Causal Assessment of Biological Impairment in the Little Floyd River,Iowa, USA

An assessment of biological impairment in the Little Floyd River (Iowa, USA) was based on evidence of three characteristics of causation: co-occurrence, preceding causation, and sufficiency. Evidence of the physical interaction of the probable causes and the biota, resulting alterations to the biota, as well as the time order of the cause and the effect were consistent within the assessment, but the evidence for these causal characteristics did not discriminate among probable causes or other causes. Deposited sediment, low dissolved oxygen, heat stress, and ammonia toxicity are the probable causes of impaired biological condition in the Little Floyd River compared with other rivers in the ecoregion. Less likely causes are suspended sediment, altered basal food resources, and flow alteration. Very unlikely causes are pH shifts, total dissolved solids, Cyprinus carpio (an invasive species), metal toxicity, and pesticides. Data were insufficient to assess salinity or other toxicants. The assessment was used to develop a recovery plan for the stream. This assessment demonstrates that, even when there are many candidate causes and uncertainties are substantial, the probable causes of biological impairments can be determined with enough certainty to inform decision-making to address environmental problems.     

Using Field-Based Species Sensitivity Distributions to Infer Multiple Causes

We describe a new way to develop evidence of causes of biological effects using field-based species sensitivity distributions (SSDs) and show how evidence can be compared when genera or effect endpoints are different among potentially causal agents. To evaluate if a cause is sufficient to elicit an effect, we developed a general SSD. A cause was judged sufficient if the intensity of the stressor at the site predicted the observed proportion of extirpation. To evaluate if an effect is specific to a cause, we developed site-specific SSDs using field-based effect levels of genera occurring in the locality of the study. An effect was judged specific to a cause if susceptible genera were absent and tolerant genera were present. Field-based SSDs were used to assess nutrients and conductivity. Other associations were used to assess metals, sediment, dissolved oxygen, and temperature. A case study at Pigeon Roost Creek, Tennessee, USA, illustrates how the SSDs are used to infer multiple causes. A weight-of-evidence analysis identified nutrients and sediment as probable causes but another unidentified agent appears to be acting as well. This inferential approach has broad application and the causal models for conductivity, nutrients, and deposited sediment can be used at other locations.     

Biological,chemical and physical characteristics of downwelling and upwelling zones in the hyporheic zone of a north-temperate stream

Along a single stream riffle, there is a typical flow pattern in which surface water enters the hyporheic zone in a downwelling zone at the head of the riffle and hyporheic water returns to the stream surface in an upwelling zone at the tail of the riffle. Distinct patterns of physical and chemical conditions in the hyporheic zone are likely to determine patterns of microbial activity and occurrence of hyporheic fauna. Interstitial water and core samples were taken at three depths in the downwelling and upwelling zones of a single riffle in the Speed River, Southern Ontario, Canada. Physical and chemical characteristics of the hyporheic water, bacterial density, protein content, detritus content and faunal composition of the hyporheic sediment were analysed. The downwelling and upwelling zones differed significantly in temperature, pH, redox potential, dissolved oxygen and nitrate with significant positive correlations occurring among the latter three. There were no differences in bacterial density or detritus content between the two zones nor between depths in either zone, but protein content, considered to be a measure of biofilm biomass, was significantly higher in the downwelling zone. Total density of hyporheic fauna and the number of taxa decreased with increasing depth in both upwelling and downwelling zones, and were positively correlated with surface water characteristics (oxygen, temperature and nitrate), sediment protein content and detritus; however, only a weak correlation was found with zone. The composition of taxa differed between the two zones, and faunal distribution was correlated with dissolved oxygen, detritus, protein content and depth.     

