Ostracoda as bioindicators of anthropogenic impact in salt lakes,saltpans, and a lagoon: A case study from the Gulf of Saros coast (NE Aegean Sea), Turkey

The study area consists of wetlands and semi-wetlands (saltpan and salt lakes) that are separated from the Gulf of Saros in the northeastern Aegean Sea by a littoral cordon. Twenty-four samples were collected from the Enez Salt Lake; Dalyan, Enez Gala, Kuvalak, Isik, and Tasalti Lakes; Vakif and Erikli Saltpans; and Karagol Lagoon. The overall distribution of the sediment sizes reveals that they consist predominantly of mud and sand and a mixture of mud, sand, and gravel. The average proportion of gravel size particles is 8.36%. Feldspar and mica are abundant in sand and gravel-sized materials. Ecological conditions of these coastal areas were assessed on the basis of ostracod assemblages that can be considered as useful bioindicators and depend on water depth, temperature, and salinity. In this context, the effects of physical and chemical properties of the environment, geochemistry of the sediment, and anthropogenic impact on the meiofauna, in particular ostracoda, was here evaluated. Cyprideis torosa Jones, a cosmopolitan species of ostracoda, was found in salt lakes. Other species of ostracoda were shown to be affected by environmental conditions. The toxicity of some heavy metals in the saltpans, salt lakes, and hypersaline lagoons was evaluated. Lake Dalyan and Erikli Saltpan display high toxicity for Cu and Cd levels. The distribution of hydrocarbon pollution of terrestrial origin was determined.     

Detecting anthropogenic disturbance in an environment with multiple gradients of physical disturbance,Manukau Harbour,New Zealand

Demonstrating spatial or temporal gradients of effects on macrobenthic communities can be a useful way of providing strong empirical evidence of natural or anthropogenic disturbance. Gradient designs for environmental assessment are sensitive to change for point source data, enabling the scale of the effects of a disturbance to be readily identified. If the spatial scale that is sampled from the point source is adequate, problems of selecting control sites can be avoided. However, sources of spatial variation in macrobenthic communities, which are not related to the impact, can confound the use of gradient designs. This can occur if the natural spatial structure overlaps that of the gradient and cannot be identified either as a location or environmental covariable. The ability to detect point source impacts using a gradient design against natural spatial variability was tested using benthic macrofaunal data collected from Manukau Harbour, New Zealand. Treated sewage wastewater is discharged into the north-west area of the Manukau Harbour. Sandflats in the vicinity of the outfall are also subject to physical disturbance from wind-waves and strong tides. Ordination techniques and the testing of a priori predictions were used to try and separate the relative effects of organic and physical disturbance on the benthic communities. While the occurrence of other environmental disturbances along a gradient of anthropogenic disturbance makes interpretation of community pattern more difficult, the use of a gradient sampling layout, ordination analysis and the testing of a priori predictions enabled impacts of the anthropogenic and natural environmental disturbances to be interpreted. Gradient designs, therefore, provide a method of assessing complex impacts that operate over broad spatial and temporal scales.     

Responses of photosynthesis,leaf conductance and growth to different salinities in three coastal dune plants

The effects of soil-water salinity on growth and photosynthesis of three coastal dune plants were examined by salt-treatment in order to clarify the causal relationship between salinity and plant distribution in a dune habitat. Plants were cultivated hydroponically at three salinity levels: 0, 10 and 100 mM NaCl. With the 100 mM salt treatment,Calystegia soldanella (C₃ species) had the highest relative growth rate (RGR) (0.085 g g⁻¹ d⁻¹), followed byCarex kobomugi (C₃) (0.066), andIschaemum anthephoroides (C₄) (0.060). This order coincides with the distribution pattern of the three species on coastal dunes;Calystegia soldanella is generally distributed in more seaward areas whereasI. anthephoroides occurs further inland. The order of RGR was determined exclusively by leaf area ratio (LAR) among the three species. Due to its C₄ pathway,I. anthephoroides had higher net photosynthetic rate (Pn) and net assimilation rate (NAR) than the two C₃ plants at all NaCl concentrations, despite its low RGR. This apparent discrepancy is explainable by differences of LAR among the three species; LAR ofI. anthephoroides was lowest, and about half that ofCalystegia soldanella. These results suggest that LAR is one of the main determinants of salt tolerance based on RGR, whereas Pn or NAR may not be significant. This article is dedicated to Professor Hideo Iwaki, University of Tsukuba, in appreciation of the sincere encouragement he has given to the authors.     

