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Plankton size spectra are important indicators of the ecosystem state, yet such measurements are typically biased by the available sampling methods. Here, we combined individual size measurement from two zooplankton imaging approaches— in situ observation by the Underwater Vision Profiler5 and Multinet-collection supplemented by ex situ imaging via Zooscan—obtained in the global ocean, to calculate zooplankton normalized biovolume size spectra (NBSS) for all organisms larger than 1 mm. The reconstructed NBSS combining both datasets resulted in increased biomass estimates by adding organisms poorly sampled by either of the methods. The optimal values measured by both methods are used to reconstruct the zooplankton biovolume and biomass distributions. The reconstructed slopes appeared steeper and closer to those measured only by the UVP5 (+7.6%) and flatter than those obtained only from the Multinet (−20%), particularly in tropical and temperate latitudes. The main difference in tropical and temperate NBSS from the two devices is due to the fragile rhizarians that were not accounted for when using net data. When possible, we suggest using in situ and ex situ technologies together, and we provide potential indications on how to correct for missing components of the community when only one method is available. [ABSTRACT FROM AUTHOR]

Planktons are a fundamental piece of all ocean ecosystems yet, sampling plankton at the high resolution required to understand their dynamics remains a challenge. In-situ imaging tools offer an approach to sample plankton at fine scales. Advances in technology and methodology provide the ability to make in-situ imaging a common tool in plankton ecology. Despite the massive potential of in-situ imaging tools, there are no standard approaches for analyzing the associated data. Consequently, studies are inconsistent in analyzing in-situ imaging data, even for similar questions. This introduces challenges in comparing across studies and sampling devices. In this review, we briefly summarize the increasing use, potential and novel applications of in-situ imaging tools in plankton ecology. Then, we synthesize the common analyses used across these studies. Finally, we address the major statistical challenges associated with the unique sampling mechanisms of in-situ imaging tools and discuss the theoretical uncertainties, which arise from the low-sampling volumes of many in-situ imaging tools. To fully unlock the power of in-situ imaging tools in plankton ecological studies, researchers must carefully consider how to analyze their data. We provide recommendations for processing and analyzing data while also acknowledging a large need for developing new statistical tool. [ABSTRACT FROM AUTHOR]

Eugen Jørgensen, a middle school teacher turned plankton researcher, made significant contributions to the field of plankton research in the early 20th century. His work focused on various groups of marine microplankton, including dinoflagellates, ciliates, and radiolaria. Jørgensen's journey from a non-expert to an authority in the field is outlined in this article, which is based on a memorial biography and his own publications. His 1905 report with Nordgaard is highly cited and influential in radiolarian studies. Jørgensen's career shift from botany to planktonology was not uncommon during that time, as many scientists were captivated by the intriguing world of plankton. [Extracted from the article]

Climate warming causes shorter winters and changes in ice and snow cover in subarctic lakes, highlighting the need to better understand under-ice ecosystem functioning. The plankton community in a subarctic, oligotrophic lake was studied throughout the ice-covered season, focusing on lipid dynamics and life history traits in two actively overwintering copepods, Cyclops scutifer and Eudiaptomus graciloides. Whereas C. scutifer was overwintering in C-IV to C-V stage, E. graciloides reproduced under ice cover. Both species had accumulated lipids prior to ice-on and showed a substantial decrease in total lipid content throughout the ice-covered period: E. graciloides (60%–38% dw) and C. scutifer (73%–33% dw). Polyunsaturated fatty acids of algal origin were highest in E. graciloides and declined strongly in both species. Stearidonic acid (18:4n-3) content in E. graciloides was particularly high and decreased rapidly during the study period by 50%, probably due to reproduction. The copepods differed in feeding behavior, with the omnivore C. scutifer continuing to accumulate lipids until January, whereas the herbivorous E. graciloides accumulated lipids from under-ice primary production during the last months of ice-cover. Our findings emphasize the importance of lipid accumulation and utilization for actively overwintering copepods irrespective of the timing of their reproduction. [ABSTRACT FROM AUTHOR]

Recently, natural and anthropogenic pressures caused an apparent increase in the frequency and spread of red Noctiluca scintillans (RNS) blooms. Here, we describe this potential expansion and the associated environmental factors based on an extensive literature review (1857–2023). Our analysis suggests that Noctiluca increased over time in several Australian, Chinese and European coastal regions. We point to eutrophication, ocean warming and deoxygenation as possible drivers of these intensifications. Moreover, we demonstrate Noctiluca 's importance for coastal ecosystems: with competitive advantages causing fast and intense blooms, Noctiluca has the potential to alter plankton communities, influencing productivity in affected areas. Throughout our analysis, we identified major knowledge gaps that are relevant to assess Noctiluca : (i) challenges in determining its spatiotemporal evolution; (ii) limited knowledge about drivers triggering and ending blooms; (iii) scarce information about feeding, reproduction and interaction in situ and (iv) uncertainty regarding its contribution to carbon export. We hypothesize that these gaps are related to limitations in traditional sampling techniques, and we highlight the need for a holistic approach combining traditional with novel techniques like remote sensing and underwater cameras. Our suggested approach could help filling the identified gaps and facilitate predictions of bloom dynamics and impacts under future climate conditions. [ABSTRACT FROM AUTHOR]

Several species from various zooplankton taxa perform seasonal vertical migrations (SVM) of typically several hundred meters between the surface layer and overwintering depths, particularly in high-latitude regions. We use OPtimality-based PLAnkton (OPPLA) ecosystem model) to simulate SVM behavior in zooplankton in the Labrador Sea. Zooplankton in OPPLA is a generic functional group without life cycle, which facilitates analyzing SVM evolutionary stability and interactions between SVM and the plankton ecosystem. A sensitivity analysis of SVM-related parameters reveals that SVM can amplify the seasonal variations of phytoplankton and zooplankton and enhance the reduction of summer surface nutrient concentrations. SVM is often explained as a strategy to reduce exposure to visual predators during winter. We find that species doing SVM can persist and even dominate the summer-time zooplankton community, even in the presence of Stayers, which have the same traits as the migrators, but do not perform SVM. The advantage of SVM depends strongly on the timing of the seasonal migrations, particularly the day of ascent. The presence of higher (visual) predators tends to suppress the Stayers in our simulations, whereas the SVM strategy can persist in the presence of non-migrating species even without higher predators. [ABSTRACT FROM AUTHOR]

