Distribution Of Plankton Research Articles

Phytoplankton in Lake Mainit, Philippines

The study determined the composition, abundance, and distribution of phytoplankton in Lake Mainit. Plankton samples were collected in eight sampling stations four times in 2018. A total of 26 phytoplankton taxa in four groups – Bacillariophyceae/Myxophyceae, Chlorophyceae, Cyanophyceae and Euglenophyceae were identified. Aulacoseira was ranked as the most abundant taxa, followed by Zygnema, Fragilaria, Trichodesmium, and Ulothrix. ANOVA revealed no significant (P < 0.05) difference in the number of phytoplankton between the eight stations during the first sampling. In the second sampling, Bunga showed a significantly (P < 0.05) lower number of phytoplankton than the other stations. The third sampling also showed no significant (P < 0.05) difference in the number of phytoplankton between stations. During the fourth sampling, Tagbuyawan had by far (P < 0.05) the highest number of phytoplankton. Species diversity (H’) of phytoplankton was stable at Magticao, Jaliobong, Dinarawan, Kalinawan, and Bunga. The dominance of some species (Aulacoseira, Fragilaria, and Zygnema) affected the diversity and distribution of plankton. Spectrophotometric readings recorded an average Chl-a of 0.75 µg/L. The lake was still considered oligotrophic. Remediation measures and further studies on the lake towards the primary variation of plankton are recommended. Management efforts should be strengthened to support the sustainability of life in the lake.

Anthropogenic influence on water quality and phytoplankton diversity of upper Ganga basin: A case study of Ganga River and its major tributaries

AbstractWater quality plays a vital and key role in estimating the diversity and abundance of phytoplankton in freshwater ecosystem. The water quality of freshwater body is rapidly deteriorating by various anthropogenic activities and diverse emancipations from the population growth, urbanization, and industrialization. The aim of present research work was to estimate the anthropogenic influence on water quality and phytoplankton diversity of upper Ganga basin. The water quality and plankton diversity of a Ganga River and its major tributaries was studied between September 2018 and September 2020 in eight sampling stations. Some physico‐chemical parameters like turbidity, dissolved oxygen, and biological oxygen demand showed a slight increase in sampling stations 7 and 8. Multi‐correlation was calculated between physico‐chemical parameters and phytoplankton density. Totally 31 genera of phytoplankton were recorded and represented by five groups, Bacillariophyceae (14 genera), Chlorophyceae (11 genera) Myxophyceae (4 genera), Euglenophyceae (1 genera), and Xanthophyceae (1 genera). Dissolved oxygen showed a direct influence on the distribution of plankton and also showed a positive correlation with phytoplankton diversity. Finally, it can be concluded that human activities including River bed mining, construction of Dam, and barrages had negatively impacted the water quality and phytoplankton diversity. Still, these kinds of activities to be checked regularly and can be controlled.

Spatial and temporal dynamics of phytoplankton in association with habitat parameters in a tropical reservoir, India

Phytoplankton, the primary producers in an aquatic ecosystem, also act as indicators of pollution by alterations in species composition and population structure. Study on plankton dynamics in relation to environment forms the base of any aquatic ecosystem management. So, a study on the variations in the plankton population influenced by abiotic factors was conducted in the Paleru Reservoir, India. A total of 48 plankton genera belonging to 9 classes were recorded. The Shannon-Wiener diversity index ranged from 1.098 to 2.615 with temporal variations. Plankton density showed significant (p ≤ 0.05) spatial variations with the highest density at the cage site irrespective of the season (4.126 × 105 ± 199 cells/litre, 2.814 × 105 ± 72.5 cells/litre and 3.197 × 105 ± 52.5 cells/litre during pre-monsoon, monsoon and post-monsoon, respectively). Seasonal analysis revealed significantly (p ≤ 0.05) high plankton density during pre-monsoon, followed by post-monsoon and monsoon respectively. The reservoir is moderately polluted as established from the diversity index and the Algal Genus Pollution Index except at the cage site where it receives a polluted status. The relationship of plankton distribution with the environment was established employing canonical correspondence analysis and correlation coefficient. Phosphate-P, nitrate-N, transparency, hardness, pH and dissolved oxygen are the major abiotic factors influencing the plankton distribution in Paleru. Even though Cyanophyceae dominated the plankton population, there was no plankton bloom-associated toxicity, indicating the health and dynamic nature of the reservoir. However, significantly high plankton density indicating a polluted status at the cage site reveals the influence of cage culture.

