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The Panchthar–Ilam–Taplejung Corridor in Eastern Nepal, managed through community forestry, is a crucial habitat for the Himalayan red panda, an endangered carnivore threatened by forest degradation and illegal trade. We deployed the altitude line intercept and ten-tree plotless methods to evaluate the distribution of Himalayan red pandas and the environmental factors affecting them within four community forests, namely Singhadevi, Chitre-Hile, Chhipchhipe, and Kalikhop-Dadehli, of the corridor. We established a total of 23 transects and 92 plots, identifying 41 plots with evidence of the Himalayan red panda's presence. The sign occurrence revealed a clumped distribution of the species across all four community forests. The Himalayan red panda signs were observed between 2200 m and 2700 m above sea level (asl) and the majority of them were from habitats with a moderate slope within elevations of 2400 m to 2500 m asl. The primary sites for the defecation were large horizontal tree branches (78.12%), followed by forest ground (15.62%) and rocks (6.25%). The dominant tree species in their habitats included Lithocarpus pachyphylla (Importance value index, IVI = 45.05), Symplocus theifolia (IVI = 37.19), Symplocos pyrifolia (IVI = 20.99), Quercus lamellosa (IVI = 19.25), and Magnolia campbellii (IVI = 17.25). Among the thirteen environmental variables examined, proximity to water, distance to road, bamboo density, and Normalized Difference Vegetation Index were identified as the major factors influencing the Himalayan red panda's distribution. This research provides crucial insights to develop site-specific habitat management plans for community forestry. [ABSTRACT FROM AUTHOR]

The Panchthar–Ilam–Taplejung Corridor in Eastern Nepal, managed through community forestry, is a crucial habitat for the Himalayan red panda, an endangered carnivore threatened by forest degradation and illegal trade. We deployed the altitude line intercept and ten-tree plotless methods to evaluate the distribution of Himalayan red pandas and the environmental factors affecting them within four community forests, namely Singhadevi, Chitre-Hile, Chhipchhipe, and Kalikhop-Dadehli, of the corridor. We established a total of 23 transects and 92 plots, identifying 41 plots with evidence of the Himalayan red panda’s presence. The sign occurrence revealed a clumped distribution of the species across all four community forests. The Himalayan red panda signs were observed between 2200 m and 2700 m above sea level (asl) and the majority of them were from habitats with a moderate slope within elevations of 2400 m to 2500 m asl. The primary sites for the defecation were large horizontal tree branches (78.12%), followed by forest ground (15.62%) and rocks (6.25%). The dominant tree species in their habitats included Lithocarpus pachyphylla (Importance value index, IVI = 45.05), Symplocus theifolia (IVI = 37.19), Symplocos pyrifolia (IVI = 20.99), Quercus lamellosa (IVI = 19.25), and Magnolia campbellii (IVI = 17.25). Among the thirteen environmental variables examined, proximity to water, distance to road, bamboo density, and Normalized Difference Vegetation Index were identified as the major factors influencing the Himalayan red panda’s distribution. This research provides crucial insights to develop site-specific habitat management plans for community forestry.

Live capture-recapture is often considered the gold standard for estimating wildlife population size or density, but the approach can be limited by permitting requirements, required labor, welfare concerns, and biased estimates resulting from heterogeneity in individual behavior. Noninvasive genetic sampling (e.g., from fecal pellets) offers a powerful alternative approach, but this method's success varies among taxa, with little research available on its use in rodents. Here, we addressed a series of questions to develop a noninvasive genetic sampling approach for the endangered giant kangaroo rat (Dipodomys ingens): (1) how quickly does DNA degrade in natural conditions, (2) how many pellets are required to recover a genotype, (3) how often do multiple individuals contaminate a pooled sample from a single sampling location, and (4) how do variable and parameter estimates from noninvasive genetic sampling compare to live-trapping mark-recapture estimates? We found that fecal pellets were successfully genotyped up to 9 days (estimated probability of recovery = 0.78) after exposure to hot, arid conditions, but that rate fell precipitously soon after. Although giant kangaroo rats are territorial, multiple individuals deposited fecal pellets at the same sampling locations; however, single pellets contained sufficient DNA to recover genotypes and to identify individuals, so contamination was not a problem for this approach. Capture probabilities were lower using noninvasive genetic sampling (= 0.26, SE = 0.01) than live trapping (= 0.40, SE = 0.06). Population estimates were generally similar using noninvasive genetic sampling, although they were quite a bit higher (= 64, = 38) on one grid. Noninvasive genetic sampling can overcome many of the limitations of live-trapping for small mammals, but the approach should be tested in additional taxa and systems to provide more generalizable recommendations for sampling schemes. [ABSTRACT FROM AUTHOR]

