Small Individuals Research Articles

Insights into Ontogenetic Niche Changes in Bluegill, Lepomis macrochirus, Applying Combined Analyses of Stomach Content and Stable Isotopes

We integrated stomach content analysis (SCA) and stable isotope analysis (SIA) to understand ontogenetic niche shifts in the invasive freshwater fish, bluegill, Lepomis macrochirus, inhabiting the Yedang Reservoir in Korea. Based on the total length (TL), we classified L. macrochirus as small (23–57 mm), medium (61–99 mm), or large (100–163 mm). Across all study sites, the index of relative importance (IRI) of zooplankton was high for small individuals, whereas those of benthic macroinvertebrates were high for the medium and large groups. Isotopic niche width estimates based on carbon and nitrogen isotope ratios (δ space) also increased with growth, indicating an ontogenetic niche shift in L. macrochirus. In particular, the δ space and diet plasticity of large fish was higher in the littoral population, implying L. macrochirus are generalist feeders as adults. Individuals classified as small showed confined and constant δ space, regardless of habitat condition. Thus, together with the results on the significantly high IRI of zooplankton, these individuals seem to have strong specialistic feeding ecology. Our study demonstrates the applicability strength of combining SCA and SIA for ecological niche research by providing clear evidence of an ontogenetic niche shift in L. macrochirus and elucidates their feeding ecology.

Seasonal changes in the reproductive cycle and condition index of the surf clam Mactra stultorum (Mollusca: Bivalvia) in the Gulf of Gabes, Tunisia

The reproductive biology of Mactra stultorum from the Gulf of Gabes was investigated monthly during a oneyear period (2017). This study is the first study examining its reproductive biology during one-year in the south of Tunisia. The overall samples presented a balanced sex ratio, with males dominating among smaller individuals (< 22 mm) and females predominating in larger size classes (> 34 mm). The obtained total sex ratio (F:M) was equal to 1.03:1. The size at first maturity (SL50%) was 20.43 and 22.10 mm for males and females, respectively. The seasonal variations assessed through macro- and microscopic characteristics in the gonads of both sexes indicated a clearly defined annual reproductive cycle with a principal spawning peak during summer and a resting period during December and January. The reproduction of M. stultorum was strongly influenced by fluctuations in the seawater temperature, as reflected through the temporal variation in the gonadal cycle, condition index (CI) and tissue weight rate (TiWR). If managed properly, M. stultorum is expected to meet the domestic market demand through artisanal fishery. The adoption and implementation of rules, such as limiting the size of clams, is required to protect this new exploitable fishery resource.

Within‐lake variatiability in predation risk shapes the spatio‐temporal structure of the zooplankton community

Abstract While it is well‐accepted that predation plays a key role in shaping both size structure and species composition in natural ecosystems, fine‐scale variation in predation risk within ecosystems has been largely neglected. The objective of this study was to use normalised size spectra (NSS) to investigate whether small‐scale spatial variation in predation risk (by fish) can modulate zooplankton community structure at the within‐lake level in a small temperate lake. We tested the difference in the NSS between two hydrologically well‐connected basins of a lake exhibiting contrasting thermal regimes. The first is a well‐mixed shallow basin (max. depth 2.5 m) that is inaccessible to brook charr (Salvelinus fontinalis) during summer because the temperature is too warm. The second is a deeper basin (max. depth 18 m) offering a thermal refuge during summer because of lake stratification. As a consequence of these differences in fish accessibility, the fishless basin should contain larger and more abundant zooplankters, inducing a change in NSS slope and height. Our results showed that both the zooplankton size structure and taxonomic composition were distinct in the two basins, with a higher proportion of small individuals and a higher abundance of zooplankton in the shallow basin compared to the deep one. Furthermore, following cooling of the epilimnion in late summer, the zooplankton communities of both basins exhibited a clear shift in size structure and species composition: in autumn, there were smaller individuals and larger proportions of Bosminidae and Daphniidae compared to colonial rotifers than in summer. These results suggest a potential effect of the change in the spatial distribution of brook charr which feed preferentially on large individuals, reducing the average body size of the zooplankton community. Our results show that predation risk by fish can induce a spatial and temporal variation in zooplankton community structure within small temperate lake ecosystems exhibiting contrasted thermal regimes. Other potential predators also influenced the zooplankton community structure, creating a complex interplay that has to be taken into account to disentangle ecological processes and predict their future changes.

