Vertical Distribution Of Biomass Research Articles

Latitudinal variation in zooplankton over the Emperor Seamounts (34°–44° N, 170°–171° E) during the summer of 2019

During a research expedition to the Northwest Pacific between July 13 and August 11, 2019, we collected oceanic zooplankton samples over the Emperor Seamounts (Koko, Jingu, Nintoku, and Suiko guyots). We analyzed the horizontal and vertical distributions of abundance and biomass and also the structure of the zooplankton in the highly productive but poorly studied ocean waters between 34° and 44° N. The zooplankton was represented by four genera of amphipods, seven genera of pteropods, 39 genera of copepods, and larvae of benthic invertebrates and fish. The abundance and biomass of zooplankton increased towards higher latitudes along the series Koko < Jingu < Nintoku < Suiko guyots. The highest index of diversity was recorded over the Koko and Jingu guyots; the highest species richness occurred over the Jingu and Nintoku guyots. Small-sized copepods, appendicularians, chaetognaths, euphausiids, and fish eggs and larvae concentrated in the epipelagic; large copepods and ostracods concentrated in the mesopelagic. We identified three types of zooplankton assemblages: a Subtropical assemblage between 34°–35° N characterized by tropical/subtropical forms; a Transition assemblage characterized by subtropical, subarctic, and widespread species between 38°–41° N; and a Subarctic assemblage characterized by subarctic and widespread species between 43°–44° N. The spatial distribution of zooplankton was a function of environmental variables such as surface salinity, temperature at 200-m, and, to a certain extent, by surface Chl-a concentrations.

Simulating vertical distribution of normalized leaf biomass for individual Moso bamboos under intensive management

Leaf biomass is a crucial parameter that influences forest growth and carbon exchange between ecosystems and the atmosphere. A clear understanding of the vertical distribution of leaf biomass is essential for accurate carbon sequestration estimations in Moso bamboo. We collected data on leaf biomass from each crown layer and the structural characteristics of 54 individual Moso bamboo plants. We then simulated the vertical distribution of normalized upward cumulative leaf biomass (CLBn) using three power functions. The first model (Model 1) estimates CLBn using unique and unadjustable parameters (a and b) of the power function. In the second model (Model 2), parameter ‘a’ was fixed at 1, and parameter ‘b’ was fitted for all samples. In the third model (Model 3), parameter b was adjusted based on the structural characteristics of each bamboo. Model 3 demonstrated the highest accuracy in estimating CLBn and normalized leaf biomass (LBn) in each layer, with RMSEr values of 20.34 % and 36.85 % for CLBn and LBn, respectively. When compared with Model 1 and Model 2, Model 3 reduced RMSEr by 12.27 % and 6.88 % for CLBn and 21.13 % and 10.49 % for LBn, respectively. However, uncertainty remained significant in low LBn estimates from Model 3. Variations in the vertical distribution of CLBn in individual bamboo plants were primarily explained by crown length, height to the lowest living branch, and age. This study proposes a viable method for elucidating the variation in CLBn among individual bamboo plants.

Estimating the Vertical Distribution of Biomass in Subtropical Tree Species Using an Integrated Random Forest and Least Squares Machine Learning Mode

Estimating the Vertical Distribution of Biomass in Subtropical Tree Species Using an Integrated Random Forest and Least Squares Machine Learning Mode

Estimating forest height and above-ground biomass in tropical forests using P-band TomoSAR and GEDI observations

ABSTRACT Knowledge about the vertical structure of forests, such as forest height, above-ground biomass (AGB), and the vertical biomass distribution is important for understanding carbon allocation, structural diversity, and succession and degradation dynamics in forest ecosystems. While the use of lidar (light detection and ranging) observations is well established to investigate the vertical structure of forests, the sensitivity of P-band synthetic aperture radar tomography (TomoSAR) observations to biomass and vertical forest structure is not yet well understood. Here we use lidar observations from NASA’s Global Ecosystem Dynamics Investigation (GEDI) to analyse the sensitivity of airborne P-band SAR tomography backscatter to forest height and AGB at two tropical forests in Lopé and Mondah, Gabon, Africa. We use GEDI observations to parametrize an empirical model for estimating forest height and we use a random forest model for estimating AGB from TomoSAR profiles. The validation with Land, Vegetation, and Ice Sensor (LVIS) airborne lidar data shows moderate performance for estimating forest height (RMSE = 8.2 m in Lopé and 9.8 m in Mondah) and moderate to good performance for total AGB (RMSE = 115.3 Mg/ha in Lopé and 117.8 Mg/ha in Mondah). We also estimated the vertical distribution of AGB using the corrected TomoSAR backscatter and compared it with AGB profiles derived from field observations in Mondah, which indicates potential to use TomoSAR observations for estimating vertical AGB distribution over tropical forests. However, our results demonstrate the need for targeted field observations of vertical biomass profiles in order to make full use of P-band TomoSAR to map the vertical structure of tropical forests.

