metaproteomes from 3 time points during a spring phytoplankton bloom in a shallow location (6-10m depth) in the North Sea. Particulate fractions larger than 10µm diameter were collected at near daily intervals between early March and late May in 2018. Network analysis identified two major modules representing bacteria co-occurring with diatoms and with dinoflagellates, respectively. The diatom network module included known sulfate-reducing Desulfobacterota as well as potentially sulfur-oxidizing Ectothiorhodospiraceae. Metaproteome analyses confirmed presence of key enzymes involved in dissimilatory sulfate reduction, a process known to occur in sinking particles at greater depths and in sediments. Our results indicate the presence of sufficiently anoxic niches in the particle fraction of an active phytoplankton bloom to sustain sulfate reduction, and an important role of benthic-pelagic coupling for microbiomes in shallow environments. Our findings may have implications for the understanding of algal-bacterial interactions and carbon export during blooms in shallow-water coastal areas.

Cryptic bacterial pathogens of diatoms peak during senescence of a winter diatom bloom.

Diatoms are globally abundant microalgae that form extensive blooms in aquatic ecosystems. Certain bacteria behave antagonistically towards diatoms, killing or inhibiting their growth. Despite their crucial implications to diatom blooms and population health, knowledge of diatom antagonists in the environment is fundamentally lacking. We report systematic characterisation of the diversity and seasonal dynamics of bacterial antagonists of diatoms via plaque assay sampling in the Western English Channel (WEC), where diatoms frequently bloom. Unexpectedly, peaks in detection did not occur during characteristic spring diatom blooms, but coincided with a winter bloom of Coscinodiscus, suggesting that these bacteria likely influence distinct diatom host populations. We isolated multiple bacterial antagonists, spanning 4 classes and 10 bacterial orders. Notably, a diatom attaching Roseobacter Ponticoccus alexandrii was isolated multiple times, indicative of a persistent environmental presence. Moreover, many isolates had no prior reports of antagonistic activity towards diatoms. We verified diatom growth inhibitory effects of eight isolates. In all cases tested, these effects were activated by pre-exposure to diatom organic matter. Discovery of widespread 'cryptic' antagonistic activity indicates that bacterial pathogenicity towards diatoms is more prevalent than previously recognised. Finally, examination of the global biogeography of WEC antagonists revealed co-occurrence patterns with diatom host populations in marine waters globally.

The influence of biochemical parameters on primary production in the Gulf of Gdańsk region: A model study

The influence of biochemical parameters on primary production in the Gulf of Gdańsk region: A model study

Infection strategies of different chytrids in a diatom spring bloom

Abstract Diatom blooms are often accompanied by an increase in parasitic chytrids that kill the host cells, which they are infecting, and can contribute to the decline of the bloom. However, host specificity and range of these chytrids are currently poorly understood. Low host specificity would enable the parasites to opportunistically infect any diatom species, while specialisation on infecting specific high‐biomass species could result in high prevalence and rapid spread of infection. We investigated such host–parasite interactions by monitoring the diverse diatom spring bloom in lake Erken using amplicon sequencing. We also performed infection experiments with two different, newly isolated chytrid species and several diatom cultures from the bloom. Chytridiomycota displayed the highest relative abundance of all parasitic lineages and were probably physically attached to larger organisms. Since the chytrids reached maximum abundance shortly after a peak in diatom reads, they were probably infecting these important primary producers. Phylogenetic analyses of the isolated chytrid strains identified them as members of the classes Rhizophydiales and Lobulomycetales. The infection experiments revealed high host specificity in these two chytrids targeting different diatom species. The experimental results supported statistical analyses of the environmental sequencing data, which suggested the presence of two different infection strategies: the most abundant chytrid species were specialised on infecting dominant diatom genera (i.e. Stephanodiscus, Aulacoseira, Asterionella), while rarer chytid species infected a range of less abundant diatoms.

Seasonal plankton dynamics in Kongsfjorden during two years of contrasting environmental conditions

