Turbid Water Bodies Research Articles

Interpreting the colour of an estuary

This paper explores the possibility of using water colour to quantify the concentration of coloured dissolved organic matter (CDOM), and through it, dissolved organic carbon (DOC) and salinity in a turbid estuary in which suspended sediments also influence water colour. The motivation of the work is that the method could be applied to water colour measurements made remotely from an aircraft (or, in larger estuaries, a satellite) enabling near-synoptic mapping of surface salinity and DOC distributions. The paper describes observations at 29 stations distributed along the salinity gradient of the Conwy estuary in North Wales. At each station, surface water samples were collected and analysed for salinity, concentrations of DOC, chlorophyll and suspended particles and absorption spectra of CDOM, or yellow substance. Profiles were made of both upwelling and downwelling irradiance in four narrow band channels, and these were used to calculate irradiance reflection and attenuation coefficients. Results show that spectrally averaged light absorption in the estuary is caused principally and equally by mineral suspended solids and yellow substance, with water and chlorophyll in third and fourth place. The CDOM is strongly correlated ( R 2=0.99) in a negative sense with salinity, and more weakly correlated with DOC. There is a linear relationship between CDOM and the ratio of reflection coefficients in the red (670 nm) and blue-green (490 nm) parts of the spectrum, which could be applied to remote sensing; the slope and intercept of the relationship are however different to those found in less turbid water bodies. It is shown that the change in slope and intercept are consistent with the presence, in the Conwy estuary, of suspended particles which influence the water colour. A method is described and tested for inverting water colour measurements in a turbid estuary to give estimates of CDOM in the presence of suspended particles. The solution, which has not been adjusted to fit the data, produces profiles of CDOM, DOC and salinity, which behave reasonably but which currently have a limited accuracy. RMS differences between measured and optically derived parameters for the entire data set are 0.27 m −1 (CDOM), 4 PSU (salinity) and 67 μM (DOC) although better accuracy is obtained on individual surveys. The fact that there is little bias between predicted and observed parameters indicates that much of the scatter is caused by random measurement error and that the approach is fundamentally sound.

Influence of Bright Bottom Depth on Reflectance from Clear and Turbid Water Bodies

In water bodies, where the bottom is visible to the sensor, remotely sensed data can produce erroneous estimates of water column constituents. The bottom impact depends upon depth and turbidity of the water body, color and composition of the bottom, and the wavelengths of spectral measurement. In the case of clear water, the maximum separability of the composite upwelling signals from bottom at varying depths was recorded in wavelength region between 400 and 900 nm. For water with an algal suspension of 478 □g/l, the maximum separability of upwelling signals was within 500 and 600 nm. In both clear and algal waters, bottom at depths greater than 50 cm did not impact the upwelling signals in wavelength range beyond 744 nm.

Stratification and Circulation in a Shallow Turbid Waterbody

Shallow waterbodies are often assumed to be well mixed in the vertical. However, when they are characterised by high turbidity levels, absoption of solar heating within a relatively thin surface layer can produce thermal stratification. Results from an intensive monitoring program have been combined with three-dimensional circulation modelling to examine the diurnal stratification cycles in a small turbid waterbody. The waterbody, known as Rushy Billabong, is located in southeastern Australia and its high turbidity coupled with forcing by wind and solar radiation resulted in regular diurnal cycles of stratification and overturning. Under conditions of light wind and high solar radiation, the model results were generally consistent with the observed temperature field. However, under stronger winds, preferential cooling and sinking of shallow water around the edge of the lake began to contribute significantly to the interior stratification. Model estimates then became more sensitive to the detailed bathymetry and the choice of turbulence parameterisation. The level of stratification is also shown to influence the circulation in the billabong by trapping the wind-driven flow near the surface. Insights provided by the observations and modelling may have broader implications for the management of small turbid systems such as settling ponds, aquaculture ponds, and some natural wetlands.

