Effects of algae on the Secchi transparency of the southeastern Mediterranean Sea

Megard, Robert O.; Berman, T.

doi:10.4319/lo.1989.34.8.1640

Cited by 56 publications

(41 citation statements)

References 36 publications

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“…Megard & Berman (1989) showed that in this region of the Eastern Mediterranean, l % light level is 3.04 times the Secchi disk depth (SDD) and the 0.1 % light is at 4.56 times the SDD. Thus it was calculated that 1 % of the light penetrated to 91 m at the core and to 75 m at the boundary and 0.1 % to 137 and 112 m respectively.…”

Section: Resultsmentioning

confidence: 99%

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Buildup of microbial biomass during deep winter mixing in a Mediterranean warm-core eddy

Zohary¹,

Brenner²,

Krom³

et al. 1998

Mar. Ecol. Prog. Ser.

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The Cyprus Eddy, a warm-core eddy southeast of Cyprus, was sampled towards the end of an exceptionally cold winter in early March 1992, within 4 d of a storm and w~thin 24 h of an intrusion of cold air. Depth profiles of temperature, salinity and dissolved nutrients showed an active deep mixed layer from the surface to ca 500 m at the core of the eddy, while at the eddy boundaries the mixed layer extended only to 150 m. Microb~al populations were evenly distributed over the entire upper 500 m at the core station, as iiidicated by chlorophy!! and high performance liquid chromatography (HPLC)-determined pigment composition, by flow-cytometric analysis of the ultraphytoplankton, by direct counts of 4',6-diam~dino-2-phenylindole (DAP1)-stained bacter~a and %-thymidine measurements of bacterial activity. As far as we know, thls is the first deta~led description of the microbial populations in a warm-core eddy during the bloom season. The integrated water column chlorophyll content, 59 mg m-2 at the core and 45.5 mg m-2 at the boundary, was more than double the typical late autumn values, suggesting a bloom was occurring. Noticeably, this bloom was not delayed until the establishment of summer stratification as has been observed previously in warm-core eddies. While theoretical considerations based on the calculated critical depth at the core of about 300 m suggested that a bloom should not have occurred, our data jointly with previous data from the Cyprus Eddy support the hypothesis that interim periods of quiescence between mixlng events enable bloom development even when the mixing depth is greater than the critical depth. Added nutrients and dilution of grazers, both resulting from the deep mixing, probably contributed jointly to the enhanced productivity. Based on phytoplankton 11ght-shade adaptation features and cellular chlorophyll fluorescence per cell, we calculated that the rate of vertical mixing in the core was at least 30 m h-'

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Section: Resultsmentioning

confidence: 99%

“…The depths to which 1 and 0.1 % light penetrated were calculated from Secchi depth using equations developed for Eastern Mediterranean water and given in Megard & Berman (1989).…”

Section: Methodsmentioning

confidence: 99%

Buildup of microbial biomass during deep winter mixing in a Mediterranean warm-core eddy

Zohary¹,

Brenner²,

Krom³

et al. 1998

Mar. Ecol. Prog. Ser.

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“…Although more sophisticated instruments are commercially available, Secchi disks are still being widely and regularly utilized to measure water transparency for oceanography and limnology. Secchi disk depth (SDD) is a relative indicator of the vertical visual clarity of light and also an indicator of trophic level [8][9][10][11]. …”

Section: Introductionmentioning

confidence: 99%

MODIS-Based Mapping of Secchi Disk Depth Using a Qualitative Algorithm in the Shallow Arabian Gulf

Kaabi¹,

Zhao²,

Ghedira³

2016

Remote Sensing

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Abstract:Regionally calibrated algorithms for water quality are strongly needed, especially for optically complex waters such as coastal areas in the Arabian Gulf. In this study, a regional qualitative algorithm was proposed to retrieve seawater transparency, with Secchi disk depth (SDD) as a surrogate, in the Arabian Gulf. A two-step process was carried out, first estimating the diffuse attenuation coefficient of downwelling irradiance at 490 nm (K d _490) from MODIS/Aqua imagery and then SDD based on empirical correlations with K d _490. Three satellite derived K d products were tested and assessed against a set of in situ measurements, and one from a semi-analytical algorithm based on inherent optical properties gave the best performance with a R 2 of 0.62. Comparisons between the performances of SDD models developed in this study and those established in other regions indicated higher accuracy of our proposed model for the Gulf region. The potential factors causing uncertainties of the proposed algorithm were also discussed. Seasonal and inter-annual variations of SDD over the entire Gulf were demonstrated using a 14-year time series of MODIS/Aqua data from 2002 to 2015. High SDD values were generally observed in summer while low values were found in winter. Inter-annual variations of SDD did not shown any significant trend with exceptions during algal bloom outbreaks that resulted in low SDD.