Seasonal plankton time-series data are presented from Kongsfjorden from two years with contrasting environmental conditions. Kongsfjorden (west coast of Spitsbergen – 79°N) integrates inputs from Atlantic and Arctic waters, and glacier run-off, and is thus a prime location to study impacts on ecosystem dynamics of key environmental drivers that are relevant across the Arctic. Despite extensive research in Kongsfjorden, seasonally-resolved data are scarce. From late April/early May to early September 2019 and 2020, we conducted pelagic sampling at a mid-fjord station at mostly weekly to bi-weekly resolution investigating the environmental drivers of phyto- and zooplankton community composition and phenology. During spring 2019, Atlantic water masses with temperatures > 1 °C were found throughout the upper 250 m of the water column, and little sea ice occurred in the fjord. Spring 2020, in turn, was characterized by the presence of local water masses with sub-zero temperatures and relatively extensive sea-ice cover. The most striking contrast between the two years was the difference in phytoplankton spring bloom composition. In 2019, the spring bloom was dominated by the colonial stage of the haptophyte Phaeocystis pouchetii and diatoms played a minor role, while the spring bloom in 2020 was dominated by diatoms of the genus Thalassiosira succeeded by P. pouchetii. Selective grazing by large copepods and water mass structure seem to have been the decisive factors explaining the marked difference in diatom spring bloom biomass between the years while similar spring abundances of P. pouchetii in both years indicated that this species was less impacted by those factors. Our data suggest that differences in spring bloom composition impacted trophic transfer and carbon export. Recruitment of the dominant copepods Calanus finmarchicus and C. glacialis, Cirripedia and euphausiid larvae as well as the export of carbon to the seabed was more efficient during the diatom-dominated compared to the P. pouchetii–dominated spring bloom. In summer, the plankton composition shifted towards a flagellate-dominated community characterized by mixo- and heterotrophic taxa adapted to a lower nutrient regime and strong top-down control by copepod grazers. However, residual silicic acid after the P. pouchetii–dominated spring bloom fueled a late summer diatom bloom in 2019.Our data provide a first glimpse into the environmental drivers of plankton phenology and underline that high-resolution monitoring over many annual cycles is required to resolve the ephemeral variations of plankton populations against the backdrop of climate change.

Molecular diet analysis enables detection of diatom and cyanobacteria DNA in the gut of Macoma balthica.

Detritivores are essential to nutrient cycling, but are often neglected in trophic networks, due to difficulties with determining their diet. DNA analysis of gut contents shows promise of trophic link discrimination, but many unknown factors limit its usefulness. For example, DNA can be rapidly broken down, especially by digestion processes, and DNA provides only a snapshot of the gut contents at a specific time. Few studies have been performed on the length of time that prey DNA can be detected in consumer guts, and none so far using benthic detritivores. Eutrophication, along with climate change, is altering the phytoplankton communities in aquatic ecosystems, on which benthic detritivores in aphotic soft sediments depend. Nutrient-poor cyanobacteria blooms are increasing in frequency, duration, and magnitude in many water bodies, while nutrient-rich diatom spring blooms are shrinking in duration and magnitude, creating potential changes in diet of benthic detritivores. We performed an experiment to identify the taxonomy and quantify the abundance of phytoplankton DNA fragments on bivalve gut contents, and how long these fragments can be detected after consumption in the Baltic Sea clam Macoma balthica. Two common species of phytoplankton (the cyanobacteria Nodularia spumigena or the diatom Skeletonema marinoi) were fed to M. balthica from two regions (from the northern and southern Stockholm archipelago). After removing the food source, M. balthica gut contents were sampled every 24 hours for seven days to determine the number of 23S rRNA phytoplankton DNA copies and when the phytoplankton DNA could no longer be detected by quantitative PCR. We found no differences in diatom 18S rRNA gene fragments of the clams by region, but the southern clams showed significantly more cyanobacteria 16S rRNA gene fragments in their guts than the northern clams. Interestingly, the cyanobacteria and diatom DNA fragments were still detectable by qPCR in the guts of M. balthica one week after removal from its food source. However, DNA metabarcoding of the 23S rRNA phytoplankton gene found in the clam guts showed that added food (i.e. N. spumigena and S. marinoi) did not make up a majority of the detected diet. Our results suggest that these detritivorous clams therefore do not react as quickly as previously thought to fresh organic matter inputs, with other phytoplankton than large diatoms and cyanobacteria constituting the majority of their diet. This experiment demonstrates the viability of using molecular methods to determine feeding of detritivores, but further studies investigating how prey DNA signals can change over time in benthic detritivores will be needed before this method can be widely applicable to both models of ecological functions and conservation policy.

Taxonomic and functional dynamics during chytrid epidemics in an aquatic ecosystem.

Fungal parasitism is common in plankton communities and plays a crucial role in the ecosystem by balancing nutrient cycling in the food web. Previous studies of aquatic ecosystems revealed that zoosporic chytrid epidemics represent an important driving factor in phytoplankton seasonal successions. In this study, host-parasite dynamics in Lake Pavin (France) were investigated during the spring diatom bloom while following chytrid epidemics using next generation sequencing (NGS). Metabarcoding analyses were applied to study changes in the eukaryotic microbial community throughout diatom bloom-chytrid epidemics. Relative read abundances of metabarcoding data revealed potential "beneficiaries" and "victims" during the studied period. Subsequently, metatranscriptomic analyses on samples before and during the chytrid epidemic unveiled the active part of the community and functional/metabolic dynamics in association with the progress of chytrid infection. Diatom functions involving lipases, transporters, histones, vacuolar systems, the proteasome, proteases and DNA/RNA polymerases were more abundant during the diatom bloom. Chytrid functions related to a parasitic lifestyle including invasion, colonization and stress tolerance were up-regulated during the chytrid epidemic. In addition, functions related to the degradation/metabolism of proteins, lipids and chitin were in higher proportion in the community during the epidemic event. Results of NGS and bioinformatics analyses offered a panorama of dynamic biodiversity and biological functioning of the community.

