scholarly journals Trophic ecology of juvenile flatfish in a coastal nursery ground: contributions of intertidal primary production and freshwater particulate organic matter

2012 ◽  
Vol 449 ◽  
pp. 221-232 ◽  
Author(s):  
C Kostecki ◽  
JM Roussel ◽  
N Desroy ◽  
G Roussel ◽  
J Lanshere ◽  
...  
Keyword(s):  
Organic Matter ◽  
Primary Production ◽  
Particulate Organic Matter ◽  
Trophic Ecology ◽  
Nursery Ground

scholarly journals Influence of anticyclonic eddies on the Biogeochemistry from the Oligotrophic to the Ultraoligotrophic Mediterranean (BOUM cruise)

2012 ◽  
Vol 9 (10) ◽  
pp. 3827-3855 ◽  
Author(s):  
T. Moutin ◽  
L. Prieur
Keyword(s):  
Organic Matter ◽  
Primary Production ◽  
Particulate Organic Matter ◽  
Strong Mixing ◽  
Strong Impact ◽  
Depth Range ◽  
Oxygen Utilization ◽  
Trophic Conditions ◽  
N Input ◽  
Anticyclonic Eddies

Abstract. We studied a longitudinal transect in the Mediterranean Sea (MS) and along this transect, the influence of anticyclonic eddies at three long duration (LD) stations. The deep chlorophyll maximum depth, the euphotic layer depth and the top of the nitracline depth are clearly correlated outside of the eddies, and deepen from the oligotrophic western to the ultraoligotrophic eastern MS. We provide evidence that the locations of the three LD stations studied were near the axis of the eddies. Their diameters were close to 100 km and the studied areas were less than 10 km from the centre of the eddies. The positions of the LD stations are marked by an increase in the flux function and a decrease in apparent oxygen utilization (AOU) and in excess density σ), as expected for anticyclonic eddies. Integrated mean primary production measured in situ inside the three studied eddies confirms the previous conclusion that integrated primary production (IPP) about 150 mgC m−2 d−1 may appear as a lower limit for IPP during strong oligotrophic conditions. The mesoscale activity is strong enough to locally modify the very well-documented western-to-eastern gradient of trophic conditions in the MS. We proposed a new calculation for mixed layer depths (MLDs) enabling the determination of MLD to take into consideration processes occurring with time scales ranging from a few hours to several days, and also the winter MLD. Studying the main physical, chemical and dynamical characteristics of the three eddies enables us to consider that the vorticity barrier prevents any strong mixing and advection of outer water inside the eddy and explains why the depth range of eddies starts from the surface. As a first approximation, the anticyclonic eddies could be considered as closed systems dating back to the previous winter, making possible to draw first-order budgets. The daily new N-input in the photic zone is virtually identical to the N-export measured at 230 m by drifting traps. This means that the eddies are close to an equilibrium state where input is equal to loss. The annual N-input by winter convection, which is a fundamental criterion for new nutrient availability, may be extremely variable inside eddies, with W-MLD varying from 90.5 m at the western station to 396.5 m at the eastern station. W-MLDs are always deeper inside the eddies than outside where they are in keeping with climatological averages. AOU was low inside the eddies; this together with the near-identical export measured at 230 and 460 m seems to indicate that eddy cores are areas where low mineralisation of particulate organic matter occurs. "In" and "out" AOU comparisons indicate lower mineralisation inside the eddies suggesting a higher efficiency for CO2 sequestration via sedimentation of particulate organic matter. The three eddies are enriched in dissolved organic carbon (DOC). Sequestration of CO2 by vertical export of accumulated DOC therefore seems to be higher inside eddies. The relative importance of DOC transport in the biological pump is probably one of the main characteristics of low-P low chlorophyll (LPLC) areas, and it is likely to be reinforced inside anticyclonic eddies. The numerous anticyclonic eddies in the MS are likely to influence the water masses and their dispersion, and therefore have a strong impact on the biogeochemical properties at the scale of the MS.

