Phytoplankton Succession Research Articles

Iron Limitation and Uneven Grazing Pressure on Phytoplankton Co‐Lead the Seasonal Species Succession in the Ross Ice Shelf Polynya

AbstractThe seasonal species succession of phytoplankton from Phaeocystis antarctica to diatoms in the Ross Ice Shelf Polynya (RISP) plays a fundamental role in food webs and ecosystem functioning. Previous studies have revealed that this seasonal succession is affected by differences in light, iron demand, aggregation, and subsequent sinking between these two taxa. This study further investigated the dominant process of species succession by analyzing the results of a bulk mixed‐layer ecosystem model. The mechanism of processes leading to the replacement by diatoms differs from that for triggering the initial P. antarctica bloom. Light triggered the spring bloom dominated by P. antarctica in iron‐rich surface water, which is resupplied by winter convective mixing from the lower layer pool. After reaching its maximum in mid‐November, the biomass of P. antarctica declined progressively due to the severe iron limitation. Seasonal species succession can be enhanced by a small amount of predation on P. antarctica by microzooplankton. The long‐term iron enrichment promotes the transition by supporting diatom growth. The balance between bottom‐up and top‐down processes plays a critical role in shaping the phytoplankton composition and promoting the seasonal species succession in the iron‐limited upper mixed layer of the RISP.

Seasonal measurements of the nitrogenous osmolyte glycine betaine in marine temperate coastal waters

Glycine betaine (GBT) is a nitrogenous osmolyte ubiquitous throughout the marine environment. Despite its widespread occurrence and significance in microbial cycling, knowledge of the seasonality of this compound is lacking. Here, we present a seasonal dataset of GBT concentrations in marine suspended particulate material. Analysing coastal waters in the Western English Channel, GBT peaked in summer and autumn but did not follow the observed maxima in total phytoplankton biomass or chlorophyll a. Instead, we found evidence that GBT concentrations were associated with specific phytoplankton groups or species, particularly in the summer when GBT correlated with dinoflagellate biomass. In contrast, autumn maxima corresponded with a period of rapidly changing salinity and nutrient availability, with potential contributions from some phytoplankton species and Harpacticoid copepods. This suggests distinct environmental drivers for different periods of the GBT seasonality. Building on evidence that GBT and dinoflagellate biomass peak in summer, concomitantly with low nutrients, we propose that GBT positively affects dinoflagellate fitness, allowing them to outcompete other plankton when inorganic nutrients are depleted. By using this assumption, we improved the performance of a marine ecosystem model to reproduce the observed increase in dinoflagellates biomass in the transition from spring to summer. This work sheds light on the interplay between phytoplankton succession, competitive advantage and changing environmental factors relevant to climate change. It paves the way for future multidisciplinary research aiming to understand the importance of dinoflagellates in key coastal ecosystems and their potential significance for methylamine production, compounds relevant for particle growth in atmospheric chemistry.

Upwelled plankton community modulates surface bloom succession and nutrient availability in a natural plankton assemblage

Abstract. Upwelling of nutrient-rich waters into the sunlit surface layer of the ocean supports high primary productivity in eastern boundary upwelling systems (EBUSs). However, subsurface waters contain not only macronutrients (N, P, Si) but also micronutrients, organic matter and seed microbial communities that may modify the response to macronutrient inputs via upwelling. These additional factors are often neglected when investigating upwelling impacts on surface ocean productivity. Here, we investigated how different components of upwelled water (macronutrients, organic nutrients and seed communities) drive the response of surface plankton communities to upwelling in the Peruvian coastal zone. Results from our short-term (10 d) study show that the most influential drivers in upwelled deep water are (1) the ratio of inorganic nutrients (NOx : PO43-) and (2) the microbial community present that can seed heterogeneity in phytoplankton succession and modify the stoichiometry of residual inorganic nutrients after phytoplankton blooms. Hence, this study suggests that phytoplankton succession after upwelling is modified by factors other than the physical supply of inorganic nutrients. This would likely affect trophic transfer and overall productivity in these highly fertile marine ecosystems.

