Seawater Turbidity Research Articles

Seasonal Variation of Turbidity in a Fringing Reef Water in Urasoko Bay, Ishigaki Island: Re-suspension due to Northerly Winds

Degradation of coral reef ecosystems are recognized in many areas around the world. Increase of seawater turbidity due to terrigenous sediments is regarded as one of the major cause of the degradation. We investigated levels and temporal variability of the turbidity during a two-year period at Urasoko Bay, a fringing coral reef of Ishigaki Island, Japan. At the near shore station, the median value of the turbidity was 2.26 NTU with the maximum of 92.9 NTU. At the two stations, 150m and 370m offshore, the median values of the turbidity were 0.58 NTU and 0.36 NTU, respectively. Correlation of the turbidity with the precipitation was weak, but wind showed significant correlation with the turbidity. Especially, the wind of the northwestern direction tended to increase the turbidity. These observations suggested that re-suspension of the bottom sediments by the wind driven turbulence and the wind-current with high turbidity and low salinity affected the variability of the turbidity in the Urasoko Bay.

Retrieving seawater turbidity from Landsat TM data by regressions and an artificial neural network

The radiance reflected at the sea surface (RW (λ)) of the Ariake Sea, Japan, was first estimated by subtracting Lowtran 7 estimated Rayleigh and aerosol scattered radiances from Landsat Thematic Mapper measured radiance. Then RW (λ) was averaged from 4×4 pixel windows centred at 33 sampling sites of the Ariake Sea and the data calibrated against the observed Secchi disk depth (SDD) using linear (LR) and nonlinear (NLR) regressions, and an artificial neural network (ANN) algorithm called the Modified Counter Propagation Network (MCPN). We found that at the validation stage, multi-date RW (λ) data that are mainly based on the visible channels of Landsat Thematic Mapper (TM) predict more accurate and dependable SDDs than single-date RW (λ) data. Furthermore, the NLR describes the SDD/RW (λ) relationship more closely than the LR. As an ANN, MCPN possesses non-linearity, inter-connectivity, and an ability to learn and generalize information from complex or poorly understood systems, which enables it to even better represent the SDD/RW (λ) relationship than the NLR. Our study confirms the feasibility of retrieving SDD (or turbidity) from Landsat TM data, and it seems that the calibrated MCPN and possibly NLR are portable temporally within the Ariake Sea. Lastly, the coefficient of efficiency Ef is a more stringent and probably a more accurate statistical measure than the popular coefficient of determination R 2.

Effects of oil and bioremediation on mussel (Mytilus edulis L.) growth in mudflats

Mussels (Mytilus edulis L.) were exposed to crude oil during a field experiment to evaluate two bioremediation strategies (nutrient addition and nutrient addition with tilling). The mussels were placed in 4 mesocosms: Control, Oil, Oil + Nutrients, and Oil + Nutrients + Tilled. Tilling appeared to be clearly detrimental to mussel growth. Additionally, this field experiment demonstrated that at temperatures below 5°C, growth was reduced to rates undetectable by the laser diffraction method. The data on mussel shell length show that this technique does offer very sensitive and useful comparative measurements of physiological function. Measurement of shell growth has the advantage over other techniques in that it is non‐invasive and non‐destructive and thus may be used continuously without disturbing critical physiological and biochemical functions; however, bivalve physiology is strongly linked to environmental conditions, so it is important to include such measures (i.e. seawater temperature and turbidity) in the design of the biomonitoring program. Elevated polycyclic aromatic hydrocarbon (PAH) levels reflected bioaccumulation in mussels from all the oiled mesocosms. This correlated with reduction in growth rate. Maximum reduction in growth was observed in mussels from the tilled mesocosm which contained the lowest phenanthrene and dibenzothiophene concentrations. The tilling caused an increase in suspended solids which inhibited filter feeding activity, and resulted in suppressed growth and slower intake of PAH‐laden sediment.

