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Caught between a Rock and a Hard Mineral Encrustation: Long-Lived Aquatic Insects Accumulate Calcium Carbonate Deposits in a Montane Desert Stream
Abstract
Aquatic ecosystems overlying regions of limestone bedrock can feature active deposition of calcium carbonate in the form of travertine or tufa. Although most travertine deposits form a cement-like layer on stream substrates, mineral deposits can also form on benthic invertebrates. However, little is known about which taxa may be prone to calcium carbonate encrustation and which life history traits may make taxa more susceptible to becoming encrusted. Here we report the presence of calcium carbonate deposits on live insects collected from a montane stream in the Madrean Sky Islands (Huachuca Mountains) of Arizona between 2011 and 2013. Life history differences are examined between taxa with and without travertine deposits. Thirteen genera of aquatic insects were found with calcium carbonate deposits on the exoskeleton as well as 22 other genera, also encountered in the study stream, that have not previously been found with such deposits. Taxa with calcium carbonate encrustation had significantly longer-lived aquatic stages than those without encrustation. Furthermore, encrustation presence did not differ among aerial dispersal modes. These results suggest that the extent of calcium carbonate deposition on aquatic insects is primarily related to the length of time they are in the stream. Since mineral encrustation may reduce predation pressure and mobility, changes in patterns of travertine formation in these systems may have profound effects on ecological interactions.
... Indeed, bone, made up of hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 ) is well recognized to be an important sink of calcium-associated P in vertebrate organisms (Sterner and Elser 2002). Readers are directed to the aforementioned studies and others (e.g., Moody et al. 2016;Brodie and McIntyre 2019) for further review of the potential impacts of biologically controlled calcification on P cycling. Of note is the opportunity for skeletal-P to be a terrestrial subsidy to aquatic ecosystems (e.g., Parmenter and Lamarra 1991;Subalusky et al. 2020). ...
... Animals may also indirectly promote calcification by acting as a nucleating site for CaCO 3 deposition or by hosting epibiotic communities, either on their bodies (e.g., turtles, Neil and Allen 1954; Fig. 2D) or their casings (e.g., caddisflies, Mooney et al. 2014;snails, Lukens et al. 2017), which may host microbes who influence CaCO 3 deposition via the mechanisms described above. Calcareous deposits have been documented on numerous aquatic macro invertebrates including dragonfly larvae, damselfly larvae, giant water bugs, caddisflies, riffle beetles, amphipods, fly larvae, stoneflies, water scorpions, snails, and aquatic mites (Krüper 1930;Edwards and Heywood 1960;Minckley 1963;Durrenfeldt 1978;Ruff and Maier 2000;Moody et al. 2016;Brown 1972). While several studies have considered the implications of epibiota to ecosystem processes (e.g., Mooney et al. 2014;Lukens et al. 2017), the impacts of animal-CaCO 3 deposits to P cycling via impacts on P-coprecipitation are currently unknown. ...
Phosphorus, an element essential to all life, is impacted by calcium carbonate (CaCO3) co‐precipitation and dissolution dynamics across aquatic ecosystems. Changes to climate, hydrology, and eutrophication, coupled with differences in terminology related to naming CaCO3‐producing ecosystems (i.e., chalk, carbonate, karst, travertine), point to the urgency and challenges in understanding this portion of the phosphorus cycle. Forms of CaCO3 vary across inland aquatic ecosystems, from “whiting events” in open waters to massive travertine or tufa formations to cemented layers on basal resources. And, across lakes, streams, and wetlands, periphyton mats and microbialites may form in photic regions. These biogenic carbonate structures beg the question: if aerobic photosynthesis promotes CaCO3 precipitation, but CaCO3 precipitation sequesters P, is this a challenge or opportunity for organisms? This review considers that question and others to better characterize this unexpectedly dynamic and influential portion of a major biogeochemical cycle.
... Furthermore, the response of the organism's body to preservatives is complex, and the rate at which these changes occur varies across taxonomic groups (Edwards et al. 2009). The differences among taxonomic groups can be caused by the specific biochemical composition of bodies, such as encrustation (Moody et al. 2016), sclerotization (Howmiller 1972) and chitinization (Von Schiller and Solimini 2005). These differences could be partly attributed to the body size when larger animals act differently from smaller animals (Stanford 1973). ...
... We assume that larger larvae were less affected in terms of mass losses during preservation because of their specific biochemical composition, such as heavier encrustation, sclerotization and chitinization, which may buffer them against the preservation effects better than smaller larvae which have a larger proportion of soft body tissues (Howmiller 1972;Moody et al. 2016;Von Schiller and Solimini 2005). ...
Biomass estimation offers insight into aquatic ecosystem processes and represents a powerful tool for measuring biomass in communities. However, the accuracy of this estimate depends considerably on the sample preservation method and biological traits of species. We quantified the effect of commonly used preservatives (70% ethanol, 4% formaldehyde, freezing), preservation time and initial body length on the estimation bias of body length, wet mass and dry mass in two mayfly species with dorsoventrally flattened (Rhithrogena carpatoalpina) and cylindrically elongated (Habroleptoides confusa) bodies. Freezing caused the largest relative bias in the length estimates (up to 18%). Both ethanol and freezing led to significant underestimation of wet mass of preserved animals (up to 26%). The most severe biases were observed in dry weights, where all preservation methods reduced body mass by up to 89%. Importantly, initial body mass influenced the bias caused by preservation, and the larger animals were less affected by mass losses. In contrast, larger individuals were subject to greater length reduction. Additionally, the length-mass relationship for R. carpatoalpina, based on fresh mass of living animals, was significantly different from relationships based on preserved animals. Overall, formaldehyde caused the least biased estimates of length and biomass in both examined species. This case study indicates that direct measurements of unpreserved individuals or length-mass equations based on fresh material are likely the best ways to avoid severe underestimation of biomass in aquatic insects. However, more studies covering a broader range of taxa are needed to reach general conclusions.
