scholarly journals Environmental properties of the southern Gulf of Aqaba, Red Sea, Egypt

2012 ◽  
Vol 13 (2) ◽  
pp. 179 ◽  
Author(s):  
M.M. DORGHAM ◽  
M.M. EL-SHERBINY ◽  
M.H. HANAFI
Keyword(s):  
Dissolved Oxygen ◽  
Water Column ◽  
Chlorophyll A ◽  
Red Sea ◽  
Environmental Parameters ◽  
Gulf Of Aqaba ◽  
High Concentration ◽  
Environmental Properties ◽  
Epipelagic Zone ◽  
Deep Layers

Environmental properties (temperature, dissolved oxygen, nutrients and chlorophyll a) of the epipelagic zone off SharmEl-Sheikh, Red Sea, Egypt were studied seasonally throughout a year from March 1995 to March 1996. Water samples werecollected from five water depths (0, 25, 50, 75 & 100 m). The studied parameters exhibited clear seasonal variability along the water column. The vertical distribution of water temperature showed thermal homogeneity during most seasons, and thermal stratification in summer. Dissolved oxygen attained slightly high concentrations (5.3-7.8 mg l-1) in the whole water column, with slight seasonal variation. The concentrations of nutrients reflected dominant oligotrophic conditions in the epipelagic zone and occasional mesotrophic status at some depths. Phosphate fluctuated between 0-0.7 μM, ammonium (0-2.27 μM), nitrite (0-0.72 μM), nitrate (0-1.49 μM) and silicate (0-6.48 M). Phytoplankton biomass was generally low in the epipelagic zone throughout the study, whereas chlorophyll a was less than 0.5 μg l-1, except relatively high concentration (0.7-1.12 μg l-1) in deep layers in spring. In comparison with previous studies on the Gulf of Aqaba all environmental parameters during present study showed pronouncedlydifferent values.

scholarly journals Modelling the biogeochemical effects of heterotrophic and autotrophic N<sub>2</sub> fixation in the Gulf of Aqaba (Israel), Red Sea

2018 ◽  
Vol 15 (24) ◽  
pp. 7379-7401 ◽  
Author(s):  
Angela M. Kuhn ◽  
Katja Fennel ◽  
Ilana Berman-Frank
Keyword(s):  
Water Column ◽  
Red Sea ◽  
N2 Fixation ◽  
Large Scale ◽  
Gulf Of Aqaba ◽  
Nutrient Concentrations ◽  
Nutrient Ratios ◽  
Biogeochemical Models ◽  
Deep Waters ◽  
Direct Measurements

Abstract. Recent studies demonstrate that marine N2 fixation can be carried out without light by heterotrophic N2 fixers (diazotrophs). However, direct measurements of N2 fixation in aphotic environments are relatively scarce. Heterotrophic as well as unicellular and colonial photoautotrophic diazotrophs are present in the oligotrophic Gulf of Aqaba (northern Red Sea). This study evaluates the relative importance of these different diazotrophs by combining biogeochemical models with time series measurements at a 700 m deep monitoring station in the Gulf of Aqaba. At this location, an excess of nitrate, relative to phosphate, is present throughout most of the water column and especially in deep waters during stratified conditions. A relative excess of phosphate occurs only at the water surface during nutrient-starved conditions in summer. We show that a model without N2 fixation can replicate the observed surface chlorophyll but fails to accurately simulate inorganic nutrient concentrations throughout the water column. Models with N2 fixation improve simulated deep nitrate by enriching sinking organic matter in nitrogen, suggesting that N2 fixation is necessary to explain the observations. The observed vertical structure of nutrient ratios and oxygen is reproduced best with a model that includes heterotrophic as well as colonial and unicellular autotrophic diazotrophs. These results suggest that heterotrophic N2 fixation contributes to the observed excess nitrogen in deep water at this location. If heterotrophic diazotrophs are generally present in oligotrophic ocean regions, their consideration would increase current estimates of global N2 fixation and may require explicit representation in large-scale models.

scholarly journals Diel vertical migration of Cladocera in a compartment of a tropical reservoir