Inhibition of seawater on bisphenol A (BPA) degradation by Fenton reagents

To investigate bisphenol-A (BPA) degradation in seawater using Fenton reagents, changes in the BPA recovery and in the concentration of BPA metabolite, BPA- o-quinone in the three water samples; BPA free deionizad water (control water), 3% aq. NaCl and seawater as a function of time after BPA fortification in the presence of radical oxygen species (ROS) at 20 °C were investigated. The BPA recoveries were lower in both 3% aq. NaCl and seawater than in the control water. The BPA recovery in aq. NaOCl decreased as a function of NaOCl concentration, indicating that BPA could be degraded by the potent radical ion (OCl −) at the concentration of above 2 μM. A BPA metabolite, BPA- o-quinone was formed in all the water samples after addition of ROS which was produced by Fenton reaction (reaction of 0.11 M H 2O 2 and 0.44 mM FeCl 3·6H 2O). These results indicated that BPA degradation could occur by an addition of ROS and further accelerated by the formation of OCl − in salt containing water samples. BPA recovery was the highest in seawater immediately after addition of Fenton reagents and the amount of BPA- o-quinone was very low, which suggests that seawater possesses an inhibitory system on BPA degradation. There was a positive correlation ( p<0.01) between the fortified iron concentration and turbidity in seawater. Turbidity might be originated from iron-binding substances. Degradation threshold of BPA was observed when Fenton reaction was employed in seawater fortified with high amount of BPA. The present study suggested that iron trapping caused an inhibition on BPA degradation by Fenton reagents.

Monitoring of labile metals in turbid coastal seawater using diffusive gradients in thin-films.

Diffusive gradients in thin-films (DGT) have been investigated for in situ monitoring of labile metals in north Australian coastal seawater. Field and experimental data showed that DGT devices provided adequate detection limits, accuracy and precision for monitoring of near-pristine levels of labile Mn, Co, Cu, Cd and Pb when deployed for periods of 3 days. However, Zn could not be adequately determined due to high blank levels. The ratio of DGT-labile to 0.45 microm-filtered metal levels in natural seawater ranged from 0.44-0.63 for Cu but was close to unity for Co and Cd. Elevated levels of suspended particulate matter up to 57.3 mg l(-1) did not have an adverse effect on the performance of DGT.

Distribution patterns of the sublittoral epibenthic assemblages on a rocky shoal in the Ligurian Sea (NW Mediterranean)

Acquiring baseline data on highly diverse communities such as coralligenous ones is very valuable in order to determine possible shifts in communities and define strategies for their preservation. Distribution of sciaphilic epibenthic communities belonging to the `coralligene de la roche littorale´ was investigated at 30 photostations from 17 to 24 m depth on a rocky shoal off the island complex in the Gulf of La Spezia (Ligurian Sea, NW Mediterranean). Four communities displayed a sharp zonation: Paramuricea clavata characterised deeper, vertical surfaces, whereas on horizontal and medium inclination, sediment-covered substrata, Leptogorgia sarmentosa , together with Eunicella singularis and Eunicella verrucosa , characterised the upper stratum of the deeper community. Shallow vertical walls were characterised by a facies with sponges and zoantharians, whereas community dominated by large, massive colonies of Pentapora fascialis with a basal stratum of sciaphilic algal species patched with sediment on shallow rocky slopes of medium inclination. Bathymetric distribution of assemblages is influenced by high seawater turbidity (mean annual transparency: 11.9 ± 5.7 m at the western site, 6.2 ± 1.6 m at the eastern site), which induces a shift of the upper limit of distribution of these facies to unusually shallow depths. Quantitative data provide a baseline on the study site that will be useful to understand the influence of not only biotic and abiotic factors, but also mass-mortality events, particularly on these communities characterised by high resilience.