Littoral phytoplankton and zooplankton diversity are influenced by the water quality parameters and their trophic interactions. In the largest reservoir of the Philippines, this study examined the water quality and plankton community composition in the littoral zone across three sampling sites and four depths. Of the three sites, one is located near active fish cages, one near the mouth of a tributary and one near an outlet of an upstream dam. A total of 36 phytoplankton and 34 zooplankton taxa were identified, with most taxa belonging to Chlorophyta and Cyclopoida. The most abundant phytoplankton and zooplankton taxa were Aulacoseira and Microcyclops , respectively. The three most abundant phytoplankton (Aulacoseira , Oscillatoria , Volvox) were most positively correlated with the nutrient levels [total nitrogen (TN), total phosphorus (TP) and TN:TP ratio]. A significant interaction of sampling site and depth was recorded for the phytoplankton's Shannon diversity index and community composition. The decreased zooplankton diversity amidst decreased phytoplankton diversity in the aquaculture site aligns with the effect of lowered resource heterogeneity on zooplankton. The increased phytoplankton diversity and decreased zooplankton density and taxon richness at shallower depths were probably linked with the light availability. [ABSTRACT FROM AUTHOR]

Recent changes in oceanic plankton are being reported at unprecedented rates. Most changes are related to environmental factors, and many were identified as driven by climate, either through natural cycles or by anthropogenic effects. However, the separation of both effects is difficult because of the short length of most observational series. Moreover, some changes are related to trends and cycles, while others were perceived as system shifts, often synchronized over large spatial scales. Here, studies on observational series of plankton, with the focus in the North Atlantic, are reviewed. Two main periods of shifts in plankton assemblages were identified: one in the late 1980s and a more recent one at the beginning of the new millennium. While the origin and extent of most shifts varied locally, their synchronization seems to confirm the response of plankton to changes in warming and in large-scale climatic factors. Changes in species abundance and distribution patterns were generally related to hydrographic factors, but also to non-linear effects of warming, the latter particularly affecting species in regions near the limits of their thermal niches. Indeed, most of the changes were attributed to trade-offs between different biological strategies. Taken together, the reviewed case studies indicate a lagged biological response to variations in the local environment driven by large-scale climate forcing. The challenges for interpreting future shifts include considering local changes within a larger geographical area, variations in species life traits, and potential top-down effects of plankton predators. [ABSTRACT FROM AUTHOR]

The response of plankton communities to short-term climatic events was studied in a narrow coral reef lagoon representative of the channel-type lagoons of the high islands of the tropical Pacific. Phyto- and zooplankton data (abundance and taxonomic composition) were sampled at high frequencies for 2 weeks in April–May 2017 under various tidal conditions and combined with environmental and physical measurements and modeling hydrodynamic products. The short-term external events (wind, waves and rain) that occurred caused changes in the circulation patterns and increased nutrient concentrations in the lagoon. The plankton reacted quickly to this enrichment, with an increase in chlorophyll a and the rapid development of a microphytoplankton community dominated by diatoms, and of opportunistic herbivorous zooplankton (tintinnids, appendicularians). Zooplankton composition and distribution were strongly modulated by the circulation patterns through advection and mixing. Our results show that the tidal and diel components of the temporal variability of planktonic groups were blurred by sporadic event components (i.e. wind, wave and rainfall events). Environmental and biological responses to these external physical forcings occurred at lagoon scale in this channel-like lagoon, unlike what is observed in larger lagoons (such as the southern lagoons of New Caledonia) where spatial variability is much higher. [ABSTRACT FROM AUTHOR]

In highly seasonal systems, the emergence of planktonic resting stages from the sediment is a key driver for bloom timing and plankton community composition. The termination of the resting phase is often linked to environmental cues, but the extent to which recruitment of resting stages is affected by climate change remains largely unknown for coastal environments. Here we investigate phyto- and zooplankton recruitment from oxic sediments in the Baltic Sea in a controlled experiment under proposed temperature and light increase during the spring and summer. We find that emergence of resting stage differs between seasons and the abiotic environment. Phytoplankton recruitment from resting stages were high in spring with significantly higher emergence rates at increased temperature and light levels for dinoflagellate and cyanobacteria than for diatoms, which had highest emergence under cold and dark conditions. In comparison, hatching of copepod nauplii was not affected by increased temperature and light levels. These results show that activation of plankton resting stages are affected to different degrees by increasing temperature and light levels, indicating that climate change affects plankton dynamics through processes related to resting stage termination with potential consequences for bloom timing, community composition and trophic mismatch. [ABSTRACT FROM AUTHOR]

Priscilla Susan Bury, an amateur naturalist and illustrator, published a book in 1862 called "Figures of Remarkable Forms of Polycystins, or allied Organisms, in the Barbados Chalk Deposit." This book was the first of its kind to showcase the beauty of planktonic organisms, specifically radiolarians, through detailed illustrations. Bury sought advice from renowned naturalists and promoted the study of radiolarians through articles and exhibitions. The article also provides a brief overview of the discovery of radiolarians and Bury's personal life. Copies of Bury's book can be found in a few libraries, and electronic versions are available online. [Extracted from the article]

Karlodinium veneficum is type of dinoflagellate plankton present in coastal regions. Harmful algae blooms resulting from uncontrolled growth of K. veneficum often leads to fish kills. They release a toxin named Karlotoxin that is known to affect their prey's bio-locomotion by stunning and slowing them down. We investigate whether the toxin plays a role in aggregating the prey around the a predator, thereby leading to a local increase in prey density. To achieve this, we closely examine the toxin's influence on the prey's probability density distribution with different assumptions on their relative speed in 1D, with either the predator being stationary or swimming at a constant speed. When the predator is stationary, we fully solve the prey's density distribution for all times, and verify the result by a Monte-Carlo simulation. For a swimming predator, we find the steady-state density distribution of prey analytically. When the predator's speed |$s$| is strictly greater (or less) than the prey (⁠|$s-1>0$| or |$s-1<0$|⁠), the results are verified by Monte-Carlo simulations; when their relative speed |$s-1$| has roots, we use the Frobenius method to perform a local analysis for the prey's density at steady state near the roots, and use the result to derive a scheme for finding the analytical solution. This solution is then verified numerically using a finite difference method. When the roots |$x_{1}$| and |$x_{3}$| satisfy |$s^{\prime}(x_{1})<0$| and |$s^{\prime}(x_{3})>0$|⁠ , we show that the probability density for the prey has a form |$|x-x_{1}|^{-s^{\prime}(x_{1})^{-1} -1}$| near the root |$x_{1}$|⁠ , leading to either an integrable singularity or a local maximum. Near the root |$x_{3}$|⁠ , the prey's density can be represented as a Taylor series and is smooth. In most of the cases mentioned above, toxin leads to the aggregation of prey, however the maximum density does not always occur where the toxin has the highest concentration. [ABSTRACT FROM AUTHOR]