A two‐dimensional morphospace for cyanobacteria and microalgae: Morphological diversity, evolutionary relatedness, and size constraints

Abstract Body metrics are considered as master traits that regulate physiological, behavioural and life history features of planktic cyanobacteria and microalgae. Although the distribution of their morphological traits reflects the various trade‐offs and strategies needed for survival in pelagic habitats, previous methods for quantifying phytoplankton body shape do not adequately represent the intricate details of surface variation that are so important for their nutrient‐ and light‐harvesting capabilities. Therefore, here we provide a new framework to quantify and illustrate the morphological diversity of cyanobacteria and microalgae. Essential components of formulae used for surface area (A = Cs × d2) and volume (V = Cv × d3) calculations are provided by the shape‐specific surface area and volume constants (Cs, Cv). Cs, the surface shape factor, characterises the coarseness of the object surface, and Cv, the volumetric shape factor, characterises the shape deviation from a sphere. Using these morphologically and biologically relevant variables, we defined a two‐dimensional morphological space, in which all three‐dimensional objects have well‐defined positions. By analysing morphologies of taxa representing various forms in major cyanobacterial and microalgal groups, we demonstrated that these groups show considerable differences in the area occupied within the morphospace and these differences are not affected by evolutionary relatedness. We showed that the ratio of surface and volume constants correlated with organism size, suggesting that the development of basic morphologies is constrained by their linear dimensions. Using surface and volumetric shape factors, we created a two‐dimensional Euclidean morphospace in which all three‐dimensional objects have a specific position. Positioning uni‐ and multicellular cyanobacteria and microalgae of various shapes into this morphospace allows their geometrical and ecological limitations to be understood. Because of the close linkage between phytoplankton morphology and ecology, the proposed morphospace may serve as a proxy for an ecospace. Thus, in future the proposed morphospace can be used to visualise current ecological processes such as eutrophication or seasonal succession of phytoplankton.

Declining metal availability in the Mesozoic seawater reflected in phytoplankton succession

Variable trace metal concentrations in the Precambrian ocean were closely linked to oxygen availability, although less is known about the drivers of seawater trace metal chemistry after the spread of complex life into the Phanerozoic eon. A major phytoplankton succession took place at the transition from the Palaeozoic to the Mesozoic era (~250 Myr ago), from an ocean dominated by the green Archaeplastida to secondary endosymbiotic algae with red-algal-derived plastids. Here, our comparative genomic analysis of 26 complete proteomes and metal domain analysis of additional 608 partially complete sequences of phytoplankton reveal that groups with different evolutionary history have distinct metal-binding proteins and contrasting metal acquisition strategies, adapted to differing availability of trace metals. The secondary-endosymbiont-bearing lineages are better adapted to well-oxygenated, nutrient-poor environments. This is supported by an enhanced thiol-based binding affinity of their transporters, coupled with minimized proteomic requirement for trace elements such as iron, copper and zinc at both protein and domain levels. Such different metal requirements across these lineages suggest a drastic decline in open-ocean trace metal concentrations at the inception of the Mesozoic, contributing to the shifts in phytoplankton communities that drove major changes in ocean chemical buffering.

Stochastic and Deterministic Processes Regulate Phytoplankton Assemblages in a Temperate Coastal Ecosystem.

