Biological and ecological traits of benthic freshwater macroinvertebrates: relationships and definition of groups with similar traits

• 1 Relating species traits to habitat characteristics can provide important insights into the structure and functioning of stream communities. However, trade‐offs among species traits make it difficult to predict accurately the functional diversity of freshwater communities. Many authors have pointed to the value of working with groups of organisms as similar as possible in terms of relationships among traits and have called for definition of groups of organisms with similar suites of attributes.
• 2 We used multivariate analyses to examine separately the relationships among 11 biological traits and among 11 ecological traits of 472 benthic macroinvertebrate taxa (mainly genera). The main objective was to demonstrate (1) potential trade‐offs among traits; (2) the importance of the different traits to separate systematic units or functional groupings; and (3) uniform functional groups of taxa that should allow a more effective use of macroinvertebrate biological and ecological traits.
• 3 We defined eight groups and 15 subgroups according to a biological trait ordination which highlighted size (large to small), reproductive traits (K to r strategists), food (animal to plant material) and feeding habits (predator to scraper and/or deposit feeder) as ‘significant’ factors determining the ordination of taxa. This ordination partly preserved phylogenetic relationships among groups.
• 4 Seven ecological groups and 13 ecological subgroups included organisms with combinations of traits which should be successively more adequate in habitats from the main channel to temporary waters, and from the crenon to the potamic sections of rivers, and to systems situated outside the river floodplain. These gradients corresponded to a gradual shift from (1) rheophilic organisms that lived in the main channel of cold oligotrophic mountain streams to (2) animals that preferred eutrophic habitats of still or temporary waters in lowlands. The groups with similar ecological traits had a more diverse systematic structure than those with similar biological traits.
• 5 Monitoring and assessment tools for the management of water resources are generally more effective if they are based on a clear understanding of the mechanisms that lead to the presence or absence of species groups in the environment. We believe that groups with similar relationships among their species traits may be useful in developing tools that measure the functional diversity of communities.

     

Time scales and mechanisms of estuarine variability,a synthesis from studies of San Francisco Bay

This review of the preceding papers suggests that temporal variability in San Francisco Bay can be characterized by four time scales (hours, days-weeks, months, years) and associated with at least four mechanisms (variations in freshwater inflow, tides, wind, and exchange with coastal waters). The best understood component of temporal variability is the annual cycle, which is most obviously influenced by seasonal variations in freshwater inflow. The winter season of high river discharge is characterized by: large-scale redistribution of the salinity field (e.g. the upper estuary becomes a riverine system); enhanced density stratification and gravitational circulation with shortened residence times in the bay; decreased tissue concentrations of some contaminants (e.g. copper) in resident bivalves; increased estuarine inputs of river-borne materials such as dissolved inorganic nutrients (N, P, Si), suspended sediments, and humic materials; radical redistributions of pelagic organisms such as copepods and fish; low phutoplankton biomass and primary productivity in the upper estuary; and elimination of freshwater-intolerant species of macroalgae and benthic infauna from the upper estuary. Other mechanisms modulate this river-driven annual cycle: (1) wind speed is highly seasonal (strongest in summer) and causes seasonal variations in atmosphere-water column exchange of dissolved gases, resuspension, and the texture of surficial sediments; (2) seasonal variations in the coastal ocean (e.g. the spring-summer upwelling season) influence species composition of plankton and nutrient concentrations that are advected into the bay; and (3) the annual temperature cycle influences a few selected features (e.g. production and hatching of copepod resting eggs). Much of the interannual variability in San Francisco Bay is also correlated with freshwater inflow: wet years with persistently high river discharge are characterized by persistent winter-type conditions.Mechanisms of short-term variability are not as well understood, although some responses to storm events (pulses in residual currents from wind forcing, erosion of surficial sediments by wind waves, redistribution of fish populations) and the neap-spring tidal cycle (enhanced salinity stratification, gravitational circulation, and phytoplankton biomass during neap tides) have been quantified. In addition to these somewhat predictable features of variability are (1) largely unexplained episodic events (e.g. anomalous blooms of drift macroalgae), and (2) long-term trends directly attributable to human activities (e.g. introduction of exotic species that become permanent members of the biota).     

