Vertical Distribution Patterns Research Articles

Determination of the Vertical Distribution Pattern of Indoor Climate Parameters in the Greenhouse Heated in the Winter Period

Determination of the Vertical Distribution Pattern of Indoor Climate Parameters in the Greenhouse Heated in the Winter Period

Partial replacement of chemical fertilizer by manure affects maize root traits in North China Plain

AbstractIn order to achieve high yields and environmental friendliness simultaneously, the replacement of chemical fertilizers by manure has become a research hotspot in recent years. Roots absorb nitrogen, participate in its assimilation and contribute to the cereal's dry matter accumulation. A 5‐year filed experiment in the North China Plain was initiated to assess the response of root morphology and distribution of summer maize (Zea mays L.) to fertilizer application and contribution to crop yield. The treatments included CK (unfertilized control), NPK (inorganic nitrogen/phosphorus/potassium fertilizer) and NPKM (manure + 70% NPK). We determined the root biomass, root diameter, root length density (RLD) of three diameters (>0.8 mm, 1stRLD; 0.2–0.8 mm, 2ndRLD; <0.2 mm, 3rdRLD) and the soil chemical properties at 60 cm with 10 cm increments. At 40–60 cm, NPKM significantly decreased the root diameter than NPK. Fertilization showed no effect on total RLD, 1stRLD, 2ndRLD and 3rdRLD for a 60‐cm soil profile. At 40–50 cm, the NPKM increased the RLD compared to NPK, mainly by increasing the 2ndRLD and 3rdRLD. Under CK and NPK, root lengths of 0–20 cm made up 62% and 57% of the total root length, respectively. Under NPKM, root lengths of 40–60 cm made up 46% of the total root length. Our results indicate that maize yield was preserved after replacing 30% of N fertilizer with manure, presumably depending on the change of root vertical distribution pattern and increase of the fine root length in deeper soil.

The vertical pollution structure reflected by aerosol optical properties in Beijing and its relation with meteorological conditions in the autumn and winter of 2017–2020

The high temporal aerosol optical extinction vertical profiles observed by LiDAR in Beijing and its vicinity areas (BIV) in autumn and winter from October 2017 to February 2020 are investigated in this study. Through the clustering analysis using the machine learning, we separate and distinguish the clean conditions and aerosol pollution convergence situations at different altitudes, obtain six vertical aerosol pollution distribution patterns, and discuss the differences in the diurnal variation. Patterns with the entire clean layer are the typical category, accounting for 81.4% of the overall percentage. The patterns with pollution convergence at different heights at the top and above the boundary layer and in the lower and middle parts of the boundary layer account for 11.9% and 6.7%, respectively. The relationship among vertical pollution structure, the meteorological elements, and the near-surface PM2.5 mass concentration are discussed. Pollution convergences are mainly affected by northward aerosol pollution transport. Significant humidification and temperature inversion show aerosol pollution's influence on regional meteorological conditions. The heavy near-surface PM2.5 mass concentration is only related to the category with the aerosol pollution convergence in the lower and middle boundary layer when the high values of the PLAM index (parameters linking air quality to meteorological elements), which quantifies the regional air mass stability, and the boundary layer height (BLH) appear. Other aerosol pollution convergences above the boundary layer cannot reflect in the near-surface PM2.5 mass concentration. The pollution and associated meteorological conditions near the surface are more severe in the evening than in the morning. Regional unfavorable meteorological conditions contributed 47% and 62% to surface pollution in the morning and evening, respectively. Pollution transport and the two-way feedback jointly control the near-surface aerosol pollution in the morning; The unfavorable meteorological conditions may play a dominant role in the evening.

Recent Changes in Composition and Distribution Patterns of Summer Mesozooplankton off the Western Antarctic Peninsula

