Marine Phytoplankton Diversity Research Articles

Fine-scale phytoplankton community transitions in the oligotrophic ocean: A Mediterranean Sea case study

The vast diversity of marine phytoplankton, shaped by intricate water dynamics, remains poorly understood in the oligotrophic ocean. In situ studies reveal fine-scale dynamics affecting phytoplankton distribution, leading to abrupt shifts in abundance and biomass referred here as “phytoplankton community transitions” (PCTs). Using a simple nutrient-phytoplankton-zooplankton (NPZ) numerical model, our study proposes a theoretical framework to explain PCTs observed during an oceanographic cruise in the Mediterranean Sea. We consider both a homogeneous and a variable environment, respectively corresponding to the waters on both sides of a front and to the frontal area itself. In the model, PCTs between one community of smaller phytoplankton and one community of bigger phytoplankton are controlled by nutrient supply, but not directly: nutrient supply affects all compartments of the model and creates PCTs by combining bottom-up and top-down controls. This mechanism is observed for both constant (i.e., within a water mass) and pulsed (i.e., in the front) nutrient supply. These results are consistent with in situ observations of biomass proportion across a front. This theoretical framework helps to better understand and plan in situ observations in oceanic regions characterized by fine-scale dynamics and oligotrophic conditions.

PETRI-MED: Enhancing marine phytoplankton diversity monitoring in the Mediterranean

PETRI-MED: Enhancing marine phytoplankton diversity monitoring in the Mediterranean Preserving biodiversity is crucial for sustaining life on Earth. Unfortunately, it is facing growing threats. Marco Talone and the PETRI-MED Team discuss their objectives for the PETRI-MED project and explain why it is urgently necessary. Marine biodiversity is crucial for maintaining healthy and resilient ecosystems. The variety of life forms in our oceans—from microscopic plankton to giant whales—plays a key role in sustaining ecological balance. Each species contributes to ecosystem services such as oxygen production, carbon sequestration, and nutrient cycling, which are vital for the planet’s health. Marine biodiversity also supports the global food web, providing a primary source of protein for over three billion people. Additionally, it contributes to the blue economy through fisheries, tourism, and biotechnology. Lastly, healthy marine ecosystems are better equipped to withstand and recover from environmental changes and human impacts, such as climate change and pollution. Among the various life forms inhabiting our ocean, phytoplankton is one of the most important.

Biogeochemical cycling of dissolved manganese in the Arabian Sea

The study of marine biogeochemical cycling of Mn, a bio-essential trace metal, is crucial to decipher its relative role in controlling the production and diversity of marine phytoplankton. Furthermore, Mn oxides and oxyhydroxides act as sinks for other trace elements in the water column, and Mn redox cycling may exert a major control on the vertical distribution of these elements. Dissolved Mn (dMn) concentrations are measured along two GEOTRACES-India (GI) transects, GI05 and GI10, for a basin-wide investigation of biogeochemical controls on the dMn distribution in the Arabian Sea (AS). Surface dMn distribution shows a strong spatial gradient, with relatively dMn-rich levels in the eastern AS (3.4–5.7 nmol kg−1) compared to the central and western AS (1.2–2.3 nmol kg−1). This correlates with the higher model estimates of soluble Mn input from the atmospheric dust deposition in the eastern AS (∼1.5–2.0 times of input in the western and central AS), and probable additional Mn input from riverine discharge and shallow shelf region of the eastern AS. In the south-eastern AS, a correlated increase in surface dMn with a decrease in salinity indicates the Mn input by the advection of dMn-rich, low-salinity Bay of Bengal (BoB) surface waters to the AS under the influence of the Northeast Monsoon Current. Our mass balance estimates for dMn in the euphotic waters (upper 100 m) suggest important contributions from atmospheric Mn deposition (14–99% of the total estimated input flux), and dMn input/dilution (13–74% of the total estimated input or removal flux) due to lateral/vertical advective-eddy diffusive mixing. Mn-oxidation and passive scavenging are determined to be the dominant processes for the dMn removal (61–99%) from the euphotic zone (upper 100 m), while export via Mn bio-assimilation is comparatively negligible.In the AS denitrification zone, the observed dMn maxima in the upper thermocline depths (∼200–400 m) result from the in situ reductive dissolution of Mn oxides and oxyhydroxides, and lateral advective-eddy diffusive Mn flux from the reducing sediments of the western Indian margin. Outside the denitrification zone, in the northern and western AS, a shift of dMn maxima to the lower thermocline waters (∼500 m) indicates the change in the source region and dMn input from the reducing margins of the north (Pakistan Margin) and north-western AS (Oman Margin), intersecting the core of the oxygen minima at the depth range of 400–600 m.Deep water (>1500 m) dMn concentrations are low (<0.3 nmol kg−1) in most of the AS regions. Anomalous dMn enrichment in the deep waters is observed in the southern and western AS, presumably indicating the influence of hydrothermal plumes emanating from the active hydrothermal vents over the Carlsberg Ridge and spreading ridges in the Gulf of Aden. A correlated and localized increase in dMn and dAl levels close to the Murray Ridge hints at dMn input from the sediment resuspension over the ridge and subsequent Mn dissolution in low-oxygen waters (DO < 20 µM) and/or diffusive flux from the Mn-rich pore waters.

