Temporary Aquatic Habitats Research Articles

Large branchiopods (Anostraca, Notostraca, Laevicaudata, Spinicaudata) from the semi-arid regions of western India

Abstract Large branchiopod crustaceans are flagship species of temporary water bodies, especially in arid and semi-arid regions. Less information is available about the large branchiopods of tropical Asia compared to other parts of the world such as the Americas. To reduce this disparity, we surveyed large branchiopods from the semi-arid region of Maharashtra state, India. Sampling at 29 sites over four years revealed nine species representing four orders. This is the highest diversity ever reported from a single regional study in India. Anostracans were the most commonly occurring group, whereas the spinicaudatans Leptestheria cf. nobilisSars, 1900, L. jaisalmerensisTiwari, 1962, and Eulimnadia michaeliNayar & Nair, 1968 were very rare. Leptestheria jaisalmerensis had been known previously only from its type locality nearly 1,200 km north of our study region. Congeneric assemblages of the anostracans Streptocephalus dichotomusBaird, 1860 + S. simplexGurney, 1906 and the spinicaudatans Leptestheria cf. nobilis + L. jaisalmerensis were collected. Temporary aquatic habitats are threatened due to adverse anthropogenic activities, especially in developing countries like India. The endemic species of large branchiopods in the Indian subcontinent should be red-listed, as is done elsewhere.

Occurrence of tardigrades and morphometric and chemical conditions in rock pools by the Baltic Sea

Rock pools are eroded depressions in bedrock providing temporary aquatic habitats with varying morphometric and chemical conditions. Tardigrades have adapted to many habitats with varying and extreme abiotic conditions, including desiccation, but their occurrence in rock pools have rarely been investigated. This study investigated the occurrence of tardigrades and the morphometric and chemical conditions in rock pools by the Baltic Sea in southeast Sweden. Samples of benthic material were collected from rock pools at three sites near the town Karlshamn together with measurements of pool size, pH, temperature, salinity, and dissolved oxygen of the water. Tardigrades occurred in about one fifth of the rock pools and included five eutardigrade genera. Also rotifers and nematodes were observed in the samples. The morphometric and chemical variables varied both within and among the three sites but with few differences between rock pools with or without tardigrades. However, rock pools with tardigrades tended to be overall shallower than pools without tardigrades, indicating that more desiccating-prone rock pools may be more favourable habitats for tardigrades. The study shows that tardigrades are part of the micro-invertebrate fauna in rock pools and this habitat deserves more investigations into the occurrence of this animal group.

Heterocypris incongruens maintains an egg bank in stormwater habitats and influences the development of larval mosquito, Culex restuans.

Dormant propagules can provide a rapid colonization source for temporary aquatic habitats and set the trajectory for community dynamics, yet the egg banks of stormwater management systems have received little attention. We asked which species hatched from the sediment of drainage ditches in Champaign County, IL, and found bdelloid rotifers and ostracods (Heterocypris incongruens) to be the most common taxa. These sites also are colonized by mosquitoes, and we established laboratory experiments to examine interspecific interactions between common co-occurring taxa. Culex restuans larvae were reared in the presence or absence of H. incongruens at two intra- and interspecific densities (20 or 40 total individuals) and their survivorship to adulthood, development time to adulthood, adult body size, and sex ratio were determined. Survival for Cx. restuans was significantly lower at high larval density than at low larval density in both treatments. Culex restuans larvae reared in the presence of H. incongruens had a shorter development time to adulthood and emerged as larger adults compared to those reared in the absence of H. incongruens. The sex ratios in the H. incongruens treatments were female-biased whereas those in the Culex-only treatments were male-biased. These differences may have epidemiological implications, as only female mosquitoes serve as disease vectors. Our results emphasize the importance of understanding interspecific interactions in influencing larval mosquito development traits.