The Southern Ocean has undergone significant climate-related changes in recent decades. As a result, pelagic communities inhabiting these waters, particularly mesozooplankton, have adapted to new conditions. The present study considers the patterns of horizontal and vertical (up to 1000 m) distribution, the composition, abundance, and biomass of mesozooplankton, and the relationships of these parameters to the extreme environmental conditions off the western Antarctic Peninsula throughout the record-warm austral summer season of 2022. Sampling was conducted using the opening/closing Multinet system (0.25 m2 aperture) equipped with five 150-μm mesh nets and a WP-2 net. The mesozooplankton was represented by the three most abundant groups: eggs and larvae of euphausiids such as Euphausia superba, small copepods such as Oithona similis, and large calanoid copepods such as Calanoides acutus, Calanus propinquus, Metridia gerlachei, and Rhincalanus gigas. The composition and quantitative distribution of the mesozooplankton significantly varied: the copepods were abundant in the west, off the Antarctic Peninsula, while eggs and larvae of euphausiids were abundant in the east, off the South Orkney Islands. Most mesozooplankton occurred in the upper 200 m layer, and each taxon showed characteristic depth preference: small copepods, euphausiids larvae, and cirripeds cypris larvae were abundant in the epipelagic layer, while large calanoid copepods, euphausiids eggs, amphipods, pelagic polychaetes, and ostracods were found mostly in the mesopelagic layer. The composition and quantitative distribution of mesozooplankton had clear relationships with environmental factors, particularly with a combination of variables such as water salinity, temperature, and chlorophyll a concentration.

Interspecific differences in the vertical distribution patterns of Sebastes inermis and S. ventricosus

Interspecific differences in the vertical distribution patterns of Sebastes inermis and S. ventricosus

Seasonal shifts in diel vertical migrations by lake‐dwelling coastal cutthroat trout, Oncorhynchus clarkii clarkii, reflect thermal regimes and prey distributions

AbstractLakes provide important habitat for salmonids that may use them as a primary feeding area between periods of reproduction. The seasonal changes in vertical thermal structure in lakes can affect the distribution of salmonids on seasonal and diel time scales as they search for, consume, and digest prey that also exploits the water column's distribution of food, temperature and light. Our goal was to analyse the vertical distribution of wild, native coastal cutthroat trout (Oncorhynchus clarkii clarkii) in Lake Washington on daily and seasonal time scales. This lake is stratified in the summer and isothermal in winter, allowing us to compare vertical movements between periods with and without thermal structure in water 50 m deep. We predicted that trout would be deeper in the water column during stratified months and shallower during isothermal months, and shallower at night than in the day. Overall, the trout showed these patterns in the depths and temperatures they occupied, tending to be within or below the thermocline in the summer but not in the coolest water available, and closer to the surface when the lake was isothermal. The trout were also closer to the surface at night and deeper during the day. The vertical range of these diel movements shifted with the seasons–deepest in October, as the thermocline deepened and weakened, and shallowest in January when the lake was isothermal. These seasonal and diel vertical distribution patterns by the trout optimise metabolism for growth, and facilitate feeding on planktivorous fishes that also show seasonal and diel vertical distribution changes.

Inhomogeneous antibiotic distribution in sediment profiles in anthropogenically impacted lakes: Source apportionment, fate drivers, and risk assessment

Antibiotic residues in lake ecosystems have been widely reported; however, the vertical distribution of antibiotics in lake sediment profiles have rarely been examined. This study systematically revealed the vertical distribution pattern, sources, and risks of antibiotics in sediments of four typical agricultural lakes in central China. Nine of 33 target antibiotics were detected with a total concentration range of 39.3–18,250.6 ng/g (dry weight), and the order of average concentration was erythromycin (1447.4 ng/g) > sulfamethoxazole (443.7 ng/g) > oxytetracycline (62.6 ng/g) > enrofloxacin (40.7 ng/g) > others (0.1–2.1 ng/g). The middle-layer sediments (9–27 cm) had significantly higher antibiotic detected number and concentration than those in the top layer (0–9 cm) and bottom layer (27–45 cm) (p < 0.05). Correlation analysis showed that significant relationships existed between antibiotic concentrations and the octanol–water partition coefficients (Kow) of antibiotics (p < 0.05). Redundancy analysis indicated that Pb, Co, Ni, water content, and organic matter (p < 0.05) jointly affected the distribution of antibiotics in sediment profiles. Risk assessment showed that the highest potential ecological and resistance selection risks of antibiotics occurred in the middle-layer sediments, and oxytetracycline, tetracycline, and enrofloxacin had the most extensive potential risks in the sediment profiles. Additionally, the positive matrix factorization model revealed that human medical wastewater (54.5%) contributed more antibiotic pollution than animal excreta (45.5%) in sediment. This work highlights the inhomogeneous distribution of antibiotics in sediment profiles and provides valuable information for the prevention and control of antibiotic contamination in lakes.