Timing is everything: Improving predictions of winter New Zealand grass grub densities and associated damage from summer and autumn larval counts

Costelytra giveni is a serious pasture pest in New Zealand and accurate estimates of population densities are important to inform control measures. This species generally has a one-year life cycle so populations should either remain stable after eggs have hatched or decline due to larval mortality. Larval counts were obtained using a simple, standard and widely used sampling method from a series of soil cores collected from ryegrass research plots in Canterbury, New Zealand between 27 January and 16 June 2021 and a significant increase in population was recorded. Measurements on 27 January, 19 March and 5 May, represented only c. 8%, 25% and 63% of the mean densities measured on 16 June, respectively. The apparent increase in larvae is attributed to failure to find small 1st and 2nd instar individuals within the soil samples. Larvae increased in size as they transitioned from 1st to 3rd instar and later instar specimens were more easily discovered. An equation to describe the observed results provided date-related correction factors to allow a more realistic prediction of C. giveni larval densities in the winter following empirical larval counts. Larval counts measured on 27 January, 19 March, and 5 May, would need to be multiplied by 13, 4 and 1.6, respectively, to accurately estimate the larval density found on 16 June. This study showed that summer-autumn sampling using the current method can significantly underestimate winter C. giveni larval densities, potentially leading to unanticipated pasture production losses. Similar results were also found in 2022. While the equation provides a guide to population estimates, the caveat is that region and environment will influence population trends in any particular year.

Seasonal pigment fluctuation in diploid and polyploid Arabidopsis revealed by machine learning-based phenotyping method PlantServation

Long-term field monitoring of leaf pigment content is informative for understanding plant responses to environments distinct from regulated chambers but is impractical by conventional destructive measurements. We developed PlantServation, a method incorporating robust image-acquisition hardware and deep learning-based software that extracts leaf color by detecting plant individuals automatically. As a case study, we applied PlantServation to examine environmental and genotypic effects on the pigment anthocyanin content estimated from leaf color. We processed >4 million images of small individuals of four Arabidopsis species in the field, where the plant shape, color, and background vary over months. Past radiation, coldness, and precipitation significantly affected the anthocyanin content. The synthetic allopolyploid A. kamchatica recapitulated the fluctuations of natural polyploids by integrating diploid responses. The data support a long-standing hypothesis stating that allopolyploids can inherit and combine the traits of progenitors. PlantServation facilitates the study of plant responses to complex environments termed “in natura”.

Habitat and distribution of the red decorator crab, Schizophrys aspera, a cryptic crown-of-thorns seastar predator

Abstract Cryptic species and their interactions are challenging to describe owing to the difficulties in observing and sampling their populations. Such methodological hurdles are critical to resolve, especially when important interactions involving poorly described species are detected. The red decorator crab, Schizophrys aspera, is a newfound predator of the corallivorous Pacific crown-of-thorns seastar (CoTS; Acanthaster sp.). We discuss the Indo-Pacific distribution and taxonomy of S. aspera and provide characterization of its cryptic population at sites around Heron Island, Great Barrier Reef, that differ in CoTS densities. Most S. aspera (>95%) were found under coral rubble pieces atop existing rubble, associated with large pieces and chasmic interstices. The three smallest individuals (carapace width: 5–11 mm) were found under rubble overlying sand. Mean density of S. aspera was 0.8 ± 0.2 ind. 100 m−2, which varied among sites. Areas with lower records of CoTS had higher densities of S. aspera (p = 0.002; R2 = 0.25), which justifies evaluation of the distribution and impact of this species in context of CoTS outbreaks. We present a method to survey cryptic decapods on coral reefs, along with microhabitat characteristics to help predict S. aspera on reefs prone to CoTS outbreaks and its capacity to act as a natural top-down control mechanism.