Aquatic macrophyte communities as bioindicators of eutrophication in calcareous oligosaprobe stream waters (Upper Rhine plain,Alsace)

The results cover a statistical analysis of the correlations between aquatic macrophyte communities and chemical parameters (N–NH₄, N–NO₃, P–PO₄, COD, Temperature, dissolved O₂, Cl) in unpolluted hard waters (upper Rhine rift valley).This study was based on a table of phytosociological relevés for six plant communities, named A, B, C, CD, D and E. The ecological determinism of the communities were defined from: The study of the seven foregoing physico-chemical parameters for 29 groundwater streams on periodical samples of water. The study of the change with time in the aquatic vegetation after change of the trophic status, confirmed by analysis. The comparative study of the vegetation of the streams and parts of the streams with different trophic statuses but fed by the same groundwater table of the Wurmian Rhine gravels.Analysis of the main components showed the good correlation between the macrophyte communities and the trophy (N–NH₄, P–PO₄). These six communities were classified according to the trophic scale. Discriminant analysis was used to compare the classification of the phytosociological sequence with that based on the statistical analysis. The authors give a very precise bioindication scale (based on the macrophyte community) for the eutrophication degree in unpolluted hard waters.     

Cytomorphological alterations of the thymus, spleen, head-kidney, and liver in cardinal fish (Apogonidae, Teleostei) as bioindicators of stress

Morphological and cytological alterations at the light microscope (LM) and transmission electron microscope (TEM) levels were observed in the thymus, spleen, head-kidney, and liver of cardinal fishes (Apogonidae, Teleostei) from the Gulf of Aqaba, Red Sea, sampled from a strongly polluted site at the northern end of the gulf, and compared to similar samples from a clean, reference site. At the polluted site, the most prominent change was the formation of numerous deposits of cells rich in phagosomes with lipofucin, melanin granules, and phagocytosed debris, including a high increase in number and dimensions of Hassall's corpuscles and melano-macrophage centers. The number of Hassall's corpuscles was 20 (+/-8.0)/mm(2) and of melano-macrophage centers 18 (+/-4.0)/mm(2) at the polluted site, and 7.0 (+/-4.0)/m(2) vs. 5.0 (+/-2.0)/mm(2) respectively at the reference site. In numerous instances the head kidney's melano-macrophage centers in fishes from the polluted site were encapsulated by reticulocytes, a phenomenon recognized as a marker of neoplasmosis and possible malignancy. In the spleens of fishes from the polluted site, numerous deposits of cell debris, peroxisomes, and enlarged lysosomes were also observed. The livers (hepatopancreas) of fishes from polluted waters demonstrated very strong hyperlipogeny. Many of their hepatocytes were laden with lipid vesicles, fragmented endoplasmic reticulula, and aberrant mitochondria. Although the observed alterations in the glands and liver do not indicate any immediate threat to the life of the fish, they can become crucial with respect to energy turnover and fecundity trajectories. This study strongly suggests the use of cytological alterations in vital organs, such as were observed, as pathological biomarkers to environmental stress.     

Differences in growth rates among cohorts of Encrasicholina punctifer and Engraulis japonicus larvae in the coastal waters off Tanshui River Estuary, Taiwan, as indicated by otolith microstructure analysis

The hatching dates of Encrasicholina punctifer and Engraulis japonicus larvae collected in the coastal waters off Tanshui River Estuary during the fishing seasons of 1992 and 1993 indicated that these two anchovies had protracted spawning seasons, which resulted in multiple recruitment cohorts. Encrasicholina punctifer larvae recruited to the estuary from October to March, while the majority of E. japonicus larvae came in March-May and to a lesser extent in October and November. The E. punctifer larvae on arrival to the estuary were 17·4–35·6 mm in length, 167ndash;89 days old and had growth rates of 0·4–1·0 mm day⁻¹, E. japonicus larvae were 12·1–32·7 mm in length, 19–62 days old and had growth rates of 0·7–0·9 mm day⁻¹. Growth rates were significantly different among cohorts and positively correlated to water temperature.     