Investigation of dynamic change in microplastics vertical distribution patterns: The seasonal effect on vertical distribution

This paper analyzes the variability of microplastics vertical distributions in the oceanic water column. Data were obtained from targeted sampling in the Bay of Marseille (France) and from a numerical simulation forced by realistic physical forcings. By fitting model and in-situ data in a simplified vertical dimension, three microplastics classes may be deduced: settling, buoyant and winter neutrally-buoyant microplastics. Buoyant microplastics are mainly concentrated at the surface but they can be mixed throughout the whole water column during episodes with strong winds and no water stratification, inducing an implicit underestimation of buoyant microplastics in surface sampling. Almost symmetrical to the distribution of buoyant microplastics, settling microplastics are mainly found at the bottom but they can sometimes reach the surface under the mixing conditions cited above. They could thus contribute to surface sampling. Winter neutrally-buoyant microplastics are more homogenously mixed during the winter but are under the stratified layers during summer.

Spray coverage profiles from pecan air-blast sprayers, with a radial air-flow and a volute-generated focused air-flow, as affected by forward speed and application volume

Pecan (Carya illinoinensis) is an important specialty crop in the U.S.A., but yield is limited by several diseases and pests. In mature-tree pecan orchards, large air-blast sprayers are commonly used to apply the pesticides to control these diseases and pests. The spray coverage, deposition and profiles are poorly defined under the range of application scenarios, limiting the recommendations that can be provided to growers to maximize control while minimizing input costs. To explore effects of sprayer setting parameters such as travel speed and spray volume rate on spray coverage on tall targets we set up a system (a simple vertical patternator) using a 19-m-tall pole with cards attached at eight height levels from 5 to 19 m above ground, allowing to determine the vertical distribution pattern of two air-blast sprayers with different air discharge systems. Spray was applied with a standard radial-flow air-blast sprayer during six treatments being combinations of two travel speeds: 2.4 and 3.2 km/h, and three spray volume rates: 470, 940 and 1970 L/ha, as well as with a focused air-flow system (a volute) sprayer during four treatments being combinations of two travel speeds: 2.4 and 3.2 km/h, and two spray volume rates: 470 and 940 L/ha. Results show that using a standard radial air-flow sprayer, application volume affected coverage at heights ≤17 m (higher volumes resulting in more coverage). Higher speed using a standard radial air-flow sprayer resulted in greater spray coverage, but was inconsistent with the focused air-flow system. Using a focused air-flow system more spray coverage occurred at >17 m compared to a standard radial air-flow sprayer. Spray coverage profiles affirmed the rapid decline in coverage with height using a standard radial air-flow sprayer. The results may help guide decisions on volute use, spray volume, and spray partitioning to different parts of the canopy to improve spray profile characteristics for applying more uniform spray coverage to mature pecan tree canopies.

Vertical migration patterns linked to body and environmental temperatures in chub mackerel

Fishes in the genus Scomber are currently one of the most abundant, economically important, and widely distributed fishes in the North Pacific and North Atlantic Oceans. This study recorded the depth, peritoneal and environmental temperature of the chub mackerel Scomber japonicus using an electronic tag. The 176 tagged mackerel were released from Tsushima Strait, Japan. A total of 1,075 days of data from November to August were obtained from seven individuals. Mackerel extensively used the epipelagic zone, and ranges of depth and environmental temperature during the overall recording period were 0.5–213 m and 3.4–29.1 °C, respectively. The mean depth during the day was deeper than that observed during the night in the foraging season. This vertical distribution pattern of the mackerel may overlap with that of prey organisms. We also observed a unique short-term vertical migration of mackerel during the foraging season. When the mackerel repeated the short-term vertical migrations, ranges of peritoneal temperature (13.9–15.0 °C) were narrower than environmental temperature (7.9–16.5 °C). This behavior allowed the mackerel to use physiologically unsuitable thermal layers, while avoiding overcooling of body temperature. However, these vertical migration patterns broke down in the spawning season. Behavioral decisions of diel vertical migration in chub mackerel may be affected by body condition of individual fish such as maturation states. Quantifying vertical migrations of Scomber species occupying intermediate trophic levels is important when considering conservation strategies of more than simply fisheries stock but also that of marine ecosystems.

Benthic biogeographic patterns on the deep Brazilian margin.

