scholarly journals Persistent organic pollutants in river food webs: influence of trophic position and degree of heterotrophy

2005 ◽  
Vol 62 (9) ◽  
pp. 2021-2032 ◽  
Author(s):  
Olof Berglund ◽  
Per Nyström ◽  
Per Larsson
Keyword(s):  
Food Webs ◽  
Salmo Trutta ◽  
Trophic Position ◽  
Dry Weight ◽  
Grazing Pressure ◽  
Weight Basis ◽  
Trophic Levels ◽  
Brown Trout Salmo Trutta ◽  
Lipid Weight ◽  
The Mean

We investigated how the degree of autotrophy/heterotrophy and organism trophic position influenced the bioaccumulation of polychlorinated biphenyls (PCBs) in 10 benthic river food webs consisting of terrestrial detritus, periphyton, invertebrates, and age-0 brown trout (Salmo trutta) in southern Sweden. Concentrations of PCBs increased with trophic position, estimated from δ15N and δ13C, on a dry weight basis (ng·g–1 dry weight) but not on a lipid weight basis (ng·g–1 lipid). PCB biomagnification factors between the first and second trophic levels (invertebrates/ periphyton and invertebrates/detritus) ranged between 0.3 and 2.3 and between the second and third levels (trout/invertebrates) between 0.3 and 2.0 on a lipid weight basis. The mean proportion of carbon ultimately derived from terrestrial sources, α, was 0.82 ± 0.19 for invertebrates and 0.67 ± 0.28 for trout. Contrary to our hypothesis, PCB concentrations in trout were positively related to α (r2 = 0.58–0.77, p < 0.05). As α and the periphyton density (g C·m–2) in the rivers was positively related (r2 = 0.88, p < 0.01), we propose that this relationship was due to an increased retention and exposure of PCBs to trout in rivers with low grazing pressure and high periphyton density.

Variation within and between Rivers in Adult Size and Sea Age at Maturity of Anadromous Brown Trout, Salmo trutta

1991 ◽  
Vol 48 (6) ◽  
pp. 1015-1021 ◽  
Author(s):  
Jan Henning L'Abée-Lund
Keyword(s):  
Brown Trout ◽  
Sexual Maturity ◽  
Salmo Trutta ◽  
Adult Size ◽  
Age At Maturity ◽  
Migration Distance ◽  
Spawning Area ◽  
Brown Trout Salmo Trutta ◽  
Males And Females ◽  
The Mean

I compared adult size and sea age at sexual maturity among nine populations of anadromous brown trout, Salmo trutta, in two Norwegian rivers to determine the extent of inter- and intrariverine variations. Variation in the mean length of spawners and in the mean sea age at sexual maturity were mainly dependent on the variations found within rather than between rivers. Mean lengths and mean age at maturity of males increased significantly with increasing altitude of the spawning area and with migration distance in freshwater. In females, positive significant correlations were found with mean lengths and altitude of the spawning area and with mean sea age at maturity and both spawning site altitude and migration distance. Mean lengths and ages of males and females were not significantly correlated with the rate of water discharge in the streams during spawning. The size of gravel substrate for spawning was of minor importance in explaining interpopulation variation in mean female size. The increase noted in mean length and in mean sea age at maturity of both males and females is probably an adaptation to greater energy expenditure to reach the uppermost natal spawning areas.

The Population of a Trout Stream and the Survival of Released Fish

1958 ◽  
Vol 9 (3) ◽  
pp. 319 ◽  
Author(s):  
AG Nicholls
Keyword(s):  
Salmo Trutta ◽  
Age Groups ◽  
River System ◽  
Fish Population ◽  
Curvilinear Relationship ◽  
Growth And Survival ◽  
Younger Age ◽  
Brown Trout Salmo Trutta ◽  
Preceding Season ◽  
The Mean

