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The associations between feeding activities and environmental variables inform animal feeding tactics that maximize energetic gains by minimizing energy costs while maximizing feeding success. Relevant studies in aquatic animals, particularly marine mammals, are scarce due to difficulties in the observation of feeding behaviors in aquatic environments. This data scarcity concurrently hinders ecosystem‐based fishery management in the context of small toothed‐cetacean conservation. In the present study, a passive acoustic monitoring station was deployed in an East Asian finless porpoise habitat in Laizhou Bay to investigate potential relationships between East Asian finless porpoises and their prey. The data revealed that porpoises were acoustically present nearly every day during the survey period. Porpoise detection rates differed between spring and autumn in concert with activities of fish choruses. During spring, fish choruses were present throughout the afternoon, and this was the time when porpoise vocalizations were the most frequently detected. During autumn, when fish choruses were absent, porpoise detection rates decreased, and diurnal patterns were not detected. The close association between fish choruses and finless porpoise activities implies an "eavesdropping" feeding strategy to maximize energetic gains, similar to other toothed cetaceans that are known to engage similar feeding strategies. Underwater noise pollution, particularly those masking fish choruses, could interrupt finless porpoises' feeding success. Fisheries competing soniferous fishes with finless porpoise could impact finless porpoise viability through ecosystem disruption, in addition to fishing gear entanglement. [ABSTRACT FROM AUTHOR]

• A diel pattern of CH 4 flux with a single afternoon peak was dominated by GEP in the vegetative stage. • Daytime CH 4 emissions showed no peaks and were much lower than nighttime levels, which were frequently observed during the reproductive stage. • Rice plant productivity dominantly control CH 4 flux through carbon supply and transport in the early and late stage, respectively. The diel pattern of CH 4 emissions used in field sampling strategies and time-scale extrapolation is generally regarded as peaking during daytime rather than at night. However, under specific conditions such as water limitation and high temperatures that rice widely undergo, the diel patterns of CH 4 emissions remain unclear. We identified diel patterns in CH 4 flux among rice stages that experienced different water and temperature conditions, using continuous high-frequency measurements over three consecutive years of CH 4 flux in rice paddies. The results showed that a pronounced single peak in CH 4 flux occurred during the daytime (13:30–14:30) in the early rice stage. During the reproductive stage, however, the daytime CH 4 flux decreased significantly, resulting in a distinct reverse diel pattern frequently (80–86%) observed. The daytime CH 4 emissions showed no peaks and were averaged only 41.67% of the nighttime levels under water-limited conditions with high temperatures. Missing the nighttime CH 4 flux would underestimate 28.49–32.98% of the daily CH 4 emissions during the reproductive stage if the nighttime CH 4 flux was calculated using the nighttime/daytime ratio at the vegetative stage. The discovery of a distinct nocturnal peak diel pattern of CH 4 flux, contrary to the well-known daytime peak pattern, indicates that measurements and extrapolations based only on daytime data could underestimate CH 4 emissions from rice paddies. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Predation is the most common cause of nest failure in birds. While nest predation is relatively well studied in general, our knowledge is unevenly distributed across the globe and taxa, with, for example, limited information on shorebirds breeding in subtropics. Importantly, we know fairly little about the timing of predation within a day. Here, we followed 444 nests of the red‐wattled lapwing (Vanellus indicus), a ground‐nesting shorebird, for a sum of 7,828 days to estimate a nest predation rate, and continuously monitored 230 of these nests for a sum of 2,779 days to reveal how the timing of predation changes over the day and season in a subtropical desert. We found that 312 nests (70%) hatched, 76 nests (17%) were predated, 23 (5%) failed for other reasons, and 33 (7%) had an unknown fate. Daily predation rate was 0.95% (95%CrI: 0.76% – 1.19%), which for a 30‐day long incubation period translates into ~25% (20% – 30%) chance of nest being predated. Such a predation rate is low compared to most other avian species. Predation events (N = 25) were evenly distributed across day and night, with a tendency for increased predation around sunrise, and evenly distributed also across the season, although night predation was more common later in the season, perhaps because predators reduce their activity during daylight to avoid extreme heat. Indeed, nests were never predated when midday ground temperatures exceeded 45℃. Whether the diel activity pattern of resident predators undeniably changes across the breeding season and whether the described predation patterns hold for other populations, species, and geographical regions await future investigations.