Assessing the relative contributions of the interacting deterministic and stochastic ecological processes for phytoplankton community assembly is crucial in understanding and predicting community organization and succession at different temporal and spatial scales. In this study, we hypothesized that deterministic and stochastic ecological processes regulating phytoplankton, present seasonal and repeating patterns. This hypothesis was explored during a 5-year survey (287 samples) conducted at a small spatial scale (~15km) in a temperate coastal ecosystem (eastern English Channel). Microscopy and flow cytometry quantified phytoplankton abundance and biomass, while metabarcoding data allowed an extended evaluation of diversity and the exploration of the ecological processes regulating phytoplankton using null model analysis. Alpha diversity of phytoplankton was governed by the effect of environmental conditions (environmental filtering). Temporal community turnover (beta diversity) evidenced a consistent interannual pattern that determined the phytoplankton seasonal structure. In winter and early spring (from January to March), determinism (homogeneous selection) was the major process in the phytoplankton community assembly. The overall mean in the year was 38%. Stochastic processes (ecological drift) prevailed during the rest of the year from April to December, where the overall mean for the year was 55%. The maximum values were recorded in late spring and summer, which often presented recurrent and transient monospecific phytoplankton peaks. Overall, the prevalence of stochastic processes rendered less predictable seasonal dynamics of phytoplankton communities to future environmental change. IMPORTANCE While ecological deterministic processes are conducive to modeling, stochastic ones are far less predictable. Understanding the overall assembly processes of phytoplankton is critical in tracking and predicting future changes. The novelty of this study was that it addressed a long-posed question, on a pluriannual scale. Was seasonal phytoplankton succession influenced by deterministic processes (e.g., abiotic environment) or by stochastic ones (e.g., dispersal, or ecological drift)? Our results provided strong support for a seasonal and repeating pattern with stochastic processes (drift) prevailing during most of the year and periods with monospecific phytoplankton peaks.

Phytoplankton Community in Relation to Environmental Variables in the Tidal Mangrove Creeks of the Pasur River Estuary, Bangladesh

The Pasur River estuary (PRE) provides vital fishery resources and supports millions of livelihoods in the southwestern coastal region of Bangladesh. Our research focused on phytoplankton community assemblages, alpha diversity indices, and the seasonal succession of major phytoplankton species in relation to physicochemical parameters in the tidal mangrove creeks of the Pasur River estuary. Spatial and temporal variations were assessed by water sampling at 17 stations in the study area from January to December 2019. The mean salinity level in the tidal mangrove creeks of the PRE was significantly (p < 0.05) higher during the dry season than during the wet season. Spatially, no significant variation (p > 0.05) was observed in the dissolved inorganic nitrogen and dissolved inorganic phosphorus between PRE and mangrove creeks, but temporally, the variables varied significantly (p < 0.05). Spatially, no significant variation (p > 0.05) was observed in the alpha diversity of the phytoplankton community but significantly (p < 0.05) varied temporally. Blue-green algae became dominant in the oligohaline conditions during the wet season, while diatoms were dominant during the dry season which severely depleted dissolved silica. In terms of phytoplankton species diversity, our study classifies the study areas as highly diversified zones. Phytoplankton succession from diatoms (dry season) to blue-green algae (wet season) is attributed to the changes in the physicochemical and nutrient parameters depending on seasonal environmental parameter fluctuations. This study illustrated that phytoplankton diversity and density varied with the degrees of habitat and seasonal changes, implying the potential impacts of anthropogenic activities and natural causes on their community structure in tropical estuaries and mangrove creeks.

Phytoplankton succession phenology trends in the backwaters of the three gorges reservoir in China and their drivers: Results from satellite observations

Information on long-term phytoplankton phenology trends is critical for clarifying the responses of aquatic ecosystems to environmental perturbations. However, the trends in the phenological metrics of phytoplankton blooms have not yet been comprehensively investigated in river systems with complex hydrodynamic conditions and typical phytoplankton community succession characteristics. Here, we investigated long-term phytoplankton phenology trends in the four typical backwaters of the Three Gorges Reservoir in China as well as the driving factors of these trends between 2009 and 2020 using in situ and satellite observations. The phenological metrics, including the initiation, succession, and termination dates of phytoplankton blooms, were extracted from satellite imagery times series. We found that the phytoplankton bloom and green algal bloom durations have significantly increased, while the durations of cyanobacterial blooms have decreased since 2009. Specifically, the initiation (of cyanobacterial blooms) and first succession (from cyanobacterial blooms to green algal blooms) dates were advanced by 9.75 d and 23.25 d, respectively. However, the second succession (from green algal blooms to cyanobacterial blooms) and termination (of cyanobacterial blooms) dates were delayed by 24.25 d and 13.5 d, respectively. We revealed that air temperature and water level changes were likely responsible for these trends (mean relative contribution = 75.1 ± 6.1 %). These findings provide new insights into regional climatic change and reservoir environmental management and can help researchers address harmful phytoplankton blooms and their associated adverse effects.