2018 ◽  
Vol 30 (0) ◽  
Author(s):  
Erika dos Santos Silva ◽  
Odete Rocha ◽  
Maria José dos Santos-Wisniewski
Keyword(s):  
Dissolved Oxygen ◽  
Water Column ◽  
Chlorophyll A ◽  
Vertical Migration ◽  
Variable Temperature ◽  
Chemical Properties ◽  
Migration Pattern ◽  
Limiting Factor ◽  
Tropical Reservoir ◽  
Physical And Chemical

Abstract Aim This study seeks to analyze the vertical migration pattern of Cladocera species as related with the physical and chemical parameters of the water. Methods Samplings were carried out at 3-h intervals for 24 h in January 15 on the Sapucaí River compartment of Furnas reservoir, Minas Gerais State, Brazil. These samples were taken at five depths, from the surface to the near-bottom layer (0, 2, 4, 6, 8, and 9 m) totalizing 54 samplings for each limnological variable (temperature, pH, dissolved oxygen, electrical conductivity, chlorophyll-a content, Index of Trophic State, water transparency and Cladocera populations abundance). The samplings were performed at the limnetic region at a point with total depth of 9 meters. Results Water column thermal and chemical stratifications and thermocline occurrences were registered in the middle of the day. Among the 14 Cladocera species, only Ceriodaphnia cornuta and C. silvestrii displayed a significant migration pattern, which was mainly related to chlorophyll-a and dissolved oxygen concentrations. Diaphanosoma birgei and D. spinulosum are found at high densities near the surface and low ones in depth. The migration of Diaphanosoma was directly related to the concentration of chlorophyll a and pH, thus acting as a limiting factor. Feeding at high temperatures in the surface layer and assimilating at lower ones in depth, usually confer metabolic advantages to the vertically migratory species. Conclusions In this study, a well-defined pattern of vertical migration was found for two Cladocera species and its possible causes were hypothesized. To the species with less locomotory capacity, thermal and chemical stratifications can act as barriers to migration and distribution through the water column. This pattern may probably be found for zooplankton species in other compartments of Furnas reservoir, with similar physical and chemical properties.

Distribution of bdellovibrios in the water column of an estuary

1984 ◽  
Vol 30 (7) ◽  
pp. 971-974 ◽  
Author(s):  
Henry N. Williams ◽  
William A. Falkler Jr.
Keyword(s):  
Dissolved Oxygen ◽  
Water Column ◽  
Water Samples ◽  
Vibrio Parahaemolyticus ◽  
Environmental Parameters ◽  
Water Columns ◽  
Sampling Times

The distribution of bdellovibrios in the water column of the Miles River has been studied. Water samples were collected every 4 h over a 24-h period from five depths in the water column. The samples were cultured for the recovery of bdellovibrios lytic against Vibrio parahaemolyticus. Environmental parameters, i.e., salinity, temperature, turbidity, and dissolved oxygen (DO) were measured for each sample. Bdellovibrios were observed to be uniformly distributed at all depths measured in the water columns. There were no significant differences between the number of bdellovibrios recovered at the various depths. There were significant differences between the number of bdellovibrios recovered at various sampling times. However, no basis for these significant differences could be established. No association was found between the number of bdellovibrios recovered and the environmental parameters measured. Of interest was the observation that the distribution of the aerobic bdellovibrios did not correlate with DO measurements. The results suggest that neither depth nor DO content influenced the recovery of bdellovibrios from the Miles River.

scholarly journals Major impacts of climate change on deep-sea benthic ecosystems

Elem Sci Anth ◽  
2017 ◽  
Vol 5 ◽  
Author(s):  
Andrew K. Sweetman ◽  
Andrew R. Thurber ◽  
Craig R. Smith ◽  
Lisa A. Levin ◽  
Camilo Mora ◽  
...  
Keyword(s):  
Water Column ◽  
Deep Sea ◽  
Oil And Gas ◽  
Environmental Parameters ◽  
Societal Implications ◽  
Environmental Properties ◽  
Water Formation ◽  
Ne Pacific ◽  
Benthic Ecosystems ◽  
Impacts Of Climate Change