Sea urchin coelomocytes as a novel cellular biosensor of environmental stress: a field study in the Tremiti Island Marine Protected Area,Southern Adriatic Sea,Italy

The aim of the present study was to investigate on the suitability of the sea urchin as a sentinel organism for the assessment of the macro-zoobenthos health state in bio-monitoring programmes. A field study was carried out during two oceanographic campaigns using immuno-competent cells, the coelomocytes, from sea urchins living in a marine protected area. In particular, coelomocytes subpopulations ratio and heat shock protein 70 (HSC70) levels were measured in specimens of Paracentrotus lividus (Lamark, 1816) collected in two sampling sites, namely Pianosa and Caprara Islands, both belonging to the Tremiti Island Marine Protected Area (MPA) in the Southern Adriatic Sea, Italy. By density gradients separation performed on board the Astrea boat, we found an evident increase in red amoebocytes, a subpopulation increasing upon stress, in those specimens collected around Pianosa (strictly protected area with no human activities allowed), unlike those collected around Caprara (low restrictions for human activities). Likewise, we found higher HSC70 protein levels in the low impacted site (Pianosa) by Western blots on total coelomocyte lysates. The apparent paradox could be explained by the presence in the Pianosa sampling area of contaminating remains from Second World War conventional ammunitions and a merchant boat wreck. Metal determination performed using sea urchin gonads by inductively coupled plasma atomic emission spectrometry (ICP-AES) revealed higher Fe and lower Zn levels around Pianosa with respect to Caprara, in accordance with the persistent contaminating metal sources, and thus calling for remediation measures. Taken all together, our results confirm the feasibility of using sea urchin coelomocytes as biosensors of environmental stress.     

浙江苍南南部沿岸海域主要游泳动物生态位及种间联结性

根据2014年苍南南部沿岸海域春季(5月)和秋季(11月)的渔业资源调查资料,采用生态位测度、方差比率法、基于2×2列联表的χ²检验和联结系数(AC)等方法分析群落物种间的相互关系.结果表明： 该海域主要游泳动物按生态位宽度值可划分为广生态位种、中生态位种和窄生态位种3大类,其中广生态位种包括龙头鱼、三疣梭子蟹、口虾蛄等5种,中生态位种包括棘头梅童鱼、哈氏仿对虾和细巧仿对虾等8种,窄生态位种包括日本蟳、六丝钝尾鰕虎鱼和葛氏长臂虾等10种;种对间生态位重叠值差异较大,最大值和最小值分别为0.93和0, 部分游泳动物间可能存在资源利用性竞争.方差比率法分析表明,主要游泳动物总体呈显著正关联,其中有78个种对间的联结性达到显著水平(χ²≥3.841),联结系数(AC)中正显著联结的种对多于负显著联结.     

Deformities in larval Prodiamesa olivacea (Meigen, 1818) (Diptera,Chironomidae) and their use as bioindicators of toxic sediment stress

The early development of epibenthic communities on stabilised coal-waste material from Poole Bay Artificial Reef (PBAR) was studied by deployment of arrays of slabs (each slab, 20 × 20 × 5 cm), suspended 1 m off a sandy seabed, on the PBAR site (50 ° 39′ 72″ N, 01 54′ 79″ W; depth 12 m) in May 1991. Effects of season, substratum orientation and period of exposure on recruitment and community development of epibenthos, as determined from percentage cover and biomass (ash-free dry weight) measurements, were evaluated over the following 14 months. The initial barnacle- and serpulid polychaete-dominated community developed into an ascidian-polyzoan turf on the slab bases and into an algal-hydroid turf on the tops. The number of colonisers reached maxima of about 21 and 12 sessile taxa, on the bases and tops, respectively. Epibenthic biomass was greater on the slab bases than on the tops throughout the study. The main recruitment season was from February to August. Encrusting bryozoans, ascidians and hydroids were generally better competitors for space than were serpulids and barnacles. The small (< 5 cm) mobile invertebrate community was dominated by porcelain crabs (Porcellanidae) and scale worms (Polynoinae). This revised version was published online in July 2006 with corrections to the Cover Date.     