Insect root feeders incur negative density-dependent damage across plant species in an alpine meadow.

Although herbivores are well known to incur positive density-dependent damage and mortality, thereby likely shaping plant community assembly, the response of belowground root feeders to changes in plant density has seldom been addressed. Locally rare plant species (with lower plant biomass per area) are often smaller with shallower roots than common species (with higher plant biomass per area) in competition-intensive grasslands. Likewise, root feeders are often distributed in the upper soil layers. We hypothesized, therefore, that root feeders would incur negative density (biomass)-dependent damage across plant species. To test this hypothesis, we investigated the diversity and abundance of plant and root feeder species in an alpine meadow and determined the diet of the root feeders using metabarcoding. Across all species, root feeder load decreased with increasing aboveground plant biomass, root biomass, and total plant biomass per area, indicating a negative density dependence of damage across plant species. Aboveground plant biomass per area increased with increasing individual plant biomass and root depth per area across species, suggesting that rare plant species were smaller in size and had shallower root systems compared to common plant species. Both root biomass per area and root feeder biomass per area decreased with soil depth, but the root feeder biomass decreased disproportionately faster compared to root biomass with increasing root depth. Root feeder load decreased with increasing root depth but was not correlated with the feeding preference of root feeder species. Moreover, the prediction derived from a random process incorporating vertical distributions of root biomass and root feeder biomass significantly accounted for interspecific variation in root feeder load. In conclusion, the data indicate that root feeders incur negative density-dependent damage across plant species. On this basis, we suggest that manipulative experiments should be conducted to determine the effect of the negative density-dependent damage on plant community structure and that different types of plant-animal interactions should be concurrently examined to fully understand the effect of plant density on overall herbivore damage across plant species.

Distribution Characteristics of Carbon Density in Plant–Soil System of Temperate Steppe and Temperate Desert in the Longzhong Loess Plateau

Grassland, as a key component of the carbon cycle in terrestrial ecosystems, is vital in confronting global climate change. Characterising the carbon density of grassland ecosystems in the Longzhong Loess Plateau is important for accurately assessing the contribution of grasslands to global climate change and achieving the goal of “peak carbon” and “carbon neutral”. In this study, the Longzhong Loess Plateau was used as the research object to explore changes in the plant–soil system carbon density in two grassland types by analysing the aboveground vegetation biomass carbon density, belowground vegetation biomass carbon density, 0–100 cm soil carbon density, and ecosystem carbon density of temperate steppe and temperate desert. The results showed that the vegetation biomass (standing and living, litter, and belowground biomass), soil, and ecosystem carbon densities of the temperate steppe were significantly higher than those of the temperate desert (p &lt; 0.05). Their carbon densities were 700.51, 7612.95, and 8313.45 g·m−2, respectively. The vertical distribution of belowground biomass and soil carbon density in the temperate steppe was significantly higher than that in the temperate desert. The overall trend of belowground biomass carbon density in the temperate steppe and temperate desert showed a gradual decrease, whereas soil carbon density showed a steady increase. More than 91% and 96% of the carbon was stored in soil in the temperate steppe and temperate desert, respectively, and the belowground biomass carbon stock accounted for more than 84% of the total biomass carbon pools in both temperate steppe and temperate desert. Temperate steppe has a significant effect in improving the carbon stock of grassland ecosystems, so ecological protection and restoration of grassland should be strengthened in the future to enhance the capacity of grassland to sequester carbon and increase sinks.