Marine phytoplankton diversity of Odisha coast, India with special reference to new record of diatoms and dinoflagellates

Marine phytoplankton diversity of Odisha coast, India with special reference to new record of diatoms and dinoflagellates

Diversity and seasonal variation of marine phytoplankton in Jiaozhou Bay, China revealed by morphological observation and metabarcoding

Diversity and seasonal variation of marine phytoplankton in Jiaozhou Bay, China revealed by morphological observation and metabarcoding

Dimensions of marine phytoplankton diversity

Abstract. Biodiversity of phytoplankton is important for ecosystem stability and marine biogeochemistry. However, the large-scale patterns of diversity are not well understood and are often poorly characterized in terms of statistical relationships with factors such as latitude, temperature and productivity. Here we use ecological theory and a global trait-based ecosystem model to provide mechanistic understanding of patterns of phytoplankton diversity. Our study suggests that phytoplankton diversity across three dimensions of trait space (size, biogeochemical function and thermal tolerance) is controlled by disparate combinations of drivers: the supply rate of the limiting resource, the imbalance in different resource supplies relative to competing phytoplankton demands, size-selective grazing and transport by the moving ocean. Using sensitivity studies we show that each dimension of diversity is controlled by different drivers. Models including only one (or two) of the trait dimensions will have different patterns of diversity than one which incorporates another trait dimension. We use the results of our model exploration to infer the controls on the diversity patterns derived from field observations along meridional transects in the Atlantic and to explain why different taxa and size classes have differing patterns.

Metabolomic Insights into Marine Phytoplankton Diversity.

The democratization of sequencing technologies fostered a leap in our knowledge of the diversity of marine phytoplanktonic microalgae, revealing many previously unknown species and lineages. The evolutionary history of the diversification of microalgae can be inferred from the analysis of their genome sequences. However, the link between the DNA sequence and the associated phenotype is notoriously difficult to assess, all the more so for marine phytoplanktonic microalgae for which the lab culture and, thus, biological experimentation is very tedious. Here, we explore the potential of a high-throughput untargeted metabolomic approach to explore the phenotypic–genotypic gap in 12 marine microalgae encompassing 1.2 billion years of evolution. We identified species- and lineage-specific metabolites. We also provide evidence of a very good correlation between the molecular divergence, inferred from the DNA sequences, and the metabolomic divergence, inferred from the complete metabolomic profiles. These results provide novel insights into the potential of chemotaxonomy in marine phytoplankton and support the hypothesis of a metabolomic clock, suggesting that DNA and metabolomic profiles co-evolve.