The total mass flux (TMF) of particulate organic matter (POM) is key for understanding the energetic transfer within the "biological pump" (i.e., involving the carbon cycle), reflecting a critical connection between the surface and the bottom. A fixed multi-sediment trap was installed at 30 m depth in Callao Bay, central Peru from March to December 2020. After recovery, samples were dried and weighed to calculate the TMF and pellet flux. The average TMF was 601.9 mg·m−2·day−1, with 70.2 and 860 mg·m−2·day−1 as the lowest and highest values during "normal conditions". Zooplankton fecal pellets (ZFP) were found in ovoid (e.g., larvae) and cylindrical (e.g., adult copepods) shapes and their flux contribution to TMF was low, ranging from 0.17 to 85.59 mg·m−2·day−1. In contrast with ZFP, fish fecal pellets (FFP) were found in fragments with a cylindrical shape, and their contribution to the TMF was higher than ZFP, ranging from 1 to 92.56 mg·m−2·day−1. Mean sinking velocities were 4.63 ± 3.47 m·day−1 (ZFP) and 432.27 ± 294.26 m·day−1 (FFP). There is a considerable difference between the ZFP and FFP contributions to TMFs. We discuss the implications of these results regarding a still poorly understood process controlling the POM flux off the Peruvian coast. [ABSTRACT FROM AUTHOR]

Live capture-recapture is often considered the gold standard for estimating wildlife population size or density, but the approach can be limited by permitting requirements, required labor, welfare concerns, and biased estimates resulting from heterogeneity in individual behavior. Noninvasive genetic sampling (e.g., from fecal pellets) offers a powerful alternative approach, but this method’s success varies among taxa, with little research available on its use in rodents. Here, we addressed a series of questions to develop a noninvasive genetic sampling approach for the endangered giant kangaroo rat (Dipodomys ingens): (1) how quickly does DNA degrade in natural conditions, (2) how many pellets are required to recover a genotype, (3) how often do multiple individuals contaminate a pooled sample from a single sampling location, and (4) how do variable and parameter estimates from noninvasive genetic sampling compare to live-trapping mark-recapture estimates? We found that fecal pellets were successfully genotyped up to 9 days (estimated probability of recovery = 0.78) after exposure to hot, arid conditions, but that rate fell precipitously soon after. Although giant kangaroo rats are territorial, multiple individuals deposited fecal pellets at the same sampling locations; however, single pellets contained sufficient DNA to recover genotypes and to identify individuals, so contamination was not a problem for this approach. Capture probabilities were lower using noninvasive genetic sampling ( = 0.26, SE = 0.01) than live trapping ( = 0.40, SE = 0.06). Population estimates were generally similar using noninvasive genetic sampling, although they were quite a bit higher ( = 64 , = 38) on one grid. Noninvasive genetic sampling can overcome many of the limitations of live-trapping for small mammals, but the approach should be tested in additional taxa and systems to provide more generalizable recommendations for sampling schemes.

The total mass flux (TMF) of particulate organic matter (POM) is key for understanding the energetic transfer within the “biological pump” (i.e., involving the carbon cycle), reflecting a critical connection between the surface and the bottom. A fixed multi-sediment trap was installed at 30 m depth in Callao Bay, central Peru from March to December 2020. After recovery, samples were dried and weighed to calculate the TMF and pellet flux. The average TMF was 601.9 mg·m−2·day−1, with 70.2 and 860 mg·m−2·day−1 as the lowest and highest values during “normal conditions”. Zooplankton fecal pellets (ZFP) were found in ovoid (e.g., larvae) and cylindrical (e.g., adult copepods) shapes and their flux contribution to TMF was low, ranging from 0.17 to 85.59 mg·m−2·day−1. In contrast with ZFP, fish fecal pellets (FFP) were found in fragments with a cylindrical shape, and their contribution to the TMF was higher than ZFP, ranging from 1 to 92.56 mg·m−2·day−1. Mean sinking velocities were 4.63 ± 3.47 m·day−1 (ZFP) and 432.27 ± 294.26 m·day−1 (FFP). There is a considerable difference between the ZFP and FFP contributions to TMFs. We discuss the implications of these results regarding a still poorly understood process controlling the POM flux off the Peruvian coast.