Impact of critical eddy diffusivity on seasonal bloom dynamics of Phytoplankton in a global set of aquatic environments

The intensity of eddy diffusivity and the spatial average of water velocity at the depths of the water column in oceans and lakes play a fundamental role in phytoplankton production and phytoplankton and zooplankton biomass, and community composition. The critical depth and intensity of turbulent mixing within the water column profoundly affect phytoplankton biomass, which depends on the sinking characteristic of planktonic algal species. We propose an Nutrient-Phytoplankton-Zooplankton (NPZ) model in 3D space with light and nutrient-limited growth in a micro-scale ecological study. To incorporate micro-scale observation of phytoplankton intermittency in bloom mechanism in stationary as well as oceanic turbulent flows, a moment closure method has been applied in this study. Experimental observations imply that an increase in turbulence is sometimes ecologically advantageous for non-motile planktonic algae. How do we ensure whether there will be a bloom cycle or whether there can be any bloom at all when the existing phytoplankton group is buoyant, heavier, motile, or non-motile? To address these questions, we have explored the effects of critical depth, the intensity of eddy diffusivity, spatial average of water velocity, on the concentration as well as horizontal and vertical distribution of phytoplankton and zooplankton biomass using a mathematical model and moment closure technique. We quantify a critical threshold value of eddy diffusivity and the spatial average of water velocity and observe the corresponding changes in the phytoplankton bloom dynamics. Our results highlight the importance of eddy diffusivity and the spatial average of water velocity on seasonal bloom dynamics and also mimic different real-life bloom scenarios in Mikawa Bay (Japan), Tokyo Bay (Japan), Arakawa River (Japan), the Baltic Sea, the North Atlantic Ocean, Gulf Alaska, the North Arabian Sea, the Cantabrian Sea, Lake Nieuwe Meer (Netherlands) and several shallower lakes.

Linear water column stratification and euphotic depth determine the number of phytoplankton taxa that create biomass peaks in a hypertrophic oxbow lake

The mixing regime, the spatial distribution of nutrients and light determine the distribution of phytoplankton in lakes to a large extent. Linear stratification is a unique phenomenon among the various forms the lakes can stratify, representing a continuous and gradual water temperature decrease with depth. Here, we aimed to understand how mixing, nutrient and light affect the vertical distribution of phytoplankton in the case of linear water column stratification using the taxonomic and functional group approaches. We sampled phytoplankton and physical and chemical variables in the Malom-Tisza oxbow lake (Hungary) monthly from May to September between 2007 and 2009. Our results revealed that multiple biomass peaks of taxa belonging to distinct phytoplankton functional groups could develop in response to the strong linear stratification of the water column. Although several different species represented the functional groups, only one or two species developed the peaks. Light irradiance did not influence the vertical distribution of biomass and taxonomic richness of phytoplankton, but the depth of the euphotic zone determined the number of distinct biomass peaks. We found that diversity indices could not reflect the phytoplankton compositional differences well in the case of linear stratification, but similarity indices calculated among water column layers.

Mapping depth-integrated microphytobenthic biomass on an estuarine tidal flat using Sentinel satellite data

Microphytobenthos (MPB) are central to benthic tidal flat ecological networks. Large-scale information on total MPB biomass is difficult to obtain from traditional in-situ measurements. Here, we assessed the effectiveness of using surface sediment properties as proxies for predicting the total (depth-integrated) MPB biomass with Sentinel satellite data. First, the best subset regression was applied to the in-situ data to determine the properties that best predict the biomass decay rate with depth (sampling every cm up to 10 cm depth). Then, data from a controlled laboratory experiment were used to analyse the spectral response to different sediment properties (i.e., variations in sediment grain size, organic matter and water content). Subsequently, an algorithm was developed to obtain the spatial distribution of the sediment properties and the depth-integrated total MPB biomass from remote sensing data. Finally, we presented a case study in which the seasonal dynamics of total (depth-integrated) MPB biomass were obtained from Sentinel-2 Multispectral Instrument (MSI) satellite data using the Google Earth Engine (GEE) platform. The results showed that (1) the vertical distribution of MPB biomass on a tidal flat could be predicted by the surface MPB biomass, median grain-size (D50) and water content (W0) of the sediment (top 1 cm); (2) the near infrared (NIR) band absorption depth was a key feature in estimating D50 and W0; and (3) the seasonal variation in the total (depth-integrated) MPB biomass was prominent in Chongming Dongtan, Changjiang Estuary. We concluded that the depth-integrated exponential decay algorithm was useful for estimating total MPB biomass and, combined with mappable sediment-surface data, could help map the total MPB biomass in estuarine tidal flats at a large scale.