The Characteristics and Distribution of Eukaryotic Phytoplankton Community in Liaodong Bay, China

Brown tides have occurred in the Bohai Sea of China since 2009 and caused serious losses in aquaculture. In recent years, phytoplankton identification has been greatly promoted by the development of high-throughput sequencing technologies. In this study, V4 region of 18S rDNA was used as the target gene to design the primer V4 (F/R), and high-throughput sequencing technology was adopted to evaluate the diversity of composition and characteristics of the eukaryotic phytoplankton community. A total of 93 alga species were identified, and about 60% (56 out of 93) of them were undetected or unreported in Chinese waters. There were 59% of the total algal species identified as autotrophy in trophic mode while heterotrophy and mixotrophy accounted for 12% and 29% of the total algal species, respectively. 8 species of picophytoplankton that were mainly distributed in the south and a partial area of the east and west formed the scientific basis for the quality and safety early-warning in aquatic products and brown rides study. Diversity index analysis also revealed a trend of fluctuations of marine phytoplankton diversity in different sample sites in Liaodong Bay. In conclusion, our work provides a detailed evaluation of eukaryotic phytoplankton diversity in Liaodong Bay, suggesting the need for long-term monitoring to further study and guard against the potential risk of harmful algal blooms.

Changes in marine phytoplankton diversity: Assessment under the Marine Strategy Framework Directive

The Marine Strategy Framework Directive requires EU Member States to assess the Good Environmental Status (GES) of their marine waters in a coherent and strategic manner. For the regional assessment of biodiversity, the OSPAR Intersessional Coordination Group of Biodiversity Assessment and Monitoring (ICG-COBAM) provides substantial advice. Through expert working groups, phytoplankton indicators are currently being developed to measure the state and the change in pelagic diversity, to quantify food web dynamics and to measure the extent of eutrophication impacts. We developed a multi-metric indicator that is compliant with the common OSPAR indicator “Changes in plankton diversity” (PH3). The aim was to describe the structure of the phytoplankton community (alpha diversity) and to detect significant temporal changes (beta diversity) to evaluate the health of pelagic habitats. In this pilot study, we used three coastal time-series in the Western Channel and the north of the Bay of Biscay (North Atlantic, France) to test the efficiency and the performance of several existing diversity indices. We validated two alpha diversity indices, namely the Menhinick Index (D) and the Hulburt Index (δ), based on their complementary ecological information, their strong relationship with habitat characteristics, and their relative ease of interpretation for stakeholders. Temporal shifts or rate of change in community structure were detected by the Local Contributions to Beta Diversity index (LCBD; a beta diversity measure). For the years where significantly high LCBD values were found, the Importance Value Index (IVI) was calculated to potentially identify the taxa (genus) responsible for the “unusual” community structure. For example, at the Ouest Loscolo site in 2008, an elevated LCBD (0.45) coincided with a high dominance value (Hulburt’s Index) caused by the occurrence of a monospecific bloom of Leptocylindrus spp. (IVI = 73%) in July (2.22 × 106 cells L−1) and October (8 × 106 cells L−1). In this way, PH3 informs on different aspects of phytoplankton diversity from a community to a genus level. At the current stage of development, however, PH3 acts as a “surveillance” rather than an operational indicator since the relationship to GES is not directly tracked. In the future, by additional testing of PH3 and extending the geographical scope, the robustness of the assessment could be further determined across the OSPAR Maritime Area.

Evidence of small‐scale spatial structuring of phytoplankton alpha‐ and beta‐diversity in the open ocean

