Theoretical habitat templets, species traits, and species richness: birds in the Upper Rhône River and its floodplain

• 1 To test predictions of the river habitat templet and the patch dynamics concept, twenty species traits and the species richness of eighty-one bird species were examined in the context of the spatial – temporal variability of ninety-one sites at Jons, a section of the Upper Rhône River, France.
• 2 The basic information was obtained either from the literature (for species traits) or by observation, then structured by a fuzzy coding technique, and examined using multivariate analyses.
• 3 The relationships between species traits separated three groups of birds: (i) large species that are long lived, have long breeding cycles, and use open sites to feed, breed, and sing (e.g. Podicipidae, Laridae); (ii) medium-sized species with intermediate longevities and breeding cycles that use less open sites (e.g. Columbidae, Corvidae); and (iii) small species that are short lived, have short breeding cycles, and use closed sites (e.g. Sylviidae).
• 4 The distribution of birds in the floodplain habitats of the river was closely related to the spatial–temporal variability of sites.
• 5 No trends in species traits were observed along a gradient of spatial–temporal variability of the sites.
• 6 Species richness of birds was relatively constant over the gradient of spatial–temporal variability of the ninety-one sites, but decreased at low spatial and high temporal variability because of human activities and vegetation changes that occurred at these sites.
• 7 These observations on species traits and richness were related to the high mobility of birds (which is a scale phenomenon) and the high intercorrelation between parameters used to determine the spatial and temporal variability of the sites (which makes separation of the spatial from the temporal variability impossible).

     

Stream community structure in relation to spatial and temporal variation: a habitat templet study of two contrasting New Zealand streams

• 1 The physical characteristics of two contrasting streams, and habitat types within these streams, are described in terms of a two-dimensional physical habitat templet in which disturbance frequency and the availability of spatial refugia are the temporal and spatial axes.
• 2 It is predicted that habitats experiencing a high disturbance frequency and low refuge availability will be characterized by a low invertebrate species diversity, a low biomass of epilithic algae and particulate organic matter and a community made up of mobile, weedy species. Habitats having a low disturbance frequency and high refuge availability will be characterized by a diverse community containing sedentary and specialist species, with high algal and particulate organic matter levels.
• 3 A lower median substrate particle size and higher shear stress regime in Timber Creek were indicative of a higher disturbance frequency than in the Kyeburn. Substrate diversity was lower in Timber Creek than in the Kyeburn and indicated that the availability of refugia was lower in Timber Creek. In both streams, pools were found to have a higher disturbance frequency and lower availability of refugia than riffles.
• 4 Invertebrate species diversity, the biomass of epilithic algae and particulate organic matter and the representation of sedentary species, filter feeders and shredders were higher in the more temporally stable and spatially heterogeneous Kyeburn. The community of Timber Creek, frequently disturbed and having low refuge availability, had a high proportion of mobile and weedy species, with the highly mobile, generalist-feeding Deleatidium spp. (Ephemeroptera; Leptophlebiidae) being the most dominant organisms.
• 5 The predictions made about stream community structure and species characteristics in relation to disturbance frequency and the availability of spatial refugia are generally supported. Now a larger scale investigation is required to test the generality of the predictions. We conclude that the habitat templet approach offers a sound framework within which to pose questions in stream ecology.

     

Flyway‐scale analysis reveals that the timing of migration in wading birds is becoming later