It is now widely accepted that Hexapoda emerged from Crustacea. Compared to the ubiquitous calcified exoskeleton in crustaceans, a mineralized cuticle in insects is extremely rare. Catecholamine-driven protein cross-links play a leading role in the sclerotization of insect cuticle. In this study, mineralization was discovered in the pupal cuticle of Bactrocera dorsalis (Diptera: Tephritidae), a common pest of fruit farms. We mainly profiled the features of mineralized pupal cuticles from B. dorsalis and its white mutant B. dorsaliswh and unmineralized cuticle from Musca domestica using high-resolution field emission scanning electron microscopy (SEM) and transmission electron microscopy (TEM) combined with structural analysis involving infrared (IR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and synchrotron X-ray absorption near-edge structure (XANES) spectroscopy. We also compared the thermodynamic and mechanical properties of different pupal cuticles. The results showed that the pupal cuticles of B. dorsalis contain a phase of stable amorphous calcium phosphate (ACP) with a high level of magnesium, which is mainly distributed in the exocuticle and assists in the formation of a graded, stiffened cuticle structure. Unexpectedly, this ACP possesses a very low Ca/P ratio and has a composition similar to that of CaHPO4·2H2O. The degree of mineralization in the pupal cuticle of B. dorsaliswh (approximately 22 wt%) is significantly greater than that of wild-type B. dorsalis (approximately 12 wt%), which indicates that there may be a connection between the biomineralization and tyrosine-mediated tanning pathways. These findings provide new evidence for the mineralization of the insect cuticle, which may shed new light on the evolutionary mechanism underlying the divergence of cuticle sclerotization between insects and crustaceans.
The absolute concentrations of nitrogen (N) and phosphorus (P) and their relative availabilities (N:P stoichiometry) can influence numerous ecological processes. In streams, N:P stoichiometry is influenced by different hydrologic and biogeochemical processes that also affect the downstream transport of these nutrients to receiving waters. Calcium carbonate (CaCO3) deposition, a widespread geochemical process in alkaline streams and other aquatic ecosystems, can lower phosphate concentrations and, potentially, decrease P availability relative to N availability. We evaluated the effects of CaCO3 deposition on stream water stoichiometry using a 3-year dataset of stream physicochemistry and several metrics of CaCO3 deposition across three streams in the Huachuca Mountains of southern Arizona, USA. CaCO3 deposition rates varied across and within streams, with benthic coverage of travertine as high as 70 % and deposition rates up to 8.3 μg Ca2+ L−1 m−1. Redundancy analysis revealed a strong, negative correlation between stream water phosphate concentrations and CaCO3 deposition rates, a relationship that also extended to total P concentrations, and a strong, positive correlation between inorganic N concentrations and CaCO3 deposition rates. Furthermore, we found a significant positive relationship between CaCO3 deposition rates and N:P ratios. These results support the role of coprecipitation of phosphate with CaCO3 deposition in reducing P supply. They also suggest that reduced concentrations of P in the water column may reduce biological N uptake, amplifying the stoichiometric signal of CaCO3 deposition.
Hydrology is a fundamental factor influencing ecosystem dynamics, life-history strategies, and diversity patterns in running-water habitats. However, it remains unclear how hydrology may structure the taxonomic and functional composition of communities, especially in systems with high spatiotemporal variability in flow. We examined invertebrate diversity from 7 desert streams in the Huachuca Mountains of southeastern Arizona, USA, that span a flow permanence continuum from highly intermittent to perennial. We examined the relative roles of flow permanence, habitat size, season, and microhabitat in determining taxonomic and functional structure (according to 7 species traits compiled for 234 taxa) of these communities. We predicted that both functional and taxonomic diversity would be positively related to flow permanence and negatively related to the duration and number of stream drying events. As predicted, increased flow permanence was associated with increased functional richness, functional evenness, and taxonomic richness. Conversely, drying events reduced functional diversity across all measured indices. We found a saturating relationship between functional richness and taxonomic richness, indicating functional redundancy in species-rich communities, which may promote resilience of ecosystem function to environmental variation. Our study adds further evidence that hydrology is a key determinant of aquatic invertebrate diversity, and that stream hydroperiod strongly influences both functional and taxonomic diversity in arid-land streams.
Since the nesting of the White-naped Swift (Streptoprocne semicollaris) was first described (Rowley and Orr 1962), this species has been thought to differ from other cypseloidine swifts in failing to build a nest structure. I studied nesting of White-naped Swifts and White-collared Swifts (Streptoprocne zonaris) at colonies where earlier nest descriptions were made. Based on a larger sample than that available to previous authors, I found the two swifts to differ little in nesting habits. Both species built or used existing nest structures on slanted substrates where eggs and young would otherwise have been at risk of rolling or falling, and both often laid eggs and reared young without a nest structure where the substrate was level or naturally enclosed. Frequency of use of risky vs. safe sites differed between colonies, reflecting apparent differences in the availability of safe sites. White-naped Swifts used nest structures on the same ledges where they laid eggs without nest structures 22 and 24 years earlier. Probably due to periodic flooding, these ledges apparently were less sandy in 1983 and 1985 than in 1961, and the swifts had responded to substrate changes by building nest structures in the absence of sandy oviposition sites. The supposedly unique nesting habits of S. semicollaris have been used as partial justification for a monotypic subgenus, Semicollum (Brooke 1970). Evidence presented here brings this rationale into question. Nests of both species, when built, were typical of the Cypseloidinae, except that semicollaris used more mud than is typical. Stereotyped behaviors used in nest building, when it does occur, are probably safer indicators of phylogeny than is mere frequency of nest building, which can differ between sites and change rapidly at a given site.