The deep sea encompasses the largest ecosystems on Earth. Although poorly known, deep seafloor ecosystems provide services that are vitally important to the entire ocean and biosphere. Rising atmospheric greenhouse gases are bringing about significant changes in the environmental properties of the ocean realm in terms of water column oxygenation, temperature, pH and food supply, with concomitant impacts on deep-sea ecosystems. Projections suggest that abyssal (3000–6000 m) ocean temperatures could increase by 1°C over the next 84 years, while abyssal seafloor habitats under areas of deep-water formation may experience reductions in water column oxygen concentrations by as much as 0.03 mL L–1 by 2100. Bathyal depths (200–3000 m) worldwide will undergo the most significant reductions in pH in all oceans by the year 2100 (0.29 to 0.37 pH units). O2 concentrations will also decline in the bathyal NE Pacific and Southern Oceans, with losses up to 3.7% or more, especially at intermediate depths. Another important environmental parameter, the flux of particulate organic matter to the seafloor, is likely to decline significantly in most oceans, most notably in the abyssal and bathyal Indian Ocean where it is predicted to decrease by 40–55% by the end of the century. Unfortunately, how these major changes will affect deep-seafloor ecosystems is, in some cases, very poorly understood. In this paper, we provide a detailed overview of the impacts of these changing environmental parameters on deep-seafloor ecosystems that will most likely be seen by 2100 in continental margin, abyssal and polar settings. We also consider how these changes may combine with other anthropogenic stressors (e.g., fishing, mineral mining, oil and gas extraction) to further impact deep-seafloor ecosystems and discuss the possible societal implications.

scholarly journals Impact of an anticyclonic eddy on the summer nutrient and chlorophyll a distributions in the Ulleung Basin, East Sea (Japan Sea)

2011 ◽  
Vol 69 (1) ◽  
pp. 23-29 ◽  
Author(s):  
Dongseon Kim ◽  
Eun Jin Yang ◽  
Kyung Hee Kim ◽  
Chang-Woong Shin ◽  
Jisoo Park ◽  
...  
Keyword(s):  
Water Column ◽  
Chlorophyll A ◽  
Surface Waters ◽  
Japan Sea ◽  
Anticyclonic Eddy ◽  
East Sea ◽  
Ulleung Basin ◽  
Surface Mixed Layer ◽  
High Concentration ◽  
Chl A

Abstract Kim, D., Yang, E. J., Kim, K. H., Shin, C-W., Park, J., Yoo, S., and Hyun, J-H. 2012. Impact of an anticyclonic eddy on the summer nutrient and chlorophyll a distributions in the Ulleung Basin, East Sea (Japan Sea). – ICES Journal of Marine Science, 69: 23–29. The impact of the anticyclonic Ulleung Warm Eddy (UWE) on the vertical distributions of nutrient and chlorophyll a (Chl a) concentrations in the Ulleung Basin (UB) was investigated during the contrasting summers of 2005 and 2007. The physical structure of the water column was characterized by an intrathermocline eddy (ITE) in 2005, whereas the UWE remained distant from the sampling transect in 2007. Water column structures appeared to be highly stratified, and nutrients in the surface waters were totally depleted at all stations. In 2005, an exceptionally high concentration of Chl a (5.5 mg m−3) was measured below the surface mixed layer in the eddy core (station D3), and values of ∼2.5 mg m–3 were observed at the eddy edge (stations D2 and D4). Formation of an ITE efficiently mixed surface and deep-ocean waters, the latter supplying sufficient nutrients to generate an extremely high concentration of Chl a at the base of the subsurface layer. Overall, the results indicated that the anticyclonic UWE plays a key ecological role in supporting substantial phytoplankton biomass in the nutrient-depleted surface waters in summer and maintaining high benthic mineralization in the deep-sea sediments of the UB.

scholarly journals Phytoplankton in relation to water quality of Tanguar Haor ecosystem, Bangladesh: 2. Watch tower station

2020 ◽  
Vol 29 (1) ◽  
pp. 9-18
Author(s):  
Mohammad Azmal Hossain Bhuiyan ◽  
Abu Kowser ◽  
Sam Shariar Islam ◽  
Md Rasikul Islam ◽  
Mahin Mohid ◽  
...  
Keyword(s):  
Water Quality ◽  
Dissolved Oxygen ◽  
Chlorophyll A ◽  
High Concentration ◽  
Phytoplankton Population ◽  
A Value ◽  
Significant Difference ◽  
The Mean ◽  
Two Parameters

