Search results for "benthic"
showing 10 items of 350 documents
Predation of perch on vendace larvae: diet composition in an oligotrophic lake and digestion time of the larvae
2007
The diet of perch Perca fluviatilis was studied to reveal possible predation on vendace Coregonus albula larvae in an oligotrophic lake. Perch diet changed with the size of the fish: small perch ate mainly zooplankton and the diet shifted more to benthic invertebrates and fishes in larger perch. There were also annual and spatial differences in the diet, probably reflecting differences in the availability of prey animals. Perch predation on vendace larvae was only observed in the area with high availability of the larvae. The result suggested strengthened predation when the density of the larvae increases. According to bioenergetics modelling, the perch population increased natural mortalit…
Morphological variation of perchPerca fluviatilisin humic lakes: the effect of predator density, competition and prey abundance
2010
Between and within-lake variations in morphology of perch Perca fluviatilis were studied in four humic lakes in eastern Finland. Perca fluviatilis were more streamlined and smaller headed in a lake with the highest abundance of cyprinids, but lowest abundance of predators (Lake Tuopanjarvi), indicating adaptation to planktivorous feeding and low predator density. Highest bodied fish were found from a lake with the lowest cyprinid but highest predator abundance (Lake Koppelojarvi), which conversely indicates adaptation to more effective predator avoidance. Furthermore, the length of the paired fins was longest in Lake Kinnasjarvi and Lake Tuopanjarvi, where the abundance of benthic macroinve…
Chemosensitizers of the multixenobiotic resistance in amorphous aggregates (marine snow): etiology of mass killing on the benthos in the Northern Adr…
1998
Periodically appearing amorphous aggregates, 'marine snow', are formed in the sea and if settled as mars on the sea bottom cause death of benthic metazoans. Especially those animals are killed which are sessile filter feeders, e.g, sponges, mussels, or Anthozoa. The etiology of the toxic principle(s) is not yet well understood. Gel-like marine snow aggregates occurred in the Northern Adriatic during summer 1997. Samples of these aggregates were collected during the period July to September and the outer as well as the inner zones were analyzed for (i) cell toxicity, and (ii) chemosensitizing activity of the multixenobiotic resistance (MXR)mechanism. Organic extracts were prepared an…
Transcriptomic, biochemical and individual markers in transplanted Daphnia magna to characterize impacts in the field
2015
Daphnia magna individuals were transplanted across 12 sites from three Spanish river basins (Llobregat, Ebro, Jucar) showing different sources of pollution. Gene transcription, feeding and biochemical responses in the field were assessed and compared with those obtained in re-constituted water treatments spiked with organic eluates obtained from water samples collected at the same locations and sampling periods. Up to 166 trace contaminants were detected in water and classified by their mode of action into 45 groups that included metals, pharmaceuticals, pesticides, illicit drugs, and other industrial compounds. Physicochemical water parameters differentiated the three river basins with Llo…
Environmental history of an urban lake: a palaeolimnological study of Lake Jyväsjärvi, Finland
2003
Sedimentary diatom frustules and chironomid remains, in addition to the chemical stratigraphy of 32 elements and organic pollutants such as resin acids, PCB, DDT and its metabolites, were studied from core samples taken from Lake Jyvasjarvi in Central Finland (64° 14′ N, 25° 47′ E). The sediment profile covered over 200 years, with the oldest samples representing a period of very low human interference. The town of Jyvaskyla was established on the lake shore in 1837, and the lake received untreated municipal wastewater from the town up until, 1977. A paper mill started operations in 1872 and began discharging effluent into Lake Jyvasjarvi. In recent years this effluent loading has been redu…
A quantitative survey of the benthic meiofauna in the Gulf Of Riga (eastern Baltic Sea), with special reference to the structure of nematode assembla…
1998
Abstract The Gulf of Riga is relatively shallow and considered to be one of the most eutrophied areas in the Baltic Sea with an annual primary production estimated to 290 gCm-2 yr-1. Meiofauna sampling was carried out at 30 stations homogeneously spread over the Gulf of Riga, varying in depth and sediment structure. The average meiofauna abundance was 4800 ind/10 cm2, with a maximum of 17000 ind/10 cm2. Harpacticoid copepods were abundant all over the Gulf, averaging 425 ind/10 cm2. The highest number was found close to the mouth of the river Daugava, up to 1400 ind/10 cm2. Harpacticoids were significantly more abundant in sediments with medium organic content (loss on ignition (LOI) 5–10%)…
Predicting the stream macroinvertebrate fauna across regional scales: influence of geographical extent on model performance
2008
AbstractPredictive modeling is used increasingly often in freshwater bioassessment. These models are routinely applied across broad geographical areas, yet the influence of spatial extent on model performance has not been assessed directly. We examined the influence of changing geographical extent on the performance of River InVertebrate Prediction and Classification System (RIVPACS)–type predictive models of benthic macroinvertebrates in boreal headwater streams representative of reference conditions. Separate models were constructed for 2 hierarchical extents: within ecoregions (middle boreal and north boreal) and across ecoregions. We assessed the accuracy and precision of the models usi…
Determinants of macroinvertebrate diversity in headwater streams: regional and local influences
2003
Summary 1 Multiscale determinants of diversity and the relationship between regional (RSR) and local richness (LSR) have recently attracted increased attention, yet such studies on stream organisms remain scarce. We studied the relationships among RSR, β-diversity, LSR and local environmental variables in 120 headwater streams in Finland. Approximately similar-sized areas of eight drainage systems were defined as regions, and 15 stream riffles (= locality) per region were sampled. 2 RSR showed a strong positive relationship with mean LSR (R2 = 0·686), and there was no sign of curvilinearity within the observed range of RSR. RSR was also positively, although non-significantly, related to β-d…
Habitat geometry of benthic substrata: effects on arrival and settlement of mobile epifauna
1996
Abstract The effect of substratum complexity on the early stages of colonization by mobile epifauna was assessed through a comparative study based on the architecture of artificial substrata. We conducted field observations over 4 years, on six types of small plastic substrata placed in the low intertidal zone of an exposed rocky shore, for varied immersion periods (1, 2, 4 and 12 wk). The use of artificial substrata allowed us to manipulate independently structural and spatial features of the habitat, such as total area, amount of folds, intercepting area, total volume, and interstitial volume. The invertebrate fauna colonizing over 300 sample units was recorded, and their densities compar…
Succession et remplacements de communautés à brachiopodes en régime de sédimentation discontinue (Jurassique Moyen, Bourgogne, France)
1993
Abstract Sequence stratigraphy throws a new and seminal light on the fossil record and helps in determining the respective role played by external control (community replacement) and internal control (paleoecological succession) in the temporal “train” of marine benthic paleocommunities. Five brachiopod-dominated communities (C1–C5) are recognized and their temporal “train” described, during the uppermost Bathonian-lower Callovian interval in Burgundy. The first series (C1–C3) exhibits a trend interpreted as a paleoecological succession and the next two (C3–C4, C4–C5) as community replacements. Within the scope of sequence stratigraphy, the paleoecological succession comes at the end of a t…