Surface Phytoplankton Community Research Articles

Spatio-temporal variability of surface phytoplankton community structure in relation to different water systems in the east China sea coast

Spatio-temporal variability of surface phytoplankton community structure in relation to different water systems in the east China sea coast

Dynamics of phytoplankton communities in the Baltic Sea: insights from a multi-dimensional analysis of pigment and spectral data—part I, pigment dataset

This study aims to investigate the seasonal and spatial distribution of surface phytoplankton communities in the Baltic Sea, using pigment analysis and hydrological parameters. Data were collected during six oceanographic campaigns between 2005 and 2008, including high-performance liquid chromatography (HPLC) pigment characterization and hydrological measurements. The first part of this comprehensive study was focused on the HPLC phytoplankton pigment dataset in relation to hydrological conditions. The research highlighted the importance of high-quality input data for accurate taxonomic analysis. Several unsupervised machine learning approaches, such as hierarchical cluster analysis (HCA), principal component analysis (PCA), and network-based community detection analysis (NCA), were used to analyze the data and identify phytoplankton communities based on biomarker pigments. Five main phytoplankton communities were identified: diatoms, dinoflagellates, cryptophytes, green algae, and cyanobacteria. The results evidenced distinct seasonal patterns, with diatom blooms dominating in spring, cyanobacterial blooms in mid-summer, and haptophyte and dinoflagellate peaks occurring in late summer and autumn. While PCA and NCA provided consistent insights into community structure, HCA offered less clarity in distinguishing between groups. The results of the statistical analysis were then compared with those of traditional approaches such as CHEMTAX and region-specific bio-optical algorithms, providing new perspectives on the taxonomic composition of phytoplankton groups. This study provides valuable insights into phytoplankton dynamics in the Baltic Sea and the effectiveness of different analytical approaches in understanding community structure, providing metrics that can enhance current and future advancements in remote sensing, including support for hyperspectral ocean color remote sensors.

Organic matter composition in sediments recording sea surface phytoplankton community structure in Prydz Bay of Antarctica

Organic matter composition in sediments recording sea surface phytoplankton community structure in Prydz Bay of Antarctica

Alexandrium on the Alaskan Beaufort Sea shelf: Impact of upwelling in a warming Arctic

Alexandrium on the Alaskan Beaufort Sea shelf: Impact of upwelling in a warming Arctic

Seasonal Compositions of Size-Fractionated Surface Phytoplankton Communities in the Yellow Sea

Little information on the phytoplankton community in the Yellow Sea (YS)—especially size-fractionated phytoplankton—is currently available, in comparison to the various physicochemical studies in the literature. Using high-performance liquid chromatography (HPLC), size-fractionated phytoplankton communities were seasonally investigated in the YS in 2019. In the study period, diatoms (55.0 ± 10.2%) and cryptophytes (16.9 ± 9.3%) were the dominant groups. Due to the recent alteration in inorganic nutrient conditions reported in the YS, the contribution of diatoms was lower than in previous studies. The large-sized phytoplankton group (>20 µm) was dominated mostly by diatoms (89.0 ± 10.6%), while the small-sized phytoplankton group (<20 µm) was also dominated by diatoms (41.9 ± 9.1%), followed by cryptophytes (19.2 ± 9.8%). The contributions of small-sized diatoms (<20 µm) have been overlooked in the past, as they are difficult to detect, but this study confirms significant amounts of small-sized diatoms, accounting for 62.3% of the total diatoms in the YS. This study provides an important background for assessing the seasonal variations in different-sized diatom groups in the YS. Further detailed studies on their potential ecological roles should be conducted, in order to better understand marine ecosystems under future warming scenarios.

Tracing the path of carbon export in the ocean though DNA sequencing of individual sinking particles

Surface phytoplankton communities were linked with the carbon they export into the deep ocean by comparing 18 S rRNA gene sequence communities from surface seawater and individually isolated sinking particles. Particles were collected in sediment traps deployed at locations in the North Pacific subtropical gyre and the California Current. DNA was isolated from individual particles, bulk-collected trap particles, and the surface seawater. The relative sequence abundance of exported phytoplankton taxa in the surface water varied across functional groups and ecosystems. Of the sequences detected in sinking particles, about half were present in large (>300 μm), individually isolated particles and primarily belonged to taxa with small cell sizes (<50 µm). Exported phytoplankton taxa detected only in bulk trap samples, and thus presumably packaged in the smaller sinking size fraction, contained taxa that typically have large cell sizes (>500 μm). The effect of particle degradation on the detectable 18 S rRNA gene community differed across taxa, and differences in community composition among individual particles from the same location largely reflected differences in relative degradation state. Using these data and particle imaging, we present an approach that incorporates genetic diversity into mechanistic models of the ocean’s biological carbon pump, which will lead to better quantification of the ocean’s carbon cycle.