Phytoplankton biomass in relation to some environmental and nutritional parameters at Watch Tower Station of Tanguar and Rauar Station has been studied. Since the Haor is a Ramsar Site, it is a globally important aquatic ecosystem. In the present investigation, the structure of the phytoplankton and the water quality factors were worked out and the data were compared Rauar Station with having the same ecosystem. Though weaker, a difference among alkalinity, total dissolved solids (TDS), conductivity, dissolved oxygen (DO), Secchi disc transparency, soluble reactive phosphorous (SRP), soluble reactive silicate (SRS), NO3-N, NH4+, chlorophyll-a and phytoplankton population density was found between the Watch Tower and the Rauar Station of Tanguar Haor. The mean values of the aforsaid parameters were found to some extent higher in the Watch Tower Station. The Watch Tower Station was deeper and perennial, where the depth of water varied from 3.0 - 9.5 m annually with a mean of 6.72 m. In the studied station, air and water temperature varied from 22.6 - 30.6 and 22.7 - 30.3°C, respectively. Water transparency ranged from 2.08 - 3.0 m. From December to March the pH remained 8.1-9.7 and alkalinity from 0.73 - 1.35 meq/l. However, from April to September these two parameters ranged from 7.5 - 7.7 and 0.33 - 1.35 meq/l, respectively. Dissolved oxygen (DO) and free CO2 concentration ranged from 2.5 - 6.09 and 0.084 - 0.087 mg/l, respectively. During April to September the Chlorophyll-a value ranged from 5.5 - 7.5 μg/l while the range of SRP was 24.23 - 30.05 μg/l during the same period. At the latter part of the study year i.e., during the dry period (December to March) those two parameters were relatively low in concentration. In April a high concentration of NH4+ (1380 μg/l) was reported from the haor, at other times this parameter ranged from 690 - 820 μg/l. The NO3-N ranged from 0.25 - 0.75 mg/l. High density of phytoplankton population (2690 ind./l) was reported at the time of high concentration of SRP (30.05 μg/l ) of the haor water. The chlorophyll-a value (7.5 μg/l) was also highest at that time. So, it could be said that SRP concentration in Tanguar haor has been playing a vital role in regulating the standing crop of phytoplankton. To find the variation on a spatial scale, the data of the present investigation were compared with another study station of the haor namely, Rauar Station. No significant difference was observed among the concentrations of different parameters. However, a slight increasing trend in the concentrations of DO, alkalinity, SRP, NO3-N, SRS, NH4+ and total phytoplankton density was observed in the Watch Tower Station compared to Rauar Station. Watch Tower Station is also relatively deeper with an improved light climate as it had been revealed by the mean value of the Secchi depth. The water quality of Tanguar Haor has been classified as mesotrophic. Dhaka Univ. J. Biol. Sci. 29(1): 9-18, 2020 (January)

scholarly journals A temporal and spatial investigation of cyanophage abundance in the Gulf of Aqaba, Red Sea

2006 ◽  
Vol 86 (3) ◽  
pp. 507-515 ◽  
Author(s):  
Andrew D. Millard ◽  
Nicholas H. Mann
Keyword(s):  
Host Range ◽  
Water Column ◽  
Red Sea ◽  
Surface Waters ◽  
Annual Cycle ◽  
Water Samples ◽  
Gulf Of Aqaba ◽  
Temporal And Spatial ◽  
Multiple Strains ◽  
Spatial Investigation

The aim of this study was to determine the abundance of cyanophages over an annual cycle in the Red Sea from the period April 1999 to December 1999 at a range of depths. Cyanophage numbers from 71 water samples were determined by the use of plaque assays using four different Synechococcus strains. The results indicate that cyanophage are found throughout the water column from surface waters to depths of 150 m, with a discrete maximum in the number of cyanophages in the summer months of July, August and September at a depth of 30 m. Eighty-seven cyanophages were isolated and characterized in terms of host range, genome size and possession of a myoviral portal vertex gene. Cyanophages were found to infect multiple strains of Synechococcus from different phylogenetic clades. The genome sizes of cyanophages were also found to be bigger than previously estimated.

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