Morphology of Ascophyllum nodosum in relation to commercial harvesting in New Brunswick, Canada

Intertidal seaweed beds form three-dimensional structures providing habitat for a variety of species. As such, ecosystem-based management of seaweed harvesting must take into consideration the impact of the harvest not only on the biomass but also on the morphology of the seaweed. We compare the morphology and vertical distribution of biomass and shoots in Ascophyllum nodosum from three sites with a 20 + year history of commercial harvesting with three corresponding control sites in southern New Brunswick, Canada. We found no significant impact of harvest history on the vertical distribution of shoots or biomass within individual clumps. At two of the three harvested sites, large clumps had a wider circumference than those at the control sites, suggesting that long-term harvesting increases the growth of shoots throughout the clumps; presumably caused by an increase in light penetration through the harvested canopy. We also compare biomass of littorinids, the most abundant invertebrates found in A. nodosum beds at low tide and found no significant difference between control and harvested sites. We conclude that the harvest of A. nodosum according to the current regulations in New Brunswick, does not have long-term impact on the morphology of the algae or on the abundance of its main inhabitant.

The vertical distribution and control factor of microbial biomass and bacterial community at macroecological scales

Microorganisms exist throughout the soil profile and those microorganisms living in deeper soil horizons likely play key roles in regulating biogeochemical processes. However, the vertical differentiations of microbes along soil depth and their global biogeographical patterns remain poorly understood. Herein, we conducted a global meta-analysis to clarify the vertical changes of microbial biomass, diversity, and microbial relative abundance across the soil profiles. Data was collected from 43 peer-reviewed articles of 110 soil profiles (467 observations in total) from around the world. We found soil microbial biomass and bacterial diversity decreased with depth in soils. Among examined edaphic factors, the depth variation in soil pH exhibited significant negative associations with the depth change in microbial biomass and bacterial Shannon index, while soil total organic carbon (TOC) and total nitrogen (TN) exhibited significant positive associations. For the major bacteria phyla, the relative abundances of Proteobacteria and Bacteroidetes decreased with soil depth, while Chloroflexi, Gemmatimonadetes, and Nitrospirae increased. We found both parallels and differences in the biogeographical patterns of microbial attribute of topsoil vs. subsoil. Microbial biomass was significantly controlled by the soil nutrient concentrations in both topsoil and subsoil compared with climatic factors, while bacterial Shannon index was significantly controlled by the edaphic factors and across latitudes or climatic factors. Moreover, mean annual precipitation can also be used as a predictor of microbial biomass in subsoil which is different from topsoil. Collectively, our results provide a novel integrative view of how microbial biomass and bacterial community response to soil depth change and clarify the controlling factors of the global distribution patterns of microbial biomass and diversity, which are critical to enhance ecosystem simulation models and for formulating sustainable ecosystem management and conservation policies.

Effect of planting density on root biomass and distribution, and soil organic carbon stock of Acacia decurrens stands in Northwestern Ethiopia

Background:The expandingAcacia decurrenswoodlots in Northwestern Ethiopia is recognized for carbon storageviaroot biomass and soil organic carbon (SOC) enhancement but its planting densities have varied considerably. This study evaluated the effect of planting density on the root biomass, SOC stock, and vertical distributions in the stands.Methods:Five planting densities (0.5 m x 0.5 m, 0.75 m x 0.75 m, 1 m x 1 m, 1.25 m x 1.25 m, and 1.5 m x 1.5 m) were replicated four times with randomized complete block design. Soil core (6.67 cm diameter) and pit (900 cm2area) methods were used to collect fine and coarse root samples within 0–50 cm soil depth (having five soil layers in 10 cm intervals), respectively. Fine root biomass samples were classified as live and dead (necromass) and further as tree and herbaceous root. All root biomass samples were washed, oven-dried, weighed, and standardized into gram per meter square (g m-2) for root biomass comparisons for each planting density and soil depth, then summed up for 0–50 cm depth as a total root biomass. The vertical distributions of fine and coarse root biomass at each depth were expressed as a percentage (in decimal) of the total root biomass (0–50 cm).Conclusions:Planting density had significant effects on root biomass, SOC stock, and root distributions (P &lt; 0.05) but inconsistent for the percentage of SOC stock at all soil layers except at 40-50 cm. PlantingA. decurrenswith high density is recommended to increase root biomass, SOC, and percentage of roots in deep soil layers. Further study is suggested for the effects of stand age on root biomass dynamics and SOC stock with large scale.

Generating Douglas-fir Breeding Value Estimates Using Airborne Laser Scanning Derived Height and Crown Metrics.