Humpback whales (Megaptera novaeangliae) produce song and non-song vocalisations, which allows their presence to be detected through passive acoustic monitoring. To determine the seasonal and diel acoustic presence and acoustic behaviour of humpback whales at the migratory stopover site off Bermuda, three hydrophones were deployed between March 2018 and April 2019 on Challenger Bank and the Bermuda platform. Song was the predominant vocalisation type encountered, with 65% of song recordings containing whale chorus and a clear seasonal trend of humpback whale occurrence in the spring and winter months from late December to mid-May. A strong diel pattern in singing activity was detected. Singing activity significantly increased at night relative to the daytime (p

Abstract Background A strong behavioural plasticity is commonly evidenced in the movements of marine megafauna species, and it might be related to an adaptation to local conditions of the habitat. One way to investigate such behavioural plasticity is to satellite track a large number of individuals from contrasting foraging grounds, but despite recent advances in satellite telemetry techniques, such studies are still very limited in sea turtles. Methods From 2010 to 2018, 49 juvenile green turtles were satellite tracked from five contrasting feeding grounds located in the South-West Indian Ocean in order to (1) assess the diel patterns in their movements, (2) investigate the inter-individual and inter-site variability, and (3) explore the drivers of their daily movements using both static (habitat type and bathymetry) and dynamic variables (daily and tidal cycles). Results Despite similarities observed in four feeding grounds (a diel pattern with a decreased distance to shore and smaller home ranges at night), contrasted habitats (e.g. mangrove, reef flat, fore-reef, terrace) associated with different resources (coral, seagrass, algae) were used in each island. Conclusions Juvenile green turtles in the South-West Indian Ocean show different responses to contrasting environmental conditions - both natural (habitat type and tidal cycle) and anthropogenic (urbanised vs. uninhabited island) demonstrating the ability to adapt to modification of habitat.

Predation is the most common cause of nest failure in birds. While nest predation is relatively well studied in general, our knowledge is unevenly distributed across the globe and taxa, with, for example, limited information on shorebirds breeding in subtropics. Importantly, we know fairly little about the timing of predation within a day. Here, we followed 444 nests of the red‐wattled lapwing (Vanellus indicus), a ground‐nesting shorebird, for a sum of 7,828 days to estimate a nest predation rate, and continuously monitored 230 of these nests for a sum of 2,779 days to reveal how the timing of predation changes over the day and season in a subtropical desert. We found that 312 nests (70%) hatched, 76 nests (17%) were predated, 23 (5%) failed for other reasons, and 33 (7%) had an unknown fate. Daily predation rate was 0.95% (95%CrI: 0.76% – 1.19%), which for a 30‐day long incubation period translates into ~25% (20% – 30%) chance of nest being predated. Such a predation rate is low compared to most other avian species. Predation events (N = 25) were evenly distributed across day and night, with a tendency for increased predation around sunrise, and evenly distributed also across the season, although night predation was more common later in the season, perhaps because predators reduce their activity during daylight to avoid extreme heat. Indeed, nests were never predated when midday ground temperatures exceeded 45℃. Whether the diel activity pattern of resident predators undeniably changes across the breeding season and whether the described predation patterns hold for other populations, species, and geographical regions await future investigations. [ABSTRACT FROM AUTHOR]

Many terrestrial and marine species have a diel activity pattern, and their acoustic signaling follows their current behavioral state. Whistles and echolocation clicks on long-term recordings produced by melon-headed whales (Peponocephala electra) at Palmyra Atoll indicated that these signals were used selectively during different phases of the day, strengthening the idea of nighttime foraging and daytime resting with afternoon socializing for this species. Spectral features of their echolocation clicks changed from day to night, shifting the median center frequency up. Additionally, click received levels increased with increasing ambient noise during both day and night. Ambient noise over a wide frequency band was on average higher at night. The diel adjustment of click features might be a reaction to acoustic masking caused by these nighttime sounds. Similar adaptations have been documented for numerous taxa in response to noise. Or it could be, unrelated, an increase in biosonar source levels and with it a shift in center frequency to enhance detection distances during foraging at night. Call modifications in intensity, directionality, frequency, and duration according to echolocation task are well established for bats. This finding indicates that melon-headed whales have flexibility in their acoustic behavior, and they collectively and repeatedly adapt their signals from day- to nighttime circumstances.

Male humpback whales produce complex sounds known as songs during their breeding season. Previous studies have shown diel patterns of song in their breeding areas, but there had been no similar studies in the breeding area around Okinawa, Japan. To study diel patterns of song and the behavior of humpback whales in Okinawa, we conducted 24 hr recording with a fixed hydrophone in 2007, and vessel‐based sighting surveys during 2014–2017. Song was monitored for 15 days, with peaks at sunrise and around 2200. Singing activity declined significantly between sunrise and sunset, then increased until 2200. Activity levels at night were higher and more stable than during the day. During 278 days of sighting surveys, 2,551 whales in 1,382 groups were observed. 79 individuals were confirmed as singers, all of which were lone whales. In six cases, singing individuals stopped singing before joining a group or began singing after leaving a group. Previous studies have shown that group size of humpback whales increases through the day. Considering the results from our study and the former studies, the decrease in singing activity as the day progresses may be a result of aggregation increasing, thus reducing the number of lone singers during the day. [ABSTRACT FROM AUTHOR]

