The trophic level impact of structural changes in Aufwuchs communities resulting from low levels of stress can be assessed through analyses of the nutritive value of the microfloral community in conjunction with measurements of grazer consumption rates and assimilation efficiencies. Artificial streams dosed with either intermittent chlorination (20 min doses 3 times per d) or continuous treatments of copper (0.05 ppM) or dextrose (1 or 2 ppM) were used to obtain Aufwuchs communities from stressed environments. Aufwuchs communities were also sampled from the New River within and around a chlorinated-thermal, power plant discharge. The heterotrophically dominated Aufwuchs communities developing under the dextrose enrichment contained more protein, carbohydrate, and calories compared to reference communities. There was no significant change in snail consumption of Aufwuchs from the dextrose enriched streams, although this community was consistently assimilated with greater efficiency relative to reference communities. When Aufwuchs developing under the chlorine or copper treatments became dominated by blue-green algae, the protein content of these communities increased as a result of the algal proteinatious sheath. Carbohydrate content was generally less then reference values for Aufwuchs developing under chlorine or copper stress. Aufwuchs from these treated streams were consumed to a less extent than reference communities and assimilated with 2 to 12% less efficiency
Brust, K; Licht, O; Hultsch, V; Jungmann, D; Nagel, R
The effects of the herbicide terbutryn on a simple lotic food web were investigated during a 72-d exposure period in five artificial indoor streams in a greenhouse. The model compound terbutryn, an s-triazine and an inhibitor of photosynthesis, was applied once in each stream at nominal concentrations of 0.6, 6, 60, or 600 microg/L. Terbutryn concentrations in the water were analyzed by gas chromatography/mass spectrometry, and an overall time to 50% dissipation (DT50) of 28 d was calculated. The development of aufwuchs and the population growth and development of the oligochaete Lumbriculus variegatus were investigated. We determined that terbutryn was toxic to L. variegatus at 23.7 mg/L (96-h median lethal concentration [LC50]) and 16.5 mg/L (96-h median effective concentration [EC50]) in static acute toxicity tests. Terbutryn decreased aufwuchs production at 0.6 microg/L in the experimental streams. Population growth of L. variegatus was decreased by 50% at 6 microg/L. The effect of terbutryn on the aufwuchs was a direct effect of decreases in the periphyton. However, the effects on L. variegatus were an indirect effect of terbutryn as a consequence of decrease in the aufwuchs food source and occurred at three-orders-of-magnitude-lower concentrations of terbutryn than the acute toxicity effects. Our study demonstrates the utility of indoor lotic microcosm studies for evaluating both direct and indirect effects of contaminants on aquatic ecosystems.
Nelson, V.A.; Seymour, A.H.
The Amchitka Radiobiological Program is a continuing program to collect biological and environmental samples for radiometric analyses. Results of analyses for samples collected during 1976 include gamma-emitting radionuclides in air filters, freshwater, birds, lichens, marine algae, marine invertebrates, fish, aufwuchs, and freshwater moss and plants; 90 Sr in rats, birds, and soil; 239 240 Pu in sand, soil, marine algae and fish; and tritium ( 3 H) in seawater, freshwater, and biological organisms
Newbold, J.D.; Elwood, J.W.; O'Neill, R.V.; Sheldon, A.L.