Pterotrachea coronata is a carnivorous gastropod slowly swimming in the open sea all its life. Since P. coronata ingests prey without mastication, the whole bodies of the ingested organisms are often recognizable through the transparent body. The present study described fine structures of epithelial cells along the alimentary canal to elucidate functional adaptations to this digestion mode. The alimentary canal is a simple tube; the epithelial cells lining the tube always have microvilli and are basally underlain by a muscular layer. The structure of the epidermis was different in each organ, i.e., buccal mass, esophagus, intestine, and visceral nucleus, with differences in cell shape, microvilli length and density, and muscle layer thickness. Additionally, a cuticular layer overlies the epithelia in the buccal cavity and the alimentary epithelial cells are multi-ciliated in the visceral nucleus where absorption of digested material and formation of fecal pellets proceed. The long esophagus and intestine of P. coronata are probably suitable to retain ingested materials for the slow digestion process, without mastication. While the intestine occupied most of the alimentary canal, the epithelium was thin and had short, sparse microvilli. This poorly developed but large, transparent intestine in P. coronata is one of the major characteristics of this animal. Slow digestion with retention of prey in the large intestine would be an adaptation for the floating life of this transparent carnivore, allowing it to survive in the epipelagic layers where there are limited chances to obtain prey organisms, especially during the day. [ABSTRACT FROM AUTHOR]

Organic carbon of fecal pellets and small-sized (≤ 1mm) zooplankton was measured using a high- temperature combustion method. The method was adapted for measurements with Shimadzu TOC-VCPH analyzer equipped with a manual injection module. The range of organic carbon values was 30–10 000 ng ind–1. The samples for analysis were collected during the cruises of the R/V "Akademik Mstislav Keldysh" in the Kara Sea in 2019–2021. Relationship between body carbon (C, µg ind–1) and prosome length (L, mm) of zooplankton describes by the equation С = 4.24 L1.84, r2 = 0.85, n = 46. Carbon of field collected fecal pellet varied from 9.4 to 102.9 µg С mm–3. The carbon to chlorophyll a ratio of fecal pellets differed by more than two orders of magnitude. The highest values (542.1 and 726.1) were obtained in the bays of the Novaya Zemlya Archipelago, the lowest (3.2–5.6) on the Kara sea shelf in June 2021 soon after ice melting. The perspectives of implication of high temperature combustion method for studies of zooplankton in situ feeding and to estimate the contribution of fecal pellets to POC vertical flux are discussed. [ABSTRACT FROM AUTHOR]

Phytoplankton and zooplankton are key marine components that play an important role in metal distribution through a food web transfer. An increased phytoplankton concentration as a result of ocean acidification and warming are well-established, along with the fact that phytoplankton biomagnify 210Po by 3–4 orders of magnitude compared to the seawater concentration. This experimental study is carried out to better understand the transfer of polonium between primary producers and consumers. The experimental produced data highlight the complex interaction between the polonium concentration in zooplankton food, i.e. phytoplankton, its excretion via defecated fecal pellets, and its bioaccumulation at ambient seawater pH and a lower pH of 7.7, typical of ocean acidification scenarios in the open ocean. The mass of copepods recovered was 11% less: 7.7 pH compared to 8.2. The effects of copepod species (n = 3), microalgae species (n = 3), pH (n = 2), and time (n = 4) on the polonium activity in the fecal pellets (expressed as % of the total activity introduced through feeding) was tested using an ANOVA 4. With the exception of time (model: F20, 215 = 176.84, p < 0.001; time: F3 = 1.76, p = 0.16), all tested parameters had an impact on the polonium activity (copepod species: F2 = 169.15, p < 0.0001; algae species: F2 = 10.21, p < 0.0001; pH: F1 = 9.85, p = 0.002) with complex interactions (copepod x algae: F2 = 19.48, p < 0.0001; copepod x pH: F2 = 10.54, p < 0.0001; algae x pH: F2 = 4.87, p = 0.009). The experimental data underpin the hypothesis that metal bioavailability and bioaccumulation will be enhanced in secondary consumers such as crustacean zooplankton due to ocean acidification. [ABSTRACT FROM AUTHOR]

