The feeding ecology of Axiothella rubrocincta (Johnson) (Polychaeta: Maldanidae)

The feeding ecology of Axiothella rubrocincta (Johnson) from Tomales Bay, California, is described. This worm inhabits a U-shaped tube of agglutinated sand grains and mucus. Morphological adaptations such as nuchal and anal plaques prevent the tube from becoming clogged. Foreign debris entering the tube is either consumed or incorporated into the tube wall. The proboscis and notosetae are probably used to clean the tube wall. A. rubrocincta combines feeding and burrowing activities to form the funnel and complete the tube: it does not ingest sediment while burrowing. Organic matter deposited into the funnel is buried there by sand slides originating at the rim of the funnel. The concentration of organic matter within the funnel is significantly higher than for non-funnel sediments. A. rubrocincta consumes food from the upper 2 cm of the substratum and is 4.6% efficient as a depositfeeder. It also feeds within the funnel and can ingest large quantities of food. This feeding process is described. A. rubrocincta irrigates its tube at a rate of 5.1 ml sea water/g/h while feeding, and briefly reverses this current to a rate of 0.1 ml/g/h when defaecating. The rhythmic activity patterns are integrated: the mean defaecation and inverse pumping time is 14.4 min at 15 ± 1 C.     

Behavior,Growth, and Reproduction of Lumbriculus Variegatus (Oligochaetae) in Different Sediment Types

Lumbriculus variegatus is an oligochaete widely used in sediment toxicity tests. The locomotory behavior of adults from a normal and a clone population was studied in the Multispecies Freshwater Biomonitor? along with growth and reproduction to determine how different sediment types may affect this worm and forced clones during testing. Four different sand size classes were established by sieving: fine (< 1 mm), medium (1 < × < 2 mm), coarse (> 2 mm), and whole sediment. Locomotory activity was highest in fine and then in coarse sediment, while in whole and medium sediment size classes worms grew and reproduced less, and had lower locomotory activity levels. Fine sediment (< 1 mm) should be used as the negative control in L. variegatus whole sediment toxicity tests. A clone population, generated by cutting all worms over six generations, showed lower locomotory activity levels than normal worms. Artificial cloning is not recommended for obtaining additional test organisms.     

Feeding behavior of the cirratulid Cirriformia filigera (Delle Chiaje, 1825) (Annelida: Polychaeta).

Observations of the feeding behavior of Cirriformia filigera (Delle Chiaje, 1825) (Annelida: Polychaeta) from the intertidal zone of S?o Francisco and Engenho D'água beaches (S?o Sebasti?o, State of S?o Paulo) were made in the laboratory. This species, like other cirratulids, is a deposit feeder, feeding mainly on sediment surface with the aid of its grooved and ciliated palps, which are used to capture food particles. The worm lies just beneath the substrate surface in a J-shaped tube. When feeding, it extends up to 4 palps over the sediment surface, capturing food particles which pass down the groove of each palp directly to the mouth. Only fine sand grains are ingested. The worm frequently extends 4 branchial filaments into the overlying water for aeration. When it moves with the prostomium sideways, it collects and transports sand grains that pass backwards along its ventral region until reaching the middle part of its body. Next, the parapodia and palps move the sand grains to the dorsal posterior end of the animal, covering this area with sand. Some sand grains are also ingested as the worm moves.     

Increase in Alphaproteobacteria in association with a polychaete,Capitella sp. I,in the organically enriched sediment

We conducted bioremediation experiments on the organically enriched sediment on the sea floor just below a fish farm, introducing artificially mass-cultured colonies of deposit-feeding polychaete, Capitella sp. I. To clarify the association between the Capitella and bacteria on the efficient decomposition of the organic matter in the sediment in the experiments, we tried to identify the bacteria that increased in the microbial community in the sediment with dense patches of the Capitella. The relationship between TOC and quinone content of the sediment as an indicator of the bacterial abundance was not clear, while a significant positive correlation was found between Capitella biomass and quinone content of the sediment. In particular, ubiquinone-10, which is present in members of the class Alphaproteobacteria, increased in the sediment with dense patches of the Capitella. We performed denaturing gradient gel electrophoresis (DGGE) analyses to identify the alphaproteobacterial species in the sediment with dense patches of the worm, using two DGGE fragments obtained from the sediment samples and one fragment from the worm body. The sequences of these DGGE fragments were closely related to the specific members of the Roseobacter clade. In the associated system with the Capitella and the bacteria in the organically enriched sediment, the decomposition of the organic matter may proceed rapidly. It is very likely that the Capitella works as a promoter of bacteria in the organically enriched sediment, and feeds the increased bacteria as one of the main foods, while the bacteria decompose the organic matter in the sediment with the assistance of the Capitella.     