Satellite remote sensing is a powerful tool to monitor the global dynamics of marine plankton. Previous research has focused on developing models to predict the size or taxonomic groups of phytoplankton. Here, we present an approach to identify community types from a global plankton network that includes phytoplankton and heterotrophic protists and to predict their biogeography using global satellite observations. Six plankton community types were identified from a co-occurrence network inferred using a novel rDNA 18 S V4 planetary-scale eukaryotic metabarcoding dataset. Machine learning techniques were then applied to construct a model that predicted these community types from satellite data. The model showed an overall 67% accuracy in the prediction of the community types. The prediction using 17 satellite-derived parameters showed better performance than that using only temperature and/or the concentration of chlorophyll a. The constructed model predicted the global spatiotemporal distribution of community types over 19 years. The predicted distributions exhibited strong seasonal changes in community types in the subarctic–subtropical boundary regions, which were consistent with previous field observations. The model also identified the long-term trends in the distribution of community types, which suggested responses to ocean warming. [ABSTRACT FROM AUTHOR]

Pioneers of plankton research: Easter Ellen Cupp (1904-1999) At some point, Regina Woodruff, Cupp's Professor of Biology at Whittier College, contacted Winifred Allan at the Scripps Institution of Oceanography (SIO), advising him that Cupp would be an outstanding PhD student to take on. The role of Cupp in the history of Oceanography has overshadowed, and left somewhat neglected, the third and most important legacy of Cupp in plankton research, her I Marine Diatoms of the West Coast of North America i . (2000) Easter Ellen Cupp: first woman to receive a Ph.D. in oceanography from Scripps institution of oceanography. [Extracted from the article]

Predicting recruitment in a reliable fashion is a great challenge within operational fisheries advice. Here, we consulted the unique but undercommunicated IMR Cod Larva Project (1975–1990), its spin-offs, placed in an international era of advancements over the last 50 years to glance into the future. Few initiatives of this kind have applied such extensive research approaches, spanning from laboratory, mesocosm, tank, and field studies to process modelling. The "critical period" concept appeared misleading, covering months rather than days of the early life history stages (ELHS) of Northeast Arctic cod. Larval feeding success was strongly modified by improved encounter rates from wind-induced turbulence. In addition, the following maternal effect studies evidenced that the dynamics of stock demography prior to spawning should be upheld to promote recruitment success. Although we now have lower-trophic level models as well as ELHS individual-based models, such models are still insufficiently reflecting the needed spatiotemporal resolution. The same problem applies to climate/circulation models. Nevertheless, this long-lasting research has significantly improved the mechanistic understanding of ELHS dynamics but also of the more predictable adult reproductive parameters. Based on a "to-list list," we suggest research avenues that should be pursued to further improve our ability predicting recruitment strength in marine fish stocks. [ABSTRACT FROM AUTHOR]

Plankton phototrophy consumes CO2, increasing seawater pH, while heterotrophy does the converse. Elevation of pH (>8.5) during coastal blooms becomes increasingly deleterious for plankton. Mixoplankton, which can be important bloom-formers, engage in both photoautotrophy and phagoheterotrophy; in theory, this activity could create a relatively stable pH environment for plankton growth. Using a systems biology modelling approach, we explored whether different mixoplankton functional groups could modulate the environmental pH compared to the extreme activities of phototrophic phytoplankton and heterotrophic zooplankton. Activities by most mixoplankton groups do not stabilize seawater pH. Through access to additional nutrient streams from internal recycling with phagotrophy, mixoplankton phototrophy is enhanced, elevating pH; this is especially so for constitutive and plastidic specialist non-constitutive mixoplankton. Mixoplankton blooms can exceed the size of phytoplankton blooms; the synergisms of mixoplankton physiology, accessing nutrition via phagotrophy as well as from inorganic sources, enhance or augment primary production rather than depressing it. Ocean acidification will thus enable larger coastal mixoplankton blooms to form before basification becomes detrimental. The dynamics of such bloom developments will depend on whether the mixoplankton are consuming heterotrophs and/or phototrophs and how the plankton community succession evolves. [ABSTRACT FROM AUTHOR]

EUGÈNE CANU'S WORK ON COPEPODS Eugène Canu was born on 11 September 1864 at Trith-Saint-Leger, close to Valenciennes, in the North of France. Eugène Canu made many contributions to copepod research in the late 19th century. In 1888 Giard, Canu's mentor, was recruited as assistant professor at the prestigious I Ecole Normale Supérieure i in Paris, and Canu continued his studies there under Giard. Pioneers of plankton research: Eugène Canu (1864-1952). [Extracted from the article]

Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 26 Lo Bianco, S. (1888) Notizie biologiche riguardanti specialmente il periodo di maturità sessuale degli animali del golfo di Napoli. Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 21 Groeben, C. (2005) LO BIANCO, Salvatore. Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 34 Lo Bianco, S. (1906a) Azione della pioggia di cenere caduta durante l'eruzione del Vesuvio dell'Aprile 1906 sugli animali marini. Google Scholar OpenURL Placeholder Text WorldCat 22 Groeben, C. (2007) Alfred Krupp, Anton Dohrn und Salvatore Lo Bianco: Pelagische Tiefseekampagnen um Capri 1900-1902. [Extracted from the article]

The interaction between biological and short-term physical processes affects plankton distribution and composition variability, with consequences for the entire ecosystem. Aspects of the plankton distribution at smaller scales have been understudied, mainly in coastal regions where highly variable conditions promote variations in the biophysical environment. This work aimed to investigate the short-term variations in the distribution of plankton along the inner shelf off Ubatuba, Brazil. We quantified the abundance and diversity of the main planktonic taxa (>100 μm) and their spatiotemporal distribution in winter 2018 and summer 2019 using high-resolution sensors and a shadowgraphic imaging system at cross-shore and fixed stations (12 and 24 h). Summer–winter environmental contrast was evident in the water column stability and plankton abundance. In the summer, higher values of plankton abundance and diversity were obtained. Our results suggested that spatiotemporal variations related to wind-induced mixing and water mass intrusions lead to variabilities in plankton populations on a time scale of a few hours, vertically between depth layers and at spatial scales ˂2 km. This study contributes to the knowledge of the mechanisms of biophysical interactions and their spatiotemporal variation, which is crucial for assessing the effects of climate variability on plankton-mediated ecosystem services. [ABSTRACT FROM AUTHOR]

