Effects of the lampricide, 3-trifluoromethyl-4-nitrophenol (TFM) on the macroinvertebrates of Wilmot Creek

The effects of the lampricide, TFM, on the abundance of macroinvertebrates in the benthos of Wilmot Creek, a hardwater tributary to Lake Ontario, was examined over 1 year. Drifting macroinvertebrates were also collected before, during and after TFM treatment. Significant decreases in benthic abundance were exhibited by Dolophilodes sp., Tubificoidea, Cricotopus sp. and Macrotendipes sp. throughout the 350 days following treatment. Only the decrease in abundance of Dolophilodes sp. and Tubificoidea could be attributed to TFM treatment. Increases in drift abundance observed during treatment were generally an accurate indicator of TFM-sensitive macroinvertebrates. The most sentive taxa (Dolophilodes sp., Dugesia sp. and Tubificoidea) responded immediately following the introduction of TFM. Branchiobdellida, Diamesa sp., Dicranota sp., Lumbricidae and Nemouridae exhibited increases in drift abundance 8–10 h after the introduction of TFM, however, were considered less sensitive than the former taxa because a decline in their abundance in the benthos was not detected.The response of the benthic invertebrates found in this hardwater creek was similar to those observed during studies of softwater streams. Only the most severely affected taxa were not present in the benthos 350 days after treatment.     

Benthic, Drifting and Marginal Macroinvertebrate Assemblages in a Lowland River: Temporal and Spatial Variations and Size Structure

Aquatic macroinvertebrates living in anastomosing lowland rivers use different habitats and respond differently to the hydrological regime. In this paper, the structure and composition of benthic, drifting and marginal macroinvertebrate assemblages are analyzed in the lowland river Ctalamochita (Córdoba, Argentina). The assemblages were studied in an annual cycle; a comparison among the composition of benthos, drift and marginal fauna was carried out; and size structure of the assemblages was characterized. Samples were obtained from two sites: a rural and an urban site. In total 73 taxa of aquatic macroinvertebrates were collected. Benthos was characterized by Chironomidae and Oligochaeta; marginal fauna was mainly constituted by Coleoptera, Heteroptera, Decapoda, the Trichoptera Nectopsyche sp., Ephemeroptera and Odonata. Drifting assemblage was composed by macroinvertebrates from local and remote upstream benthos, and from the marginal zone. Marginal fauna diversity was higher than benthos and drift. Total biomass of the assemblages pooled together was relatively equitably among size classes. Larger size classes consisted of organisms from the marginal zone whereas the smallest ones were composed by benthic and drifting organisms. In the study area there is habitat partitioning in the lateral dimension of the river. Marginal fauna was more diverse due to the asymmetry of transport and deposit processes, which generate a heterogeneous habitat in the bankside. The relation between fine substrate and high current velocity determines an unstable habitat in the central channel, which makes colonization by benthic macroinvertebrates difficult.     

Aquatic insect drift through a final-cut strip mine pit,with emphasis on drift distances

Drift samples were taken upstream and at the outlet of a final-cut strip mine pit through which a portion of the Tongue River, Wyoming, USA, was rerouted. All prominent rheophilic insect species (except cased Trichoptera) were found capable of drifting the length of the pit (> 500 m). However, drift densities leaving the pit were reduced in comparison to those entering it. Pit inhabitants such as burrowing mayflies, Chaoborus flavicans, and several species of Chironomidae were also collected at the pit outlet. Under the physical conditions created by rerouting the river through a strip mine pit, the observed maximum behavioral and background drift distances (> 500 m) were significantly greater than those reported in the past (< 100 m).     

