Phytoplankton Species Research Articles

PHYTOPLANKTON COMMUNITY DYNAMICS RELATED TO CERTAIN PHYSICAL AND CHEMICAL VARIABLES IN ARDIÇTEPE RESERVOIR (BALIKESIR, TURKEY)

Ardıçtepe Reservoir (Balıkesir, Turkey) was sampled seasonally at three stations between October 2018 and August 2019 to determine the phytoplankton community dynamics in relation to water temperature, speciffic conductance (SC), total dissolved solids (TDS), pH, oxidation-reduction potential (ORP) and Secchi disk depth. A total of 43 phytoplankton species were identified, 27 from Bacillariophyta, 4 from Charophyta, 6 from Chlorophyta, 5 from Cyanobacteria and 1 from Euglenozoa. Bacillariophyta made 76% total number of species, Cyanobacteria 11%, Chlorophyta 6%, Charophyta 4% and Euglenozoa 3%. Aulacoseria granulata, Aulacoseira granulata var. angustissima, Cyclotella meneghiniana and Ulnaria ulna from Bacillariophyta and Anabaena circinalis from Cyanobacteria dominanted phytoplankton during the study. The CCA explained 90.8% of the cumulative variance in the relationships of dominant species-environment. The CCA also showed that water temperature, TDS, ORP and pH had significant effects on the phytoplankton community of Ardıçtepe Reservoir (Monte Carlo test, p 0.05)

Effects of the fungicide azoxystrobin in two habitats representative of mediterranean coastal wetlands: A mesocosm experiment

This paper investigates the effects of the fungicide azoxystrobin, a compound widely used in rice farming, on aquatic communities representative of two habitats characteristic of Mediterranean wetland ecosystems: water springs and eutrophic lake waters. The long-term effects of azoxystrobin were evaluated on several structural (phytoplankton, zooplankton, macroinvertebrate populations and communities) and functional (microbial decomposition, macrophyte and periphyton growth) parameters making use of freshwater mesocosms. Azoxystrobin was applied in two pulses of 2, 20, 200 µg/L separated by 14 d using the commercial product ORTIVA (23 % azoxystrobin w/w). The results show that these two habitats responded differently to the fungicide application due to their distinct physico-chemical, functional, and structural characteristics. Although overall sensitivity was found to be similar between the two (lowest NOEC < 2 µg/L), the taxa and processes that were affected differed substantially. In general, the most sensitive species to the fungicide were found in the water spring mesocosms, with some species of phytoplankton (Nitzschia sp.) or macrocrustaceans (Echinogammarus sp. and Dugastella valentina) being significantly affected at 2 µg/L. In the eutrophic lake mesocosms, effects were found on phytoplankton taxa (Desmodesmus sp. and Coelastrum sp.), on numerous zooplankton taxa, on chironomids and on the beetle Colymbetes fuscus, although at higher concentrations. The hemipteran Micronecta scholtzi was affected in both treatments. In addition, functional parameters such as organic matter decomposition or macrophyte growth were also affected at relatively low concentrations (NOEC 2 µg/L). Structural Equation Modelling was used to shed light on the indirect effects caused by azoxystrobin on the ecosystem. These results show that azoxystrobin is likely to pose structural and functional effects on Mediterranean wetland ecosystems at environmentally relevant concentrations. Moreover, it highlights the need to consider habitat-specific features when conducting ecotoxicological research at the population and community levels.