Detailed in situ vertical and temporal distribution of appendicularians, marine snow, fecal pellets, nano- and microplankton were recorded simultaneously with environmental data in the San Jorge Gulf, Argentinean Patagonia (45°–47°S). Data were taken at a fixed station over 36 h in February 2014 with an autonomous Video Plankton Recorder and a FlowCAM®. The water column was thermally stratified with a pycnocline at ~ 40 m. Appendicularians dominated in the upper 65 m with a condensed pattern above the pycnocline at high chlorophyll a concentrations, matching the subsurface chlorophyll maximum layer at ~ 20 m. Our results suggest the absence of vertical migration of appendicularians. Marine snow, strongly correlated with appendicularians, showed high concentrations above the pycnocline, whereas fecal pellets from krill were distributed throughout the water column. Discarded houses of appendicularians or their mucus fragments were the main components of marine snow aggregates, with phytoplankton, detritus and krill pellets also contributing. Nanoplankton dominated over microplankton, with vertical distribution patterns that might depend on local grazing pressure and advective processes. Our study, the first one in the region using underwater imagery, emphasizes the leading contribution of appendicularians to marine snow aggregates in the San Jorge Gulf and their potential implications in the bentho-pelagic coupling. [ABSTRACT FROM AUTHOR]

Experimental nutrient additions are a fundamental approach to investigating plankton ecology. Possibilities range from whole-lake fertilization to flask assays encompassing a trade-off between closeness to the "real world" and feasibility and replication. Here we describe an enclosure type that minimizes the manipulation of planktonic communities during the enclosure filling. The enclosure (typically ~100 L volume) consists of a narrow translucent cylinder that can comprise the entire photic zone (or a large part of it in clear deep lakes, e.g. 20-m long) and holds a sediment trap at the bottom for recovering the sinking material. The enclosures are inexpensive and straightforward to build. Thus, many can be used in an experiment, favoring the diversity of treatments and the number of replicates. They also are lightweight with easy transport and use in lakes that cannot be reached by road. The enclosures are fundamentally aimed at investigating the short-term response of the planktonic community, integrated across the photic zone, to pulse perturbations using before and after comparisons and multiple replication and treatments. The pros and cons of the enclosure design are evaluated based on experience gained in Lake Redon, a high mountain ultraoligotrophic deep lake in the Pyrenees. [ABSTRACT FROM AUTHOR]

Although there are quantitative studies of the effect of formalin storage on copepod body size, no comparable data exist concerning storage in ethanol. We determined the degree of shrinkage of adult specimens of Parvocalanus crassirostris (Dahl, 1894) preserved in 96% ethanol for different periods of time. Measurements of the prosome of 50 females and 50 males were undertaken in fresh specimens and 7, 15, 30, and 60 days after initial preservation in ethanol. Despite variation among specimens, no significant shrinkage (P > 0.05) was detected on average males. For females, significant shrinkage (mean –4.2%; P < 0.05) was observed after seven days, with no further significant change thereafter. [ABSTRACT FROM AUTHOR]

While adult stomatopod crustaceans are relatively well studied, understanding of larval stomatopod ecology is lacking, largely due to difficulties studying larvae in their natural habitat. This study investigated how light environment (i.e. spectral composition) and time of day affected prey consumption in two species of larval stomatopod, Gonodactylaceus falcatus (Forskål, 1775) and Gonodactylellus sp. Individual larvae were placed with 20 Artemia nauplii prey in feeding chambers treated to produce different light environments with respect to ultraviolet (UV) light: full spectrum light UV+, full spectrum UV–, and a dark control. Chambers were lowered to a depth of 3 m for 2 hours at three times of day (noon, twilight, and night) to test 1) if larval feeding rates changed at different times of day and 2) if UV vision was involved in prey capture. We found that light was important for successful feeding, with both species eating significantly more in lighted treatments than the dark controls during daytime experiments. Gonodactylellus sp. also had a significantly higher feeding rate at twilight in the UV+ treatment than in the dark control. Both species showed decreased consumption at night compared to daytime rates, and decreased consumption in all dark controls. This study is one of the first to examine how ecological conditions affect feeding behavior in larval stomatopods. Our results suggest that light is important for larval stomatopod feeding, with differences between species in daily feeding activity periods. There was also a difference in total consumption between the two species, with the slightly larger Gonodactylaceus falcatus consuming nearly double the prey items as Gonodactylellus sp. at peak feeding times. Follow up studies should incorporate a variety of prey types to test how feeding changes based on food source and density. [ABSTRACT FROM AUTHOR]

In two surveys in an Icelandic fjord, September 2016 and October 2018, the target strength (TS) of the euphausiid Thysanoessa raschii was estimated at four frequencies (38, 70, 120, 200 kHz) by matching the acoustic backscatter to the number of euphausiids detected by a Video Plankton Recorder (VPR). Using forward-looking strobe lights on the VPR and doubling the towing speed lowered the estimated target strength by 4.3 dB. In 2016, the TS for euphausiids of mean length 20.7 mm averaged −98.4, −92.3, −86.6 and −82.8 dB at 38, 70, 120 and 200 kHz frequencies, respectively. In 2018, TS for euphausiids of mean length 19.9 mm averaged −98.2 dB at 38 kHz and −88.3 dB at 120 kHz. Theoretical modeling using a Distorted-Wave Born Approximation-based approach was used to compute the average target strength for the observed length distributions and for several density and sound speed contrast (g, h) and orientations. Except at 38 kHz, these results are in reasonable agreement with the TS estimated from the VPR-acoustic comparisons. The methodological approach presented provides an alternative to net-acoustic comparison or modeling for the estimation of euphausiid target strength. [ABSTRACT FROM AUTHOR]

Automatic recognition of in situ marine plankton images has long been treated as an image classification problem in machine learning. However, the deep learning-based classifiers are far from robust when used for predicting actual oceanic data that inevitably has distributional and compositional variations from their training sets. This paper proposes a novel image retrieval-based framework for plankton image recognition, within which supervised contrastive learning is used to train a feature extractor for better image representation, and similarity between the input and a gallery of reference images is compared to determine the identity of queries. We construct a dataset of high-quality in situ dark-field images of plankton and suspended particles to train and test the proposed retrieval model. Experimental results show that the image retrieval method has achieved excellent recognition performance similar to the state-of-the-art classification models on a very imbalanced closed-set, and also exhibited better generalizability in dealing with dataset shift and out-of-distribution issues. In addition, the image retrieval method has also demonstrated great architectural flexibility, bringing practical convenience for its adaptation to complex marine application scenarios. This new recognition framework is expected to enable real-time in situ observation of marine plankton in the actual oceanic underwater environment in the near future. [ABSTRACT FROM AUTHOR]

