scholarly journals Variable predator–prey relations in zooplankton overwintering in Subarctic fjords

2020 ◽  
Author(s):  
Stig Skreslet ◽  
Marina Espinasse ◽  
Ketil Olsen ◽  
Boris D. Espinasse
Keyword(s):  
Standing Stock ◽  
Species Abundance ◽  
Spatial Density ◽  
Predator Prey ◽  
Trophic Activity ◽  
Basin Scale ◽  
Atlantic Origin ◽  
Scale Population ◽  
Stock Abundance

Zooplankton predator–prey relations in northern Norwegian fjords are highly variable in time and space, and the mechanisms driving this variability are still poorly understood. Replicate Juday net sampling in October and February from 1983 to 2005, which included five repeated tows from bottom to surface, was conducted in Saltfjord and Mistfjord, northern Norway. The time-series provided evidence of in situ variability in species abundance, as well as seasonal and interannual changes in standing stock abundance. The shallow sill of one fjord caused accumulation of coastal water in the fjord’s basin, while the other fjord’s deeper sill selected denser water of Atlantic origin from the same open shelf habitat. The selective advection caused differences in the immigration of species recruiting to the fjords’ specific overwintering communities of zooplankton. Statistical analyses of the cumulated replicate data indicated significant in situ variability in the spatial density of species. Cases with an abundance of carnivores relating positively to other species probably resulted from the carnivores’ attraction to patches with concentrations of prey. Interspecific negative density relations likely indicated either predator avoidance or substantial trophic activity during the sampling. During years of high abundance, some wintering stocks of carnivores evidently reduced the local stocks of overwintering prey. We conclude that predator–prey interactions and stock variability in Subarctic fjords result from complex bio-geophysical interactions that occur on the scales of local habitats and basin-scale population systems.

scholarly journals Mapping High Spatiotemporal-Resolution Soil Moisture by Upscaling Sparse Ground-Based Observations Using a Bayesian Linear Regression Method for Comparison with Microwave Remotely Sensed Soil Moisture Products

2021 ◽  
Vol 13 (2) ◽  
pp. 228
Author(s):  
Jian Kang ◽  
Rui Jin ◽  
Xin Li ◽  
Yang Zhang
Keyword(s):  
Soil Moisture ◽  
Large Scale ◽  
Spatial Scales ◽  
Microwave Remote Sensing ◽  
In Situ Measurements ◽  
Spatial Density ◽  
Linear Regression Method ◽  
Spatiotemporal Resolution ◽  
Pixel Scale

In recent decades, microwave remote sensing (RS) has been used to measure soil moisture (SM). Long-term and large-scale RS SM datasets derived from various microwave sensors have been used in environmental fields. Understanding the accuracies of RS SM products is essential for their proper applications. However, due to the mismatched spatial scale between the ground-based and RS observations, the truth at the pixel scale may not be accurately represented by ground-based observations, especially when the spatial density of in situ measurements is low. Because ground-based observations are often sparsely distributed, temporal upscaling was adopted to transform a few in situ measurements into SM values at a pixel scale of 1 km by introducing the temperature vegetation dryness index (TVDI) related to SM. The upscaled SM showed high consistency with in situ SM observations and could accurately capture rainfall events. The upscaled SM was considered as the reference data to evaluate RS SM products at different spatial scales. In regard to the validation results, in addition to the correlation coefficient (R) of the Soil Moisture Active Passive (SMAP) SM being slightly lower than that of the Climate Change Initiative (CCI) SM, SMAP had the best performance in terms of the root-mean-square error (RMSE), unbiased RMSE and bias, followed by the CCI. The Soil Moisture and Ocean Salinity (SMOS) products were in worse agreement with the upscaled SM and were inferior to the R value of the X-band SM of the Advanced Microwave Scanning Radiometer 2 (AMSR2). In conclusion, in the study area, the SMAP and CCI SM are more reliable, although both products were underestimated by 0.060 cm3 cm−3 and 0.077 cm3 cm−3, respectively. If the biases are corrected, then the improved SMAP with an RMSE of 0.043 cm3 cm−3 and the CCI with an RMSE of 0.039 cm3 cm−3 will hopefully reach the application requirement for an accuracy with an RMSE less than 0.040 cm3 cm−3.

scholarly journals Neural network-based estimates of Southern Ocean net community production from in situ O<sub>2</sub> / Ar and satellite observation: a methodological study