Top predator losses aff ect a wide array of ecological processes, and there is growing evidence that top predators are disproportionately vulnerable to environmental changes. Despite increasing recognition of the fundamental role that top predators play in structuring communities and ecosystems, it remains challenging to predict the consequences of predator extinctions in highly variable environments. Both biotic and abiotic drivers determine community structure, and manipulative experiments are necessary to disentangle the eff ects of predator loss from other co-occurring environmental changes. To explore the consistency of top predator eff ects in ecological communities that experience high local environmental variability, we experimentally removed top predators from arid-land stream pool mesocosms in southeastern Arizona, USA, and measured natural background environmental conditions. We inoculated mesocosms with aquatic invertebrates from local streams, removed the top predator Abedus herberti (Hemiptera: Belostomatidae) from half of the mesocosms as a treatment, and measured community divergence at the end of the summer dry season. We repeated the experiment in two consecutive years, which represented two very diff erent biotic and abiotic environments. We found that some of the eff ects of top predator removal were consistent despite signifi cant diff erences in environmental conditions, community composition, and colonist sources between years. As in other studies, top predator removal did not aff ect overall species richness or abundance in either year, and we observed inconsistent eff ects on community and trophic structure. However, top predator removal consistently aff ected large-bodied species (those in the top 1% of the community body size distribution) in both years, increasing the abundance of mesopredators and decreasing the abundance of detritivores, even though the identity of these species varied between years. Our fi ndings highlight the vulnerability of large taxa to top predator extirpations and suggest that the consistency of observed ecological patterns may be as important as their magnitude.
We developed a geochemical atlas of the Colorado River in Grand Canyon and in its tributary, the Little Colorado River, and used it to identify provenance and habitat use by Federally Endangered humpback chub, Gila cypha. Carbon stable isotope ratios (δ(13)C) discriminate best between the two rivers, but fine scale analysis in otoliths requires rare, expensive instrumentation. We therefore correlated other tracers (SrSr, Ba, and Se in ratio to Ca) to δ(13)C that are easier to quantify in otoliths with other microchemical techniques. Although the Little Colorado River's water chemistry varies with major storm events, at base flow or near base flow (conditions occurring 84% of the time in our study) its chemistry differs sufficiently from the mainstem to discriminate one from the other. Additionally, when fish egress from the natal Little Colorado River to the mainstem, they encounter cold water which causes the otolith daily growth increments to decrease in size markedly. Combining otolith growth increment analysis and microchemistry permitted estimation of size and age at first egress; size at first birthday was also estimated. Emigrants < 1 year old averaged 51.2 ± 4.4 (SE) days and 35.5 ± 3.6 mm at egress; older fish that had recruited to the population averaged 100 ± 7.8 days old and 51.0 ± 2.2 mm at egress, suggesting that larger, older emigrants recruit better. Back-calculated size at age 1 was unimodal and large (78.2 ± 3.3 mm) in Little Colorado caught fish but was bimodally distributed in Colorado mainstem caught fish (49.9 ± 3.6 and 79 ± 4.9 mm) suggesting that humpback chub can also rear in the mainstem. The study demonstrates the coupled usage of the two rivers by this fish and highlights the need to consider both rivers when making management decisions for humpback chub recovery.
Aquatic environments in the Madrean Sky Islands (MSI) consist of a matrix of perennial and intermittent stream segments, seasonal ponds, and human-built cattle trough habitats that support a diverse suite of aquatic macroinvertebrates. Although environmental conditions and aquatic communities are generally distinct in lotic and lentic habitats, MSI streams are characterized by isolated perennial pools for much of the year, and thus seasonally occur as lentic environments. In this study, we compared habitat characteristics and Coleoptera and Hemiptera assemblages of stream pools with those of true lentic habitats (seasonal ponds and cattle troughs) across the MSI. We identified 150 species across the 38 sites, and despite superficial similarities in habitat characteristics, seasonal ponds and stream pools in the MSI support distinct aquatic insect communities. Stream-exclusive species included many long-lived species with poor dispersal abilities, while pond-exclusive species tended to have rapid development times and strong dispersal abilities. We suggest that, in addition to perennial streams, seasonal aquatic habitats should also be a focus of conservation planning in the MSI.
Natural disturbance regimes—cycles of fire, flood, drought or other events—range from highly predictable (disturbances occur regularly in time or in concert with a proximate cue) to highly unpredictable. While theory predicts how populations should evolve under different degrees of disturbance predictability, there is little empirical evidence of how this occurs in nature. Here, we demonstrate local adaptation in populations of an aquatic insect occupying sites along a natural gradient of disturbance predictability, where predictability was defined as the ability of a proximate cue (rainfall) to signal a disturbance (flash flood). In controlled behavioural experiments, populations from predictable environments responded to rainfall events by quickly exiting the water and moving sufficiently far from the stream to escape flash floods. By contrast, populations from less predictable environments had longer response times and lower response rates, reflecting the uncertainty inherent to these environments. Analysis with signal detection theory showed that for 13 out of 15 populations, observed response times were an optimal compromise between the competing risks of abandoning versus remaining in the stream, mediated by the rainfall–flood correlation of the local environment. Our study provides the first demonstration that populations can evolve in response to differences in disturbance predictability, and provides evidence that populations can adapt to among-stream differences in flow regime.
Geochemical, mineralogical and microbiological data from four freshwater streams in central region of Mexico indicate the importance of Blennothrix ganeshii mats (Cyanobacteria, Oscillatoriales) in promoting the formation of calcium carbonate crystals. The streams were characterized by alkaline waters and relative physicochemical stability during three seasons (cold dry, warm dry and warm rainy). Calcification took the form of a thick, dense layer of calcium carbonate crystals surrounding the extracellular polymeric substances produced by B. ganeshii filaments, giving an appearance of micritic tubes (structures formed by crystallization in the spaces between filaments) along the sheath surfaces. The precipitate was analyzed using X-ray diffraction and energy dispersal X-ray spectrometry, and the calcite crystal habit was determined. The photosynthetic activity of cyanobacterial growth and the presence of abundant extracellular polymeric substances and epiphytic species promote the absorption of ions and mineral nucleation on the surface of the sediment and contribute to the formation of travertine in tropical regions.