Inability of yellow‐bellied toad to accelerate metamorphosis in desiccation conditions

AbstractMany amphibian species inhabit temporary aquatic habitats for reproduction to maximize larval growth under favorable conditions, but accelerate developmental rate to rapidly undergo metamorphosis under stress conditions when high desiccation risk exists. Desiccation affects different aspects of amphibian biology such as developmental rate, body size and mass, and growth rate. We studied the responses of yellow‐bellied toad (Bombina variegata) to different water levels (constant high, decreasing water level, and constant low water level) in the laboratory using individuals collected from natural ponds. To assess the effects of experimental pond drying, we investigated the effects on life‐history and morphological traits at metamorphosis as well as carry‐over effects on post‐metamorphic traits and locomotor performances. We found that B. variegata cannot accelerate developmental rate in response to pond drying. The metamorphs from decreasing and constant low water levels had similar size, mass, growth rate and body condition indices at metamorphosis, and all these traits were lower than in the constant high water level treatment. These changes in life‐history traits at metamorphosis did not affect tail shape although they had carry‐over effects on life‐history and morphological traits after metamorphosis. Post‐metamorphic individuals reared in desiccation treatments had similar but smaller lengths of femur and tibiofibula, but these changes did not have negative consequences on jumping performances. We show that responsiveness to pond drying of B. variegata is probably associated with maximum growth rate in favorable conditions and inability to increase growth rate as well as developmental rate in desiccation conditions. This resulted in prolonged developmental time to reach the minimum size and mass for metamorphosis.

Savanna vegetation increase triggers freshwater community shifts.

Tropical savannas are globally extensive and ecologically invaluable ecosystems. As most ecosystems however, they are subject to serious anthropogenic stress. Defaunation, and especially the loss of large mammals, is pervasive in tropical savannas and known to trigger wide-ranging ecological effects, from vegetation changes to the loss of ecosystem function. Despite what is currently known about the terrestrial consequences of defaunation, and the potential cross-ecosystem influence of large mammals, virtually no research has investigated associated effects on small adjacent water bodies. This research gap persists because (1) tropical savannas have been historically neglected, (2) the ecological value of small water bodies (e.g. ponds) is only recently being recognized, and (3) empirical baseline data are often lacking. In this paper, we compared a rare pre-change dataset with newly collected data on 213 freshwater assemblages, to investigate community structure and composition before and after a major defaunation event. Our research focused on a diverse species assemblage of amphibian larvae (i.e. tadpoles) in temporary savanna ponds. We found that pond vegetation cover increased from 16.0% to 45.6% post-defaunation, that is, a near three-fold increase. Such habitat changes seemed to have benefitted those species that use vegetation during reproduction (e.g. the leaf-folding Afrixalus spp.), while others have declined. Interestingly, we found a strong correlation between tadpole community shifts and other freshwater organisms, which indicates that habitat changes have affected a wide variety of aquatic organisms. Given that organisms inhabiting temporary aquatic habitats often have complex life histories with terrestrial adult life stages, we propose that the terrestrial effects of defaunation have indirectly led to distinct aquatic communities, in addition to direct habitat effects. These results shed new light on the potential role of large-bodied mammals in shaping adjacent ecosystems, and raise important questions concerning the functioning of temporary aquatic systems in the Anthropocene.

Contrasting biodiversity and food web structure of three temporary freshwater habitats in a tropical biodiversity hotspot

Abstract In many biomes, a variety of different small freshwater habitats, such as pools and phytotelmata can occur together in the same habitat matrix. However, both the biodiversity and the functioning of these ecosystems remain poorly known. Three freshwater habitat types in a tropical West African biodiversity hotspot were studied. The study demonstrated that animal communities in water‐filled tree holes, temporary ponds and granite rock pools were strongly differentiated with exclusive faunas despite their spatial proximity and similar disturbance in the form of seasonal drought. In particular, granite rock pools stood out with a high gamma diversity. Rock pools were also functionally different from the other two habitat types. The three habitats had contrasting predator assemblages, a differential reliance on primary production and different concentrations of available nutrients. The work illustrates that the biodiversity and functions of small temporary freshwater habitats can be strongly differentiated. This shows the unique and potentially complementary roles that these habitats can fulfil in mediating fluxes of energy and nutrients and preserving aquatic biodiversity in landscapes. Temporary aquatic habitats are typically overlooked in conservation policy and local management plans despite being threatened by habitat transformation. In addition, livestock can threaten savanna ponds, wood exploitation can threaten tree holes, and mining and sediment disruption can threaten rock pools. Hence, better knowledge about the ecological functioning of these ecosystems is vital to the implementation of effective conservation strategies.