2014 ◽  
Vol 11 (12) ◽  
pp. 3279-3297 ◽  
Author(s):  
C.-H. Chang ◽  
N. C. Johnson ◽  
N. Cassar
Keyword(s):  
Neural Network ◽  
Organic Carbon ◽  
Southern Ocean ◽  
Mixed Layer ◽  
Sea Surface ◽  
Carbon Export ◽  
Net Community Production ◽  
Basin Scale ◽  
Community Production

Abstract. Southern Ocean organic carbon export plays an important role in the global carbon cycle, yet its basin-scale climatology and variability are uncertain due to limited coverage of in situ observations. In this study, a neural network approach based on the self-organizing map (SOM) is adopted to construct weekly gridded (1° × 1°) maps of organic carbon export for the Southern Ocean from 1998 to 2009. The SOM is trained with in situ measurements of O2 / Ar-derived net community production (NCP) that are tightly linked to the carbon export in the mixed layer on timescales of one to two weeks and with six potential NCP predictors: photosynthetically available radiation (PAR), particulate organic carbon (POC), chlorophyll (Chl), sea surface temperature (SST), sea surface height (SSH), and mixed layer depth (MLD). This nonparametric approach is based entirely on the observed statistical relationships between NCP and the predictors and, therefore, is strongly constrained by observations. A thorough cross-validation yields three retained NCP predictors, Chl, PAR, and MLD. Our constructed NCP is further validated by good agreement with previously published, independent in situ derived NCP of weekly or longer temporal resolution through real-time and climatological comparisons at various sampling sites. The resulting November–March NCP climatology reveals a pronounced zonal band of high NCP roughly following the Subtropical Front in the Atlantic, Indian, and western Pacific sectors, and turns southeastward shortly after the dateline. Other regions of elevated NCP include the upwelling zones off Chile and Namibia, the Patagonian Shelf, the Antarctic coast, and areas surrounding the Islands of Kerguelen, South Georgia, and Crozet. This basin-scale NCP climatology closely resembles that of the satellite POC field and observed air–sea CO2 flux. The long-term mean area-integrated NCP south of 50° S from our dataset, 17.9 mmol C m−2 d−1, falls within the range of 8.3 to 24 mmol C m−2 d−1 from other model estimates. A broad agreement is found in the basin-wide NCP climatology among various models but with significant spatial variations, particularly in the Patagonian Shelf. Our approach provides a comprehensive view of the Southern Ocean NCP climatology and a potential opportunity to further investigate interannual and intraseasonal variability.

Predator–Prey Relationships for Juvenile Chinook Salmon, Oncorhynchus tshawytscha, Feeding on Zooplankton in "in situ" Enclosures

1983 ◽  
Vol 40 (3) ◽  
pp. 287-297 ◽  
Author(s):  
Karl K. English
Keyword(s):  
Growth Rates ◽  
Chinook Salmon ◽  
Oncorhynchus Tshawytscha ◽  
Fish Growth ◽  
Juvenile Salmon ◽  
Predator Prey ◽  
Juvenile Chinook Salmon ◽  
Successful Search ◽  
Juvenile Chinook

Juvenile chinook salmon, Oncorhynchus tshawytscha, were raised in 90-m3 mesh enclosures in Saanich Inlet, B.C. The enclosures permitted ample water and zooplankton circulation while retaining 5–6 g juvenile salmon. Mean growth rate was 1.8% wet body weight/d over 6 wk. Weekly growth rates ranged from 3.9%/d while food was abundant, to −0.5%/d when food was scarce. Zooplankton concentration inside and outside enclosures without fish were not significantly different. Organisms associated with the sides of the enclosures (non-pelagic) were not a major contributor to the growth of the juvenile chinook. There was a strong relationship between the fish growth rates and the abundance of 1.4- to 4.5-mm zooplankton. Rates of successful search varied directly with the size and inherent contrast of a prey item. The minimum rate of successful search was 2.3 m3/h for salmon feeding on 1.4- to 4.5-mm zooplankton. This rate of successful search, while far greater than previously suspected, is still within the visual capabilities of the juvenile salmon. The enclosed salmon grew rapidly on zooplankton concentrations that were 1/1000 of those required to sustain similar growth rates in tank experiments.Key words: predator–prey relationship, planktivorous salmonid, marine, "in situ" enclosures, search efficiency

Landscape Influences on Stream Habitats and Biological Assemblages

2006 ◽  
Keyword(s):  
Land Cover ◽  
Ictalurus Punctatus ◽  
Environmental Variables ◽  
Agricultural Land ◽  
Fish Assemblages ◽  
Spatial Scales ◽  
Species Abundance ◽  
Ecological Condition ◽  
Basin Scale ◽  
Assemblage Metrics