Progeny test trials in British Columbia are essential in assessing the genetic performance via the prediction of breeding values (BVs) for target phenotypes of parent trees and their offspring. Accurate and timely collection of phenotypic data is critical for estimating BVs with confidence. Airborne Laser Scanning (ALS) data have been used to measure tree height and structure across a wide range of species, ages and environments globally. Here, we analyzed a Coastal Douglas-fir [Pseudotsuga menziesii var. menziesii (Mirb.)] progeny test trial located in British Columbia, Canada, using individual tree high-density Airborne Laser Scanning (ALS) metrics and traditional ground-based phenotypic observations. Narrow-sense heritability, genetic correlations, and BVs were estimated using pedigree-based single and multi-trait linear models for 43 traits. Comparisons of genetic parameter estimates between ALS metrics and traditional ground-based measures and single- and multi-trait models were conducted based on the accuracy and precision of the estimates. BVs were estimated for two ALS models (ALSCAN and ALSACC) representing two model-building approaches and compared to a baseline model using field-measured traits. The ALSCAN model used metrics reflecting aspects of vertical distribution of biomass within trees, while ALSACC represented the most statistically accurate model. We report that the accuracy of both the ALSCAN (0.8239) and ALSACC (0.8254) model-derived BVs for mature tree height is a suitable proxy for ground-based mature tree height BVs (0.8316). Given the cost efficiency of ALS, forest geneticists should explore this technology as a viable tool to increase breeding programs’ overall efficiency and cost savings.

Vertical distribution of planktonic ostracods (Halocyprididae) in the northeastern and central South China Sea: Significance of large‐sized species in deep waters

AbstractThe vertical distribution of species richness, abundance and biomass of planktonic ostracods down to a depth of 1000 m were studied in the northeastern South China Sea (NESCS) during March and in the central South China Sea (CTSCS) during September 2016. A total of 47 species of halocyprids were identified, with 46 species recorded in the NESCS and 28 species in the CTSCS. Most of the species observed were concentrated in the mesopelagic zone (200–1000 m), but the majority of species abundance and biomass occurred in the 25 m to 300 m water column. Results of statistical analysis showed that the vertical distribution of planktonic ostracods was associated with chlorophyll a concentration and sampling depth. The high abundance and species richness of ostracods in the NESCS were probably influenced by the Kuroshio intrusion and eddies leading to high levels of chlorophyll a concentration. The biomass of large‐sized individuals with low abundance is equal to or larger than, the extremely small‐sized individuals with high abundance, particularly in deep layers. The body sizes of planktonic ostracods were found to increase from surface to deeper water layers, indicating a trend of greater body length and higher biomass of ostracods in deep sea.

Relationship between the vertical distribution of fine roots and residual soil nitrogen along a gradient of hardwood mixture in a conifer plantation

In forest ecosystems, understanding the relationship between the vertical distribution of fine roots and residual soil nitrogen is essential for clarifying the diversity-productivity-water purification relationship. Vertical distributions of fine-root biomass (FRB) and concentrations of nitrate-nitrogen (NO3 -N) in soil water were investigated in a conifer plantation with three thinning intensities (Control, Weak and Intensive), in which hardwood abundance and diversity were low, moderate and high, respectively. Intensive thinning led to the lowest NO3 -N concentration in soil water at all depths (0-100 cm) and highest FRB at shallow depths (0-50 cm). The NO3 -N concentration at a given depth was negatively correlated with total FRB from the surface to the depth at which NO3 -N concentration was measured, especially at shallow depths, indicating that more abundant fine roots led to lower levels of downward NO3 -N leaching. FRB contributed positively to nitrogen content of hardwood leaves. These findings demonstrate that a hardwood mixture in conifer plantations resulted in sufficient uptake of NO3 -N from soil by well developed fine-root systems, and translocation to canopy foliage. This study suggests that productivity and water purification can be achieved through a hardwood mixture in conifer plantations.

