photic zone

(redirected from Euphotic depth)

photic zone

[′fōd·ik]
(ecology)
The uppermost layer of a body of water (approximately the upper 330 feet or 100 meters) that receives enough sunlight to permit the occurrence of photosynthesis.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
A factor of 1.9 between Secchi depth and euphotic depth was assumed based on Kalff's (2002) review of the relationship for clear water lakes, such as Bonilla, in order to estimate the relationship between mixing and euphotic depths.
That means that mixing depth is greater than euphotic layer in this lake, and the ratio of euphotic depth to mixing depth varied between 0.1 when it overturned up to 0.6 especially during stratified periods.
where B is chlorophyll-a concentration, [k.sub.par] is vertical diffusion attenuation coefficient for euphotic depth ([Z.sub.eu]), and D is the day length given as input to the model.
(ii) Euphotic Depth. Downwelling irradiance at each depth of the Ocean during cruise period was obtained from [E.sub.d] and SPMR sensor of Satlantic radiometer when it was operated in free fall mode.
Being a function of [K.sub.d,PAR], the euphotic depth varied from 1.8 to 4.6 in the inshore areas and from 2.1 to 7.0 m in the offshore areas of Peipsi with corresponding average values of 3.0 and 3.8 m (Fig.
Phytoplankton growth has been found to be negative when the depth of the mixture is more than four times greater than the euphotic depth (Talling, 1986).
Water transparency was determined with a Secchi disk and euphotic depth with a submarine photometer.
Several investigators have used the concept of a euphotic depth to calculate phytoplankton carrying capacities under light-limited conditions (e.g., Talling 1965, Jewson 1977, Reynolds 1984).
Although the question of depth scaling for aquatic productivity has not been directly addressed previously, there is indirect evidence that under steady-state, nutrient-rich conditions, phytoplankton growth and biomass often adjust such that euphotic depth corresponds with mixed-layer depth (Wofsy 1983).
Date Surface water [Z.sub.SD] (m) temperature ([deg]C) 8-08-05 29 0.51 27-08-05 31.5 0.55 8-10-05 31.1 0.53 15-10-05 31 0.50 29-10-05 28.5 0.55 19-11-05 26.4 0.55 15-12-05 33.3 0.6 9-01-06 22.8 0.51 5-02-06 ND 0.52 1-03-06 30.1 0.55 25-03-06 ND 0.58 26-04-06 24.2 0.35 Date [K.sub.d] (units m) [Z.sub.eu] (m) 8-08-05 2.82 1.63 27-08-05 2.62 1.75 8-10-05 2.72 1.69 15-10-05 2.88 1.59 29-10-05 2.62 1.75 19-11-05 2.62 1.75 15-12-05 2.4 1.92 9-01-06 2.82 1.63 5-02-06 2.77 1.66 1-03-06 2.62 1.75 25-03-06 2.48 1.85 26-04-06 4.11 1.12 ND Not Determined Table 1:Surface Water Temperatures ([deg]C), Secchi depths ([Z.sub.SD]), Mean vertical extinction coefficients ([K.sub.d]) and Euphotic depths ([Z.sub.eu]) of the central station in Lake Kuriftu August, 2005 to April 2006).