<em>Abstract.</em>—We analyzed data from 38 sites on 31 large rivers in Wisconsin to characterize the influence of environmental variables at the basin, reach, and site scales on fish assemblages. Electrofishing and site habitat data were collected for a distance of 1.6 km per site. Environmental variables included conductivity, substrate, and fish cover at the site scale; distance to impoundments, dams, and length of riverine habitat at the reach scale; and land cover, climate, and geology at the basin scale. Of the 77 fish species found, 39 occurred in more than 10% of the sites and were retained for analyses of fish abundance and biomass. Redundancy analysis (RDA) was used to relate species abundance, biomass, and 16 assemblage metrics to environmental variables at the three spatial scales. The site and basin scales defined fishes along a gradient from high conductivity, fine substrate, and agricultural land cover to low conductivity, rocky substrate, and forested land cover. For abundance and biomass, the strongest assemblage pattern contrasted northern hog sucker <em>Hypentelium nigricans</em>, blackside darter <em>Percina maculata</em>, and logperch <em>P. caprodes </em>with common carp <em>Cyprinus carpio</em>, channel catfish <em>Ictalurus punctatus</em>, and sauger <em>Sander canadensis</em>. The <em>H. nigricans </em>group, along with high values of index of biotic integrity and some assemblage metrics (percent lithophilic spawners, percent round-bodied suckers), corresponded with the forested end of the ecological gradient, whereas the <em>C. carpio </em>group and percent anomalies corresponded with the agricultural end. Natural environmental conditions, including bedrock geology type, bedrock depth, surficial geology texture, basin area, and precipitation, also influenced the fish assemblage. Partial RDA procedures partitioned the explained variation among spatial scales and their interactions. We found that widespread land cover alterations at the basin scale were most strongly related to fish assemblages across our study area. Understanding the influence of environmental variables among multiple spatial scales on fish assemblages can improve our ability to assess the ecological condition of large river systems and subsequently target the appropriate scale for management or restoration efforts.

scholarly journals RAD-Seq Analysis and in situ Monitoring of Nassau Grouper Reveal Fine-Scale Population Structure and Origins of Aggregating Fish

2020 ◽  
Vol 7 ◽  
Author(s):  
Krista D. Sherman ◽  
Josephine R. Paris ◽  
Robert Andrew King ◽  
Karen A. Moore ◽  
Craig P. Dahlgren ◽  
...  
Keyword(s):  
Population Structure ◽  
In Situ Monitoring ◽  
Fine Scale ◽  
Nassau Grouper ◽  
Scale Population

scholarly journals The Mediterranean Ocean Colour Level 3 Operational Multi-Sensor Processing

2018 ◽  
Author(s):  
Gianluca Volpe ◽  
Simone Colella ◽  
Vittorio Brando ◽  
Vega Forneris ◽  
Flavio La Padula ◽  
...  
Keyword(s):  
Fine Tuning ◽  
Ocean Colour ◽  
Basin Scale ◽  
Sensor Processing ◽  
Level 3 ◽  
The Mediterranean ◽  
Set Up ◽  
Marine Environment Monitoring ◽  
Monitoring Service

Abstract. This work describes the main processing steps operationally performed to enable single ocean colour sensors to enter the multi-sensor chain for the Mediterranean Sea of Ocean Colour Thematic Assembling Centre. Here, the multi-sensor chain takes care of reducing the inter-sensor bias before data from different sensors are merged together. The basin-scale in situ bio-optical dataset is used both to fine-tuning the algorithms for the retrieval of phytoplankton chlorophyll and attenuation coefficient of light, Kd, and to assess the uncertainty associated with them. The satellite multi-sensor remote sensing Reflectance spectra better agree with the in situ observations than that of the single sensors, and are comparable with the ESA-OC-CCI multi-sensor product, highlighting the importance of reducing the inter-sensor bias. The Mediterranean near-real-time multi-sensor processing chain has been set up and is operational in the framework of the Copernicus Marine Environment Monitoring Service.

scholarly journals Dust Measurements in the Outer Solar System

1994 ◽  
Vol 160 ◽  
pp. 367-380
Author(s):  
Eberhard Grün
Keyword(s):  
Solar System ◽  
Interstellar Dust ◽  
Thermal Emission ◽  
Scattered Light ◽  
Interplanetary Dust ◽  
Dust Particles ◽  
Spatial Density ◽  
Outer Solar System ◽  
The Sun

