scholarly journals Waves and currents decrease the available space in a salmon cage

2021 ◽  
Author(s):  
Asa Johannesen ◽  
Øystein Patursson ◽  
Jóhannus Kristmundsson ◽  
Signar Pæturssonur Dam ◽  
Mats Mulelid ◽  
...  
Keyword(s):  
Water Column ◽  
Water Exchange ◽  
High Biomass ◽  
Environmental Barriers ◽  
Video Cameras ◽  
Available Water ◽  
Entire Water Column ◽  
Waves And Currents ◽  
Exposed Part ◽  
Increasing Demand

Due to increasing demand for salmon and environmental barriers preventing expansion in established sites, salmon farmers seek to move or expand their production to more exposed sites. In this study we investigate the effects of strong currents and waves on the behaviour of salmon and how they choose to use the space available to them. Using video cameras and echo sounders, we show that fish prefer to use the entire water column, narrowing their range only as a response to cage deformation, waves, or daylight. Conversely, fish show strong horizontal preference, mostly occupying the portions of the cage exposed to currents. Additionally, waves cause salmon to move away from the sides of the cage. Even when strong currents and waves decrease the amount of available space, salmon choose to occupy the more exposed part of the cage. This indicates that at least with good water exchange, the high biomass caused by limited vertical space is not so aversive that salmon choose to move to less desirable areas of the cage. However, the dispersal throughout the entire available water column indicates that keeping the cone portion of the cage available in strong currents would be beneficial to salmon welfare.

Use competition and water exchange in Marina Baja district, Alicante, Spain

2005 ◽  
Vol 5 (3-4) ◽  
pp. 265-272 ◽  
Author(s):  
T.T. Martí
Keyword(s):  
Water Exchange ◽  
Citrus Fruit ◽  
Water Markets ◽  
Tourist Industry ◽  
Related Services ◽  
Integrated Water Management ◽  
The North ◽  
Increasing Demand ◽  
Water Problems ◽  
Water Uses

The water problems in Marina Baja district, located in the north of Alicante Province, southeast Spain, gives rise to very interesting practices in the management of this scarce resource. The key issue in water use both in the Júcar Catchment and in Marina Baja district is the growing demand for water in inland areas for intensive crop irrigation (principally fruit, medlars and citrus fruit) and the growth in demand for water for urban use, as well as for use in the tourist industry and its related services mainly in the towns in the coastal areas, due to strong growth in tourism. This trend of increasing demand has created a tense situation as well as conflict between existing water uses and the need for integrated water management in the area. This step implies that procedures for water exchange contracts have to be developed, that are significantly different from emerging water markets.

Variability of the Horizontal Velocity Structure in the Upper 1600 m of the Water Column on the Equator at 10°W

2006 ◽  
Vol 36 (7) ◽  
pp. 1287-1304 ◽  
Author(s):  
Lucia Bunge ◽  
Christine Provost ◽  
Jonathan M. Lilly ◽  
Marc D’Orgeville ◽  
Annie Kartavtseff ◽  
...  
Keyword(s):  
Water Column ◽  
Velocity Component ◽  
Velocity Structure ◽  
Strong Dependence ◽  
Acoustic Doppler Current Profiler ◽  
Horizontal Velocity ◽  
Vertical Shear ◽  
Equatorial Atlantic ◽  
Entire Water Column ◽  
Current Profiler