Impacts of jellyfish on marine cage aquaculture: an overview of existing knowledge and the challenges to finfish health

AbstractGelatinous plankton present a challenge to marine fish aquaculture that remains to be addressed. Shifting plankton distributions, suggested by some to be a result of factors such as climate change and overfishing, appear to be exacerbated by anthropogenic factors linked directly to aquaculture. Fish health can be negatively influenced by exposure to the cnidarian hydrozoan and scyphozoan life stages commonly referred to as “jellyfish”. Impact is particularly pronounced in gill tissue, where three key outcomes of exposure are described; direct traumatic damage, impaired function, and initiation of secondary disease. Cnidarian jellyfish demonstrated to negatively impact fish include Cyanea capillata, Aurelia aurita, and Pelagia noctiluca. Further coelenterates have also been associated with harm to fish, including sessile polyps of species such as Ectopleura larynx. An accurate picture of inshore planktic exposure densities within the coastal environments of aquaculture would aid in understanding cnidarian species of concern, and their impact upon fish health, particularly in gill disease. This information is however presently lacking. This review summarises the available literature regarding the impact of gelatinous plankton on finfish aquaculture, with a focus on cnidarian impact on fish health. Present strategies in monitoring and mitigation are presented, alongside identified critical knowledge gaps.

Short-Term Spatiotemporal Variability in Picoplankton Induced by a Submesoscale Front South of Gran Canaria (Canary Islands)

The distribution and variability of phytoplankton in the upper layers of the ocean are highly correlated with physical processes at different time and spatial scales. Model simulations have shown that submesoscale features play a pivotal role on plankton distribution, metabolism and carbon fluxes. However, there is a lack of observational studies that provide evidence for the complexity of short-term phytoplankton distribution and variability inferred from theoretical and modeling approaches. In the present study, the development and decay of a submesoscale front south of Gran Canaria Island is tracked at scales not considered in regular oceanographic samplings in order to analyze the picoplankton response to short-term variability. Likewise, the contribution of each scale of variability to the total variance of the picophytoplankton community has been quantified. We observe statistically different picophytoplankton assemblages across stations closer than 5 km, and between time periods shorter than 24 h, which were related to high physical spatiotemporal variability. Our results suggest that both temporal and spatial variability may equally contribute to the total variance of picoplankton community in the mixed layer, while time is the principal contributor to total variance in the deep chlorophyll maximum (DCM).

Dynamics of currents and biological scattering layers around Senghor Seamount, a shallow seamount inside a tropical Northeast Atlantic eddy corridor

Biophysical interactions of the mesopelagic fauna and hydrodynamic features were investigated at a shallow, tall seamount in the tropical Northeast Atlantic based on data from three inter-disciplinary surveys collected between 2009 and 2015. Senghor Seamount is located close to the equator in a unique but underexplored oceanographic setting, where classical seamount effects are expected to be small. Shipboard Acoustic Doppler Current Profiler (ADCP) and remote sensing data revealed flow phenomena strongly varying over different temporal and spatial scales. The quasi-steady, longer period flow at the seamount was largely unchanged by flow-topography interaction with the exception of a persistent and recurring shadow zone of weaker currents downstream of the summit. Senghor Seamount is exposed to energetic mesoscale eddy activity in surrounding waters with potentially large physical and biological implications. At higher frequencies, tidal currents interacting with the seamount generated large-amplitude internal waves propagating horizontally and vertically away from the summit. Analysis of acoustic backscatter data and micronekton biomass displayed prominent near-surface night time and deep (>400 m) day time scattering layers associated with the diurnal vertical migration of the mesopelagic fauna. An intense and previously unreported aggregation of acoustic scatterers was detected in the depth range 150–300 m inside a radius of 3 km along the upper slopes of the seamount summit. ADCP measurements over a full semi-diurnal tidal cycle suggest that biophysical interactions were present in near-seafloor waters around the upper seamount as evidenced by plankton distributions that were modified by topographic blocking during descent and aggregation in waters characterised by internal waves and enhanced tidally-driven energy dissipation.

