REMOTS monitoring of dredging, disposal, sand mining, and organic enrichment on the Hong Kong shelf

Rhoads, Donald C.; Valente, Raymond M.; Germano, Joseph D.; Hilbig, Brigitte; Hodgson, G. W.; Evans, Nathan R.

doi:10.1109/oceans.1995.528539

Cited by 2 publications

(2 citation statements)

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“…Anthropogenic impacts from fish farming and oil spills have been shown to have a large impact on marine ecosystems (Rhoads et al, 1995;Germano et al, 2011;Sweetman et al, 2014). Under fish farms, for example, the benthos receives a high input of particulate organic matter, which raises microbial metabolism and enhances nutrient fluxes across the sediment and the water column (Graf et al, 1982;Holmer and Kristensen, 1992) and can lead to changes in benthic biodiversity and ecosystem function (Alongi et al, 2009;Sweetman et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

“…As a result of the ability to rapidly identify benthic conditions with the SPI-camera, this cheaper and more efficient method soon became widely utilised for assessing benthic community health (Rhoads and Germano, 1982;Germano et al, 2011). Nowadays, the SPI system is used to assess the impact of aquaculture (Karakassis et al, 2002;Mulsow et al, 2006;Callier et al, 2008), trawling (Rosenberg et al, 2003), sewage effluent (Makra et al, 2001), and oil spills (Germano, 1995;Rhoads et al, 1995) on the benthos. Furthermore, the SPI system is a recommended method for assessing the quality of benthic environments for marine spatial management and environmental decision-making (O'Connor et al, 1989;Rosenberg et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

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Sediment Profile Imaging: Laboratory Study Into the Sediment Smearing Effect of a Penetrating Plate

et al. 2021

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Sediment profiling imaging (SPI) is a versatile and widely used method to visually assess the quality of seafloor habitats (e.g., around fish farms and oil and gas rigs) and has been developed and used by both academics and consultancy companies over the last 50 years. Previous research has shown that inserting the flat viewport of an SPI camera into the sediment can have an impact on particle displacement pushing oxygenated surface sediments to deeper sediment depths and making anthropogenically-disturbed sediment appear healthier than they may actually be. To investigate the particle displacement that occurs when a flat plate is inserted into seafloor sediments, a testing device, termed the SPI purpose-built sediment chamber (SPI-PUSH) was designed and used in a series of experiments to quantify smearing where luminophores were used to demonstrate the extent of particle displacement caused by a flat plate being pushed into the sediment. Here, we show that the plate of the SPI-PUSH caused significant smearing, which varied with sediment type and the luminophore grain size. The mean particle smearing measured directly behind the inserted plate was 2.9 ± 1.5 cm for mud sediments with sand-like luminophores, 4.3 ± 2.5 cm for fine sand sediments with sand-like luminophores and 1.9 ± 1.1 cm for medium sand sediments with mud-like luminophores. When the mean depth of particle smearing was averaged over a larger sediment volume (11 cm3) next to the inserted plate, substantial differences were seen between the plate-insertion experiments and controls highlighting the potential extent of smearing artefacts that may be produced when a SPI camera penetrates the seafloor. This experimental data shows that future studies using the SPI camera, or any other periscope-like device (e.g., planar optodes) need to acknowledge that smearing may be significant. Furthermore, it highlights that a correction factor may need to be applied to these data (e.g., the depth of apparent redox potential discontinuity layer) to correctly interpret SPI camera images and better determine the effect of anthropogenic impacts on seafloor habitats.

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