Our knowledge of aquatic fungal communities, their assembly, distributions and ecological roles in marine ecosystems is scarce. Hence, we aimed to investigate fungal metacommunities of coastal habitats in a subarctic zone (northern Baltic Sea, Sweden). Using a novel joint species distribution model and network approach, we quantified the importance of biotic associations contributing to the assembly of mycoplankton, further, detected potential biotic interactions between fungi–algae pairs, respectively. Our long-read metabarcoding approach identified 493 fungal taxa, of which a dominant fraction (44.4%) was assigned as early-diverging fungi (i.e. Cryptomycota and Chytridiomycota). Alpha diversity of mycoplankton declined and community compositions changed along inlet–bay–offshore transects. The distributions of most fungi were rather influenced by environmental factors than by spatial drivers, and the influence of biotic associations was pronounced when environmental filtering was weak. We found great number of co-occurrences (120) among the dominant fungal groups, and the 25 associations between fungal and algal OTUs suggested potential host–parasite and/or saprotroph links, supporting a Cryptomycota-based mycoloop pathway. We emphasize that the contribution of biotic associations to mycoplankton assembly are important to consider in future studies as it helps to improve predictions of species distributions in aquatic ecosystems. [ABSTRACT FROM AUTHOR]

Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 10 Boltovskoy, E. (1964b) Planktological Dictionary in Five Languages: English, Spanish, French, German and Russian, Servicio Hidrografía Naval, Buenos Aires (Argentina). Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 23 Boltovskoy, E. (1973a) Note on the determination of absolute surface water temperature by means of the foraminifer Globigerina bulloides d'Orbigny. Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 8 Boltovskoy, E. (1962) Planktonic foraminifera as indicators of different water masses in the South Atlantic. Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 3 Boltovskoy, E. (1954) The species and subspecies concept in the classification of the foraminifera. [Extracted from the article]

We used linear inverse ecosystem modeling techniques to assimilate data from extensive Lagrangian field experiments into a mass-balance constrained food web for the Gulf of Mexico open-ocean ecosystem. This region is highly oligotrophic, yet Atlantic bluefin tuna (ABT) travel long distances from feeding grounds in the North Atlantic to spawn there. Our results show extensive nutrient regeneration fueling primary productivity (mostly by cyanobacteria and other picophytoplankton) in the upper euphotic zone. The food web is dominated by the microbial loop (>70% of net primary productivity is respired by heterotrophic bacteria and protists that feed on them). By contrast, herbivorous food web pathways from phytoplankton to metazoan zooplankton process <10% of the net primary production in the mixed layer. Nevertheless, ABT larvae feed preferentially on podonid cladocerans and other suspension-feeding zooplankton, which in turn derive much of their nutrition from nano- and micro-phytoplankton (mixotrophic flagellates, and to a lesser extent, diatoms). This allows ABT larvae to maintain a comparatively low trophic level (~4.2 for preflexion and postflexion larvae), which increases trophic transfer from phytoplankton to larval fish. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the in vitro activity of fosfomycin, colistin and combinations thereof against planktonic and biofilm cultures of Gram-negative pathogens, mostly showing MDR phenotypes, at concentrations achievable via inhalation of aerosolized drugs.Methods: Activity against planktonic cultures was tested by the chequerboard assay with 130 strains, including 52 Pseudomonas aeruginosa, 47 Klebsiella pneumoniae, 19 Escherichia coli, 7 Stenotrophomonas maltophilia and 5 Acinetobacter baumannii. Activity against biofilm cultures was tested by biofilm chequerboard and quantitative antibiofilm assays with a subset of 20 strains. In addition, 10 of these strains were tested in mutant prevention concentration (MPC) assays.Results: Against planktonic cultures, synergism between fosfomycin and colistin was detected with a minority (10%) of strains (eight K. pneumoniae and five P. aeruginosa), while antagonism was never observed. Synergism between fosfomycin and colistin against biofilms was observed with the majority of tested strains (16/20 in biofilm chequerboard assays, and 18/20 in the quantitative antibiofilm assays), including representatives of each species and regardless of their resistance genotype or phenotype. Furthermore, combination of fosfomycin and colistin was found to significantly reduce the MPC of individual drugs.Conclusions: Fosfomycin and colistin in combination, at concentrations achievable via inhalation of nebulized drugs, showed notable synergy against MDR Gram-negative pathogens grown in biofilm, and were able to reduce the emergence of fosfomycin- and colistin-resistant subpopulations. [ABSTRACT FROM AUTHOR]

The phenology, distribution, and size composition of plankton communities are changing rapidly in response to warming. This may lead to shifts in the prey fields of planktivorous fish, which play a key role in transferring energy up marine food chains. Here, we use 60 + years of Continuous Plankton Recorder data to explore temporal trends in key taxa and community traits in the prey field of planktivorous lesser sandeels (Ammodytes marinus) in the North Sea, the Faroes and southern Iceland. We found marked spatial variation in the prey field, with Calanus copepods generally being much more common in the northern part of the study area. In the western North Sea, the estimated amount of available energy in the prey field has decreased by more than 50% since the 1960s. This decrease was accompanied by declining abundances of small copepods, and shifts in the timing of peak annual prey abundances. Further, the estimated average prey community body size has increased in several of the locations considered. Overall, our results point to the importance of regional studies of prey fields, and caution against inferring ecological consequences based only on large-scale trends in key taxa or mean community traits. [ABSTRACT FROM AUTHOR]

This is a correction to: Erwin Kers, Eva Leu, Per-Arne Amundsen, Raul Primicerio, Martin Kainz, Amanda E Poste, Under ice plankton and lipid dynamics in a subarctic lake, Journal of Plankton Research, Volume 46, Issue 3, May/June 2024, Pages 323–337, https://doi.org/10.1093/plankt/fbae018In the originally published version of this article, there was an error in the legend of Figure 3, whereby Eudiaptomus graciloides was misspelled as Euaugaptilus graciloides.This has been corrected. [Extracted from the article]

This document is a correction to an article titled "Seasonal organization of tintinnid community by temperature preference and LOD size-class in a subtropical brackish embayment" published in the Journal of Plankton Research. The correction addresses errors in the original article, specifically in the abundance values of the tintinnids, the caption of Figure 4, and the images of Figures 5, 6, and 7. The Supplementary data file has also been updated to correct the values of the Y axis of Figures S1-S6. [Extracted from the article]