1. Understanding the implications of climate change for migratory animals is paramount for establishing how best to conserve them. A large body of evidence suggests that birds are migrating earlier in response to rising temperatures, but many studies focus on single populations of model species.
2. Migratory patterns at large spatial scales may differ from those occurring in single populations, for example because of individuals dispersing outside of study areas. Furthermore, understanding phenological trends across species is vital because we need a holistic understanding of how climate change affects wildlife, especially as rates of temperature change vary globally.
3. The life cycles of migratory wading birds cover vast latitudinal gradients, making them particularly susceptible to climate change and, therefore, ideal model organisms for understanding its effects. Here, we implement a novel application of changepoint detection analysis to investigate changes in the timing of migration in waders at a flyway scale using a thirteen‐year citizen science dataset (eBird) and determine the influence of changes in weather conditions on large‐scale migratory patterns.
4. In contrast to most previous research, our results suggest that migration is getting later in both spring and autumn. We show that rates of change were faster in spring than autumn in both the Afro‐Palearctic and Nearctic flyways, but that weather conditions in autumn, not in spring, predicted temporal changes in the corresponding season. Birds migrated earlier in autumn when temperatures increased rapidly, and later with increasing headwinds.
5. One possible explanation for our results is that migration is becoming later due to northward range shifts, which means that a higher proportion of birds travel greater distances and therefore take longer to reach their destinations. Our findings underline the importance of considering spatial scale when investigating changes in the phenology of migratory bird species.

     

Theoretical habitat templets, species traits, and species richness: a synthesis of long-term ecological research on the Upper Rhône River in the context of concurrently developed ecological theory

• 1 Based on information obtained from analysis of thirteen taxonomic groups of plants and animals occurring in the alluvial floodplain habitats of the Upper Rhône River, France, we synthesize results obtained on: (i) relationships among species traits; (ii) habitat utilization by species; (iii) the relationship between species traits and habitat utilization; (iv) trends in species traits in a framework of spatial and temporal variability; and (v) tests of trends predicted for species traits and species richness in the framework of spatial and temporal habitat variability in terms of the river habitat templet and patch dynamics concept.
• 2 Species traits describing reproductive characteristics, food, and size had the closest relationships with each other in the various correspondence analyses performed. Faunal and floral separation by species traits produced groupings similar to those based on traditional taxonomy.
• 3 Two major gradients appear in the utilization of the floodplain habitats: a vertical gradient from interstitial to superficial habitats; and a transverse gradient from the main channel to oxbow lakes, temporary waters, and terrestrialized habitats.
• 4 For the majority of the groups examined, a statistically significant relationship was evident between the structure of the species trait and habitat utilization arrays. For these groups, the characteristics of the habitat act as a templet for species traits. Moreover, species trait modalities (i.e. categories defining traits) were significantly arranged along the axis of spatial and temporal variability for most groups, which indicates that such variability acts as a templet for species traits.
• 5 Species traits did not conform to predictions of the river habitat templet because the observed modality sequences did not follow the trends predicted in a framework of spatial and temporal variability. Moreover, there was no clear pattern in the distribution of species traits along an axis of temporal variability for groups of organisms having different sizes, which is a correlate of longevity, nor did modalities of species traits that occur under conditions of low temporal variability also tend to occur under conditions of high spatial variability (or vice versa). Clearly, species traits occur as alternative suites of characteristics in various groups of organisms.
• 6 The patch dynamics concept, which predicts that highest species richness occurs at intermediate levels of temporal variability and highest levels of spatial variability, was supported by observations in only two of the thirteen groups exaniined, and only partially (for spatial variability) when all 548 taxa were examined together.
• 7 The predictions of the river habitat templet and patch dynamics concepts were not supported, perhaps because templet theories do not yet accommodate alternative suites of characteristics and trade-offs between combinations of traits, or perhaps because the single scale of variability considered in the analyses, the inhomogeneity of the available biological information, and the aggregation of spedes traits that were used created methodological problems.
• 8 Ecologically sound river management polides eventually may be based on two key points that emerged from this synthesis: that the habitat acts as a templet for spedes traits, and that composite taxonomic groupings represent relatively homogeneous assemblages of spedes trait modalities.
• 9 The use of statistical approaches developed in this project to analyse other long-term data sets may clarify questions about the applicability of habitat templet theories to river ecology, and hasten development of ecologically sound river management policies.