Predicting marine carbon sequestration in a changing climate requires mechanistic understanding of the processes controlling sinking particle flux under different climatic conditions. The recent occurrence of a warm anomaly (2014–2015) followed by an El Niño (2015–2016) in the southern sector of the California Current System presented an opportunity to analyze changes in the biological carbon pump in response to altered climate forcing. We compare primary production, mesozooplankton grazing, and carbon export from the euphotic zone during quasi-Lagrangian experiments conducted in contrasting conditions: two cruises during warm years - one during the warm anomaly in 2014 and one toward the end of El Niño 2016 – and three cruises during El Niño-neutral years. Results showed no substantial differences in the relationships between vertical carbon export and its presumed drivers (primary production, mesozooplankton grazing) between warm and neutral years. Mesozooplankton fecal pellet enumeration and phaeopigment measurements both showed that fecal pellets were the dominant contributor to export in productive upwelling regions. In more oligotrophic regions, fluxes were dominated by amorphous marine snow with negligible pigment content. We found no evidence for a significant shift in the relationship between mesozooplankton grazing rate and chlorophyll concentration. However, mass-specific grazing rates were lower at low-to-moderate chlorophyll concentrations during warm years relative to neutral years. We also detected a significant difference in the relationship between phytoplankton primary production and photosynthetically active radiation between years: at similar irradiance and nutrient concentrations, productivity decreased during the warm events. Whether these changes resulted from species composition changes remains to be determined. Overall, our results suggest that the processes driving export remain similar during different climate conditions, but that species compositional changes or other structural changes require further attention.

Predicting marine carbon sequestration in a changing climate requires mechanistic understanding of the processes controlling sinking particle flux under different climatic conditions. The recent occurrence of a warm anomaly (2014–2015) followed by an El Niño (2015–2016) in the southern sector of the California Current System presented an opportunity to analyze changes in the biological carbon pump in response to altered climate forcing. We compare primary production, mesozooplankton grazing, and carbon export from the euphotic zone during quasi-Lagrangian experiments conducted in contrasting conditions: two cruises during warm years - one during the warm anomaly in 2014 and one toward the end of El Niño 2016 – and three cruises during El Niño-neutral years. Results showed no substantial differences in the relationships between vertical carbon export and its presumed drivers (primary production, mesozooplankton grazing) between warm and neutral years. Mesozooplankton fecal pellet enumeration and phaeopigment measurements both showed that fecal pellets were the dominant contributor to export in productive upwelling regions. In more oligotrophic regions, fluxes were dominated by amorphous marine snow with negligible pigment content. We found no evidence for a significant shift in the relationship between mesozooplankton grazing rate and chlorophyll concentration. However, mass-specific grazing rates were lower at low-to-moderate chlorophyll concentrations during warm years relative to neutral years. We also detected a significant difference in the relationship between phytoplankton primary production and photosynthetically active radiation between years: at similar irradiance and nutrient concentrations, productivity decreased during the warm events. Whether these changes resulted from species composition changes remains to be determined. Overall, our results suggest that the processes driving export remain similar during different climate conditions, but that species compositional changes or other structural changes require further attention.

Understanding population dynamics requires reliable estimates of population density, yet this basic information is often surprisingly difficult to obtain. With rare or difficult-to-capture species, genetic surveys from noninvasive collection of hair or scat has proved cost-efficient for estimating densities. Here, we explored whether noninvasive genetic sampling (NGS) also offers promise for sampling a relatively common species, the snowshoe hare (Lepus americanus Erxleben, 1777), in comparison with traditional live trapping. We optimized a protocol for single-session NGS sampling of hares. We compared spatial capture-recapture population estimates from live trapping to estimates derived from NGS, and assessed NGS costs. NGS provided population estimates similar to those derived from live trapping, but a higher density of sampling plots was required for NGS. The optimal NGS protocol for our study entailed deploying 160 sampling plots for 4 days and genotyping one pellet per plot. NGS laboratory costs ranged from approximately $670 to $3000 USD per field site. While live trapping does not incur laboratory costs, its field costs can be considerably higher than for NGS, especially when study sites are difficult to access. We conclude that NGS can work for common species, but that it will require field and laboratory pilot testing to develop cost-effective sampling protocols.