The ecological significance of the relationship between temperature and duration of embryonic development in planktonic freshwater copepods

The embryonic development times of six planktonic freshwater copepods from Austrian waters (Eudiaptomus gracilis, Arctodiaptomus bacillifer, Arctodiaptomus spinosus, Mixodiaptomus kupelwieseri, Cyclops abyssorum, Mesocyclops leuckarti) were determined at constant temperatures ranging from 1.4°C to 27.3°C. In most experiments the hatching success was very high, low survival occurring only when experimental temperatures closely approached lower and upper lethal ranges. Development times usually decreased with increasing temperatures, retardation in development occurring close to the upper lethal range. The non-linear relationship of development time to temperature is most adequately described by Bělehrádek's equation, quadratic models using log-transformed data perform almost equally well. Data on embryonic development times of planktonic copepods are summarized and regression equations (Bělehrádek's equation) for the relationship between duration of development and temperature are presented. Adaptation to temperature and intra- and interspecific differences and similarities in embryonic development times are discussed in the context of geographical distribution and thermal history of various species and populations. The applicability of general curves relating temperature to duration of development is examined and some of the deficiencies in the data are discussed.     

The alkaline,saline lakes of Uganda: a review

Most saline lakes in Uganda are alkaline and occur in closed basins associated with the Western Rift Valley. They are small shallow lakes exhibiting considerable temporal variation in volume and surface area. They have been categorized as maar lakes. Salinity in these lakes results from evaporative concentration of ions leached from their drainage basins. These lakes can be grouped into three broad categories: carbonate-chloride, sulphate-chloride, and chloride lakes according to the dominant anion(s). The relative amounts of ions in solution determines, in part, the limnochemical characteristics of the lakes. There is some evidence of thermal and chemical stratification in the deeper lakes. Records of the limnobiology in these lakes are scarce and not exhaustive.     

Patterns in stage duration and development among marine and freshwater calanoid and cyclopoid copepods: a review of rules,physiological constraints,and evolutionary significance

Studies of development time of marine and freshwater copepods have taken separate tracks. Most studies on marine copepods report development time of each individual development stage, whereas studies on freshwater copepods report only development time, from egg to nauplius and nauplius to adult. This bias allows comparison of total development time but prevents detailed comparisons of patterns in stage-specific developmental schedules. With respect to egg to adult development time, three general relationships are known: developmental rates are dependent upon temperature and food concentration but independent of terminal body size; freshwater calanoids develop significantly slower than marine calanoids; freshwater cyclopoids develop at the same rate as marine calanoids. Two rules describe stage-specific developmental rates: the equiproportional rule and the isochronal rule. The first rule states that the duration of a given life history stage is a constant proportion of the embryonic development time; the second rule states that the time spent in each stage is the same for all stages. This review focuses on the second rule. From the 80+ published studies of copepod stage-specific developmental times, no species follows the isochronal rule strictly: Acartia spp. come closest with isochronal development from third nauplius (N3) to fourth copepodite (C4). The only pattern followed by all species is rapid development of the first and/or second naupliar stages, slow development of the second and/or third nauplius and prolonged development of the final copepodite stage. Once adulthood is reached, males are usually short-lived, but females can live for weeks to months in the laboratory. Adult longevity in the sea is, however, on the order of only a few days. The evolution of developmental patterns is discussed in the context of physiological constraints, along with consideration of possible relationships between stage-specific mortality rates and life history strategies. Physiological constraints may operate at critical bottlenecks in development (e.g. at the first feeding nauplius, N6, and the fifth copepodite stage). High mortality of eggs may explain why broadcast eggs hatch 2–3 times faster than eggs carried by females in a sac; high mortality of adults may explain why adults do not grow rather they maximize their reproductive effort by partitioning all energy for growth into egg production.     

Drag coefficients of stream bryophytes: experimental determinations and ecological significance

1. Drag coefficients ( C D) of bryophyte-covered rocks were measured to see whether these differed between species. Replicate rocks, each supporting one of six bryophyte taxa, were attached to a base plate mounted on Teflon bearings in a flow tank. The drag force exerted on rocks with and without bryophyte material was measured by a strain gauge at different water velocities.
2. The difference in C D between rocks with and without bryophyte material was calculated for each plant, and expressed as a percentage change ( δC D). This varied significantly from 0 in three of the six taxa. The cushion-shaped moss Bryum blandum increased the C D by around 10%. The moss Blindia lewinskyae and liverwort Cryptochila grandiflora decreased the C D by around 40 and 30%, respectively, presumably reflecting their streamlined growth.
3. Drag characteristics of aquatic bryophytes may help explain differences in their resistance to fast flows. Furthermore, we suggest that some aquatic bryophytes can increase substrate stability by streamlining rocks, rendering them less prone to movement.     