Plankton dynamics and physico-chemical parameters: A longitudinal investigation in carp and catfish culture ponds

An experiment was aimed to discover the overall scenario of physico-chemical parameters along with the qualitative and quantitative analysis of plankton in two different fish culture systems as carp mixed culture and catfish (Pangus) monoculture from September 2021 to February 2022 using conventional techniques. The mean values of transparency and dissolved oxygen (DO) noted at the catfish culture pond were lower than those at the mixed carp culture pond while pH mean values were observed to be higher in the catfish culture pond than in the mixed carp culture pond. A total of 21 genera of phytoplankton were found in both ponds under the groups of euglenophyceae (4), cyanophyceae (4), bacillariophyceae (5) and chlorophyceae (8). Among zooplankton, 13 genera were identified including Rotifera (7), copepoda (2), cladocera (3) and crustacean larvae (1) were recorded in mixed culture ponds whereas in catfish culture ponds, 11 zooplankton genera were recorded including Rotifera (5), copepoda (2), cladocera (3) and crustacean larvae (1). Planktonic abundances were statistically significantly different between the different levels (phytoplankton abundance in CCP, phytoplankton abundance in MCP, zooplankton abundance in CCP, zooplankton abundance in MCP), χ2(3) = 220.46, p &lt; 0.001. Mixed culture pond cyanophyceae, bacillariophyceae, and euglenophyceae are positively associated with water temperature and pH but negatively correlated with DO. Rotifera is negatively associated with catfish culture pond water temperature, whereas chlorophyceae and cyanophyceae are favorably. Catfish monoculture ponds had higher phytoplankton abundance, so phytoplankton grazing fish species could be included with pangus culture to maintain a better water quality.

Influence of circulation processes on cyanobacteria bloom and phytoplankton succession in the Baltic Sea coastal area

Many studies related to the influence of eddies on the primary production chain of marine ecosystems have been conducted; however, this effect tends to be regionally specific, especially in coastal dynamic waters. In the Baltic Sea, mesoscale and submesoscale eddies are a ubiquitous feature of water circulation during summer, when diazotrophic cyanobacteria blooms occur in surface waters due to the excess of phosphorus in seawater. Climatic change may increase the frequency and duration of these negative events in the marine ecosystem. We examined the taxonomic composition, abundance, and primary production of phytoplankton in the southeastern Baltic Sea during the occurrence of the packed eddy system at the end of the abnormally warm summer of 2018. Massive cyanobacteria growth was observed in the plume of the eutrophic Vistula Lagoon in the Gulf of Gdansk. The only species diazotrophic Dolichospermum flos-aquae ((Bornet &amp; Flahault) P. Wacklin, L. Hoffmann &amp; Komárek, 2009) vegetated along the western coast of the Sambia Peninsula. Its colonies reached the highest biomass nearby the dumping site of the Amber Mining Plant in Yantarny, Kaliningrad Region, Russia. The cyanobacteria colonies dispersed in the outgoing jet of a relatively warm eddy dipole. Chrysochromulina spp. (Lackey, 1939) was dominant in these nitrogen-rich waters. In contrast, cryptophyte species dominated in the relatively cold waters of the dipole anticyclone that resulted in a fourfold decline in primary production. The decrease in the number of mobile phytoplankton species was revealed within the “old” eddies near the northern coast of the Sambia Peninsula and the Curonian Spit. Meanwhile, species of the spring–autumn complex Coscinodiscus granii (Gough, 1905), Peridiniella catenate ((Levander) Balech, 1977) and other developed in the community. This implies that the appearance of eddies can cause phytoplankton succession in the coastal area. The mechanism of their influence was similar to the action of other physical factors perturbing a relatively stationary environment. Capture of cyanobacterial colonies by eddies led to an improvement of the ecological situation in the area, as cyanobacteria transported their biomass outside the coastal area. However, the opposite direction processes obviously were the deterioration of light conditions, increased water turbidity, and organic matter concentration.

Anthropogenic nutrients and phytoplankton diversity in Kenya's coastal waters: An ecological quality assessment of sea turtle foraging sites

We assessed ecological quality status (EQS) of coastal waters following claims of increasing sea turtle fibro-papillomatosis (FP) infections in Kenya, a disease hypothesized to be associated with ‘poor’ ecological health. We established widespread phosphate (P) and silicate (Si) limitation, dissolved ammonium contamination and an increase in potential harmful algal blooming species. Variations in the EQS was established in the sites depending on the indicators used and seasons. Generally, more sites located near hotels, tidal creeks, and estuarine areas showed ‘poor’, and ‘bad’ EQS during rainy period compared to dry season. Additionally, 90.1 % of the sites in ‘poor’ and ‘bad’ EQS based on dissolved inorganic nitrogen. Low dissolved oxygen, elevated temperature, salinity and ammonium, ‘poor’ EQS based on DIN, and potential bio-toxin-producing phytoplankton species characterized the FP prevalent areas, specifically during the dry season suggesting environmental stress pointing to the hypothesized connection between ecological and sea turtle health.