The intensity of scattered light in turbid seawater is a major factor in the turbiditaxis of Japanese anchovy larvae

SUMMARY: Positive taxis toward turbid seawater (turbiditaxis) is a well-known key factor in the formation of Shirasu (Japanese anchovy larvae, Engraulis japonicus) fisheries in coastal waters. The physical characteristics of turbid seawater, including color, particle size, underwater light intensity, and scattered light intensity, were studied to examine the mechanism by which turbidity lures the larvae using four food colors, polishing powder, and five water colors. The results of taxis tests comparing turbid materials with different characteristics, led to the conclusion that the scattered light intensity of turbid seawater was the key factor causing positive turbiditaxis in anchovy larvae.

The effect of temperature, pressure, and salinity on sound attenuation in turbid seawater

The acoustic attenuation coefficient in shallow coastal waters is of interest to designers and operators of devices such as naval mine-hunting sonars, sidescan surveying sonars, and acoustic Doppler current profilers, typically employing frequencies ranging from tens of kHz to several hundred kHz, possibly up to 1 MHz. At these frequencies attenuation due to suspended particulate matter which characterizes turbid coastal waters is an important contribution to the total attenuation coefficient. In this paper the effect of temperature, pressure, and salinity on the total attenuation coefficient for seawater containing a suspension of solid particles is investigated by employing suitable expressions for the sound speed, density, and viscosity of seawater as functions of temperature, salinity, and pressure. Results presented demonstrate that while there is little variation in the attenuation with pressure in up to a few hundred meters of water, there is significant variation with temperature and salinity over the ranges found globally in the sea.

Tailings disposal at a marine placer mining operation by WestGold, Alaska

From 1985 to 1990 WestGold managed a marine placer mining operation with substantial documentation concerning its submarine tailings disposal (STD) system. For 5 years the operation involved the use of a floating bucket‐ladder dredge with an integrated, gravity‐based treatment plant to extract free particulate gold from the seabed gravels. Three‐quarters of the throughput was disposed of at 1.5 m below sea level through two pipes, each of 0.51‐m diameter. The system's design resulted from considerable trial and error and modeling studies to achieve regulated seawater conditions. The information is publicly available as a result of a very open permitting and operating process. The mining permit specified waste discharge controls and. environmental impact limits for topics of local concern: the dredge's effluents, the red king crab population (an important fishery resource), seawater turbidity, and bioaccumulation of trace metals, especially mercury (a remnant of prior beach mining). The impact on crab stoc...

海中の濁りの藻場への影響 ＩＩＩ 褐藻類ワカメ・カジメ遊走子群の分散に及ぼす海中懸濁粒子の影響

The dispersion of zoospores in a horizontal direction is considered to be the sum of their own swimming power and the effect of eddy currents, while in the vertical direction it is regarded as a uniform movement sedimentation. If the total number of liberated zoospores is regarded as 100%, the relative number of zoospores showed 0.047%/cm right below the zoospore liberation point and 0.020%/cm at a point 10m away from there. Furthermore, the dispersion range of zoospores became wider in the seawater as turbidity increased, while the number of zoospores settling on the bottom decreased; when the sea water turbidity was more than 2mg/l, the density of settled zoospores was 0.023%/cm right below the zoospore liberation point. Meanwhile, the formational range of kelp beds is also largely reduced in accordance with increasing turbidity. When the turbidity is 10mg/l, the area of kelp beds is estimated to reduce to less than 1/10 of its ordinary area under normal turbidity.

Florisphaera profunda, a possible nannoplankton indicator of late Quaternary changes in sea-water turbidity at the northwestern margin of the Pacific