Spatial distribution of growth rates and of epidermal cell lengths in the elongation zone during leaf development in Lolium perenne L.

Relative elemental growth rates (REGR) and lengths of epidermal cells along the elongation zone of Lolium perenne L. leaves were determined at four developmental stages ranging from shortly after emergence of the leaf tip to shortly before cessation of leaf growth. Plants were grown at constant light and temperature. At all developmental stages the length of epidermal cells in the elongation zone of both the blade and sheath increased from 12 m at the leaf base to about 550 m at the distal end of the elongation zone, whereas the length of epidermal cells within the joint region only increased from 12 to 40 m. Throughout the developmental stages elongation was confined to the basal 20 to 30 mm of the leaf with maximum REGR occurring near the center of the elongation zone. Leaf elongation rate (LER) and the spatial distributions of REGR and epidermal cell lengths were steady to a first approximation between emergence of the leaf tip and transition from blade to sheath growth. Elongation of epidermal cells in the sheath started immediately after the onset of elongation of the most proximal blade epidermal cells. During transition from blade to sheath growth the length of the blade and sheath portion of the elongation zone decreased and increased, respectively, with the total length of the elongation zone and the spatial distribution of REGR staying near constant, with exception of the joint region which elongated little during displacement through the elongation zone. Leaf elongation rate decreased rapidly during the phase when only the sheath was growing. This was associated with decreasing REGR and only a small decrease in the length of the elongation zone. Data on the spatial distributions of growth rates and of epidermal cell lengths during blade elongation were used to derive the temporal pattern of epidermal cell elongation. These data demonstrate that the elongation rate of an epidermal cell increased for days and that cessation of epidermal cell elongation was an abrupt event with cell elongation rate declining from maximum to zero within less than 10 h.Abbreviations LER leaf elongation rate - REGR relative elemental growth rates     

Salinity induced changes in haemolymph osmolality and total metabolic rate of the mud crab Rhithropanopeus harrisii Gould, 1841 from Baltic coastal waters

The specific metabolic rate (SMR) and haemolymph osmolality (HO) of the mud crab Rhithropanopeus harrisii Gould, 1841 from Baltic brackish waters were measured at a habitat salinity of 7 psu (T = 15 °C, full air saturation) and after step-wise acclimation to a salinity range of 3-27 psu. Values of SMR at 7 psu varied between 0.40 and 3.89 J g^− 1 WW h^− 1 (n = 25, wet weight range 0.051-1.142 g) and were significantly (p < 0.05) related to the specimen's wet weight (WW) according to the power regression SMR = 0.94 WW^− 0.41 (R² = 0.68). The SMR of females did not differ significantly (p > 0.05) from those of males. When exposed to higher salinities, the SMR of R. harrisii decreased significantly (p < 0.05) and reached a minimum value at 23 psu (0.55 ± 0.05 J g^− 1 WW h^− 1, n = 6). Mean haemolymph osmolality at 7 psu amounted to 581 ± 26 mOsm kg^− 1 (n = 5) and was 2.9 times higher than that of the external medium. R. harrisii hyperosmoregulated its body fluids up to 24 psu (727 mOsm kg^− 1) at which salinity the isosmotic point was reached.     

Right whale occurrence in the coastal waters of Virginia,U.S.A.: Endangered species presence in a rapidly developing energy market

The endangered North Atlantic right whale is susceptible to increased risks associated with the developing energy market off the Virginia coast of the U.S.A., including increased noise exposure from shipping and energy exploration and extraction, and shipping activity. Primarily viewed as a migratory corridor between northern feeding and mating areas and the southern calving area, Virginia waters have not been intensely monitored for right whales. We conducted a 1 yr, continuous, passive acoustic survey from the Virginia coast to the continental shelf to better describe the seasonal occurrence and spatial distribution of right whales in this area. We found that whales were acoustically detected in every month of the year, with increased seasonal occurrences in fall and late winter/early spring, and not just during limited periods of the year. As industry activities continue to increase in the area, these new right whale occurrence data have implications for siting and permitting of offshore energy activities.     