Horizontal prey distribution determines the foraging performance of short‐ and long‐billed waders in virtual resource landscapes

When waders gather in mixed‐species flocks to feed on benthic prey, differences in morphological traits, foraging strategies and prey selection may allow different species to optimize their energy intake while reducing competition. As the effect of the fine‐scale spatial distribution of resources on energy intake is unknown, we simulated the foraging performance of two types of waders with contrasting body plans and foraging strategies in a variety of virtual mudflats with different horizontal and vertical prey distribution patterns. Although larger, longer‐billed individuals had higher energy intake rates, smaller individuals with shorter bills maintained higher prey capture rates by relocating if prey was insufficiently available. Shorter‐billed individuals struggled more to meet their energetic demands because they selected smaller prey items and had a more limited capacity to metabolize energy from food. Being able to catch larger, high‐quality prey offered a competitive advantage for longer‐billed individuals, which could be a driving force for the evolutionary lengthening of bills in waders. Interestingly, their performance was more affected by the horizontal than by the vertical prey distribution. Quantifying prey distributions may help explain how some wader species can co‐occur in the field and why some wetland areas are unattractive as foraging areas. The work confirms that the foraging performance of larger, longer‐billed birds is not limited by bill size per se, but by the energetic trade‐offs associated with the ability to catch larger prey items more efficiently, increased handling times and higher absolute energy costs. These trade‐offs may become particularly important in landscapes where prey is scarce and spatially patchy.

Juvenile sparids (Rhabdosargus holubi) consistently select structurally dense vegetated habitat in nursery seascapes.

Seagrass habitats provide structural complexity in coastal estuarine and marine environments, which offer fish optimal foraging grounds and refuge from predation. However, seagrasses are some of the most threatened ecosystems globally, with anthropogenic activities such as population growth and environmental degradation leading to the fragmentation, thinning, and loss of these habitats. Rhabdosargus holubi is one of only a few vegetation-associated marine fish species in South African estuaries. Although field studies have shown a strong association with seagrass over other aquatic vegetation for the juveniles of this species, habitat choice has never been empirically tested. Here, we used artificial vegetation units to test habitat choice (different structural complexities) for this species. We also tested whether habitat choice is influenced by a predatory threat, with fish preferentially selecting dense habitat in the presence of a predator and whether this effect may be more apparent in smaller individuals. We found that R. holubi significantly prefer greater structural complexity over less complex habitats, in both the absence and presence of a predator and for both small and large juveniles, showing that R. holubi actively choose more complex structures and are attracted to the structure per se irrespective of the threat of predation. This study highlights the importance of dense seagrass as nursery areas for this species and demonstrates how the loss of these habitats could impact the nursery function of estuaries.

Pachyoliva columellaris G.B. Sowerby I, 1825 (Olividae, Caenogastropoda) in Peru: tidal migrations and population density

The gastropod Pachyoliva columellaris (formerly Olivella columellaris) is particularly common on many sandy beaches in North Peru. In the studied region north of Paita, Piura province, the species reaches densities of over 80000 individuals per beach meter. The snails perform tidal migrations throughout the lunar cycle although tidal amplitudes differ four-fold between neap and spring tide. Not all animals complete their tidal migrations, and significant numbers remain above the water line at low tide. Throughout the tidal cycle, the proportion of small individuals is increased near the water line whereas large animals dominate in lower beach zones. I conclude that the sandy beaches north of Paita are well-suited for further studies of P. columellaris and the mechanisms underlying tidal migrations in invertebrates.