The Brazilian continental margin (BCM) extends from the Tropical to the Subtropical Atlantic Ocean, with much of its seafloor within deep waters, supporting rich geomorphological features and under wide productivity gradients. Deep-sea biogeographic boundaries on the BCM have been limited to studies that used water mass and salinity properties of deep-water masses, partly as a result of historical under sampling and a lack of consolidation of available biological and ecological datasets. The aim of this study was to consolidate benthic assemblage datasets and test current oceanographic biogeographical deep-sea boundaries (200-5,000 m) using available faunal distributions. We retrieved over 4,000 benthic data records from open-access databases and used cluster analysis to examine assemblage distributions against the deep-sea biogeographical classification scheme from Watling et al. (2013). Starting from the assumption that vertical and horizontal distribution patterns can vary regionally, we test other schemes incorporating latitudinal and water masses stratification within the Brazilian margin. As expected, the classification scheme based on benthic biodiversity is in overall agreement with the general boundaries proposed by Watling et al. (2013). However, our analysis allowed much refinement in the former boundaries, and here we propose the use of two biogeographic realms, two provinces and seven bathyal ecoregions (200-3,500 m), and three abyssal provinces (>3,500 m) along the BCM. The main driver for these units seems to be latitudinal gradients as well as water mass characteristics such as temperature. Our study provides a significant improvement of benthic biogeographic ranges along the Brazilian continental margin allowing a more detailed recognition of its biodiversity and ecological value, and also supports the needed spatial management for industrial activities occurring in its deep waters.

Diverse patterns of larval coral reef fish vertical distribution and consequences for dispersal and connectivity

Diverse patterns of larval coral reef fish vertical distribution and consequences for dispersal and connectivity

Trapped microplastics within vertical redeposited sediment: Experimental study simulating lake and channeled river systems during resuspension events

Plastic waste and its fragments (microplastics; <5 mm) have been observed in almost all types of environments. However, the mechanisms underlying the flow and transport processes of plastics are unknown. This is particularly valid for river sediments, where complex interactions occur between particles and influence their vertical and horizontal distribution patterns. In this study, we investigated the vertical redistribution of 14 pristine microplastics (MPs) with different densities, sizes, and shapes within disturbed sediment without lateral transport (i.e., low-velocity flow). MPs were spiked into sediments (height: 8 cm) in a column with a height of 1 m (diameter: 6 cm) filled to the top with water. The sediment was perturbed by turning the column upside-down to simulate remobilization and the subsequent deposition of sediment. After the complete sedimentation of the particles, the water column was filtered and the sediment was cut into vertical sections. MPs were then extracted from the sediment using sieves and a density separation method, and were counted under a stereomicroscope. Low-density polymers were mainly recovered in the water column and at the surface of the sediment, whereas high-density polymers were found within all sediment sections. The vertical distribution of high-density polymers changes primarily with the sediment grain size. The distribution of each polymer type changes depending on the size and/or shape of the particles with complex interactions. The observed distributions were compared with the expected distributions based only on the vertical velocity formulas. Overall, the formulas used did not explain the sedimentation of a portion of low-density polymers and predicted a lower distribution in the sediment than those observed in the experiment. In conclusion, this study highlights the importance of considering MPs as multi-dimensional particles and provides clues to understand their fate in low-velocity flow systems, considering that they undergo scavenging in sediments.

Vertical distribution patterns of zooplankton across a gradient of fish predation in boreal lakes