     

Temporal and spatial environmental variability in the Upper Rhône River and its floodplain

• 1 This paper develops a framework of spatial and temporal variability for a habitat typology of the Upper Rhône River (France) and its alluvial floodplain that is based on about 17 years of data collection and analysis. The aim was to provide a scale of spatial-temporal variability for river habitat templet predictions on trends in species traits and species richness.
• 2 In developing this framework, eight physical-chemical variables were available and could be considered for twenty-two habitat types: seventeen superficial (surface) and five interstitial (0.5 m below the substrate surface). These habitat types were selected in two areas (Jons and Brégnier-Cordon) after geomorphological considerations and because of differences in their biological characteristics.
• 3 The data sets used were processed by a ‘fuzzy coding’ method using, for each variable, the frequency distribution (by modalities = categories) of all measurements and monthly means over an annual scale. Two tables were produced; the first corresponded to an expression of the total variability, and the second represented an evaluation of the temporal variability.
• 4 Each of these tables was analysed by correspondence analysis, which provided factorial scores that were used to calculate, by habitat type and by variable, a total variability and a temporal variability in terms of cumulated variability of factorial scores for the eight physical–chemical variables. The rationale in describing variability from these two tables is that total variability equals temporal variability plus spatial variability. The spatial variability was then determined by the difference between total and temporal variability. From this procedure, a positioning of the twenty-two habitat types on the spatial and temporal variability axes was obtained.
• 5 The estimate of spatial variability did not consider any error term that may have occurred in the above model; it was then tested by an independent assessment of the spatial variability using thirteen variables in nine major habitat types. A high correlation between the two ways of assessing spatial variability (r = 0.85, P < 0.004) underscored the reliability of the spatial variability that was calculated previously.
• 6 The river habitat templet obtained for the Upper Rhône and its alluvial floodplain appears to be appropriate to test the predictions on patterns of species traits and species richness in the framework of spatial and temporal variability.

     

Population differentiation in whiskered auklets Aethia pygmaea: do diurnal and nocturnal colonies differ in genetics,morphometry and acoustics?

Despite a great number of empirical studies, the mechanisms of population differentiation and the factors that influence this process, particularly in seabirds, remain insufficiently understood. Here we analyzed population structure in the whiskered auklet Aethia pygmaea, a previously poorly studied alcid species with unusual differentiation in colony attendance rhythms (i.e. diurnal in the Sea of Okhotsk vs nocturnal in the Bering Sea), and examined the influence of it on intraspecific differentiation. For this study, we analyzed morphometric measurements, acoustic variables, mitochondrial control region fragment and five microsatellite loci from nine whiskered auklet colonies spanning the breeding range. Previous research has shown a clinal morphometric variation in this species. We build on this analysis by adding auklets from more colonies, for the first time analyzing vocalizations from different colonies and genetic structure of this species. Our data supports a clinal variation in morphometric and acoustic characters with the largest size and the lowest call frequency in western birds, and the smallest size and highest call frequency in the east. We also found two mitochondrial lineages – whiskered auklets from colonies in the Sea of Okhotsk and the Commander Is. (Bering Sea) and from the Aleutian Is. (Bering Sea), that were presumably formed during Sangamonian interglacial period (115 000–130 000 years ago). Genetic clusters found did not reflect differences in colony attendance rhythms, suggesting that they were shaped by other factors (e.g. differences in predator pressure) and are unlikely to have participated in the formation of population structure. Colony fidelity, mobility of birds, proximity of foraging grounds and location of colonies in relation to seasonal ice pack, seem to be more likely determinants of population differentiation.     

Real-time weather analysis reveals the adaptability of direct sea-crossing by raptors