Recent Changes of Phytoplankton Bloom Phenology in the Northern High‐Latitude Oceans (2003–2020)

AbstractEighteen years (2003–2020) of data on remotely‐sensed ocean color in high northern latitudes show a significant increase (0.56% yr−1) in double blooms of phytoplankton. Starting in 2015 the rate of increase rose to 1.10% yr−1. Double blooms have become especially prevalent in regions north of 50°N in the North Atlantic, Gulf of Alaska and southern Chukchi Sea. Our correlation analysis suggests that double bloom occurrences are dependent on latitude and seasonal changes in both sea surface temperature (SST) and mixed layer depth (MLD), particularly in the subpolar North Pacific (SNP) and polar oceans (65°–75°N), although we cannot attribute the increased double blooms to specific causes. Single blooms indicated by Chlorophyll a (Chl a) dominate in subpolar‐polar waters and occur close to the timing of the Particulate Inorganic Carbon (PIC) peak (i.e., June–August). In the SNP single bloom, Chl a peaks occur earlier than PIC peaks. This interval was shorter during 2016–2020, which is associated with warming anomalies. In the southern part of the Chukchi Sea, however, we found that PIC peaks occur earlier than Chl a peaks, suggesting a potentially different succession pattern between calcifiers and other functional groups. We speculate that in the near future double blooms of phytoplankton will become a prevalent feature in high‐latitude oceans with concurrent changes in the timing of blooms and seasonal phytoplankton succession in the surface ocean due to climate change.

Diel light cycles affect phytoplankton competition in the global ocean

AbstractAimLight, essential for photosynthesis, is present in two periodic cycles in nature: seasonal and diel. Although seasonality of light is typically resolved in ocean biogeochemical–ecosystem models because of its significance for seasonal succession and biogeography of phytoplankton, the diel light cycle is generally not resolved. The goal of this study is to demonstrate the impact of diel light cycles on phytoplankton competition and biogeography in the global ocean.LocationGlobal ocean.Major taxa studiedPhytoplankton.MethodsWe use a three‐dimensional global ocean model and compare simulations of high temporal resolution with and without diel light cycles. The model simulates 15 phytoplankton types with different cell sizes, encompassing two broad ecological strategies: small cells with high nutrient affinity (gleaners) and larger cells with high maximal growth rate (opportunists). Both are grazed by zooplankton and limited by nitrogen, phosphorus and iron.ResultsSimulations show that diel cycles of light induce diel cycles in limiting nutrients in the global ocean. Diel nutrient cycles are associated with higher concentrations of limiting nutrients, by 100% at low latitudes (−40° to 40°), a process that increases the relative abundance of opportunists over gleaners. Size classes with the highest maximal growth rates from both gleaner and opportunist groups are favoured by diel light cycles. This mechanism weakens as latitude increases, because the effects of the seasonal cycle dominate over those of the diel cycle.Main conclusionsUnderstanding the mechanisms that govern phytoplankton biogeography is crucial for predicting ocean ecosystem functioning and biogeochemical cycles. We show that the diel light cycle has a significant impact on phytoplankton competition and biogeography, indicating the need for understanding the role of diel processes in shaping macroecological patterns in the global ocean.

Biological-physical processes regulate autumn prey availability of spiny icefish Chaenodraco wilsoni in the Bransfield Strait, Antarctic.