Recognition of nutrient and light limitation in turbid mixed layers: Three approaches compared in the Parani floodplain (Argentina)

The potential difficulties of testing for nutrient limitation in turbid mixed layers are illustrated by comparing the outcome of three different approaches (in vitro bioassays, limnocorrals, and whole-lake fertilization) in the subtropical ParanL floodplain. Bioassays of the planktonic communities consistently suggested acute N limitation, no limitation, or P limitation, depending on the time at which we chose to terminate the experiment. Enclosures (17 m*) deployed in one lake indicated N limitation but increased sedimentation and water transparency in the enclosures. Although short-term bioassays consistently indicated limitation by N, whole-lake fertilization produced only a small and transient increase in chlorophyll a and primary production or no response at all. Some lakes are mildly limited by N during summer; others appear to be limited by light. In the latter, bioassays and whole-lake fertilization lead to inconsistent conclusions. A steady state model of phytoplankton biomass (as Chl a) under excess nutrient concentrations is proposed to facilitate the diagnosis of light limitation in shallow and turbid water bodies. Model predictions are consistent with mean column critical irradiance (PAR) of 1.6 MJ m-2 d-l (7.36 Einst m-2 d-l) previously reported for net phytoplankton growth in marine and freshwater systems.

Characteristics of the light field in highly turbid waters: A Monte Carlo study

AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Abstract The nature of the light field in waters with very high ratios of scattering coefficient to absorption coefficient (b : a) has been explored by Monte Carlo modeling. The progressive change in the angular structure of the field at a specified optical depth (zm) as b: a increases up to an extreme value of 200 is illustrated in terms of the changes in average cosines µ̄d[zm], µ̄u[zm], µ̄[zm]) and irradiance reflectance (R[zm]). The dependence of the vertical attenuation coefficient for downward irradiance on absorption and scattering is satisfactorily represented by A nomnogram is presented, with the help of which the values of the absorption and scattering coefficients for highly turbid water bodies can be estimated from underwater irradiance data. Citing Literature Volume39, Issue3May 1994Pages 702-706 RelatedInformation

A model for the light-limited growth of buoyant phytoplankton in a shallow, turbid waterbody

A computer model was used to explore the relationship between buoyancy and the light-limited growth of phytoplankton in very turbid waters. The model simulates the potential growth of phytoplankton as a function of flotation speed, using field observations of photosynthetically active radiation, wind speed, surface-layer thickness (from water-column temperature data), and light attenuation made at Rushy Billabong on the River Murray from 28 November 1991 to 26 March 1992. A unique feature of the model is the simulation of the development and dispersal of surface scums as a function of wind speed. Under nutrient-replete conditions, the model predicted that phytoplankton with a flotation speed of 1-10 m day-1 (typical of Anabaena flos-aquae and Microcystis aeruginosa) would grow up to four times faster than would neutrally buoyant phytoplankton with the same maximum specific growth rate. In the shallow system modelled, high flotation speeds allowed a large proportion of the total population to rise into the euphotic zone shortly after the onset of stratification each day. Surface scums played an important role in maintaining the more buoyant phytoplankton populations close to the water surface. Under the very turbid conditions in the billabong (100 nephelometric turbidity units), self-shading became significant only when the mean chlorophyll concentration in the water column approached 100 mg chla m-3.

Relationship between turbidity and fish diets in Lakes Waahi and Whangape, New Zealand

Abstract Stomach contents of Gobiomorphus cotidianus,Retropinna retropinna, Gambusia affinis, and Anguilla australis were compared between two shallow lakes in the lower Waikato River basin, to examine the relationship between turbidity and diet. Lake Waahi and the south arm of Lake Whangape had been turbid (20–40 g suspended solids (SS) m−3) and devoid of submerged macrophytes since the late 1970s and early 1980s, respectively. The main basin of Lake Whangape had been generally clearer (5 g SS m−3) with dense beds of submerged macrophytes, but at the time of sampling (1987) water clarity had deteriorated (> c. 10 g SS m3) and submerged macrophytes had declined. The mysid Tenagomysis chiltoni was an important prey for all species of fish from turbid water bodies but was less important in stomachs of fish in the main basin of Lake Whangape. Apparently, mysids were not an important prey in Lake Waahi before it became turbid. Chironomid larvae and pupae dominated the diets of small fish in the main basin of ...