We collected an undescribed hydropsychid caddisfly, Smicridea (Smicridea) travertinera ,n . sp., from 2 sites in Venezuela. One of the sites, Quebrada El Charo, flowed over extensive calcareous formations of travertine, which were covered with retreats and capture nets of the new species. Smicridea travertinera was the most abundant aquatic insect colonizing travertine. We describe the adult male, the retreat and net, and gut contents. The retreat consisted of an aperture in the travertine with a capture net. Retreat-making behavior appears to cause both the biogenesis and erosion of the travertine formations.
Microbes are important in stream ecosystem processes and ubiquitous in stream environments, but limitations of study techniques have left most of these microbial communities poorly described. In stream ecosystems, fungal and bacterial communities play critical roles in leaf decomposition and release energy and nutrients to higher trophic levels of the food web. Our research examined microbial communities in Fossil Creek, Arizona, USA, to elucidate effects of litter quality and abiotic habitat characteristics on early microbial colonizers of leaves. High- and low-quality leaf litter was placed in the creek at 5 study sites with heterogeneous environmental conditions (including differing stream morphology, water flow, water chemistry, and travertine deposition). Microbial assemblages that colonized the decomposing leaves were characterized using terminal-restriction fragment length polymorphism analysis and clone library comparisons. Our study revealed differences in microbial community structure along environmental gradients and, to some extent, between high- and low-quality litter in Fossil Creek. Leaf decomposition rates were strongly influenced by both litter quality and abiotic site characteristics, but microbial communities were more strongly influenced by site than by litter quality. Bacterial and fungal communities differed with incubation times: bacterial diversity increased between 2-d and 8- to 9-d incubations, whereas fungal diversity decreased. Fungal community diversity was negatively correlated with decomposition rates after incubation in the creek for 2 d when the community still included nonaquatic fungi, but this relationship did not exist after longer incubation. Bacterial community diversity was not related to litter quality or decomposition rates.
Feeding preference experiments were conducted to determine the feeding habits of Abedus herberti (Heteroptera, Belostomatidae) and Thermonectus marmoratus (Coleoptera, Dytiscidae), two large insects in Sycamore Creek, an intermittent Sonoran desert stream, Arizona, U.S.A. Numbers of live versus dead prey consumed were tested between and across three prey sizes. Five prey species were offered simultaneously (5 live and 5 dead specimens) in each size class. We found that A. herberti preferred live prey of small and medium size, but it chose mainly dead prey in the large size class. These results fitted the model of size-selective predation (Zaret, 1980). Size dependent predators selected prey of increased size, according to their visibility, but only up to where difficulty in handling and probability of escape affect successful consumption. Snails were the most preferred prey of A. herberti. By contrast, T. marmoratus consumed only dead prey of all sizes, but it preferred soft organisms with thin cuticle, such as immature larvae of some mayflies, beetles, dragonflies or fishes.
In disturbance ecology there is a tension between ecological and evolutionary viewpoints, because while disturbances often cause mortality in populations (an ecological effect), populations may also evolve mechanisms that ameliorate mortality risk (an evo-lutionary effect). Flash floods cause high mortality in the juvenile aquatic stage of desert stream insects, but these ecological effects may be mitigated by the evolution of life-history strategies that allow the terrestrial adult stage to avoid floods. Life-history theory predicts that, to balance trade-offs between juvenile growth and mortality risk from floods, (1) most individuals should emerge before the peak of the flood season, (2) optimal body size at emergence should decline as flood probability increases, and (3) a second decline in body size at emergence should occur as the reproductive season ends. These predictions were tested with data on body mass at and timing of emergence of the caddisfly Phylloicus aeneus measured in three montane Chihuahuan Desert (Arizona, USA) streams over two years. P. aeneus that had not reached the adult stage were eliminated from site-years that experienced flash floods, suggesting that timing of emergence is an important fitness component. On average 86% of emergence occurred before the long-term (100 yr) mean arrival date of the first seasonal flood, supporting prediction 1. The presence of two consecutive declines in body mass at emergence in most site-years was congruent with predictions 2 and 3. To test whether the two declines were associated with increasing flood probability and end of the reproductive season, respectively, maximum-likelihood methods were used to compare five body-size models: a null model that contains no parameters related to flood regime or reproductive season, a seasonal model that incorporates a reproductive time constraint, and three disturbance models that incorporate both reproductive time constraints and flood dynamics. The disturbance models outperformed the other models, suggesting that at least some of the body-mass pattern was influenced by flood dynamics. The timing of the first flood of the season was the most important determinant of observed emergence patterns. Overall, this study demonstrates that aquatic insects can compensate for flash floods by using state-dependent emergence strategies that are synchronized with long-term flood dynamics.
Leaf retention is important in transferring energy from riparian trees to stream food webs. Retention increases with geomorphic
complexity such as substrate coarseness, sinuosity, and the presence of debris dams. High discharge can reduce retention,
particularly when streams lack physical trapping features. Travertine formations, caused by calcium carbonate deposition,
can alter stream morphology. To date, however, we know of no study testing the effect of travertine on leaf retention. This
study capitalized on a river restoration project in Fossil Creek, Arizona, where water was returned to the channel after a
century of diversion. We examined how the fixed factors Flow (before and after restoration) and Morphology (travertine and
riffle-pool sites) affected leaf retention. Leaf retention was higher in sites where travertine forms barriers across the
river, relative to sites with riffle-pool morphology. Most leaves retained in travertine reaches were concentrated at the
bottom of pools formed between dams. Although flow restoration did not alter retention rates across all sites, it diminished
them at travertine sites, indicating an interaction between stream flow and morphology. We conclude that stream complexity
and leaf retention are enhanced by travertine deposition but that high discharge can reduce the retentive capacity of in-stream
structures.