Spring Distribution of Ciliate Plankton in the Southeastern Yellow Sea in 2019

As planktonic ciliates have been recognized as important players in marine microbial food webs, relevant studies have been conducted in the western coastal waters of the Yellow Sea. However, little is known about ciliate distributions from the eastern coast of the Yellow Sea near the Korean Peninsula. A spring cruise in April 2019 was carried out to investigate vertical and horizontal distributions of ciliate plankton at 18 stations that form three zonal sections in the eastern area. Biological (picoplankton, nanophytoplankton, and mesozooplankton) and hydrological (water temperature and salinity) environments were also analyzed to understand relationships between the ciliate distributions and the environments. High abundance (ca. 2400 cells L−1) of a large ciliate species, Laboea strobila, was observed at the surface water of Stn. 37–5. Abundance peak of large (> 50 μm) ciliates coincided with the peak of mesozooplankton abundance. Spatial distribution of the large ciliates was associated with nanophytoplankton distribution while a smaller (20–50 μm) ciliate group was associated with picoplankton distribution. Therefore, the spring distribution of ciliate plankton in the southeastern coast of the Yellow Sea indicates that food size for the ciliates is one of the important factors controlling ciliate compositions as well as their abundances. Further investigations need to be carried out to understand seasonal differences of ciliate distributions in the eastern Yellow Sea.

Analisis pola transportasi sedimen terhadap sebaran plankton dan daerah penangkapan ikan muara Sungai Kampar

This study aimed to analyze the pattern of sediment transport to the distribution of plankton and fishing ground in the estuary of KamparRiver. This study used survey methods, the study sample was obtained in the field are considered to represent the Kampar River estuary. Then the sampling results in the form of TSS, brightness, temperature, salinity, pH, flow velocity and plankton descriptively analyzed and discussed with reference to data interpretation method by using mathematical models (software mike21 ). The results showed the concentration distribution of sediment at the mouth of the Kampar River in east monsoon amounted to 8.76 million tons / day and in the west monsoon amounted to 7.64 million tons / day. A region prone to silting due to sediment transport is periodically southeastern portion Mendol. Based on the analysis modeling , plankton diversity index tends to be low in the study site so that the waters around the Mendol island excluding strategic area for fishing grounds it is indicated there has been a downward trend in plankton diversity index as the primary productivity . The existence of TSS may hinder the penetration of light that ultimately affect the photosynthetic plankton.

Impact of Port and harbour activities on plankton distribution and dynamics: A multivariate approach

Numerous researches have been conducted to study the impact of Port activities on water quality. However, investigation on the response of the inhabiting biota to Port related extrinsic factors is extremely limited. Using Canonical Correspondence Analysis, comprehensive assessment of plankton population dynamics and distribution corresponding to the spatial heterogeneity in physico-chemical characteristics of harbour and adjacent coastal water is conducted. The results revealed resource competition for nitrate, predator mediated co-existence of species favoured by active switching and Port influenced environmental filtering due to suspended solids, and oil and grease as the predominant factor to modulate the plankton community structure and succession in harbour. The higher heterogeneity in the measured environmental variables at coast revealed dispersion of nutrient and other pollutants from harbour into the adjacent coastal water during ebb tide. Our results indicate reengineering of Port infrastructures and efficient management policies including water quality standards to facilitate proper water circulation and minimize pollution with a long term goal to reconcile economic interest with ecosystem conservation.