To describe spiralling in Walker Branch, a first-order woodland stream in Tennessee, we released 32 PO 4 to the stream water and measured its uptake from the water and then followed its dynamics in coarse particulate organic matter (CPOM), fine particulate organic matter (FPOM), aufwuchs, grazers, shredders, collectors, net-spinning filter feeders, and predators over a 6-week period. Rates of transfer among compartments and rates of downstream transport were estimated by fitting a partial differential equation model of the ecosystem to the data. With the resulting coefficients, the model was run to steady state to estimate standing stocks and fluxes of exchangeable phosphorus. Phosphorus moved downstream at an average velocity of 10.4 m/d, cycling once every 18.4 d. The average downstream distance associated with one cycle was therefore 190 m (10.4 m/d x 18.4 d). Spiralling length, at steady state, is approximately the ratio of the total downstream flux of phosphorus per unit width of stream (720 mg.d -1 .m -1 ) to the rate of P uptake from the water (3.90 mg.m -2 .d -1 ). CPOM accounted for 60% of the uptake, FPOM for 35%, and aufwuchs for 5%. Turnover times of P in particulates ranged from 5.6 to 6.7 d, except for FPOM, which showed a slower turnover time of 99 d. Of the P uptake from water by particulates, 2.8% was transferred to consumers, while the remainder returned directly to the water. About 30% of the consumer uptake, in turn, was transferred to predators. The small consumer turnover length reflected low consumer uptake of P from particulates and slow downstream drift velocity (0.013 m/d). In spite of the low rate of phosphorus uptake, the combined consumer-and-predator community accounted for 25% of the standing stock of exchangeable P in the stream. The retentiveness of this community is attributable both to the low drift rate and to a long turnover time (152 d) for P within the community
Newbold, J D; Elwood, J W; Schulze, M S; Stark, R W; Barmeier, J C
In order to test for nitrogen limitation and examine ammonium uptake by stream sediments, ammonium hydroxide was added continuously at concentrations averaging 100 /sup +/gl/sup -1/ for 70 days to a second-order reach of Walker Branch, an undisturbed woodland stream in Tennessee. Ammonium uptake during the first 4 h of addition corresponded to adsorption kinetics rather than to first-order uptake or to Michaelis-Menten kinetics. However, the calculated adsorption partition coefficient was two to four orders of magnitude greater than values reported for physical adsorption of ammonium, suggesting that the uptake was largely biotic. Mass balance indicated that the uptake of ammonium from the water could be accounted for by increased nitrogen content in benthic organic detritus. Nitrification, inferred from longitudinal gradients in NO/sub 3/, began soon after enrichment and increased dramatically near the end of the experiment. Both ammonium and nitrate concentrations dropped quickly to near background levels when input ceased, indicating little desorption or nitrification of excess nitrogen stored in the reach. There was no evidence of nitrogen limitation as measured by weight loss, oxygen consumption, phosphorus content, and macroinvertebrate density of red oak leaf packs, or by chlorophyll content and aufwuchs biomass on plexiglass slides. A continuous phosphorus enrichment 1 year earlier had demonstrated phosphorus limitation in Walker Branch. 38 references, 6 figures, 3 tables.
Full Text Available Stomach contents were examined from 102 banded puffer, Colomesus psittacus (Tetraodontidae, caught from intertidal mangrove creeks at diurnal neap tides between June and September, 1997 (early dry season near Bragança (north Brazil. The study found that C. psittacus were specialized predators of Cirripedia (Balanus spp. and Brachyuran crabs (Uca spp., Pachygrapsus gracilis (mean: 58 and 38% by dry weight, respectively, emphasizing a short food chain in the mangrove system. Cirripedia and Brachyura dominated the diet in all size classes, however, the prey spectrum narrowed with fish size. The mean daily consumption of Cirripedia and Brachyura was 6.2% body weight of C. psittacus. On average C. psittacus consumed 100.3 g.ha-1.d-1 of Cirripedia and 178.7 g.ha-1.d-1 of Brachyura (wet weight. The predation on Brachyuran crabs - a significant driver of fluxes of organic matter and energy in the system - provides C. psittacus with an important ecological function in the mangrove food web. A plant-animal interaction is proposed where C. psittacus exerts a mutually beneficial cleaning function on the Aufwuchs (Cirripedia and associated epibiota of Rhizophora mangle stilt roots. Our results and those of other studies suggest that C. psittacus encounter optimum foraging conditions in the mangrove at high inundations at daylight (spring tide-day whereas darkness and low inundations are linked to poor foraging conditions (neap tide-night. The C. psittacus resource could be used as an alternative income in the region in terms of i sustainable catch and filet processing for exports to East Asia, ii developing certified aquaculture methods for breeding puffers for the aquarium trade.