三峡库区不同水文类型支流大型底栖动物对蓄水的响应

为探究三峡水库修建对库区不同水文类型支流大型底栖动物的影响,于2015年7月和2016年1月对三峡水库四条支流的大型底栖动物进行调研,分别对周期性受蓄水影响支流的非回水区与回水区和长期受蓄水影响支流的非回水区与回水区大型底栖动物群落结构进行比较研究,结果表明:⑴7月份三峡水库145米低水位时期共采集到底栖动物655头计59种(属),在受蓄水影响河段采集到底栖动物4种共40头,优势种为日本沼虾(占受蓄水影响区域的57.5%); 1月份三峡水库175米蓄水时期共采集到底栖动物1123头计69种(属),在受蓄水影响河段采集到16种238头,优势种为锯齿新米虾(占受蓄水影响区域的14.2%)。⑵周期性受蓄水影响支流的非回水区与回水区底栖动物密度、生物量和多样性指数无显著差异(P0.05);长期受蓄水影响支流的非回水区与回水区之间底栖动物密度和Pielou均匀度指数无显著差异(P0.05),但非回水区底栖动物生物量显著高于回水区(P0.05),底栖动物多样性和丰富度极显著高于回水区(P0.01)。⑶7月份影响底栖动物分布的主要环境因子共6个,分别是水深、流速、硝态氮、溶解氧、水温和电导率; 1月份影响底栖动物分布的主要环境因子共7个,分别是水温、溶解氧、总磷、流速、深度、电导率和透明度。     

Water quality of a southeast Texas stream

Water quality of Menard Creek in the Big Thicket National Preserve of southeast Texas was studied from July 1978 to June, 1979 utilizing physicochemical parameters, bacteriological data, and benthic macroinvertebrates.Physicochemical conditions generally indicated good water quality. Dissolved oxygen concentrations were always high and all other parameters were within the expected ranges for small streams in this area. Conductivity and chlorides indicated low concentrations of oil field brines at Stations 4 and 5.Numbers of fecal bacteria were higher than acceptable at all stations during much of the study period. Highest numbers were generally found after heavy rains and surface runoff. Fecal coliform to fecal streptococci ratios indicated human contamination in 53 percent of the 60 samples, while non-human contamination was found in 12 percent of the samples.125 taxa and 7,462 individuals of benthic macroinvertebrates were collected. Chironomids (44.8%, 38 sp.) and oligochaetes (32.1%, 13 sp.) were the dominant groups. The oligochaete Aulodrilus pigueti and the trichopterans Lype diversa and Brachycentrus numerosus were reported in Texas for the first time. The greatest number of taxa was found at Station 1 (79), while Station 5 had the fewest (61). Station 1 had the highest annual species diversity ({xxd}) of 4.37. The other stations had intermediate to high values indicating moderately stressed conditions during high discharge. Sørenson's (1948) index of similarity showed relatively high coefficients of faunal similarity between stations, depending on discharge.This research was financed by contract number PX 7029-8-0789 from the National park Service and Lamar University research fundsThis research was financed by contract number PX 7029-8-0789 from the National park Service and Lamar University research funds     

Macrobenthic distribution and community structure in the upper navigation pools of the Upper Mississippi River

The northern section of the Upper Mississippi River supports a diverse macrobenthic assemblage. Distribution of this benthic fauna, benthic community structure, and factors which influences which influence both of these phenomena in these upper pools are reviewed. Dumping of heavy loads of municipal and industrial wastes from the Minneapolis-St. Paul metropolitan area has severely stressed the benthic community. Once abundant, pollution-sensitive mayflies, Hexagenia bilineata and H. limbata, are noticeably absent, replaced by pollution-tolerant oligochaetes and midges (notably Chironomus). Harmful effects of this pollution are not restricted to the area immediately downstream from the Twin Cities. In Lake Pepin, the Hexagenia population has suffered a drastic decline. The benthic community is characterized by low species diversity and a dominant, pollution-tolerant Chironomus plumosus — Oligochaeta — Sphaeriidae — Hirudinea community complex. Farther south, effects of the high organic load which originates approximately 226 km upstream are ameliorated. Inundation of large, diverse land areas contributes to the great ecological diversity in Pools No. 7 and No. 8. In Navigation Pool No. 7, benthic standing crops in the backwater pool areas (biomass range: 2.08–26.96 g m^–2) exceed those in the main channel (biomass range: 0.05–1.02 g m^–2). Greater numbers of burrowing mayflies and mollusks were found in the pool areas. Of 131 taxa collected from 1976–1977 in Lake Onalaska, which occupies most of Pool No. 7, eight dominant groups — Oligochaeta, Hirudinea, Isopoda, Amphipoda, Lepidoptera, Diptera, Gastropoda, and Pelecypoda — accounted for 90–93% of the macroinvertebrates. In Pool No. 8, over half of the 144 benthic taxa collected during the summer of 1975 were insect nymphs and larvae. Oligochaetes were by far the most ubiquitous and dominant macroinvertebrates. Habitat preferences of particular benthic forms reflected distributional relationships between macroinvertebrates and physical-chemical conditions. Benthic production, in terms of total wet weight m^–2 and macroinvertebrate density in each study area, was generally greater in the more eutrophic areas. However, fewer taxa were supported in these areas. These taxa were generally pollution-tolerant organisms, such as oligochaetes and certain chironomids, which were capable of burrowing into depositional-type substrates. More taxa and greater numbers of gill breathers and filter feeders, such as caddisflies, mayflies, stoneflies, and dipterans, were collected from less eutrophic areas.     

