Phytoplankton Ecology Research Articles

Space, the final frontier: The spatial component of phytoplankton-bacterial interactions.

Microscale interactions between marine phytoplankton and bacteria shape the microenvironment of individual cells, impacting their physiology and ultimately influencing global-scale biogeochemical processes like carbon and nutrient cycling. In dilute environments such as the ocean water column, metabolic exchange between microorganisms likely requires close proximity between partners. However, the biological strategies to achieve this physical proximity remain an understudied aspect of phytoplankton-bacterial associations. Understanding the mechanisms by which these microorganisms establish and sustain spatial relationships and the extent to which spatial proximity is necessary for interactions to occur, is critical to learning how spatial associations influence the ecology of phytoplankton and bacterial communities. Here, we provide an overview of current knowledge on the role of space in shaping interactions among ocean microorganisms, encompassing behavioural and metabolic evidence. We propose that characterising phytoplankton-bacterial interactions from a spatial perspective can contribute to a mechanistic understanding of the establishment and maintenance of these associations and, consequently, an enhanced ability to predict the impact of microscale processes on ecosystem-wide phenomena.

Sinking rates, orientation, and behavior of pennate diatoms.

Phytoplankton cells are now recognized as dynamic entities rather than as passive and isolated particles because they can actively modulate impacts of selection factors (nutrients, light, turbidity, and mixing) through a wide range of adaptations. Cell shape and/or chain length modulation is one of these processes but has predominantly been studied as an adaptation or an acclimatation to a specific growth limitation (light, nutrients, predation, etc.). In this study we have demonstrated that cell shape and size may have greater roles than previously known in phytoplankton ecology and species adaptation by permitting cell-to-cell signaling and more complex ecological processes that result from it. By exploring microscale biophysical interactions that lead to specific cell reorientation processes, we demonstrated that cell geometry not only modulates cell sinking rates but can also provide fast sensor responses to the cells' environment. Although gyrotaxis has been described in detail for motile phytoplankton cells, our findings illustrate that the reorientation process described here can occur even in non-motile cells within their natural environment. An additional consistent behavior was also recently described for a diatom species (Pseudo-nitzschia delicatessima), and with this study, we extend this observation to Pseudo-nitzschia pungens and Pseudo-nitzschia fraudulenta. Our observations emphasize the generality of this process, which adds a new level of complexity to our understanding of cellular interactions and their network of sensors.

Polyphosphate phosphorus in the Great Lakes

AbstractPolyphosphate (polyP) is important to phytoplankton ecology, but a unified view of its variability and roles in ecosystem‐scale phosphorus (P) cycling is lacking. We study polyP in the world's largest freshwater ecosystem, the Laurentian Great Lakes, covering pelagic to nearshore areas across a wide nutrient gradient. We show that polyP (average 10.99 ± 3.90 nmol L−1) constitutes 3.8–30.2% (average 18.1 ± 7.2%) of total particulate P (TPP). PolyP accumulation is higher in low‐P pelagic waters compared with more productive nearshore areas. PolyP is preferentially degraded in the water column of the Great Lakes, enhancing P recycling and relieving the nitrogen (N) : P imbalance. Our data enables a coherent large‐scale freshwater‐to‐oceanic comparison. We show that while different plankton groups accumulate different levels of polyP with smaller plankton accumulating more, P availability is the key driver of polyP variability within and across systems.