Mathematical Model of Phytoplankton Interspecific Competition for Food Resource

The phytoplankton in an aquatic ecosystem is the basis of its life activity and the main producing link. The functioning of phytoplankton in same time depends on environmental factors: mineral nutrition, photosynthetically active solar radiation, water temperature and other less significant ones. Sunlight is a stable factor, varying predictably over time and space. The water temperature is the small regulatory factor. Concentrations of mineral substances can change quite quickly and significantly, this much influences on plant organisms. Thus, mineral nutrition is a basic environmental factor of influence to phytoplankton. On the other hand, in large aquatic basin such as seas and oceanic areas the distribution of living organisms is very heterogeneous in space. These two aspects – nutrient and spatial heterogeneity – are the focus of this article. A model of competitive interaction is considered using the example of two species of phytoplankton. The phytoplankton move passively in water what is simulated by the diffusion process. The model contains one non-trivial stationary and spatially homogeneous equilibrium and two trivial ones, i.e. degenerate in at least one species of phytoplankton. Trivial equilibria are stable only in some “degenerate” situations. The non-trivial equilibrium in “normal” conditions is stable to temporal and spatial disturbances. The behavior of solutions near a nontrivial equilibrium for a stationary living environment and in cases of its nonstationary is studied. Perturbation of a nontrivial equilibrium in a stationary environment leads to relatively long-term deviations from equilibrium and a slow return to it. The instability of trivial equilibria increases the spatial heterogeneity of solutions. At the same time, the nontrivial equilibrium computationally demonstrates weak properties of global stability in time. The unsteadiness of the environment is simulated by the unsteadiness of the influx of nutrients. It has been shown that the distribution of nutrients can lead to significant heterogeneity in the distribution of individuals across the spatial habitat.

Mercury species induce metabolic reprogramming in freshwater diatom Cyclotella meneghiniana

Mercury is a hazardous pollutant of global concern. While advances have been made in identifying the detrimental effects caused by Hg species in phytoplankton, knowledge gaps remain regarding the metabolomic perturbations induced by inorganic mercury (Hg(II)) and monomethylmercury (MeHg) in these organisms. Diatoms represent a major phytoplankton group essential in various global biogeochemical cycles. The current study combined targeted metabolomics, bioaccumulation, and physiological response assays to investigate metabolic perturbations in diatom Cyclotella meneghiniana exposed for 2 h to nanomolar concentrations of Hg(II) and MeHg. Our findings highlight that such exposures induce reprogramming of the metabolism of amino acids, nucleotides, fatty acids, carboxylic acids and antioxidants. These alterations were primarily mercury-species dependent. MeHg exposure induced more pronounced reprogramming of the metabolism of diatoms than Hg(II), which led to less pronounced effects on ROS generation, membrane permeability and chlorophyll concentrations. Hg(II) treatments presented distinct physiological responses, with more robust metabolic perturbations at higher exposures. The present study provides first-time insights into the main metabolic alterations in diatom C. meneghiniana during short-term exposure to Hg species, deepening our understanding of the molecular basis of these perturbations.

Ecotoxicology of Polymetallic Nodule Seabed Mining: The Effects of Cobalt and Nickel on Phytoplankton Growth and Pigment Concentration.