In-situ measurements of micrometeoroids provide information on the spatial distribution of interplanetary dust and its dynamical properties. Pioneers 10 and 11, Galileo and Ulysses spaceprobes took measurements of interplanetary dust from 0.7 to 18 AU distance from the sun. Distinctly different populations of dust particles exist in the inner and outer solar system. In the inner solar system, out to about 3 AU, zodiacal dust particles are recognized by their scattered light, their thermal emission and by in-situ detection from spaceprobes. These particles orbit the sun on low inclination (i ≤ 30°) and moderate eccentricity (e ≤ 0.6) orbits. Their spatial density falls off with approximately the inverse of the solar distance. Dust particles on high inclination or even retrograde trajectories dominate the dust population outside about 3 AU. The dust detector on board the Ulysses spaceprobe identified interstellar dust sweeping through the outer solar system on hyperbolic trajectories. Within about 2 AU from Jupiter Ulysses discovered periodic streams of dust particles originating from within the jovian system.

scholarly journals On the Variability of the Circulation and Water Mass Properties in the Eastern Levantine Sea between September 2016–August 2017

Water ◽  
2019 ◽  
Vol 11 (9) ◽  
pp. 1741 ◽  
Author(s):  
Mauri ◽  
Sitz ◽  
Gerin ◽  
Poulain ◽  
Hayes ◽  
...  
Keyword(s):  
High Salinity ◽  
Autonomous Systems ◽  
Vertical Mixing ◽  
The North ◽  
Levantine Sea ◽  
Surface Circulation ◽  
Basin Scale ◽  
Geographical Position ◽  
Surface Drifters

The surface circulation and the thermohaline properties of the water masses of the eastern Levantine Sea (Mediterranean Sea) were monitored with mobile autonomous systems (surface drifters and gliders) during the period September 2016–August 2017. The drifters provided data for more than a year and revealed complex circulation features at scales ranging from the basin scale to the sub-mesoscale. Three drifters were captured in a semi-permanent gyre (Cyprus Eddy) allowing a quantitative study of its kinematics. During the experiment, three gliders were operated, in two different periods: September to December 2016 and February to March 2017. The autonomous instruments crossed the prevailing sub-basin structures several times. The collected in-situ observations were analyzed and interpreted in concert with remote sensing products (sea surface temperature and altimetry). The evolution of some of the prevailing features confirmed the complexity of the circulation of the basin. The Cyprus Eddy is the most persistent anticyclone, moving its geographical position and sometimes merging with the North Shikmona Eddy in a bigger structure. The gliders sampled this wide anticyclonic feature revealing its vertical structure in the two different periods. In fall, in stratified conditions, a high salinity core is evident below the thermocline. The isopycnals are characterized by an upward bending over the high salinity lens and a downward bending below it, typical of an anticyclonic modewater eddy. In winter, the core disappears following the vertical mixing that, homogenizes the upper Cyprus Eddy water down to 300 m.

Comparison and utility of different size-based metrics of fish communities for detecting fishery impacts

2006 ◽  
Vol 63 (4) ◽  
pp. 810-820 ◽  
Author(s):  
Daniel E Duplisea ◽  
Martin Castonguay
Keyword(s):  
Standing Stock ◽  
Fish Communities ◽  
Ecosystem Approach ◽  
Size Spectrum ◽  
Size Spectra ◽  
Predator Prey ◽  
Similar Information ◽  
Chance Events ◽  
Length Frequency Analysis ◽  
Scientific Survey

The use of fish community indicators based on size spectra has become popular in the development of an ecosystem approach to fisheries. Size spectrum theory arose from basic ecological work on energy flow, predator–prey interactions, and biomass standing stock and was later applied to fish communities as length–frequency analysis. A multitude of size spectrum indicators have resulted, but it is not clear if they all present similar information. Here we develop a simple framework describing what four size spectra indicators suggest about fish communities, their likely response to fisheries exploitation, their ecological interpretation, and some of their biases. We examined indicators for scientific survey data from six exploited North Atlantic fish communities for the information that they reveal about each community. Each indicator revealed different information and had different biases. Combining indicators for the most impacted system (owing to fisheries and environmental change), the eastern Scotian Shelf, revealed a pattern analogous to Holling's ecological cycle of exploitation, conservation, release, and reorganisation. If this analogy is generally valid, then it suggests that collapsed fish communities are more susceptible to chance events, and recovery is not directly reversible and may not be recoverable (to previous known state) at all if the system moves to an alternative cycle.

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