SummaryPhytoplankton assemblages in the open ocean are usually assumed to be mixed on local scales unless large semi‐permanent density discontinuities separating water masses are present. Recent modelling studies have, however, suggested that ephemeral submesoscale oceanographic features leading to only subtle density discontinuities may be important for controlling phytoplankton alpha‐ and beta‐diversity patterns. Until now, no empirical evidence has been presented to support this hypothesis.Using hydrographic and taxonomic composition data collected near Iceland during the period of the 2008 spring bloom, we show that the distribution of phytoplankton alpha‐ and beta‐diversity was related to submesoscale heterogeneity in oceanographic conditions. Distinct phytoplankton communities as well as differences in richness were identified on either side of a front delimiting surface waters of slightly different (˜0.03) salinities.Alpha‐diversity was significantly higher on the high salinity side of the front compared to the low salinity side. This difference was primarily driven by the presence of several large diatom species in the high salinity region, especially of the genusChaetoceroswhich dominated the biomass here. By investigating beta‐diversity in relation to environmental and spatiotemporal variables, we show that the regional distribution of phytoplankton taxa was influenced by both different environmental conditions on either side of the front and dispersal limitation across the front. Changes in beta‐diversity were primarily driven by turnover rather than nestedness and were apparently controlled by different processes in each region.Synthesis. This study shows that small‐scale and ephemeral density discontinuities created by submesoscale frontal dynamics can play a major role in structuring patterns of phytoplankton diversity. Evidence is presented that they can generate changes in environmental conditions (leading to environmental filtering) and act as physical (dispersal) barriers for phytoplankton transport. The study suggests that dispersal barriers are potentially of much greater importance for phytoplankton diversity at local scales than currently recognized and indicates that drivers of marine phytoplankton diversity are similar to those structuring diversity of land plants.

Marine phytoplankton diversity and the impact of global climate change

Understanding the effect of global climate change (GCC) on earth ecosystems is a key issue worldwide. Compared to terrestrial ecosystems, marine ecosystems are more sensitive to GCC. Stresses that GCC brings to oceans include warming, ocean acidification, changes in currents, sea level rise, and enhancement of ultraviolet radiation, etc. Phytoplankton are the key primary producers in marine ecosystems and very important in the ocean carbon cycle. Distribution patterns, primary productivity, community succession and phenology of phytoplankton can all be affected by GCC. For phytoplankton species distribution, the distribution region of warm-water species is generally extended, which is opposite the trend of cold-water species. Phytoplankton primary productivity is decreased globally, and phytoplankton cell sizes are gradually reduced. Intensity and timing of phytoplankton blooms are stronger and earlier, with a higher frequency of harmful algal blooms. Ocean acidification has been found to greatly affect the metabolisms and biodiversity of marine organisms, especially calcifying species. Enhancement of ultraviolet radiation may inhibit the growth of phytoplankton. Furthermore, El Nino, La Nina and enhanced precipitation will decrease phytoplankton biomass. The changes in phytoplankton growth and distribution will lead to variation of its biodiversity from the gene to ecosystem levels. Phytoplankton eco-physiological studies under GCC driven factors and long-term monitoring •综述• 740 生 物 多 样 性 Biodiversity Science 第 24 卷 are key pathways for understanding the phytoplankton-diversity-ecosystem responses and feedbacks under GCC.

The dynamical landscape of marine phytoplankton diversity.

Observations suggest that the landscape of marine phytoplankton assemblage might be strongly heterogeneous at the dynamical mesoscale and submesoscale (10-100 km, days to months), with potential consequences in terms of global diversity and carbon export. But these variations are not well documented as synoptic taxonomic data are difficult to acquire. Here, we examine how phytoplankton assemblage and diversity vary between mesoscale eddies and submesoscale fronts. We use a multi-phytoplankton numerical model embedded in a mesoscale flow representative of the North Atlantic. Our model results suggest that the mesoscale flow dynamically distorts the niches predefined by environmental contrasts at the basin scale and that the phytoplankton diversity landscape varies over temporal and spatial scales that are one order of magnitude smaller than those of the basin-scale environmental conditions. We find that any assemblage and any level of diversity can occur in eddies and fronts. However, on a statistical level, the results suggest a tendency for larger diversity and more fast-growing types at fronts, where nutrient supplies are larger and where populations of adjacent water masses are constantly brought into contact; and lower diversity in the core of eddies, where water masses are kept isolated long enough to enable competitive exclusion.