Many animals seasonally travel between their breeding and wintering grounds. With their advanced mobility, birds often migrate over thousands of kilometres. Recently, satellite-tracking studies have revealed peculiar migration routes for some avian species at a global scale. However, the adaptability of such migration routes has not been clearly demonstrated. Using satellite-tracking data for 33 individuals, we show that the Japanese population of Oriental honey-buzzards (Pernis ptilorhynchus) directly crosses the 650-km-wide East China Sea during their autumn migration, although they fly a longer route around the sea rather than directly crossing it during their spring migration. By applying aerodynamic theory, we show that the buzzards could cross the sea by soaring and gliding flight. Moreover, using a high-resolution meteorological-prediction analysis, we demonstrate that the migratory trajectory of the birds strongly depends on the wind direction at their estimated locations. In the area, northeastern tailwinds blow stably only during autumn. Thermals were abundant ca. 500–1,000 m over the East China Sea in autumn, but that was not the case in spring. We suggest that the autumn-migration route across the East China Sea is likely to have evolved in response to the specific weather conditions over the sea. Animations showing movements of Oriental honey-buzzards and temporal change in weather conditions are available at: , , , , , and .     

Post‐breeding movements of northeast Atlantic ivory gull Pagophila eburnea populations

The post‐breeding movements of three northeast Atlantic populations (north Greenland, Svalbard and Franz Josef Land) of the ivory gull Pagophila eburnea, a threatened high‐Arctic sea‐ice specialist, were studied between July and December 2007 using 31 satellite transmitters. After leaving their breeding grounds, all birds first dispersed eastward in August–September, to an area extending from the Fram Strait to the northwestern Laptev Sea (off Severnaya Zemlya). Most returned along the same flyway in October–November, hence describing a loop migration before moving south, off east Greenland. Wintering grounds were reached in December, in southeast Greenland and along the Labrador Sea ice‐edge, where Canadian birds also overwinter. One to two birds from each population however continued eastwards towards a third wintering area in the Bering Strait region, hence demonstrating a bi‐directional migration pattern for the populations and elucidating the origin of the birds found in the north Pacific during winter time. Overall, all birds breeding in the northeast Atlantic region used the same flyways, had similar rates of travel, and showed a peak in migratory activity in November. Though the total length of the main flyway, to the Labrador Sea, is only and at most 7500 km on a straight line, the mean total distance travelled by Greenland birds between July and December was 50 000 km when estimated from hourly rates of travel. Our study presents the first comprehensive and complete picture for the post‐breeding movements of the different ivory gull populations breeding in the northeast Atlantic.     

Overview of sperm whale Physeter macrocephalus mortality events in the Adriatic Sea, 1555–2009

• 1 In the Mediterranean Sea, the sperm whale Physeter macrocephalus is one of eight regular cetacean species. Poor knowledge of its ecology and status, together with suspected decline in numbers, make studies of historical and present occurrence especially relevant. Long‐term time series of stranding events are the most reliable data to provide a scientific framework for testing hypotheses that seek to explain the mechanisms responsible for cetacean strandings.
• 2 We present a comprehensive overview of cases of sperm whale mortality and human response to such events encompassing five centuries (1555–2009) within a portion of the Mediterranean Sea that offers a wealth of historical information – the Adriatic Sea.
• 3 A total of 36 mortality events were validated, involving 68 animals. Two findings of skeletal materials are also reported. The geographic distribution of strandings within the basin clearly was uneven: 44% of records (n = 16) were clustered along a 280km portion of the western Adriatic coast. A relatively high number of mortality events occurred along gently sloping sandy beaches away from suitable sperm whale habitat.
• 4 Until the first half of the 20th century, live‐stranded animals were routinely killed: all but one cases with known human response elicited killing attempts. Starting from the 1980s, killing was replaced by efforts to rescue the animals.
• 5 Mass strandings of sperm whales have occurred since historical times in the Adriatic Sea. Mortality events involving multiple individuals accounted for at least 17% of the total sample (6 of 36 mortality events). At least 29% of live strandings (6 of 21) involved more than one individual.
• 6 This study contributes a long‐term dataset based on careful validation of historical information, suitable for hypothesis testing aimed at investigating spatial and temporal correlates of sperm whale strandings – particularly live strandings – as a clue to their causes.