Effect of the inclusion of food waste in pig diets on growth performance, carcass and meat quality

Food waste from fish and fruit shops was used as an alternative to the grain in grower-finisher pig diets. Two diets were formulated on an iso-nutrient basis (14 MJ digestible energy per kg, 160 g crude protein per kg on a dry-matter basis) to contain 0 g of food waste per kg in the control diet and 50 g of fish-shop waste per kg and 120 g of fruit-shop waste per kg in the experimental diet. In the study, 28 pigs per diet (seven pigs per pen) were fed ad libitum from 20 kg to 100 kg, then, they were slaughtered and the carcass characteristics determined. The inclusion of food waste in the diet had no significant effect (P>0.05) on average daily feed intake (2.12 v. 2.20 kg/day), average daily gain (0.74 v. 0.78 kg/day), or gain/feed (0.35 v. 0.35 kg per kg). In the case of the experimental diet, backfat thickness was significantly lower (18.0 v. 21.3 mm, P < 0.01). The results of the taste test indicated that the meat from food waste-fed pigs had acceptable organoleptic quality although a very light aroma to fish was observed in the bacon (P < 0.01).It was concluded that food waste from the fish and fruit shops could be included in grower-finisher pig diets without any detrimental effect on growth performance and only minor effects on carcass characteristics and meat quality.     

Discolored Red Seaweed <Emphasis Type="Italic">Pyropia yezoensis</Emphasis> with Low Commercial Value Is a Novel Resource for Production of Agar Polysaccharides

The red seaweed Pyropia yezoensis has been demonstrated to be a novel resource for the production of high-quality agar. P. yezoensis is grown for the food industry in large-scale Japanese mariculture operations. However, discolored P. yezoensis is mostly discarded as an industrial waste, although it has some kind of utility values. Here, we evaluated the utility of discolored P. yezoensis as a resource for agar production. The quality of agar from the discolored seaweed was comparable to that from normal seaweed. In addition, as a distinguishing characteristic, agar yield was higher from discolored seaweeds than from normal types. Moreover, we successfully used agar from discolored P. yezoensis for bacterial plate media and DNA electrophoresis gels without agarose purification. Thus, our results demonstrate that discolored P. yezoensis is suitable for agar production and use in life science research. Diverting discolored P. yezoensis from disposal to agar production provides a solution to the current industrial waste problem in mariculture, as well as a secure source of agar for research purposes.     

The Good,the Bad and the Plenty: Interactive Effects of Food Quality and Quantity on the Growth of Different Daphnia Species

Effects of food quality and quantity on consumers are neither independent nor interchangeable. Although consumer growth and reproduction show strong variation in relation to both food quality and quantity, the effects of food quality or food quantity have usually been studied in isolation. In two experiments, we studied the growth and reproduction in three filter-feeding freshwater zooplankton species, i.e. Daphnia galeata x hyalina, D. pulicaria and D. magna, on their algal food (Scenedesmus obliquus), varying in carbon to phosphorus (C∶P) ratios and quantities (concentrations). In the first experiment, we found a strong positive effect of the phosphorus content of food on growth of Daphnia, both in their early and late juvenile development. Variation in the relationship between the P-content of animals and their growth rate reflected interspecific differences in nutrient requirements. Although growth rates typically decreased as development neared maturation, this did not affect these species-specific couplings between growth rate and Daphnia P-content. In the second experiment, we examined the effects of food quality on Daphnia growth at different levels of food quantity. With the same decrease in P-content of food, species with higher estimated P-content at zero growth showed a larger increase in threshold food concentrations (i.e. food concentration sufficient to meet metabolic requirements but not growth). These results suggest that physiological processes such as maintenance and growth may in combination explain effects of food quality and quantity on consumers. Our study shows that differences in response to variation in food quality and quantity exist between species. As a consequence, species-specific effects of food quality on consumer growth will also determine how species deal with varying food levels, which has implications for resource-consumer interactions.     