Abstract This paper presents initial results from new velocity observations in the eastern part of the equatorial Atlantic Ocean from a moored current-meter array. During the “EQUALANT” program (1999–2000), a mooring array was deployed around the equator near 10°W that recorded one year of measurements at various depths. Horizontal velocities were obtained in the upper 60 m from an upward-looking acoustic Doppler current profiler (ADCP) and at 13 deeper levels from current meters between 745 and 1525 m. To analyze the quasiperiodic variability observed in these records, a wavelet-based technique was used. Quasiperiodic oscillations having periods between 5 and 100 days were separated into four bands: 5–10, 10–20, 20–40, and 40–100 days. The variability shows (i) a strong seasonality (the first half of the series is dominated by larger periods than the second one) and (ii) a strong dependence with depth (some oscillations are present in the entire water column while others are only present at certain depths). For the oscillations that are present in the entire water column the origin of the forcing can be traced to the surface, while for the others the question of their origin remains open. Phase shifts at different depths generate vertical shears in the horizontal velocity component with relatively short vertical scales. This is especially visible in long-duration events (>100 days) of the zonal velocity component. Comparison with a simultaneous lowered acoustic Doppler current profiler (LADCP) section suggests that some of these flows may be identified with equatorial deep jets. A striking feature is a strong vertical shear lasting about 7 months between 745 and 1000 m. These deep current-meter observations would then imply a few months of duration for the jets in this region.

scholarly journals A model for the evolution of the thermal bar system

2012 ◽  
Vol 24 (2) ◽  
pp. 161-177 ◽  
Author(s):  
DUNCAN E. FARROW
Keyword(s):  
Surface Layer ◽  
Water Column ◽  
Thermal Balance ◽  
Spring Warming ◽  
Entire Water Column ◽  
Horizontal Extent ◽  
Thermal Bar ◽  
Stable Surface Layer ◽  
Near Shore ◽  
New Framework

A new framework for modelling the evolution of the thermal bar system in a lake is presented. The model assumes that the thermal bar is located between two regions: the deeper region, where spring warming leads to overturning of the entire water column, and the near shore shallower region, where a stable surface layer is established. In this model the thermal bar moves out slightly more quickly than predicted by a simple thermal balance. Also, the horizontal extent of the thermal bar region increases as it moves out from the shore.

A New Thermal Categorization of Ice-covered Lakes

2021 ◽  
Author(s):  
Bernard Yang ◽  
Mathew Wells ◽  
Bailey McMeans ◽  
Hilary Dugan ◽  
James Rusak ◽  
...  
Keyword(s):  
Temperature Profile ◽  
Water Column ◽  
Wind Stress ◽  
Thermal Regime ◽  
Thermal Stratification ◽  
Trophic Status ◽  
Cold Water ◽  
Entire Water Column ◽  
Lake Type

<p>Lakes are traditionally classified based on their thermal regime and trophic status. While this classification adequately captures many lakes, it is not sufficient to understand seasonally ice-covered lakes, the most common lake type on Earth. We describe the inverse thermal stratification in 19 highly varying lakes and derive a model that predicts the temperature profile as a function of wind stress, area, and depth. The results suggest an additional subdivision of seasonally ice-covered lakes to differentiate under-ice stratification. When ice forms in smaller and deeper lakes, inverse stratification will form with a thin buoyant layer of cold water (near 0<sup>o</sup>C) below the ice, which remains above a deeper 4<sup>o</sup>C layer. In contrast, the entire water column can cool to ~0<sup>o</sup>C in larger and shallower lakes. We suggest these alternative conditions for dimictic lakes be termed “cryostratified” and “cryomictic.”</p>

Observations of Turbulent Mixing During a Nonstratification Period in the Yellow Sea

2021 ◽  
Vol 55 (2) ◽  
pp. 185-197
Author(s):  
Yunli Nie ◽  
Xin Luan ◽  
Hua Yang ◽  
Xu Chen ◽  
Dalei Song ◽  
...  
Keyword(s):  
Water Column ◽  
Turbulent Mixing ◽  
Yellow Sea ◽  
Dissipation Rate ◽  
Distribution Functions ◽  
Cumulative Distribution ◽  
The Yellow Sea ◽  
Distribution Model ◽  
Entire Water Column ◽  
Diapycnal Diffusivity