Weak response of saltmarsh infauna to ecosystem-wide nutrient enrichment and fish predator reduction: A four-year study

We examined the effect of whole-ecosystem manipulations of predator removal and nutrient enrichment on saltmarsh macroinfauna in the Plum Island Estuary, Massachusetts. Nitrate and phosphate loading rates were increased 10× above background levels in experimental creeks, and we significantly reduced (by 60%) the abundance of the killifish, Fundulus heteroclitus, a key predator in this system. Two creek pairs were manipulated; Creek Pair 1 for three growing seasons and Creek Pair 2 for one. Infaunal responses were examined in four habitats along the inundation gradient: mudflat, creek wall, Spartina alterniflora, and S. patens habitats. Although benthic microalgae increased synergistically in our treatments, we detected no long-term, population-level numerical response by any taxon. Similarly, no long-term species diversity or community responses were observed. However, nutrient enrichment increased the population biomass of the polychaete Manayunkia aestuarina in the creek wall habitat and the oligochaete Cernosvitoviella immota in the S. alterniflora habitat. No numerical or biomass responses of infauna were detected in predator removal treatments although indirect effects associated with killifish reduction may have contributed to an ephemeral interaction between nutrient addition and predator reduction in S. patens habitat. Our data suggest that population and community responses between benthic microalgae and macroinfauna are not tightly coupled even though some species benefit from increased benthic algae biomass by achieving larger body size.     

Age structure and growth of Semotilus atromaculatus(Mitchill) in PCB‐contaminated streams

Creek chub Semotilus atromaculatus from two PCB contaminated streams (Clear Creek and Richland Creek) at three locations and a reference stream (Little Indian Creek), Indiana, U.S.A., were examined to determine if age class structure and growth variables were correlated with in‐situ PCB exposure. Approximately five to 15 fish were captured weekly during the spring spawning season and monthly thereafter for a 12 month period. Fish collected ranged from 25 to 267 mm total length (L_T). Throughout the course of this study, no spawning activity was observed at either location in Clear Creek, although some very small young‐of‐the‐year (YOY) creek chub fry were observed at the downstream location by late summer. Creek chub nests were observed in both Richland Creek and Little Indian Creek but YOY were common only in Little Indian Creek. Exposure to PCBs was shown to both enhance and decrease growth in varied laboratory tests; subtle but significant gender‐specific differences in the growth of creek chub populations between the sites were observed. Creek chub up to 24 months in age from Clear Creek and Richland Creek were significantly larger (both L_T and mass for males and L_T for females) than reference site creek chub. This trend was reversed for creek chub aged ≥24 months as the reference site fish were consistently larger with reference males weighing significantly more. Older age classes of creek chub were missing in areas of higher PCB contamination. Female population growth rates and individual instantaneous growth rates were consistently higher at the reference site in comparison to the PCB‐contaminated sites. Calculation of ‘functional b’(as a condition factor) did indicate that growth enhancement in young males did occur at the most contaminated site and reductions in growth (mass relative to L_T) occurred in females from all contaminated sites. Furthermore, long‐term survivorship for females was reduced in the PCB‐contaminated streams. All of these subtle alterations in growth would not have been observed if males and females had not been analysed separately.     

Recovery of the macroinvertebrate community below a wastewater treatment plant input in a Mediterranean stream