Habitat diversity and ostracod distribution patterns in Belarus

Ostracod diversity and abundance was studied in 10 different types of water bodies of Belarus (bogs, brooks, canals, oxbows, ponds, reservoirs, rivers, springs, shoal of lake and temporary pools). Hydrochemical variables, sediment, and vegetation were analyzed. In total 156 different localities were investigated. Habitat diversity was based mainly upon the closely correlated hydrochemical variables of mineralization (hardness total and carbonate, conductivity, total value of dissolved substances), although bottom, vegetation characteristics and other factors (pH, dissolved oxygen, nutrients) were also significant. The ostracods found included 62 species in 27 genera comprising 8 cosmopolitan, 17 Holarctic, 13 Palearctic species; 21 of these species are known from central and southern Europe and adjacent areas, while 3 are characteristic for eastern Europe. The distribution of freshwater ostracod assemblages reflected the habitat and depended on water body type. Heterogeneous oxbows and temporary pools supported 37 species, while other types of pool maintained only 27–14 species. The population density of different species varied from 0.5 to more than 10 000 ind./m². Indices of local alpha diversity were significantly correlated with the number of species and temperature and were maximal in heterogeneous habitats. The variation of population density was not connected with habitat patterns but appeared to be regulated by the biotic interactions in the community. Habitat diversity, verified by the beta-diversity indices, enabled us to find localities with a similar heterogeneity level and species richness. Beta-diversity values were independent of species number as well as abundance but a significant positive correlation (p < 0.05) was found with temperature, pH and dissolved oxygen. This index probably reflected the general patterns of different localities.     

Terrestrial mesofauna in above- and below-ground habitats: Taylor Valley,Antarctica

In the McMurdo Dry Valleys region of Antarctica, above-ground production is often limited to mosses and algae that occur near seasonally available liquid water such as ephemeral streams and ice-covered lakes. Compared to surrounding dry soils these critical transition zones are highly productive and harbor a more diverse assemblage of soil animals, including rotifers, tardigrades, nematodes and microarthropods. Current cooling trends punctuated by warming events, and predicted future climate warming are expected to affect the hydrology of this region and thereby biodiversity and ecosystem functioning. Above-ground communities are exposed to more variable temperature, relative humidity and greater UV radiation, and may be more vulnerable to climate change than sediments beneath, which are buffered from short-term changes. In this study, we compared above- and below-ground communities associated with either moss or cyanobacterial mats along glacial-fed streams and lakes differing in biological complexity (diversity, productivity and habitat suitability). All groups of soil fauna were more abundant in the above-ground material compared to the sediment beneath. Common indicators of habitat suitability (chlorophyll a, soil pH, soil salinity, and soil nitrogen) did not differ between vegetation types but were significantly different among sites. Variables most correlated with invertebrate abundances were sediment salinity, chlorophyll a content and nitrogen concentration. The McMurdo Dry Valleys are expected to become warmer and wetter as a result of climate change. This will likely increase the area of suitable habitat for most soil animals as areas of liquid water potentially increase and become available for longer periods of time.     

Dissolved oxygen concentration in river sediment of the Lake Biwa tributaries, Japan

The dissolved oxygen concentration in the sediment pore water downstream of rivers in the Lake Biwa basin was measured, and the factors affecting the dissolved oxygen concentration were analyzed. In August 2003, nine rivers (Sakai, Nakanoi, Hebisuna, Anziki, Yasu, Echi, Ane, Oh, and Ohura) were surveyed. The dissolved oxygen was depleted in the sediment pore water of the rivers with a high proportion of particles less than 250 μm in size. For these rivers, the difference between the dissolved oxygen concentrations of the river surface water and the pore water was large, ranging from −9.54 to −5.26 mg L⁻¹. It was found that the proportion of land turned to paddy fields has an effect on the percentage of the particles below 250 μm (standard partial regression coefficient = 0.807, p = 0.023). These results suggest that, in the Lake Biwa basin, the sedimentation of the fine particles released from paddy fields results in poor dissolved oxygen in the river sediment downstream. In addition, the water flow conditions in small- and medium-scale rivers without headwaters also affect the sedimentation of suspended particles.     

凉水和帽儿山地区低级溪流生境和水质状况

为研究不同植被景观土地利用下低级溪流的生境状况和水质差异,对凉水国家级自然保护区红松原始林内和帽儿山国家森林公园境内天然次生林植被和农田背景下各3条溪流生境和水质状况进行调查。对溪流生物特性（悬浮藻、附着藻）和理化性质（温度、混浊度、溶解氧（DO）、pH、NH4^＋-N、NO3^-N、PO4^3-P、总氮（TN）和总磷（11P））以及细小颗粒有机物质（FPOM）和粗大有机物质（CPOM））进行测定。研究结果表明,凉水地区原始林溪流的生境状况好于帽儿山地区的次生林,帽儿山地区农田溪流生境最差。原始林溪流具有稳定的溪底生物生活基质,稳水区和急流区均匀分布,稳水区尺度变化大,受淀积物沉降干扰小,河道较弯曲,河岸稳定,河岸植被覆盖度高;次生林溪流以急流区为主,稳定基质相对较差,并受到一定程度的淀积物沉降干扰,河岸尚稳定,有一定程度的人为干扰;农田溪流基质不稳定,受到强烈淀积物沉降影响,渠道化严重,河岸带植被严重破坏。3种景观背景下溪流总磷（11P）、溶解氧（DO）、混浊度、温度、氮磷比值（N／P）（P〈0．05）存在显著差异。原始林溪流NH4^＋、DO、TP、TN、悬浮藻浓度和pH较高、附着藻数量较多,温度较低、FPOM和CPOM的数量较少;次生林溪流的NO3^--N、N／P和TDIN较高。 浊度较低;农田溪流浊度、温度、PO4^3--P较高,DO和pH较低,附着藻数量较少。景观尺度上的土地利用对溪流生境具有深刻的影响,同时决定溪流的水质状况。     