Mayfly instar determination methods have been examined to determine their accuracy and usefulness. The Janetschek and Cassie methods are shown not to be an improvement on the simple frequencies from which they are calculated. The Palmen body method suffers from great technical difficulties due to the body’s structure and small size. The prospect of associating the number of molts with life history and environmental data is discussed.
Aquatic insect larvae play an important role in travertine deposition at Louie Creek, a small, karst spring fed stream in northwest Queensland, Australia. The most conspicuous larvae are the caddis-flies, of which the genus Cheumatopsyche is the most abundant. These larvae build retreats consisting of travertine and organic fragments harvested from the stream bed, Silken nets constructed across the retreat opening act as food traps and as important substrata for calcium carbonate precipitation. The nets and retreats together form distinctive microtopographic features that not only disturb hydrodynamics, and thus probably stream chemistry, but also contribute significantly to travertine deposition rates under a range of hydrochemical conditions.
In situ measurements were performed on the travertine-encrusted mosses Cratoneuron commutatum var. commutatum and Eucladium verticillatum to obtain estimates of calcium carbonate deposition through photosynthesis, evaporation and carbon dioxide evasion. It was estimated that for both species, between 6 and 12% of the carbonate was deposited through photosynthesis, 10-20% through evaporation and the remaining 70-80% through gas evasion.
Phenomena affecting population regulation of the aeshnid dragonfly, Oplonaeschna armata Hagen, were studied from 1962 through 1965. Definitive features of the habitat occurring in the southwestern mountain streams of the U. S. are described. Adult emergence and flying season are related to the annual air and water temperature cycles. Emergence occurs over approximately 10 days in mid to late June. Adult maturation requires 12 to 20 days and the total flight season is approximately one month. Egg development is approximately three weeks between oviposition and hatching. Total larval growth requires three years and some mechanism synchronizes growth as emergence nears. The sex ratio in larvae moves in second-year-class larvae from near equality to higher female values at emergence. The three year-classes of larvae display different habitat selection behavior based on variations along the stream substrate.
Study on calcite precipitation has major implications for both the hydrochemical evolutions of river systems and the global carbon cycle. The precipitation of calcite generally requires the water to be 5–10 times supersaturated with respect to calcite, which is usually achieved by the removal of CO2. Formation of waterfall tufa has been often simply described as the result of water turbulence in fast-flowing water. In this paper, the formation mechanisms of waterfall tufa are discussed and a series of laboratory experiments are designed to simulate the hydrological conditions at waterfall sites. The influences of the air–water interface, the water flow velocity and the solid–water interface on CO2 outgassing and calcite precipitation are compared and evaluated quantitatively. The results show that the principal cause of waterfall tufa formation is the enhanced inorganic carbon dioxide outgassing resulted from the sudden hydrological changes occurring at waterfall sites, rather than organisms, evaporation or the solid–water interface. The air–water interface area and the water flow velocity are greatly increased at waterfall sites as a result of the “aeration effect”, “low pressure effect” and “jet-flow effect”, which greatly accelerate CO2 outgassing. Inorganic CO2 outgassing drives the waters to become highly supersaturated with respect to calcite and, consequently, results in much calcite deposition. The solid–water interface is less important as the air–water interface in affecting calcite precipitation at waterfall sites. Field measurements showed that conductivity, Ca2+ and HCO3− concentrations along Tianhe Creek and Hot Creek decrease downstream while pH rises. Field observations also showed that tufa deposition occurred mainly at waterfall sites.
1. Temporary streams comprise a large proportion of the total length of most stream networks, and the great majority of arid‐land stream networks, so it is important to understand their contribution to biotic diversity at both local and landscape scales.
2. In late winter 2010, we sampled invertebrate assemblages in 12 reaches of a large arid‐land stream network (including perennial and intermittent headwaters, intermittent middle reaches and perennial rivers) in south‐east Arizona, U.S.A. Intermittent reaches had then been flowing for c. 60 days, following a dry period of more than 450 days. We sampled a subset of the perennial study reaches three more times between 2009 and 2011. Since intermittent reaches were dry during these additional sampling periods, we used assemblage data from two other intermittent streams in the study network (sampled in 2004–05 and 2010) to explore interannual variability in intermittent stream assemblage composition.
3. Invertebrate richness was lowest in intermittent reaches, despite their often being connected to species‐rich perennial reaches. The assemblages of these intermittent reaches were not simply a subset of the species in perennial streams, but rather were dominated by a suite of stoneflies, blackflies and midges with adaptations to intermittency (e.g. egg and/or larval diapause). On average, 86% of individuals in these samples were specialists or exclusive to intermittent streams. Predators were 7–14 times more abundant in perennial than in intermittent reaches.
4. Despite being separated by long distances (12–25 km) and having very different physical characteristics, the assemblages of perennial headwaters and rivers were more similar to one another than to intervening intermittent reaches, emphasising the prime importance of local hydrology in this system.
5. The duration and recurrence intervals of dry periods, and the relative importance of dispersal from perennial refuges, probably influence the magnitude of biological differences between neighbouring perennial and temporary streams. Although perennial headwaters supported the highest diversity of invertebrates, intermittent reaches supported a number of unique or locally rare species and as such contribute to regional species diversity and should be included in conservation planning.
1. Ecological communities can be relatively stable for long periods of time, and then, often as a result of disturbance, transition rapidly to a novel state. When communities fail to recover to pre-disturbance configurations, they are said to have experienced a regime shift or to be in an alternative stable state.
2. In this 8-year study, we quantified the effects of complete water loss and subsequent altered disturbance regime on aquatic insect communities inhabiting a formerly perennial desert stream. We monitored two study pools seasonally for 4 years before and 4 years after the transition from perennial to intermittent flow to evaluate pre-drying community dynamics and post-drying recovery trajectories.