We sampled chlorophyll a, benthic organic matter, and benthic macroinvertebrates in June 2001 in La Tordera stream (Catalonia, NE Spain), receiving a wastewater treatment plant (WWTP) input. Samples were collected in six equidistant transects in three reaches located upstream (UP), few m below (DW1), and 500 m below the WWTP input (DW2). Our first objective was to assess the effects of the point source on the structure and functional organization of the benthic macroinvertebrate community. Our second objective was to determine if the self-purifying capacity of the stream implied differences between the communities of the DW1 and the DW2 reaches. The WWTP input highly increased discharge, nutrient concentrations, and conductivity and decreased dissolved oxygen. At the DW1 and the DW2 reaches, taxa richness, EPT taxa (Ephemeroptera, Plecoptera, and Trichoptera), and Shannon diversity decreased and gatherer relative density increased relative to the UP reach. At the UP reach, CPOM and FPOM standing crops were similar, whereas at the DW1 and the DW2 reaches CPOM was two times higher than FPOM. Detailed analysis showed that major changes in the benthic community occurred abruptly between 80 and 90 m downstream of the point source (middle of the DW1 reach). At this location, chlorophyll a concentration, density of macroinvertebrates, taxa richness, and scraper relative density increased, whereas gatherer relative percentage decreased. The macroinvertebrate community at the DW2 reach was comparable to that at the second middle of the DW1 reach (DW1B). The macroinvertebrate community at the DW1B and the DW2 reaches were quite similar to that at the UP reach, indicating that the recovery capacity of the stream from nutrient enrichment was high.     

Diel foraging in relation to available prey in an Adirondack Mountain stream fish community

The diets of the fish community of Trucka Brook, a small stream located in the central Adirondack Mountains in northern New York, were examined in relation to the bottom fauna and invertebrate drift. Measures of overlap were calculated between the diets of each fish species examined, brook trout (Salvelinus fontinalis), blacknose dace (Rhinichthys atratulus), creek chub (Semotilus atromaculatus) and pearl dace (Semotilus margarita). Overlap was also examined between the fish diets and bottom and drift samples. Blacknose dace, pearl dace and brook trout had the most similar diets which were closely associated with the benthos. Creek chub had the most distinctive diets which did not compare well with any other fish species during either diurnal or nocturnal periods. The mayfly nymph Litobranchia recurvata was the most abundant bottom invertebrate and was the major prey of benthic feeding fishes. The invertebrate drift did not compare favorably with any of the fishes' diets because of the predominance of large cased limnephilid larvae (primarily Psychoglypha sp.) which were not readily consumed by fish.     

Spatial and temporal distribution patterns of the macrozoobenthos assemblage in the salt marshes of Tejo estuary (Portugal)

The present study focuses on the spatial and temporal distribution of the macroinvertebrate community of the salt marsh areas of the Tejo estuary, based on surveys conducted from autumn 1998 to summer 2000. Samples were collected quarterly in five different intertidal areas along an elevation gradient in: mudflats, creek mouths, creeks, pioneer salt marsh areas and middle marsh areas. A total of 36 benthic invertebrate taxa were identified. Insect larvae were the most well represented group, with 10 taxa identified. Oligochaetes and ostracods were the most numerically abundant taxa, whereas bivalves dominated in biomass. Benthic macroinvertebrate assemblages were dominated, both in number and biomass, by deposit feeders. Three distinct macroinvertebrate assemblages were distinguished along the elevation gradient, based on species presence, density and biomass: the unvegetated muddy areas with a macrobenthic assemblage composed mostly by infauna; the salt marsh pioneer areas of Spartina maritima in which several epibenthic taxa were found, as well as endobenthic taxa characteristic of muddy sediment; and the creek margins, with epifauna taxa such as insect larvae and crustaceans and a low abundance of benthic infauna. Total biomass in the unvegetated and Spartina areas was higher during spring and summer mainly due to the increase in biomass of Scrobicularia plana and Hydrobia ulvae. No decreases in the salt marsh macroinvertebrate biomass values were observed during the highest densities of their potential nektonic predators (summer). This fact might indicate that macroinvertebrates are not a limiting resource for the nektonic species, and that the natural biomass increment of these invertebrate species could be masking the predation/disturbance caused by the nektonic species.     

Colonization and succession of benthic macroinvertebrates in Arcadia Lake,a South-Central USA reservoir

Colonization and succession of benthic macroinvertebrates in Arcadia Lake, an urban reservoir, were studied for four years. Physicochemical conditions including water temperature, dissolved oxygen concentrations, pH, specific conductance, and Secchi disc depth were also recorded. Colonization of the reservoir occured fairly rapidly through a sequence of three invasions. The first, and most significant, colonists were primarily facultative species already present in streams and ponds that were inundated by the impoundment. Later arrivals tended to be limnophilic species that probably came from other bodies of water. Of 30 species encountered in a pre-impoundment collection, only six were still present three years following impoundment. Thirty-three additional benthic macroinvertebrates species invaded the area following impoundment. Dominant taxa in the reservoir included Dero nivea, Limnodrilus sp., Chaoborus punctipennis, Chironomus sp., and Procladius sp. Pollutants accumulating in this urban reservoir, including metals and pesticides, and siltation probably have kept benthic populations relatively low and possibly reduced potential species diversity.     