Hopefully, due to this essay, when one hears or reads "Utermöhl", the person Hans Utermöhl will come to mind, not just an image of a plastic cylinder or an inverted microscope! Utermöhl's example of an inverted microscope made for field work was a new portable inverted microscope manufactured by Firma Walter Schweder in Kiel, a precision engineering company. The name Utermöhl is familiar to most of us who work on plankton, and especially to those of us who work on phytoplankton or microzooplankton. Google Scholar OpenURL Placeholder Text WorldCat 9 Utermöhl, H. (1931a) Neue Wege in der quantitativen Erfassung des plankton. [Extracted from the article]

Assessment of zooplankton abundance, distribution, community composition, and temporal variability is critical to understanding the effects of climate variability and change on lower trophic level production and availability for consumption by larger consumers. Zooplankton sampling is performed across the Canadian continental shelf system by Fisheries and Oceans Canada's Atlantic Zone Monitoring Programme (AZMP). Sampling includes semi-monthly to monthly collection of zooplankton using vertical net tows (VNTs) deployed from near-bottom to surface at stations on the central Scotian Shelf (Stn 2, 150 m depth) and Newfoundland Shelf (Stn 27, 175 m depth), and by Continuous Plankton Recorders (CPRs) in the near-surface layers along routes over the Scotian and Newfoundland shelves (0–10 m depth). Here, we compare abundance metrics for 11 copepod taxa collected using both gear types in both regions between 1999 and 2015. Seasonal cycles of VNT and CPR abundance were similar for near-surface residents. VNT: CPR abundance ratios varied year-round for vertical migrants, as ontogenetic migrants shifted their vertical distribution, and as diel migrants changed their migratory behaviour. For some taxa, differences in annual average VNT: CPR abundance ratios between regions suggest differences in vertical distribution, while for others differences in inter-annual variability for VNT and CPR abundances suggest differences in the dynamics of the near- and sub-surface components of the populations. [ABSTRACT FROM AUTHOR]

Fronts are particularly productive regions of the ocean, and biodiversity hotspots for many marine species. Here we use an ocean-ecosystem model to investigate the effect of fronts on plankton ecology. We focus on energetic fronts in Western Boundary Current systems that efficiently inject nutrients into the euphotic layer and which are physical boundaries between productive and oligotrophic provinces. We found that the fronts form an environment distinct from both provinces, favorable to some plankton groups (diatoms, dinoflagellates and large carnivorous zooplankton) and less favorable to others (pico-phytoplankton, coccolithophores and small grazers), and with an overall larger diversity. In agreement with previous understanding, we find that bottom-up abiotic processes (nutrient enrichment) explain the prevalence of groups with fast growing rates (the "winners"). Importantly, our results also show that biotic interactions within the ecosystem may play a larger role than previously thought. We show that the winners can have a negative impact on other plankton species (the "losers") through two indirect competitive processes: community shading (modification of the light environment by the plankton community leading to light-limitation of some plankton groups) and shared predation (where an increase in one functional group leads to increased grazing by a shared predator on another functional group). [ABSTRACT FROM AUTHOR]

Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 27 Marshall, S. M. and Orr, A. P. (1955a) The Biology of a Marine Copepod Calanus Finmarchicus (Gunnerus), Oliver & Boyd. Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 31 Marshall, S. M. and Orr, A. P. (1972) The Biology of a Marine Copepod, Springer. Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 32 Marshall, S. M., Orr, P. and Conover, R. J. (1961) On the biology of Calanus finmarchicus XII. Google Scholar Google Preview OpenURL Placeholder Text WorldCat COPAC 28 Marshall, S. M. and Orr, A. P. (1955b) On the biology of Calanus finmarchicus VIII. [Extracted from the article]

Aims: To investigate the phylogenetic composition and functional potential of bighead carp (Hypophthalmichthys nobilis) gut microbiome in two rearing patterns (bighead carp polycultured with Oreochromis niloticus in pond A and bighead carp polycultured with Cyprinus carpio in pond B, respectively), as well as the changes of plankton in the cultured water at four different time points. Methods and Results: The intestinal contents were sequenced using Illumina HiSeq of bacterial 16S rRNA. Cyanophyta and Chlorophyta were the prevalent phytoplankton in the water, whereas Rotifers and Protozoa were the predominant zooplankton. In all, 779,563 quality‐filtered sequences and 8870 amplicon sequence variants were obtained from 24 samples that numbered T1A1 to T4A3 and T1B1 to T4B3, resulting in 35 phyla, with Proteobacteria, Firmicutes, Fusobacteria and Cyanobacteria dominating. According to alpha diversity and beta diversity measurements, the bacterial communities were diverse, Chao1 richness and Pielou's evenness were significantly lower in the T2B and T4B groups. The gut bacterial communities of T1A, T1B, T2A and T2B groups differed from those of other samples, which formed distinctly clusters with principal coordinate analysis and non‐metric multidimensional scaling analysis. PICRUSt2 predictive function analysis revealed that different culture patterns influenced the gut microbiota metabolic capacity. Conclusions: Intestinal bacteria belonging to the phyla Proteobacteria, Firmicutes, Cyanobacteria and Fusobacteria are better suited to inhabit in various environments and perform specific functions. Furthermore, contact with the external environment and nutrient intake also stimulate the variety of intestinal microbiotas in polycultured bighead carp. Significance and Impact of the Study: This is the first comprehensive, high‐throughput investigation of gut microbiota diversity in bighead carp during various seasons in two polycultured patterns and provide preliminary information on gut microbiome composition and changes, laying a crucial foundation for future research on fish culture patterns in various environments. [ABSTRACT FROM AUTHOR]

Various field studies on plankton dynamics have broadened our understanding of seasonal succession patterns. Additionally, laboratory experiments have described consumers ranging from generalists to selective grazers. While both approaches can give us a good understanding of the ecosystem and its dynamics, drawbacks in identification and a limited coverage of the ecosystem have left open questions on the generality of previous results. Using an integrative approach, we investigated water samples taken at Helgoland Roads by metabarcoding to describe seasonal succession patterns of the whole plankton community. By use of network analysis, we also tried to identify predator–prey dynamics. Our data set depicted the strong seasonality typically found for temperate waters. Despite a stable background community surviving strong fluctuations, small and abrupt changes, such as pronounced blooms and random appearance of autotrophs, cause seasons to be quite different in an inter-year comparison. Main consumers were copepods, ciliates, and dinoflagellates, of which the latter were most abundant. Furthermore, our results suggest that zooplankton predators might favour specific prey during certain time periods but seem to be quite opportunistic otherwise throughout the year. The variability and potential for many different relationships in the plankton community might be an indicator of resilience in the system. [ABSTRACT FROM AUTHOR]