3. Mean species richness was not affected by the transition to intermittent flow, though seasonal patterns of richness did change. Sample densities were much higher in post-drying samples.
4. The stream pool communities underwent a catastrophic regime shift after transition to intermittent flow, moving to an alternative stable state with novel seasonal trajectories, and did not recover to pre-drying configurations after 4 years. Six invertebrate species were extirpated by the initial drying event, while other species were as much as 40 times more abundant in post-drying samples. In general, large-bodied top predators were extirpated from the system and replaced with high abundances of smaller-bodied mesopredators.
5. Our results suggest that the loss of perennial flow caused by intensified droughts and water withdrawals could lead to significant changes in community structure and species composition at local and regional scales.
Dispersal is an essential process in metapopulation and metacommunity dynamics. Most studies of aquatic invertebrate dispersal in streams have focused on in-stream drift of larvae. However, understanding aerial dispersal is important for predicting community assembly in isolated habitats after disturbance or stream restoration. We used artificial pools placed at 3 distances (5, 75, and 250 m) from 1 perennial and 1 ephemeral arid-land stream to examine aerial-dispersal dynamics of aquatic invertebrates over a 6-wk period in summer 2009. We also conducted a 2-wk experiment to examine the relationship between daily rainfall and disperser abundance at the perennial site. Sixty-six aquatic invertebrate taxa (including many Coleoptera and Diptera and fewer Hemiptera, Ephemeroptera, Trichoptera, and noninsect taxa) colonized the artificial pools. They represented V, of taxa documented from neighboring perennial streams. Abundance and species richness declined with distance away from both streams. This result suggests that ephemeral stream channels may serve as important aerial dispersal corridors for aquatic invertebrates even when no surface water is present. Mean species richness tripled after 58 mm of rain during the 4th wk of the experiment. Data from the 2-wk experiment highlighted the role of rainfall as a dispersal cue in this system. Amount of daily rainfall explained 48 to 77% of the variation in disperser abundance at 5, 75, and 250 m from the perennial site. We used spatiotemporal dispersal patterns observed in our study to identify 5 modes of aerial dispersal among 56 taxa: 1) widespread common, 2) widespread haphazard, 3) range-restricted, 4) cue-limited, and 5) infrequent. Classification of specific aerial-dispersal modes provides a conceptual framework for modeling spatially explicit community responses to disturbance, stream restoration, and climate-change-induced habitat contraction or expansion.
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Le Zitelle hot springs contain high concentrations of dissolved Ca and CO2 and precipitate copious quantities of aragonite and calcite as travertine. A study of precipitation rates in the upper section of the stream was undertaken using marble tablets. This showed that: (1) precipitation rate increased with distance from the spring over the section studied; (2) the rate was positively correlated with flow, agreeing with previous experimental and theoretical studies; (3) precipitation rates during the day and night did not differ statistically. The last finding demonstrated a negligible effect of photosynthesis on travertine formation and was supported by further precipitation rate studies undertaken in clear and blackened tubes. This conflicts with previous work that suggested an important role for microbial photosynthesis in travertine deposition at Le Zitelle. The microbial flora consisted mainly of cyanobacteria (Spirulina) and photosynthetic bacteria, with smaller quantities of diatoms. The biomass in most of the travertine was extremely low and often endolithic. Carbon fixation rates were also low. A mass-balance calculation of carbon flow showed that of 100 units of dissolved carbon entering the stream section investigated, 51 units were lost to the atmosphere as CO2, 0-9 units were deposited as travertine, 0.09 units were fixed by photosynthesis and 48 units remained in the stream water. We conclude that most of the Zitelle travertine is formed abiotically, casting doubt on the supposed biotic origin of travertine at this and other Italian sites.
U-Th disequilibrium dates and stable isotope analyses of travertine deposits at Soda Dam, New Mexico, have been used to determine the age and to document the evolution of the Valles caldera hydrothermal system. The similar ages between caldera formation and the onset of large-scale hydrothermal circulation and travertine deposition on pre-Bandelier Tuff rocks imply that incision rates by the Jemez River in Bandelier Tuff were relatively rapid. As much as 400m of tuff were cut by the ancestral Jemez River in 105 yr or less.-from Authors
Ninety-nine taxa of aquatic insects and a total 104 macroinvertebrate taxa were collected in Sycamore Creek, Arizona, from July 1977 to November 1979 The fauna is primarily composed of organisms restricted to the American Southwest, although many widespread Nearctic taxa are also present. Life histories of 17 taxa were examined with emphasis on total developmental time (egg to adult), reproductive period and dormancy Ephemeroptera, small Diptera and the corixid Graptocorixa serrulata developed rapidly (1-3 weeks) and reproduced continuously. Aquatic beetles (Dytiscidae and Hydrophilidae) developed in 4-8 weeks and reproduced only in spring and after summer rains. Two Trichoptera species required 6-7 weeks for development and reproduced continuously Degree-day developmental rates (ca. 1200) were similar for some desert and temperate species. Dormant stages were restricted to stoneflies (egg diapause) and tabanids (larval diapause). Drought and flooding markedly influenced life histories. Adaptations to drought are habitat selection by ovipositing adults and rapid development. Adaptations to floods are behavioral avoidance, rapid development and seasonal reproduction. Floods also contribute to the rarity of dormancy, thus aerial adults become the life stage resistant to disturbance. Floods, which do not occur in temporary lentic systems, are an important selective pressure in temporary lotic systems.