Abstract Detritivores need to upgrade their food to increase its nutritional value. One method is to fragment detritus promoting the colonization of nutrient‐rich microbes, which consumers then ingest along with the detritus; so‐called microbial gardening. Observations and numerical models of the detritus‐dominated ocean mesopelagic zone have suggested microbial gardening by zooplankton is a fundamental process in the ocean carbon cycle leading to increased respiration of carbon‐rich detritus. However, no experimental evidence exists to demonstrate that microbial respiration rates are higher on recently fragmented sinking detrital particles. Using aquaria‐reared Antarctic krill fecal pellets, we showed fragmentation increased microbial particulate organic carbon (POC) turnover by 1.9×, but only on brown fecal pellets, formed from the consumption of other pellets. Microbial POC turnover on un‐ and fragmented green fecal pellets, formed from consuming fresh phytoplankton, was equal. Thus, POC content, fragmentation, and potentially nutritional value together drive POC turnover rates. Mesopelagic microbial gardening could be a risky strategy, as the dominant detrital food source is settling particles; even though fragmentation decreases particle size and sinking rate, it is unlikely that an organism would remain with the particle long enough to nutritionally benefit from attached microbes. We propose “communal gardening” occurs whereby additional mesopelagic organisms nearby or below the site of fragmentation consume the particle and the colonized microbes. To determine how fragmentation impacts the remineralization of sinking carbon‐rich detritus and to parameterize microbial gardening in mesopelagic carbon models, three key metrics from further controlled experiments and observations are needed; how particle composition (here, pellet color/krill diet) impacts the response of microbes to the fragmentation of particles; the nutritional benefit to zooplankton from ingesting microbes after fragmentation along with identification of which essential nutrients are being targeted; how both these factors vary between physical (shear) and biological particle fragmentation.

Worldwide, Aeromonas salmonicida is a major bacterial pathogen of fish in both marine and freshwater environments. Despite psychrophilic growth being common for this species, the number of characterized mesophilic strains is increasing. Thus, this species may serve as a model for the study of intraspecies lifestyle diversity. Although bacteria are preyed upon by protozoan predators, their interaction inside or outside the phagocytic pathway of the predator can provide several advantages to the bacteria. To correlate intraspecies diversity with predation outcome, we studied the fate of psychrophilic and mesophilic strains of A. salmonicida cocultured with the ciliate Tetrahymena pyriformis. A total of three types of outcome were observed: digestion, resistance to phagocytosis, and pathogenicity. The psychrophilic strains are fully digested by the ciliate. In contrast, the mesophilic A. salmonicida subsp. pectinolytica strain is pathogenic to the ciliate. All the other mesophilic strains display mechanisms to resist phagocytosis and/or digestion, which allow them to survive ciliate predation. In some cases, passage through the phagocytic pathway resulted in a few mesophilic A. salmonicida being packaged inside fecal pellets. This study sheds light on the great phenotypic diversity observed in the complex range of mechanisms used by A. salmonicida to confront a predator. [ABSTRACT FROM AUTHOR]

Phytoplankton and zooplankton are key marine components that play an important role in metal distribution through a food web transfer. An increased phytoplankton concentration as a result of ocean acidification and warming are well-established, along with the fact that phytoplankton biomagnify 210Po by 3–4 orders of magnitude compared to the seawater concentration. This experimental study is carried out to better understand the transfer of polonium between primary producers and consumers. The experimental produced data highlight the complex interaction between the polonium concentration in zooplankton food, i.e. phytoplankton, its excretion via defecated fecal pellets, and its bioaccumulation at ambient seawater pH and a lower pH of 7.7, typical of ocean acidification scenarios in the open ocean. The mass of copepods recovered was 11% less: 7.7 pH compared to 8.2. The effects of copepod species (n = 3), microalgae species (n = 3), pH (n = 2), and time (n = 4) on the polonium activity in the fecal pellets (expressed as % of the total activity introduced through feeding) was tested using an ANOVA 4. With the exception of time (model: F20, 215 = 176.84, p < 0.001; time: F3 = 1.76, p = 0.16), all tested parameters had an impact on the polonium activity (copepod species: F2 = 169.15, p < 0.0001; algae species: F2 = 10.21, p < 0.0001; pH: F1 = 9.85, p = 0.002) with complex interactions (copepod x algae: F2 = 19.48, p < 0.0001; copepod x pH: F2 = 10.54, p < 0.0001; algae x pH: F2 = 4.87, p = 0.009). The experimental data underpin the hypothesis that metal bioavailability and bioaccumulation will be enhanced in secondary consumers such as crustacean zooplankton due to ocean acidification.