There is limited information about the biology and seasonal distribution of bearded seals (Erignathus barbatus) in Greenland. The species is highly ice-associated and depends on sea ice for hauling out and giving birth, making it vulnerable to climate change. We investigated the seasonality and distribution of bearded seal vocalizations at seven different locations across southern Baffin Bay and Davis Strait, West Greenland. Aural M2 and HARUphone recorders were deployed on the sea bottom during 2006–2007 and 2011–2013. Recordings were analyzed for presence/absence of bearded seal calls relative to location (including distance to shore and depth), mean sea ice concentration and diel patterns. Calling occurred between November and late June with most intense calling during the mating season at all sites. There was a clear effect of depth and distance to shore on the number of detections, and the Greenland shelf (< 300 m) appeared to be the preferred habitat for bearded seals during the mating season. These results suggest that bearded seals may retreat with the receding sea ice to Canada during summer or possibly spend the summer along the West Greenland coast. It is also possible that, due to seasonal changes in bearded seal vocal behavior, animals may have been present in our study area in summer, but silent. The number of detections was affected by the timing of sea ice formation but not sea ice concentration. Diel patterns were consistent with patterns found in other parts of the Arctic, with a peak during early morning (0400 local) and a minimum during late afternoon (1600 local). While vocalization studies have been conducted on bearded seals in Norwegian, Canadian, northwest Greenland, and Alaskan territories, this study fills the gap between these areas. [ABSTRACT FROM AUTHOR]

The amount of short wavelength (ultraviolet (UV), violet and blue) light that reaches the retina depends on the transmittance properties of the ocular media, especially the lens, and varies greatly across species in all vertebrate groups studied previously. We measured the lens transmittance in 32 anuran amphibians with different habits, geographical distributions and phylogenetic positions and used them together with eye size and pupil shape to evaluate the relationship with diel activity pattern, elevation and latitude. We found an unusually high lens UV transmittance in the most basal species, and a cut-off range that extends into the visible spectrum for the rest of the sample, with lenses even absorbing violet light in some diurnal species. However, other diurnal frogs had lenses that transmit UV light like the nocturnal species. This unclear pattern in the segregation of ocular media transmittance and diel activity is shared with other vertebrates and is consistent with the absence of significant correlations in our statistical analyses. Although we did not detect a significant phylogenetic effect, closely related species tend to have similar transmittances, irrespective of whether they share the same diel pattern or not, suggesting that anuran ocular media transmittance properties might be related to phylogeny. [ABSTRACT FROM AUTHOR]

The bluntnose sixgill shark ( Hexanchus griseus Bonnaterre 1788) is a large, deepwater apex predator that, in a few unique locations such as the Strait of Georgia, Canada, occupies shallow, inshore waters as juveniles. The occurrence of pregnant females in the Strait of Georgia suggests that this is an important area for parturition and juvenile rearing. Bluntnose sixgill sharks are listed under the Canadian Species at Risk Act, and an understanding of their behaviour in habitat selection during important life stages is an important component for conservation measures. We employed satellite tags to identify the daily and seasonal depth and thermal habitats of juvenile bluntnose sixgill sharks in the Strait of Georgia. Tag release and depth information suggests that juvenile bluntnose sixgill sharks within the Strait of Georgia remain there until they mature and migrate to offshore deepwaters. The dominant depth habitat utilized by the juvenile sharks in our study was deepwater (>200 m), with only occasional occupation of depths <100 m, indicating that even within coastal areas, juveniles still prefer deepwater. Overall the sharks occupied shallower depths at night than during the day with increased vertical activity in both the day and night compared to crepuscular periods. Seasonally, the sharks occupied shallower depths in the summer than in winter, but inconsistency in the temperatures with which those depths were associated suggests that their vertical behaviour is influenced by local foraging opportunities and not by thermoregulation. [ABSTRACT FROM AUTHOR]

Behavioural lateralization, the preferential use of one side of the body or one of the limbs, is a trait common in vertebrates, and is often expressed as a turning bias in fishes. Recent studies have demonstrated considerable plasticity in lateralization, inferring the role of predation pressure as a key driver of this plasticity over short periods (i.e. days). Such plasticity may be expected if predator pressure is highly variable through space and time and can provide prey with a distinct advantage. We know that increased turning bias is linked with better escape performance, but we do not know the extent to which prey can adjust this trait to match temporal variation in risk. Here we trained juvenile Ambon damselfish to recognize different temporal patterns of risk throughout the day and asked whether their degree of lateralization changed according to this pattern. Damselfish that were taught that midday was risky showed a stronger turning bias at midday than in the evening, whereas damselfish that were taught that evening was risky showed a stronger turning bias in the evening than at midday. Subsequently, we found that fish exposed to cortisol expressed a greater degree of turning bias. Our results suggest that predation stress may be a key factor determining the degree of behavioural lateralization in vertebrates. [ABSTRACT FROM AUTHOR]