Phytoplankton ecology in the early years of a boreal oil sands end pit lake

BackgroundBase Mine Lake (BML) is the first full-scale end pit lake for the oil sands mining industry in Canada. BML sequesters oil sands tailings under a freshwater cap and is intended to develop into a functional ecosystem that can be integrated into the local watershed. The first stage of successful reclamation requires the development of a phytoplankton community supporting a typical boreal lake food web. To assess the diversity and dynamics of the phytoplankton community in BML at this reclamation stage and to set a baseline for future monitoring, we examined the phytoplankton community in BML from 2016 through 2021 using molecular methods (targeting the 23S, 18S, and 16S rRNA genes) and microscopic methods. Nearby water bodies were used as controls for a freshwater environment and an active tailings pond.ResultsThe phytoplankton community was made up of diverse bacteria and eukaryotes typical of a boreal lake. Microscopy and molecular data both identified a phytoplankton community comparable at the phylum level to that of natural boreal lakes, dominated by Chlorophyta, Cryptophyta, and Cyanophyta, with some Bacillariophyta, Ochrophyta, and Euglenophyta. Although many of the same genera were prominent in both BML and the control freshwater reservoir, there were differences at the species or ASV level. Total diversity in BML was also consistently lower than the control freshwater site, but consistently higher than the control tailings pond. The phytoplankton community composition in BML changed over the 5-year study period. Some taxa present in 2016–2019 (e.g., Choricystis) were no longer detected in 2021, while some dinophytes and haptophytes became detectable in small quantities starting in 2019–2021. Different quantification methods (qPCR analysis of 23S rRNA genes, and microscopic estimates of populations and total biomass) did not show a consistent directional trend in total phytoplankton over the 5-year study, nor was there any consistent increase in phytoplankton species diversity. The 5-year period was likely an insufficient time frame for detecting community trends, as phytoplankton communities are highly variable at the genus and species level.ConclusionsBML supports a phytoplankton community composition somewhat unique from control sites (active tailings and freshwater lake) and is still changing over time. However, the most abundant genera are typical of natural boreal lakes and have the potential to support a complex aquatic food web, with many of its identified major phytoplankton constituents known to be primary producers in boreal lake environments.

Widespread Geographical Disparities in Phytoplankton Ecology Research in the Face of Climate Change: A Review

Climate change is a global threat that is better understood through global research spanning many regions, countries, and life-supporting ecosystems. This review focused on the bibliometric analysis of the distribution of a global research compendium on phytoplankton, an aquatic community that accounts for half of the carbon fixation in the global carbon cycle. A total of 716 primary research papers published in the immediate past decade (2012–2022) were reviewed. The articles were sampled from Web of Science and described field and laboratory experiments quantifying the impact of global climate change on phytoplankton from different climate zones (tropical, subtropical, temperate, subpolar, and polar) and ecosystems (freshwater, brackish, and marine). Analyses of these studies suggest that the bulk of the global research effort (80%) focused on high-latitude areas, and only a few (17%) were carried out in the tropics, largely led by four countries (Australia, Brazil, India, and Saudi Arabia), while Africa’s contribution was minuscule (<1%). In terms of ecosystems, the majority (76%) of the research was in marine waters, irrespective of the climate zone. Analyses of these studies also highlighted widespread disparities in phytoplankton research in tropical aquatic ecosystems, particularly in Africa. Strategic investment in terms of targeted funding, institutional networks, and partnerships between the global north and global south are necessary to increase phytoplankton research across different ecosystems in the tropics.

An integrated individual-level trait-based phytoplankton dataset from transitional waters

Functional trait-based approaches have undergone an extraordinary expansion in phytoplankton ecology. Morpho-functional traits have been shown to vary both within and between populations and species, potentially affecting individual fitness and the network of inter-individual relationships. Here we integrate six fully harmonized phytoplankton morpho-functional trait datasets, characterized by a fine data grain, reporting individual-level data over a large biogeographical area. Datasets refer to transitional water ecosystems, from five biogeographical areas: Northern Atlantic Ocean (Scotland), South-Western Atlantic Ocean (Brazil), South-Western Pacific Ocean (Australia), Indo Pacific Ocean (Maldives) and Mediterranean Sea (Greece and Turkey). The integrated dataset includes 127311 individual phytoplankton records with sampling locations, taxonomic and morphometric information according to Darwin Core standards and semantic annotations. The six FAIR datasets are openly available in the LifeWatch Italy data portal. The datasets have already been used for morpho-functional analyses and hypothesis testing on phytoplankton guilds at different levels of data aggregation and scale, from local to global.

Riverine connectivity influences the phytoplankton ecology in the open floodplain wetland of the lower river Ganga.

