Seasonal variations of water column nutrients in the inner area of Ariake Bay, Japan: the role of muddy sediments

2013 ◽  
Vol 185 (8) ◽  
pp. 6831-6846 ◽  
Author(s):  
Masumi Koriyama ◽  
Yuichi Hayami ◽  
Akane Koga ◽  
Koichi Yamamoto ◽  
Alim Isnasetyo ◽  
...  
Keyword(s):  
Water Column ◽  
Seasonal Variations ◽  
Ariake Bay ◽  
Muddy Sediments

Effects of Fe addition on sediment P dynamics in a eutrophic lake

2021 ◽  
Author(s):  
Melanie Münch ◽  
Rianne van Kaam ◽  
Karel As ◽  
Stefan Peiffer ◽  
Gerard ter Heerdt ◽  
...  
Keyword(s):  
Water Quality ◽  
Organic Matter ◽  
Surface Water ◽  
Water Column ◽  
Sediment Cores ◽  
Surface Water Quality ◽  
Water Interface ◽  
Eutrophic Lakes ◽  
Fe Addition

<p>The decline of surface water quality due to excess phosphorus (P) input is a global problem of increasing urgency. Finding sustainable measures to restore the surface water quality of eutrophic lakes with respect to P, other than by decreasing P inputs, remains a challenge. The addition of iron (Fe) salts has been shown to be effective in removing dissolved phosphate from the water column of eutrophic lakes. However, the resulting changes in biogeochemical processes in sediments as well as the long-term effects of Fe additions on P dynamics in both sediments and the water column are not well understood.</p><p>In this study, we assess the impact of past Fe additions on the sediment P biogeochemistry of Lake Terra Nova, a well-mixed shallow peat lake in the Netherlands. The Fe-treatment in 2010 efficiently reduced P release from the sediments to the surface waters for 6 years. Since then, the internal sediment P source in the lake has been increasing again with a growing trend over the years.</p><p>In 2020, we sampled sediments at three locations in Terra Nova, of which one received two times more Fe during treatment than the other two. Sediment cores from all sites were sectioned under oxygen-free conditions. Both the porewaters and sediments were analysed for their chemical composition, with sequential extractions providing insight into the sediment forms of P and Fe. Additional sediment cores were incubated under oxic and anoxic conditions and the respective fluxes of P and Fe across the sediment water interface were measured.</p><p>The results suggest that Fe and P dynamics in the lake sediments are strongly coupled. We also find that the P dynamics are sensitive to the amount of Fe supplied, even though enhanced burial of P in the sediment was not detected. The results of the sequential extraction procedure for P, which distinguishes P associated with humic acids and Fe oxides, as well as reduced flux of Fe(II) across the sediment water interface in the anoxic incubations, suggest a major role of organic matter in the interaction of Fe and P in these sediments.</p><p>Further research will include investigations of the role of organic matter and sulphur in determining the success of Fe-treatment in sequestering P in lake sediments. Based on these data in combination with reactive transport modelling we aim to constrain conditions for successful lake restoration through Fe addition.</p>

Behaviour in flow: perspectives on the distribution and dispersion of meroplanktonic larvae in the water column

2001 ◽  
Vol 58 (1) ◽  
pp. 86-98 ◽  
Author(s):  
Anna Metaxas
Keyword(s):  
Water Column ◽  
Turbulent Flows ◽  
Larval Dispersal ◽  
Spatial Scales ◽  
Fluid Motion ◽  
Benthic Boundary Layer ◽  
Larval Distribution ◽  
Physical Measurements ◽  
Marine Benthic Invertebrates