• Open-flow photosynthesis system was assembled using an Arduino development board. • System provided a disinfection condition during air ventilation with near-saturated moisture content. • Accurate sampling was conducted by a real-time clock library programmed on the Arduino board. • In vitro pitaya achieved a positive net photosynthetic rate during the daytime period. • Open-flow system yielded a four-phase gas exchange pattern. A non-facultative crassulacean acid metabolism (CAM) profile has been documented in pitaya, in which closed flow photosynthesis systems have been used to evaluate the CAM capacity and characteristics of plants, albeit with overestimation. By contrast, open-flow systems promote measurement reliability and continuously monitor the photosynthetic profile, which has not been reported in pitaya. Therefore, this study aimed to overview the diel gas exchange capacity of Hylocereus polyrhizus 'Da Hong' in an open-flow system, in which the explants were incubated in vitro to prevent measurement deviations caused by microorganism activity. The experimental conditions were 80 µmol/m2/s light intensity at 25 °C under a 16/8 h (D/N) photoperiod. The Arduino-based assembled system contained three subsystems: explant growth, air supplementation, and air sampling and environmental monitoring. The growth vessel had an 83.5% light transmittance with a 3.8 mol/m2/day light intensity. Air ventilation was performed at a flow rate of 1,000 mL/min with 99.9% relative humidity through the filters, which precluded infection and provided a high moisture content environment in the growth vessel during the experiments. A real-time clock library programmed on the development board realized an accurate sampling point and period. The diel gas exchange pattern of pitaya exhibited four phases; explants had a net photosynthetic rate (P n) of 2.63 μmol/m2/s at midnight, and the total net CO 2 uptake over 24 h was 73.98 mmol/m2/day. The positive P n observed during the daytime was noteworthy. This study successfully measured the photosynthetic profile of pitaya in vitro , providing a diel gas exchange reference. An open-flow whole-canopy system could be used in other explants to evaluate the photosynthesis profile in the era of climate change. [Display omitted] [ABSTRACT FROM AUTHOR]

The drift of early development stages is an essential element of dispersal in many fish species. It is caused by a multitude of factors and is thus highly specific for each taxon and developmental stage. In this paper, we examined the drift of free embryos, larvae, and juveniles of percids and gobiids in a free-flowing stretch of the Austrian Danube. We assessed the drift density (DD) at different distances from the shore, described seasonal and diel patterns, and how size of drifting fish changed throughout the season. The seasonal patterns as well as the DDs were highly specific for each genus, while the diel patterns and changes in size of drifting fishes differed primarily at family level. In addition, we compared two opposed shorelines-a near-natural gravel bar and a rip-rap stabilized shore. The shores differed significantly and on both shores the DD of gobies was higher compared to percids. Among the Gobiidae, the invasive Neogobius species clearly dominated (99% of total gobiid catch) over the native tubenose goby Proterorhinus semilunaris. Percid DD was substantially higher on the near-natural shore, with Zingel and Sander as the most abundant genera. [ABSTRACT FROM AUTHOR]

In diurnal species with short breeding seasons, an extension of diel activity to the night hours could be favoured to maximize mating opportunities, but individuals must deal with physiological and behavioural constraints. We tested this hypothesis in the Yungas Red-belly Toad ( Melanophryniscus rubriventris (Vellard, 1947)). We registered the diel pattern of male calling activity in two localities using automated recording systems, and related it to abiotic factors such as temperature, relative air humidity, and precipitation. The diel pattern of vocalization was mainly diurnal. Interestingly though, nocturnal calling activity was a common feature, representing between 40% and 43% of call records in both localities. Vocal activity was significantly influenced by time of the day and presence of rainfall. Calling males showed high plasticity, with activity in the entire environmental range of relative air humidity and temperature. Nocturnal calling seems to play an important role in the mating strategy of males, and it is probably more frequent in the genus Melanophryniscus than currently assumed. We discuss the implications of our findings in relation to different aspects of ecology of the species and suggest that bright colouration in M. rubriventris might result from a compromise between several nonconflicting functions (e.g., aposematism and thermoregulation). [ABSTRACT FROM AUTHOR]