Three piston cores from the Ryukyu Trench slope, northwestern margin of the Pacific Ocean, contain nearly continuous paleoceanographic records of the last 320, 165 and 105 kyr. Ages of the cores are constrained by plankticδ 18O stratigraphy and roughly substantiated by the presence of two calcareous nannofossil events. Spectral analysis of the changes in relative abundance of Florisphaera profunda, a nannoplankton species presently living in the lower euphotic zone, reveals a maximum power at ∼0.01 cycles/kyr, corresponding to the ∼ 100 kyr/cycle of orbital eccentricity. Much lower power is observed at the ∼ 23 kyr precessional band. This differs from the equatorial Atlantic Ocean variations, which show dominant power in the ∼ 23 kyr precessional band in the changes of F. profunda abundances ( Molfino and McIntyre, 1990a). Besides, our cores were taken outside the equatorial divergence zone. We also show a rather close relationship between F. profunda abundance and sea-water transparency (Secchi depth) in the present northwest Pacific, based on data from 204 sites of surface sediment samples. Because sea-water transparency is primarily affected by bio-productivity change in open ocean, stratigraphic changes of F. profunda abundances in our cores seem to have been caused by productivity change as well pointed out by Molfino and McIntyre (1990a,b). A mechanism proposed by them for its change, however, is not applied to our cases due to differences in spectral analysis results and in geographic situation. Alternatively, we suggest that geographic change of the northwestern margin of the Pacific during the late Quaternary caused F. profunda abundance change through the sea-water turbidity change which has been affected not only by bio-productivity but also by land-origin particles supply.

Improved Method of Enumeration of Attached Bacteria for Study of Fluctuation in the Abundance of Attached and Free-Living Bacteria in Response to Diel Variation in Seawater Turbidity

Sample preparation for enumerating attached bacteria in turbid seawater by epifluorescence microscopy was improved by treating samples with a surfactant (Tween 80) followed by sonication. With optimal treatment with Tween 80 (final concentration, 10 ppm [10 mug/ml]) and sonication, as many as 10 times more attached bacteria were enumerated from turbid seawater relative to the number enumerated from an untreated control. Dispersion of bacteria by sonication alone resulted in the enumeration of only 42 to 72% of the attached bacteria. By this technique, fluctuations in the number of attached and free-living bacteria were determined in water from Aransas Pass, Tex., where surface sediments are resuspended on a regular basis by tidal currents. The abundance of attached bacteria increased in proportion to the seawater turbidity that resulted from sediment resuspension. The variation in abundance of free-living bacteria was not directly related to seawater turbidity. However, the magnitude of fluctuation in the abundance of free-living bacteria was related to the extent of turbidity variation during diurnal tides.

褐藻類カジメ・ワカメの遊走子の沈降速度および基質着生に及ぼす海中懸濁粒子の影響

In order to find out any influence on the seaweed-bed exerted by sea water turbidity, the occurrence of seaweed zoospores adsorbed into suspended matters during their spent season, and the sedimentation velocity of those zoospores combined with suspended matters, and also the probability of their insertion on a base-plate were examined. In the experiment, Ecklonia cava and Undaria pinnatifida were used for the seaweeds and Kaolinite for the material of suspended matters. As a result, it had been concluded that the occurrence of zoospores adsorbed into suspended matters has nothing to do with whether they have flagella or not and the attainability of such adsorption escalates with turbidity concentration; that the sedimenta-tion velocity of zoospores themselves in the filtered sea water is in a range from 0.65 to 0.90cm but it decreases when they are adsorbed into suspended matters; that the insertion of zoospores on the base-plate is disturbed not only by their adsorption into suspended matters but also by suspended matters themselves adhered on the plate.

Analysis of the characteristics of a two-fiber sensor for monitorship of a turbid medium

Certain characteristics of a two-fiber sensor device, of the type proposed by Papaet al. for sea water turbidity monitorship, are examined. The extension of medium from which most of the received backscattered power originates is investigated, together with possible effects of multiple scattering on the received power. Laboratory measurements testing the results of the analysis are reported.