Biological Impact of Photoperiod on Fairy Shrimp (Branchinecta orientalis): Life History and Biochemical Composition.

Simple SummaryBranchinecta orientalis G.O. Sars, 1901 is a broadly distributed fairy shrimp species in temporary freshwater pools throughout Europe and Asia. Recently, using fairy shrimps to feed freshwater fish and shellfish species has been brought to attention mainly due to their high nutritional value, possibility of mass culture, and ability to remain alive for long periods when used as prey. Fairy shrimps might be valuable alternatives for the widely used brine shrimp Artemia species; however, relatively little is known regarding their life-cycle characteristics and biochemical properties under various environmental conditions. Among environmental factors, the photoperiod is assumed as an important environmental cue to regulate the growth, development, and physio-biochemical properties of animals. In the present study, the growth performances, reproductive status, and nutritional quality of fairy shrimp were investigated under predefined environmental conditions, i.e., different photoperiods, and compared with various common live prey used in freshwater ornamental fish production.B. orientalis, fairy shrimp, is often among the most conspicuous invertebrates inhabiting temporary aquatic habitats with a typical variation in environmental conditions. Its life history characteristics and biochemical composition were studied under four different photoperiodic regimes (24L:0D, 0L:24D, 16L:8D, and 12L:12D). The significantly highest cumulative and initial hatching rates (48 h) were obtained at 24L:0D (p < 0.05). Cultivating the larvae under different photoperiods did not significantly affect specific growth rate (SGR) (p > 0.05). However, higher final total body length and daily growth rate were recorded under constant darkness. Higher lipid content was found at 24L:0D to the extent that it was more than two times higher than that at 16L:8D and 12L:12D (p < 0.05). There was also a remarkable increase in body crude protein content at 24L:0D (p < 0.05). Body fatty-acid profiles of the fairy shrimps were also affected by culture condition (p < 0.05). Extension of lighting period resulted in a subtle increase in body contents of arginine, lysine, histidine, isoleucine, leucine, valine, methionine, and phenylalanine, especially in the group kept under a 16L:8D regime. The highest and lowest digestive enzyme activity was observed at 0L:24D and 24L:0D, respectively (p < 0.05). In contrast, the highest and lowest soluble protein content was recorded at 24L:0D and 0L:24D, respectively (p < 0.05). Similarly, antioxidant status was significantly higher at 0L:24D (p < 0.05). In conclusion, a 16L:8D light–dark cycle might be an optimal condition in terms of growth performance and physio-biochemical characteristics. These findings could be helpful in optimizing the rearing conditions for upscaling B. orientalis production.

Cannibalism and Necrophagy Promote a Resource Loop and Benefit Larval Development in Insects of Temporary Waters.

Simple SummaryThe consumption of conspecific individuals by cannibalism (i.e., the killing and eating of conspecific individuals) and necrophagy (i.e., feeding on dead individuals of the same species) has been documented in several insect species. Selective advantages have been proposed to explain the persistence of these behaviors in natural populations. In this paper, we tested the hypothesis that cannibalism and necrophagy lead to a significant resource loop within an insect cohort, allowing individual survival and development. With this aim, we performed laboratory and semi-field experiments using the tiger mosquito Aedes albopictus. Larval stages of this species develop in small aquatic habitats, such as tree holes and artificial containers. These latter are highly ephemeral habitats, where resources are often scarce and of poor quality (mainly leaf litter, wood, and vegetal detritus). We first estimated the relative rate of cannibalism and necrophagy. Then, we analyzed the effects of cannibalism and necrophagy on larval survival and adult yield. Consistent with our hypothesis, we found that conspecifics consumed about 50% of the initial cohort. Furthermore, conspecific consumption significantly increased the rate of adult emergence and larval survival, which supports that cannibalism and necrophagy can positively affect insect populations in temporary waters.Temporary aquatic habitats are contingent on the allochthonous inputs of plant and animal detritus, whose quality and availability can significantly affect the species developing in these habitats. Although animal detritus (i.e., invertebrate carcasses) is a high-quality food, it is an unpredictable and variable resource. On the contrary, conspecific individuals (dead or alive) are a nutritionally high-quality food source that is always available. In this context, conspecifics consumption, by cannibalism or necrophagy, can be a good strategy to overcome nutrient limitation and allow individual maintenance and development. Here, we tested this hypothesis by using the tiger mosquito Aedes albopictus. By carrying out laboratory and semi-field experiments, we first estimated the relative rate of cannibalism and necrophagy, under different larval densities. Then, we analyzed the effects of cannibalism and necrophagy on larval survival and adult yield. Consistent with our hypothesis, we found that cannibalism and necrophagy occurred under all experimental conditions, and that conspecific consumption had positive effects on individual development, as it significantly increased the rate of adult emergence and larval survival. Interestingly, about 50% of the initial cohort was consumed by conspecifics, suggesting that cannibalism and necrophagy can drive an important resources loop in temporary aquatic habitats.