The river Ganga has several floodplain wetlands that support its ecology and ecosystem. Phytoplankton is an important component of the aquatic ecosystem, which plays an important role as a bioindicator for the assessment of aquatic health. The present study was conducted between 2018 and 2019 to understand the seasonal variation in the phytoplankton diversity of the Charaganga wetland and, parallelly, in the river Ganga in Nabadweep, India. The study explains how riverine connectivity affects the structure of the algal community in the wetland ecosystem. In the study, it has been observed that in the wetland, maximum mean phytoplankton density was noticed during pre-monsoon, i.e., 4079 unit l-1 followed by post-monsoon 3812 unit l-1 and monsoon 550 unit l-1, respectively. In the river system, the phytoplankton density varied from 78unit l-1 to 653 unit l-1 seasonally, i.e., highest during monsoon and lowest during pre-monsoon. In both the ecosystems, i.e., wetland and river, the supreme influential group was Cyanophyceae followed by diatoms. One-way ANOVA showed a significant variation (p > 0.05) of three algal groups of phytoplankton (Bacillariophyceae, Coscinodiscophyceae, Chlorophyceae) in the river, while in the wetland, no significant variation(p > 0.05) was found among the other algal groups. The observed higher Shannon and Margalef's species richness value in the wetland was observedthan in the river defines the significance and importance of the wetland ecosystem, which may support the growth and conservation of various aquatic organisms as well. The study highlighted that the influencing abiotic factors like water temperature, dissolved oxygen, pH, and nutrients have affected the phytoplankton community in both the water bodies, i.e., wetland and river. We concluded that river connectivity is required to restore the biotic flora of the wetland ecosystem.

Seasonal dynamics of phytoplankton community assembly at the Blanes Bay Microbial Observatory (BBMO), NW Mediterranean Sea

The dynamics of phytoplankton biomass and community composition is important for the functioning of marine ecosystems and ocean biogeochemical cycles. However, there is a shortage of studies addressing the interannual seasonal patterns of phytoplankton community assembly due to sampling limitations. Here we study the seasonal dynamics of eight major phytoplankton groups over a 12 year period (2006 to 2018) using a time-series of taxonomic composition from the Blanes Bay Microbial Observatory (BBMO) in the North Western Mediterranean Sea: dinoflagellates, diatoms, coccolithophores, Prochlorococcus, Synechococcus, picoeukaryotes, nanoeukaryotes, and photosynthetic nanoflagellates. We combine the analysis of biotic factors (primary production, phytoplankton taxa, cell abundance, cell size, chlorophyll-a concentration, and phytoplankton biomass) and abiotic factors (nutrients, temperature, and irradiance) to provide a coherent picture of the observed seasonal patterns of phytoplankton community assembly. The BBMO ecosystem is seasonally heterogeneous in community composition, displaying large fluctuating alternations in phytoplankton group dominance throughout the year. The seasonal succession of phytoplankton groups tends to repeat itself every year in a regular fashion, being the seasonal variability of the phytoplankton groups larger than their interannual variability. We compute α-diversity, a measure of the effective richness of phytoplankton groups. The seasonality of α-diversity shows that it is lowest during winter and highest during summer. We compute temporal β-diversity, a measure of compositional heterogeneity of the phytoplankton community. The data show a sinusoidal behavior of β-diversity as a function of the temporal distance between samples, with a period of one year. We use the mirror index (1 - β-diversity) at a temporal distance of one month to compute the phytoplankton group turnover. The seasonality of turnover shows that it is highest during spring and autumn. To evaluate the validity of niche and neutral theories in predicting the interannual sinusoidal behavior of β-diversity, we performed numerical simulations using a mechanistic model. The results provide support to the niche theory for marine phytoplankton ecology and community assembly. The phytoplankton groups appear to follow their specific ecological niches, tracking the seasonal changes in environmental conditions. The ecological implications of these findings are that marine phytoplankton groups appear to fill distinct environmental niches and thus may have different functional roles in the ecosystem. Furthermore, they may be predictable using both mechanistic and species distribution modeling approaches. The climatological time-series presented here can be an excellent testing ground for evaluating the performance of these marine ecosystem models having an explicit representation of different phytoplankton groups.