The ecological effect of acid conditions and precipitation of hydrous metal oxides in a Rocky Mountain stream

Periphyton and benthic invertebrates assemblages were studied at the confluence of two Rocky Mountain streams, Deer Creek and the Snake River near Montezuma, Colorado. Upstream from the confluence the Snake River is acidic and enriched in dissolved trace metals, while Deer Creek is a typical Rocky Mountain stream. In the Snake River, downstream from the confluence, the pH increases and hydrous metal oxides precipitate and cover the streambed. The algal and benthic invertebrate communities in the upstream reaches of the Snake River and in Deer Creek were very different. A liverwort, Scapania undulata var. undulata, was abundant in the Snake River, and although periphyton were very sparse, there were as many benthic invertebrates as in Deer Creek. Downstream from the confleunce, the precipitation of hydrous metal oxides greatly decreased the abundance of periphyton and benthic invertebrates. This study shows that in streams metal precipitates covering the streambed may have a more deleterious effect on stream communities than high metal-ion activities.     

Distribution and seasonal abundance of benthic macroinvertebrates in a subtropical Florida lake

We studied the distribution and seasonal abundance of benthic macroinvertebrates from July 1975 through September 1976 in a hypereutrophic lake in subtropical Florida. The benthic community was comprised principally of oligochaetes (56.1%), chironomids (37.1%), and chaoborids (5.7%). Numbers of taxa and mean densities correlated negatively with depth and positively with mean grain size of the substratum and dissolved oxygen concentration at the mud-water interface. Seasonal abundances and life history information obtained for the predominant species of Chironomidae (Polypedilum halterale, Glyptotendipes paripes, Chironomus crassicaudatus, Cryptochironomus fulvus, C. blarina, Cladotanytarsus sp., Procladius culiciformis, and Coelotanypus concinnus) indicated that all of these species are multivoltine with rapid generation times. Larval lengths of life at summer temperatures, 27–31 °C, ranged from 14–22 days indicating that sampling in subtropical lakes should be at short intervals (approximately 3 days) if the life cycles, ecology, and function of the components of the benthic community is to be understood.     

Effects of the lampricide, 3-trifluoromethyl-4-nitrophenol (TFM) on the macroinvertebrates of a hardwater river

The effects of the lampricide, TFM, on the benthic macroinvertebrates in the Rouge River, a hardwater tributary to Lake Ontario was examined at 1 untreated and 2 treated sites over a 7 month period. Drift samples were collected from one one of the treated sites during the 5 days bracketing treatment. Significant decreases in relative abundance attributable to TFM were recorded for Chimarra sp., Dugesia sp. and Tubificoidea 2–19 d following treatment. Large reductions were also exhibited by Caenis sp. and Lumbricidae. Two-thirds of the Chironomidae genera and Nematoda tended to decline in abundance 2 d after treatment at only one of the treated sites, probably due to a 2.5 h longer treatment. This decline was followed by a significant increase to greater than pretreatment abundances 17 d later undoubtedly as a result of an upward migration of macroinvertebrates from within the hyporheos. Partial recolonization of the TFM-sensitive benthic taxa was evident 19 d after lampricide treatment with complete recolonization 6.5 months later. With the exception of Caenis sp. those taxa in the present study found to be TFM-sensitive were in accordance with those found in softwater field studies. Chimarra sp., Dugesia sp., Hemerodromia sp., Lumbricidae and Tubificoidea exhibited substantial increases in drift abundance resulting from TFM treatment. Generally drift abundance of the taxa returned to pretreatment levels within 12 h following the completion of treatment. The drift abundance of Chimarra sp. and Dugesia sp. remained above normal throughout the rest of the sampling period likely due to continued irritation or mortalities induced by the presence of TFM in the substrate. Generally, drift was a good indicator of those taxa likely to experience a decline in abundance as a result of TFM treatment.     