1. The distribution of egg masses of the freshwater snails Lymnaea stagnalis and Planorbarius corneus on the undersides of water lily leaves (e.g. Nuphar lutea) is related to the prevalence of the leaf-mining beetle Galerucella nymphaeae. 2. When given the choice, Planorbarius significantly avoids leaves that were infested by the mining beetle. Conversely, Lymnaea did not discriminate against mined leaves. 3. Intact Nuphar leaves block over 95% of incident ultraviolet radiation. Yet, ultraviolet transmission reaches almost 100% under beetle mining scars. These are several times wider than snail embryos. 4. When exposed to natural sunlight, Lymnaea embryos proved to be resistant to ambient ultraviolet, while Planorbarius embryos were rapidly killed. Thus, one selective advantage of Planorbarius discrimination against mined leaves when depositing its eggs could be the avoidance of ultraviolet radiation passing through mining scars. 5. Other mining-related modifications of the leaves, reduced area, decreased longevity, altered aufwuchs (i.e. biofilm and epibionts) are discussed but seem less relevant for the oviposition preference of Planorbarius. 6. The discriminatory behaviour of this snail species was triggered by water-borne cues emitted by the damaged leaf, not by the eggs or larvae of the beetle. 7. This study illustrates how environmental stress on a given species, ultraviolet radiation in this case, can be ecologically buffered (shading by Nuphar) or enhanced (reduction of Nuphar shading through beetle mining) by associated species. It highlights how the impact of a given stress depends on the identity of the target species as well as on the identity and role of other species in the community.
Persistent organic compounds in food chains in Bavaria and Czechia. Pt. 1. Terrestrial systems; Persistente organische Verbindungen in Nahrungsketten von Bayern und Tschechien. T. 1. Terrestrische Systeme
Kettrup, A; Heinisch, E
In the paper presented here single presentations concerning the contamination of soil, vegetation and organs and tissues form animals and man with persistent organic substances (DDT and metabolites, isomers of hexachlorocyclohexane, hexachlorobenzene, cyclodiene insecticides, chlorophenols, light volatile organic compounds, PCDD/F, PAH and nitromusk compounds) from Bavaria, the Czech Republic and Brandenburg/Berlin and the former GDR, respectively, were assessed, summarized and - as far as possible - compared and confronted. The results are given in the summaries of the single chapters. It could be shown that the different socioeconomic structures in the regions upto 1989 has considerable influences on the extent of the contamination. Large corpusses of law concerning the application and production of chemical products and their increasingly denser monitoring in Bavaria as well as the various sanitation measures has lead to only traces of chloroorganic compounds now and to a minimization of unavoidable substances like PCDD/F. These prerequisites have now been created in the new federal states - here the example Brandenburg - where upto 1989 the national economy was only directed at production maximization and they begin to result in a decrease of contamination especially for the classical chlorohydrocarbons. In the Czech Republic there are still mostly considerably higher loads, e.g. for HCB and especially for PCB, leading to the consideration of possible bordercrossing effects. (orig.) [Deutsch] In der vorliegenden Arbeit wurden Einzeldarstellungen zur Kontamination von Boden, Aufwuchs und von Tieren bzw. dem Menschen stammenden Organen und Geweben mit persistenten organischen Verbindungen (DDT und Metabolite, Isomeren des Hexachlorcyclohexans, Hexachlorbenzol, Cyclodien-Insektizide, Chlorphenole, leichtfluechtige organische Verbindungen, PCDD/F, PAK und Nitromoschusverbindungen) aus Bayern, Tschechien und Brandenburg-Berlin bzw. der ehemaligen DDR ausgewertet
Full Text Available The Kpong Headpond was the second created on the Volta River after Akosombo Dam, primarily as a source of hydroelectric power generation and potable water supply, and additionally, it has supported some fish production in Ghana since impoundment. The changes in fish community of the Kpong Headpond were studied to provide baseline information for strategies formulation to support the socio-economic development of the reservoir. The study identified changes in the fish community of the reservoir by comparing occurrence, composition, relative abundance and relative importance estimates of fish species, families and trophic groups, from available previous studies in the reservoir. From the collated information all fishes identified in the reservoir were categorised based on occurrence and importance as disappeared, appeared, permanent, declined or important, to show current status. The results indicated that the fish community has experienced a shift in the composition and relative abundance of important species, families and trophic groups in terms of number and weight, while remaining ecologically balanced. Representatives of the families Osteoglossidae, Centropomidae and Characidae have declined while representatives of the families Claroteidae, Cyprinidae and Cichlidae have increased. The aufwuch-detritus and herbivores declined while semi-pelagic omnivores increased resulting in a shift in dominance to benthic and semi pelagic omnivores. The appearance of five species and the disappearance of 25 others indicated a dynamic restructuring of the fish community in the reservoir, as expected. Enforcement of fishing regulations including the use of appropriate gear and fishing methods, fishery access control, promotion of culture-based fisheries and improvement in fisher education are recommended topics for sustainable fisheries in the reservoir. Rev. Biol. Trop. 59 (4: 1685-1696. Epub 2011 December 01.La laguna Kpong se convirtió en la segunda