MAREL Carnot data and metadata from the Coriolis data center

Abstract. The French coast of the eastern English Channel (ECC) is classified as a potential eutrophication zone by the Oslo and Paris (OSPAR) Convention and as moderate to poor according to the phytoplankton quality element of the Water Framework Directive (WFD). It is regularly affected by Phaeocystis globosa bloom events, which have detrimental effects on the marine ecosystem, economy, and public health. In this context and to improve our observation strategy, MAREL Carnot, a multi-sensor oceanographic station, was installed in the eastern English Channel in 2004 at the Carnot wall in Boulogne-sur-Mer. The aim of this station was to collect high-frequency measurements of several water quality parameters to complement conventional low-resolution monitoring programs. The purpose of this paper is to describe the MAREL Carnot dataset and show how it can be used for several research objectives. MAREL Carnot collects high-frequency, multi-parameter observations from surface water as well as meteorological measurements and sends the data in near real-time to an onshore data center. In this paper, we present several physical, chemical, and biological parameters measured by this station. We also demonstrate that the MAREL Carnot dataset can be used to assess environmental or ecological statuses and conduct research in the field of marine phytoplankton ecology and oceanography. In addition, we show that this dataset may indirectly aid in improving European environmental management strategies. The MAREL Carnot dataset is publicly accessible via https://doi.org/10.17882/39754 (MAREL Carnot, 2023).

Spatial and temporal variability of phytoplankton dynamics in-relation to essential oceanographic variables in the south east coast of Bangladesh

Phytoplankton form the base of food chain and play a key role in maintaining the global climate system. However, very limited knowledge is available about the phytoplankton ecology of Bangladesh coast which is a representation of sub-tropical coastal ecosystem. Thus, this study aimed to understand the spatial and temporal variability of phytoplankton community in-relation to environmental variables in the South East coast of Bangladesh. Monthly data on essential oceanographic variables (i.e. temperature, salinity, dissolved oxygen, turbidity, silicate, nitrate and phosphate) and phytoplankton species abundance were collected from January 2022 to December 2022. We found a strong spatial and temporal variability in essential oceanographic variables and phytoplankton community compositions in Naf – Saint Martin Peninsula of Bangladesh. Estuarine ecosystem is characterized by high nutrients and low salinity while offshore ecosystem was found with comparatively low nutrients and high salinity. About 154 phytoplankton species were identified from the study area through year round sampling events. In the estuarine ecosystem Skeletonema marino, Coscinodiscus centralis, Coscinodiscus argus and Coscinodiscus traducens were found as the major contributing species at the estuarine ecosystem while Chaetoceros radican, Tripos trichoceros, Cylindrotheca Closterium, Chaetoceros convulutus, Tripos muelleri, and Cyclotella striata were found as the major contributing species at the offshore ecosystem. Our study found that 6 explanatory variables (i.e. temperature, salinity, turbidity, silicate, nitrate and phosphate) jointly explained about 78% variability in phytoplankton community dynamics. Nitrate concentration explained maximum variability (19%) followed by phosphate (17%), salinity (15%), silicate (12%), turbidity (10%) and surface temperature (5%). This study will play a key role in understanding the spatial and temporal variability of phytoplankton dynamics in the sub-tropical coastal ecosystem.

Evaluating Underwater Light Availability for Phytoplankton: Mean Light Intensity in the Mixed Layer versus Attenuation Coefficient

The use of several light-related variables, such as the Secchi disc depth, the euphotic depth, and in particular, the diffuse attenuation coefficient (Kd), is deeply rooted in phytoplankton research, but these are not the most appropriate indicators of the amount of light available for photosynthesis. We argue that the variable of interest for phytoplankton is the mean light intensity in the mixed layer (Im), which represents the mean light to which phytoplankton cells are exposed throughout their life cycle, while being continuously mixed in the mixed layer. We use empirical data collected in different coastal ecosystems in southern Portugal to demonstrate why Im should be the preferred metric instead of the deeply rooted Kd. We show that, although the relationship between Im and Kd is inversely proportional, it is not always strong or even significant. Different Im values can be associated with the same Kd, but distinct Im have different physiological effects of phytoplankton. Therefore, Kd does not capture the amount of light available for photosynthesis, given that, unlike Im, Kd calculation does not consider the depth of the mixed layer. Therefore, we urge phytoplankton researchers to consider the measurement and calculation of Im when evaluating light-related processes in phytoplankton ecology.