Production of earthworm Allolobophora parva (Eisen) in cattle dung

Vermicomposting potential of Allolobophora parva is well proven in recent experiments but little is known about its growth and reproduction performance. Efforts were made in this study to assess the biological productivity of A. parva in cattle waste solids under laboratory conditions. The growth and reproduction performance of A. parva was monitored up to its termination state in experimental beddings. A. parva was weighed weekly and cocoons produced during the interval were also counted. The maximum individual biomass and maximum growth rate (wt. mg worm⁻¹ week⁻¹) was 190.9 ± 0.07 mg (after 13 weeks) and 2.66 (after 12th week), respectively. A. parva showed the maximum values of cocoon number (within a week) and reproduction rate: 26 ± 1.12 and 0.74 ± 0.05 cocoon worm⁻¹ week⁻¹, respectively, during the 8th week of vermiculture. Cocoon production in earthworms was terminated after the 17th week of culture. Data suggested that A. parva may acts as a potential candidate to convert negligible organic waste resources into worm biomass for sustainable environmental management.     

Aquatic worms eating waste sludge in a continuous system

Aquatic worms are a biological approach to decrease the amount of biological waste sludge produced at waste water treatment plants. A new reactor concept was recently introduced in which the aquatic oligochaete Lumbriculus variegatus is immobilised in a carrier material. The current paper describes the experiments that were performed to test whether this concept could also be applied in continuous operation, for which worm growth is an important condition. This was tested for two mesh sizes of the carrier material. With an increase in mesh size from 300 to 350 μm, worm biomass growth was possible in the reactor at a rate of 0.013 d⁻¹ and with a yield of 0.13 g dw/g VSS digested by the worms. Mass balances over the worm reactors showed the importance of correcting for natural sludge breakdown, as the contribution of the worms to total VSS reduction was 41–71%.     

Influence of Chironomidae (Diptera) faecal pellet accumulation on lake sediment quality and larval abundance of pestiferous midge Glyptotendipes paripes

Two opposite distribution patterns of larval Glyptotendipes paripes in relation to organic carbon content in sediments of central Florida lakes were discovered. In a majority of examined lakes, G. paripes larvae were most abundant in sand sediment and their density rapidly declined with increased carbon content (type 1 lakes); however, in some cases the opposite was true (type 2 lakes). To elucidate this anomaly, field-collected organic sediments from types 1 and 2 lakes and sand sediment were studied for G. paripes development in the laboratory. Type 1 organic sediment consisted predominantly of fine particles (<0.25 mm diameter) with low dissolved oxygen levels, whereas type 2 organic sediments consisted primarily of chironomid large faecal pellet aggregates (>0.25 mm diameter), with significantly higher levels of dissolved oxygen concentrations that were similar to sand sediment. Type 2 organic sediment and sand sediment were conducive to higher survival of G. paripes larvae than fine organic sediment. The larvae in type 2 organic sediment produced longer tubes than in other sediment types. This observation indicates that accumulation of chironomid faecal pellets in lake sediments may change physical properties, such as dissolved oxygen level and consequently alter conditions for survival of chironomid larvae and possibly other benthic fauna.     

Vermicomposting potential of Perionyx sansibaricus (Perrier) in different waste materials

The decomposition efficiency of Perionyx sansibaricus (Perrier) for vermicomposting was evaluated by using a variety of wastes such as agriculture waste, farm yard manure and urban solid waste. Vermicomposting resulted in significant increase in total N (80.8-142.3%), phosphorous (33.1-114.6%) and potassium (26.3-125.2%), whereas decrease in organic C (14.0-37.0%) as well as C:N ratio (52.4-69.8%) in different experimental beddings. P. sansibaricus showed maximum biomass production, growth rate (mg day(-1)), mean cocoon numbers, and reproduction rate (cocoon worm(-1)) in VLL (vegetable waste+leaf litter) as compared to other substrate materials. There was a consistent trend for earthworms' growth and reproduction rate, related to initial N-content of the substrate (P<0.05), but there was no clear effect of C:N ratio of the composted material on earthworm cocoon numbers and weight gain. Earthworm showed minimum total population mortality in VLL and maximum in HHCD (household waste+cow dung), after 150 days of experimentation. The increased level of plant metabolites in end product (vermicompost) and growth patterns of P. sansibaricus in different organic waste resources demonstrated the candidature of this species for wastes recycle operations at low-input basis.     