THE LEGAL FRAMEWORK FOR SMALL TRADERS IN ALGERIAN COMMERCIAL LEGISLATION

It is no different that commercial work was at its beginning a simple work done by individuals (natural persons), then it increased in expansion in size and territory until merchants were able to introduce the denominations system, and with the beginnings of the emergence of commercial companies, the commercial law focused on small projects for private individuals, under the influence of the general provisions of the law The civil (individuals law) where the state extracted from them the organization of large projects for fear of the tyranny of large merchants over the systems of government, so the joint stock companies were organized as they require huge sums in the form of decrees, and perhaps this influence still exists although it has become less severe in our time. The Committee on International Trade Law of the United Nations has called on more than one occasion to pay attention to small traders through the approach of "thinking on a small scale first" and called on developing countries in particular to include, recognize and support them in the various legal texts regulating them. It goes without saying that the Algerian commercial law is the regulator of the principles and rules of trade with all its actors: merchants, their obligations, commercial activities, etc. However, these principles and texts are often general without specification (registration in the commercial registry, commercial and accounting bookkeeping...) as they apply to all Merchants without specifying, and the special legal texts regulating commercial life have recently known accelerating rates. Or is it not fair to reconsider this generality by adopting legal texts for small traders, individuals or companies, with regard to obligations? With an explanation of how? Is this legislative richness or is it a place of contradiction and contradiction of provisions? Accordingly, the researcher suggests the need to reconsider the provisions of the Algerian commercial law by granting privacy to this category in terms of activity, incorporation, reduction or exemption from obligations and the proposed alternatives? As well as the privileges thatmay be enjoyed by small traders,individuals and companies,to develop their activity in support of the national economy, and to call on the Algerian legislator to recognize the individual small trader and strengthen the position of the small trader as a legal person, while ensuring that the texts governing small and emerging commercial companies meet the principles of governance

Complete mitochondrial genome and phylogenetic analysis of Kapsa arca and Alnetoidia dujuanensis (Hemiptera, Cicadellidae, Typhlocybinae, Erythroneurini) from the Karst region

Kapsa arca and Alnetoidia dujuanensis, which belong to erythroneurine leafhoppers (Cicadellidae and Typhlocybinae), are economic pests with the characteristics of a large number of small individuals and wide distribution. Analysis of the complete mitochondrial genome sequence and phylogenetic relationships of the leafhopper will help not only in its identification but also in its control. In this work, two mitochondrial gene sequences from K. arca and A. dujuanensis were sequenced, analyzed, and used to explore the phylogenetic relationships of the tribe. The lengths of the K. arca and A. dujuanensis genomes were 15,594 bp and 15,375 bp, respectively, and all contained a noncoding control region, two ribosomal RNAs (rRNAs), 22 transfer RNAs (tRNAs), and 13 PCGs. Most protein-coding genes end with TAA or TAG and start with ATN, with AT skew exhibiting a positive skew and GC skew exhibiting a negative skew. The mitotic genomes of K. arca and A. dujuanensis are similar in structure to those of other leafhoppers and are conserved. Phylogenetic analysis revealed that K. arca forms a sister group with Elbelus tripunctatus, and A. dujuanensis forms a sister group with Kaukania anser, but Zyginellini and Typhlocybini, which should branch separately, are interrelated and cannot form separate branches. The result differs from previous studies. The results indicated that the two species, K. arca and A. dujuanensis, should belong to the same tribe, the Erythroneurini leafhoppers, but should be grouped into different genera. A time-calibrated phylogeny estimated the earliest divergence time of Erythroneurini, Empoascini, Typhlocybini, and Zyginellini.

Ontogenetic Shifts in Body Morphology of Demersal Sharks' Species (Order: Squaliformes) Inhabiting the Western-Central Mediterranean Sea, with Implications for Their Bio-Ecological Role.

Several elasmobranch species undergo shifts in body proportions during their ontogenetic growth. Such morphological changes could reflect variation in diet, locomotion, or, more broadly, in the species' interactions with their environment. However, to date, only a few studies have been conducted on this topic, and most of them focused on particular body regions. In the present study, the ontogenetic growth of five different demersal shark species was investigated by using both traditional linear morphometry of the entire body and shape analysis of the caudal fin. A total of 449 sharks were analysed: 95 little gulper sharks, 80 longnose spurdogs, 103 kitefin sharks, 124 velvet belly lanternsharks, and 47 angular roughsharks. From each specimen, 36 linear morphometric measurements were taken. While a first canonical analysis of principal coordinates ruled out the possibility of different growth patterns between males and females, the same analysis statistically discriminated between small and large individuals in every species based on their morphology. A Similarity Percentage analysis revealed that the most important measurements in distinguishing these two groups were those related to body lengths, indicating that large individuals are more elongated than small individuals. The shape analysis of caudal fins revealed allometric growth during ontogenetic development, with adult individuals having a wider fin (discriminant analysis, p < 0.05). These findings could be related to changes in predatory skills, supporting the hypothesis of a shift in the ecological role that these sharks play in their environment, thus providing new essential information for their conservation.