Species composition, spatio-temporal variation and habitat characterization of Anopheline larvae in Bure district, northwestern Ethiopia

In Ethiopia, mosquito larva control interventions are given less emphasis due to a number of factors including lack of precise information on potential breeding habitats and complicated vector biology. Hence, the objective of this study was to assess the spatio-temporal variation and habitat characterization of Anopheline larvae in Bure district, Northwestern Ethiopia. Longitudinal larval sampling was done in 3 villages (Bukta, Workimdr and Shnebekuma) for a year (July 2015 - June, 2016). Sampling was done one time per month. Documentation of habitat type and environmental characteristics were done in each round of sampling. A total of 3490 Anophelines larvae were collected in a year. Seven larval species were identified morphologically: Anopheles gambiae s.l, An. funestus s.l, An. pharoensis. An. demeilloni, An. coustani, An. squamosus, An. cinereus. Of these, An. demeilloni (1.97 ± 0.03) and An. gambiae s. l (1.79 ± 0.06) were the predominant larvae, whereas An. pharoensis (0.18 ± 0.04) was the least representative (p < 0.01). Anophelines larvae were found in various breading habitats, but the mean density of Anophelines larvae in dam- edge (0.45 ± 0. 19) was relatively smaller than other habitats (p < 0.01). The large densities of An. gambiae s.l and An. funestus s.l larvae were sampled from natural, permanent and temporary aquatic habitats that had clean and standing water, without mats of algae, vegetation’s and plants. Multiple linear regression analysis showed that only standing water was found to be the main predictor of the density of An. gambiae s.l density (R2 = 0.457; p < 0.016). In conclusion, the larvae of the two most important malaria vectors of Ethiopia, An. gambiae and An. funestus s.l, were collected through the year.

Geographic distribution and conservation of seasonal killifishes (Cyprinodontiformes, Rivulidae) from the Mid-Northeastern Caatinga ecoregion, northeastern Brazil

The Rivulidae fish family, which includes Neotropical seasonal killifishes, is one of the most diverse taxonomic groups in the aquatic systems of Caatinga in Brazil. Cynolebias and Hypsolebias genera, with 20 and 35 endemic species, respectively, concentrate the greatest diversity of rivulid species in the semiarid. Sixty-eight years after the first records of annual killifishes in the Mid-Northeastern Caatinga ecoregion (MNCE), only four valid species have been sampled in this area. Here we combined bibliographic surveys and recent samplings to investigate the distribution of seasonal rivulids in MNCE. Twenty-one records were obtained, nine of which are new localities, expanding the distribution of three species: Hypsolebias martinsi, H. antenori and Cynolebias microphthalmus. Hypsolebias&amp;amp;nbsp;longignatus is still only known from its type locality in Ceará, near the Environmental Protection Area in Pacoti River, and has not been sampled ever since its description in 2008. Among the four species present in MNCE, H. antenori is the only species occurring within the limits of a conservation unit in the Furna Feia National Park. Anthropogenic impacts were observed in most temporary habitats visited, which ranged from river channel to small ponds in cave entrances. All records are found in coastal basins that discharge in the northern coast of the MNCE, in Ceará and Rio Grande do Norte states, which are crucial for the conservation of the Caatinga’s killifishes. The results also evidenced the importance of karstic habitats in the Jandaíra Formation as potential biotopes for seasonal fish in MNCE. This information must be used to update the conservation status of these species and highlight the importance of strategies for preserving the Caatinga’s temporary aquatic habitats, which should be considered for environmental licensing purposes.