To better quantify the ocean's biological carbon pump, we resolved the diversity of sinking particles that transport carbon into the ocean's interior, their contribution to carbon export, and their attenuation with depth. Sinking particles collected in sediment trap gel layers from four distinct ocean ecosystems were imaged, measured, and classified. The size and identity of particles was used to model their contribution to particulate organic carbon (POC) flux. Measured POC fluxes were reasonably predicted by particle images. Nine particle types were identified, and most of the compositional variability was driven by the relative contribution of aggregates, long cylindrical fecal pellets, and salp fecal pellets. While particle composition varied across locations and seasons, the entire range of compositions was measured at a single well‐observed location in the subarctic North Pacific over one month, across 500 m of depth. The magnitude of POC flux was not consistently associated with a dominant particle class, but particle classes did influence flux attenuation. Long fecal pellets attenuated most rapidly with depth whereas certain other classes attenuated little or not at all with depth. Small particles (<100 μm) consistently contributed ∼5% to total POC flux in samples with higher magnitude fluxes. The relative importance of these small particle classes (spherical mini pellets, short oval fecal pellets, and dense detritus) increased in low flux environments (up to 46% of total POC flux). Imaging approaches that resolve large variations in particle composition across ocean basins, depth, and time will help to better parameterize biological carbon pump models. Plain Language Summary: Sinking particles transport carbon from the surface ocean to depth where carbon is sequestered from the atmosphere for long time periods. The amount of carbon transported by this process is difficult to quantify, in part because of the complex ecological interactions that generate sinking particles and alter downward transport. This study combined chemical measurements with detailed imagery of sinking particles collected in drifting sediment traps to survey how different types of particles affect carbon export across five locations. The biological characteristics of imaged particles can be used to reasonably predict carbon export and its attenuation with depth. Measured particles were classified into nine different categories, including various types of aggregates, organisms, and zooplankton fecal pellets. The amount of sinking carbon was not related to the dominance of any specific particle type, but each type transported carbon with differing efficiencies. Episodic presence of fecal pellets produced by gelatinous zooplankton had a large influence on transport of carbon to depth. Particles often considered too small to contribute to carbon export (<100 µm) were consistently important, especially in low flux environments, and often attenuated relatively little with depth. Resolving biological details of sinking particles improves our ability to quantify the ocean's carbon cycle. Key Points: Carbon flux into the deep ocean by sinking particles can be reasonably predicted from images of collected particle fluxSinking particle type and trophic processing affect attenuation of carbon flux with depthParticles smaller than 100 μm can be an important component of sinking carbon and some attenuated little with depth [ABSTRACT FROM AUTHOR]

Background: In herbivores, the proximal and distal colonic regions feature distinct motor patterns underlying formation and propulsion of fecal pellets, respectively. Omnivores, such as mice and humans, lack a similar clear anatomical transition between colonic regions. We investigated whether distinct processes form and propel content along the large intestine of a mouse (an omnivore). Methods: We recorded propulsive and non‐propulsive neurogenic motor activity in mouse large intestine under six different stimulus conditions of varying viscosities. Gut wall movements were recorded by video and smooth muscle electrical behavior recorded with extracellular suction electrodes. Key Results: Three major neurally mediated motor patterns contributed to pellet formation and propulsion. (1) Pellet‐shaped boluses are pinched off near the ceco‐colonic junction and slowly propelled distally to a transition located at 40% length along the colon. (2) At this functional colonic flexure, propulsion speed is significantly increased by self‐sustaining neural peristalsis. Speed transition at this location also occurs with artificial pellets and with spontaneously formed boluses in the empty colon. (3) Periodic colonic motor complexes (CMCs) were present in all conditions reaching a maximal frequency of about 0.4 cpm and extending across the proximal and distal colon with faster speed of propagation. Conclusions and Inferences: The three motor patterns share a unique underlying fundamental property of the enteric circuits, which involve extended ensembles of enteric neurons firing at close to 2 Hz. The demonstration of distinct functional differences between proximal and distal colon in rabbit, guinea pig, and now mouse raises the possibility that this may be an organizational principle in other mammalian species, including humans. [ABSTRACT FROM AUTHOR]