The fish population of a river system was studied by electro-fishing in 25 places, after which 1000 marked yearling brown trout, Salmo trutta L., were released at each of 10 sites. In a re-examination 8 to 9 months after the release it was estimated that about 10 per cent. of these were surviving; the survival after 18 months was estimated to be below 5 per cent., and the survival to takable size, at about 3 years of age, at 2 per cent. At no site were the younger age groups of the natural population truly represented in either season, but the numbers of older fish in the second season were greater than those of the corresponding year classes in the preceding season, showing that the streams receive recruitment of younger fish from other sources. Some evidence is produced to show that "nursery" streams provide the source of recruitment. The average annual mortality for fish of 2 and 3 years of age is estimated at from 70 to 80 per cent. for the system. It is estimated that there were about 45,000 takable fish in this river system at the beginning of each season. It is shown that the mean lengths of trout decrease with increasing density of population, and that there is a curvilinear relationship between population density and total weight of all fish per acre. The standing crop of trout at different sites ranged from 1 to 182 lb/acre over the two seasons. The condition factor showed a decrease with increasing age of the fish, and the released fish had a lower factor than resident fish of the same age at all sites. In general there was a relationship between the depth of water and the length of the fish, sections over 14 in. deep having greater populations of larger fish. A study of the ability of each section of stream to carry fish, based on the lengths and condition factors of the fish, the number and weight of the population per acre, and the ability of each section to absorb additions to the population, shows that where populations were low, conditions were Iess favourable to the growth and survival of fish.

Admixture analysis and stocking impact assessment in brown trout (Salmo trutta), estimated with incomplete baseline data

2001 ◽  
Vol 58 (9) ◽  
pp. 1853-1860 ◽  
Author(s):  
Michael M Hansen ◽  
Einar E Nielsen ◽  
Dorte Bekkevold ◽  
Karen-Lise D Mensberg
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Population Level ◽  
Genetic Distances ◽  
Scaling Analysis ◽  
Genetic Contribution ◽  
Multidimensional Scaling Analysis ◽  
Genetic Impact ◽  
Brown Trout Salmo Trutta ◽  
The Mean

Studies of genetic interactions between wild and domesticated fish are often hampered by unavailability of samples from wild populations prior to population admixture. We assessed the utility of a new Bayesian method, which can estimate individual admixture coefficients even with data missing from the populations contributing to admixture. We applied the method to analyse the genetic contribution of domesticated brown trout (Salmo trutta) in samples of anadromous trout from two stocked populations with no genetic data available before stocking. Further, we estimated population level admixture proportions by the mean of individual admixture coefficients. This method proved more informative than a multidimensional scaling analysis of individual-based genetic distances and assignment tests. The results showed almost complete absence of stocked, domesticated trout in samples of trout from the rivers. Consequently, stocking had little effect on improving fisheries. In one population, the genetic contribution by domesticated trout was small, whereas in the other population, some genetic impact was suggested. Admixture in this sample of anadromous trout despite absence of stocked domesticated trout could be because of introgression by domesticated trout adopting a resident life history.

Effect of the traditional cooking practice on fumonisin content of maize porridge consumed in the former Transkei region of South Africa

2012 ◽  
Vol 5 (4) ◽  
pp. 405-407 ◽  
Author(s):  
G.S. Shephard ◽  
J.P. Rheeder ◽  
L. van der Westhuizen
Keyword(s):  
South Africa ◽  
Standard Deviation ◽  
Dry Weight ◽  
Weight Basis ◽  
Rural District ◽  
Limited Effect ◽  
The Mean ◽  
Contamination Levels ◽  
Conventional Manner ◽  
Maize Kernels

Fumonisin exposure in the rural district of Centane, former Transkei region of South Africa, has largely been determined from surveys of fumonisin levels in home-grown maize kernels collected from household storage cribs, rather than from the traditional cooked dishes. In this current study, five samples of home-grown maize kernels were ground in the conventional manner of the district, i.e. without separation of any kernel components. The contamination levels of total fumonisins (FB1+FB2+FB3) in the resultant meals ranged from 2.130 to 13.27 mg/kg. In each of two separate villages, five volunteer householders each cooked a portion of one of the maize meals into a traditional porridge. The resultant ten porridges were subsequently analysed for fumonisins by HPLC. The mean decrease in total fumonisin levels, based on a dry weight basis and corrected for recovery, was 11.3% (standard deviation 6.9%), confirming that preparation of traditional porridge has only a limited effect on fumonisin exposure in this population.