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“…1). Los muestreos se realizaron en 6 estaciones durante marzo, mayo, julio, septiembre y diciembre de 2004, obteniendo parámetros como el coeficiente de atenuación vertical de luz difusa [K d (PAR)] mediante la lectura de un disco de Secchi (LDS) y su relación empírica K d (PAR)= 1,3/LDS (Megard & Berman 1989). Asimismo, se calcularon las profundidades de muestreo al 100, 10 y 1% de la irradiancia superficial (E 0 (PAR)) en cada una de las 6 estaciones de acuerdo con la ley de Lambert-Beer.…”

Section: Materiales Y Métodosunclassified

Variabilidad del coeficiente de absorción por fitoplancton con influencia de marea roja en las bahías de Manzanillo y Santiago, México

Sosa-Ávalos

Millán-Núñez²,

Quijano-Scheggia

et al. 2015

Rev. biol. mar. oceanogr.

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Abstract.-Five surveys (March, May, July, September and December 2004) in 6 stations at 3 depths (100, 10 and 1% E 0 (PAR)) were carried out in the bays of Manzanillo and Santiago, Mexico, to detect the temporal variation of water temperature, chlorophyll a concentration and specific absorption coefficient of phytoplankton at 440 nm and 676 nm (a *  (440), a *  (676)). The surface temperature was lower in spring and higher in summer. Meanwhile, the average surface chl orophyll a concentration changed from 1.1 mg m -3 in December to 20.8 mg m -3 in May, while integrated chlorophyll a in the euphotic zone was 36.2 to 146.6 mg m -2 in July and May, respectively. High chlorophyll a recorded in May was different from the other months as a result of harmful algal bloom event dominated by the dinoflagellate Ceratium balechii (Balech 1988) with an average abundance of 1.19 x 10 6 cells L -1 , which represent 95.31% of total phytoplankton. The average values of a *  (440), a *  (676) were 0.051 and 0.029 m 2 (mg Chl a) -1 , respectively, which showed significant temporal variation between months, but had no differences through the euphotic zone. The spectra of the specific absorption coefficient of phytoplankton (a *  ()) for May presented a clear packaging effect into the depths of 100 and 10% E 0 (PAR). The ratio between the maximum blue/red spectral absorption (440 nm/676 nm) showed lower values than 2.5, indicating a phytoplankton community dominated primarily by microphytoplankton cells. Key words: Specific absorption coefficient, chlorophyll a, harmful algal bloom, Manzanillo and Santiago BaysResumen.-Se realizaron 5 cruceros (marzo, mayo, julio, septiembre y diciembre 2004) en 6 estaciones a 3 profundidades (100, 10 y 1% de E 0 (PAR)) en las bahías de Manzanillo y Santiago, México, para detectar la variación temporal de la temperatura, concentración de clorofila a y del coeficiente específico de absorción por fitoplancton a 440 y 676 (a *  (440nm), a *  (676nm)). La temperatura superficial fue menor en primavera y mayor en verano. La media de la concentración superficial de clorofila a cambió de 1,1 mg m -3 en diciembre a 20,8 mg m -3 en mayo, mientras que la clorofila a integrada en la zona eufótica fue de 36,2 a 146,6 mg m -2 en julio y mayo, respectivamente. La alta clorofila a en mayo fue diferente a los otros meses como resultado de un florecimiento algal nocivo dominado por el dinoflagelado Ceratium balechii (Balech 1988) con una abundancia de 1,19 x 10 6 células L -1 , el cual representa el 95,31% del fitoplancton total. Los valores promedio del a *  (440) y a *  (676) fueron de 0,051 y 0,029 m 2 (mg Cla) -1 , respectivamente, los cuales mostraron variación temporal significativa entre los meses, pero no tuvieron diferencias a través de la zona eufótica. Los espectros del coeficiente específico de absorción por fitoplancton (a *  ()) presentaron en mayo un claro efecto de paquete a las profundidades del 100 y 10% de E 0 (PAR). La razón entre los máximos de absorción espectral azul/rojo (440 nm/...

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Effects of algae on the Secchi transparency of the southeastern Mediterranean Sea

Cited by 56 publications

References 36 publications

Buildup of microbial biomass during deep winter mixing in a Mediterranean warm-core eddy

Buildup of microbial biomass during deep winter mixing in a Mediterranean warm-core eddy

MODIS-Based Mapping of Secchi Disk Depth Using a Qualitative Algorithm in the Shallow Arabian Gulf

Variabilidad del coeficiente de absorción por fitoplancton con influencia de marea roja en las bahías de Manzanillo y Santiago, México

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