Abstract Different physical factors such as solar radiation and wind impose strong vertical gradients in lake water columns and have important consequences on the distribution of aquatic organisms, from bacteria to fish. The heterogeneous vertical distribution of zooplankton in lakes is a clear example of a pattern related to these vertical gradients. Although the vertical distribution of zooplankton is probably controlled by multiple factors including light, resources, and predation, we still lack an integrated view of the interplay among these potential drivers, which are most often analysed separately. Moreover, most studies focussed on temperate lakes in which both phytoplankton resources and predation risk from fish are highest in the epilimnion, whereas only a few investigated boreal lakes, where phytoplankton is often more abundant in the metalimnion than in the epilimnion and cold‐stenothermic fishes prey on zooplankton below the warm epilimnetic layers. Here we investigated zooplankton vertical distribution in the epi‐ and metalimnetic waters of 17 boreal lakes that varied in fish predation, resource quantity and quality, and optical properties. The lakes were sampled at midday and midnight at five different depths in the well‐lit epi‐ and metalimnetic layers, where the strongest gradient in light (and predation risk) were expected. We used a multi‐model inference approach combined with linear modelling to examine the relative effects of physical factors (light attenuation, temperature and moon phase), resources (chlorophyll‐a and polyunsaturated fatty acids), and predation (fish and Chaoborus) on depth selection in four zooplankton taxa. All taxa showed a heterogeneous vertical distribution that in most cases had a clear diel migration pattern. Both predation and resources (food and temperature gradient) were associated with vertical depth selection by zooplankton, but each taxon had different responses to each factor. Vertebrate predators were associated with the vertical distribution of Daphnia, Calanoida, and Cyclopoida, but—unexpectedly—all these taxa reduced their diel vertical migration patterns in the presence of fish. Invertebrate predators were better correlated with the distribution of Cyclopoida, which tended to be shallower when Chaoborus was abundant. Food abundance seemed important for Holopedium glacialis and Calanodia, while the temperature gradient was partly associated with both Daphnia spp. and Calanoida distribution. Finally, we found an intriguing, albeit weak, positive association between the vertical distribution of Cyclopoida and that of food quality. These results showed that taxa less vulnerable to predators such as H. glacialis perform inverse DVM, and that this is at least partly related to moon phase rather than to fish predation. They also suggest that boreal lakes colonised by stenothermic planktivorous fish behave differently from the classical DVM paradigm, given that visual predators do not have access to fully lit layers.

Permafrost Affected Soils of the Alazeya River Basin: Properties, Mineralogy and Classification

Physico-chemical properties and vertical distribution patterns of clay minerals in the weakly differentiated soils were studied. The soils are located in the Kolyma lowland plain; they have formed in a cold and ultracontinental climate. The study objects cover a broad range of the landscape diversity: the marsh and alas meadows and typical northern taiga landscapes. Despite the fact that weathering processes are weakly developed at high latitudes, mineral transformation represented by chlorite-illite association led to presence of (i) vermiculite in the acidic soil horizons of the alas meadow and the zonal northern taiga landscapes and (ii) iron hydroxide – lepidocrocite in the profile from the marsh meadow. It was shown that classification of the Kriozem located in the open woodland landscapes that are typical in the northern taiga does not cause difficulties based on the profile-genetic approaches of the national classification system. Oppositely, classification of the permafrost affected soils located in the intrazone landscapes of the marsh and alas meadows should be further clarified.

New insight into Salpa thompsoni distribution via glider-borne acoustics

Salpa thompsoniis an ephemerally abundant pelagic tunicate in the waters of the Southern Ocean that makes significant contributions to carbon flux and nutrient recycling in the region. WhileS. thompsoni, hereafter referred to as “salps”, was historically described as a polar-temperate species with a latitudinal range of 40 – 60°S, observations of salps in coastal waters of the Western Antarctic Peninsula have become more common in the last 50 years. There is a need to better understand the variability in salp densities and vertical distribution patterns in Antarctic waters to improve predictions of their contribution to the global carbon cycle. We used acoustic data obtained from an echosounder mounted to an autonomous underwater Slocum glider to investigate the anomalously high densities of salps observed in Palmer Deep Canyon, at the Western Antarctic Peninsula, in the austral summer of 2020. Acoustic measurements of salps were made synchronously with temperature and salinity recordings (all made on the glider downcasts), and asynchronously with chlorophyll-ameasurements (made on the glider upcasts and matched to salp measurements by profile) across the depth of the water column near Palmer Deep Canyon for 60 days. Using this approach, we collected high-resolution data on the vertical and temporal distributions of salps, their association with key water masses, their diel vertical migration patterns, and their correlation with chlorophyll-a. While salps were recorded throughout the water column, they were most prevalent in Antarctic Surface Water. A peak in vertical distribution was detected from 0 – 50 m regardless of time of day or point in the summer season. We found salps did not undergo diel vertical migration in the early season, but following the breakdown of the remnant Winter Water layer in late January, marginal diel vertical migration was initiated and sustained through to the end of our study. There was a significant, positive correlation between salp densities and chlorophyll-a. To our knowledge, this is the first high resolution assessment of salp spatial (on the vertical) and temporal distributions in the Southern Ocean as well as the first to use glider-borne acoustics to assess salpsin situ.