Biology and Management of Dogfish Sharks

2009 ◽  
Keyword(s):  
Stable Isotope ◽  
Pacific Ocean ◽  
Food Webs ◽  
Trophic Position ◽  
Nitrogen Isotope ◽  
Isotope Ratios ◽  
Gulf Of Alaska ◽  
The North ◽  
Northeastern Pacific ◽  
The Mean

Abstract.—Spiny dogfish <em>Squalus acanthias </em>biomass has increased in the Gulf of Alaska, yet little is known about the ecological niche that dogfish fill in this ecosystem. Trophic position is an important indicator of the ecological role of an organism. To explore the trophic position of dogfish we analyzed the nitrogen and carbon stable isotope ratios of 60 dogfish from five locations between Washington and the Gulf of Alaska. The mean δ<sup>15</sup>N values for dogfish ranged from 12.0‰ (central Gulf of Alaska) to 13.4‰ (Howe Sound, British Columbia) and the mean δ<sup>13</sup>C values ranged from –21.3‰ (Yakutat Bay, Alaska) to –17.9‰ (Puget Sound, Washington). Sites to the north tended to be significantly depleted in the heavy isotopes of both nitrogen and carbon. The differences in nitrogen isotope ratios among sites were attributed to potential changes in dogfish feeding behavior and trophic position. Differences in carbon isotope ratios suggested that dogfish utilize different food webs along the northeastern Pacific Ocean shelf. Additionally it was hypothesized that feeding differentially in offshore versus inshore food webs or targeting pelagic versus benthic prey species may explain the isotopic variability. These results are preliminary and require additional tests before conclusions can be made about the trophic position of dogfish in this region. Future work will explore stable isotope variability at lower trophic levels to test the hypothesis that entire food webs are isotopically shifted owing to differences in isotopic fractionation at the base of the food web. Also, trophic level differences among dogfish size classes and between sexes will be explored among a greater diversity of locations to better describe the ecological consequences of increased biomass of dogfish in the northeastern Pacific Ocean.

RESPONSE FROM COPPER AND SELENIUM WITH VITAMIN E INJECTIONS TO CATTLE PASTURED ON MINERAL AND ORGANIC GROUNDWATER SOILS

1973 ◽  
Vol 53 (2) ◽  
pp. 237-244 ◽  
Author(s):  
J. E. MILTIMORE ◽  
J. L. MASON ◽  
J. M. McARTHUR ◽  
C. C. STRACHAN ◽  
J. B. CLAPP
Keyword(s):  
Vitamin E ◽  
Crude Protein ◽  
Clay Soil ◽  
Dry Weight ◽  
Weight Basis ◽  
The Mean ◽  
Good Drainage ◽  
Daily Gain ◽  
Mean Concentration ◽  
Inorganic Sulfate

An experiment, using a total of 127 cattle on one ranch over a 2-yr period and 82 cattle at two separate locations on a second ranch in 1 yr, tested injections of copper (Cu) and injections of selenium (Se) with vitamin E, separately and in combination. Injections of 100 mg Cu as copper calcium edetate resulted in an increased overall daily gain of 118 g or 22%. The injections of Se and vitamin E did not significantly increase gain and there was no synergistic effect when the two materials were given together. The crude protein, inorganic sulfate, S, P, Ca, K, Mg, Cu, Mo, Fe, Mn, Zn, and B concentrations were determined on grass from the experimental pastures and from grass growing in fields around one ranch. These latter forages were collected in seven paired locations with one member forage of each set being harvested from an organic groundwater soil and the other from an adjacent clay soil where there was good drainage. Forage growing on well-drained soils had a Cu/Mo ratio of 1.9, which was almost treble the 0.7 ratio found in forage grown on the groundwater soil. Cu levels in hair from cattle on ranch B, given only Cu injections, averaged 13.4 ppm Cu on an oven-dry weight basis, which was 54% higher in Cu than hair from the control cattle. The mean concentration of Se in hair of cattle receiving Se with vitamin E was 60 ppm, which was not significantly different from the control at 58 ppm.