Abstract Microstructure profiling measurements collected at the continental shelf of the Yellow Sea (35°38'N, 121°20'E) from December 4 to 5, 2019, were analyzed by focusing on the characteristics of turbulent mixing in the Yellow Sea and its associated influencing factors. The vertical thermohaline structure of the water column was nonstratified during the observation period, resulting in the vertically and temporally consistent distribution of turbulence dissipation and diapycnal diffusivity. The average (in time and space) dissipation rate and diapycnal diffusivity were 2.95 × 10−8 W kg−1 and 1.86 × 10−4 m2 s−1, respectively. In the vertical distribution, intense mixing occurred near the sea surface and within the bottom layers. The temporal variation in dissipation exhibits a diurnal variation that was strongly affected by surface buoyancy flux and wind energy, and a high amount of dissipation was observed at night, with an average dissipation rate of 2.45 × 10−8 W kg−1, which was almost one order of magnitude higher than that in the daytime (3.55 × 10−9 W kg−1). The cumulative distribution functions of the dissipation rate and diapycnal diffusivity across the entire water column during the measurement period could be parameterized by a lognormal distribution model. Further analysis shows that the dissipation rate was positively related to wind speed and rotational barotropic tidal velocity. Compared with the rotating tidal current, wind-driven turbulence was able to penetrate the surface, thereby causing layer mixing throughout the entire water column (R = 0.71), and is a dominant driver of elevated turbulent mixing during wintertime.

scholarly journals The Effect of Cold and Warm Anomalies on Phytoplankton Pigment Composition in Waters off the Northern Baja California Peninsula (México): 2007–2016

2020 ◽  
Vol 8 (7) ◽  
pp. 533 ◽  
Author(s):  
Adriana González-Silvera ◽  
Eduardo Santamaría-del-Ángel ◽  
Víctor Camacho-Ibar ◽  
Jorge López-Calderón ◽  
Jonatan Santander-Cruz ◽  
...  
Keyword(s):  
Water Column ◽  
Chlorophyll A ◽  
Community Composition ◽  
High Performance ◽  
Baja California ◽  
Regional Scale ◽  
Baja California Peninsula ◽  
Phytoplankton Pigments ◽  
Entire Water Column ◽  
Satellite Chlorophyll

In this study, we report the response of phytoplankton community composition to cold and warm interannual events affecting the waters off the Baja California Peninsula from 2007 to 2016 based on data obtained from a single marine station (31.75° N/116.96° W). Included variables were satellite chlorophyll a, sea surface temperature (MODIS/Aqua), upwelling intensity, and field data (phytoplankton pigments, inorganic nutrients, light penetration). Phytoplankton pigments were determined by high performance liquid chromatography, and CHEMTAX software was used to determine the relative contributions of the main taxonomic groups to chlorophyll a. Our results confirm the decrease in phytoplankton biomass due to the influence of the recent Pacific Warm Anomaly (2014) and El Niño 2015–2016. However, this decrease was especially marked at the surface. When data from the entire water column was considered, this decrease was not significant, because at the subsurface Chla did not decrease as much. Nevertheless, significant changes in community composition occurred in the entire water column with Cyanobacteria (including Prochlorococcus) and Prymnesiophytes being dominant at the surface, while Chlorophytes and Prasinophytes made a strong contribution at the subsurface. Analysis of the spatial distribution of SST and satellite chlorophyll a made it possible to infer the spatial extension of these anomalies at a regional scale.

scholarly journals Cold-water corals in the Subpolar North Atlantic Ocean exposed to aragonite undersaturation if Paris 2 ºC is not met

2021 ◽  
Author(s):  
Maribel I. García-Ibáñez ◽  
Nicholas R. Bates ◽  
Dorothee C.E. Bakker ◽  
Marcos Fontela ◽  
Antón Velo
Keyword(s):  
Atlantic Ocean ◽  
Water Column ◽  
North Atlantic ◽  
Cold Water ◽  
Sea Water ◽  
North Atlantic Ocean ◽  
Labrador Sea ◽  
Entire Water Column ◽  
Intermediate Waters ◽  
Labrador Sea Water