Seasonal variability in carbon:234thorium ratios of suspended and sinking particles in coastal Antarctic waters: Field data and modeling synthesis

Seasonal variability in carbon:234thorium ratios of suspended and sinking particles in coastal Antarctic waters: Field data and modeling synthesis

An overview of Prorocentrum donghaiense blooms in China: Species identification, occurrences, ecological consequences, and factors regulating prevalence

An overview of Prorocentrum donghaiense blooms in China: Species identification, occurrences, ecological consequences, and factors regulating prevalence

Primary productivity and phytoplankton community structure in surface waters of the western subarctic Pacific and the Bering Sea during summer with reference to bloom stages

Primary productivity and phytoplankton community structure in surface waters of the western subarctic Pacific and the Bering Sea during summer with reference to bloom stages

Impact of Shifting Subpolar Front on Phytoplankton Dynamics in the Western Margin of East/Japan Sea

A subpolar front (SPF) generated between the East Korea Warm Current (EKWC) and the North Korea Cold Current (NKCC) in the western margin of the East/Japan Sea has shifted northward in recent decades. This study investigated the biomass and composition of the phytoplankton assemblage in relation to hydrological and biogeochemical features in the shallow shelf and slope off the Korean coast from January to June in 2016 and 2017, to determine the mechanistic effects of SPF on spring–summer phytoplankton bloom dynamics. Monthly average depth-integrated chlorophylla(Chla) levels and the contribution of phytoplankton classes revealed bimodal diatom blooms in early spring and summer in the frontal zone. Canonical correspondence analysis showed that the distribution of high Chlawas associated with cold, low-salinity NKCC water in March 2016. No Chlapeak was observed in March 2017 when the warm saline EKWC water mass invaded. These results suggest that the NKCC intrusion acts as a forcing mechanism leading to enhanced phytoplankton biomass in the frontal zone. In contrast, positive correlations of Chlaconcentration with water density and nutrient concentrations suggest that summer blooms were fed by the subsurface chlorophyll maximum (SCM) driven by shoaling of the pycnocline and nitracline. Varying water-column stratification determined the thickness of the SCM layer, driving year-to-year variability in the magnitude of diatom blooms. These findings further suggest that seasonal/interannual variability in the timing of algal blooms affects regional trophodynamics and hence could be an important factor in explaining ecosystem changes in this region.

Scallop shells as geochemical archives of phytoplankton‐related ecological processes in a temperate coastal ecosystem

AbstractPhytoplankton dynamics in coastal ecosystems is increasingly altered by land‐based human activities. Yet, this global vision conceals major disparities, among sites and through time. As conventional monitoring time series are quite sparse and relatively short, biological records of environmental variability appear as relevant tools to gain insights into phytoplankton dynamics over larger temporal and spatial scales. Here, we present results of an interdisciplinary project dealing with chemical information archived in shells of Pecten maximus (Bivalvia; Pectinidae), known to form daily growth striae on its shell surface. Several individuals were collected in the Bay of Brest (France) in 2011 and 2012, and analyzed for the molybdenum and lithium concentrations in their soft tissues and the element‐to‐calcium ratios (Mo : Ca and Li : Ca) in their calcitic striae. All shells revealed high synchrony and reproducibility in their Mo : Ca and Li : Ca profiles, characterized with a major peak at the end of May and in mid‐June 2011, respectively. Detailed analysis of physical, chemical, and biological variables measured in seawater during an extensive 9‐month environmental survey enabled a meticulous description of phytoplankton dynamics in 2011 and its impact on shell geochemistry. Main findings strongly suggest that (1) the timing of Mo : Ca peaks reflects the occurrence of silicon limitation and diatom aggregation periods, (2) the height of these peaks relates to the amplitude of the first spring diatom bloom, and (3) Li : Ca serves as a proxy for the temporal dynamics of diatom biovolume and of biogenic silica recycling at the sediment–water interface.

