scispace - formally typeset
Search or ask a question
Topic

Secchi disk

About: Secchi disk is a research topic. Over the lifetime, 617 publications have been published within this topic receiving 17103 citations.


Papers
More filters
Journal ArticleDOI
16 Aug 2016-Sensors
TL;DR: The commonly used approaches and sensors employed in evaluating and quantifying the eleven water quality parameters, including chlorophyll-a (chl-a), colored dissolved organic matters (CDOM), Secchi disk depth (SDD), turbidity, total suspended sediments (TSS), water temperature (WT), total phosphorus (TP), sea surface salinity (SSS), dissolved oxygen (DO), biochemical oxygen demand (BOD) and chemical oxygendemand (COD).
Abstract: Remotely sensed data can reinforce the abilities of water resources researchers and decision makers to monitor waterbodies more effectively. Remote sensing techniques have been widely used to measure the qualitative parameters of waterbodies (i.e., suspended sediments, colored dissolved organic matter (CDOM), chlorophyll-a, and pollutants). A large number of different sensors on board various satellites and other platforms, such as airplanes, are currently used to measure the amount of radiation at different wavelengths reflected from the water’s surface. In this review paper, various properties (spectral, spatial and temporal, etc.) of the more commonly employed spaceborne and airborne sensors are tabulated to be used as a sensor selection guide. Furthermore, this paper investigates the commonly used approaches and sensors employed in evaluating and quantifying the eleven water quality parameters. The parameters include: chlorophyll-a (chl-a), colored dissolved organic matters (CDOM), Secchi disk depth (SDD), turbidity, total suspended sediments (TSS), water temperature (WT), total phosphorus (TP), sea surface salinity (SSS), dissolved oxygen (DO), biochemical oxygen demand (BOD) and chemical oxygen demand (COD).

554 citations

Journal ArticleDOI
TL;DR: In this article, a new trophic index (TRIX) based on chlorophyll, oxygen saturation, mineral and total nitrogen and phosphorus, and applicable to coastal marine waters, is proposed.
Abstract: In pursuing earlier attempts to characterize the trophic state of inland waters, a new trophic index (TRIX) based on chlorophyll, oxygen saturation, mineral and total nitrogen and phosphorus, and applicable to coastal marine waters, is proposed. Numerically, the index is scaled from 0 to 10, covering a wide range of trophic conditions from oligotrophy to eutrophy. Secchi disk transparency combined with chlorophyll, instead, defines a turbidity index (TRBIX) that serves as complementary water quality index. The two indices are combined in a general water quality index (GWQI). Statistical properties and application of these indices to specific situations are discussed on examples pertaining to the NW Adriatic Sea. It is believed that these indices will simplify and make comparison between different spatial and temporal trophic situations of marine coastal waters more consistent. © 1998 John Wiley & Sons, Ltd.

474 citations

Journal ArticleDOI
TL;DR: The Secchi disk is a circular white disk that is lowered into a natural body of water by a human observer until it disappears from view as mentioned in this paper, which is a visual measure of the clarity of the water.
Abstract: The Secchi disk is a circular white disk that is lowered into a natural body of water by a human observer until it disappears from view. The depth of disappearance is a visual measure of the clarity of the water. This review examines the physical and physiological basis of the Secchi disk procedure. The theory of the white disk is detailed to show the underlying assumptions and the consequent strengths and limitations of the procedure. The theory shows how to use a calibrated Secchi disk to predict illuminance levels as a function of depth. In particular it is shown how to predict the euphotic depth of a medium. Ten laws of the Secchi disk are stated verbally and in mathematical form. The laws show how variations in properties of the disk and the surrounding light field affect the depth of disappearance of the disk. Theory and examples lead to the following three main conclusions of this paper: (i) the Secchi disk reading zs,, (in meters) yields a quantitative estimate of a single apparent optical property (CX + K) (in meter-') of a natural hydrosol, where (Y is the (photopic) beam attenuation coefficient and K the (photopic) diffuse attenuation coefficient of the medium; (ii) the primary function of a Secchi disk is to provide a simple visual index of water clarity via z,, or a! + K, (iii) to extend the use of the Secchi disk by auxiliary objective electronic measurements of a or of K, or both, is to risk obviating or abusing this primary function.

458 citations

Journal ArticleDOI
TL;DR: In the near-shore regions of this shallow lake, low N:P ratios potentially favor blooms of N2-fixing cyanobacteria, but their occurrence in the pelagic zone is restricted by low irradiance and lack of stable stratification.

378 citations

Journal ArticleDOI
Gordon A. Riley1
TL;DR: The average concentration of phytoplankton was sparse, but it extended through a long vertical column, in agreement with previous observations as mentioned in this paper, and the seasonal minimum occurred in autumn, and the population tended to be larger in winter than in summer.
Abstract: U. S. Weather Ship personnel operating at Lat. 35°N, Long. 48°W obtained approximately weekly collections of water samples for phytoplankton enumeration at five depths between 0 and 150 m for a two-year period beginning in February, 1950. Temperature and Secchi disk measurements and zooplankton collections also were made. The average concentration of phytoplankton was sparse, but it extended through a long vertical column, in agreement with previous observations. There was a diatom increase in April of each year, which appeared to be analogous to the vernal augmentation in temperate waters although of miniature size. The seasonal minimum occurred in autumn, and the population tended to be larger in winter than in summer. Destruction of the seasonal thermocline between December and March presumably increased the rate of nutrient supply at that season, but light and turbulence were critical factors. Hence the development of winter diatom pulses was correlated with the stability of the water column. The species composition was mainly subtropical or ubiquitous, but occasional localized concentrations of temperate-water diatoms suggested eddy transfer from the north. Analysis of previous oceanographic observations in the region by three independent methods indicated an average daily rate of net phytoplankton production of about 0.15 g carbon per m2 of sea surface, or a quarter to a third of the observed rates in highly productive temperate waters.

345 citations


Network Information
Related Topics (5)
Water quality
67.1K papers, 945.1K citations
81% related
Vegetation
49.2K papers, 1.4M citations
79% related
Ecosystem
25.4K papers, 1.2M citations
79% related
Sediment
48.7K papers, 1.2M citations
79% related
Surface runoff
45.1K papers, 1.1M citations
76% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202319
202238
202127
202034
201933
201817