Generation of ocean internal wave with vertical-slice hydrodynamic simulation

The instability of the density of seawater causes the formation of internal waves in the sea. This phenomenon is difficult to observe visually but can be studied with a hydrodynamic model approach. This study investigates the internal waves caused by underwater obstructions (seamounts) and the stratified density with a two-dimensional marine hydrodynamic model. Four scenarios are simulated in studying internal waves. Two scenarios used one barrier with uniform density and stratified density (based on the Brunt Vaisala stability frequency N 2 = 5 x 10-4 s-2). Meanwhile, the other two scenarios use two barriers with uniform density and stratified density (based on the Brunt Vaisala stability frequency N 2 = 5 x 10-4 s-2). Based on the simulation results, it is known that the density conditions have a significant effect on the dynamics of ocean currents. In hydrodynamic simulations of one and two barriers with varying or stratified densities, current resonances and density resonances are formed underwater topography. Meanwhile, in uniform density, the currents formed the rotor, cavity, turbulence, and resonance with the underwater topography. Thus the current dynamics are stronger in the case of uniform density than in the stratified density. It has implications for differences in the mixing of suspended matter in the sea. So this study can be useful in the study of sediment transport, upwelling, the thermocline layer, energy from internal waves, and the distribution of plankton or fish larvae.

Characterization of the biological, physical, and chemical properties of a toxic thin layer in a temperate marine system

The distribution of plankton in the ocean is patchy across a wide range of spatial and temporal scales. One type of oceanographic feature that exemplifies this patchiness is a ‘thin layer’. Thin layers are subsurface aggregations of plankton that range in vertical thickness from centimeters to a few meters, which may extend horizontally for kilometers and persist for days. We undertook a field campaign to characterize the biological, physical, and chemical properties of thin layers in Monterey Bay, California (USA), an area where these features can be persistent. The particle aggregates (marine snow) sampled in the study had several quantifiable properties indicating how the layer was formed and how its structure was maintained. Particles were more elongated above the layer, and then changed orientation angle and increased in size within the layer, suggesting passive accumulation of particles along a physical gradient. The shift in particle aggregate orientation angle near the pycnocline suggests that shear may also have played a role in generating the thin layer. Pseudo-nitzschia spp. were the most abundant phytoplankton within the thin layer. Further, both dissolved and particulate domoic acid were highest within the thin layer. We suggest that phosphate stress is responsible for the formation of Pseudo-nitzschia spp. aggregates. This stress together with increased nitrogen in the layer may lead to increased bloom toxicity in the subsurface blooms of Pseudo-nitzschia spp. Several zooplankton groups were observed to aggregate above and below the layer. With the knowledge that harmful algal bloom events can occur in subsurface thin layers, modified sampling methods to monitor for these hidden incubators could greatly improve the efficacy of early-warning systems designed to detect harmful algal blooms in coastal waters.

Diversity and Seasonal Distribution of Plankton in Khaste Lake, Lekhnath, Kaski, Nepal

Planktons are the important components of aquatic ecosystem. In this study, we assessed the diversity and seasonal distribution of planktons in Khaste Lake, Lekhnath, Kaski. Samples were collected from three stations from April to September using plankton net of mesh size 60μm.The collection period included three different seasons: summer, early monsoon and late monsoon. Altogether 35 genera of plankton, 24 belonging to phytoplanktonic group and 11 to zooplankton, were recorded from April to September 2012. The recorded phytoplankton belonged to four classes namely chlorophyceae, bacillariophyceae, xanthophyceae, and cyanophyceae with fourteen, seven, two and one genera respectively, while zooplanktons belonged to three groups namely rotifera, cladocera and copepoda with three, six and two genera respectively. The dominant class in phytoplankton was chlorophyceae with fourteen genera and in zooplankton was cladocera with six genera. Eleven genera of phytoplankton and five genera of zooplankton were recorded throughout the three seasons of the study period. The rich in diversity of phytoplankton shows high level of nutrient status and the lake changing into Eutrophication Lake resulting from the surface run-off water with fertilizers from agricultural lands and sewage from densely populated area of the surrounding.