Non-indigenous amphipods and mysids in coastal food webs of eastern Baltic Sea estuaries

2016 ◽  
Vol 97 (3) ◽  
pp. 581-590 ◽  
Author(s):  
Nadezhda A. Berezina ◽  
Arturas Razinkovas-Baziukas ◽  
Alexei V. Tiunov
Keyword(s):  
Baltic Sea ◽  
Food Webs ◽  
Trophic Position ◽  
Isotope Analysis ◽  
River Estuary ◽  
Trophic Levels ◽  
Gut Contents ◽  
Curonian Lagoon ◽  
Gammarus Tigrinus ◽  
Neva Estuary

The study analyses the role of non-indigenous invertebrates in the food webs of two eutrophic brackish estuarine ecosystems of the Baltic Sea: the Neva River estuary and the Curonian Lagoon, with the aim of clarifying several questions such as what trophic levels were occupied by newly established species (mainly amphipods and mysids) and whether they can affect the native benthic invertebrates as a result of their possible carnivorous nature. Stable isotope analysis (δ15N values) and gut contents analysis of field-collected specimens were used to estimate trophic level and trophic links of the newly established malacostracan crustaceans, while their consumption rates when feeding as carnivores were measured experimentally. The δ15N analysis allocated four trophic levels (TL) in the coastal food webs of both studied ecosystems with the lowest δ15N (2–4‰) for detritus and algae and the highest for fish (12–14‰). Through their high abundance, non-indigenous crustaceans (Pontogammarus robustoides, Gmelinoides fasciatus, Obessogammarus crassus, Gammarus tigrinus, Limnomysis benedeni and Paramysis lacustris) have become important members of food chains of the studied ecosystems. Their trophic position varied significantly within species during ontogenesis. This suggests that they turned from being typically detritivores/plantivorous (TL 2–2.4) at juvenile stages to omnivores (2.5–3) or to carnivores (>3) as adults. Assessment of the predation pressure by the adult amphipods on other coexisting invertebrates (in the example of the Neva Estuary) showed a low or medium impact, depending on species of predator and productivity of its potential prey organisms.

Assessing food-web structure, matter fluxes, and system attributes of a Central European mountain stream by performing mass-balanced network analysis

2004 ◽  
Vol 61 (9) ◽  
pp. 1565-1581 ◽  
Author(s):  
Elisabeth I Meyer ◽  
Rainer Poepperl
Keyword(s):  
Food Web ◽  
Salmo Trutta ◽  
Dry Mass ◽  
Trophic Levels ◽  
Mountain Stream ◽  
Food Web Structure ◽  
Total Consumption ◽  
Cottus Gobio ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Brown Trout Salmo Trutta

Trophic interactions and cycling of matter within the community in a soft-water mountain stream were analyzed on the basis of a compartment food-web model. The model describes (i) the structure of the food web, quantifying biomass, production, and consumption of individual elements as well as of the entire system, and (ii) the flow of matter between compartments as well as trophic levels. Detritus and primary producers sustain a broad variety of invertebrate consumers. Fishes are the top predators; sculpin (Cottus gobio) and a compartment consisting of brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) are at the highest trophic level. Heterotrophic microorganisms (227.1 g dry mass (DW)·m–2·year–1) and aufwuchs algae (150.1 g DW·m–2·year–1) have the highest production. Secondary production of fishes and macroinvertebrates amounts to 2.56 and 19.9 g DW·m–2·year–1, respectively. Total consumption amounts to 1136.41 g DW·m–2·year–1. Main flows occur between the lower trophic levels. Food intake is greatest for microorganisms and Ephemeroptera. A relatively high fraction of invertebrate production is consumed by predators. For 10 of 19 compartments, over 95% of production is used as food by other organisms. Transfer efficiencies are generally low (<10%). A large proportion of matter transfer occurs at the lower discrete trophic levels of the stream.