新薛河溪流生境底栖动物群落结构季节动态

明确底栖动物在时空尺度上的自然变化规律对有效评估和保护水生态系统十分重要。基于2012年季节调查数据,对新薛河典型生境底栖动物群落季节动态进行了研究。共鉴定底栖动物108种,隶属5门10纲74属。短脉纹石蛾、长钝直突摇蚊、拟长跗摇蚊、Neozarelia sp.为研究区域优势分类单元,相对丰度分别为25.1%、9.8%、9.0%、8.6%;各季节间优势分类单元组成差异较大,3个季度共同优势物种仅短脉纹石蛾1种。密度、物种丰度、香农指数表现为4月和12月显著高于10月;均匀度指数10月份最高。非度量多维标度排序表明,不同季节底栖动物群落结构差异显著;对照河段(D河段)群落结构季节间差异相对较小。指示物种法分离出了新薛河及各河段代表性物种41种,但B河段未分离出指示物种;双向聚类分析进一步明确了指示物种的指示属性(特有或者相对丰度最高)。     

Effects of an invasive crayfish on trophic relationships in north‐temperate lake food webs

1. The introduction of invasive species is one of the main threats to global biodiversity, ecosystem structure and ecosystem processes. In freshwaters, invasive crayfish alter macroinvertebrate community structure and destroy macrophyte beds. There is limited knowledge on how such invasive species‐driven changes affect consumers at higher trophic levels. 2. In this study, we explore how the invasive rusty crayfish Orconectes rusticus, a benthic omnivore, affects benthic macroinvertebrates, as well as the broader consequences for ecosystem‐level trophic flows in terms of fish benthivory and trophic position (TP). We expected crayfish to decrease abundance of benthic macroinvertebrates, making most fish species less reliant on benthic resources. We expected crayfish specialists (e.g. Lepomis sp. and Micropterus sp.) to increase their benthic dependence. 3. In 10 northern Wisconsin lakes, we measured rusty crayfish relative abundance (catch per unit effort, CPUE), macroinvertebrate abundance, and C and N stable isotope ratios of 11 littoral fish species. We used stable isotope data and mixing models to characterise the trophic pathways supporting each fish species, and related trophic structure to crayfish relative abundance, fish body size and abiotic predictors using hierarchical Bayesian models. 4. Benthic invertebrate abundance was negatively correlated with rusty crayfish relative abundance. Fish benthivory increased with crayfish CPUE for all 11 fish species; posterior probabilities of a positive effect were >95%. TP also increased slightly with crayfish CPUE for some species, particularly smallmouth bass, largemouth bass, rock bass and Johnny darter. Moreover, both fish body size and lake abiotic variables explained variation in TP, while their effects on benthivory were small. 5. Rusty crayfish abundance explained relatively little of the overall variation in fish benthivory and TP. Although rusty crayfish appear to have strong effects on abundances of benthic macroinvertebrates, energy flow pathways and trophic niches of lentic fishes were not strongly influenced by invasive rusty crayfish.     

Interim Responses of Benthic and Snag‐Dwelling Macroinvertebrates to Reestablished Flow and Habitat Structure in the Kissimmee River,Florida, U.S.A.

A critical component in the effort to restore the Kissimmee River ecosystem is the reestablishment of an aquatic invertebrate community typical of free‐flowing rivers of the southeastern United States. This article evaluates early responses of benthic and snag‐dwelling macroinvertebrates to restoration of flow and habitat structure following Phase I construction (interim period) of the Kissimmee River Restoration Project. Replicate benthic and snag samples were collected from remnant river channels in Pool A (Control site), and Pool C, the site of the first phase of restoration (Impact site). Samples were collected quarterly for 2 years prior to construction (baseline) and monthly or quarterly for 3 years following Phase I construction and restoration of flow. Baseline benthic data indicate a community dominated by taxa tolerant of organic pollution and low levels of dissolved oxygen, including the dipterans Chaoborus americanus (Chaoboridae) and the Chironomus/Goeldichironomus group (Chironomidae). Baseline snag data indicate a community dominated by gathering‐collectors, shredders, and scrapers. Passive filtering‐collector invertebrates were rare. Following restoration of flow, benthic invertebrate communities are numerically dominated by lotic taxa, including bivalves and sand‐dwelling chironomids (e.g. Polypedilum spp., Cryptochironomus spp., and Tanytarsini). Snags within the Phase I area support an invertebrate community dominated by passive filtering‐collectors including Rheotanytarsus spp. (Chironomidae) and Cheumatopsyche spp. (Hydropsychidae). Results indicate that restoration of flow has resulted in ecologically significant changes to the river habitat template not observed in Pool A. Observed shifts in benthic and snag macroinvertebrate community structure support previously developed hypotheses for macroinvertebrate responses to hydrologic restoration.     