Aquatic insect larvae play an important role in travertine deposition at Louie Creek, a small, karst spring-fed stream in northwest Queensland, Australia. The most conspicuous larvae are the caddis-flies, of which the genus Cheumatopsyche is the most abundant. These larvae build retreats consisting of travertine and organic fragments harvested from the stream bed. Silken nets constructed across the retreat opening act as food traps and as important substrata for calcium carbonate precipitation. The nets and retreats together form distinctive microtopographic features that not only disturb hydrodynamics, and thus probably stream chemistry, but also contribute significantly to travertine deposition rates under a range of hydrochemical conditions.
The principal goal of the present study is to determine the nature and environments of chemical sedimentation and diagenesis in the stratigraphic unit containing the large Mg-clay deposits. Toward this goal, the stratigraphy of the Pliocene-Pleistocene deposits was worked out, and the lithofacies and their depositional environments were established. The mineral composition of the different lithofacies was determined, and authigenic minerals were correlated with depositional environments. The paleohydrology was inferred from the distribution, composition, and morphology of chemically deposited sediments. Isotopic data from authigenic minerals in the different facies provided a basis for estimating the relative degree of evaporative concentration for water in the different environments.
Previous methods of determining instar number in mayflies have been criticized as inaccurate and misleading. A new method, based on predictable size-dependent growth ratios calculated from growth experiment data, is described. A growth curve is also estimated using these growth ratios and temperature-dependent moult intervals.
• I. A brief survey of the British members of the genus Ecdyonurus is given.
• II. A special study is made of the Ecdyonurus population of the River Alyn, Denbighshire.
• III. An examination of the presumed specific differences of the nymphs and imagines of E. venosus (Fab.), E. venosus var. queesitor, E. longicauda, and E. forcipula, together with a study of the Alyn Ecdyonurus population, lead to grave doubts concerning the recognition of these flies as true species. Two suggestions are made–either E. venosus (Fab.), the Alyn venosus, E. longicauda, and E. forcipula are local varieties, races, or seasonal forms which will in future be found to grade into one another, or the Alyn Ecdyonurus population is incompletely separated into the species described from elsewhere as distinct.
• IV. The author regards the Alyn E. venosus as a variety of E. venosus (Fab.) which comes within the possible range of variation in this species. Until the true status of the various forms has been settled, the Alyn E. venosus is referred to throughout as E. venosus to distinguish it from E. venosus (Fab.).
• V. The life-history of the Alyn form of E. venosus–pairing, oviposition, and the development from the egg to the imago–has been described. There are at least two broods a year.
• VI. The external features, habitat, and habits of the imagines and nymphs of this form are described. The mode of feeding of the nymphs is also described.
• VII. A study of weekly samples of the nymphal population during the summer and monthly samples during the winter shows a marked seasonal difference in the rate of nymphal growth and the presence of two definite broods of flies a year. The first swarms appear in June, the second from July to October. The early summer eggs hatch and emerge as flies within two months, whereas the autumn ones grow much more slowly and emerge the following June.
• VIII. An analysis of the population samples collected between May 1937 and May 1938 is given.
We studied the lime deposits on Gammarus fossarum from a tufa brook in Southern Germany. Between 20 and 75% of the gammarids collected carried calcium carbonate deposits at the dorsal part of the pleon segments. Average weight of deposits ranged between 0.6 mg on small and 1.7 mg on large specimens and constituted 60–20% of specimens' dry weights.
Predator‐prey experiments with salamander larvae and gammarids showed that significantly fewer prey with deposits were eaten than without deposits and that the differences in predation risks between prey with vs. prey without deposits were greatest in small and medium sized specimens.
Lime deposits changed the feel or taste and the activity patterns of gammarids. Gammarids with deposits were rejected significantly more often by the predators than gammarids without deposits. Medium sized specimens with deposits, which suffered a great predation risk, were significantly less active than specimens of the same size category without deposits.
Lime deposits did not increase conspicousness or decrease escape ability of prey. Prey with deposits were attacked by predators with the same frequency and captured with the same success as prey without deposits.
Lime deposits may afford effective protection from salamander predation in some natural habitats. Predation impact on gammarids by salamander larvae may be low, however, because larval density was very low in most places (< 1 m ‐2 ) and because larvae are only present for a limited time until they start metamorphosis.
1. Breakdown of four leaf species (Platanus orientalis, Populus nigra, Salix atrocinerea, Rubus ulmifolius) was studied in a Mediterranean second-order stream characterised by abundant travertine precipitation, a history of fire in its catchment, and a recently revegetated alluvial corridor.
2. Compared to breakdown rates reported in the literature for congeneric species, breakdown of the four species was slow (k = 0.0024–0.0069 day−1 for the tree species, and 0.0103 and 0.0111 day−1 for Rubus), in spite of high water temperatures, indicating that the travertine layer that quickly covered submerged leaves impeded decomposer activity and physical fragmentation losses.
3. Breakdown rates nevertheless differed between leaf species in a predictable manner, suggesting that the observed mass loss was largely due to biological processes.
4. The observed tendency towards increasing leaf nitrogen and phosphorus concentrations during breakdown suggests that microorganisms were actively involved in leaf breakdown; however, this interpretation must be viewed with caution because of potentially confounding effects by nutrients contained in the travertine layer.
5. Leaf breakdown of the three indigenous species was faster than that of the exotic species P. orientalis. Due to the recalcitrance of its leaves, the frequent use of Platanus in revegetation schemes following the destruction of indigenous vegetation by fire, exacerbates the negative effect of travertine precipitation on leaf breakdown and, by extension, energy flow in Mediterranean karst streams.
Mature larvae of Ecdyonurus dispar were collected from Ennerdale Water and Windermere (English Lake District) and reared to adult males and females in the laboratory. The females were then fertilized artificially and their progeny were kept at constant temperatures (range 4.2–20.2°C). Larvae collected directly from the two lakes were also reared under the same conditions.