This study examines the adaptability of a Southern Ocean predator, which is dependent on Antarctic krill (Euphausia superba), to potential changes in food availability. Muscle fatty acids (FAs) of the spiny icefish Chaenodraco wilsoni collected from three areas in the Bransfield Strait (BS), northern Antarctic Peninsula during February-April 2016 give a good representation of their feeding variability. The compositions of 22:6n3 (DHA) and 20:5n3 (EPA) were both higher in the Transitional Zonal Water with Bellingshausen influence (TBW)-controlled C. wilsoni than in the Transitional Zonal Water with Weddell Sea influence (TWW)-controlled fish. This was positively correlated with photoadaptation and carbon sequestration in TBW-controlled phytoplankton. Results for the FAs 16:1n7, 16:0, DHA and EPA indicate the presence of dinoflagellates in all three areas, suggesting that during late summer and early fall, there is a seasonal phytoplankton succession, where small phytoplankton become dominant, in the BS. In addition, the compositions of some long-chain FAs (>20, such as 20:0, 20:1, 22:0 and 22:1n9) and ∑18 indicated that the food chain based on flagellates and copepods was more apparent in TWW-controlled C. wilsoni, especially the effect of El Niño-Southern Oscillation (ENSO) on the variation of prey communities in TWW-controlled areas. FA markers such as SFA/(PUFA+MUFA), ∑15 + ∑17 and ARA were more pronounced in TWW-controlled C. wilsoni, indicating a more strongly carnivorous and benthic food source. In the TBW-TWW confluence, the complex hydrological structure, including the presence of a large number of mesoscale eddies, allows rich nutrients and krill larvae to remain in it, providing a rich food source for the C. wilsoni. Overall, the FA data of this study show that the diet of C. wilsoni varies in different marine environments, aiding their survivability at the face of climate change.

Length, width, shape regularity, and chain structure: time series analysis of phytoplankton morphology from imagery.

Functional traits are increasingly used to assess changes in phytoplankton community structure and to link individual characteristics to ecosystem functioning. However, they are usually inferred from taxonomic identification or manually measured for each organism, both time consuming approaches. Instead, we focus on high throughput imaging to describe the main temporal variations of morphological changes of phytoplankton in Narragansett Bay, a coastal time‐series station. We analyzed a 2‐yr dataset of morphological features automatically extracted from continuous imaging of individual phytoplankton images (~ 105 million images collected by an Imaging FlowCytobot). We identified synthetic morphological traits using multivariate analysis and revealed that morphological variations were mainly due to changes in length, width, shape regularity, and chain structure. Morphological changes were especially important in winter with successive peaks of larger cells with increasing complexity and chains more clearly connected. Small nanophytoplankton were present year‐round and constituted the base of the community, especially apparent during the transitions between diatom blooms. High inter‐annual variability was also observed. On a weekly timescale, increases in light were associated with more clearly connected chains while more complex shapes occurred at lower nitrogen concentrations. On an hourly timescale, temperature was the determinant variable constraining cell morphology, with a general negative influence on length and a positive one on width, shape regularity, and chain structure. These first insights into the phytoplankton morphology of Narragansett Bay highlight the possible morphological traits driving the phytoplankton succession in response to light, temperature, and nutrient changes.

Highly-resolved interannual phytoplankton community dynamics of the coastal Northwest Atlantic