Amphibians as metrics of critical biological thresholds in forested headwater streams of the Pacific Northwest, U.S.A.

1. Amphibians are recognized both for their sensitivity to environmental perturbations and for their usefulness as cost-effective biometrics of ecosystem integrity (=system health).
2. Twenty-three years of research in headwater streams in the Klamath-Siskiyou and North Coast Bioregions of the Pacific Northwest, U.S.A., showed distinct patterns in the distribution of amphibians to variations in water temperature, % fine sediments and the amount of large woody debris (LWD).
3. Here, we review seven studies that demonstrate connections between species presence and abundance and these three in-stream variables. These data were then used to calculate realized niches for three species, the southern torrent salamander, the larval coastal tailed frog and the larval coastal giant salamander, relative to two of these environmental stressors (water temperature and % fine sediments). Moreover, multivariate generalized additive models were used to predict the presence of these three amphibians when these three stressors act in concert.
4. Stream-dwelling amphibians are shown to be extremely sensitive to changes in water temperature, amounts of fine sediment and LWD, and specific thresholds and ranges for a spectrum of animal responses can be used to manage for headwater tributary ecosystem integrity.
5. Consequently, amphibians can provide a direct metric of stream ecosystem integrity acting as surrogates for the ability of a stream network to support other stream-associated biota, such as salmonids, and their related ecological services.     

The palaeoenvironments of coastal lagoons in the southern Baltic Sea,I. The application of sedimentary Corg/N ratios as source indicators of organic matter

C/N ratios of organic matter sources in coastal lagoons and their drainage areas in the southern Baltic Sea region are investigated to determine the origin of organic matter (i.e. terrigenous or marine) in the sediments of the lagoons. These ratios are compared with δ¹³C values in the area. Terrestrial plants in the study area show C/N ratios between 10 and 85, whereas aquatic macrophytes have values in the range of 6 to 44. Peat and shore vegetation have C/N ratios between 15 and 16, and plankton shows values close to 6. In conjunction with δ¹³C values, the C/N ratios in the sediments allow the reconstruction of the Holocene palaeoenvironments and palaeoecology in the lagoons (Oder Estuary and Greifswalder Bodden). Distinct stages in the development of the water bodies, resulting from sea level changes in the region, can be derived: post-glacial lake stages with sandy sedimentation, lacustrine phases with high autochthonous productivity, terrestrial stages with peat formation, sedimentation as a result of marine transgression, and brackish sedimentation after the formation of sand spits and barrier islands. The application of C_org/N_tot ratios instead of C_org/N_org does not have any significant influence on the interpretation of the data and may thus be used in the coastal sediments of the southern Baltic Sea after having applied the test procedures presented in this study.     

Comparisons between the age structures, growth and reproductive biology of two co-occurring sillaginids, Sillago robusta and S. bassensis, in temperate coastal waters of Australia

Sillago robusta and S. bassensis occupy the open sandy areas of the deeper waters (20–35 m) of the inner continental shelf of the lower west coast of Australia. Comparisons were made of their age and size compositions, growth rates, ages and sizes at first maturity, and spawning times. Most S. robusta were less than 3 years old (maximum 7 years), while S. bassensis often reached 7 years of age (maximum 10 years). The maximum length of S. robusta (200 mm) was far shorter than S. bassensis (328 mm), whereas the reverse pertained for the von Bertalanffy growth coeffcient (K), i.e. c. 1.0 v. c. 0.3. Differences in K reflect the fact that c. 80% of the asymptotic length is achieved by S. robusta after 2 years, but not until 6 years of age by S. bassensis. Sexual maturity was reached by up to 50% of S. robusta at the end of their first year of life, and by almost all fish at the end of their second year of life. Most S. bassensis did not reach maturity until the end of their third year of life. In both species, those individuals that reached maturity early, were significantly longer than those that did not reach maturity at the same age. The gonadosomatic indices and proportions of mature gonads, and the numbers of vitellogenic and hydrated oocytes and post-ovulatory follicles, were relatively high in ovaries of both species between December and March. Although both species spawn in these 4 months, some S. bassensis also spawn between September and November and in March and April. In the middle of the spawning period, the ovaries of S. robusta and S. bassensis frequently contained oocytes that ranged widely in size and development, together with post-ovulatory follicles, suggesting that both species are multiple spawners. Juveniles of S. robusta remain in the deeper waters of the inner continental shelf, whereas those of S. bassensis migrate inshore to their nursery areas in surf zones. As S. robusta reaches sexual maturity at an earlier age and smaller size than S. bassensis, it is probably more advantageous for the juveniles of this species to remain in deeper water, and thereby conserve energy for gonadal maturation, rather than migrating into shallow waters for only a very few months.     