In order to improve the understanding of the environmental impacts of polymetallic nodule mining, ecotoxicological studies were conducted on the growth of model phytoplankton species Skeletonema costatum and Prorocentrum donghaiense using cobalt and nickel. This study evaluated various physiological and ecological indicators, such as cell proliferation, chlorophyll a, pigments, total protein, and antioxidant enzyme markers. The results show that the introduction of low amounts of cobalt or nickel increased the growth rate of phytoplankton. The phytoplankton benefited from low concentrations of cobalt and nickel stress. The increased protein levels and decreased activity of antioxidant enzymes considerably impacted physiological responses during the promotion of cell abundance. High concentrations of cobalt or nickel resulted in decreased light-absorbing pigments, increased photoprotective pigments, an inactive chlorophyll content, decreased total proteins, and maximal antioxidant enzyme activity in phytoplankton. Throughout the experiment, both the phytoplankton protein and enzyme activity declined with prolonged stress, and the cells underwent age-induced damage. Thus, seabed mining's repercussions on phytoplankton could result in both short-term growth promotion and long-term damage. These consequences depend on the impurity concentrations infiltrating the water, their duration, and the organism's physiological responses.

Competition between Dissolved Organic Matter and Freshwater Plankton Control Methylmercury Isotope Fractionation during Uptake and Photochemical Demethylation.

Isotope fractionation related to photochemical reactions and planktonic uptake at the base of the food web is a major uncertainty in the biological application of mercury (Hg) stable isotopes. In freshwater systems, it is unclear how competitive interactions among methylmercury (MeHg), dissolved organic matter (DOM), and phytoplankton govern the magnitude of mass-dependent and mass-independent fractionation. This study investigated how DOM alters rates of planktonic MeHg uptake and photodegradation and corresponding Hg isotope fractionation in the presence of freshwater phytoplankton species, Raphidocelis subcapitata. Outdoor sunlight exposure experiments utilizing R. subcapitata were performed in the presence of different DOM samples using environmentally relevant ratios of MeHg-DOM thiol groups. The extent of Δ199Hg in phytoplankton incubations (2.99‰ St. Louis River HPOA, 1.88‰ Lake Erie HPOA) was lower compared to paired abiotic control experiments (4.29 and 2.86‰, respectively) after ∼30 h of irradiation, resulting from cell shading or other limiting factors reducing the extent of photodemethylation. Although the Δ199Hg/Δ201Hg ratio was uniform across experiments (∼1.4), Δ199Hg/δ202Hg slopes varied dramatically (from -0.96 to 15.4) across incubations with R. subcapitata and DOM. In addition, no evidence of Hg isotope fractionation was observed within R. subcapitata cells. This study provides a refined examination of Hg isotope fractionation markers for key processes occurring in the lower food web prior to bioaccumulation, critical for accurately accounting for the photochemical processing of Hg isotopes across a wide spectrum of freshwater systems.

Scenarios of temporal environmental alterations and phytoplankton diversity in a changing bay in the East China Sea

In the context of global change, the stressors of warming and eutrophication have significant ecological implications in coastal waters. In order to examine the diversity of phytoplankton and its relationship with water quality, we conducted a survey of phytoplankton community compositions and their correlation with environmental changes over four seasons in a eutrophic bay located in the East China Sea. Through a systematic analysis, we identified diatoms and dinoflagellates as the primary dominant groups, with the species Skeletonema costatum, Skeletonema marinoi, Biddulphia sinensis, Thalassiosira eccentrica, Leptocylindrus danicus, Coscinodiscus oculus-iridis, Coscinodiscus jonesianus, and Chaetoceros knipowitschi as the most abundant species in all seasons. Significant seasonal alterations were observed in both environmental settings and phytoplankton species richness, dominance, and abundance. The phytoplankton community varied in its response to diverse aquatic environments and was principally affected by temperature, silicic acid concentrations, and suspended solids. Elevated temperatures were found to promote an increase in phytoplankton abundance. However, no clear evidence of diatom and dinoflagellate succession in relation to N:P ratio was observed across seasons. Water quality analysis illustrated that the majority of the study area exhibited a mid-eutrophic with severe organic pollution. The abundance of phytoplankton was significantly influenced by eutrophication and organic pollution. The accelerated warming process related to coastal nuclear power plants and nutrient regime alterations significantly affect the temporal shift of the phytoplankton community. These findings contribute valuable insights into the effects of eutrophic environments on the structure of phytoplankton communities in coastal aquatic systems.