Oceanic Frontal Divergence Alters Phytoplankton Competition and Distribution

AbstractEcological interactions among phytoplankton occur in a moving fluid environment. Oceanic flows can modulate the competition and coexistence between phytoplankton populations, which in turn can affect ecosystem function and biogeochemical cycling. We explore the impact of submesoscale velocity gradients on phytoplankton ecology using observations, simulations, and theory. Observations reveal that the relative abundance of Synechoccocus oligotypes varies on 1–10 km scales at an ocean front with submesoscale velocity gradients at the same scale. Simulations in realistic flow fields demonstrate that regions of divergence in the horizontal flow field can substantially modify ecological competition and dispersal on timescales of hours to days. Regions of positive (negative) divergence provide an advantage (disadvantage) to local populations, resulting in up to ∼20% variation in community composition in our model. We propose that submesoscale divergence is a plausible contributor to observed taxonomic variability at oceanic fronts, and can lead to regional variability in community composition.

A discrete, stochastic model of colonial phytoplankton population size structure: Development and application to in situ imaging-in-flow cytometer observations of Dinobryon.

The scientific community lacks models for the dynamic changes in population size structure that occur in colonial phytoplankton. This is surprising, as size is a key trait affecting many aspects of phytoplankton ecology, and colonial forms are very common. We aim to fill this gap with a new discrete, stochastic model of dynamic changes in phytoplankton colonies' population size structure. We use the colonial phytoplankton Dinobryon as a proof-of-concept organism. The model includes four stochastic functions-division, stomatocyst production, colony breakage, and colony loss-to determine Dinobryon population size structure and populations counts. Although the functions presented here are tailored to Dinobryon, the model is readily adaptable to represent other colonial taxa. We demonstrate how fitting our model to in situ observations of colony population size structure can provide a powerful approach to explore colony size dynamics. Here, we have (1) collected high-frequency in situ observations of Dinobryon in Lac (Lake) Montjoie (Quebec, Canada) in 2013 with a moored Imaging FlowCytobot (IFCB) and (2) fit the model to those observations with a genetic algorithm solver that extracts parameter estimates for each of the four stochastic functions. As an example of the power of this model-data integration, we also highlight ecological insights into Dinobryon colony size and stomatocyst production. The Dinobryon population was enriched in larger, flagellate-rich colonies near bloom initiation and shifted to smaller and emptier colonies toward bloom decline.

Predicting the impacts of environmental variability on phytoplankton communities of a sub-tropical estuary

Phytoplankton are the floating microscopic organisms which form the base of aquatic food chain, and their ecology is controlled by biotic and abiotic variables. However, a little is known about the response of phytoplankton to changed environmental conditions especially in the sub-tropical regions. Therefore, this study aimed to understand the response of phytoplankton community in variable temperature and salinity conditions in the Naf River estuary of Bangladesh. Phytoplankton, temperature and salinity data were collected from the Naf River estuary of Bangladesh from February 2022 to December 2022. Predicted data of temperature and salinity under two climate change scenarios were also gathered from a hydrodynamic model. Response of phytoplankton to different temperature and salinity scenarios were then analyzed by using a logistic model. This study identified about 154 phytoplankton species from the study area. Temperature had significant negative impacts on the 50 phytoplankton species while 83% species were correlated to the change in salinity. About four phytoplankton species disappeared under the changed environmental conditions. Abundance of one species significantly reduced (50% reduction) while environmental conditions were changed. About 18 phytoplankton species responded positively to the changed environmental conditions. This study provides necessary insights to understand the consequences of climate change on phytoplankton ecology in the sub-tropical ecosystems.