The temporal partitioning hypothesis suggests that the evolution of different diel activity rhythms in animals might facilitate the coexistence between prey and predators. However, the temporal shift of habitat use induced by predation has rarely been observed. The study of such a mechanism is particularly relevant for introduced species because it might explain how native species can persist or decline in response to the presence of alien species. The introduction of fish into ponds inhabited by amphibians has severe consequences for their occurrence and abundance. Fish particularly affect an alternative newt phenotype, the paedomorph, which does not undergo metamorphosis and maintains larval traits such as gills at the adult stage. In a laboratory design, we assessed the diel patterns of habitat use in the 2 distinct morphological phenotypes of palmate newt (Lissotriton helveticus) in the presence or absence of goldfish (Carassius auratus). Both newt phenotypes avoided a risky habitat more in the presence than in the absence of fish. This habitat shift was more pronounced during the daytime (i.e., when the risk could be considered higher for the newts) than during nighttime. However, in contrast to metamorphs, paedomorphs showed less adaptive changes according to temporal risk and remained in their shelter for most of the time. Temporal and habitat partitioning at the diel scale between native and alien species might promote their coexistence, but diel change can also imply a cost in the overall reduction of the time allocated to essential activities, showing that species interactions remain complex. [ABSTRACT FROM AUTHOR]

The response of prey to predation risk varies through time and space. These responses relate to trade-offs between foraging and predator avoidance. Following the extirpation of predators from many landscapes, the responses related to predator avoidance may have been lost or diluted. Investigating the activity pattern of prey species on comparable landscapes with and without large predators provides an opportunity to understand how predators may shape prey activity and behaviour. Using camera trap data from neighbouring fenced sections of the Addo Elephant National Park (Eastern Cape, South Africa), we investigated the activity patterns of species exposed to large predators, where the predators were only present in one of the sections. Our results suggest that prey species at risk of predation (e.g., buffalo, kudu and warthog) are more likely to be active diurnally when co-existing with nocturnally active predators, thereby reducing the activity overlap with these predators. In the absence of predators, kudu and buffalo were more active at night resulting in a low overlap in activity between sections. Warthog activity was predominantly diurnal in both sections, resulting in a high overlap in activity between sections. The presence of predators reduced the nocturnal activity of warthogs from 6 to 0.6 % of all warthog captures in each section. Elephants, which are above the preferred prey weight range of the predators and therefore have a low risk of predation, showed higher overlap in activity periodicity between predator-present and predator-absent areas. Our findings suggest that maintaining prey with their predators has the added benefit of conserving the full spectrum of prey adaptive behaviours. [ABSTRACT FROM AUTHOR]

Soil CO2 flux is strongly influenced by precipitation in many ecosystem types, yet knowledge of the effects of precipitation on soil CO2 flux in semi-arid desert ecosystems remains insufficient, particularly for sandy soils. To address this, we investigated the response of sandy soil CO2 flux to rainfall pulses in a desert ecosystem in northern China during August-September 2011. Significant changes ( P < 0.05) were found in diel patterns of soil CO2 flux induced by small (2.1 mm), moderate (12.4 mm) and large (19.7 mm) precipitation events. Further analysis indicated that rainfall pulses modified the response of soil CO2 flux to soil temperature, including hysteresis between soil CO2 flux and soil temperature, with Fs higher when Ts was increasing than when Ts was decreasing, and the linear relationship between them. Moreover, our results showed that rainfall could result in absorption of atmospheric CO2 by soil, possibly owing to mass flow of CO2 induced by a gradient of gas pressure between atmosphere and soil. After each precipitation event, soil CO2 flux recovered exponentially to pre-rainfall levels with time, with the recovery times exhibiting a positive correlation with precipitation amount. On the basis of the amounts of precipitation that occurred at our site during the measurement period (August-September), the accumulated rain-induced carbon absorption evaluated for rainy days was 1.068 g C m−2; this corresponds approximately to 0.5-2.1% of the net primary production of a typical desert ecosystem. Thus, our results suggest that rainfall pulses can strongly influence carbon fluxes in desert ecosystems. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The Istanbul Strait (Bosphorus) is a part of the Turkish Straits System, connecting the Aegean Sea and the Black Sea. There are three cetacean species in the Strait, namely the harbour porpoise (Phocoena phocoena), the common dolphin (Delphinus delphis), and the bottlenose dolphin (Tursiops truncatus). To monitor the presence of the cetaceans, a fixed stereo passive acoustic monitoring system (A-tag) was deployed in the middle of the Strait from July 2009 to September 2010. In total 26,814 click trains were detected. Presence, direction and inter-click intervals of phonating cetaceans were measured. Most click trains were detected during the night time. Diel presence pattern was prominent in March and April. In spring, the cetaceans were concentrated in one specific direction from the fixed monitoring system. In contrast, they were found in all directions for the rest of the year. Short range sonar (inter-click intervals (ICIs) less than 50 ms) was commonly detected in spring. During the rest of the year ICIs could reach up to 150 ms. All these findings suggest that they were feeding or socializing in spring and mostly travelling in the other seasons. It is well known that pelagic fish such as sprat and bluefish start their migration from the Aegean Sea to the Black Sea in spring. This study suggests that the cetaceans use the middle part of the Strait for feeding on the pelagic fish in spring when the fish migration has just started. [ABSTRACT FROM PUBLISHER]