A hydrobiological survey of a polluted canal

The present state of a man-cut canal and a waste stream discharging into it was assessed. Some chemical and physical aspects of the study area have been measured and the diversity of the macroinvertebrates has been quantified.Species diversity of the net populations varied inversely to the degree of pollution. In the benthos, however, the nature of the bottom seemed to be largely responsible for the changes in community composition: the indices of diversity increased with increase in the amounts of silt and organic detritus. The ranges of phosphate, nitrite, ammonia, temperature, dissolved oxygen, chlorine (in chlorides), hardness, pH, transparency and velocity of the water were insufficient to produce detectable effects upon the diversity of the fauna.The waste stream had no macroscopic animal, save for the pollution-tolerant oligochaete, Limnodrilus.     

Contrasting spatiotemporal patterns and environmental drivers of diversity and community structure of ammonia oxidizers,denitrifiers, and anammox bacteria in sediments of estuarine tidal flats

The spatial and temporal patterns of diversity, community structure, and their drivers are fundamental issues in microbial ecology. This study aimed to investigate the relative importance of spatial and seasonal controls on the distribution of nitrogen cycling microbes in sediments of estuarine tidal flats, and to test the hypothesis that metals impact the distribution of nitrogen-cycling microbes in the coastal system. Two layers of sediment samples were collected from three estuarine tidal flats of Laizhou Bay in 2010 winter and 2011 summer. The alpha diversities (Shannon and Simpson indices) and community structure of ammonia oxidizing bacteria (AOB) and archaea (AOA), denitrifier and anammox bacteria (AMB) were revealed using denaturing gradient gel electrophoresis and clone library analysis of amoA, nosZ and 16S rRNA gene markers. We found that both AOB and AMB exhibited distinct seasonal patterns in either alpha diversity or community turnover; AOA had different alpha diversities in two layers, but neither spatial nor seasonal patterns were found for their community turnover. However, no distinct spatiotemporal pattern was observed for either diversity or community composition of nosZ-type denitrifiers. For correlations between alpha diversities and environmental factors, significant correlations were found between AOB and ammonium, temperature and As, between denitrifiers and nitrite, salinity and Pb, and between AMB and Pb, ratio of organic carbon to nitrogen, ammonium, pH and dissolved oxygen. Salinity and sediment grain size were the most important factors shaping AOB and AOA communities, respectively; whereas AMB community structure was mostly determined by temperature, dissolved oxygen, pH and heavy metals As and Cd. These results stress that ammonia oxidizers, denitrifiers and anammox bacteria have generally different distributional patterns across time and space, and heavy metals might have contributed to their differentiated distributions in coastal sediments.     

Megafaunal Communities in Rapidly Warming Fjords along the West Antarctic Peninsula: Hotspots of Abundance and Beta Diversity