Reproductive ecology of the freshwater red alga Batrachospermum boryanum Sirodot in a temperature headwater stream

The surface and hyporheic fauna of a second-order reach of a northern California Coast Range stream (Big Canyon Creek, Lake Co., CA, USA) was examined using substrate colonization samplers (i.e. hyporheic pots) during both the wet and dry seasons in the prevailing Mediterranean climate of the region. In terms of total number of macroinvertebrate taxa, the surface (0 cm to −5.0 cm within the stream substrate) level had higher richness than any level within the hyporheic (−5.1 cm to −15.0 cm, −15.1 cm to −25.0 cm, or −25.1 cm to −35.0 cm) from the beginning of the dry season (May) to the beginning of the wet season (October); during this period the surface was not subject to disturbance from wet-season storms. During the wet season, richness at the surface was similar to that observed at any of the three hyporheic levels examined. Macroinvertebrate density at the surface was substantially reduced during the wet season; however, mean surface densities always exceeded those found within the hyporheic zone (from 25% to 78% of total macroinvertebrate numbers were found at the surface). Seasonal fluctuations in abundance of total macroinvertebrates and density of many constituent populations were less within the hyporheic zone than at the surface. Apparently, early instars of abundant surface taxa do not penetrate the interstices, and substrate disturbance due to spates is less in deeper levels. Compared with many hyporheic faunas described from other temperate-zone sites, this hyporheic community shows reduced numerical dominance by the Chironomidae.     

Ecological significance of phosphomonoesters and phosphomonoesterase activity in a small Mediterranean river and its estuary

In 1998, the concentration of phosphomonoesters, a biologically available fraction of the dissolved organic phosphorus pool, was measured along Palmones River (a small Mediterranean river in Southern Spain) and its estuary. Due to the extremely low phosphomonoester concentration in the river (usually under detection limits by analytical procedures), a method using chromatographic cartridges to concentrate this compound was used. Phosphomonoester concentration was usually in the nanomolar range, although values up to 6 m were measured in a sampling station near an effluent of domestic sewage and a cellulose pulp plant. Concentrations were always lower than the dissolved reactive phosphorus (mostly orthophosphate). Phosphomonoesters represented a variable percentage of the dissolved organic phosphorus, from negligible percentages up to 56%. Besides, a highly significant correlation between these two phosphorus fractions was found.In addition, phosphomonoesterase (alkaline phosphatase) activity was measured in the water and macrophytobenthos (both algae and aquatic phanerogams) along the river and the estuary. In water, most of the phosphatase activity upstream was regarded as soluble. This was confirmed by the difficulty of performing kinetic studies in the unfiltered samples. On the contrary, the phosphomonoesterase activity in the estuary was attributed to different size fractions, suggesting that phosphomonoesters are used actively as a phosphate source by bacteria and phytoplankton, with relative contributions depending on the sampling period.     

Direct and indirect responses of a freshwater food web to a potent synthetic oestrogen

Endocrine-disrupting chemicals (EDCs) in municipal effluents directly affect the sexual development and reproductive success of fishes, but indirect effects on invertebrate prey or fish predators through reduced predation or prey availability, respectively, are unknown. At the Experimental Lakes Area in northwestern Ontario, Canada, a long-term, whole-lake experiment was conducted using a before-after-control-impact design to determine both direct and indirect effects of the synthetic oestrogen used in the birth control pill, 17α-ethynyloestradiol (EE2). Algal, microbial, zooplankton and benthic invertebrate communities showed no declines in abundance during three summers of EE2 additions (5–6 ng l⁻¹), indicating no direct toxic effects. Recruitment of fathead minnow (Pimephales promelas) failed, leading to a near-extirpation of this species both 2 years during (young-of-year, YOY) and 2 years following (adults and YOY) EE2 additions. Body condition of male lake trout (Salvelinus namaycush) and male and female white sucker (Catostomus commersonii) declined before changes in prey abundance, suggesting direct effects of EE2 on this endpoint. Evidence of indirect effects of EE2 was also observed. Increases in zooplankton, Chaoborus, and emerging insects were observed after 2 or 3 years of EE2 additions, strongly suggesting indirect effects mediated through the reduced abundance of several small-bodied fishes. Biomass of top predator lake trout declined by 23–42% during and after EE2 additions, most probably an indirect effect from the loss of its prey species, the fathead minnow and slimy sculpin (Cottus cognatus). Our results demonstrate that small-scale studies focusing solely on direct effects are likely to underestimate the true environmental impacts of oestrogens in municipal wastewaters and provide further evidence of the value of whole-ecosystem experiments for understanding indirect effects of EDCs and other aquatic stressors.     