Feeding, growth, and fecundity of Abarenicola pacifica in relation to sediment organic concentration

For marine deposit-feeding invertebrates, the distribution of species with different life history strategies has long been known to be correlated with sediment organic concentration. Large populations of opportunistic species are found in sediments with enriched organic concentration, while equilibrium species populate low organic concentration sediments. Differences in both behavioral (e.g. feeding rate) and physiological (e.g. growth rate, reproductive output) adaptations determine the ability of species to establish populations in different environments. By systematically documenting differences in the way these factors vary as sediment organic concentration varies for both opportunistic and equilibrium species, we can better understand the mechanisms underlying this correlation between sediment organic concentration and species distributions. Here, we present the results of experiments examining the interactions among food concentration, feeding rate, growth rate, and reproductive output (measured as egg number and size) for the equilibrium species Abarenicola pacifica. A. pacifica is a large, long-lived, iteroparous, sub-surface deposit-feeding polychaete. Individual worms were reared throughout most of one generation in sediments differing only in the concentration of organic matter. Juveniles (<20 mg AFDW) had higher feeding rates and growth rates in sediments of higher organic concentration throughout the range tested. These results are consistent with the predictions from optimal foraging theory. As worms grew, however, these patterns changed. Once worms reached a mean body size of approximately 50 mg AFDW, feeding rate was greater on sediments of lower organic concentration (although it took worms in the sediments with lower organic concentration longer to reach this size). Differences in growth rates among treatments decreased as worms grew. For worms >100 mg AFDW, growth rates were uniformly low ( approximately 1%/day) on all sediments, but the early advantage obtained by worms in the high organic treatments resulted in much greater body sizes after 200 days. Worms had higher tissue triacylglyceride concentrations and produced more eggs (independent of worm size) as sediment organic concentration increased. We conclude that A. pacifica alters its feeding rate in response to variations in food resources in such a way as to maximize its energy intake and thereby maximize fitness. Future studies should investigate whether opportunistic species (as well as other equilibrium species) also have this ability.     

A simple screening procedure for selecting fungi with potential for use in the bioremediation of contaminated land

A simple initial screening procedure for selecting strains of white-rot fungi with potential for use in bioremediation of contaminated sites is described. Besides the ability to degrade low molecular weight PAHs, isolates were screened for their growth rate on straw-based agar media, their potential to tolerate high concentrations of phenanthrene and their ability to out-grow the cellulolytic fungus Trichoderma harzianum on straw agar plates. Results from simple in vitro tests were correlated with the ability of the different strains to degrade PAHs in sand microcosms. It was found that fungal growth rate on straw-based agar media in the presence of phenanthrene correlated well with the ability of the different fungi to degrade PAHs in sand microcosms. Whereas growth rate on straw-based agar plates per se was indicative of the ability of white-rot fungi to establish in the presence of a competing fungus, it was a poor indicator of the fungus’ ability to degrade PAHs.     

Alleviation of Both Water and Nutrient Limitations is Necessary to Accelerate Ecological Restoration of Waste Rock Tips

Hard rock quarries are commonly located close to national parks and special areas of conservation and are generally regarded as visually intrusive. Consequently, restoration strategies that effectively accelerate natural plant regeneration processes are required. Slate waste tips present extreme conditions for plant establishment with multiple potential limiting factors (e.g., lack of organic matter, nutrients, and poor water retention). In this study, we investigated ecological strategies to accelerate natural regeneration at the largest slate quarry in Europe. A field experiment was conducted to assess ecosystem restoration using a contrasting set of native woody species. Treatments included amendments of waste tips with: polyacrylamide gel to increase water‐holding capacity; mineral fertilizer to increase nutrient supply; and two treatments that increased both (organic waste or boulder clay addition). Ecosystem recovery was evaluated through above‐ and below‐ground productivity (plant and microbial, respectively) and soil analyses. Neither increasing nutrient supply (with mineral fertilizer) nor water‐holding capacity (with polyacrylamide gel) was sufficient, alone, to improve plant establishment. However, both boulder clay and organic waste amendment significantly enhanced plant growth. There was a marked positive interaction in the effects on tree growth of the amendment with organic waste and boulder clay. Large interactions occurred between tree species and substrate amendments. The growth of N₂‐fixing species was strongly favored over non‐fixers where there was no addition of material increasing soil nitrogen supply, whereas the growth advantage of pioneer species over non‐pioneers was greatest with fertilizer, organic waste, or clay additions. Organic waste addition had the greatest positive impact on soil processes.     