Controls on Early Cretaceous Carbonate Platform Margin Development: Northeastern Gulf of Mexico: ABSTRACT

A seismic stratigraphic analysis of approximately 3000 km of multifold reflection data correlated to available geologic information documents the development of an Early Cretaceous carbonate platform margin in the De Soto Canyon area of the northeastern Gulf of Mexico. During the Jurassic(.), inferred oceanic and thin transitional crust underlying the Gulf subsided and formed a flexure zone on which the Early Cretaceous margin developed. By the late Aptian to late Albian, two types of margin morphologies evolved in response to different paleogeographic settings. Northwest of De Soto Canyon, a gently dipping accretionary slope morphology formed as a result of its proximity to a terrigenous clastic province. Seawater turbidity and chemistry probably inhibited buildup formation on this leeward margin, thus allowing both carbonate and siliciclastic sediments to be transported from the platform interior to the adjacent slope. Southeast of De Soto Canyon, the carbonate province was cleaner and a steeply dipping bypass slope morphology formed due to the development of robust buildups that probably limited downslope deposition of platform-derived sediments, thereby gradually starving the adjacent basin. Total tectonic subsidence profiles across both types of margin morphologies show steeper gradients associated with the bypass slope morphology, suggesting that differential subsidence rates contributedmore » to the development of the margin's morphology and may reflect the margin's proximity to the oceanic-continental crust boundary. In the late Albian, the platform interior drowned in response to a pronounced fluctuation in short-term eustatic sea level superimposed on a long-term rise. Buildups continued to form at the margin, however, until they drowned in the middle Cenomanian due to another big change in short-term eustatic sea level combined with down-to-basin faulting and the continuing long-term rise.« less

Effect of ship scrapping activities on the soil and sea environment in the coastal area of Chittagong, Bangladesh

Ship scrapping activities pollute the soil and sea water environment in the coastal area of Foujderhat to Kumira of Chittagong District, Bangladesh mainly through the discharge of various refuse materials and metal fragments from the scrapping of ships. As a result, toxic concentration of ammonia for marine organisms was found in both beach soil and sea water with an increase in pH. Extensive human and mechanical activities accelerate the rate and amount of sea shore erosion and results in higher turbidity of sea water. Critical concentration of DO and higher BOD were found with an abundance of floatable materials (grease balls and oil films) in the sea water.

The response of the upper ocean to solar heating. I: The mixed layer

The results of two earlier papers on convection in the mixed layer and on the solar heating profile are here introduced into a one-dimensional model in order to investigate the following consequences of the daily cycle of solar heating in the upper ocean: 1. the daytime convection depth becomes less than the turbocline depth; 2. the convective power supply to turbulence in the mixed layer is reduced; 3. the mixed layer below the convection layer becomes stably stratified; 4. the depth of the turbocline is reduced, leaving a diurnal thermocline between it and the top of the seasonal thermocline; 5. the heat content and potential energy of the diurnal and seasonal thermoclines are increased, slowing down the subsequent nocturnal descent of the turbocline. These diurnal changes are illustrated by integrating a one-dimensional model forced by the astronomical cycle of solar heating and seasonal variation of surface meteorology derived from Bunker's climatology. The model is integrated for 18 months to show the seasonal modulation of the diurnal cycle. Nocturnal convection plays a dominant role. The convection depth closely follows the thermal compensation depth during the day when they are less than the turbocline depth. Integrating the model with a 24-hour time step leads to large errors in the seasonal variation of mixed layer temperature and depth, and in the source term of isopycnic potential vorticity. The errors are reduced by using two time steps per day, one for the daytime when convection is quenched, the other for the night when it is active. A novel parametrization based on tuning the daily equivalent solar elevation to surface temperature further reduces the error. This parametrization is used to investigate the sensitivity of the seasonal cycles of mixed layer depth and temperature to: (1) seasonality in the surface fluxes; (2) systematic changes in the net annual solar heating; (3) random changes in the seasonal cycles of solar heating induced (i) monthly and (ii) daily. The sensitivity to uncertainty in seawater turbidity is investigated in the same way. The profile of isopycnic potential vorticity subducted into the thermocline depends on the vernal correlation of mixed layer depth and density, so gyre circulation is sensitive to solar heating in spring.