Sea surface phytoplankton community response to nutrient and light changes

The sea surface microlayer (SML) is the boundary layer between the ocean and the atmosphere and plays a unique role in marine biogeochemistry. Phytoplankton communities in this uppermost surface layer are exposed to extreme ultraviolet (UV) radiation and potentially high nutrient supplies. In order to understand the response of SML communities to such contrasting conditions, we conducted experiments at three different sites, the North Sea (open ocean) and two sites, outer and middle fjord, in the Sognefjord, Norway, with differing physical and chemical parameters. We manipulated light, nitrogen (N) and phosphorus (P) supply to natural communities collected from the SML and compared their response to that of the underlying water (ULW) communities at 1-m depth. Phytoplankton communities in both SML and ULW responded significantly to N addition, suggesting the upper 1-m surface phytoplankton communities were N-limited. While phytoplankton growth rates were higher with high N and high light supply, biomass yield was higher under low light conditions and with a combined N and P supply. Furthermore, biomass yield was generally higher in the ULW communities compared to SML communities. Nutrient and light effects on phytoplankton growth rates, particulate organic carbon (POC) and stoichiometry varied with geographical location. Phytoplankton growth rates in both SML and ULW at the open ocean station, the site with highest salinity, did not respond to light changes, whereas the communities in the middle fjord, characterized by high turbidity and low salinity, did experience light limitation. This work on the upper surface phytoplankton communities provides new insights into possible effects of coastal darkening and increases understanding of oceanic biogeochemical cycling.

Eukaryotic Phytoplankton Contributing to a Seasonal Bloom and Carbon Export Revealed by Tracking Sequence Variants in the Western North Pacific.

Greater diversity of eukaryotic phytoplankton than expected has been revealed recently through molecular techniques, but little is known about their temporal dynamics or fate in the open ocean. Here, we examined size-fractionated eukaryotic phytoplankton communities from the surface to abyssopelagic zone (5,000 m) throughout the year, by tracking sequence variants of the 18S rRNA gene in the western subtropical North Pacific. The oceanographic conditions were divided into two periods, stratification and mixing, between which the surface phytoplankton community differed. During the mixing period, the abundance of large phytoplankton (≥3 μm) increased, with diatoms and putative Pseudoscourfieldia marina dominating this fraction. Picophytoplankton (<3 μm) also increased during the mixing period and were dominated by Mamiellophyceae. Taxa belonging to prasinophytes (including Ps. marina and Mamiellophyceae) were observed in the epipelagic zone throughout the year, and thus likely seeded the seasonal bloom that occurred during the mixing period. In contrast, diatoms observed during the mixing period mostly represented taxa unique to that period, including coastal species. Numerical particle backtracking experiments indicated that water masses in the surface layer could be transported from coastal areas to the study site. Gene sequences of coastal diatoms were present in the abyssopelagic zone. Therefore, allochthonous species drove the seasonal bloom and could be transported to deep waters. In the abyssopelagic zone, the relative abundance of Ps. marina in deep waters was similar to or higher than that of diatoms during the mixing period. Among picophytoplankton, Mamiellophyceae made up a significant fraction in the abyssopelagic zone, suggesting that prasinophytes are also involved in carbon export. Our molecular survey showed that these previously overlooked phytoplankton species could contribute significantly to the seasonal bloom and biological pump in the subtropical open ocean.

Optical characterization of marine phytoplankton assemblages within surface waters of the western Arctic Ocean.

An extensive data set of measurements within the Chukchi and Beaufort Seas is used to characterize the optical properties of seawater associated with different phytoplankton communities. Hierarchical cluster analysis of diagnostic pigment concentrations partitioned stations into four distinct surface phytoplankton communities based on taxonomic composition and average cell size. Concurrent optical measurements of spectral absorption and backscattering coefficients and remote‐sensing reflectance were used to characterize the magnitudes and spectral shapes of seawater optical properties associated with each phytoplankton assemblage. The results demonstrate measurable differences among communities in the average spectral shapes of the phytoplankton absorption coefficient. Similar or smaller differences were also observed in the spectral shapes of nonphytoplankton absorption coefficients and the particulate backscattering coefficient. Phytoplankton on average, however, contributed only 25% or less to the total absorption coefficient of seawater. Our analyses indicate that the interplay between the magnitudes and relative contributions of all optically significant constituents generally dampens any influence of varying phytoplankton absorption spectral shapes on the total absorption coefficient, yet there is still a marked discrimination observed in the spectral shape of the ratio of the total backscattering to total absorption coefficient and remote‐sensing reflectance among the phytoplankton assemblages. These spectral variations arise mainly from differences in the bio‐optical environment in which specific communities were found, as opposed to differences in the spectral shapes of phytoplankton optical properties per se. These results suggest potential approaches for the development of algorithms to assess phytoplankton community composition from measurements of seawater optical properties in western Arctic waters.