Effect of Impoundment and River Diversion on Profundal Macrobenthos of Southern Indian Lake Manitoba

1984 ◽  
Vol 41 (4) ◽  
pp. 638-648 ◽  
Author(s):  
Allen P. Wiens ◽  
David M. Rosenberg
Keyword(s):  
Organic Matter ◽  
Primary Production ◽  
Particulate Organic Matter ◽  
Standing Crop ◽  
Suspended Solids ◽  
Shoreline Erosion ◽  
Benthic Organism ◽  
River Diversion ◽  
Before And After ◽  
High Diversity

Profundal macrobenthos in Southern Indian Lake, Manitoba, were surveyed to determine effects of hydroelectric manipulations in 1972 (preimpoundment), 1977 (postimpoundment), and 1979 (postdiversion). Lakewide average standing crops increased following impoundment and decreased by 3 yr after impoundment. Regional changes in standing crops usually could be related to additions of nutrients leached from flooded vegetation, additions of particulate organic matter resulting from shoreline erosion, and changes in integral primary production and suspended solids concentrations before and after impoundment. Greater increases in standing crops of macrobenthos in shallower compared with deeper depth zones of the lake after flooding were attributed to preferential deposition of organic materials in the shallow areas of the lake. Mean standing crops of macrobenthos were higher in regions through which the Churchill River flowed than in regions isolated from the flow before and after impoundment. After diversion, greatest decreases in standing crops occurred in isolated regions, whereas those of regions in the flow declined much less or increased. Responses of the most abundant taxa of macrobenthos (Pontoporeia brevicornis grp., Chironomidae, Oligochaeta, Sphaeriidae) differed in many ways from those recorded for other new reservoirs. Pontoporeia brevicornis grp. remained the most abundant benthic organism, there was no evident succession of macrobenthic taxa, and a high diversity of profundal species was maintained. These results, together with the slight changes in standing crop observed after flooding, indicated only a marginal impact on macrobenthos caused by the low-level flooding of Southern Indian Lake.

scholarly journals Seasonal dynamics of carbon and nutrients from two contrasting tropical floodplain systems in the Zambezi River basin

2015 ◽  
Vol 12 (24) ◽  
pp. 7535-7547 ◽  
Author(s):  
A. L. Zuijdgeest ◽  
R. Zurbrügg ◽  
N. Blank ◽  
R. Fulcri ◽  
D. B. Senn ◽  
...  
Keyword(s):  
Organic Matter ◽  
Primary Production ◽  
River Basin ◽  
Particulate Organic Matter ◽  
Dry Season ◽  
Nutrient Concentrations ◽  
Wet Season ◽  
Carbon And Nitrogen ◽  
Zambezi River Basin ◽  
Zambezi River

Abstract. Floodplains are important biogeochemical reactors during fluvial transport of carbon and nutrient species towards the oceans. In the tropics and subtropics, pronounced rainfall seasonality results in highly dynamic floodplain biogeochemistry. The massive construction of dams, however, has significantly altered the hydrography and chemical characteristics of many (sub)tropical rivers. In this study, we compare organic-matter and nutrient biogeochemistry of two large, contrasting floodplains in the Zambezi River basin in southern Africa: the Barotse Plains and the Kafue Flats. Both systems are of comparable size but differ in anthropogenic influence: while the Barotse Plains are still in large parts pristine, the Kafue Flats are bordered by two hydropower dams. The two systems exhibit different flooding dynamics, with a larger contribution of floodplain-derived water in the Kafue Flats and a stronger peak flow in the Barotse Plains. Distinct seasonal differences have been observed in carbon and nutrient concentrations, loads, and export and retention behavior in both systems. The simultaneous retention of particulate carbon and nitrogen and the net export of dissolved organic and inorganic carbon and nitrogen suggested that degradation of particulate organic matter was the dominant process influencing the river biogeochemistry during the wet season in the Barotse Plains and during the dry season in the Kafue Flats. Reverse trends during the dry season indicated that primary production was important in the Barotse Plains, whereas the Kafue Flats seemed to have both primary production and respiration occurring during the wet season, potentially occurring spatially separated in the main channel and on the floodplain. Carbon-to-nitrogen ratios of particulate organic matter showed that soil-derived material was dominant year-round in the Barotse Plains, whereas the Kafue Flats transported particulate organic matter that had been produced in the upstream reservoir during the wet season. Stable carbon isotopes suggested that inputs from the inundated floodplain to the particulate organic-matter pool were important during the wet season, whereas permanent vegetation contributed to the material transported during the dry season. This study revealed effects of dam construction on organic-matter and nutrient dynamics on the downstream floodplain that only become visible after longer periods, and it highlights how floodplains act as large biogeochemical reactors that can behave distinctly differently from the entire catchment.

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