     

Weak large‐scale population genetic structure in a philopatric seabird,the European Shag Phalacrocorax aristotelis

Quantifying population genetic structure is fundamental to testing hypotheses regarding gene flow, population divergence and dynamics across large spatial scales. In species with highly mobile life‐history stages, where it is unclear whether such movements translate into effective dispersal among discrete philopatric breeding populations, this approach can be particularly effective. We used seven nuclear microsatellite loci and mitochondrial DNA (ND2) markers to quantify population genetic structure and variation across 20 populations (447 individuals) of one such species, the European Shag, spanning a large geographical range. Despite high breeding philopatry, rare cross‐sea movements and recognized subspecies, population genetic structure was weak across both microsatellites and mitochondrial markers. Furthermore, although isolation‐by‐distance was detected, microsatellite variation provided no evidence that open sea formed a complete barrier to effective dispersal. These data suggest that occasional long‐distance, cross‐sea movements translate into gene flow across a large spatial scale. Historical factors may also have shaped contemporary genetic structure: cluster analyses of microsatellite data identified three groups, comprising colonies at southern, mid‐ and northern latitudes, and similar structure was observed at mitochondrial loci. Only one private mitochondrial haplotype was found among subspecies, suggesting that this current taxonomic subdivision may not be mirrored by genetic isolation.     

Movements and behavior of satellite-tagged spotted seals (Phoca largha) in the Bering and Chukchi Seas

Satellite-linked tags were attached to 12 spotted seals (Phoca largha) captured at a coastal lagoon in the eastern Chukchi Sea during August 1991–1993. Movements of seals were tracked for 32–298 days using the Argos system. Of 9,651 total location records obtained, 7,268 were usable. Individual seals were located on 41–96% of the days that tags were operational. During August–November, tagged seals alternated haul-outs at coastal sites lasting 1–304 h with trips to sea of 14–901 h. Coastal haul-outs occurred at 14 sites in western Alaska and eastern Russia. On several trips to sea, seals covered distances of more than 1,000 km. Movement southward from the Chukchi Sea generally began in October, with most of the seals passing through the Bering Strait during November. Seals first hauled out on sea ice in October (Chukchi Sea) or November (Bering Sea), and generally moved southward during October–December as sea-ice coverage increased. Seven seals, whose transmitters were still operating, spent December to June in the Bering Sea region between Kuskokwim Bay and Anadyr Gulf, which corresponded to the location of the ice front. The seals made active east-west movements within the ice front. Spotted seals are unlike other ice-breeding seals in that they regularly use coastal haul-outs during summer and autumn. Compared to the closely related Pacific harbor seal (Phoca vitulina richardsi), spotted seals make much longer trips to sea and spend longer continuous periods at their haul-outs during summer and autumn. Received: 9 April 1997 / Accepted: 30 September 1997     

Fine‐scale movements and interactions of platypuses,and the impact of an environmental flushing flow

1. The platypus is a cryptic mammal that inhabits freshwater streams and rivers of eastern Australia. Tracking the movements of wild platypuses has been notoriously difficult due to the animals' morphology and methodological limitations. Knowledge of fine‐scale movements and interactions among individuals remain particularly poorly understood, as do responses to changes in hydrology.
2. We tracked movements of 15 platypuses (six females, nine males) downstream of the Jindabyne Dam on the Snowy River, using externally attached acoustic transmitters (September–November 2017), to assess spatio‐temporal activity patterns among individuals and changes in movement and activity before and after an environmental flushing flow. As the study took place during the breeding season, we expected to observe overlap in area of activity among males and females, but not among males due to increased territoriality during these months. We also anticipated that a large flow event would impact their activity and foraging behaviour, possibly displacing platypuses downstream.
3. Overlaps in area of activity and temporal co‐occurrence within a pool varied among individuals, with two resident males exhibiting some spatial overlap of activity and varying temporal co‐occurrence, despite tracking during the breeding season. All six tracked females were captured in the same pool and appeared to be residents, possibly highlighting preferences for certain habitats during the breeding months.
4. We found no evidence that the movements of adult platypuses were affected by an environmental flushing flow, with no significant changes to area of activity, number of detections, or daily range of movements. However, foraging duration increased in the week after the flow, possibly associated with increased prey availability.
5. These findings suggest that territoriality between males during and after the breeding season may depend on platypus density and resource availability and that pools with high resource availability may support several breeding females.