Much has been published on the effects of ocean acidification on plankton since the original Royal Society 2005 report. In addition to direct effects on primary production, it is clear that ocean acidification also has profound consequences for biogeochemistry. Furthermore, although ocean acidification can have direct effects of on grazers such as copepods, acidification induces changes in nutritional value of phytoplankton which can be passed on up the food chain. There has also been recognition of the complexity of the interactions between elevated CO2 and other environmental factors and this has seen an upsurge in climate change research involving multifactorial experiments. In particular, the interaction of ocean acidification with global warming resulting from the increasing greenhouse effect has been investigated. There has also been research on acidification and warming effects in inland water plankton. These, combined with novel experimental techniques and long term studies of genetic adaptation, are providing better insights to plankton biology and communities in a future world. [ABSTRACT FROM AUTHOR]

Although diel vertical migration (DVM) in aquatic systems may account for the largest daily migration of biomass globally, our understanding of this process under ice cover is limited, particularly in fresh water. The date of lake ice onset and duration of ice cover is declining globally, therefore determining the extent of plankton migrations under ice is imperative to inform our baseline understanding of seasonal differences in community structure and function, and how conditions may change over time. We investigated whether plankton exhibit DVM under ice and explored interactions between phytoplankton and zooplankton at highly resolved space–time scales across 24 h in a eutrophic system. Despite the dominance of motile taxa, phytoplankton remained vertically segregated based on morpho-functional groups throughout the sampling period. Daphnia mendotae exhibited size-structured DVM with an upward migration at sunset and sunrise, and midnight sinking, presumably to avoid the rise of predatory Chaoborus. We hypothesize that because overwintering daphnids require rich lipid stores, D. mendotae migrated to access small, lipid-rich phytoplankton that were limited to surface waters. Given our study took place during an unusually warm winter in a eutrophic system, our results may represent future under-ice dynamics under increasing eutrophication pressure and climate warming in shallow lakes. [ABSTRACT FROM AUTHOR]

The annual/temporal and vertical dynamics of the microbial food web (MFW) was studied in a coastal station of the oligotrophic Eastern Mediterranean Sea. The present study analyzed the changes of all components of the MFW with a specific focus on the relationships between different size classes of heterotrophic and mixotrophic ciliates with their potential prey. The MFW was dominated by heterotrophic picoplankton in all months and depths analyzed, whereas autotrophic nanoplankton took advantage in cold months with higher nutrient availability. On the other hand, mixotrophic microplankton biomass was higher in summer when nutrients and chlorophyll-a were scarce. As part of the mixotrophic biomass, mixotrophic ciliates were correlated with their "potential" prey at the surface and deep chlorophyll maximum. Large mixotrophic ciliates (L. strobila) were more selective in terms of potential prey, showing a correlation with Synechococcus. On the other hand, mixotrophic nanociliates (Strombidium dalum) were correlated differently with different potential prey according to depth, supporting the idea that nanociliates could be more generalists in terms of prey selection. Because the relationships between mixotrophic ciliates and their potential prey are still poorly studied, this work represents the start for further investigation. [ABSTRACT FROM AUTHOR]

The causes of seasonal phytoplankton blooms in the ocean are a debated topic. The disturbance-recovery hypothesis posits that blooms are initiated when seasonally changing light and mixing conditions disrupt attractive equilibrium states in the predator–prey relationship between zooplankton and phytoplankton, leading to an accumulation in phytoplankton biomass. This paper follows up on this notion with a nutrient-phytoplankton-zooplankton (NPZ) model incorporating diffusion and depth-dependent coefficients in which we explore the nature of these attractive states. The reaction–diffusion NPZ model, incorporated with seasonal solar radiation and mixed layer depth data, simulates blooms with better timing than a related ordinary differential equations model but still leaves room for further modeling and improvement. The results of the data-driven, reaction–diffusion model aid in understanding the driving forces of the simulated phytoplankton blooms. The results also reveal a significant influence on the vertical structure of plankton concentration by the attenuation of light with depth in the ocean. Models that accurately simulate blooms tend to share characteristics of the reaction–diffusion model in this paper. The dynamics described in this paper could be a key mechanism that seasonally disrupts the ecological balance between phytoplankton and zooplankton and facilitates a high-latitude marine phytoplankton bloom. [ABSTRACT FROM AUTHOR]

Normalized biomass size spectra (NBSS) are frequently used to describe pelagic communities. However, the underlying structure of NBSS may lead to varying intercepts and slopes when only a portion of the biomass range is sampled. This may be further perpetuated by the sampling efficiency of different gears/mesh sizes. Spatial and seasonal effects of mesh size on zooplankton NBSS and production were evaluated. Zooplankton were collected during winter, spring and summer (2017–2019) between Vancouver Island and Station Papa (50°N, 145°W) using a 64-μm Working Party 2 (WP-2) net and a 236-μm bongo net and analyzed using a bench-top laser optic particle counter. WP-2 and bongo NBSS overlapped in 11 size classes, for which the WP-2 more effectively sampled smaller size classes and converged with the bongo in larger size classes. Differences in NBSS slopes from the two nets were detected, yet no differences in total production. However, the contribution of individual size classes to total production varied spatially and seasonally. Total production in the coastal region exhibited strong seasonal variability. Notably, summer estimates of production in the coastal region were at least 2-fold higher than transitional and open ocean regions. This study suggests that using one mesh size may underestimate zooplankton NBSS and thus production. [ABSTRACT FROM AUTHOR]

Objectives: To investigate the in vitro activity of antibiotics against clinical Elizabethkingia anophelis isolates and to find a suitable antibiotic combination with synergistic effects to combat antibiotic-resistant E. anophelis and its associated biofilm.Methods: E. anophelis isolates were identified by 16S rRNA sequencing; 30 strains with different pulsotypes were identified and the MIC, antibiotic resistance mechanism, antibiotic combination activity and killing effects of antimicrobial agents on biofilms of these strains were determined.Results: All E. anophelis isolates were susceptible to minocycline and cefoperazone/sulbactam (1:1). More than 90% of clinical isolates were susceptible to cefoperazone/sulbactam (1:0.5), piperacillin/tazobactam and rifampicin. Some novel mutations, such as gyrA G81D, parE D585N and parC P134T, that have never been reported before, were identified. The synergistic effect was most prominent for the combination of minocycline and rifampicin, with 93.3% of their FIC index values ≤0.5, and no antagonism was observed using the chequerboard method. This synergistic effect between minocycline and rifampicin was also observed using time-killing methods for clinical E. anophelis isolates at both normal inoculum and high inoculum. Twenty-nine isolates tested positive for biofilm formation. Minocycline remained active against biofilm-embedded and biofilm-released planktonic E. anophelis cells; however, the enhanced effect of minocycline by adding rifampicin was only observed at 24 h (not at 72 and 120 h).Conclusions: Although E. anophelis was resistant to many antibiotics and could exhibit biofilm formation, minocycline showed potent in vitro activity against this pathogen and its associated biofilm. [ABSTRACT FROM AUTHOR]