Habitat Delineation in Highly Variable Marine Environments

The structure of the phytoplankton community in surface waters is the consequence of complex interactions between physical and chemical properties of the upper water column as well as interaction within the general biological community. Understanding the structure of phytoplankton communities is especially challenging in highly variable and dynamic marine environments. A variety of strategies have been employed to delineate marine planktonic habitats, including both biogeochemical and water mass based approaches. These methods have led to fundamental improvements in our understanding of marine phytoplankton distributions, but they are often difficult to apply to systems with physical and chemical properties and forcings that vary greatly over relatively short spatial or temporal scales. In this study, we have developed a method of dynamic habitat delineation based on environmental variables that are biologically relevant, that integrate over varying time scales, and that are derived from standard oceanographic measurements. As a result, this approach is widely applicable, simple to implement, and effective in resolving the spatial distribution of phytoplankton communities. As a test of our approach, we have applied it to the Amazon River influenced Western Tropical North Atlantic (WTNA) and to the South China Sea (SCS), which is influenced by both the Mekong River and seasonal coastal upwelling. These two systems differ substantially in their spatial and temporal scales, nutrient sources/sinks, and hydrographic complexity, providing a robust test of the applicability of our analysis. Despite their significant differences in scale and character, our approach generated statistically robust habitat classifications that were clearly relevant to surface phytoplankton communities. Additional analysis of the habitat-defining variables themselves can provide insight into the processes acting to shape phytoplankton communities in each habitat. Finally, by demonstrating the biological relevance of the generated habitats, we gain insights into the conditions promoting the growth of distinct communities and the factors that lead to mismatches between environmental conditions and phytoplankton community structure.

Environmental influence on phytoplankton communities in the northern Benguela ecosystem

An investigation of surface phytoplankton communities was undertaken on the shelf of the northern Benguela upwelling ecosystem during austral autumn (May) and spring (September), along latitudinal transects at 20° S and 23° S, from 2 to 70 nautical miles offshore, as well as on a zigzag grid located between these transects. Microscopic identification of the phytoplankton and CHEMTAX analysis of pigment biomarkers were used to characterise the community composition. During May 2014, warmer, more-saline water with a shallower upper mixed layer corresponding to periods of less-intense offshore Ekman transport was encountered on the shelf. Satellite imagery indicated high phytoplankton biomass extending for a considerable distance from the coast, and CHEMTAX indicated diatoms as dominant at most of the stations (52–92%), although dinoflagellates were dominant at some inshore localities (57–74%). Species of Chaetoceros, Bacteriastrum and Cylindrotheca were the most abundant, with abundance of the Pseudo-nitzschia ‘seriata-group’ being particularly high at a number of stations. In September 2014, more-intense wind-forcing resulted in a deeper upper mixed layer and stronger upwelling of colder, less-saline water. Elevated phytoplankton biomass was confined close to the coast, where diatoms accounted for most of the population (54–87%), whereas small flagellates, such as prasinophytes, haptophytes and cryptophytes, as well as the cyanobacterium Synechococcus, dominated the communities (58–90%) farther from the coast. It is hypothesised that stronger upwelling and deeper vertical mixing in September of that year were not conducive for widespread diatom growth, and that small flagellates populated the water column by being entrained from offshore onto the shelf in the upwelled water that moved in towards the coast.

Variations in Remotely-Sensed Phytoplankton Size Structure of a Cyclonic Eddy in the Southwest Indian Ocean

Phytoplankton size classes were derived from weekly-averaged MODIS Aqua chlorophyll a data over the southwest Indian Ocean in order to assess changes in surface phytoplankton community structure within a cyclonic eddy as it propagated across the Mozambique Basin in 2013. Satellite altimetry was used to identify and track the southwesterly movement of the eddy from its origin off Madagascar in mid-June until mid-October, when it eventually merged with the Agulhas Current along the east coast of South Africa. Nano- and picophytoplankton comprised most of the community in the early phase of the eddy development in June, but nanophytoplankton then dominated in austral winter (July and August). Microphytoplankton was entrained into the eddy by horizontal advection from the southern Madagascar shelf, increasing the proportion of microphytoplankton to 23% when the chlorophyll a levels reached a peak of 0.36 mg·m−3 in the third week of July. Chlorophyll a levels declined to &lt;0.2 mg·m−3 in austral spring (September and October) as the eddy propagated further to the southwest. Picophytoplankton dominated the community during the spring period, accounting for &gt;50% of the population. As far as is known, this is the first study to investigate temporal changes in chlorophyll a and community structure in a cyclonic eddy propagating across an ocean basin in the southwest Indian Ocean.