Dynamics of a Plankton-Fish Model with Infection in Phytoplankton Species

Dynamics of a Plankton-Fish Model with Infection in Phytoplankton Species

Alpha diversity of planktonic organisms across stream networks associated with mining activities in Southeast Sulawesi

Planktonic organisms are the main biotic components of the food chain of aquatic ecosystems. Little is known about the impact of multiple stressors on plankton community response in mining areas. This study aimed to elucidate the alpha diversity of zooplankton and phytoplankton in different stream networks associated with mining activities in the Molore watershed, Southeast Sulawesi. The research was carried out by taking samples for water quality and plankton analyses in four streams in November 2021 and November 2022. A rarefaction curve approach was used to assess the species richness and diversity trends of the region. Streams were clustered using the Bray-Curtis similarity index of alpha diversity indices, such as the Shannon-Wiener, Simpson, Margalef, Pielou, and Berger-Parker indices. We found six species of zooplankton only in three sites and 21 species of Phytoplankton in the class of Bacillariophyceae, Chlorophyceae, Cyanophyceae, Dinophyceae, and Euglenophyceae across the landscape gradient. The present study showed that the lowest value of the Shannon-Wiener diversity of the plankton community was 0.48, while the maximum expected value based on individuals’ rarefaction curve was 2.24. Species richness is in line with cluster analysis, which shows the similarity of stream groups according to the level of environmental pressure, indicating a valuable ecological indicator for stream management.

Dynamics of Phytoplankton Species Structure in the Kurile Lake (Kamchatka Peninsula)

Dynamics of Phytoplankton Species Structure in the Kurile Lake (Kamchatka Peninsula)

Community structure of phytoplankton in Downstream of the Segedong River, Kubu Raya Regency, West Kalimantan

The Segedong River flows between the Tanjung Prapat Muda Mangrove Protected Forest in Kubu Raya Regency. Mangrove forests contribute nutrients to water. However, nutrients and fluctuative environmental conditions influence the existence of phytoplankton. People’s settlements and fish farming activities downstream of ​​the Segedong River influence environmental conditions. Research on phytoplankton is needed to determine the quality of the Segedong River. The aim of this research is to determine the abundance and diversity of phytoplankton in the downstream Segedong River. Sampling was carried out in the dry and rainy seasons using a survey method at 3 stations. Water physicochemical factors are measured in situ and ex situ. The identified phytoplankton species are then calculated for their abundance, diversity index, evenness, and dominance. 59 phytoplankton species are categorized into 6 classes, including Bacillariophyceae (35 species), Dinophyceae (15 species), Chlorophyceae (4 species), Cyanophyceae (3 species), Chrysophyceae (1 species) and Xanthophyceae (1 species). The phytoplankton abundance obtained in both seasons at all stations ranged from 1,314-10,185 Ind.L-1 or categorized into oligotrophic to mesotrophic. The diversity index ranges from 1.99-2.88 in the medium category. The evenness index ranges from 0.53-0.80, which is in the medium to high category, while the dominance index is low &lt;0.4.

Predictable shifts in diversity and ecosystem function in phytoplankton and zooplankton communities along thermocline stratification intensity continua