Phytoplankton Distributions in the Kuroshio-Oyashio Region of the Northwest Pacific Ocean: Implications for Marine Ecology and Carbon Cycle

The Northwest Pacific Ocean (NWPO) is a significant sink for atmospheric CO2 but a paucity of large-scale phytoplankton surveys in the upper and lower euphotic zone results in uncertainties in estimates of the efficiency of the biological carbon pump there. Here, we report the spatial distribution of lipid biomarkers from diatoms (brassicasterol/epi-brassicasterol), dinoflagellates (dinosterol), and haptophytes (C37 alkenones) as proxies of phytoplankton biomass and community structure in suspended particles from the surface and deep chlorophyll maximum (DCM) layers across low- and mid-latitude regions of the NWPO. Our observations suggest that these lipid biomarkers can be used as indicators of the vertical distributions of phytoplankton biomass, which was comparable between the surface and DCM layers. Water masses with different nutrient concentrations strongly controlled the variations of lipid biomarkers, showing high biomass and the dominance of diatoms in the eutrophic Oyashio region, whereas low biomass and high proportions of dinoflagellates and haptophytes occurred in the oligotrophic Kuroshio region. Diatoms predominated in the DCM, likely enhancing carbon sequestration in the deep ocean and in sediments. Our results quantitatively demonstrate the horizontal and vertical variations of phytoplankton biomass and community structure, leading to an improved understanding of ecosystem function and biogeochemical cycles in this important region of the NWPO.

Carbon remineralization by small mesopelagic and bathypelagic Stomiiforms in the Northeast Atlantic Ocean

The organic carbon resulting from photosynthesis in the upper ocean is transferred downward through the passive sinking of organic particles, physical mixing of particulate and dissolved organic carbon as well as active flux transported by zooplanktonic and micronektonic migrants. Several meso- and bathypelagic organisms feed in shallower layers during the nighttime and respire, defecate, excrete and die at depth. Recent studies suggest that migrant micronekton transport similar amounts of carbon to migrant zooplankton. However, there is scarce information about biomass and carbon flux by non-migratory species in the mesopelagic and bathypelagic zones. The non-migratory bristlemouth fishes (Cyclothone spp.) and partial migrator (A. hemigymnus) remineralise organic carbon at depth, and knowledge about this process by this fauna is lacking despite them having been referred to as the most abundant vertebrates on Earth. Here we show the vertical distribution of biomass and respiration of non-migratory mesopelagic fishes, during day and night, using the enzymatic activity of the electron transfer system (ETS) as a proxy for respiration rates. The study is focused on five Cyclothone species (C. braueri, C. pseudopallida, C. pallida, C. livida and C. microdon) and Argyropelecus hemigymnus. The samples were taken on a transect from the oceanic upwelling off Northwest Africa (20° N, 20° W) to the south of Iceland (60° N, 20° W). Cyclothone spp. showed, by far, the largest biomass (126.90 ± 86.20 mg C·m−2) compared to A. hemigymnus (0.54 ± 0.44 mg C·m−2). The highest concentrations of Cyclothone spp. in the water column were observed between 400 and 600 m and from 1000 to 1500 m depths, both during day and night. For the different species analysed, ETS activity did not show significant differences between diurnal and nocturnal periods. The total average specific respiration of Cyclothone spp. (0.02 ± 0.01 d-1) was lower than that observed for A. hemigymnus (0.05 ± 0.02 d-1). The average carbon respiration of Cyclothone spp. was 2.22 ± 0.81 mg C·m−2·d-1, while it was much lower for A. hemigymnus (0.04 ± 0.03 mg C·m−2·d-1). The respiration of Cyclothone spp. was lower in the bathypelagic than in the mesopelagic zone (0.84 ± 0.48 vs 1.36 ± 1.01 mg C·m−2·d-1, respectively). These results, to our knowledge, provide the first account of remineralisation by this community in the meso and bathypelagic zones of the ocean.

Variability of hydrographic factors, biomass and structure of the phytoplankton community at the entrance to the Gulf of California (spring 2013)