Seston quality controls zebra mussel (Dreissena polymorpha ) energetics in turbid rivers

Feeding processes and energetic balance of zebra mussels were both related to the quantity and quality of natural seston. Filtration rate and pseudofeces production increased while clearance rate remained constant with increasing seston concentration. Ingestion rate, assimilation efficiency, and assimilation rate all increased with increasing food quality, measured as the ratio of organic to inorganic material in the seston. Respiration rate did not change with either food quantity or quality. As a result, scope for growth declined with decreasing food quality, and fell below 0 cal mg⁻¹ h⁻¹ at an organic:inorganic ratio of 0.5. The association between feeding processes and food quality appears related to a breakdown in the ability of zebra mussels to selectively ingest high-quality organic particles when the organic content of the seston is low. Ingestion, assimilation efficiency, assimilation rate and scope for growth were all higher when seston was amended with an addition of a natural assemblage of algae. Food quality may be a better indicator of environmental conditions suitable for growth than food quantity. These results suggest that the conditions of high suspended inorganic sediment concentrations in large turbid rivers represent a difficult growth environment for the zebra mussel. Received: 12 May 1997 / Accepted: 7 July 1998     

Sewage effects on the food sources and diet of benthic foraminifera living in oxic sediment: A microcosm experiment

A microcosm experiment was conducted to investigate the effects of sewage-derived particulate organic matter (POM) on the food sources and diets of two species of intertidal benthic foraminifera, Ammonia beccarii and Haynesina germanica, using lipid biomarkers to determine trophic relationships. The lipid content of the sediment and associated micro-organisms was a guide to potential food sources while that of the foraminifera was a guide to what they had actually eaten. Six microcosm tanks were established, with constant salinity, temperature and oxygen content, and each with a thin layer of sediment containing living foraminifera. Three microcosms were used as controls and three were treatments to which the POM from secondary treated sewage was added. Each microcosm was treated as a single replicate (to avoid pseudoreplication). The experiment was run for 38 days. The results showed that the food sources (from the sediment) and the diet of the foraminifera did not significantly differ in the controls or the treatments, but quantities of fatty acids decreased in both the sediment system and the foraminifera over the duration of the experiment. It is concluded that sewage-POM (secondary treatment) does not have a direct effect on the food sources of the foraminifera or their diet. The foraminifera did not feed directly on the sewage-derived POM, nor did the addition of sewage stimulate growth of micro-organisms associated with the sediment system. However, recent field data collected by the authors provides evidence that season plays an important role in foraminiferal response to organic pollution (OP), and microcosm sediment might have been unknowingly collected at a time when foraminifera are now known not to respond to OP, i.e. in summer.     

Refractory dissolved organic matter can influence the reproduction of Caenorhabditis elegans (Nematoda)

1. We investigated the effect of refractory dissolved organic matter (refractory DOM: fulvic acids (FAs) and ultrafiltrates (UFs)), isolated from five different sources, on the reproduction of the bacterivorous nematode Caenorhabditis elegans. Nematodes were exposed to DOM (0.5–64 mg L?1 dissolved organic carbon) during a whole life cycle (72 h). At the end of the test, the number of offspring per worm was determined.
2. We also studied the effect of refractory DOM on abundance, cell size, and activity of the bacteria (Escherichia coli) that were used as a food source for the nematodes, to assess possible indirect effects of DOM via the food organisms.
3. The effects of DOM on the reproduction of C. elegans varied, depending on the origin and concentration of DOM. FAs isolated from a soil leachate and from the effluent of a waste water plant, as well as UFs from a humic lake and from a marsh, stimulated the reproduction of C. elegans. FAs from ground water had no effect, while FAs from a humic lake inhibited the reproduction of the nematodes. All effects occurred at ecologically relevant DOM concentrations and showed clear dose–response relationships.
4. Neither bacterial abundance nor cell size were influenced by refractory DOM. Bacterial activity was unaffected by four types of DOM. Only FAs from the humic lake caused a significant decrease in bacterial activity over 72 h.
5. The negative effect of FAs from the humic lake on nematode reproduction may be a consequence of a lower bacterial activity in this treatment. The positive effects of refractory DOM, however, could not be related to bacterial parameters. Therefore, we assume that the DOM directly influenced the reproduction of C. elegans. We speculate that refractory DOM can potentially be an additional carbon source or a source of trace nutrients influencing the reproduction of C. elegans. Adsorption of refractory DOM on bacterial cells, serving as food for the nematodes, may have been an important factor for the availability of DOM for C. elegans.     