Abstract: Microbial decay of emergent macrophyte litters in the standing-dead phase is an essential component of litter decomposition and thus carbon (C) cycle in wetland ecosystems. In this study, we examined the amount of microbial respiration from standing litter in a Deyeuxia angustifolia-dominated marsh in the Sanjiang Plain by integrating field studies with laboratory experiments. In the field, CO2 evolution from standing litter exhibited a pronounced diel pattern, with high evolution rates concurring with increasing litter water potential at night. Notably, significant CO2 evolution even existed at temperature of −4°C. Overall, rates of CO2 evolution showed strong positive correlations with relative humidity and litter water potential. In the laboratory, rates of CO2 evolution from wetted culms and leaves increased with increasing temperature, and the relationship between CO2 evolution rates and temperature could be well described with an exponential model. Based on extrapolation from temperature-adjusted mean CO2 evolution rates and standing litter mass, annual CO2 fluxes of culms (3.07gCm−2 yr−1) and leaves (6.81gCm−2 yr−1) accounted for 2.32% (culms, 132.30gCm−2 yr−1) and 6.94% (leaves, 98.20gCm−2 yr−1) of the corresponding annual net aboveground production, respectively. In total, microbial mineralization of standing litter only contributed to 1.12% of the ecosystem respiration (880gCm−2 yr−1). Our results highlight the importance of standing-dead phase in litter decomposition and C cycle in wetlands, and also suggest that CO2 flux from standing litter could even be neglected in assessing C budget in the D. angustifolia-dominated freshwater marshes in the Sanjiang Plain, Northeast China. [Copyright &y& Elsevier]

Fluorotelomer alcohols (FTOHs) and perfluorooctane sulfonamides (FOSAs) are present in consumer products and are semi-volatile precursors of persistent perfluoroalkyl acids (PFAAs). The high variability of levels of FTOHs and FOSAs in products makes it difficult to derive FTOH- and FOSA-emissions from urban areas based on emission factors. Here we used a multimedia mass balance model that describes the day–night cycle of semi-volatile organic chemicals in air to interpret measurements of 8:2 FTOH, 10:2 FTOH, MeFOSA and EtFOSA from a sampling campaign in summer 2010 in Zurich, Switzerland. The estimated emission source strength of the four substances follows the sequence: 8:2 FTOH (2.6 g/h) > 10:2 FTOH (0.75 g/h) > MeFOSA (0.08 g/h) > EtFOSA (0.05 g/h). There is no FTOHs- or FOSAs-related industry in Zurich. Accordingly, our estimates are representative of diffusive emissions during use and disposal of consumer products, and describe noticeable sources of these PFASs to the environment. [Copyright &y& Elsevier]

This study investigated diel changes in ambient noise levels and the number of whistles produced by bottlenose dolphins (Tursiops truncatus) at the Brookfield Zoo in Brookfield, Illinois. Automated, continuous 24-h underwater recordings were made from 1 January to 31 March 2008. The number of whistles, types of whistles, and background noise level were examined for each hour. Nine distinct frequency contours were identified, named, and analyzed for minimum frequency, maximum frequency, peak frequency, and duration. Since all pumps and filters at the Seven Seas Exhibit of Brookfield Zoo were housed in a separate building isolated from the dolphins' pools, background noise was relatively low and consistent throughout the day (95 to 98 dB re: 1 μPa). However, when the zoo staff used a scrubber to clean the pool walls, the background noise was higher and fluctuated (up to 112 dB re: 1 μPa). The dolphins whistled significantly less during these scrubbing periods. The dolphins exhibited a distinct diel pattern in whistle production. Increased whistle production coincided with increased interactions with humans during feeding/training sessions; the number of whistles peaked in the late afternoon (∼1600 h) and then quickly tapered off throughout the night. The investigation began with eight dolphins; however, the death of one young male and the transport of two adult males to another facility left five dolphins: two adult females and two juvenile females along with an unrelated young male. These changes provided an opportunity to explore how social change affected whistle production. After the two adult males were transported out of the facility, two of the distinct whistle types disappeared, suggesting that each of the two dolphins had a unique whistle type. The results of this investigation highlight the usefulness of passive recording for monitoring ambient noise, as well as for documenting the activity pattern and social interactions of captive bottlenose dolphins. [ABSTRACT FROM AUTHOR]