The maximum number of instars from egg to subimago was 25, the average body length increment (mm) per moult was proportionately constant at c. 15% and Dyar's rule was applicable. The interval between moults decreased with increasing temperature and the relationship between the two variables within the temperature range 4.2–19.8°C was described by a power law. Larval growth was exponential and variations in mean specific growth rate (range 0.23–5.23% length day−1) were related to mean temperature which was the major factor affecting growth in the laboratory. A few experiments were also performed in the lake to test the adequacy of the estimated values for larval growth at different temperatures in the laboratory. There was agreement between the estimates and the actual growth rates in the lake. Therefore, the regression equations obtained from the laboratory experiments are probably applicable to larval growth in the field.
Values for daily production in the laboratory ranged from 0.53 to 9.33 mg dry wt day−1 m−2. The lowest value was obtained at 8.9°C and the highest at 20°C.
Information on different life cycles of E. dispar is briefly reviewed and it is concluded that E. dispar from the lakes can only achieve one generation per year.
We studied the effect of carbonate depositions covering stone surfaces on the growth of larvae and the biomass of subsequent adults of the grazing limnephilid caddisfly Melampophylax mucoreus(Hagen, 1861) in a laboratory rearing experiment. M. mucoreus is mainly distributed in karst streams characterized by calcium carbonate precipitations (tufa). We reared larvae of M. mucoreus on stones covered by calcareous tufa crusts as well as on stones from which these crusts were experimentally removed to assess the influence on larval growth and the subsequent adult biomass. The rough surface of the covered stones provided a higher complexity of micro-habitats and supported algal growth compared to the smooth surface of stones without crusts. Larvae of M. mucoreus profited from the enhanced algal biofilm growth on the calcium carbonate precipitation indicated by faster larval growth and higher subsequent adult biomass. Biomass increase of larvae reared on stones covered by tufa crusts exhibited a faster biomass development (0.09 ± 0.015 mg/d) compared to the larvae reared on stones without crusts (0.06 ± 0.002 mg/d). Adult males (5.13 ± 0.25 mg) and females (7.64 ± 0.63 mg) were significantly heavier in the treatment with stones covered by tufa than their conspecifics from the treatment with uncovered stones (males: 4.26 ± 0.25 mg, p = 0.047; females: 4.96 ± 0.47 mg, p = 0.001). Additionally, males from the treatment with crust covered stones emerged significantly earlier (p = 0.003) than the males from the other treatment, whereas no significant difference was found for females. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
This study investigated ecological factors affecting species distribution and travertine deposition in an Italian site of the "Natura 2000" network. Vegetation plots were located along four streams in a prealpine valley (Valganna, Lombardy, Northern Italy). Five meso-scale variables (e.g. altitude, aspect and slope) and ten micro-scale variables (e.g. shading, plot position and soil accumulation) were recorded for each plot; in addition, travertine deposition was evaluated. The main floristic gradients extracted by DCA were related to topography, vegetation type and water availability. The occurrence of species groups in relation to environmental variables was analysed using Poisson regression. Amongst 15 environmental variables and six species, the variables showing the greatest relationship to travertine deposition were the length of the waterless period and substrate slope. Photosynthetic organisms had a minor role in travertine formation, mostly restricted to substrates with a shallow slope. The maintenance of a sufficient water flow is the most effective action in conservation plans for petrifying springs.
Travertine deposition occurs in streams worldwide but its effects on stream communities are poorly understood. I sampled benthic
macroinvertebrates, periphyton, and reach-scale environmental variables in coastal streams in Big Sur, central California,
USA, to determine the specific effects of travertine that occurred at some sites as well as to provide a broader assessment
of community–habitat relationships. Total density and biomass of macroinvertebrates varied 6- and 9-fold across sites, respectively,
and chlorophyll a concentrations varied 10-fold, but invertebrate and periphyton abundances were not correlated. Baetis tricaudatus (Ephemeroptera), Simuliidae (Diptera), and Chironomidae (Diptera) dominated macroinvertebrate communities across all sites,
although differences in the relative abundances of these and other taxa produced moderate variation in community structure
among sites (Bray-Curtis similarity coefficients of 47–84). Variation in community structure was related to a number of habitat
features, notably travertine but also including variables reflecting channel morphology, flow, substrate size, and riparian
tree type. Median density and biomass of macroinvertebrates were more than twice as high at sites without travertine than
sites with travertine. Taxa richness also was higher at sites without travertine, and community structure differed moderately
between sites with and without travertine, although there were no particular assemblages associated with either group. Non-metric
multidimensional scaling (MDS) and cluster analysis of similarities in community structure appeared to separate sites with
either travertine or high fines from sites without those conditions. These results demonstrate that travertine can have strong
effects on stream communities, and additional studies are needed to identify the full range of effects on ecosystems and to
evaluate the potential consequences of travertine for conservation efforts such as biomonitoring programs and threatened species
management.
Travertine deposits of calcium carbonate can dominate channel geomorphology in streams where travertine deposition creates a distinct morphology characterized by travertine terraces, steep waterfalls, and large pools. Algae and microorganisms can facilitate travertine deposition, but how travertine affects material and energy flow in stream ecosystems is less well understood. Nearly a century of flow diversion for hydropower production has decimated the natural travertine formations in Fossil Creek, Arizona. The dam will be decommissioned in 2005. Returning carbonate-rich spring water to the natural stream channel should promote travertine deposition. How will the recovery of travertine affect the ecology of the creek? To address this question, we compared primary production, decomposition, and the abundance and diversity of invertebrates and fish in travertine and riffle/run reaches of Fossil Creek, Arizona. We found that travertine supports higher primary productivity, faster rates of leaf litter decomposition, and higher species richness of the native invertebrate assemblage. Observations from snorkeling in the stream indicate that fish density is also higher in the travertine reach. We postulate that restoring travertine to Fossil Creek will increase stream productivity, rates of litter processing, and energy flow up the food web. Higher aquatic productivity could fundamentally shift the nature of the stream from a sink to a source of energy for the surrounding terrestrial landscape.
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