Underwater Binocular Meta-lens

Underwater optics in all-aquatic environments is vital for environmental management, biogeochemistry, phytoplankton ecology, benthic processes, global change, etc. Many optical techniques of observational systems for underwater sensing, imaging, and applications have been developed. For the demands of compact, miniaturized, portable, lightweight, and low-energy consumption, a novel underwater binocular depth-sensing and imaging meta-optic device is developed and reported here. A GaN binocular meta-lens is specifically designed and fabricated to demonstrate underwater stereo vision and depth sensing. The diameter of each meta-lens is 2.6 mm, and the measured distance between the two meta-lens centers is 4.04 mm. The advantage of our binocular meta-lens is no need of distortion correction or camera calibration, which is necessary for traditional two-camera stereo vision systems. Based on the experimental results, we developed the generalized depth calculation formula for all-size binocular vision systems. With deep-learning support, this stereo vision system can realize the fast underwater object’s depth and image computation for real-time processing capability. Our artificial intelligent imaging results show that depth measurement accuracy is down to 50 μm. Besides the aberration-free advantage of flat meta-optic components, the intrinsic superhydrophobicity properties of our nanostructured GaN meta-lens enable an antiadhesion, stain-resistant, and self-cleaning novel underwater imaging device. This stereo vision binocular meta-lens will significantly benefit underwater micro/nanorobots, autonomous submarines, machine vision in the ocean, marine ecological surveys, etc.

Tropical cyclones: what are their impacts on phytoplankton ecology?

Following the passage of a tropical cyclone (TC) the changes in temperature, salinity, nutrient concentration, water clarity, pigments and phytoplankton taxa were assessed at 42 stations from eight sites ranging from the open ocean, through the coastal zone and into estuaries. The impacts of the TC were estimated relative to the long-term average (LTA) conditions as well as before and after the TC. Over all sites the most consistent environmental impacts associated with TCs were an average 41% increase in turbidity, a 13% decline in salinity and a 2% decline in temperature relative to the LTA. In the open ocean, the nutrient concentrations, cyanobacteria and picoeukaryote abundances increased at depths between 100 and 150m for up to 3months following a TC. While at the riverine end of coastal estuaries, the predominate short-term response was a strong decline in salinity and phytoplankton suggesting these impacts were initially dominated by advection. The more intermediate coastal water-bodies generally experienced declines in salinity, significant reductions in water clarity, plus significant increases in nutrient concentrations and phytoplankton abundance. These intermediate waters typically developed dinoflagellate, diatom or cryptophyte blooms that elevated phytoplankton biomass for 1-3months following a TC.

Methodological 'lenses' influence the characterization of phytoplankton dynamics in a coastal upwelling ecosystem.

New technologies enable the opportunity to improve our monitoring and understanding of marine phytoplankton communities. However, careful consideration for how different methodological approaches, or 'lenses', influence our interpretation of phytoplankton ecology is important, particularly when drawing conclusions about change over time or space. Using both high-throughput 18S rRNA gene sequencing and microscopy, we explored how phytoplankton community structure varied over the course of a year within a nearshore semi-enclosed coastal embayment along the Central Coast of California. The seasonal shift in the relative community dominance (i.e., diatom vs. dinoflagellate dominance) was captured in the microscopy results but not effectively captured in the molecular-based findings. However, the molecular approach explained more of the variability in composition across seasons relative to the microscopy approach. Temporal dynamics of specific bloom-forming taxa also differed between the molecular and microscopy results. Overall, the observed differences between the molecular- and microscopy-derived characterization of phytoplankton dynamics suggest that the approaches are best suited to answer different research questions. Moreover, the approaches complement each other for a more comprehensive perspective of a coastal phytoplankton ecosystem. Therefore, identifying the biases of each approach within natural communities is necessary to effectively and accurately characterize phytoplankton communities.