Freshwater diatom and macroinvertebrate diversity of coastal permanent ponds along a gradient of human impact in a Mediterranean eco-region

Mediterranean coastal areas are characterised by heavily transformed landscapes and an ever-increasing number of ponds are subjected to strong alterations. Although benthic diatoms and macroinvertebrates are widely used as indicators in freshwater ecosystems, little is still known about the diatom communities of lowland freshwater ponds in the Mediterranean region, and, furthermore, there are few macroinvertebrate-based methods to assess their ecological quality, especially in Italy. This article undertakes an analysis of benthic diatom and macroinvertebrate communities of permanent freshwater ponds, selected along a gradient of anthropogenic pressures, to identify community indicators (taxa and/or metrics) useful to evaluate the effect of human impacts. A series of 21 ponds were sampled along Tyrrhenian coast in central Italy. Five of these ponds, in a good conservations status and surrounded by woodland were selected as ‘reference sites’ for macroinvertebrates and epipelic diatoms. The remaining sixteen ponds were located in an agricultural landscape subject to different levels of human impact. The total number of macroinvertebrate taxa found in each pond was significantly higher in reference sites than in both the intermediate and heavily degraded ones, whereas the diatom species richness did not result in a good community variable to evaluate the pond ecological quality. The analysis revealed a substantial difference among the compositions of diatom communities between reference ponds and degraded ponds. The former were characterised by the presence of several species belonging to genera, such as Pinnularia sp., Eunotia sp., Stauroneis sp., Neidium sp., all of which were mostly absent from degraded ponds. Furthermore, the taxonomic richnesses of some macroinvetebrate groups (Odonata, Ephemeroptera, Trichoptera, Coleoptera), and taxa composition attributes of macroinvertebrate communities (total abundance, percentages of top three dominant taxa, percentages of Pleidae, Ancylidae, Hirudinea, Hydracarina) significantly correlated with variables linked with anthropogenic pressures. The results of the investigation suggested that diatoms tended more to reflect water chemistry through changes in community structure, whereas invertebrates responded to physical habitat changes primarily through changes in taxonomic richness. The methodologies developed for the analysis of freshwater benthic diatom and macroinvertebrate communities may have a considerable potential as a tool for assessing the ecological status of this type of water body, complying with the European Union Water Framework Directive 2000/60/EC. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: B. Oertli, R. Cereghino, A. Hull & R. Miracle Pond Conservation: From Science to Practice. 3rd Conference of the European Pond Conservation Network, Valencia, Spain, 14–16 May 2008     

Morphological characters and occurrence patterns of juveniles of two estuarine gobies,Acentrogobius kranjiensis and Acentrogobius malayanus,verified by molecular identification

Juveniles of two Acentrogobius species collected in a mangrove estuary in Sikao Creek, southern Thailand, were identified by morphological and molecular methods. A total of 1315 Acentrogobius specimens were collected and grouped into types A (n = 1107, 4·4–12·0 mm standard length, L_S) (melanophore absent or indistinct on posterodorsal contour of caudal peduncle; two rows of melanophore blotches on lateral midline) and B (n = 208, 4·8–12·6 mm L_S) (distinct melanophore on posterodorsal contour of caudal peduncle; a single row of melanophore blotches on lateral midline). Based on the reverse series method, the melanophore patterns of larger juveniles were linked with the smallest specimens possessing adult characters. The homogeneities of mitochondrial cytochrome b region sequences between the two juvenile types and adult Acentrogobius species collected in the study area indicated type A to be A. kranjiensis (homogeneity between type A and A. kranjiensis: 99·3–100%), and type B to be A. malayanus (homogeneity between latter 98·1 and 99·7%). No Acentrogobius juveniles were collected from the surf zone outside the creek mouth, both species apparently spending most of their life histories within the estuarine habitat. During their pelagic phase, A. kranjiensis and A. malayanus dispersed in the upper, middle and lower reaches of the creek. On the other hand, occurrence patterns during the benthic phase of A. kranjiensis and A. malayanus differed, the former showing upstream movement and the latter downstream movement with growth. These results emphasize the necessity of analysing early fish life histories at the species level, and the collaboration between morphological and molecular methods should prove valuable in accurately identifying of larvae and juveniles.