The present study aimed to record all flower visitors of Aechmea nudicaulis (Bromeliaceae) and their foraging behavior as well as their role in animal-plant and animal-animal relationships, and to assess temporal pattern of visitation on flowers. In order to estimate the influence of habitat on species richness and abundance, we compared the diversity and visitation frequency of flower visitors to Ae. nudicaulis in three different habitat types - secondary forest, low and high vegetation restinga - in Parana and Santa Catarina. We recorded 40 taxa of flower visitors. The secondary forest sites showed highest, the restinga habitats lowest species richness and visitation frequency. Main visitor groups were birds, bees and butterflies. The species spectrum differed considerably among habitats and similarity was lowest between the two secondary forests in Parana and Santa Catarina. We recorded mainly hummingbirds (54.6% of all visits) as flower visitors in Parana, whereas flowers in Santa Catarina were dominated by bees (44.5-59.7% of all visits). The temporal pattern of visits was similar at all sites; visits occurred mainly in the morning hours. However, there was no significant correlation between number of visits and hour of day. In contrast to the expectation that Ae. nudicaulis flowers, due to their morphology, attract mainly hummingbirds, they were visited by a much wider spectrum of animal species, mainly insects and arachnids, varying according to habitat. Our findings answer the question of what attracts animals to the inflorescences and elucidate the nature of some of the manifold interactions between Ae. nudicaulis and its associated flower visitors. [ABSTRACT FROM AUTHOR]

Abstract: Fish activity was monitored analyzing the catches of gillnets exposed for short time intervals at night. Experiments were done in two Central European reservoirs with different turbidity and fish density. Cyprinids dominated in both reservoirs. The aims of the study were to describe and model a pattern of fish activity in general and on species and age group levels, and in turbid and clear water. Fish activity showed two distinct peaks around sunset and sunrise and was low during night. This pattern was the same in clear and turbid reservoirs, as well as for all species and age groups tested. This study established some justifications and standards for gillnet sampling: (i) it is possible to compare overnight gillnet catches between different lowland European species and waterbodies, as the pattern of fish activity is general; (ii) gillnets should be set 2–3h before sunset and lifted 2–3h after sunrise to cover activity peaks, thus getting reliable and comparable results; (iii) depicting gillnet catches per average hour of exposition produces biased and incomparable results. [Copyright &y& Elsevier]

The article presents a study which examines the short-term movements of small temperate fish Serranus scriba in the marine protected area (MPA) of Palma Bay, Spain through the use of passive acoustic telemetry. It mentions that the researchers have surgically implanted fifteen adult fishes with acoustic transmitters and monitored them for seven months in which they have detected interindividual variability on the animals. It affirms that two principal movement behaviors that are being detected from the study include having some of the fishes showing high site fidelity and others having a more mobile behavior.

Abstract: The activity rhythms of marine species may consistently bias demographic evaluation by bottom trawl survey, depending on the time of day. In this study, we examine occurrence data of selected commercial and non-commercial decapod species at different depths (0–800m) of the western Mediterranean as produced by the Mediterranean international trawl survey (MEDITS) UE Program by sampling during daytime. In order to show how the activity rhythms and types of displacement (pelagic, nektobenthic and endobenthic) of different species can alter the occurrences determined by bottom trawling, and to quantify relative bias, we modeled potential outcomes of a putative nocturnal MEDITS sampling. MEDITS and published data for studies with 24-h hauls were compared in order to obtain a folding correction factor. We found that the temporal bias of sampling is moderate when trawling is performed on the continental slope and more important when it occurs on the continental shelf. The configuration of daytime and nighttime occurrence data by depth was performed using non-metric multidimensional scaling (nMDS). For the daytime configuration, association with irradiance (PAR) was evaluated by fitting occurrence data with a generalized additive model (GAM). Symmetry in species assemblages was found according to depth (inflection point at 200m depth) as a significant irradiance-dependence distribution pattern of occurrences that took place on the shelf, above 200m depth. For the night configuration, the inflection point relaxed due to the active displacements of some species, mixing the assemblages reported in daytime data. Results of the present study indicated that a deep knowledge of the autoecology of decapod species as it relates to activity rhythms (including a precise assessment of displacement typology) is of importance in population distribution and biomass evaluation and also influences locally perceived biodiversity. Accordingly, bottom trawl surveys for population assessment should take into account the timing of sampling as a factor potentially biasing obtained abundances. [Copyright &y& Elsevier]

The activity patterns for most animals are determined through a trade-off among competing processes, such as foraging behaviour, predator or competitor avoidance, and maintaining bioenergetic efficiency. We used active and passive acoustic telemetry to examine what processes may contribute to diel and seasonal patterns of vertical movement in 27 sixgill sharks in Puget Sound, WA, U.S.A., from December 2005 to December 2007. We found clear and consistent patterns of diel activity; sixgill sharks were typically shallower and more active at night than during the day. In Elliott Bay, WA, sixgill sharks made direct vertical movements at sunrise and sunset, while vertical movements were more variable in deeper, main channel waters. The greatest rates of ascent and descent in sixgill sharks occurred most often during night-time ebb tides. Seasonally, sixgill sharks occupied deeper habitats during the autumn and winter than during spring and were most active in the autumn. We also found synchronous vertical movements in three of four shark pairs tracked simultaneously, evidence that these sharks were responding to similar stimuli. Clear and consistent patterns of diel activity throughout the year across size and sex of sharks and across multiple spatial scales is most consistent with the hypothesis that foraging behaviour is responsible for the patterns of diel vertical movement of sixgill sharks in Puget Sound. [Copyright &y& Elsevier]