Environmental drivers of tadpole community structure in temporary and permanent ponds

About 87 % of the anuran species that occur in Brazil possess a larval stage, i.e., tadpoles. Throughout this stage of development, tadpoles are subject to predation and the conditions of their aquatic habitat, including environmental heterogeneity, physical and chemical properties of the water, and hydroperiod of the water body. We assessed the patterns of species composition and richness of tadpoles in permanent and temporary ponds, with the objective of evaluating how morphometric, physical and chemical factors of the ponds and environmental heterogeneity (surrounding vegetation and substrate cover and aquatic vegetation) affect anuran occupation of these environments. The study was performed in five permanent and four temporary ponds. Tadpoles of 20 anuran species differed in species composition between permanent and temporary environments. Environmental factors were significant drivers for tadpole richness: turbidity and dissolved oxygen were significantly related to richness in permanent ponds, while water temperature and pH were significantly correlated to richness in temporary environments. Higher species richness was related to the heterogeneity of the ponds and greater complexity associated with the stratification of the surrounding vegetation. In general, the results suggest that species sorting of tadpoles is probably related to the high environmental variation among permanent and temporary aquatic habitats. The spatial heterogeneity of these two types of environments increases local diversity by accommodating species that are unique to only one habitat type.

The complete mitogenome of an undescribed clam shrimp of the genus Gondwanalimnadia (Branchiopoda: Spinicaudata), from a temporary wetland in Central District, Botswana

Clam shrimps (Spinicaudata) are a widespread and diverse crustacean group that frequent temporary aquatic habitats, but few complete mitochondrial genomes have been published for this group. Here, we report the mitogenome of an undescribed Gondwanalimnadia species from Botswana. Raw sequences were assembled into a single circular genome with a total length of 15,663 bp. Thirteen protein-coding genes, 22 tRNAs, and 2 rRNAs were identified using the MITOS pipeline. The mitogenome’s GC content is 33.52%. Phylogenetic analysis using protein-coding genes confirmed that Gondwanalimnadia sp. is closely related to another member of the Limnadiidae, Limnadia lenticularis.

Colonization of drying temporary wetlands by Coptotomus loticus (Coleoptera: Dytiscidae): a unique strategy for an aquatic wetland insect

Predaceous diving beetles (Coleoptera: Dytiscidae) are well-known for their ability to colonize both permanent and temporary aquatic habitats. They often move predictably between these two habitats, colonizing recently flooded habitat and returning to permanent habitat during the dry-down phase. However, Coptotomus loticus Hilsenhoff does not appear to utilize this same strategy. The objective of our study was to investigate the spatial and temporal patterns of C. loticus distribution in wetland habitats of the southeastern USA. Floodplain wetlands were sampled seasonally over 2 years (a drought year and a flood year), and Carolina bays were sampled seasonally over 3 years. During the drought year, C. loticus remained primarily in permanent water bodies on the floodplain. During the flood year, C. loticus utilized temporary habitats on the floodplain to a greater degree than in the drought year. High densities of C. loticus were more common in temporary habitat during the latter half of the year (dry-down phase) versus the early actively-flooding portion of the year. The highest density of C. loticus in Carolina bays was also found during the dry-down phase. These results suggest C. loticus may be accessing temporary wetland habitat in which fish and other vertebrates may be stranded as the habitat dries down. Dytiscids have been known to consume vertebrate carrion, and in this study system, C. loticus may be utilizing the dry-down effect to hone in on stranded vertebrates as a readily available food source, a strategy not yet described among wetland macroinvertebrates. This phenomenon warrants further study in this and other systems, however, to verify its existence across time and space.