Marine nano‐ and microphytoplankton diversity: redrawing global patterns from sampling‐standardized data

AbstractAimWe analysed marine phytoplankton diversity data as a function of latitude, temperature, primary production and several environmental and biological variables to ascertain whether large‐scale variability in the diversity of marine nano‐ and microphytoplankton (including diatoms, dinoflagellates and coccolithophores) follows similar patterns to those observed for macroorganisms. For the first time we explored these relationships after correcting the observed patterns of species richness by sampling effort.LocationThe global ocean.MethodsTo standardize the estimates of species richness by sampling effort we used interpolation and extrapolation based on Hill numbers and shareholder quorum subsampling (SQS) methods. Then, we fitted linear and quadratic models to species richness data to explore their variability with latitude, inverse temperature and biomass. These relationships were compared with the patterns obtained from non‐standardized data. In addition, we used a stepwise multiple linear regression model to explain the variability of species richness as the combined effect of multiple drivers acting together.ResultsMarine phytoplankton diversity was weakly correlated with latitude, temperature or biomass. The hotspots of species richness at intermediate latitudes largely vanished after standardization for sampling effort. Neither latitude, temperature, primary production (as diagnostics of energy supply) nor any other variable or combination of variables, explained the patterns of phytoplankton species richness.Main conclusionsNone of the hypotheses tested explained a significant amount of the variability in species richness. The patterns observed for microorganisms in previous studies may have resulted at least partially from differences in sampling effort along productivity gradients and systematic undersampling of species. We conclude that large‐scale processes such as passive dispersal and recurrent habitat recolonization dominate the distribution of species. Sampling protocols and data analyses must be improved in order to obtain estimates of diversity that are comparable across ecosystems.

The impact of fine‐scale turbulence on phytoplankton community structure

Lay AbstractThe mechanisms that maintain the great diversity of marine phytoplankton are not well understood. In particular, the widespread distribution and survival of large phytoplankton cells in the ocean are paradoxical, as they are at a distinct competitive disadvantage compared with smaller cells. The growth of large phytoplankton is typically limited by the diffusive supply of essential nutrients, whereas smaller cells have a greater surface‐area‐to‐volume ratio and are thus able to acquire sufficient resources more effectively via diffusion. Here, we employ a model of the diverse marine phytoplankton community to show that fine‐scale turbulence, a defining and ubiquitous feature of the ocean environment, aids the survival of large cells by increasing their effective supply of critical nutrients. This ecological impact of turbulence becomes most important in regions with established grazer populations, with high inputs of turbulent kinetic energy, and where nutrients have been exhausted, such as in the middle and high latitudes in summer and the trade wind latitudes of the tropics and subtropics. Our work shows that the presence of turbulence can have profound impacts on the size structure of the marine phytoplankton community.

Conventional sampling methods severely underestimate phytoplankton species richness

Conventional methods for the estimation of marine phytoplankton diversity include the collection of a small volume of seawater which is analysed under the microscope. We sampled natural communities and also synthetic communities generated under a neutral community model configuration and demonstrate that traditional sampling methods underestimate the species richness of marine phytoplankton communities. In our model, a synthetic community represents an ensemble of individuals enclosed in a parcel of seawater wherein the dynamics of each population is controlled by demographic stochasticity and dispersal. By sampling these synthetic communities, we found that roughly 20–45% of the species is missed by conventional, small volume samples. Consistent with the simulations, field data showed that the number of species increases with sampling effort by up to 1.5-fold, revealing that these microbial communities might be more diverse than previously estimated. We suggest that conventional sampling methods have limited our ability to delineate the patterns of marine phytoplankton diversity and identify the underlying mechanisms. Improved sampling methods are proposed to obtain more accurate estimates of marine phytoplankton diversity.

Dispersal, eddies, and the diversity of marine phytoplankton

Lay AbstractPhytoplankton are the “plants” of the ocean; they fix carbon dioxide from the atmosphere and make up the base of the oceanic food chain. Phytoplankton are incredibly diverse, but the reason for their high biodiversity is not well understood. Generally speaking, phytoplankton might be present in a given location either because they are “happy” and able to grow there, or if they are unable to grow there, because they have been transported in from elsewhere (i.e., via dispersal). Previous studies have suggested that “hotspots” of high phytoplankton diversity found in the most dynamic oceanic regions can be explained by dispersal. We explored this question by using a set of computer simulations of phytoplankton ecology coupled to a realistic ocean circulation. We show that dispersal can only partly explain diversity hotspots. The mixing of populations by ocean currents and eddies is important, but a plentiful supply of nutrients and variable environmental conditions also enhance phytoplankton diversity. This work has generated hypotheses that will stimulate new projects to test them in the field.