     

Avian ecological succession in the Amazon: A long‐term case study following experimental deforestation

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A Comparative Study of the Far Eastern Seas and the Northern Pacific Ocean Based on Integral Parameters of Net Zooplankton in the Epipelagic Layer

Integral parameters of zooplankton community, including species diversity and its components were compared between the Chukchi Sea, Bering Sea, Sea of Okhotsk, Sea of Japan, and adjacent Pacific waters based on the data obtained by standard Juday net with a mouth area of 0.1 m² during the large-scale surveys conducted by the Pacific Fisheries Research Center (TINRO Center) in 1984–2013. These parameters were calculated for the total surveyed area of approximately 7.0 million km² and separately for each of the considered water bodies. In Pacific waters, species richness is higher than that in all the seas, while the concentration of individuals (expressed in terms of abundance, ind./m³) and evenness of their distribution over species were lower. The only sea with a larger mean size of organisms compared to the ocean is the Bering Sea. A lower species diversity than in the ocean has been recorded only from the Chukchi Sea; a lower density (in terms of biomass, g/m³) was determined only from the Sea of Japan. Among the four seas, the Chukchi Sea ranks first in terms of biomass and abundance of zooplankton, second in species evenness, third in the mean size of individuals, and last in species richness and diversity. The Bering Sea ranks first in terms of mean size of plankton organisms, second in species richness, diversity, and biomass, third in abundance, and last in species evenness. The Sea of Okhotsk ranks second in terms of mean size of individuals, last in their abundance, and third in the other parameters. The Sea of Japan ranks first in terms of species richness, evenness, and diversity, second in abundance, and last in mean size of zooplankton organisms, and, therefore, their biomass. The biomass of zooplankton, in accordance with the concentration of nutrients, increases in the southto-north direction (while its absolute abundance depends largely on the size of the body of water). The mean size of organisms increases in the same direction; the evenness of their distribution over species increases in the reverse direction (with the exception of both parameters for the Chukchi Sea). The rank of a water body for its biodiversity coincides with the species richness rank. The latter increases from north to south (except for the Okhotsk Sea), but greatly depends on the surveyed area and, even more, on the surveyed volume of water. A study of the literature data found some unexpected statistically significant relationships of the integral parameters of zooplankton with those of pelagic and bottom macrofauna, as well as with the parameters of zooplankton production, on the size of the considered bodies of water. The causes and the biological meanings of most of these relationships still do not have any rational interpretation. Their testing at other spatial scales will be continued in future works.     

Inter-island movements and population differentiation in a pelagic seabird

We used mark-resight data and amplified fragment length polymorphism (AFLP) markers to assess movements and gene flow between Central Pacific breeding colonies of the great frigatebird, Fregata minor. Of 715 adult frigatebirds marked on Tern Island and Johnston Atoll, 21.3% were resighted at other frigatebird colonies at least 582 km away. Mark-resight data indicated regular movement of males and females between Tern Island and Johnston Atoll (873 km apart), and less frequent movements to other islands; no birds marked on Tern or Johnston were seen on Christmas Island, but one was seen in the Philippines, 7627 km from where it was marked. Despite the regular occurrence of interisland movements, Bayesian analyses of AFLP data showed significant genetic differentiation between Tern Island and Johnston Atoll, and more pronounced differentiation between these two islands and the more distant Christmas Island. The AFLP profiles of three birds breeding on Tern Island fell within the profile-cluster typical for Christmas Island birds, both in a nonmetric multidimensional scaling analysis and in a population assignment test, suggesting dispersal events from Christmas Island to Tern Island. Several factors could explain the persistence of genetic structure despite frequent movements between colonies: many movements occurred during the nonbreeding season, many breeding-season movements did not involve mate-acquisition behaviours and individuals that do disperse may be selected against, as suggested by morphometric differences between colonies. The persistence of genetic structure among breeding colonies despite significant interisland movements suggests limits to the effectiveness of migration as a homogenizing force in this broadly distributed, extremely mobile species.     

