The effect of packaging of chlorophyll within phytoplankton and light scattering in a coupled physical-biological ocean model

A coupled physical-biological model forced with spectrally resolved solar radiation is used to investigate the effect of packaging of pigment and light scattering on physical and biological properties in the open ocean. Simulations are undertaken with three alternate formulations of vertical attenuation, which consider: (1) chlorophyll as dissolved in the water column; (2) chlorophyll packaged into phytoplankton cells with no scattering; and (3) packaged chlorophyll with scattering. In the coupled model, depth-resolved solar heating depends on the vertical profile of phytoplankton concentration, creating a feedback mechanism between the physical and biological states. The particular scenario investigated is a northerly wind off the coast of south-east Australia. The packaging of chlorophyll approximately halves the attenuation rate of 340-500 nm light and a phytoplankton maximum forms ∼10 m deeper than in the dissolved chlorophyll case, with a corresponding adjustment of the dissolved inorganic nitrogen and zooplankton fields. Scattering approximately doubles the vertical attenuation of 340-600 nm light, lifting the phytoplankton maximum by ∼10 m when compared with the packaged chlorophyll case. Additionally, strong horizontal gradients in chlorophyll distribution associated with filaments of upwelled water inshore of the East Australian Current, when modelled with alternate formulations of vertical light attenuation, result in circulation changes. The explicit representation of the packaging of pigment and light scattering is worth considering in coupled physical-biological modelling studies. © CSIRO 2007

Coupled physical-biological modelling study of the East Australian Current with idealised wind forcing. Part I: Biological model intercomparison

A coupled physical-biomechanical Nitrogen-Phytoplankton-Zooplankton (NPZ) model of the pelagic ecosystem is configured for the East Australian Current (EAC). The biomechanical NPZ model uses a combination of physiological and physical descriptions to quantify the rates of planktonic interactions. Physiological rates include the maximum growth rates of phytoplankton and zooplankton, while physical processes include the diffusion of nutrients to phytoplankton cells and the encounter rates of predators and prey. Model simulations are conducted for two different scenarios: a northerly (upwelling favourable) and southerly (downwelling favourable) wind. The model output is compared to satellite derived sea surface colour images and in situ measurements of biological properties. A further comparison is made with output from the commonly used Franks et al. [Franks, P.J.S., Wroblewski, J.S., Flierl, G.R., 1986. Behaviour of a simple plankton model with food-level acclimation by herbivores. Mar. Biol. 91, 121-129] NPZ model with empirical descriptions of planktonic processes. The biomechanical model better captures the formation of a deep chlorophyll maximum during downwelling favourable winds and coastally confined phytoplankton blooms during upwelling favourable winds. A diagnostic tracer is used to interpret the large scale physical-biological coupling, and reveals the importance of the transport and entrainment of upwelled filaments in determining the temporal and spatial trends of biological properties in the waters off south eastern Australia. © 2005 Elsevier B.V. All rights reserved

Biological properties across the Tasman Front off southeast Australia

Physical, geochemical and biological observations across the Tasman Front off southeast Australia provide the first detailed view of the relationship between physical forcing and biological properties within the frontal system. At the beginning of the austral spring of 2004, high resolution measurements were taken using a CTD and a towed undulating vehicle along transects perpendicular to the Tasman Front at 152{ring operator} 00′ E, 153{ring operator} 00′ E and 153{ring operator} 30′ E. The front was characterised by a sharp surface gradient in physical and biological properties and a sub-surface intrusion of low-salinity water. In general the surface temperature changes across the front from 19 {ring operator} C in the Coral Sea waters to the north to 17 {ring operator} C in the Tasman Sea waters over ∼ 10 km. Over the same distance we observed (1) an increase of the mixed layer depth from ∼ 40 to ∼ 100 m; (2) a 3-8-fold increase in the depth-integrated chlorophyll; (3) an order of magnitude increase in biovolume of particulate matter in the size range of 357-2223 μ m; (4) a 2-fold increase in filtered particulate organic matter; (5) a 3 ‰ increase in δ13 CPOM; and (6) a 4 ‰ increase in δ15 NPOM. The particulate matter in the warmer Coral Sea waters is well approximated by a linear fit of the normalised biomass size spectrum (NBSS) with a slope of between - 0.95 and - 0.99, while the Tasman Sea waters have a more non-linear and less negative (- 0.59 to - 0.8) spectrum. The low-salinity intrusion that penetrates to within 40 m of the surface between the Coral Sea and Tasman Sea waters is biologically unproductive, with low oxygen, fluorescence and particulate matter counts. The unproductive low salinity intrusion of the Tasman Front contrasts with the highly productive intrusion observed at the Gulf Stream Front off Cape Hatteras, USA. Observations are consistent with Coral Sea and Tasman Sea waters being found in close proximity with steep gradients in biological properties across the front suggesting minimal cross-front mixing. North of the front, the stratified, oligotrophic Coral Sea waters are relatively unproductive, while the vertically well-mixed waters south of the front exhibit strong biological activity. © 2008 Elsevier Ltd. All rights reserved

Examining the cost effectiveness of interventions to promote the physical health of people with mental health problems: a systematic review

Recently attention has begun to focus not only on assessing the effectiveness of interventions to tackle mental health problems, but also on measures to prevent physical co-morbidity. Individuals with mental health problems are at significantly increased risk of chronic physical health problems, such as cardiovascular disease or diabetes, as well as reduced life expectancy. The excess costs of co-morbid physical and mental health problems are substantial. Potentially, measures to reduce the risk of co-morbid physical health problems may represent excellent value for money