The food of Pomatoschistus minutus (Pisces, Gobiidae) in Belgian coastal waters, and a comparison with the food of its potential competitor P. lozanoi

Data are presented on the food and gonadosomatic index of Pomatoschistus minutus obtained from the bycatch of a commercial shrimp trawler. P. minutus has a diverse diet including zooplankton and hyperbenthos but mainly epibenthic and benthic animals. During the spawning season males consumed high numbers of Pomatoschistus eggs, presumably after aggressive take–overs of territories. The food of P. minutus is compared to the food of P. lozanoi of the same size classes obtained from the same hauls. In the absence of data on predator and prey abundance the discussion on possible interference competition between the two species remains largely speculative.     

Gradients of salinity stress, environmental stability and water chemistry as a templet for defining habitat types and physiological strategies in inland salt waters

The search for pattern in the geographic occurrence of salt lake flora and fauna often reveals strong associations of specific taxa with certain types of water chemistry. Solute composition, along with salinity and habitat stability, may provide a templet shaping the distribution of many organisms inhabiting saline lakes. A review of studies demonstrating habitat associations, specific solute tolerance, and ionic and osmotic adaptations provide evidence of fidelity to particular conditions of environmental chemistry across a wide taxonomic spectrum. Under low salinity conditions, some species show osmoregulatory adaptability to varied solute composition but the capacity for such flexibility is reduced with increased salinity and only certain taxa are found in hypersaline waters dominated by a particular solute. Anionic ratios of chloride, bicarbonate–carbonate, and sulfate appear to be especially important determinants of distribution. Specific solute tolerance presents an alternative explanation to disrupted hydrographic connections in describing how biogeographic distributions may be restricted to certain aquatic habitats in arid regions. Physiological adaptations to chemistry, exemplified in the brine fly genus Ephydra, may be an integral part of the evolution, ecology and diversification of saline water organisms.     

Thiol pools and glutathione redox ratios as possible indicators of copper toxicity in the green macroalgae Enteromorpha spp. from the Scheldt Estuary (SW Netherlands,Belgium) and Thermaikos Gulf (Greece,N Aegean Sea)

Defence mechanisms against Cu toxicity were examined in two dominant Enteromorpha species from two coastal water types. The macroalgae were collected at three locations in the eulittoral of the Scheldt Estuary (Netherlands, Belgium) and the Thermaikos Gulf (Greece). For 10 days E. prolifera (Scheldt) and E. linza (Thermaikos) were incubated in seawater media of different salinities: 6, 9, 23 psu and 25, 30, 35 psu, respectively. In one series, media were enriched with 100 μg Cu l-1; responses were compared with those in controls with no extra Cu added. Enteromorpha, which is frequently used as a monitor species for heavy metal contamination, had relatively high Cu tissue levels (0.5–3.8 μmol Cu gdwt-1). Cu levels in E. prolifera controls (Scheldt) decreased with salinity; this was not the case with Cu levels in E. linza controls (Thermaikos). During the 10-d incubation algal protein contents and tissue Cu were rather stable. In E. linza (Thermaikos) algal protein contents were significantly lower than those of E. prolifera (Scheldt), although there was no indication for nitrogen limitation in E. linza. E. linza also had much lower glutathione pools than E. prolifera. Only under acute Cu stress (metal addition) did E. prolifera synthesise metal-binding thiols (phytochelatins). Phytochelatin pools are not suitable as an indicator of the Cu levels in these algae. The glutathione redox ratio GSH:(GSH + 0.5GSSG) was used as an indicator of (Cu-induced) oxidative stress. In E. prolifera (Scheldt) this ratio decreased with algal Cu content (P <0.05), from ~0.5 to ~0.2. The average glutathione ratios in Enteromorpha from the Scheldt and Thermaikos showed some oxidative stress induction with increasing algal Cu contents, however more clearly if Cu was added. As this redox ratio can also be influenced by environmental factors such as irradiance and desiccation, it may not be useful as an indicator for Cu-induced oxidative stress in situ. This revised version was published online in September 2006 with corrections to the Cover Date.     