For marine benthic invertebrates with meroplanktonic larvae, the relative importance of hydrodynamics and swimming behaviour in determining larval dispersal in the water column, particularly at small spatial scales, has not been determined. In the field, larval aggregations recorded at physical and biological discontinuities in the water column were attributed to hydrodynamics. Similar aggregations obtained in the absence of flow in the laboratory indicate a potentially significant role of behaviour. At large spatial scales, larval distribution in the plankton is mainly regulated by horizontal advection. However, the ability of larvae to behaviourally regulate their position at scales of micrometres to metres when exposed to turbulent fluid motion in the water column, as evidenced in the benthic boundary layer, is unknown. Evaluation of swimming in turbulent flows in the water column is an intriguing area of research, which involves several constraints. In the field, quantification of behaviour is limited by low success in tracking larvae and lack of appropriate observational tools. In the laboratory, the generation and quantification of flow regimes that are representative of those in the field remains a challenge. An approach that integrates biological and physical measurements within realistic ranges is necessary to advance our understanding of larval dispersal.

Protozoa abundance, growth, and bacterivory in the water column, on sedimenting particles, and in the sediment of Halifax Harbor

1990 ◽  
Vol 36 (12) ◽  
pp. 859-863 ◽  
Author(s):  
James A. Novitsky
Keyword(s):  
Bacterial Community ◽  
Water Column ◽  
Sediment Surface ◽  
Metabolic Inhibitor ◽  
Optimum Conditions ◽  
Bacterial Populations ◽  
Protozoan Grazing ◽  
Large Numbers ◽  
Doubling Times

The role of protozoan grazing in controlling bacterial populations was examined in four microbial habitats in Halifax Harbor, Canada: the water column, setting particles, the sediment–water interface, and the sediment. Large numbers of protozoans were found in all habitats although most (>56%) were small (<5 μm) flagellates. Protozoans larger than 10 μm were rarely observed; protozoans >20 μm were never observed. Protozoans were also observed to a depth of 9 cm below the sediment surface although efforts to culture viable protozoa failed except for the top 1 cm. The use of the metabolic inhibitor cycloheximide with and without colchicine to selectively inhibit eucaryotic metabolism was shown to severely affect procaryotic metabolism in sediment (and presumably particle and water) samples. Using fluorescently labelled bacteria as food, and under optimum conditions, up to 42% of the Protozoa population exhibited active grazing within 7 h. Using protozoan and bacterial community sizes and doubling times, it was calculated that each protozoan in Halifax Harbor would have to consume 13–118 bacteria per hour for the enumerated nanoplanktonic (<20 μm) Protozoa to be the sole control of the size of the bacterial community. Key words: marine, Protozoa, bacterivory, particles, bacteria.

scholarly journals The Legacy of the Idrija Mine Twenty-Five Years after Closing: Is Mercury in the Water Column of the Gulf of Trieste Still an Environmental Issue?

2021 ◽  
Vol 18 (19) ◽  
pp. 10192
Author(s):  
Elena Pavoni ◽  
Elisa Petranich ◽  
Sergio Signore ◽  
Giorgio Fontolan ◽  
Stefano Covelli
Keyword(s):  
Water Column ◽  
Environmental Concern ◽  
Anthropogenic Factors ◽  
Northern Adriatic Sea ◽  
Northern Adriatic ◽  
High Discharge ◽  
Fine Sediments ◽  
Gulf Of Trieste ◽  
Freshwater Inputs

Mercury (Hg) contamination in the Gulf of Trieste (northern Adriatic Sea) due to mining activity in Idrija (Slovenia) still represents an issue of environmental concern. The Isonzo/Soča River’s freshwater inputs have been identified as the main source of Hg into the Gulf, especially following periods of medium-high discharge. This research aims to evaluate the occurrence and distribution of dissolved (DHg) and particulate (PHg) Hg along the water column in the northernmost sector of the Gulf, a shallow and sheltered embayment suitable for the accumulation of fine sediments. Sediment and water samples were collected under unperturbed and perturbed environmental conditions induced by natural and anthropogenic factors. Mercury in the sediments (0.77–6.39 µg g−1) and its relationship to grain size were found to be consistent with previous research focused on the entire Gulf, testifying to the common origin of the sediment. Results showed a notable variability of DHg (<LOD–149 ng L−1) and PHg (0.39–12.5 ng L−1) depending on the interaction between riverine and marine hydrological conditions. Mercury was found to be mainly partitioned in the suspended particles, especially following periods of high discharge, thus confirming the crucial role of the river inputs in regulating PHg distribution in the Gulf.