The article discusses a study which explored the transatlantic migration and deep mid-ocean diving by basking sharks, Cetorhinus maximus. It presents results on the tracks and behaviour of two basking sharks tagged off the British Isles, one of which released its tag off Newfoundland. Data on the shark's transit of the North Atlantic provide the first evidence for a link between European and American populations. Basking sharks' use of deep-water habitat beyond the shelf edge is also noted.

Despite potentially reducing predation mortality, behavioural responses of native species to introduced predators may still have sub-lethal impacts. In video-recorded laboratory trials, we examined the effects of introduced brown trout, Salmo trutta, on the short-term behaviour of a threatened, lake-dwelling galaxiid fish and confirmed a suspected diel pattern in habitat use by this species. We found that Galaxias auratus followed a distinct diel pattern in the use of complex habitats and open water, which was significantly altered by the presence of brown trout. In trials without the introduced predator, G. auratus used complex habitats (rocks or macrophytes) during the day, and open water during the night. In trials with brown trout present, G. auratus spent significantly less time in open water and rarely ventured out of the macrophytes. However, when given the option of using only rocky substrate or open water, which is the more common situation in the lakes to which this galaxiid is endemic, the fish reduced the amount of time they spent in the open water during the night, but still spent more time in open water than when macrophytes were available. Spending the daylight hours amongst the cover of rocks or macrophytes is most likely an adaptation to reduce the risk of predation by visual predators, and the pattern of reduced use of open water habitats in the presence of brown trout is an acute response to the close proximity of the introduced predator. The difference in the nocturnal use of macrophytes and rocks when trout are present may be related to differences in feeding opportunities or success within these habitats. [ABSTRACT FROM AUTHOR]

Abstract: The diving behaviour of four leatherback turtles (Dermochelys coriacea) was recorded for periods of 0.5–8.1 months during their postnesting movements in the Indian and Atlantic Oceans, when they covered 1569–18,994 km. Dive data were obtained using satellite-linked transmitters which also provided information on the dive depths and profiles of the turtles. Turtles mainly dove to depths <200 m, with maximum dive durations under 30–40 min and exhibited diel variations in their diving activity for most part of the routes, with dives being usually longer at night. Diurnal dives were in general quite short, but cases of very deep (>900 m) and prolonged (>70 min) dives were however recorded only during daytime. The three turtles that were tracked for the longest time showed a marked change in behaviour during the tracking, decreasing their dive durations and ceasing to dive deeply. Moreover, diel variations disappeared, with nocturnal dives becoming short and numerous. This change in turtle diving activity appeared to be related to water temperature, suggesting an influence of seasonal prey availability on their diving behaviour. The turtle diving activity was independent on the shape of their routes, with no changes between linear movements in the core of main currents or looping segments in presence of oceanic eddies. [Copyright &y& Elsevier]

• Karst rivers CO 2 flux have a diel pattern of falling during daytime and rising at night. • Precipitation can interrupt or weaken the diel pattern amplitude of CO 2 degassing. • Water level controls the CO 2 flux dynamics after rainfall. • High‐resolution monitoring helps to minimize uncertainty of riverine CO 2 flux estimates. Estimates of CO 2 flux from rivers are uncertain due to limited measurements at high-resolution. In addition, precipitation may impact diurnal variation of riverine CO 2 flux but the processes controlling those impacts are unknown. Here, we examine the diurnal characteristics of some physicochemical parameters, meteorological parameters, water level, δ13C DIC values, and the CO 2 emission flux at two transects (DM and PY) of a typical karst river (Lijiang River, LJR), southwest China, during May 13–16, 2017. Our results show significant correlations between CO 2 flux, DO, p CO 2 , and δ 13C DIC and reflect control of CO 2 flux diel pattern (decreasing during daytime and increasing at night) by metabolic processes of aquatic plants. The amplitude of CO 2 flux diel pattern is weakened at DM. In contrast, diurnal pattern are interrupted at PY by the precipitation, and afterwards controlled by water level due to the significant positive correlation between water level and CO 2 flux. Certainly, this amplitude will return to prestorm values as the water level recovered. We suggest that effects of precipitation on regional CO 2 efflux estimate require scaling water level and CO 2 flux with a linear relationship, and converting hourly flux to daily flux (α values) to improve the estimate of CO 2 flux diel cycle. These methods will optimize sampling monitoring strategies and provide more reliable estimates of regional riverine CO 2 emissions. [ABSTRACT FROM AUTHOR]