Microplastics have been reported to be present in zooplankton, yet questions persist regarding their fate and dynamics within biota. We selected the commercial mysid shrimp, Mesopodopsis orientalis , as the focal zooplankton for this study due to their crucial role in our study area, the Inner Gulf of Thailand in January 2022. We investigated the presence of microplastics in mysid bodies and fecal pellets, examining both attached microplastics on external body parts and those ingested. In addition, we conducted microplastic feeding experiments, exposing mysids to various treatments of microplastics. The results of the field investigation indicate that mysids exhibited an average of 0.12 ± 0.03 microplastic items/mysid from whole-body samples. The shape, type, and color of microplastics found in mysids were similar to those present in seawater, with blue PET microfibers being the most prevalent. Our observations on live mysids revealed that microplastics were acquired through ingestion and adherence to appendages and exoskeletons. Microplastics were observed in mysid's fecal pellets at 0.09 ± 0.03 items/mysid, while microplastics adhering to the mysid's body and appendages were observed at 0.10 ± 0.04 items/mysid. The sizes of microplastics extracted from preserved mysids ranged from 58 μm to 4669 μm, with median of 507 μm. The laboratory experiments revealed that the presence of microalgae enhanced microplastic ingestion in mysids; microplastics incubated with a cyanobacterium, Oscillatoria sp., and diatom Navicula sp. significantly increased the number of microplastic particles ingested by mysids. This study showed that microplastics can be more ingested in mysids, especially when food items are present. Microplastic fate in these animals may involve expulsion into the environment or adherence, potentially facilitating their transfer up the marine food web. [Display omitted] • Mysid shrimps were found to contain microplastics, averaging 0.09 items per individual within the body cavity and increasing to 0.19 when including those attached to external body parts. • Microplastics found in mysids were similar in shape, type, and color to those in seawater, with blue polyethylene terephthalate (PET) microfibers being the most common. • The presence of microalgae, particularly the diatom Navicula sp., actively enhanced microplastic ingestion in mysids. [ABSTRACT FROM AUTHOR]

Detritivores need to upgrade their food to increase its nutritional value. One method is to fragment detritus promoting the colonization of nutrient‐rich microbes, which consumers then ingest along with the detritus; so‐called microbial gardening. Observations and numerical models of the detritus‐dominated ocean mesopelagic zone have suggested microbial gardening by zooplankton is a fundamental process in the ocean carbon cycle leading to increased respiration of carbon‐rich detritus. However, no experimental evidence exists to demonstrate that microbial respiration rates are higher on recently fragmented sinking detrital particles.Using aquaria‐reared Antarctic krill fecal pellets, we showed fragmentation increased microbial particulate organic carbon (POC) turnover by 1.9×, but only on brown fecal pellets, formed from the consumption of other pellets. Microbial POC turnover on un‐ and fragmented green fecal pellets, formed from consuming fresh phytoplankton, was equal. Thus, POC content, fragmentation, and potentially nutritional value together drive POC turnover rates.Mesopelagic microbial gardening could be a risky strategy, as the dominant detrital food source is settling particles; even though fragmentation decreases particle size and sinking rate, it is unlikely that an organism would remain with the particle long enough to nutritionally benefit from attached microbes. We propose "communal gardening" occurs whereby additional mesopelagic organisms nearby or below the site of fragmentation consume the particle and the colonized microbes.To determine how fragmentation impacts the remineralization of sinking carbon‐rich detritus and to parameterize microbial gardening in mesopelagic carbon models, three key metrics from further controlled experiments and observations are needed; how particle composition (here, pellet color/krill diet) impacts the response of microbes to the fragmentation of particles; the nutritional benefit to zooplankton from ingesting microbes after fragmentation along with identification of which essential nutrients are being targeted; how both these factors vary between physical (shear) and biological particle fragmentation. [ABSTRACT FROM AUTHOR]

Settling marine aggregates, such as zooplankton fecal pellets and marine snow, transport organic matter from the surface ocean to the deep sea and are largely responsible for the ocean’s sequestration of carbon. However, our understanding of the functioning of the biological pump and the distribution of particulate organic matter in the water column often hinge on limited bulk data from sediment traps, large volume filtration or instantaneous snap-shots from in situ optical systems that only see a small part of the particle and aggregate spectra. We evaluated the added value of combining different optical systems to detect a range of organic and inorganic particle types during a case-study in the Cape Blanc upwelling region. Laboratory calibrations showed that one camera system detected large organic aggregates well and in situ data showed that it correlated positively with fluorescence. The other camera was better at detecting small, mainly inorganic particles which were not seen by the first camera and correlated positively with turbidity. The combined deployments of the two optical systems together with fluorescence and turbidity sensors showed potentials for added insights into spatial (depth) and temporal (diurnal) particle dynamics. The case study exemplified the different efficiencies of two camera systems to detect particles of different types in marine waters. From this, the results highlighted the importance of discriminating between qualitative and quantitative ranges of imaging systems, in order to understand the quantitative range of sizes as well as types of particles detected by a given system. This is especially important when optical systems are used to estimate carbon fluxes and particulate organic matter distribution in the water column from vertical profiles of particle size-distribution and abundance.