Thermocline stratification is a global threat to water quality in drinking water reservoirs, though its underlying mechanisms are not clear. The impacts of thermocline stratification intensity on biodiversity-ecosystem relationships were assessed using phytoplankton and zooplankton indicators from four stages of stratification in Lake Qiandaohu. There were significant differences in biomass, species diversity, and resource use efficiency (RUEpp = phytoplankton biomass/total phosphorus) for phytoplankton between continuous stratification and mixing periods, but only in FDis and RaoQ diversity indices for zooplankton. Phytoplankton species diversity and RUE were higher in the formative and stable periods, while zooplankton species diversity and zooplankton biomass/phytoplankton biomass (RUEzp) were lower. When combining the data from the four periods, a negative linear pattern was found between phytoplankton Simpson's, functional dispersion (FDis), and Rao's Quadratic (RaoQ) diversity indices, and thermocline depth (TD). Only zooplankton FDis and RaoQ diversity indices were significantly positively related to TD. Phytoplankton RUE was significantly negatively related only to its Pielou's evenness (J) diversity, while zooplankton RUE was significantly negatively related to its J, FDis, and RaoQ diversity indices. The results of structural equation models (SEMs) showed that the R2 of RUE for phytoplankton was much higher than that for zooplankton. Thermocline stratification intensity exerted an indirect positive effect on phytoplankton RUE by affecting species diversity but had a negative effect on zooplankton RUE. These findings underscore the negative influence of thermocline stratification resulting in various biodiversity changes in freshwater ecosystems.

Responses of globally important phytoplankton species to olivine dissolution products and implications for carbon dioxide removal via ocean alkalinity enhancement

Abstract. Anthropogenic greenhouse gas emissions are leading to global temperature increases, ocean acidification, and significant ecosystem impacts. Given current emissions trajectories, the IPCC's reports indicate that rapid abatement of CO2 emissions and development of carbon dioxide removal (CDR) strategies are needed to address legacy and difficult-to-abate emissions sources. These CDR methods must efficiently and safely sequester gigatons of atmospheric CO2. Coastal enhanced weathering (CEW) via the addition of the common mineral olivine to coastal waters is one promising approach to enhance ocean alkalinity for large-scale CDR. As olivine weathers, it releases several biologically active dissolution products, including alkalinity, trace metals, and the nutrient silicate. Released trace metals can serve as micronutrients but may also be toxic at high concentrations to marine biota, including phytoplankton, which lie at the base of marine food webs. We grew six species representing several globally important phytoplankton species under elevated concentrations of olivine dissolution products via a synthetic olivine leachate (OL) based on olivine's elemental composition. We monitored their physiological and biogeochemical responses, which allowed us to determine physiological impacts and thresholds at elevated olivine leachate concentrations, in addition to individual effects of specific constituents. We found both positive and neutral responses but no evident toxic effects for two silicifying diatoms, a calcifying coccolithophore, and three cyanobacteria. In both single and competitive co-cultures, silicifiers and calcifiers benefited from olivine dissolution products like iron and silicate or enhanced alkalinity, respectively. The non-N2-fixing picocyanobacterium could use synthetic olivine-derived iron for growth, while N2-fixing cyanobacteria could not. However, other trace metals like nickel and cobalt supported cyanobacterial growth across both groups. Growth benefits to phytoplankton groups in situ will depend on species-specific responses and ambient concentrations of other required nutrients. Results suggest olivine dissolution products appear unlikely to cause negative physiological effects for any of the phytoplankton examined, even at high concentrations, and may support growth of particular taxa under some conditions. Future studies can shed light on long-term eco-evolutionary responses to olivine exposure and on the potential effects that marine microbes may in turn have on olivine dissolution rates and regional biogeochemistry.

Trait-based classification and environmental drivers of phytoplankton functional structure from anthropogenically altered tropical creek, Thane Creek India

The present study on variability in phytoplankton functional structure through a trait-based approach described the species-trait-environmental relationship and its possible impact on ecosystem functioning. Based on trait similarities 102 phytoplankton species were clubbed into 14 distinct functional groups. Among others, FGs-XI and XII (small size, chain-forming species with medium to high SA:V ratio and space between cells in chain) were the most dominant due to their competitive advantage in resource utilization and avoidance of loss processes. The morphological traits space between cells and cellular protrusion along with temperature and ammonia played a decisive role in their seasonal succession. Eutrophication in Thane Creek favors the dominance of anti-grazing traits which increases the phytoplankton biomass through efficient resource acquisition but can encumber the energy transfer efficiency. The dominance of HAB species impedes ecosystem functioning which raises public health concerns. The strong correlation of environmental variables with phytoplankton functional structure reinforces the practical implementation of a trait-based approach for understanding phytoplankton community dynamics under varying environmental conditions.