Spatial Distribution of Plankton in Citanduy River, Cisayong Region, Tasikmalaya, West Java

The Cisayong area of ​​Tasikmalaya Regency is an area that is passed by the Citanduy River. The condition of the waters in the Citanduy River in Cisayong area, has received various waste inputs which will affect the quality of the river waters and cause a decrease in water fertility. Plankton can be used as an indicator of water fertility. This study aims to determine the spatial distribution of plankton in the Citanduy River, Cisayong Tasikmalaya Region, West Java. This research was conducted from January 2020 to February 2020. The research stations are located in four locations which are determined based on environmental and land use factors with a sampling period span of once every seven days. This research was conducted using a survey method and the data were analyzed descriptively and comparatively. The results showed that there were 67 genera of plankton from 5 phytoplankton phyla and 4 zooplankton phyla with most of the phytoplankton groups found from the Bacillariophyceae class and the zooplankton group from the Tubulinea class. The total average abundance of phytoplankton was 11,534 ind / L and the total average abundance of zooplankton was 295 ind / L. The biological index values ​​of the average diversity and dominance of phytoplankton were 2.72 and 0.11, while the average values ​​of diversity and dominance of zooplankton were 0.92 and 0.47. The results of the plankton spatial distribution show that the fertility of the waters in Citanduy River is classified as oligotrophic for station 1 and mesotrophic waters for stations 2,3, and 4.

Automated plankton classification from holographic imagery with deep convolutional neural networks

AbstractIn situ digital inline holography is a technique which can be used to acquire high‐resolution imagery of plankton and examine their spatial and temporal distributions within the water column in a nonintrusive manner. However, for effective expert identification of an organism from digital holographic imagery, it is necessary to apply a computationally expensive numerical reconstruction algorithm. This lengthy process inhibits real‐time monitoring of plankton distributions. Deep learning methods, such as convolutional neural networks, applied to interference patterns of different organisms from minimally processed holograms can eliminate the need for reconstruction and accomplish real‐time computation. In this article, we integrate deep learning methods with digital inline holography to create a rapid and accurate plankton classification network for 10 classes of organisms that are commonly seen in our data sets. We describe the procedure from preprocessing to classification. Our network achieves 93.8% accuracy when applied to a manually classified testing data set. Upon further application of a probability filter to eliminate false classification, the average precision and recall are 96.8% and 95.0%, respectively. Furthermore, the network was applied to 7500 in situ holograms collected at East Sound in Washington during a vertical profile to characterize depth distribution of the local diatoms. The results are in agreement with simultaneously recorded independent chlorophyll concentration depth profiles. This lightweight network exemplifies its capability for real‐time, high‐accuracy plankton classification and it has the potential to be deployed on imaging instruments for long‐term in situ plankton monitoring.

Karst Lakes of Mari Chodra National Park: stratification and vertical distribution of phototrophic plankton

The characteristics of micro-scale vertical heterogeneity of physicochemical parameters, photosynthetic pigments’ content and populations of phototrophic microbial plankton in four karst lakes of the Mari-Chodra NP (rep. Mari El), the Bolshoy Kichier, Cherny Kichier, Shungaldan and the Blue Oxbow, are presented on the basis of summer surveys of 2006, 2007 and 2009. According to our data, two lakes, Shungaldan and Cherny Kichier are, meromictic waterbodies of crenogenic type; the Lake Bolshoy Kichier is holomictic with stable summer stratification and anoxic hypolimnion. The Lake Blue Oxbow occupies an intermediate position, and, apparently, is irregularly mixing. The physicochemical conditions and composition of the phototrophic plankton communities of the chemocline zone of the two previously studied lakes, Bolshoy and Cherny Kichier, have remained stable over the past 20-35 years. Significant development of anoxygenic phototrophic bacteria was found in two lakes in which data on their development were previously absent. In the bacterial plates of meromictic lakes, the concentration of bacteriochlorophyll d, the pigment of green phototrophic bacteria, reaches some mg per liter.