Phormidium J-1 bioflocculant: production and activity

Phormidium J-1, a benthic filamentous cyanobacterium, isolated from a drainage channel, was found to produce a high molecular weight polymer. This substance can flocculate bentonite particles from suspensions. At the stationary phase of growth the cells excreted this bioflocculant into the surrounding medium. Production was enhanced by reduction of the calcium content in the growth medium or by increasing its EDTA content. Above the isoelectric point (pH 3.5) the bioflocculant is negatively charged. The presence of minimal concentrations of divalent cations in the reaction mixture is required for its flocculating activity. The production of bioflocculant could be of great importance in clarification of turbid water bodies, thus allowing light penetration to the sediment/water interface. Bioflocculant production and excretion was not found in several other benthic cyanobacteria.

A versatile directional reflectance model for natural water bodies, submerged objects, and moist beach sands

A directional reflectance model is derived that is based upon the same multiple scattering concepts as were employed in a previously published vegetation reflectance model. The scattering phase functions utilize the “model equivalent” Lambertian panel approximation for each scattering species. The model exhibits the property of optical reciprocity and offers consistent procedures for calculating directional reflectance of turbid water bodies of any depth, particulate content, and bottom vegetation cover, as well as the apparent reflectance of an isolated submerged object, such as a Secchi disc. Moist beach sands are considered to be extremely turbid water where air voids are also a scattering species.

Prediction of Radiation Absorption and Scattering in Turbid Water Bodies

In this study four methods of solving the radiative transfer equation applied to shallow ponds have been compared. The methods include a simple version of Beer’s law, a representative two-flux model, a six-flux model and the method of discrete ordinates. Calculations have been performed for a wide range of representative conditions typical to natural water. It was found that scattering was unimportant when the scattering albedo is small (ω ≲ 0.5) and the phase function is highly forward peaked. Consequently, even the simple Beer’s law expression yielded accurate predictions. However, in general only the six-flux method provided a suitable compromise between accuracy and operational convenience for all the conditions considered. The two-flux method was found to be the least accurate primarily due to its inability to account for refraction.

Effects of suspended sediments on photolysis rates of dissolved pollutants

Data are presented concerning the effects of suspended sediments upon photolysis rates of dissolved ultraviolet (u.v.) absorbing pollutants. The malachite green leucocyanide actinometer was found to be a convenient and sensitive device for measurement of solar u.v. radiation (∼ 330 nm) in sediment suspensions. Irradiance measurements by the actinometer were employed to compute diffuse attenuation coefficients for sediment suspensions from six natural water bodies in Georgia, Mississippi, and Montana. Specific attenuation coefficients were remarkably similar for all the sediments examined. Evidence is presented that large underestimates of photolysis rates result when beam attenuation coefficients of turbid water bodies are employed to compute the effects of light attenuation. Finally, it is demonstrated that photolysis rates within the photic zone are generally more rapid in turbid than in clear water. Enhanced photolysis rates in turbid waters are attributed to the increased diffuseness of light caused by scattering.

Mathematisches Modell zur Deutung der durch intermittierende Belichtung von Phytoplanktern hervorgerufenen Mehrleistung der Photosynthese

AbstractIn the turbulent, turbid water body of a river, lake, reservoir or ocean, the light intensity for a phytoplankton individuum is time‐dependent. But current production equations are based on time‐independent light conditions. A mathematical model for the photosynthetic oxygen production under the simple condition of intermittent light is developed. It consists of one nonlinear algebraic and one linear differential equation of the first order. For the photosynthetic apparatus a global effective relaxation time τ is given. The model is proved with the data published by Warburg (1919). It shows, coupled with an empirical relation for τ, a good qualitative and quantitative agreement with experimental results.