Ontogenetic and spatial variability in trophic biomarkers of juvenile saffron cod (<Emphasis Type="Italic">Eleginus gracilis</Emphasis>) from the Beaufort,Chukchi and Bering Seas

Climate models indicate the Arctic will undergo dramatic environmental change with forecasted increases in temperature and river runoff. Saffron cod (Eleginus gracilis) is abundant in nearshore waters and appears in the diet of many Arctic sea birds and marine mammals; however, little is known about its early ecology and consequently how they might be affected by environmental changes. We aimed to characterize the mechanisms of spatial and ontogenetic variation in trophic biomarkers (lipid classes, fatty acids and bulk C and N stable isotopes) of saffron cod from the Western Arctic, Chukchi and Bering Seas. Size-standardized analyses showed a significant difference in lipid condition metrics and trophic biomarkers as a function of survey location. Both ontogeny and sampling location played an important role in determining lipid stores with elevated levels in both small offshore juveniles (<55 mm) and larger inshore juveniles (>75 mm). Higher lipid storage in Arctic juveniles was associated with elevated levels of diatom fatty acid markers, but not with nearshore carbon input. Increased lipids were found in age-1 juveniles from Prudhoe Bay in the Western Beaufort that were feeding at a lower trophic level than similarly sized age-0 juveniles from surface trawls in the Bering Sea. The use of otolith annuli revealed two discrete patterns of growth that help explain the trade-offs between energy storage and rapid growth that diverge between the Arctic and Bering Sea. Laboratory temperature-growth experiments confirmed that saffron cod have a eurythermal growth response and are able to store excess lipids at temperatures as high as 20 °C.     

Six steps towards operationalising freshwater ecoacoustic monitoring

1. Applications in bioacoustics and its sister discipline ecoacoustics have increased exponentially over the last decade. However, despite knowledge about aquatic bioacoustics dating back to the times of Aristotle and a vast amount of background literature to draw upon, freshwater applications of ecoacoustics have been lagging to date.
2. In this special issue, we present nine studies that deal with underwater acoustics, plus three acoustic studies on water-dependent birds and frogs. Topics include automatic detection of freshwater organisms by their calls, quantifying habitat change by analysing entire soundscapes, and detecting change in behaviour when organisms are exposed to noise.
3. We identify six major challenges and review progress through this special issue. Challenges include characterisation of sounds, accessibility of archived sounds as well as improving automated analysis methods. Study design considerations include characterisation analysis challenges of spatial and temporal variation. The final key challenge is the so far largely understudied link between ecological condition and underwater sound.
4. We hope that this special issue will raise awareness about underwater soundscapes as a survey tool. With a diverse array of field and analysis tools, this issue can act as a manual for future monitoring applications that will hopefully foster further advances in the field.

     

Theoretical habitat templets, species traits, and species richness: Trichoptera in the Upper Rhône River and its floodplain