Strong variations and shifting mechanisms of altitudal diversity and abundance patterns in soil oribatid mites (Acari: Oribatida) on the Changbai Mountain, China

Biological composition and structure vary strongly with elevation, however, the vertical distribution of soil fauna and its drivers have been rarely investigated. Oribatid mites play an essential role in soil faunal composition, where they can occur at high densities and mediate soil ecological processes and functions. Here, we comprehensively investigated the composition and diversity of soil oribatid mites, at nine altitudes (from 600 to 2200 m asl) and four vegetation types from forest to alpine tundra on the Changbai Mountain in July 2021. In total, 67 species were identified among 37,224 oribatid mite individuals. Oribatid mite species varied strongly with altitude and vegetation type, and only a few species overlapped between elevations. Species abundance and diversity declined significantly as altitude increased, while abundance exhibited a hump-shaped distribution along an elevational gradient, peaking at 1200 m. Beta diversity decomposition analyses revealed that species replacement processes dominated community compositional differences across all study sites (both between vegetation types and elevations). Meanwhile, soil oribatid mite community composition is greatly affected by elevation and vegetation type. Specifically, oribatid mite community varies with elevation across vegetation types. Twelve and twenty indicator species were found at different elevations and vegetation types, respectively. Our study shows that soil moisture content, total phosphorus, available phosphorus, ammonium nitrogen, and nitrate nitrogen are the most dominant drivers of oribatid mite composition patterns. These findings indicate oribatid mite assemblages have a distinct vertical distribution pattern and are coupled with different aboveground vegetation types, implying that changes in aboveground vegetation will cause shifts in soil fauna under future climate change.

Soil sulfur cycle bacteria and metabolites affected by soil depth and afforestation conditions in high-sulfur coal mining areas

This study aimed to clarify the changes in sulfur-driven microorganisms and sulfur metabolic pathways in the vertical soil profile during the restoration of different afforestation types. Soils of varying afforestation patterns (grassland, shrubland, woodland) in high‑sulfur coal mining areas (Gujiao City, China) were analysed to determine the characteristics of the sulfur distribution, microbial community structure, and sulfur metabolites in shallow (10 cm), middle (30 cm), and deep (50 cm) soils. Compared with the area without vegetation, the soil in the planted area had higher total soil S (5.1–58.6 %), Fe (37.5–67.4 %), and Cu (28.3–54.2 %); the content of these elements showed a consistent increase with depth. Afforestation resulted in increased pH by 0.8–1.3 pH units, organic carbon (1.6–2.9 times), total N (30.2–46.9 %), and available N (58.3–78.2 %) in the soil. Additionally, the electrical conductivity of the shallow soil in the three plant cover areas decreased by 78–82 %. The diversity of 16S bacterial showed that different afforestation types shaped the structure of specific microbial communities at different soil depths. Afforestation also showed a promotion of abundance of soil sulfur-related microorganisms (e.g., Desulfovibrio (0.8–34.2 %), Acidiferrobacter (0.3–32.8 %), Acidithiobacillus (1.2–21.7 %), and Thiomonas (0.6–15.6 %)). Plant cover induced the vertical spatial distribution pattern of sulfur metabolites in high-sulfur coal mines showing a shallow > middle > deep layer, and afforestation enhanced the transformation process of sulfur metabolites in shallow soil. The main metabolic pathways for soil sulfur metabolism involve sulfur-containing amino acids, such as cysteine and methionine metabolism, taurine, and hypotaurine. Interaction analysis indicated that Lysobacter, Luteimonas, and Leptospirillum made greater contributions to the changes in sulfur metabolites. The findings from this study suggest that the distribution of sulfur and soil properties in vertical depth soil of different afforestation types in high-sulfur coal mining areas recruit specific bacteria, which drive soil sulfur metabolic conversion and reestablishment of soil sulfur homeostasis, and the shallow layers of the soil were critical areas for turnover of sulfur metabolite. These results provide insights for understanding biochemical sulfur cycling in vertical soil depth under different afforestation models.

Appendicularians and marine snowin situvertical distribution in Argentinean Patagonia

AbstractDetailed 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.

Role of height and position in the vertical distribution pattern of urban surface-deposited sediments and associated heavy metals

Urban surface-deposited sediments (USDs) with different spatial positions and heights are a mixture of various pollutants with complex sources and are widely distributed in urban environments.