A general model of temporary aquatic habitat use: Water phenology as a life history filter

AbstractTemporary aquatic habitats are not widely appreciated fish habitat. However, fish navigate the transient waters of intertidal zones, floodplains, intermittent and ephemeral streams, lake margins, seasonally frozen lakes and streams, and anthropogenic aquatic habitats across the globe to access important resources. The selective pressures imposed by water impermanence (i.e., freezing, drying, tidal fluctuations), however, operate similarly across taxa and ecosystems. These similarities are formalized into a conceptual model relating habitat use to surface water phenology. Whereas all necessary life history functions (spawning, foraging, refuge, and dispersal) can be accomplished in temporary habitats, the timing, duration, and predictability of water act as a “life history filter” to which habitats can be used and for what purpose. Habitats wet from minutes to months may all be important—albeit in different ways, for different species. If life history needs co‐occur with accessibility, temporary habitats can contribute substantially to individual fitness, overall production and important metapopulation processes. This heuristic is intended to promote research, recognition and conservation of these frequently overlooked habitats that can be disproportionately important relative to their size or brevity of existence. There is a pressing need to quantify how use of temporary aquatic habitats translates to individual fitness benefits, population size and temporal stability, and ecosystem‐level consequences. Temporary aquatic habitats are being impacted at an alarming rate by anthropogenic activities altering their existence, phenology, and connectivity. It is timely that scientists, managers and policymakers consider the role these habitats play in global fish production.

The complementary role of lentic and lotic habitats for Arctic grayling in a complex stream‐lake network in Arctic Alaska

AbstractLakes can be important to stream dwelling fishes, yet how individuals exploit habitat heterogeneity across complex stream‐lake networks is poorly understood. Furthermore, despite growing awareness that intermittent streams are widely used by fish, studies documenting the use of seasonally accessible lakes remain scarce. We studied Arctic grayling (Thymallus arcticus) in a small seasonally flowing (June–October) stream‐lake network in Alaska using PIT telemetry. Overall, 70% of fish visited two lakes, 8% used a single lake, and 22% used only stream reaches. We identified five distinct behavioural patterns that differed in dominant macrohabitat used (deep lake, shallow lake or stream reaches), entry day into the network and mobility. Some juvenile fish spent the entire summer in a shallow seasonally frozen lake (average 71 days), whereas others demonstrated prospecting behaviour and only entered the stream channel briefly in September. Another group included adult and juvenile fish that were highly mobile, moving up to 27 km while in the 3‐km stream‐lake network, and used stream reaches extensively (average 59 days). Lentic and lotic habitats served differing roles for individuals, some fish occupied stream reaches as summer foraging habitat, and other individuals used them as migration corridors to access lakes. Our study emphasises the importance of considering stream‐lake connectivity in stream fish assessments, even to shallow seasonally frozen habitats not widely recognised as important. Furthermore, we demonstrate that individuals may use temporary aquatic habitats in complex and changing ways across ontogeny that are not captured by typical classifications of fish movement behaviour.

Effects of flash flooding on mosquito and community dynamics in experimental pools.

Pulsed disturbances of larval mosquito sites are likely to have a direct negative effect on mosquitoes but may also have indirect effects due to the alteration of community structure. These altered communities may become attractive to gravid mosquitoes searching for oviposition sites when the disturbances decrease the abundance of mosquito antagonists such as competitors, which often results in an increase in mosquito food resources. However, flash flood disturbances in intermittent riverbeds can also remove mosquito food resources such as algae, so that the net effect of flash floods could be either to increase or decrease mosquito abundance. We conducted an outdoor mesocosm experiment to assess the effects of flash floods on mosquito oviposition habitat selection and larval abundance during the post-disturbance period of community recovery. Mesocosms were artificially flooded. Mosquito oviposition, immature abundance, invertebrate species diversity, chlorophyll a, and abiotic parameters were monitored. Our results showed that the flash flood negatively affected phytoplankton and zooplankton, leading to a decrease of mosquito oviposition in flooded mesocosms compared to non-flooded mesocosms. More broadly, this study indicates how disturbances influence mosquito oviposition habitat selection due to the loss of food resources in ephemeral pools, and it highlights the importance of considering the effects of disturbances in management, habitat restoration, and biodiversity conservation in temporary aquatic habitats.

Patterns of genetic divergence in the Ilyodromus amplicolis lineage (Crustacea, Ostracoda), with descriptions of three new species

In this study, 13 previously recorded populations of Ilyodromus amplicolis De Deckker, 1981 from temporary aquatic habitats in Western Australia were scanned for undescribed species diversity using morphological and molecular systematics techniques. The study found congruent morphological and molecular evidence for three species that are new to science, all of which are formally described here (I. armacutis n. sp., I. sensaddito n. sp. and I. hiatus n. sp.). The findings shed light on the potential for further undescribed diversity in the genus Ilyodromus Sars, 1894.