Body mass is associated with hibernation length, body temperature, and heart rate in free-ranging brown bears

BackgroundDespite centuries of research, debate remains on the scaling of metabolic rate to mass especially for intraspecific cases. The high variation of body mass within brown bears presents a unique opportunity to study the intraspecific effects of body mass on physiological variables. The amplitude of metabolic rate reduction in hibernators is dependent on body mass of the species. Small hibernators have high metabolic rates when euthermic but experience a drastic decrease in body temperature during torpor, which is necessary to reach a very low metabolic rate. Conversely, large hibernators, such as the brown bear (Ursus arctos), show a moderate decrease in temperature during hibernation, thought to be related to the bear’s large size. We studied body mass, abdominal body temperature, heart rate, and accelerometer-derived activity from 63 free-ranging brown bears (1–15 years old, 15–233 kg). We tested for relationships between body mass and body temperature, heart rate, and hibernation duration.ResultsThe smallest individuals maintained lower body temperatures during hibernation, hibernated longer, and ended hibernation later than large bears. Unlike body temperature, winter heart rates were not associated with body mass. In summer, the opposite pattern was found, with smaller individuals having higher body temperature and daytime heart rates. Body mass was associated with body temperature in the winter hypometabolic state, even in a large hibernating mammal. Smaller bears, which are known to have higher thermal conductance, reached lower body temperatures during hibernation. During summer, smaller bears had higher body temperatures and daytime heart rates, a phenomenon not previously documented within a single mammalian species.ConclusionWe conclude that the smallest bears hibernated more deeply and longer than large bears, likely from a combined effect of basic thermodynamics, the higher need for energy savings, and a lower cost of warming up a smaller body.

Variation of 210-polonium in the cephalopod community from the Bay of Biscay, North-East Atlantic

Among natural radionuclides, 210Po is the major contributor to the radiation dose received by marine organisms. In cephalopods, 210Po is concentrated in the digestive gland, which contains over 90% of the whole-body burden of the nuclide. Although previous studies showed that 210Po was taken up independently of 210Pb, its parent nuclide, very little is known about the factors influencing its levels in cephalopods. To the best of our knowledge, no studies investigated 210Po levels in different species at the same time. In the present study, 210Po was analysed in the digestive gland of 62 individuals from 11 species representing a large range of feeding ecologies and habitats, including squids, cuttlefish and octopus species from coastal to deep-oceanic habitats. Among species, the highest activity was measured in Loligo vulgaris (5720 ± 3606 Bq/kg) and the lowest in T. megalops (188 Bq/kg). However, considering the habitats (benthic vs pelagic and neritic vs oceanic), no significant differences appeared. At the species level, no differences between sexes were found so both sexes were plotted together to test the size effect for species with at least 8 individuals (i.e., Eledone cirrhosa, L. vulgaris, L. forbesi and Sepia officinalis). In the first three species, 210Po levels decreased significantly with increasing size or weight but not in S. officinalis. In squid, this could be related to ontogenetic changes in diet from a high proportion of crustaceans (high Po content) in small individuals to fish (low Po content) in larger individuals, while the high dietary plasticity of S. officinalis at all stages of its life cycle could explain the lack of decrease in 210Po with size. In comparison to the few data from the literature, the levels of 210Po concentrations in the cephalopod community of the Bay of Biscay were overall in the same range than those reported in other cephalopods, varying across 4 orders of magnitude. Further studies are needed to understand the mechanism of retention in the cephalopod digestive gland.

