Shelf Transport Pathways Adjacent to the East Australian Current Reveal Sources of Productivity for Coastal Reefs

The region where the East Australian Current (EAC) separates from the coast is dynamic and the shelf circulation is impacted by the interplay of the western boundary current and its eddy field with the coastal ocean. This interaction can drive upwelling, retention or export. Hence understanding the connection between offshore waters and the inner shelf is needed as it influences the productivity potential of valuable coastal rocky reefs. Near urban centres, artificial reefs enhance fishing opportunities in coastal waters, however these reefs are located without consideration of the productivity potential of adjacent waters. Here we identify three dominant modes of mesoscale circulation in the EAC separation region (~31.5−34.5°S); the ‘EAC mode’ which dominates the flow in the poleward direction, and two eddy modes, the ‘EAC eddy mode’ and the ‘Eddy dipole mode’, which are determined by the configuration of a cyclonic and anticyclonic eddy and the relationship with the separated EAC jet. We use a Lagrangian approach to reveal the transport pathways across the shelf to understand the impact of the mesoscale circulation modes and to explore the productivity potential of the coastal waters. We investigate the origin (position and depth) of the water that arrives at the inner-mid shelf over a 21-day period (the plankton productivity timescale). We show that the proportion of water that is upwelled from below the euphotic zone varies spatially, and with each mesoscale circulation mode. Additionally, shelf transport timescales and pathways are also impacted by the mesoscale circulation. The highest proportion of upwelling (70%) occurs upstream of 32.5°S, associated with the EAC jet separation, with vertical displacements of 70–120 m. From 33 to 33.5°S, water comes from offshore above the euphotic layer, and shelf transport timescales are longest. The region of highest retention over the inner shelf is immediately downstream of the EAC separation region. The position of the EAC jet and the location of the cyclonic eddy determines the variability in shelf-ocean interactions and the productivity of shelf waters. These results are useful for understanding productivity of temperate rocky reefs in general and specifically for fisheries enhancements along an increasingly urbanised coast.

Download Full-text

Eddy Formation and Shedding in a Separating Boundary Current

Journal of Physical Oceanography ◽

10.1175/2009jpo4151.1 ◽

2009 ◽

Vol 39 (8) ◽

pp. 1921-1934 ◽

Cited By ~ 6

Author(s):

Thierry Pichevin ◽

Steven Herbette ◽

France Floc’h

Keyword(s):

Western Boundary ◽

Coastal Current ◽

Separation Region ◽

Boundary Current ◽

Western Boundary Currents ◽

Boundary Currents ◽

Eddy Formation ◽

Induced Velocity ◽

The Impact ◽

Westward Drift

Abstract This study deals with the separation of western boundary currents within a reduced-gravity framework, and it analyzes the formation of eddies in the separation region and the conditions of their shedding into the open ocean. It shows that the separation point of the current oscillates along the coast so that the retroflected eastward current develops meanders. These meanders grow, drift westward under the influence of β, and finally hit the coastal current, which leads to the periodic formation of eddies. This study also highlights the impact by the geometrical configurations of the flow and coastline upon the existence or lack of a subsequent shedding of these eddies: a shedding occurs when no obstacle hinders the β-induced westward drift of the eddies. This happens when either (i) the current retroflects far enough beyond the tip of the coast so that, because of β, the eddies can propagate westward without being blocked, or (ii) the tilt of the coast is small enough so that the alongshore component of the β-induced velocity is enhanced and the eddies can escape from the retroflection region.

Download Full-text

Marine Quality Standards: Their Derivation and Application in the United Kingdom

Water Science & Technology ◽

10.2166/wst.1985.0213 ◽

1985 ◽

Vol 17 (6-7) ◽

pp. 1187-1198 ◽

Cited By ~ 1

Author(s):

G. Mance ◽

A. R. O'Donnell

Keyword(s):

Coastal Waters ◽

Sublethal Effects ◽

Quality Standards ◽

Toxicity Data ◽

Marine Life ◽

Nickel Zinc ◽

The United Kingdom ◽

The Common ◽

Lead Nickel ◽

The Impact

This paper discusses the derivation of environmental quality standards for coastal waters and the difficulties of using such standards for controlling industrial discharges. Attention is focused on the common List II substances, copper, chromium, lead, nickel, zinc and arsenic - and their effects on marine life. The adequacy of existing toxicity data is discussed and it is concluded that long exposure tests are required to provide information on sublethal effects. Such data are currently limited. It is also important that consideration be given to the effects that reducing salinities and increasing temperatures have in increasing the toxicity of these substances. The complexity of interpreting the results of laboratory toxicity data to coastal waters is discussed with reference to a study of the impact of an industrial discharge.