This study reports observations of the horizontal and vertical variation of chlorophyll a (Chla) and the taxonomic composition of phytoplankton at the entrance to the Gulf of California (GC) and its relationship with physicochemical processes. This region is part of the northern boundary of one of the largest shallow Oxygen Minimum Zones in the world, characterized by marked physicochemical gradients. Therefore, understanding the prevailing seasonal patterns and their relationship with primary producers is considered particularly relevant. The study period, April 2013, was characterized by mesoscale eddies and fronts associated with several water masses (California Current Water - CCW, Gulf of California Water - GCW, and Subtropical Subsurface Water - StSsW), which influenced the horizontal and vertical distribution of Chla between 0 and 150 m. Superficial southward flow of CCW was observed near the west coast of Baja California, turning toward the GC flowing between 30 and 60 m depth. At the entrance to the GC, the currents circulated anticyclonically, flowing into the GC near Baja California, while GCW flowed out of the GC near the mainland coast. The vertical distribution of Chla featured a subsurface maximum layer (SCML) associated with the 25 kg m-3 isopycnal, highlighting the importance of stratification processes as drivers of the vertical distribution of phytoplankton biomass. In turn, this favored different associations of phytoplankton groups. In surface waters, the phytoplankton community was dominated by picocyanobacteria (Synechococcus and Prochlorococcus) and Prymnesiophytes, while at the SCML, Prymnesiophytes coexist mainly with Prasinophytes, Chrysophytes, and Cryptophytes. The prevalence of these flagellates (and the absence of autotrophic dinoflagellates) suggests the importance of a multivorous food web in this region, typical of environments where carbon recycling predominates in the pelagic zone. Diatoms made no significant contribution to Chla, although their abundance increased in the SCML associated with the influence of the CCW. The low N:P (8.3) and Si:N (0.86) ratios indicate that nitrates and silica are potentially limiting nutrients for the development of this group.

Seasonal and diel variations in the vertical distribution, composition, abundance and biomass of zooplankton in a deep Chilean Patagonian Fjord.

Comau Fjord is a stratified Chilean Patagonian Fjord characterized by a shallow brackish surface layer and a >400 m layer of aragonite-depleted subsurface waters. Despite the energetic burden of low aragonite saturation levels to calcification, Comau Fjord harbours dense populations of cold-water corals (CWC). While this paradox has been attributed to a rich supply of zooplankton, supporting abundance and biomass data are so far lacking. In this study, we investigated the seasonal and diel changes of the zooplankton community over the entire water column. We used a Nansen net (100 µm mesh) to take stratified vertical hauls between the surface and the bottom (0-50-100-200-300-400-450 m). Samples were scanned with a ZooScan, and abundance, biovolume and biomass were determined for 41 taxa identified on the web-based platform EcoTaxa 2.0. Zooplankton biomass was the highest in summer (209 g dry mass m−2) and the lowest in winter (61 g dry mass m−2). Abundance, however, peaked in spring, suggesting a close correspondence between reproduction and phytoplankton spring blooms (Chl a max. 50.86 mg m−3, 3 m depth). Overall, copepods were the most important group of the total zooplankton community, both in abundance (64–81%) and biovolume (20–70%) followed by mysids and chaetognaths (in terms of biovolume and biomass), and nauplii and Appendicularia (in terms of abundance). Throughout the year, diel changes in the vertical distribution of biomass were found with a daytime maximum in the 100–200 m depth layer and a nighttime maximum in surface waters (0–50 m), associated with the diel vertical migration of the calanoid copepod family Metridinidae. Diel differences in integrated zooplankton abundance, biovolume and biomass were probably due to a high zooplankton patchiness driven by biological processes (e.g., diel vertical migration or predation avoidance), and oceanographic processes (estuarine circulation, tidal mixing or water column stratification). Those factors are considered to be the main drivers of the zooplankton vertical distribution in Comau Fjord.

Modification and upscaling of S–W model based on vertical distributions of soil moisture and vegetation root biomass

Soil water is the dominant factor controlling evapotranspiration (ET) in arid and semi-arid regions. However, the widely used ET simulation models, such as the Shuttleworth-Wallace model (S–W model), are insufficient in simulating the direct influence of soil moisture (SM), especially in the root zone. Based on SM and ET field data, we found that the influence of SM on ET increased with soil depth in the grassland. Evaporation in the S–W model was optimized by SM at 0–5 cm as the root mean square error (RMSE) decreased from 1.4 to 0.17, while transpiration was optimized by SM at 10–20 cm as the RMSE decreased from 0.26 to 0.07. The modified S–W model incorporating SM was called the S–W-ϴ model. To up-scale application and to verify the accuracy of the S–W-ϴ model under watershed water balance, we replaced the ET simulation module based on the S–W model with our S–W-ϴ model and the Block-wise TOPMODEL with Muskingum-Cunge routing method (BTOPMC) model that we used as the basis of our simulation. The influence of SM was determined by the proportion of root biomass of different vegetation types at different depths, and each depth interval was assigned a weighting reflecting its degree of influence. The results showed that the S–W-ϴ model improved accuracy with all the modification schemes tested. The modification scheme determined by the vegetation root distribution pattern had the greatest effect, providing a 4% accuracy improvement. The modified ET and hydrological models have the potential to support water basin management to a greater extent.