Shell microstructure and mineralogy of the Littorinidae: ecological and evolutionary significance

An examination of the shell microstructure and mineralogy of species from 30 of the 32 genera and subgenera of the gastropod family Littorinidae shows that most species have a shell consisting of layers of aragonitic crossed-lamellar structure, with minor variations in some taxa. However, Pellilitorina, Risellopsis and most species of Littorina have partly or entirely calcitic shells. In Pellilitorina the shell is made entirely of calcitic crossed-foliated structure, while in the other two genera there is only an outer calcitic layer of irregular-prismatic structure. A cladistic analysis shows that the calcitic layers have been independently evolved in at least three clades. The calcite is found only in the outermost layers of the shell and in species inhabiting cooler waters of both northern and southern hemispheres. Calcium carbonate is more soluble in cold than warm water and, of the two polymorphs, calcite is about 35% less soluble than aragonite. We suggest that calcitic shell layers are an adaptation of high latitude littorinids to resist shell dissolution.     

淡水有害底栖蓝藻研究进展

底栖蓝藻在全球淡水水域内广泛分布,在河流、湖泊、湿地、泉水水域等均有发现。相比于浮游蓝藻,底栖蓝藻因其隐蔽性、采样困难等关注度较低。针对近十几年有害底栖蓝藻不断过量繁殖的情况,本文对有害底栖蓝藻种类、主要的环境影响因子、有害次级代谢物及监测分析方法进行了总结概括。阐述了在有害底栖蓝藻生物量集聚过程中,光照、温度、营养盐、基质、水流等主要环境因子间的交互关联,并指出藻垫小生境内有害底栖蓝藻与微生物群落间作用的重要性。分析了不同属种有害底栖蓝藻的代谢物种类及影响代谢物产出的因素,总结了目前定性和定量分析有害底栖蓝藻的方法并指出其不足,对预测、定位高水平的有害底栖蓝藻提出了建议。本文为进一步研究有害底栖蓝藻异常增殖机制和有效防控方法提供了参考和借鉴。     

Water quality,substrate, and distribution of macroinvertebrates in the Patuxent River,Maryland

The distribution of benthic macroinvertebrates in the Patuxent River, Maryland, was analyzed for the period between June 1975 and February 1976. Numerical diversity was analyzed using data collected from seven sampling stations along the nontidal portion of the Patuxent River. Both natural and artificial substrates were examined. Dissolved oxygen, temperature, soil texture, and amount of organic matter were also measured to determine their correlation with the invertebrate distribution measurements. A 2-way ANOVA revealed significant interaction between site and collecting period in the diversity measurements of the natural substrates. This site by collecting period interaction was not observed in the collections made from the artificial substrates. Dissolved oxygen and temperature did not change significantly with distance along the river. Soil texture and organic matter varied significantly with distance. The distribution of benthic macroinvertebrates was more closely correlated to substrate than to water quality. this finding contradicts previous work on this portion of the Patuxent River.     

花颜色和花气味的量化研究方法

花颜色和花气味是花部构成的重要内容。在已开展的传粉生态学研究中对二者的报道主要是描述性的,而其量化研究可以为揭示传粉机制提供有力的实验证据。本文主要介绍了花颜色的测量和标定方法,包括比色卡、分光色差仪和便携式光谱仪等;花气味的采集方法,包括动态顶空套袋-吸附采集法、吸附-溶剂洗脱法和固相微萃取法等;花气味的检测和分析方法,包括气相色谱-质谱联用仪分析和电子鼻型超速气相色谱仪分析等;以及昆虫行为学实验方法,包括气相色谱-昆虫触角电位联用技术、Y型嗅觉仪和飞行箱实验等。科研人员可以根据实验材料的特点和实验目的选择适合的量化研究方法。     