Impact of Surface Temperature and Salinity on the Ratio of Marine Diatoms to Dinoflagellates in the Trevor Channel Area

In an effort to illuminate the factors that influence surface phytoplankton community composition with respect to marine diatoms (Class Bacillariophyceae) and dinoflagellates (Phylum Dinoflagellata), temperature and salinity data were collected. Phytoplankton samples were collected at six surface water locations along the Trevor channel near Bamfield, British Columbia where sampling locations were of known gradients of salinity and temperature. Each sample was analysed under a light microscope, where 2 µL volumes of seawater were counted for both dinoflagellate and diatom abundances. The ratio of diatoms to dinoflagellates was determined by averaging multiple counts of well-mixed samples from each station. Surface temperature and salinity data were collected using individual CTD (Conductivity, Temperature, Depth) casts, where only the surface values were considered. The phytoplankton ratios were then correlated to each of temperature and salinity. It was found with strong positive correlation that conditions with higher salinity favoured dinoflagellate-dominant communities (r = 0.97, p = 0.00013) and conditions with higher temperature favoured diatom-dominant communities (r = 0.92, p = 0.0035). This data may prove useful in studies regarding how small and large scale climatic changes affect phytoplankton community composition, and proves interesting directions in research as to how bottom-up controls on community structure can impact abundances of macro-organisms.

Atmospheric nutrients in seawater under current and high pCO2 conditions after Saharan dust deposition: Results from three minicosm experiments

Atmospheric nutrients in seawater under current and high pCO2 conditions after Saharan dust deposition: Results from three minicosm experiments

How phytoplankton physiology and community structure adjust to physical forcing in a coastal ecosystem (northern Adriatic Sea)

:We investigated how variability in physicochemical properties influenced photosynthetic parameters and the phytoplankton community in the shallow coastal waters of the Adriatic Sea (Gulf of Trieste), where local rivers greatly influenced the dynamics of the system. During the study period (May 2009–July 2010), high sea-surface temperatures in summer, freshwater inputs and precipitation influenced the stability of the water column and the distribution of major nutrients. Redundancy analysis showed a significant effect of total inorganic nitrogen, silicate and salinity on the distribution of the surface phytoplankton community. The modest chlorophyll a (Chl a) concentration exhibited higher variability [coefficient of variation(C.V.) = 60–69%] compared with the photosynthetic parameters. Among them, photosynthetic capacity (PBmax) showed smallest variation (C.V. =37–45%) and no significant vertical or temporal variability was observed. PBmax significantly correlated with temperature, although indirect control by other environmental factors should not be overlooked. During the stratified period, significant vertical differences were observed in photosynthetic efficiency [αB: 0.009 and 0.014 mg C (mg Chl a)−1 h−1 (μmol photon m−2 s−1)−1 at the surface and 15 m, respectively] and in the light saturation index (Ek: 270 and 172 μmol photon m−2 s−1 at the surface and 15 m, respectively), revealing photoacclimation in the communities. Both parameters also tended to be different in the more homogenous water column during winter. Using a ratio between available light and Ek, this study demonstrated light-limited photosynthesis for the greater proportion of the water column, drawing attention to the vertical variability in αB that could, if disregarded, have a significant effect on the assessment of depth-integrated primary production.

Response of nutrients and the surface phytoplankton community to ice melting in the central Arctic Ocean

During the fourth Chinese National Arctic Research Expedition cruise in summer 2010, a time-seriesobservation was carried out to examine the response of nutrients and phytoplankton community in the ice-waterinterface to the ice melting ice in the central Arctic Ocean. Phosphate and silicate in the ice-water interface wererich relative to dissolved inorganic nitrogen (DIN), based on the Redfield ratio (16N:1P:16Si), suggesting that DINwas the potential limiting nutrient. DIN concentrations in the sea ice were about 3-4 times that in the surfaceseawater, indicating that melting ice delivered DIN to the surface water. Pigment analysis showed that fucoxanthinand chlorophyll a contribute to carotenoids and chlorophylls in particles. The mean concentrations of chlorophyll c ,diatoxanthin, diadinoxanthin and fucoxanthin from 15 August to 18 August were 6 µ g.m-3, 22 µ g.m-3, 73 µ g.m-3and 922 µ g.m-3, respectively, suggesting that diatoms dominated in the phytoplankton community composition.Furthermore, a notable enhancement in fucoxanthin and chlorophyll a during a large-scale ice melting was likelyattributed to senescent diatoms released from the bottom sea-ice as well as phytoplankton diatoms growth in thewater column due to the input of nutrients (i.e., DIN) and reducing light limitation from melting ice. Temporaldistribution patterns of prasinoxanthin and lutein diffred from fucoxanthin, indicating that the response of greenalgae and diatoms to ice melting were different.