Diurnal and seasonal variations in surface methane at a tropical coastal station: Role of mesoscale meteorology

2018 ◽  
Vol 631-632 ◽  
pp. 1472-1485 ◽  
Author(s):  
M. Kavitha ◽  
Prabha R. Nair ◽  
I.A. Girach ◽  
S. Aneesh ◽  
S. Sijikumar ◽  
...  
Keyword(s):  
Seasonal Variations ◽  
Mesoscale Meteorology ◽  
Coastal Station

scholarly journals Seasonal variations in the oxidative stress and inflammatory potential of PM2.5 in Tehran using an alveolar macrophage model; The role of chemical composition and sources

2019 ◽  
Vol 123 ◽  
pp. 417-427 ◽  
Author(s):  
Ahlam H. Al Hanai ◽  
Dagmara S. Antkiewicz ◽  
Jocelyn D.C. Hemming ◽  
Martin M. Shafer ◽  
Alexandra M. Lai ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Chemical Composition ◽  
Alveolar Macrophage ◽  
Seasonal Variations

ROLE OF THE THYROID GLAND IN REGULATION OF METABOLIC RATE IN AN AIR-BREATHING SILUROID FISH, HETEROPNEUSTES FOSSILIS (BLOCH)

1976 ◽  
Vol 69 (3) ◽  
pp. 421-425 ◽  
Author(s):  
B. N. PANDEY ◽  
J. S. D. MUNSHI
Keyword(s):  
Oxygen Consumption ◽  
Thyroid Gland ◽  
Metabolic Rate ◽  
Seasonal Variations ◽  
Heteropneustes Fossilis ◽  
Cyclic Activity ◽  
Experimental Conditions ◽  
Probable Role ◽  
Made In

SUMMARY Studies on cyclic activity of the thyroid and seasonal variations in oxygen consumption (V̇o2) under experimental conditions in which surfacing was either allowed or prevented were made in H. fossilis to try to establish a relationship between these measures and to ascertain the possible role of the thyroid in the regulation of metabolic rate. A good correlation was found between the activity of the thyroid and V̇o2 in this species. This finding was further confirmed by the administration of l-thyroxine or thiouracil to this fish. The thyroxine-and thiouracil-treated animals showed significantly higher (P < 0·05) and lower (P < 0·01) rates of V̇o2 respectively, thus indicating the probable role of the thyroid in the regulation of metabolic rate.

Planktonic and Benthic Bacteriovorous Protozoa at Eleven Stations in Puget Sound and Adjacent Pacific Ocean

1969 ◽  
Vol 26 (2) ◽  
pp. 299-304 ◽  
Author(s):  
Bruce Lighthart
Keyword(s):  
Pacific Ocean ◽  
Water Column ◽  
Deep Sea ◽  
Heterotrophic Bacteria ◽  
Puget Sound ◽  
Ecological Role ◽  
Population Densities ◽  
Sediment Samples

Bacteriovorous Protozoa and heterotrophic bacteria quantitatively cultured from 31 samples collected at eight stations in Puget Sound and three in the adjacent Pacific Ocean (one station being 1520 m deep) ranges from undetectable to approximately 1000 Protozoa per ml and 5–80,000 bacteria/ml. Flagellates in the genera Bodo, Oikomonas, Monas, Rynchomonas, and Actinomonas were the most prevalent forms cultured. One ciliate and several sarcodinoids were also grown. The regression of predatory Protozoa on prey bacteria in sediment samples was calculated to be 580 bacteria for every bacteriovorous protozoan. Population densities of both bacteriovorous Protozoa and heterotrophic bacteria in the samples decreased from sediment to the water column, and from shore seaward. The ecological role of bacteriovorous Protozoa in the shallow and deep sea is discussed.

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