A Snapshot on the Distribution of Coastal Phytoplankton Communities in Five HAB-Affected Bays in Eastern Visayas, Philippines

In recent years, harmful algal blooms (HABs), commonly known as red tide, have started to occur year-round in the warm tropical marine waters of Eastern Visayas, Philippines. These are a threat to public safety and cause enormous loss in industries relying on marine resources. The first step in solving this problem is to establish the distribution and succession of phytoplankton communities and harmful microalgae that exist in the region. For the first time, simultaneous monthly monitoring of the phytoplankton community was conducted in five HAB-affected bays of Leyte and Samar islands. We observed spatial differences on the environmental profiles between the five bays in the two islands and these differences may, in part, influence the distribution and abundance of the phytoplankton community residing within these areas. Diatom associated groups were prevalent in all sampling sites, however, HAB causative species were abundant in the bays in Samar during the sampling period. Five (5) genera and nine (9) species that may cause HAB were identified in all five bays. These are potential vectors for paralytic shellfish poisoning, amnesic shellfish poisoning, diarrhetic shellfish poisoning, and fish kill due to hypoxia. The correlation analysis confirmed that the majority of potential HAB vectors correlated with temperature, dissolved oxygen, rainfall, nitrate, and phosphate. The abundance of Pyrodinium bahamense observed in October to November in Samar coincided with several red tide alerts announced by the region’s fishery agency. This however, was never observed to dominate the phytoplankton community. Instead, the following diatoms dominated the five bays; Skeletonema, Pseudo-nitzschia, Bacteriastrum, Chaetoceros, Rhizosolenia and Thalassionema. This is a pioneering study that shows a simultaneous snapshot on the community structure and environmental profiles in these five bays in Eastern Visayas in 2020–2021. It discusses the effects of mariculture to its phytoplankton community and vice versa. Relationships between different phytoplankton species were further observed. This contributes to the knowledge of phytoplankton ecology in warm waters which is necessary to understand future phytoplankton ecosystems affected by sea temperature rise due to climate change.

Application of multiple indices to the evaluation of trophic and ecological status in a tropical macrotidal estuary (Equatorial Margin, Brazil)

ABSTRACT The Paciência river estuary (PRE) is an Amazonian estuary with relevant socio-economic importance; however, it is undergoing a continuous anthropogenic pressure such as the input of untreated domestic effluents. Hence, the phytoplankton community and trophic indices were analysed during three seasons in 2017 to assess the water quality and understand the degree of human influence in a macrotidal estuary. The trophic state of the PRE was determined by applying the trophic state index (TSI), trophic index, and Karydis trophic index, and ecological status by diversity metrics (diversity, evenness, richness, and dominance). Multivariate analysis indicated that TSI and dominance index were the most sensitive indices to changes in environmental conditions. The precipitation regime characterised the estuary in two different trophic scenarios. PRE was hypereutrophic in the dry season and mesotrophic in the rainy/transitional seasons based on the TSI. A high dominance index was recorded in the dry season with blooms of Thalassiosira rotula, reflecting an ecological disturbance. A higher phytoplankton diversity was recorded in the rainy/transitional seasons, indicating a tendency toward a lower stressed ecosystem. Therefore, understanding the trophic state variability in tropical estuaries and its response to changes in phytoplankton ecology is essential to support the management of coastal ecosystems.