Spatial variability in DMSP-lyase activity along an Atlantic meridional transect

In vitro DMSP-lyase activity (DLA) measurements were made during an Atlantic Meridional Transect (AMT) cruise in May 2004, which travelled through the southern and northern oligotrophic gyres. Along the transect, twice-daily measurements were taken from the surface (0.5 − 8.0 m) and the chlorophyll maximum (chl max; 47 − 150 m). Surface samples showed a large variation in DLA (0 − 58.6 nmol L−1 h−1), while values for the chl max were lower and less variable (0 − 8.7 nmol L−1 h−1). A negative correlation was observed between DLA:TChl a and primary production (carbon fixation rate) in surface samples (Spearman’s ρ = −0.57, p < 0.05, n = 17). Nitracline depth and the ratio of photo-protective to photosynthetic accessory pigments indicate that, as expected, surface phytoplankton communities in the gyres experience low nutrient concentrations and high light levels in comparison to communities from the chl max. Comparing pre-dawn and late-morning surface DLA values provides a pseudo time-series for each day and, in areas with elevated DLA, values for the late-morning samples were consistently higher than those taken at pre-dawn. Our field data set covers a geographically extensive area and includes the first DLA analyses from the oligotrophic South Atlantic gyre.

Vertical distribution of aggregates (&gt;110 µm) and mesoscale activity in the northeastern Atlantic: Effects on the deep vertical export of surface carbon

Spatial and temporal variability in the distribution of marine aggregates (&gt;110 mm) was studied using underwater video profilers in an area off the Iberian Peninsula and Azores Islands dominated by mesoscale and submesocale hydrodynamics in winter, spring, and summer 2001. In the 0‐200‐m layer, aggregates were most abundant in spring (100‐120 mg dry weight [dry wt] m‐3) and lowest during summer and winter (1‐10 mg dry wt mm‐3). In the deeper layers (down to 1,000 m), the seasonal pattern was different, with concentrations highest in spring and summer, and lowest in winter (e.g., at 800 m, 5‐10 mg dry wt mm‐3 in spring and summer; 1‐5 mg dry wt mm‐3 in winter). The seasonal change in the abundance of aggregates in the upper 1,000 m was consistent with changes in the composition and intensity of the particulate flux recorded in sediment traps and with seasonal changes in the surface phytoplankton community. In an area dominated by eddies, surface accumulation of aggregates and export down to 1,000 m occur at mesoscale distances (&lt;100 km). The occurrence of a rich aggregate layer may be related to mesoscale activity in water flow that drives nutrient inputs, phytoplankton production, and the formation of large aggregates. Such spatially constrained zones of massive export may be typical of frontal open‐sea systems, and may have been missed by conventional sediment trap moorings, which cannot resolve export at this mesoscale level.

Photophysiology of Surface Phytoplankton Communities in a Transect from the Mouth of the Peene‐Strom to the Arkona Sea (Baltic)

AbstractThe potential of surface phytoplankton to withstand photostress was investigated in August 1998 along a transect from the mouth of the Peene‐Strom (Pomeranian Bight) to the open Arkona Sea (Baltic). Photosynthetic efficiency, algal class composition and pigment pattern were determined. Algae were photoinhibited by artificial illumination and the kinetics of recovery were recorded. Under photoinhibitory treatment, algae from the estuary showed a low effective quantum yield but a high potential to recover their maximum photosynthetic efficiency. Contrary to this, the relatively high effective quantum yield of open sea algae under photoinhibitory treatment is accompanied by a low final recovery of maximum photosynthetic efficiency. These phenomena are discussed with respect to nutrient supply, algal class composition and to different strategies of algae to react to light stress. Literature data of summer primary productivity of open sea and coastal algae are compared with our data on electron transport rates. This revealed a low influence of photoinhibitory effects on productivity.

Strategies of phytoplankton to perform effective photosynthesis in the North Water

Strategies of phytoplankton to perform effective photosynthesis in the North Water