Stream amphibians as metrics of critical biological thresholds in the Pacific Northwest, U.S.A.: a response to Kroll et al.

1. Kroll, Hayes & MacCracken (in press) Concerns regarding the use of amphibians as metrics of critical biological thresholds: a comment on Welsh and Hodgson 2008 . Freshwater Biology, criticised our paper [ Welsh & Hodgson (2008) Amphibians as metrics of critical biological thresholds in forested headwater streams of the Pacific Northwest. Freshwater Biology, 53 , 1470–1488] proposing the use of headwater stream amphibians as metrics of stream status in the Pacific Northwest (PNW). They argued that our analysis of previously published data reflected circular reasoning because we reached the same conclusions as the earlier studies. In fact, we conducted a meta‐analysis to address new questions about the optimum values and thresholds (based on animal densities) for abiotic stream attributes that were found to be important to these amphibians in earlier studies. This is analogous to determining blood pressure thresholds or fat‐to‐weight ratios that facilitate predicting human health based on meta‐analyses of earlier data from studies that found significant correlations between these variables and relative health. 2. Kroll et al. argued that we should not make inference to environmental conditions across the PNW from data collected in California. We collected data from northern California and southern Oregon, the southern extent of the PNW. We made inference to the Klamath‐Siskiyou and North Coast bioregions, and argued that available research on these headwater species indicates that our results have the potential to be applied throughout the PNW with minimal regional adjustments. 3. Kroll et al. contended that we need reproductive success, survival estimates and density estimates, corrected for detection probabilities, to establish relationships between animal density and stream attributes. Reproductive success and survival estimates are important for demographic modelling and life tables, but they are not necessary to demonstrate meaningful relationships with abiotic conditions. Both corrected occupancy estimates and individual detection probabilities are unnecessary, and take multiple sampling efforts per site, or onerous mark release and re‐capture studies, respectively, to determine accurately. 4. Kroll et al. questioned the use of stream amphibians as a surrogate for measuring physical parameters, such as water temperature, claiming that measuring the physical parameters directly is more efficient. Here they misinterpreted the main point of our paper: stream organisms are integrators of what happens in a catchment, and carefully selected species can serve as surrogates for the biotic community and the relative condition of the network environment. 5. Kroll et al. claimed that we demonstrated weak inferences regarding ecosystem processes. We argue that by relating densities of stream amphibians with changes along abiotic environmental gradients that are commonly affected by anthropogenic activities, we are establishing biological links to gradients that represent important ecosystem processes and identifying biometrics that can be used to quantify the status (health) of these gradients.     

铜锈环棱螺生物扰动对"蓝藻水华"水体底泥及其间隙水中碳、氮、磷含量的影响

实验室内建立小型模拟生态系统,根据铜锈环棱螺(Bellamya aeruginosa)的密度设置了3个处理组和1个对照组.结果显示:铜锈环棱螺对底泥0～0.5 cm及0.5～2 cm有机质影响较明显,显著降低了底泥中的C:P.处理组3和处理组2间隙水NH4+-N含量分别在底泥0～0.5cm及0.5～2 cm深度和对照组之间存在显著差异(p＜0.05).间隙水中NO2--N+NO3--N的变化较复杂,处理组NO2--N+NO3--N含量在0～0.5 cm,0.5～2cm及2～4cm与对照组相比差异显著(p＜0.05).间隙水中DIP含量随底泥深度先增后减,在2～4 cm处含量达最大,DIP含量在0.5～2 cm深度处理组与对照组之间有显著差异(p＜0.05).铜锈环棱螺生物干扰增加了底泥表层有机质的含量,同时降低了其稳定性.