Population and functional changes in a multispecies co-culture of marine microalgae and cyanobacteria under a combination of different salinity and temperature levels

Changes in the temperature or salinity of ocean waters can affect marine organisms at multiple trophic levels. Both environmental variables could have an impact on marine microalgae populations. Therefore, the effect of the combination of three levels of temperature (20, 24 and 28 °C), and three levels of salinity (33, 36, and 39 PSU) were evaluated on the growth of a multispecies community of five common species of phytoplankton: (one cyanobacteria, Synechococcus sp., and four microalgae, Chaetoceros gracilis, Amphidinium carterae, Pleurochrysis roscoffensis and Rhodomonas baltica). The co-culture was monitored by flow cytometry under controlled conditions in a 96 h study. The effect of both variables on dissolved oxygen concentrations was measured using the SDR SensorDish Reader system. The results demonstrated that Synechococcus sp., C. gracilis, and A. carterae displayed a high growth at the temperature of 28 °C combined with the lowest salinity assayed. However, salinity increases negatively affected the growth of P. roscoffensis and R. baltica. Decreased salinity combined with decreased temperature exhibited a higher net O2 production. The interaction of two environmental factors related to global change such as temperature and salinity can cause structural (community growth) and functional (net oxygen production) changes in a phytoplanktonic community.

Paradox of relatively more phospholipids in phytoplankton in phosphorus limited sea

AbstractMarine life is threatened by global warming and its indirect consequences, which include, among others, increased stratification leading to phosphorus (P) and nitrogen depletion in the upper water column. Phosphorus plays a key role in all biochemical systems; storage of metabolic energy, formation of genetic material, and subcellular compartmentalization. Our multi‐year study of lipid biogeochemistry in the northern Adriatic (Mediterranean), which is becoming warmer and nutrient‐poorer, particularly regarding P, has shown that under conditions of P scarcity, phospholipids are relatively more abundant and smaller plankton cells dominate. Consistent with the field data, experiments with seven phytoplankton monocultures, comprising microplankton, nanoplankton, and picoplankton, confirmed a relatively higher phospholipid content in the smaller phytoplankton species and, in particular, an increase in those grown under stress conditions in general, including, unexpectedly, P‐limitation. We suggest two reasons for the observed “P paradox” of P‐limited phytoplankton: (1) cell geometry: volume of the plasma membrane relative to the volume of the entire cell is greater in smaller cells and, therefore, the proportion of plasma membrane phospholipids to intracellular lipids is greater in smaller cells, (2) higher proportion of densely packed saturated fatty acids found in stressful conditions, including P oligotrophy, additionally increase the proportion of membrane phospholipids relative to intracellular lipids. Our findings contribute to the understanding of P cycling in the sea. In addition, our data suggest that higher phospholipid export to deep waters is possible by smaller plankton.

Cell size-dependent species sensitivity to nanoparticles underlies changes in phytoplankton diversity and productivity.

Nanoparticle pollution has been shown to affect various organisms. However, the effects of nanoparticles on species interactions, and the role of species traits, such as body size, in modulating these effects, are not well-understood. We addressed this issue using competing freshwater phytoplankton species exposed to copper oxide nanoparticles. Increasing nanoparticle concentration resulted in decreased phytoplankton species growth rates and community productivity (both abundance and biomass). Importantly, we consistently found that nanoparticles had greater negative effects on species with smaller cell sizes, such that nanoparticle pollution weakened the competitive dominance of smaller species and promoted species diversity. Moreover, nanoparticles reduced the growth rate differences and competitive ability differences of competing species, while having little effect on species niche differences. Consequently, nanoparticle pollution reduced the selection effect on phytoplankton community abundance, but increased the selection effect on community biomass. Our results suggest cell size as a key functional trait to consider when predicting phytoplankton community structure and ecosystem functioning in the face of increasing nanopollution.