The Effect of CO2 on Algal Growth in Industrial Waste Water for Bioenergy and Bioremediation Applications

The energy, mining and mineral processing industries are point sources of metal-contaminated waste water and carbon dioxide (CO₂). Freshwater macroalgae from the genus Oedogonium can be grown in metal-contaminated waste water to generate biomass for bioenergy applications and concomitantly bioremediate metals. However, interactions between CO₂ addition and algal growth, which can affect bioremediation, remain untested. The addition of CO₂ to algal cultures in the Ash Dam Water (ADW) from a coal-fired power station increased the biomass productivity of Oedogonium sp. from 6.8 g dry weight (DW) m^-2 d^-1 to a maximum of 22.5 g DW m^-2 d^-1. The greater productivity increased the rate of bioremediation of most elements. However, over time carbon-amended cultures experienced a decline in productivity. Possible explanations include metal toxicity at low pH or essential trace element limitation as a result of competition between toxic and essential trace elements for uptake into algae. Higher productivity increased bioremediation rate and yielded more biomass for bioenergy applications, making maintenance of maximum productivity the central aim of the integrated culture model. To do so it will be necessary to resolve the mechanisms responsible for declining yields over time in carbon-amended cultures. Regardless, our data demonstrate that freshwater macroalgae are ideal candidates for bioremediation of metal-contaminated waste streams. Algal culture delivered significant improvement in ADW quality, reducing 5 elements that were initially in excess of water quality criteria (Al, As, Cd, Ni and Zn) to meet guidelines within two to four weeks.     

Do biogenic sulphur compounds in phytodetritus act as cues for deposit-feeder activity? Field experiments and observations on the echiuran worm Maxmuelleria lankesteri

In temperate coastal seas, phytodetritus settling from the spring phytoplankton bloom is a potential food source for benthic deposit-feeders. The ability to exploit this seasonally variable resource could be enhanced by sensitivity to chemical cues signalling its arrival at the seabed. The biogenic sulphur compound dimethylsulphide (DMS), a breakdown product of dimethylsulphonioproprionate (DMSP) produced by some phytoplankton species, is a potential candidate for this role. We investigated the behavioural response of a sedentary surface deposit-feeder, the echiuran worm Maxmuelleria lankesteri, to DMS by observations and manipulative experimentation under natural conditions in a Scottish sea loch. Experimental addition of sediment enriched with DMSP-producing phytoplankton caused no significant increase in either the frequency of feeding by M. lankesteri or the rate of sediment ejection from observed burrows. Naturally occurring (DMSP+DMS) content of surface sediment was low during the winter, then peaked in April before declining in May. There was no consistent relationship between this parameter and rate of sediment ejection from M. lankesteri burrows. The results therefore provide no evidence that M. lankesteri uses DMSP or DMS as a stimulus to increased activity. An observed imbalance between the frequency of surface deposit-feeding and sediment ejection from individual burrows remains unexplained.     

Impacts of fine sediment addition to tussock, pasture, dairy and deer farming streams in New Zealand

1. Increased fine sediment input caused by agricultural development is expected to act as a stressor for stream ecosystems. In a large‐scale field experiment, we added fine river sand to 50‐m reaches of three second‐order streams in each of four categories of catchment development (ungrazed tussock grasslands, grazed pasture, dairying and deer farming) and measured the responses of macroinvertebrates and aquatic moss. 2. Before addition, fine sediment cover differed between land uses, being lowest in tussock (7%), intermediate in pasture (30%) and dairy (47%) and highest in deer streams (88%). Sediment addition increased cover by one land‐use category (e.g. augmented sediment cover in tussock streams was similar to pre‐existing cover in pasture streams), and cover remained high in impact reaches (compared with controls) throughout the 5‐week experiment. Sediment addition did not change concentrations of phosphate, nitrate and ammonium, which were generally highest in dairy streams and lowest in tussock streams. 3. Aquatic mosses (most common in tussock, absent in dairy and deer), invertebrate density (highest in deer, lowest in tussock), taxon richness (highest in pasture, lowest in deer) and diversity (highest in pasture and tussock, lowest in dairy and deer) all differed between land uses. Sediment addition resulted in reductions of moss cover, invertebrate taxon richness and richness of Ephemeroptera, Plecoptera and Trichoptera in impact relative to control reaches. 4. The impact of sediment addition was strongest in pasture streams where pre‐existing sediment cover was moderate and richness and diversity of the invertebrate community highest. However, even in the already sediment‐rich and species‐poor deer streams, density of one common taxon was reduced significantly by sediment addition, and another two were affected in the same way in dairy streams, the second‐most intense land use. 5. Our experiment has disentangled the impact of sediment addition from other concomitant land‐use effects that could not be reliably distinguished in previous research, which has mainly consisted of correlative studies or unrealistically small‐scale experiments.