Ontogenetic changes in green turtle (Chelonia mydas) diet and home range in a tropical lagoon

Ontogenetic changes in habitat and diet are widespread among marine species. Most species of sea turtles are characterized by extreme ontogenetic changes in habitat use and diet, with large changes occurring in early developmental stages (e.g., neonates to juveniles). Changes can continue even after recruitment to shallow coastal habitats. In places where substantial transitions in habitat occur across short distances, it is possible that the distances of developmental movements from one habitat to another could be short. We investigated ontogenetic changes in home range size, home range location and diet of Chelonia mydas in a tropical coastal lagoon in north-western Australia by combining acoustic telemetry with stable isotope analysis. There was a substantial (but nonlinear) increase in home-range size (kernel utilization distribution: KUD) with length, and an increase in the average distance of the center of home ranges from shore with length: larger turtles tended to occupy larger areas further from the shore. These patterns were accompanied by complex nonlinear changes in δ13C, δ15N and δ34S of red blood cells and nails; changes were rapid from 36 cm (the length of the smallest individual captured) to 50 cm, before reversing more gradually with increasing size. δ15N and δ34S (but not δ13C) of red blood cells and nails increased monotonically with KUD and distance from shore. Seagrass was likely an important food for all sizes, macroalgae was potentially important for small (&amp;lt; 60 cm CCL) individuals, and the proportion of scyphozoan jellyfish in diet increased monotonically with size. The combination of acoustic telemetry and stable isotope analysis revealed ontogenetic shifts in use of space and diet across short distances in a tropical coastal lagoon.

Seasonal Changes in Vertical Distribution and Population Structure of the Dominant Hydrozoan Aglantha digitale in the Western Subarctic Pacific

Hydrozoans are numerically dominant taxa in gelatinous zooplankton communities of the worldwide oceans and play an energy transfer role connecting primary producers and higher trophic level organisms. In the western subarctic Pacific, St. K2 has been established as a long-term time-series monitoring station. Various studies on zooplankton have been conducted, while hydrozoans have not been treated. This study presents the abundance, vertical distribution, and population structure of the dominant hydrozoan species (Aglantha digitale) at St. K2. Samples collected by vertical stratification samplings from eight layers of 0–1000 m both day and night during four seasons in one year. Hydrozoans occur throughout the year. The annual mean abundance of A. digitale was 198.4 ind. m−2 and composed of 91.9% of hydrozoans. The vertical distribution of A. digitale was concentrated for the epipelagic layer (0–200 m), both day and night of the most season. The bell height (BH) of A. digitale ranged between 2.4–18.9 mm. Most of the mature individuals, with gonad length larger than 10% of BH, occurred only in July. The BH of mature individuals ranged from 4.7 to 17.6 mm, with the BH of most mature individuals were larger than &gt;10 mm. Through observation on BH at each sampling layer, small individuals with BH &lt; 6 mm were distributed below 300 m depths throughout the seasons, expanding their vertical distribution to the deeper layers. Inter-region comparison of abundance, maturation body size, and generation length of A. digitale revealed that these parameters are varied with the region and depend on the marine ecosystem structures.

The state of crowdfunding in Africa and its potential impact: a literature review

The purpose of this review is to shed light on the current state of crowdfunding and its possible effects on African communities. The goal of this article is to give a narrative overview of how crowdfunding has evolved, along with trends, challenges, and potential effects on African communities. Despite recent advancements in the usage of mobile technology on the continent, the growth of crowdfunding based on internet platforms has been quite gradual. According to research, the success of crowdsourcing initiatives in Africa depends on a hybrid strategy that involves the "offline" network of backers. The majority of research concluded that the biggest barriers to the growth of crowdfunding in Africa were a lack of knowledge and trust in public institutions, lax laws protecting the rights of backers and ensuring transparency, as well as technology (internet connection). Also mentioned was the possibility that significant cultural aspects of offline crowdfunding, if taken into consideration, would make it easier for African business owners to adopt the practice. It has lagged behind other continents in the use of crowdfunding to raise money for small businesses or individuals, which could also help with financial inclusion in Africa, either directly for individuals or by sponsoring small enterprises. It is necessary to have a regulatory framework that promotes technological advancement while also reducing crime and fraud. Additionally, establishing platforms based on continents and creating synergies with existing financial actors would raise awareness, boost confidence, and whet interest in using them.