Microbial observatories can track phytoplankton at frequencies that resolve monthly, seasonal, and multiyear trends in environmental change from short-lived events. Using 4-years of weekly flow cytometry along with chloroplast and cyanobacterial 16S rRNA gene sequence data from a time-series station in the coastal Northwest Atlantic (Bedford Basin, Nova Scotia, Canada), we analyzed temporal observations for globally-relevant genera (e.g., Bolidomonas, Teleaulax, Minidiscus, Chaetoceros, Synechococcus, and Phaeocystis) in an oceanic region that has been recognized as a likely hotspot for phytoplankton diversity. Contemporaneous Scotian Shelf data also collected during our study established that the major phytoplankton within the Bedford Basin were important in the Scotian Shelf during spring and fall, therefore pointing to their broader significance within the coastal Northwest Atlantic (NWA). Temporal trends revealed a subset of indicator taxa along with their DNA signatures (e.g., Eutreptiella and Synechococcus), whose distribution patterns make them essential for timely detection of environmentally-driven shifts in the NWA. High-resolution sampling was key to identifying important community shifts towards smaller phytoplankton under anomalous environmental conditions, while further providing a detailed molecular view of community compositions underpinning general phytoplankton succession within the coastal NWA. Our study demonstrates the importance of accessible coastal time-series sites where high-frequency DNA sampling allows for the detection of shifting baselines in phytoplankton communities.

'Boom-and-busted' dynamics of phytoplankton-virus interactions explain the paradox of the plankton.

Summary Rapid virus proliferation can exert a powerful control on phytoplankton host populations, playing a significant role in marine biogeochemistry and ecology. We explore how marine lytic viruses impact phytoplankton succession, affecting host and nonhost populations.Using an in silico food web we conducted simulation experiments under a range of different abiotic and biotic conditions, exploring virus–host–grazer interactions and manipulating competition, allometry, motility and cyst cycles.Virus‐host and predator–prey interactions, and interactions with competitors, generate bloom dynamics with a pronounced ‘boom‐and‐busted’ dynamic (BBeD) which leads to the suppression of otherwise potentially successful phytoplankton species. The BBeD is less pronounced at low nutrient loading through distancing of phytoplankton hosts, while high sediment loading and high nonhost biomass decrease the abundance of viruses through adsorption. Larger hosts are inherently more distanced, but motility increases virus attack, while cyst cycles promote spatial and temporal distancing.Virus control of phytoplankton bloom development appears more important than virus‐induced termination of those blooms. This affects plankton succession – not only the growth of species infected by the virus, but also those that compete for the same resources and are collectively subjected to common grazer control. The role of viruses in structuring plankton communities via BBeDs can thus provide an explanation for the paradox of the plankton.

Factors determining phytoplankton community growth and succession in the water’s surface of Mediterranean reservoir

Factors determining phytoplankton community growth and succession in the water’s surface of Mediterranean reservoir

Comparative account on phytoplankton functional community dynamics in the Alappuzha mud bank region (southwest coast of India) by HPLC-CHEMTAX and microscopy approaches

Phytoplankton community composition and its temporal dynamics were evaluated in the Alappuzha near shore waters (<15 m depth), including mud bank region, located along the southwest coast of India, using HPLC-derived marker pigments and microscope-based species composition data. The study has shown a characteristic phytoplankton succession pattern, wherein an exceptional increase in chlorophyll a (Chl a, >10 mg m−3), observed in the whole study region during the peak southwest monsoon (SWM - July) period, apparently unveiled the biological manifestation of nutrient enrichments facilitated by the coastal upwelling phenomenon. A conspicuous increase in fucoxanthin (a biomarker for diatoms) perceived across the study region clearly indicated the preponderance of diatoms (mainly Thalassiosira sp., Skeletonema costatum, Trieres mobiliensis, Nitzschia sp. etc.), particularly during the peak SWM period. The CHEMTAX calculations have shown the significant contribution of Chl a (av. 76% of total Chl a) from diatoms, regardless of seasons, compared to other taxonomic groups. Furthermore, the combined results of HPLC-CHEMTAX analyses have demonstrated the seasonal occurrence of various small-sized phytoplankton functional groups (PFGs), specifically cyanobacteria, cryptophytes and chlorophytes, along with the predominant large-sized PFGs, i.e. diatoms (mostly) and dinoflagellates. The relative increase in zeaxanthin prevalent during the warm periods (Pre-SWM and Post SWM) signified the presence of cyanobacteria. By contrast, during the SWM period, a conspicuous increase in Chl b and alloxanthin recorded in the whole study region indicated the abundance of green algae and cryptophytes, respectively. Likewise, a nominal increase in peridinin (a marker for dinoflagellates) prevalent during the onset of SWM was apparently due to the proliferation of dinoflagellates, Tripos furca and Prorocentrum micans (microscopically confirmed). Even though the overall CHEMTAX results clearly complemented the microscopy derived phytoplankton composition data, especially the abundance of large sized PFGs, (i.e. diatoms and dinoflagellates), this particular analysis could enable the portrayal of seasonal dynamics of small-sized PFGs (mainly cyanobacteria and cryptophytes) as well, as this information is highly significant as far as the study region is concerned.