长山群岛海域真核微藻粒级结构及扇贝摄食选择性

PDF HTML阅读 XML下载 导出引用 引用提醒 长山群岛海域真核微藻粒级结构及扇贝摄食选择性 DOI: 10.5846/stxb202105191311 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 辽宁省‘兴辽英才计划’项目（XLYC1907109）；大连市杰出青年科技人才项目（2019RJ09）；现代农业体系建设专项（CARS-49） Particle size structure of eukaryotic microalgae and feeding selectivity of scallops in the waters of Changshan Islands Author: Affiliation: Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:采用高通量测序-分子鉴定分级技术于2019年对长山群岛全海域真核微藻粒级结构进行了研究。结果发现，春季以中（47%）、小粒级（41%）为主，夏季以小（39%）、大粒级（38%）为主，秋季以大粒级（60%）为主，春、夏、秋季小、中、大粒级微藻比例为42：47：11、39：23：38、22：18：60。小粒级微藻优势种为细小微胞藻（Micromonas pusilla）、融合微胞藻（Micromonas commoda）和金牛微球藻（Ostreococcus tauri），中粒级微藻优势种为剧毒卡尔藻（Karlodinium veneficum）、大粒级微藻优势种为柔弱几内亚藻（Guinardia delicatula）、平野亚历山大藻（Alexandrium hiranoi）、多纹膝沟藻（Gonyaulax polygramma），综合整个真核微藻群落，春季由中粒径的剧毒卡尔藻占据优势（23.9%），夏季由大粒径的平野亚历山大藻占据优势（29.4%），秋季由大粒径的多纹膝沟藻占据优势（66.8%），有毒甲藻在该海域中占有绝对优势，贝毒累积风险较高，小粒径微藻中金牛微球藻和抑食金球藻曾在渤海引发褐潮，潜在威胁该海域贝类养殖业。虾夷扇贝对小粒级和大粒级微藻的选择性较低，对中粒级微藻的选择性较高，尤其对水体中优势种剧毒卡尔藻一直表现出主动选择。光学需氧量、无机氮、溶解氧、石油类及部分重金属Cd、As、Hg影响着整个长山群岛海域真核微藻粒级结构时空演变。 Abstract:The Chang-shan Archipelago is the largest island group in the northern waters of the Yellow Sea. It significantly contributes to local economic development due to its abundant aquatic products. In recent years, economically important shellfish (scallops, oysters, and clams) have exhibited growth retardation, thinning, and increased mortality, which has affected the sustainable and healthy development of fisheries. Marine microalgae are the dominant food source for filter-feeding shellfish; they differ in size, physiological functions, and sedimentation rates, which greatly influence the regional ecosystem food web.The microalgae size-fractions are closely related to the nutrient reserves and healthy growth of filter-feeding shellfish.High-throughput sequencing technology can reveal highly diverse eukaryotic lineages, while significantly reducing the errors associated with species identification, particularly microalgae. Importantly, the microalgae composition can be ascertained at multiple taxonomic levels, including at the species level. However, some questions still remain regarding their quantitative estimates. As the number of rDNA copies varies widely among different eukaryotes, it is difficult to determine the abundance of eukaryotic microalgae from rDNA CN-based inferences in environmental samples. However, related studies have demonstrated a significant positive correlation between rDNA sequence polymorphisms and rDNA copy numbersrate. When the size of the cell varies in a population, the rRNA/rDNA quantity reflects the biomass of that population. In this study, the proportion of rDNA copy numbers of eukaryotic microalgae was used to characterize their size distribution (the proportion of pico-, nano-, and microphytoplankton).In aquatic ecosystems, the factors controlling phytoplankton production and their seasonal successions are the main items of phytoplankton ecology. Several factors are linked to the growth and size-fraction structure of phytoplankton, such as the availability of light, temperature, nutrients, competition, and parasitism.Therefore, phytoplankton structure can be considered an integrator of environmental factors.In this study, we used the high-throughput sequencing method to assess the size-fraction structure of phytoplankton as well as the controlling environmental factors around the Changshan Islands. It showed that the proportion of pico-, nano-, and microphytoplankton was 42:47:39 in spring, 39:23:38 in summer, and 22:18:60 in autumn.Micromonas pusilla, Micromonas commoda, and Ostreococcus tauri were the dominant picophytoplankton; Karlodinium veneficum was the dominant nanophytoplankton; and Guinardia delicatula, Alexandrium hiranoi, and Gonyaulax polygramma were the dominant microphytoplankton around the Changshan Archipelago. Moreover, Karlodinium veneficum, Alexandrium hiranoi, and Gonyaulax polygramma were the dominant species in spring, summer, and autumn, respectively. The Mizuhopecten yessoensis selectivity to small and large microalgae was low, while the selectivity to medium microalgae was high, especially to Karlodinium veneficum, the dominant species in water. Environmental factors such as COD(chemical oxygen demand), DIN(dissolved inorganic nitrogen), DO(dissolved oxygen), Oil, Cd, As, and Hg were significantly related to the growth and size-fraction structure of phytoplankton. In the three seasons, Cd and COD were significantly related to the growth of picophytoplankton biomass; DO, DIN, and Oil were significantly related to the growth of picophytoplankton biomass; and COD, As, and Hg were significantly related to the growth of picophytoplankton biomass. 参考文献 相似文献 引证文献