Glacio-marine fjords occur widely at high latitudes and have been extensively studied in the Arctic, where heavy meltwater inputs and sedimentation yield low benthic faunal abundance and biodiversity in inner-middle fjords. Fjord benthic ecosystems remain poorly studied in the subpolar Antarctic, including those in extensive fjords along the West Antarctic Peninsula (WAP). Here we test ecosystem predictions from Arctic fjords on three subpolar, glacio-marine fjords along the WAP. With seafloor photographic surveys we evaluate benthic megafaunal abundance, community structure, and species diversity, as well as the abundance of demersal nekton and macroalgal detritus, in soft-sediment basins of Andvord, Flandres and Barilari Bays at depths of 436–725 m. We then contrast these fjord sites with three open shelf stations of similar depths. Contrary to Arctic predictions, WAP fjord basins exhibited 3 to 38-fold greater benthic megafaunal abundance than the open shelf, and local species diversity and trophic complexity remained high from outer to inner fjord basins. Furthermore, WAP fjords contained distinct species composition, substantially contributing to beta and gamma diversity at 400–700 m depths along the WAP. The abundance of demersal nekton and macroalgal detritus was also substantially higher in WAP fjords compared to the open shelf. We conclude that WAP fjords are important hotspots of benthic abundance and biodiversity as a consequence of weak meltwater influences, low sedimentation disturbance, and high, varied food inputs. We postulate that WAP fjords differ markedly from their Arctic counterparts because they are in earlier stages of climate warming, and that rapid warming along the WAP will increase meltwater and sediment inputs, deleteriously impacting these biodiversity hotspots. Because WAP fjords also provide important habitat and foraging areas for Antarctic krill and baleen whales, there is an urgent need to develop better understanding of the structure, dynamics and climate-sensitivity of WAP subpolar fjord ecosystems.     

Effects of substratum restoration on salmonid habitat quality in a subalpine stream

Stream substratum restoration is a widely applied tool to improve spawning habitat quality for salmonid fishes. However, there is a lack of studies which comprehensively assess effects of the restoration on site, as well as on downstream habitats. Our study addressed effects at both locations and compared abiotic (analyses of texture, penetration resistance, oxygen concentration, redox, nitrite, nitrate, ammonium, pH, electric conductivity, temperature) with biotic (depth-specific macroinvertrebrate abundance and diversity, brown trout hatching success) indicators before and after excavation of the substratum in a highly colmated brown trout spawning site. Strong improvements of hyporheic water conditions (increased oxygen supply and redox potential, reduced concentrations of nitrite and ammonium) as well as ~50 % reductions of substratum compaction and fine sediment content were observed 1 day after the restoration measure. Improvements of habitat quality were still detectable 3 months after treatment. Consequently, the hatching success of Salmo trutta eggs increased from 0 % to 77 % after the restoration. Short-term decrease of macroinvertebrate abundance (from 13.1 to 3.9 macroinvertebrates/kg substratum) was observed within the hyporheic zone of the restoration site, but after 3 months, the number of taxa increased from 13 to 22 taxa and abundance reached 17.9 macroinvertebrates/kg. Significantly increased fine sediment deposition was detected within 1 km downstream of the restoration site and may negatively affect these habitats. Trade-offs between positive effects at restored sites and negative effects in downstream habitats need to be considered for a comprehensive evaluation of stream substratum restoration.     

Changes in shell and soft tissue growth, tissue composition, and survival of quahogs, Mercenaria mercenaria, and softshell clams, Mya arenaria, in response to eutrophic-driven changes in food supply and habitat

Eutrophic-driven changes in the composition of near-bottom seston and surface sediment potentially affect food resources and habitat of commercially important bivalves like quahogs, Mercenaria mercenaria, and softshell clams, Mya arenaria. To define how land-derived nitrogen loads and resulting eutrophication affect bivalves, we compared estuarine features to growth and survival of clams across estuaries receiving different N loads. The major effects of nitrogen enrichment on near-bottom seston and surface sediment were to (1) increase microalgal concentrations and reduce carbon to nitrogen ratios, increasing quantity and quality of available foods, and (2) reduce oxygen content in sediments, potentially reducing habitat quality. Shell growth of juvenile and native clams increased with increasing food supply, driven by N enrichment. Growth of soft tissue followed growth of shell, and %N content of soft tissue increased across N loads, providing direct evidence of a link between N loads and growth responses in clams. In some locations, low salinity limited growth and low oxygen concentrations may have reduced survival. Despite these factors, our data indicate the major effect of N enrichment on clams was increased secondary production in terms of shell and soft tissue growth.     

Modelling faecal <Emphasis Type="Italic">streptococci</Emphasis> mortality in constructed wetlands implanted with <Emphasis Type="Italic">Eichhornia crassipes</Emphasis>

Faecal streptococci mortality was investigated in a water hyacinth (Eichhornia crassipes) constructed wetland pond. The wetland was 7.5 m long, 1.5 m wide and 1.0 m deep, and was implanted with E. crassipes. In order to assess the performance of the system towards bacterial mortality, a mathematical model, based on plug flow philosophy was developed. The model incorporated the role of factors, namely solar intensity, pH, dissolved oxygen, temperature, sedimentation, and root attached growth. Model analysis strongly suggests that bacterial mortality rate constant was largely influenced by two factors, namely solar intensity and root biofilm attachment, with both contributing approximately 70.5% of removal. The contribution of other factors like temperature, dissolved oxygen, pH and sedimentation on bacterial mortality rate were less significant. For example, dissolved oxygen, pH and sedimentation contributed 5%, 8% and 0.82%, respectively. Thus, the sedimentation factor was omitted from the model because of its insignificant contribution. The same was done for temperature, due to low ambient temperature range (3.1°C) in the study area. The overall model bacterial removal efficiency was 83%.     