scholarly journals Protistan grazing impacts microbial communities and carbon cycling at deep-sea hydrothermal vents

2021 ◽  
Vol 118 (29) ◽  
pp. e2102674118
Author(s):  
Sarah K. Hu ◽  
Erica L. Herrera ◽  
Amy R. Smith ◽  
Maria G. Pachiadaki ◽  
Virginia P. Edgcomb ◽  
...  
Keyword(s):  
Food Webs ◽  
Carbon Cycling ◽  
Deep Sea ◽  
Hydrothermal Vent ◽  
Hydrothermal Vents ◽  
Grazing Pressure ◽  
Trophic Levels ◽  
Deep Seawater ◽  
Potential Predator ◽  
Protistan Grazing

Microbial eukaryotes (or protists) in marine ecosystems are a link between primary producers and all higher trophic levels, and the rate at which heterotrophic protistan grazers consume microbial prey is a key mechanism for carbon transport and recycling in microbial food webs. At deep-sea hydrothermal vents, chemosynthetic bacteria and archaea form the base of a food web that functions in the absence of sunlight, but the role of protistan grazers in these highly productive ecosystems is largely unexplored. Here, we pair grazing experiments with a molecular survey to quantify protistan grazing and to characterize the composition of vent-associated protists in low-temperature diffuse venting fluids from Gorda Ridge in the northeast Pacific Ocean. Results reveal protists exert higher predation pressure at vents compared to the surrounding deep seawater environment and may account for consuming 28 to 62% of the daily stock of prokaryotic biomass within discharging hydrothermal vent fluids. The vent-associated protistan community was more species rich relative to the background deep sea, and patterns in the distribution and co-occurrence of vent microbes provide additional insights into potential predator–prey interactions. Ciliates, followed by dinoflagellates, Syndiniales, rhizaria, and stramenopiles, dominated the vent protistan community and included bacterivorous species, species known to host symbionts, and parasites. Our findings provide an estimate of protistan grazing pressure within hydrothermal vent food webs, highlighting the important role that diverse protistan communities play in deep-sea carbon cycling.

Upstream Transport of Mirex by Migrating Salmonids

1989 ◽  
Vol 46 (9) ◽  
pp. 1484-1488 ◽  
Author(s):  
Ronald J. Scrudato ◽  
William H. McDowell
Keyword(s):  
Brown Trout ◽  
Salmo Trutta ◽  
Significant Contribution ◽  
Drainage Basin ◽  
Lake Ontario ◽  
Point Sources ◽  
Trophic Levels ◽  
Salmon River ◽  
Brown Trout Salmo Trutta ◽  
River Drainage Basin

Mirex is a persistent chlorinated hydrocarbon found in appreciable concentrations in sediments and pelagic organisms of Lake Ontario. Concentrations are particularly high in introduced salmonids, which spawn in considerable numbers in tributaries of the Lake. We sampled the sediments and biota of several tributary streams in the Salmon River drainage basin. Greater concentrations of mirex were found in the resident brown trout (Salmo trutta) of tributaries accessible to migrating salmonids than in a nearby reference tributary inaccessible to migration. No significant differences in mirex concentrations were found in lower trophic levels (crayfish and stoneflies) or sediments, although mirex was detected in all samples. Because point sources of mirex are distant from these tributaries we conclude that migrating salmonids make a significant contribution to the upstream transport of mirex from Lake Ontario. Ingestion of salmonid eggs by brown trout, decomposition of salmonid carcasses by blowfly larvae, and ingestion of carcasses by aquatic and terrestrial scavengers are all means by which the contaminant is introduced to upstream environments.

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