Top-down control of marine phytoplankton diversity in a global ecosystem model

The potential of marine ecosystems to adapt to ongoing environmental change is largely unknown, making prediction of consequences for nutrient and carbon cycles particularly challenging. Realizing that biodiversity might influence the adaptation potential, recent model approaches have identified bottom-up controls on patterns of phytoplankton diversity regulated by nutrient availability and seasonality. Top-down control of biodiversity, however, has not been considered in depth in such models. Here we demonstrate how zooplankton predation with prey-ratio based food preferences can enhance phytoplankton diversity in a ecosystem-circulation model with self-assembling community structure. Simulated diversity increases more than threefold under preferential grazing relative to standard density-dependent predation, and yields better agreement with observed distributions of phytoplankton diversity. The variable grazing pressure creates refuges for less competitive phytoplankton types, which reduces exclusion and improves the representation of seasonal phytoplankton succession during blooms. The type of grazing parameterization also has a significant impact on primary and net community production. Our results demonstrate how a simple parameterization of a zooplankton community response affects simulated phytoplankton community structure, diversity and dynamics, and motivates development of more detailed representations of top-down processes essential for investigating the role of diversity in marine ecosystems.

Diversity and evolution of marine phytoplankton

Marine phytoplankton organisms account for more than 45% of the photosynthetic net primary production on Earth. They are distributed across many of the major clades of the tree of life and include prokaryotes, and eukaryotes that acquired photosynthesis through the process of endosymbiosis. If the number of extant described species is relatively low compared to the diversity of the terrestrial plants, recent insights into the genetic diversity of natural assemblages have revealed a large unsuspected diversity at different taxonomic levels. Wide infra-specific diversity is also being discovered in many widespread and well known morphological species. This review summarizes data obtained in the fields of ecology, evolutionary biology, physiology and genomics that have improved our understanding of the biodiversity and evolution of marine phytoplankton. To cite this article: N. Simon et al., C. R. Biologies 332 (2009).

Species richness and cell-size distribution: size structure of phytoplankton communities

If the size dependence of species richness varies across ecosystems, it should be reflected in the size distribution of total abundance. Using a database of phytoplankton abundance, species composition and cell size from coastal, shelf and open-ocean environments, we show that the biogeographical patterns of phytoplankton size distribution in the ocean are a result of systematic changes in the relationship between species richness and cell size. Our results indicate that, regard- less of the environmental conditions, population abundance decreases consistently to the -3/4 power of cell size. By contrast, marine phytoplankton diversity peaks at small sizes in oligotrophic waters but is either a log-normal function or independent of cell size in eutrophic systems. It is argued that, operating on evolutionary time scales, size-dependent biophysical constraints for resource acquisi- tion are reflected in the size distribution of species richness and consequently in the size structure of phytoplankton communities in the ocean. These findings indicate that the way in which biological diversity changes with body size is crucial to a better understanding of the structure and functioning of microbial plankton communities and how energy flows through pelagic ecosystems.

Resource levels, allometric scaling of population abundance, and marine phytoplankton diversity

We analyzed the relationship between population abundance and cell size in phytoplankton assemblages from coastal, shelf, and open‐ocean environments. Our results show that across the entire size spectrum considered, population abundance increases over two orders of magnitude from subtropical to coastal regions. We find a highly significant linear relationship between nutrient concentration and the intercept of the log‐log relationship between population abundance and cell size. In contrast to overall patterns reported mainly for vascular plants and animals, marine phytoplankton diversity does not show any consistent trend along either latitudinal or productivity gradients. These results imply that large‐scale (biogeographic) variations in phytoplankton standing stocks are controlled by changes in population abundances rather than by systematic variations in species richness. These findings provide a mechanistic connection among nutrient availability, population dynamics, and phytoplankton diversity over macroecological scales.