Analysis of Social Support, Customer Review Quality, Social Commerce Trust on E-Commerce Satisfaction Study Tokopedia in Indonesia

This study aims to determine how social support, customer review quality, social commerce trust, and e-commerce satisfaction are at Tokopedia Indonesia. The authors choose Tokopedia because Tokopedia is an e-commerce from Indonesia and is influential not only in Indonesia but in Southeast Asia. Tokopedia also supports Micro, Small, and Medium Enterprises and individuals to develop their businesses by marketing their products online with the Government and other parties. The method used for this research is quantitative. It was then analyzed using the PLS technique, factor analysis, and hypothesis testing. The unit of analysis in this study is the consumer from Tokopedia. The data support hypothesis H1 that social support has a positive effect on social commerce trust, H2 supports the hypothesis that customer review quality has a positive influence on social commerce trust, as well as H3 supports the idea that social commerce trust has a positive effect on e-commerce satisfaction.

Relationship between cell volume and particulate organic matter for different size phytoplankton

Phytoplankton biomass is an intuitive indicator to evaluate the stability of marine ecosystems. How to obtain phytoplankton biomass quickly and accurately is the focus of marine research. In this work, we selected 12 phytoplankton species to explore the relationship between cell volume and cellular compounds. Results indicated that the volume of 12 species spanned 6 orders of magnitude from 0.11 μm3 (Synechococcus sp. XM-5) to 1.26 × 105 μm3 (Ditulum brightwellii). Besides, a strong negative linear correlation between cell abundance and volume was observed. For per-cell of phytoplankton, the log-log relationship between cell volume and particulate organic carbon (POC), particulate organic nitrogen (PON), chlorophyll a (Chl-a) results reflected a positive correlation. On the contrary, the density of cellular compounds (POC, PON and Chl-a) presented a negative correlation in cell volume. In addition, for ratio of particulate organic carbon and particulate organic nitrogen (C/N), the average value was 5.46, diatoms had the lowest values, 4.72. Moreover, the ratio of carbon and chlorophyll a (C/Chl-a) varied from 15.09 to 79.75, indicating that the C/Chl-a values affected by the different categories. Meanwhile, diatoms usually have a lower C/Chl-a value for their special structure. Finally, we excluded the Synechococcus group of small individuals and found that the slope of their corresponding carbon-volume relationship was not very different, indicating that the smaller individuals had no effect on the assessment of carbon-volume relationship. The physiological variation, based on the cell volume, provides us with a new perspective to simplify the relationship between carbon and volume, and further simplify the methods and analysis of experiments and model simulations of ecosystem biological rate and flux.

Movement diversity and partial sympatry of coastal and Northeast Arctic cod ecotypes at high latitudes.

Movement diversity within species represent an important but often neglected, component of biodiversity that affects ecological and genetic interactions, as well as the productivity of exploited systems. By combining individual tracking data from acoustic telemetry with novel genetic analyses, we describe the movement diversity of two Atlantic cod Gadus morhua ecotypes in two high-latitude fjord systems: the highly migratory Northeast Arctic cod (NEA cod) that supports the largest cod fishery in the world, and the more sedentary Norwegian coastal cod, which is currently in a depleted state. As predicted, coastal cod displayed a higher level of fjord residency than NEA cod. Of the cod tagged during the spawning season, NEA cod left the fjords permanently to a greater extent and earlier compared to coastal cod, which to a greater extent remained resident and left the fjords temporarily. Despite this overall pattern, horizontal movements atypical for the ecotypes were common with some NEA cod remaining within the fjords year-round and some coastal cod displaying a low fjord fidelity. Fjord residency and exit timing also differed with spawning status and body size, with spawning cod and large individuals tagged during the feeding season more prone to leave the fjords and earlier than non-spawning and smaller individuals. While our results confirm a lower fjord dependency for NEA cod, they highlight a movement diversity within each ecotype and sympatric residency between ecotypes, previously undetected by population-level monitoring. This new knowledge is relevant for the management, which should base their fisheries advice for these interacting ecotypes on their habitat use and seasonal movements.