A machine-learning approach to modeling picophytoplankton abundances in the South China Sea

Picophytoplankton, the smallest phytoplankton (<3 µm), contribute significantly to primary production in the oligotrophic South China Sea. To improve our ability to predict picophytoplankton abundances in the South China Sea and infer the underlying mechanisms, we compared four machine learning algorithms to estimate the horizontal and vertical distributions of picophytoplankton abundances. The inputs of the algorithms include spatiotemporal (longitude, latitude, sampling depth and date) and environmental variables (sea surface temperature, chlorophyll, and light). The algorithms were fit to a dataset of 2442 samples collected from 2006 to 2012. We find that the Boosted Regression Trees (BRT) gives the best prediction performance with R2 ranging from 77% to 85% for Chl a concentration and abundances of three picophytoplankton groups. The model outputs confirm that temperature and light play important roles in affecting picophytoplankton distribution. Prochlorococcus, Synechococcus, and picoeukaryotes show decreasing preference to oligotrophy. These insights are reflected in the vertical patterns of Chl a and picoeukaryotes that form subsurface maximal layers in summer and spring, contrasting with those of Prochlorococcus and Synechococcus that are most abundant at surface. Our forecasts suggest that, under the “business-as-usual” scenario, total Chl a will decrease but Prochlorococcus abundances will increase significantly to the end of this century. Synechococcus abundances will also increase, but the trend is only significant in coastal waters. Our study has advanced the ability of predicting picophytoplankton abundances in the South China Sea and suggests that BRT is a useful machine learning technique for modelling plankton distribution.

Complex Analysis of the Plankton Community of two Brown-Water Bog Lakes in the European Part of Russia

The composition and vertical distribution of plankton of two polyhumic bog lakes on the territory of the Volga-Kama State Natural Biosphere Reserve were studied. It was found that the anaerobic conditions were formed in the water column at a depth deeper than 2 m due to stratification and lack of light. Phyto- and zooplankton (including ciliates) prevailed in the upper aerobic layers of water, heterotrophic bacteria and green sulfur bacteria (Chlorobiaceae) – in the anaerobic zone. Rotifers dominated the metazooplankton in the whole water column (>95% of the biomass); prevailing genera were Asplanchna, Polyarthra, and Bipalpus. Heterotrophic organisms formed 70 ± 10% of the plankton biomass in both lakes. A high proportion of ciliates (on average 3%, maximum up to 18%) and heterotrophic bacteria (on average 49 ± 25%) was also revealed. The invasive species algae Gonyostomum semen (Raphidophyta) was first registered in the lakes of the Republic of Tatarstan. It formed 28-80% of the phytoplankton biomass in the studied lakes. It was found that at least one of the ciliate species (Frontonia cf. leucas) is able to feed on G. semen cells in situ.

Exploring the hydrography of the boreal/arctic domains of North Atlantic seas: Results from the 2013 BASIN survey