A decade of seasonal dynamics and co-occurrences within freshwater bacterioplankton communities from eutrophic Lake Mendota,WI, USA

With an unprecedented decade-long time series from a temperate eutrophic lake, we analyzed bacterial and environmental co-occurrence networks to gain insight into seasonal dynamics at the community level. We found that (1) bacterial co-occurrence networks were non-random, (2) season explained the network complexity and (3) co-occurrence network complexity was negatively correlated with the underlying community diversity across different seasons. Network complexity was not related to the variance of associated environmental factors. Temperature and productivity may drive changes in diversity across seasons in temperate aquatic systems, much as they control diversity across latitude. While the implications of bacterioplankton network structure on ecosystem function are still largely unknown, network analysis, in conjunction with traditional multivariate techniques, continues to increase our understanding of bacterioplankton temporal dynamics.     

Impact of a diazinon calamity in 1996 on the aquatic macroinvertebrates in the River Meuse, The Netherlands

A more or less continuous load of pesticides has been noted in the River Meuse in recent years. In April 1996, when high concentrations (up toca. 1 g 1^–1) of the insecticide diazinon were measured in the River Meuse at the Belgian-Dutch border, the maximum concentration for drinking water production was exceeded. This was alerted after activity changes of fish and daphnids in the biological monitoring systems (RIZA). These observations were compared with literature toxicity data of diazinon, in order to determine the ecological impact of this diazinon discharge on the aquatic macroinvertebrates. LC₅₀ values of several aquatic macroinvertebrate species were exceeded. In addition, a high mortality was observed in bioassays with the midgeChironomus riparius and the caddisflyHydropsyche angustipennis. It is inferred that the species composition of the macrofauna community in the River Meuse is likely to be reduced by such an accident. Recolonization of the River Meuse by sensitive macrofauna species may therefore be prevented by incidental pesticide discharges.     

Seasonal wing length dimorphism in a tropical seed bug: ecological significance of the short-winged form

Summary Short-winged forms of the bug, Jadera aeola, were discovered during the late dry season at a study site on Barro Colorado Island, Panama. They were smaller than long-winged adults not only in elytron and hindwing sizes but also in head, thorax, rostrum and hind femur dimentions. When newly emerged adults were kept under natural photothermal conditions, short-winged females started ovipositing earlier, produced more eggs, and died earlier than did long-winged females. This was partly due to the fact that long-winged adults usually enter diapause after adult energence (Tanaka et al. 1987b). Egg size was another factor contributing to the high egg production in the short-winged form; it was significantly smaller in the short-winged form than that in the long-winged form. Wing form was apparently environmentally induced because all off-spring of short-winged adults became long-winged. No short-winged form was obtained in the laboratory when nymphs were reared on different species of seeds at different photoperiods. Although the factor(s) responsible for determination of the wing form remains unknown, the ecological significance of this short-winged form seems clear, i.e. exploitation of the food resource left in the late dry season. Wing length dimorphism in J. aeola could be a response to unpredictable availability of the food resource determined by seed production of the host plants (Sapindaceae) and by the timing of the onset of a wet season.     

Preference of oviposition plant and hatchability of the diving beetle,Dytiscus sharpi (Coleoptera: Dytiscidae) in the laboratory

For the conservation of the diving beetle, Dytiscus sharpi (Wehncke) (Coleoptera: Dytiscidae), which is included in the Red List of Japan, it is critical to understand its ecological background. In the present study, oviposition preference and hatchability were investigated under laboratory conditions. Possible candidates of oviposition plants were observed in the natural breeding habitats of D. sharpi. Eight aquatic plants were identified, and Oenanthe javanica (Blume) was the major species present in March, when first instar larvae appeared. The number of eggs laid was investigated under the following conditions: (i) eight field plants were authentically recreated at a similar covering rate to that in the natural habitat; (ii) each of the eight plants was set at the same covering rate; (iii) a single plant taken from the field was placed separately. Significant oviposition preference for O. javanica was found when these eight aquatic plants were present in the same aquaria. In addition, hatchability in O. javanica was significantly higher than that in any of the other plants. These results suggest that O. javanica is an important aquatic plant for oviposition by D. sharpi.