Download Full-text

Assessing an Atmospheric Correction Algorithm for Time Series of Satellite-Based Water-Leaving Reflectance Using Match-Up Sites in Australian Coastal Waters

Remote Sensing ◽

10.3390/rs13101927 ◽

2021 ◽

Vol 13 (10) ◽

pp. 1927

Author(s):

Fuqin Li ◽

David Jupp ◽

Thomas Schroeder ◽

Stephen Sagar ◽

Joshua Sixsmith ◽

...

Keyword(s):

Coastal Waters ◽

Atmospheric Correction ◽

Correction Method ◽

In Situ Measurements ◽

Landsat 8 ◽

Correction Algorithm ◽

Simple Method ◽

North East ◽

The Impact

An atmospheric correction algorithm for medium-resolution satellite data over general water surfaces (open/coastal, estuarine and inland waters) has been assessed in Australian coastal waters. In situ measurements at four match-up sites were used with 21 Landsat 8 images acquired between 2014 and 2017. Three aerosol sources (AERONET, MODIS ocean aerosol and climatology) were used to test the impact of the selection of aerosol optical depth (AOD) and Ångström coefficient on the retrieved accuracy. The initial results showed that the satellite-derived water-leaving reflectance can have good agreement with the in situ measurements, provided that the sun glint is handled effectively. Although the AERONET aerosol data performed best, the contemporary satellite-derived aerosol information from MODIS or an aerosol climatology could also be as effective, and should be assessed with further in situ measurements. Two sun glint correction strategies were assessed for their ability to remove the glint bias. The most successful one used the average of two shortwave infrared (SWIR) bands to represent sun glint and subtracted it from each band. Using this sun glint correction method, the mean all-band error of the retrieved water-leaving reflectance at the Lucinda Jetty Coastal Observatory (LJCO) in north east Australia was close to 4% and unbiased over 14 acquisitions. A persistent bias in the other strategy was likely due to the sky radiance being non-uniform for the selected images. In regard to future options for an operational sun glint correction, the simple method may be sufficient for clear skies until a physically based method has been established.

Download Full-text

Averaging-Related Biases in Monthly Latent Heat Fluxes

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech-d-11-00184.1 ◽

2012 ◽

Vol 29 (7) ◽

pp. 974-986 ◽

Cited By ~ 10

Author(s):

Paul J. Hughes ◽

Mark A. Bourassa ◽

Jeremy J. Rolph ◽

Shawn R. Smith

Keyword(s):

Latent Heat ◽

Classical Method ◽

Surface Flux ◽

Heat Fluxes ◽

Western Boundary ◽

State University ◽

Boundary Current ◽

Surface Energy Fluxes ◽

Temporal Averaging ◽

The Impact

Abstract Seasonal-to-multidecadal applications that require ocean surface energy fluxes often require accuracies of surface turbulent fluxes to be 5 W m−2 or better. While there is little doubt that uncertainties in the flux algorithms and input data can cause considerable errors, the impact of temporal averaging has been more controversial. The biases resulting from using monthly averaged winds, temperatures, and humidities in the bulk aerodynamic formula (i.e., the so-called classical method) to estimate the monthly mean latent heat fluxes are shown to be substantial and spatially varying in a manner that is consistent with most prior work. These averaging-related biases are linked to nonnegligible submonthly covariances between the wind, temperature, and humidity. To provide additional insight into the averaging-related bias, the methodology behind the third-generation Florida State University monthly mean surface flux product (FSU3) is detailed to highlight additional sources of errors in gridded datasets. The FSU3 latent heat fluxes suffer from this averaging-related bias, which can be as large as 90 W m−2 in western boundary current regions during winter and can exceed 40 W m−2 in synoptically active portions of the tropics. The regional impacts of these biases on the mixed layer temperature tendency are shown to demonstrate that the error resulting from applying the classical method is physically substantial.

Download Full-text

Hydrophobicity drives the systemic distribution of lipid-conjugated siRNAs via lipid transport pathways

10.1101/288092 ◽

2018 ◽

Author(s):

Maire F. Osborn ◽

Andrew H. Coles ◽

Annabelle Biscans ◽

Reka A. Haraszti ◽

Loic Roux ◽

...