The response of coastal macrobenthic food-web structure to seasonal and regional variability in organic matter properties

The response of coastal macrobenthic food-web structure to seasonal and regional variability in organic matter properties

Cold and wet: Diatoms dominate the phytoplankton community during a year of anomalous weather in a Great Lakes estuary

As sentinels of climate change and other anthropogenic forces, freshwater lakes are experiencing ecosystem disruptions at every level of the food web, beginning with the phytoplankton, a highly responsive group of organisms. Most studies regarding the effects of climate change on phytoplankton focus on a potential scenario in which temperatures continuously increase and droughts intersperse heavy precipitation events. Like much of the conterminous United States in 2019, the Muskegon River watershed (Michigan, USA) experienced record-breaking rainfall accompanied by unusually cool temperatures, affording an opportunity to explore how an alternate potential climate scenario may affect phytoplankton. We conducted biweekly sampling of environmental variables and phytoplankton in Muskegon Lake, a Great Lakes Area of Concern that connects to Lake Michigan. We compared environmental variables in 2019 to the previous eight years using long-term data from the Muskegon Lake Observatory buoy, and annual monitoring excursions provided historical phytoplankton data. Under cold and wet conditions, diatoms were the single dominant division throughout the entire growth season – an unprecedented scenario in Muskegon Lake. In 10 of the 13 biweekly sampling days in 2019, diatoms comprised over 75% of the phytoplankton community in the lake by count, indicating that the spring diatom bloom persisted through the fall. Additionally, phytoplankton seasonal succession and abundance patterns typically seen in this lake were absent. In a world experiencing reduced predictability, increased variability, and regional climate anomalies, studying periods of extreme weather events may offer insight into how natural systems will be affected and respond under future climate scenarios.

Phytoplankton Composition and Environmental Drivers in the Northern Strait of Georgia (Salish Sea), British Columbia, Canada

A 4-year (2015–2018) weekly to bi-weekly time series of phytoplankton biomass and composition derived from high-performance liquid chromatography (HPLC) phytoplankton pigments and Chemtax analysis is presented and used to investigate phytoplankton community dynamics at a station in the northern Strait of Georgia (NSoG). Through the time series, blooms were largely dominated by diatoms, which formed the bulk of annual biomass. Spring diatom bloom timing and magnitude varied widely and appears to have been driven by complex interactions of solar radiation, wind, stratification, and grazing. In turn, post-spring diatom blooms were mostly associated with nutrient renewal to the surface layer as suggested by redundancy analysis (RDA), which showed inverse relationships between diatoms and temperature and stratification. A single non-diatom bloom in July 2016, dominated by the silicoflagellate, Dictyocha sp., was the time series maximum biomass and occurred under warm, stratified conditions and a freshening of the surface layer: The Chemtax dictyochophyte group was positively linked to temperature and stratification through RDA. Outside of bloom conditions, diverse communities emerged with prasinophytes and cryptophytes showing persistent contributions and their highest biomass during summer. Uniquely, these groups often persisted through nutrient renewal and drawdown events typically associated with diatom blooms and suggestive of high grazing pressure and nutrient regeneration. The prevalence of these groups through diverse conditions likely precluded statistical links with environmental drivers. This time series is the first of its kind for the NSoG, creates a baseline for future analyses, and highlights the contributions by small species, particularly prasinophytes, to regional phytoplankton communities.

DNA metabarcoding reveals multiple co-occurring species in

Spring diatom blooms dominate the annual cycle of phytoplankton abundance in temperate freshwater systems. Many researchers have questioned whether severe blooms are attributable to a single species and warrant the identification of similar, concurrently occurring organisms. Here, we investigated spring diatom blooms in a temperate freshwater system (Yeongsan River, South Korea) that is thought to predominantly include the diatom Stephanodiscus hantzschii. Water samples were collected from four different sites during the blooms that occurred in March 2015. We analysed physicochemical and biological parameters and examined the species composition of the spring blooms using DNA metabarcoding via pyrosequencing. Our results revealed that several diatom species co-occurred during the blooms: Cyclotella sp. was the most frequently detected, followed by Cyclostephanos dubius and Discostella sp., whereas Stephanodiscus was only detected at two stations with low occurrence. These results suggest the coexistence of many diatoms during spring blooms in the Yeongsan River; however, Cyclotella sp. was responsible for the spring bloom attributed to S. hantzschii. DNA metabarcoding can be a useful tool for resolving species identities in spring diatom blooms in temperate freshwater systems. In addition, the co-occurrence of similar species should be considered when implementing efforts to monitor and control spring blooms.

Unravelling winter diatom blooms in temperate lakes using high frequency data and ecological modeling

Unravelling winter diatom blooms in temperate lakes using high frequency data and ecological modeling

The first Holocene varve chronology for the UK: Based on the integration of varve counting, radiocarbon dating and tephrostratigraphy from Diss Mere (UK)

The first Holocene varve chronology for the UK: Based on the integration of varve counting, radiocarbon dating and tephrostratigraphy from Diss Mere (UK)