<p>The uptake of carbon dioxide (CO<sub>2</sub>) from the atmosphere is changing the ocean’s chemical state. Such changes, commonly known as ocean acidification, include reduction in pH and the carbonate ion concentration ([CO<sub>3</sub><sup>2-</sup>]), which in turn lowers oceanic saturation states (Ω) for calcium carbonate (CaCO<sub>3</sub>) minerals. The Ω values for aragonite (Ω<sub>aragonite</sub>; one of the main CaCO<sub>3</sub> minerals formed by marine calcifying organisms) influence the calcification rate and geographic distribution of cold-water corals (CWCs), important for biodiversity. In this work we use high-quality data of inorganic carbon measurements, collected on thirteen cruises along the same track during 1991–2018, to determine the long-term trends in Ω<sub>aragonite</sub> in the Irminger and Iceland Basins of the North Atlantic Ocean, providing the first trends of Ω<sub>aragonite</sub> in the deep waters of these basins. The entire water column of both basins showed significant negative Ω<sub>aragonite</sub> trends between -0.0015 ± 0.0002 and -0.0061 ± 0.0016 per year. The decrease in Ω<sub>aragonite</sub> in the intermediate waters, where nearly half of the CWC reefs of the study region are located, caused the Ω<sub>aragonite</sub> isolines to migrate upwards rapidly at a rate between 6 and 34 m per year. The main driver of the observed decline in Ω<sub>aragonite</sub> in the Irminger and Iceland Basins was the increase in anthropogenic CO<sub>2</sub>. But this was partially offset by increases in salinity (in Subpolar Mode Water), enhanced ventilation (in upper Labrador Sea Water) and increases in alkalinity (in classical Labrador Sea Water, cLSW; and overflow waters). We also found that water mass aging reinforced the Ω<sub>aragonite</sub> decrease in cLSW. Based on the observed Ω<sub>aragonite</sub> trends, we project that the entire water column of the Irminger and Iceland Basins will likely be undersaturated for aragonite when in equilibrium with an atmospheric mole fraction of CO<sub>2</sub> (xCO<sub>2</sub>) of ~860 ppmv, corresponding to climate model projections for the end of the century based on the highest CO<sub>2</sub> emission scenarios. However, intermediate waters will likely be aragonite undersaturated when in equilibrium with an atmospheric xCO<sub>2</sub> of ~600 ppmv, an xCO<sub>2</sub> level slightly above that corresponding to 2 ºC warming, thus exposing CWCs inhabiting the intermediate waters to undersaturation for aragonite.</p>

The state of understanding of the effects of beach nourishment activities on coastal biogeochemical processes and conditions

Shore & Beach ◽  
2019 ◽  
pp. 46-57 ◽  
Author(s):  
Angelos Hannides ◽  
Nicole Elko ◽  
Kenneth Humiston
Keyword(s):  
Water Column ◽  
Chemical Reactions ◽  
Oxygen Demand ◽  
Sandy Beaches ◽  
Biogeochemical Processes ◽  
Policy Makers ◽  
Rapid Exchange ◽  
Waves And Currents ◽  
Oxygenated Water ◽  
The One

Sandy beaches are sites of significant exchange of matter and energy between water and sediment. This rapid exchange is attributed to the high permeability of sandy deposits and is one of the key ingredients in understanding how a given beach will respond to a nourishment event as a habitat for many important organisms. The response is driven by fundamental abiotically and biotically mediated chemical reactions that are profoundly affected by the ability of chemicals to accumulate or to be flushed out of a sandy column in the beach substrate. So while attention has correctly been paid to the effects of nourishment projects on infaunal communities and the upper levels of the food web, the chemical reactions connecting physics and geology on the one hand and ecology on the other are treated as a black box. We synthesize existing findings on biogeochemical processes at source areas and renourished beaches before, during, and after nourishment activities, and identify gaps in knowledge. Among other processes, we highlight how the exposure of reduced sediment to an oxic water column can initially increase oxygen demand, fuel microbial primary productivity, and drive the mobilization of potentially harmful contaminants. Restoration of oxic conditions in surficial sands can proceed rapidly through rapid exchange between sand and the oxygenated water column under the influence of physical forces, such as waves and currents, and high sand permeability. Based on our findings, we recommend foci for research, outreach, and broader impacts in this field as well as discuss coastal management needs for policy makers, planners, contractors, and the public to encourage information sharing.

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