Keyword(s):

Sirna Delivery ◽

Lipid Transport ◽

Small Interfering Rnas ◽

Transport Pathways ◽

Efficient Delivery ◽

Systemic Distribution ◽

Lipoprotein Binding ◽

The Impact ◽

Plasma Half Life

AbstractEfficient delivery of therapeutic RNA is the fundamental obstacle preventing its clinical utility. Lipid conjugation improves plasma half-life, tissue accumulation, and cellular uptake of small interfering RNAs (siRNAs). However, the impact of conjugate structure and hydrophobicity on siRNA pharmacokinetics is unclear, impeding the design of clinically relevant lipid-siRNAs. Using a panel of biologically-occurring lipids, we show that lipid conjugation modulates siRNA hydrophobicity and governs spontaneous partitioning into distinct plasma lipoprotein classes in vivo. Lipoprotein binding influences siRNA distribution by delaying renal excretion and promoting uptake into lipoprotein receptor-enriched tissues. Lipid-siRNAs elicit mRNA silencing without causing toxicity in a tissue-specific manner. Lipid-siRNA internalization occurs independently of lipoprotein endocytosis, and is mediated by siRNA phosphorothioate modifications. Although biomimetic lipoprotein nanoparticles have been considered for the enhancement of siRNA delivery, our findings suggest that hydrophobic modifications can be leveraged to incorporate therapeutic siRNA into endogenous lipid transport pathways without the requirement for synthetic formulation.

Download Full-text

Simulating the Impact of the Internal Structure of Phytoplankton on the Bulk Particulate Backscattering Ratio using a Two-Layered Spherical Geometry for Cells

10.20944/preprints201808.0051.v1 ◽

2018 ◽

Author(s):

Lucile Duforêt-Gaurier ◽

David Dessailly ◽

William Moutier ◽

Hubert Loisel

Keyword(s):

Coastal Waters ◽

Natural Waters ◽

Heterotrophic Bacteria ◽

Relative Concentration ◽

Spherical Geometry ◽

The Third ◽

Study Case ◽

Coated Spheres ◽

The Impact ◽

Phytoplankton Cells

The bulk backscattering ratio ($\tilde{b_{bp}}$) is commonly used as a descriptor of the bulk real refractive index of the particulate assemblage in natural waters. Based on numerical simulations, we analyze the impact of heterogeneity of phytoplankton cells on $\tilde{b_{bp}}$. $\tilde{b_{bp}}$ is modeled considering viruses, heterotrophic bacteria, phytoplankton, detritus, and minerals. Three study cases are defined according to the relative abundance of these different components. Two study cases represent typical situations in open ocean, outside (No-B/No-M) and inside bloom (B/No-M). The third study case is typical of coastal waters with the presence of minerals. Phytoplankton cells are modeled by a two-layered spherical geometry representing a chloroplast surrounding the cytoplasm. The $\tilde{b_{bp}}$ values are higher when heterogeneity is considered because the contribution of coated spheres to backscattering is higher than homogeneous spheres. The impact of heterogeneity is however strongly conditioned by the hyperbolic slope $\xi$ of the particle size distribution. Even if the relative concentration of phytoplankton is small (<1%), $\tilde{b_{bp}}$ increases by about 60% (for $\xi=4.3$ and for the No-B/No-M water body), when the heterogeneity is taken into account, in comparison with a particulate population only composed by homogeneous spheres. As expected, heterogeneity has a much smaller impact (about 5$\%$ for $\xi=4.3$) on $\tilde{b_{bp}}$ when minerals are added.

Download Full-text

Impact of Argo Observation on the Regional Ocean Reanalysis of China Coastal Waters and Adjacent Seas: A Twin-Experiment Study

Advances in Meteorology ◽

10.1155/2015/793825 ◽

2015 ◽

Vol 2015 ◽

pp. 1-15 ◽

Cited By ~ 1

Author(s):

Caixia Shao ◽

Lili Xuan ◽

Yingzhi Cao ◽

Xiaojian Cui ◽

Siyu Gao

Keyword(s):

Coastal Waters ◽

Unique Feature ◽

Information Service ◽

Deep Ocean ◽

Ocean Reanalysis ◽

Rms Error ◽

Regional Reanalysis ◽

Argo Profiles ◽

The Impact

A regional ocean reanalysis system of China coastal waters and adjacent seas, called CORA (China ocean reanalysis), has been recently developed at the National Marine Data and Information Service (NMDIS). In this study, based on CORA, the impact of Argo profiles on the regional reanalysis is evaluated using a twin-experiment approach. It is found that, by assimilating Argo observations, the reanalysis quality is much improved: the root mean square (RMS) error of temperature and salinity can be further reduced by about 10% and the RMS error of current can be further reduced by 18%, compared to the case only assimilating conventional in situ temperature and salinity observations. Consistent with the unique feature of Argo observations, the temperature is improved in all levels and the largest improvement of salinity happens in the deep ocean. Argo profile data have a significant impact on the regional ocean reanalysis through improvements of both hydrographic and dynamic fields.

Download Full-text