Seasonal Progression of Aquatic Organisms in a Temporary Wetland in Northern California

Abstract. Seasonal wetlands are important habitats for biodiversity of both invertebrate and vertebrate fauna. Many aquatic species have life history traits adapted to colonizing and developing in temporary aquatic habitats, and these traits influence the annual succession of the macroinvertebrate community. The chronology of taxon appearance and the variation in relative abundances during the hydroperiod are important for understanding population dynamics, trophic interactions, and responses to drought. This study investigated the successional changes in macroinvertebrate abundances in a seasonal wetland in northern California. Water quality parameters were measured regularly, including dissolved oxygen, temperature, pH, surface area, and specific conductance during the wet season ( January–July) in 2007–2009. Macroinvertebrates were collected with net sweeps (mesh > 500 mm), and the presence of life stages of amphibians were visually observed from March to June each year. As the hydroperiod progressed, ...

Rainfall and hydrological stability alter the impact of top predators on food web structure and function.

Climate change will alter the distribution of rainfall, with potential consequences for the hydrological dynamics of aquatic habitats. Hydrological stability can be an important determinant of diversity in temporary aquatic habitats, affecting species persistence and the importance of predation on community dynamics. As such, prey are not only affected by drought-induced mortality but also the risk of predation [a non-consumptive effect (NCE)] and actual consumption by predators [a consumptive effect (CE)]. Climate-induced changes in rainfall may directly, or via altered hydrological stability, affect predator-prey interactions and their cascading effects on the food web, but this has rarely been explored, especially in natural food webs. To address this question, we performed a field experiment using tank bromeliads and their aquatic food web, composed of predatory damselfly larvae, macroinvertebrate prey and bacteria. We manipulated the presence and consumption ability of damselfly larvae under three rainfall scenarios (ambient, few large rainfall events and several small rainfall events), recorded the hydrological dynamics within bromeliads and examined the effects on macroinvertebrate colonization, nutrient cycling and bacterial biomass and turnover. Despite our large perturbations of rainfall, rainfall scenario had no effect on the hydrological dynamics of bromeliads. As a result, macroinvertebrate colonization and nutrient cycling depended on the hydrological stability of bromeliads, with no direct effect of rainfall or predation. In contrast, rainfall scenario determined the direction of the indirect effects of predators on bacteria, driven by both predator CEs and NCEs. These results suggest that rainfall and the hydrological stability of bromeliads had indirect effects on the food web through changes in the CEs and NCEs of predators. We suggest that future studies should consider the importance of the variability in hydrological dynamics among habitats as well as the biological mechanisms underlying the ecological responses to climate change.

Observations on the hatching dynamics and phenology of co-occurring large branchiopods from a small temporary pool in western India usingex situsediment rehydration

Sediment rehydration is a useful technique to study various ecological aspects of resting egg banks of many aquatic invertebrates, but there is a paucity of such studies from the Asian region as compared with other regions. Hence, using a tropical temporary pool as a study system, and with successive, ex situ hydrations of sediments, we studied (1) the hatching phenology and dynamics of co-occurring Notostraca and Anostraca, and (2) the effects of cyclical hydroperiods on these dynamics. Ten species of different aquatic taxa emerged from the sediments. Among the large branchiopods, the primary consumer Streptocephalus dichotomus (Anostraca) was more numerous than the predatory Triops granarius (Notostraca). However, while differing in ecological roles, the two species exhibited similar phenology and hatching strategies, with nauplii emerging in similar proportions across hydration treatments, peaking at the first hydration (∼90%), and decreasing through the third. Hatching began on day 1 in all hydrations and peaked on days 2–3. Hatching duration decreased with successive hydrations, being the longest for the first hydration. These species are important to the food chain associated with temporary aquatic habitats, which are relatively understudied in the Indian context. Laboratory-based studies, in combination with field data can help understand the ecology of the associated community. We highlight the need for such studies that can prove important for conservation of such habitats, when their destruction is rampant and undocumented.