The response of the upper ocean to solar heating. I: The mixed layer

AbstractThe results of two earlier papers on convection in the mixed layer and on the solar heating profile are here introduced into a one‐dimensional model in order to investigate the following consequences of the daily cycle of solar heating in the upper ocean:1. the daytime convection depth becomes less than the turbocline depth;2. the convective power supply to turbulence in the mixed layer is reduced;3. the mixed layer below the convection layer becomes stably stratified;4. the depth of the turbocline is reduced, leaving a diurnal thermocline between it and the top of the seasonal thermocline;5. the heat content and potential energy of the diurnal and seasonal thermoclines are increased, slowing down the subsequent nocturnal descent of the turbocline.These diurnal changes are illustrated by integrating a one‐dimensional model forced by the astronomical cycle of solar heating and seasonal variation of surface meteorology derived from Bunker's climatology. The model is integrated for 18 months to show the seasonal modulation of the diurnal cycle. Nocturnal convection plays a dominant role. The convection depth closely follows the thermal compensation depth during the day when they are less than the turbocline depth. Integrating the model with a 24‐hour time step leads to large errors in the seasonal variation of mixed layer temperature and depth, and in the source term of isopycnic potential vorticity. The errors are reduced by using two time steps per day, one for the daytime when convection is quenched, the other for the night when it is active. A novel parametrization based on tuning the daily equivalent solar elevation to surface temperature further reduces the error. This parametrization is used to investigate the sensitivity of the seasonal cycles of mixed layer depth and temperature to: (1) seasonality in the surface fluxes; (2) systematic changes in the net annual solar heating; (3) random changes in the seasonal cycles of solar heating induced (i) monthly and (ii) daily. The sensitivity to uncertainty in seawater turbidity is investigated in the same way. The profile of isopycnic potential vorticity subducted into the thermocline depends on the vernal correlation of mixed layer depth and density, so gyre circulation is sensitive to solar heating in spring.

Simulation of the mixed layer at OWS November and Papa with several models

The Mellor‐Yamada level‐2 and 2 1/2, Niiler, and Garwood one‐dimensional mixed‐layer models were compared for some simple forcing experiments and were tested by simulating changes in the mixed layer at ocean stations November and Papa for the year 1961. The ocean station simulations show that the models can be tuned to give fairly good results. However, the need to readjust model constants when changing locations suggests that there is room for improving some of the mixing parameterizations. The sensitivity of the model simulations to certain “external” parameterizations, including surface heat flux, seawater turbidity, and ambient diffusivity below the mixed layer, was investigated. The year‐long simulations were found to be very sensitive to the seawater turbidity. Increasing the turbidity from Jerlov optical type I to type III causes a maximum increase in the monthly mean SST at November of 3°C or more. The simulations are most sensitive to seawater turbidity during summer when the mixed‐layer remains shallow. For the ambient diffusivity a decrease from 0.4 to 0.01 cm2/s results in a maximum increase in the monthly mean SST at November and Papa of 0.5 and 1.5°C, respectively. The effects of using a constant ambient diffusivity are most noticeable in late summer when the seasonal thermocline is strongest. The effects are larger at Papa than at November because of the stronger summer seasonal thermocline at Papa. Best results at November and Papa were obtained by using the observed optical water types (I and II, respectively) and relatively small values for ambient diffusivity (less than 0.2 cm2/s).

A system for taking a representative sample from a large volume of turbid surface sea water for trace element determinations

The sampler is designed for use in routine monitoring of dissolved and particulate trace metals (Zn, Cd, Pb, Cu, Sb and Bi) in turbid sea water. By continuous horizontal sampling, the 5-l volume of sea water actually collected is representative of a very large volume (3000 1). The system includes pumping and filtration apparatus, suitable for use by unskilled operators, to collect small liquid and particulate samples in a closed system precluding atmospheric contamination. Filtration (0.45-μm filter) under pressure makes it possible to collect 50–100 mg of suspended matter from shallow water within 45 min. Tests under routine working conditions show satisfactory results.