Morphological traits, niche-environment interaction and temporal changes in diatoms

Annual phytoplankton succession is a key ecological phenomenon that drives marine species’ life cycles and energy flows within marine ecosystems. Identifying processes that control annual succession is critical to anticipate climate-induced environmental perturbations of this phenomenon and the consequences upon ecosystem functioning. Here, we demonstrate that diatoms in the North Sea undergo strong morphological changes throughout the year and that species with similar phenology possess comparable morphological traits (e.g. cell elongation) and ecological niches. The spring and autumn periods appear to be dominated by oblates (flattened cells) whereas the summer period is dominated by prolates (elongated cells). Elongation of the cell shape enhances buoyancy and confers a selective advantage in stratified low-nutrient waters typical of summer without changing a diatom’s surface area/volume ratio or its ability to absorb nutrients. Diatom shape thus appears to have evolved as a key adaptation to a specific environment and confers upon a species its specific niche and phenology, and therefore its place in the sequence of annual succession. As a result, shape influences temporal changes in the abundance of diatoms and their putative response to environmental forcing. We suggest that biogeochemical and earth-system models should include diatom cell shape as a parameter in order to improve model predictions and help our understanding of the consequences of climate change on marine ecosystems.

Features of the Seasonal Succession of Phytoplankton in the Crimean Coastal Area (Black Sea) in Years with Different Climatic Conditions (2009-2014)

Features of the Seasonal Succession of Phytoplankton in the Crimean Coastal Area (Black Sea) in Years with Different Climatic Conditions (2009-2014)

Phytoplankton Succession Phenology Trends in the Backwaters of the Three Gorges Reservoir and Their Drivers: Results from Satellite Observations

Phytoplankton Succession Phenology Trends in the Backwaters of the Three Gorges Reservoir and Their Drivers: Results from Satellite Observations

Seasonal dynamics of odor compounds concentration driven by phytoplankton succession in a subtropical drinking water reservoir, southeast China

Occurrences of odor compounds in drinking water reservoirs are considered as a nuisance by the water industry. Through the high-frequency monitoring of Tianmuhu Reservoir, a drinking water source for a city with a population of 700,000, we found that odor compounds seasonal dynamics were significantly related to phytoplankton succession, which was controlled by hydrometeorological process. 2-Methylisoborneol (2-MIB) was significantly related to Aphanizomenon sp. (r = 0.51). When the surface water temperature exceeded 12 ℃, 2-MIB concentration may exceed the odor threshold concentration. With the proliferation of Aphanizomenon sp. in spring, 2-MIB concentration reached 87.22 ng/L. After late spring heavy rain, 2-MIB concentration sharply decreased to 3.19 ng/L. As the temperature increased at the end of the rainy season, Aphanizomenon sp. biomass increased to 2.09 mg/L, and 2-MIB concentration increased to 40.16 ng/L. These results showed that the concentration of odor compounds in shallow layer varied greatly because odor compounds mainly originated from phytoplankton and were susceptible to short-term hydrometeorological processes. However, the concentrations of odor compounds in deep layer were relatively insensitive to short-term weather processes. This study will improve the understanding of seasonal changes in odor compounds at different depths, and provide useful information for reservoir managers to prevent odor problems.