The increasing use of image-based observing systems in marine ecosystems allows for more quantitative analysis of the ecological zonation of zooplankton. Developing methods that take advantage of these systems can provide an increasingly nuanced understanding of how morphometric characteristics (especially size) are related to distribution, abundance and ecosystem function via a wider application of allometric calculations of biogeochemical fluxes. Using MOCNESS sampling of zooplankton near the Bermuda Atlantic Time Series and a ZooSCAN/EcoTaxa pipeline, we apply a new taxonomically resolved biomass to biovolume dataset and a suite of R scripts that provide information about the relationships between zooplankter size, taxonomy, distribution, depth of migration, magnitude of migration and biogeochemical contributions (e.g. respiratory O2 consumption). The analysis pipeline provides a framework for quantitatively comparing and testing hypotheses about the distribution, migration patterns and biogeochemical impacts of mesozooplankton. Specifically, our code helps to visualize a size-based structure in the extent of vertical migration and allow for a quantification of the relative importance of non-migratory versus migratory organisms of various size classes. It additionally allows us to quantify the error associated with various methods of calculating active flux, with size-based analysis being the most important methodological choice, and taxonomic identification being the least. [ABSTRACT FROM AUTHOR]

The Plankton Imager (PI) is an underway semi-automated, high-speed imaging instrument, which takes images of all passing particles and classifies the mesozooplankton present. We used data (temperature, salinity and mesozooplankton abundance) collected in the Celtic Sea in spring and autumn from 2016 to 2019 to assess the ability of the PI to describe temporal changes in the mesozooplankton community and to capture the seasonality of individual taxa. The description obtained using the PI identified both seasonal and interannual changes in the mesozooplankton community. Variation was higher between years than seasons due to the large variation in the community between years in autumn, attributed to the breaking down of summer stratification. The spring community was consistent between years. The seasonality of taxa broadly adhered to those presented in the literature. This demonstrates the PI as a robust method to describe the mesozooplankton community. Finally, the potential future applications and how to make best use of the PI are discussed. [ABSTRACT FROM AUTHOR]

Restricted to low-productivity environments near their thermal maxima, larval tunas may be threatened by warming global temperatures, yet our understanding of how they are constrained is limited. We examined blackfin tuna (Thunnus atlanticus , presumptive) diet and growth in the context of their prey and predators in the Straits of Florida in 2 years with contrasting summer conditions: low temperature (26.7–28.3°C)–high prey and high temperature (28.4–29.0°C)–low prey. In the cooler, high-prey conditions, larvae had 30% faster growth (0.45 mm d−1), fuller guts from predominantly feeding on calanoid copepods, and were 10× more abundant, dominating the larval fish assemblage. In contrast, in warm, low-prey conditions fewer, younger, and slower-growing (0.35 mm d−1) T. atlanticus fed predominantly on nauplii and had less full guts. Modelling individual growth across years revealed that growth peaked at an optimum of 28.5°C (5°C below known thermal maxima in the field) and high densities of predators selectively consumed slower-growing larvae. Low-prey availability may reduce the thermal optima of larvae, as growth and survival are diminished when low prey and high temperature coincide. Our results illustrate the importance of considering food web dynamics with temperature when predicting the response of organisms to ecosystem variability, particularly ongoing climate change. [ABSTRACT FROM AUTHOR]

Indicators based on broad functional characteristics, which group plankton taxa into "lifeforms", summarize changes across a high number of taxa in a way that reflects changes in community functioning and are used to inform policy assessments. Key questions remain, however, as to what extent plankton taxa within these lifeforms share responses to environmental change. Addressing this knowledge gap can provide additional information on the influence of environmental drivers, including climate change, on plankton communities. Here, we use a multi-decadal plankton time series to examine the extent to which taxa within lifeforms share responses to sea surface temperature (SST) change. At the North Sea scale, the individual taxa responses within the dinoflagellate lifeform are skewed towards a negative response to increasing SST, consolidating previous findings that dinoflagellate abundance is decreasing with ocean warming. The individual taxa responses within the zooplankton lifeforms, however, varied, suggesting that lifeform traits are less of a factor determining response to SST for zooplankton than for phytoplankton. The lifeform level of grouping taxa, therefore, is useful for communicating change in the state and functioning of ecosystems, but finer taxonomically resolved data are essential for determining the drivers of plankton community change, including climate influences, during formal assessments. [ABSTRACT FROM AUTHOR]

Summer upwelling off Hainan Island (northern South China Sea) is influenced by fresher coastal water masses. To assess the ecological effects of this complicated oceanography, a cruise was conducted in August 2016. We investigated the spatial patterns of phytoplankton size structure, diversity and quantity of small eukaryotes (0.2–20 μm) across the upwelling system. In the inner-shelf waters, nanophytoplankton contributed a higher proportion to phytoplankton biomass than microphytoplankton and picophytoplankton. High-throughput sequencing of 18S rRNA genes and community analysis indicated that the horizontal variation in community structure of small eukaryotes was larger than the vertical. The relative sequence proportions of dinoflagellates, diatoms, ciliates and Micromonas in the surface layer gradually decreased from the inner shelf to the slope, whereas the Rhizaria, Bathycoccus and Ostreococcus exhibited an opposite trend. The spatial patterns of taxon-specific rDNA copy numbers were similar to the patterns based on the relative proportions. Redundancy analysis revealed that turbidity, salinity and |${\mathrm{NO}}_3^{-}$| were the most important environmental variables in structuring the community of small eukaryotes. The cell abundance of photosynthetic picoeukaryotes was significantly correlated with the rDNA abundance of Mamiellophyceae and the cell abundance of nanoeukaryotes was significantly correlated with the rDNA abundance of dinoflagellates plus diatoms. [ABSTRACT FROM AUTHOR]