Using short-term growth of enclosed 0-group European flounder, Platichthys flesus, to assess habitat quality in a Danish bay

Instantaneous growth rates of 0‐group European flounder, Platichthys flesus, obtained from two 9‐day enclosure experiments were used to assess the relative quality of three eelgrass and three bare sand habitats in the Bay of Aarhus, Denmark. Measurements of temperature, dissolved oxygen, salinity, sediment structure and biomass of benthic macrofauna were made during the experiments. Gut content analysis was performed after retrieval of the fish. Growth rates of flounder at two bare sand sites were higher or equal to growth rates at the three eelgrass sites, and at a muddy bare sand site in both experiments. The variation in gut fullness of flounder between vegetated and bare sand sites followed the pattern observed in growth rates, but diverged from the spatial variation in prey abundance, which indicates that there were differences in the feeding efficiency between sites. Overall, habitat complexity, i.e. the presence or absence of vegetation seems to be the most important factor determining the growth rates and, by corollary, habitat quality for juvenile European flounder in the Bay of Aarhus.     

The Effects of a Developing Biofilm on Chemical Changes across the Sediment-Water Interface in a Freshwater Environment

The development of a diatom biofilm on a river sediment was studied using a fluvarium channel with intensive investigations over a total duration of 16 days. The overlying solution was monitored for dissolved calcium, silicon and soluble reactive phosphorus, pH, dissolved oxygen and temperature. The surface of the sediment was sampled for chlorophyll a, algal cell density and porewater profile measurements of calcium concentration, pH and dissolved oxygen were made using microelectrodes. At the end of the experiment the sediment was longitudinally sectioned and porewaters isolated and analysed. A diatom biofilm developed within approximately 5 days leading to a decrease in the concentrations of dissolved silicon and phosphorus in the overlying solution. After approximately 270 hours, the dissolved silicon concentration remained low (average of 6.7 μM). As the diatom numbers increased, photosynthetic activity was evident from increases in dissolved oxygen and pH at the interface. By the end of the experiment diurnal changes in the overlying solution of dissolved calcium, alkalinity and soluble reactive phosphorus were evident. Vertical concentration gradients in dissolved calcium, phosphorus and silicon in the sediment porewater were found at the end of the experiment. The results are consistent with the development of a photosynthetically active diatom biofilm that acted as a barrier to the diffusion of silicon from the porewater. It also induced precipitation and dissolution of calcite and co-precipitation of phosphate with calcite. Chemical fluxes of silicon, calcium and phosphorus were estimated from concentration gradients in the sediment and found to be much smaller than fluxes measured from changes in the bulk solution indicating that processes at the sediment-water interface and biofilm mainly control the flux to the overlying solution.     

Ichthyofaunal Diversity of Kangsabati River at Paschim Medinipur District,West Bengal,India

Fish faunal diversity and their abundance vary to a great extent in respect to physical, chemical and biological parameters of the water body. The present study deals with the fish biodiversity and distribution with respect to several physicochemical characters of the habitat, from August-2013 to January-2015 in the Kangsabati River, Paschim Medinipur District of West Bengal. Occurrence of 45 fish species belonging to 8 orders, 17 families and 29 genera have been noted during the study period. It is evident that the members belonging to Cyprinifomes constitute 41 % of the total fish fauna of the river. Fluctuation in occurrence and abundance of the species are influenced by a number of physicochemical parameters viz. pH, dissolved oxygen, salinity, conductivity and suspended solids.     