In May–June 2013, the RV G.O. Sars surveyed the Norwegian, Iceland, Irminger, and Labrador seas in the North Atlantic to explore distributions of plankton and pelagic/mesopelagic fish as part of the Euro-BASIN (Basin-scale Analysis, Synthesis, and INtegration) Project. From temperature and salinity measurements collected along the ship's track, we present and compare the hydrography of the different basins using water mass analyses. In addition, we place these 2013 data into a long-term perspective by examining the historical data in these seas and exploring their variability. From the 2013 hydrographic data, we estimate the mixed layer depth at each station. During the 2013 survey, we confirmed that all four seas are influenced through advection from the south by North Atlantic Water and from the north by water originating from the Arctic but by different amounts. The 2013 data are consistent within the previously observed range of hydrographic variability. During the duration of the cruise, the mixed layer depth shallowed significantly in the Norwegian, Iceland, and Irminger seas due likely to a combination of atmospheric heat exchanges and advective changes. The largest and most consistent difference between the basins was in the deep water (>1000 m) with the Norwegian/Iceland basins containing colder, fresher waters than the Irminger/Labrador basins. Oxygen data collected during the survey and their relationship with the hydrographic structure are also discussed. The hydrographic data in this paper were used in the several of the following papers in this special issue to show their impact on the ecology of the four basins.

Fine-scale larval fish distributions and predator-prey dynamics in a coastal river-dominated ecosystem

River plumes discharging into continental shelf waters have the potential to influence the distributions, predator-prey relationships, and thus survival of nearshore marine fish larvae, but few studies have been able to characterize the plume environment at sufficiently fine scales to resolve the underlying mechanisms. We used a high-resolution plankton imaging system and a sparse convolutional neural network to automate image classification of larval fishes, their planktonic prey (calanoid copepods), and gelatinous planktonic predators (ctenophores, hydromedusae, and siphonophores) over broad spatial scales (km) and multiple pulses of estuarine water exiting Mobile Bay (Alabama, USA) into the northern Gulf of Mexico from 9-11 April 2016. Fine-scale (1 m) plankton distributions were examined to analyze predator-prey relationships across 3 distinct plume regimes that varied by degree of wind-forcing and mixing rates. In calm wind conditions, the water column was highly stratified, and fish larvae and zooplankton were observed aggregating in a region of river plume-derived hydrodynamic convergence. As winds strengthened, the water column was subjected to downwelling and highly turbulent conditions, and there was decreasing spatial overlap between larval fishes and their zooplankton prey and predators. Our results indicate that high-discharge plume regimes characterized by strong wind-forcing and turbulence can rapidly shift the physical and trophic environments from favorable to unfavorable for fish larvae. Multiple pathways for both nearshore retention and advective dispersal of fish larvae were also identified. Documenting this variability is a first step toward understanding how high discharge events and physical forcing can affect fisheries production in river-dominated coastal ecosystems worldwide.

Drivers of Plankton Distribution Across Mesoscale Eddies at Submesoscale Range

Cyclonic and anticyclonic eddies are common mesoscale features in the flow past the Canary Islands throughout the year. While drifting southwards, eddy pairs interact among them but also with upwelling filaments and eddies generated at the coastal jet of the nearby African upwelling system. These interactions force the generation of frontal zones where ageostrophic secondary circulation (ASC) may occur. With the aim of contributing to understand how meso-submesoscale interactions modulate plankton distribution, we carried out an interdisciplinary cruise across a mesoscale eddy field. The sampled region was characterized by the presence of a cyclonic eddy interacting with two anticyclonic eddies and an upwelling filament. High resolution sampling allowed us to assess the upwelling/downwelling processes associated with eddy pumping and ASC, the injection of nutrients into the euphotic zone, and the subduction of particles related to these processes. The planktonic community, which included heterotrophic bacteria, cyanobacteria-like Prochlorococcus and Synechococcus, pico and nanoautotrophic eukaryotes and heterotrophic nanoflagellates, showed a heterogeneous distribution in response to meso-submesoscale processes. Redundancy Analysis and plankton distribution suggest that while the distribution of small organisms (picoplankton) is modulated by a combination of physical and biogeochemical drivers, the distribution of larger autotrophic and heterotrophic nanoflagellates is modulated by nutrient inputs and grazing, respectively. These observational results provide new insights in the study of the impact of mesoscale structures in the dynamics of nutrients, chlorophyll and planktonic communities, valuable to validate theoretical and modeling studies.