• 1 For Trichoptera occurring in two sites of the Upper Rhône River (France) we examine: (i) relationships among species traits; (ii) habitat utilization of Trichoptera species; (iii) the relationship between species traits and habitat utilization; (iv) trends of species traits in the framework of spatial–temporal habitat variability to test predictions of the habitat templet concept; and (v) trends of species richness in the framework of spatial–temporal habitat variability to test predictions of the patch dynamics concept.
• 2 Of the sixteen species traits selected, twelve have high correlation ratios for the seventy-five species used in this analysis; these traits are related to behavioural, morphological, or physiological aspects. Traits related to reproduction or life cycle have lower correlation ratios.
• 3 An ordination by species traits separates the five main families into three groups: (i) Hydropsychidae and Polycentropodidae; (ii) Hydroptilidae; and (iii) Leptoceridae and Limnephilidae. An ordination of the habitat utilization of the species in ten habitats indicates that the Hydropsychidae occur preferentially in the main channel, Hydroptilidae, Polycentropodidae, and Limnephilidae occur in backwaters or oxbow lakes, and the Leptoceridae are ubiquitous.
• 4 The Hydropsychidae exhibit a relationship between species traits and habitat utilization, i.e. they use similar habitat types with similar species traits. The species traits of the other four families are similar but their habitat utilization is quite different.
• 5 The Hydropsychidae occur in lowest spatial–temporal variability habitats and Limnephilidae in the highest. Therefore, net spinners and filterers are characteristic of habitats with a low spatial–temporal variability, whereas shredders and case makers using plant material are characteristic of habitats with high spatial–temporal variability. The trends in species traits show little agreement with trends predicted from the river habitat templet.
• 6 Trends of species richness in the framework of spatial and temporal variability do not follow the predictions of the patch dynamics concept because richness is similar in all superficial habitats. This implies that each habitat, in spite of large differences in their spatial and temporal variability, offers Trichoptera a similar but limited number of ecological niches.

     

Stratigraphic distribution of the radiolarian Spongodiscus biconcavus Haeckel at IODP Site U1340 in the Bering Sea and its paleoceanographic significance

The temporal and spatial distributions of the radiolarian species Spongodiscus biconcavus Haeckel are investigated to understand the paleoceanographic evolution of the Bering Sea region during the last 4.3 Myr based on extensive study of samples collected at Site U1340 during the IODP Expedition 323. The biostratigraphic resolution for the region is also improved by multidisciplinary studies of radiolarians, diatoms, dinoflagellates, ebridians, and silicoflagellates. The results demonstrate that the abundance variation of S. biconcavus during the last 4.3 Myr is closely related to global climate changes, and the species can be used as a warm water and climate proxy in the Bering Sea. Based on the downhole profiles of S. biconcavus and other parameters, we conclude that the southern Bering Sea was associated with a warm water mass prior to 3.147 Ma but it gradually cooled thereafter. From 2.793 Ma to 0.889 Ma, a cold water mass and sea-ice predominated in the Bering Sea, in response to the early Northern Hemisphere glaciation (NHG). Furthermore, the climate suddenly became much cooler post 0.889 Ma. Nevertheless, a reversal of this cooling trend occurred after the Mid-Pleistocene Climatic Transition (∼1.2 Ma), marked by reoccurrence of warm water and reduced sea-ice in the Bering Sea until the final retreat of warm water mass from the Bering Sea after 0.239 Ma. These processes are correlated with biogeographic expansion and retreat of warm water planktonic species.     

Long-term climate-related changes in somatic growth and population dynamics of Hokkaido chum salmon

We used multiple regression and path analysis to examine the effects of regional and larger spatial scales of climatic/oceanic conditions on the growth, survival, and population dynamics of Hokkaido chum salmon (Oncorhynchus keta). Variability in the growth of chum salmon at ages 1 to 4 was estimated from scale analysis and the back-calculation method using scales of 4-year-old adults returning to the Ishikari River in Hokkaido, Japan, during 1943–2005. Growth of chum salmon at age 1 was less during the period from the 1940s to the mid-1970s compared to the period from the mid-1980s to the present. On the other hand, growth of chum salmon at ages 2, 3, and 4 has declined since the 1980s. Path analysis indicated that growth at age 1 in the Okhotsk Sea was directly affected by warmer sea surface temperatures associated with global warming. The increased growth at age 1 led directly to higher survival rates and indirectly to larger population sizes. Subsequently, in the Bering Sea, the larger population size was directly associated with decreased growth at age 3 and indirectly associated with shorter adult fork lengths despite the lack of relationships among sea surface temperature, zooplankton biomass, and growth at ages 2 to 4. Therefore, higher growth at age 1 related to global warming positively affected the survival rate of juvenile chum salmon in the Okhotsk Sea. The higher survival rates in turn appear to be causing a population density-dependent effect on growth at ages 2 to 4 and maturation in the Bering Sea due to limited carrying capacity.