小黑山岛海域刺参、魁蚶和紫贻贝生境适宜性分析

以小黑山岛临近海域为研究对象,利用生境适宜性指数(habitat suitability index,HSI)模型选划适宜刺参(Stichopus japonicas)、魁蚶(Scapharca broughtonii)和紫贻贝(Mytilus edulis)增殖修复的区域。分别针对每个修复物种筛选出7个生境评价因子,结合专家赋值法和层次分析法确定每个评价因子的权重,利用GIS空间分析模块将现状调查数据进行插值、重分类和栅格计算,绘制研究区域目标种群生境适宜性地图。结果表明:对于刺参和紫贻贝,研究区域均适宜其生长繁殖,同一物种,相同季节在空间上无站位差异,但各季节的生境适宜性分区变化明显;对于魁蚶来说,东北部海域较适宜增殖,其次为西部海域,四季均以较适宜生境为主,仅冬季出现基本适宜生境。水温是造成季节差异的主要因素,底质类型则是引起生境站位差异的重要原因。可为后续的生物多样性保育和生态修复提供基础资料参考。     

Establishing Causality between Exposure to Metals and Effects on Fish

This study evaluates causal relationships between chronic exposure of fish to metals and effects at different levels of biological organization based on a weight-of-evidence approach. Criteria for evaluation of causality were strength, consistency, and specificity of the association, as well as biological gradient and plausibility. Field sampling was conducted three times between 1998 and 2000, in Furnas Stream, impacted by an abandoned lead mine, and in three other locations, including two reference and one impacted sites. Levels of Pb, Zn, Cd, and Ag in sediments from the Furnas Stream exceeded background levels, and their concentrations were above sediment quality guidelines. Residual levels of metals in fish tissue were high enough to indicate reduced growth, reproduction and/or survival according to toxicological benchmarks. Lead-induced biochemical changes (ALA-D activity depletion) were observed in two species of siluriform catfish. The condition factor of a predatory catfish was reduced, and the percentage of prey generalists was higher in Furnas than at the noncontaminated sites. Reduction in fish community diversity and density was observed. Integration of data provided supporting evidence that observed effects on fish from the Furnas Stream resulted from long-term exposure to metals, however influences from other stressors cannot be ruled out.     

Variation of physico-chemical parameters along a river transect through the Okavango Delta,Botswana

The Okavango Delta depends on water quantity and quality to sustain its ecosystem services. Whereas many studies have been carried out on its hydrology, few have been done on water quality in the delta. Water pH, electrical conductivity (EC), dissolved oxygen (DO), turbidity, total suspended solids (TSS) and dissolved organic carbon (DOC) were monitored at 10 sites along the Okavango–Boro–Thamalakane–Lake Ngami system almost fortnightly from June 2008 to June 2010. Water quality in the delta was generally good, despite high evapotranspiration rates which would normally produce very saline waters. Electrical conductivity and water temperature increased with distance from Mohembo to Lake Ngami, the former most likely due to evapoconcentration. In contrast, pH, DO, turbidity and TSS decreased with distance from Mohembo to Boro at the lower end of the seasonal floodplain, before increasing again to Lake Ngami. Dissolved oxygen and TSS most likely declined due to biological uptake and particle sedimentation, respectively. Strong and significant relationships were observed between TSS and turbidity and between DOC and EC, indicating that turbidity and EC could be useful proxies for routine estimations of TSS and DOC, respectively, in the delta.     

Fractionation by centrifugation of leaf proteins from Brassica napus, Brassica oleracea, Helianthus annuus and Atriplex hortensis as a function of pH and temperature

Chlorophyll-free leaf protein concentrates for human consumption can be produced after separation of the chlorophyll-associated protein from the rest of the leaf protein. This protein separation was studied in four plant species using heat fractiona-tion. Press juice was prepared on a laboratory scale from field grown Atriplex hortensis, Brassica napus. Brassica oleracea and Helianthus annuus. Some further experiments were made with greenhouse grown plant material. After adjustment of pH to values between 4.0 and 8.0 the press juice was heated in water baths at 20, 35, 40, 45, 50, 55 and 60°C with or without 20 min holding time at appropriate temperature. Thereafter the juices were briefly centrifuged at 2500g. The protein content of the sediment was determined and the colour of the supernatant was observed. The species showed different protein sedimentation patterns, especially at neutral and weakly alkaline pH. Brassica napus had rapidly sedimenting proteins, low temperature was sufficient for complete sedimentation of chlorophyll-associated proteins and gave a high percentage of the total press juice protein as chlorophyll-free protein. Atriplex hortensis had slowly sedimenting proteins irrespective of temperature, required high temperature for complete sedimentation of chlorophyll-associated proteins and gave a low percentage chlorophyll-free proteins. Brassica oleracea and Helianthus annuus showed intermediated properties. Reasons for these differences among the species are discussed.