Hydrocarbon mixtures extracted from fecal pellets of drywood termites are species-specific and can be characterized to identify the termites responsible for damage, even when termites are no longer present or are unable to be recovered easily. In structures infested by drywood termites, it is common to find fecal pellets, but difficult to sample termites from the wood. When fecal pellets appear after remedial treatment of a structure, it is difficult to determine whether this indicates that termites in the structure are still alive and active or not. We examined the hydrocarbon composition of workers, alates, and soldiers of Incisitermes minor (Hagen) (family Kalotermitidae) and of fecal pellets of workers. Hydrocarbons were qualitatively similar among castes and pellets. Fecal pellets that were aged for periods of 0, 30, 90, and 365 days after collection were qualitatively similar across all time periods, however, the relative quantities of certain individual hydrocarbons changed over time, with 19 of the 73 hydrocarbon peaks relatively increasing or decreasing. When the sums of the positive and negative slopes of these 19 hydrocarbons were indexed, they produced a highly significant linear correlation (R 2 = 0.89). Consequently, the quantitative differences of these hydrocarbons peaks can be used to determine the age of worker fecal pellets, and thus help determine whether the colony that produced them is alive or dead.

We studied sedimentation processes in the Lofoten Basin of the Norwegian Sea based on data of the Automatic Deep-Sea Sedimentation Observatory (ADSO) deployed for a year (August 2017–July 2018). The article presents estimates of the vertical fluxes of total sedimentary material, organic carbon (Corg), calcium carbonate (CaCO3), biogenic silica (SiO2bio), aluminum, and the particles of planktonic origin (pteropods, foraminifera, fecal pellets, necrozooplankton). The seasonal pattern of total vertical flux is characterized by a unimodal distribution with a maximum in September 2017 (191 mg dry weight m–2 day–1) in the 0–500 m surface water layer. The total flux decreases markedly from November and reaches the minimum (2.6 mg m–2 day–1) in March–April 2018. The maximum Corg flux values (5.2 mg C m–2 day–1), CaCO3 (178 mg CaCO3 m–2 day–1), and SiO2bio (9.1 mg SiO2bio m–2 day–1) are observed in autumn. The value of fluxes and the portion of lithogenic material in it are higher at a depth of 2950 m due to redeposition from the nepheloid layer. The amplitude of flux variations during the year is noticeably smaller at this depth. The highest fluxes are related to the maass sedimentation of juvenile pteropods Limacina retroversa. The contribution of pteropods to vertical fluxes in autumn is 60–100% for CaCO3 and 56–73% for Corg. The contribution of foraminifera to the total CaCO3 flux does not exceed 6% and only reaches 60% at a depth of 550 m in October. The flux of fecal pellets, where ostracod pellets dominate, varies from <0.01 to 2.1 mgC m–2 day–1, making up from 0.1 to 90% of the Corg flux. The flux of zooplankton carcasses (ZCs) in the 0–550 m water layer varies from 0 to 0.45 mgC m–2 day–1, reaching the maximum value in February. The share of ZCs flux was 0–33% in the summer–autumn season, 12–52% in winter, and 23–41% in spring relative to the total (taking into account the ZCs) Corg flux. The ZCs flux varied from 0.04 to 0.22 mgC m–2 day–1 in the near-bottom water layer and amounted to 0.7–2% of the total Corg flux. The total contribution of all studied planktonic particles to the annual CaCO3 flux was 16–47%, and their contribution to the annual Corg flux was 37–45%. Comparative analysis of our results and published data obtained in the 1990s demonstrates that the observed climatic changes (increasing temperature and salinity, as well as an increase in the thickness of the Atlantic water layer) in the Lofoten Basin did not result in significant changes in the quantitative characteristics of sedimentation process. [ABSTRACT FROM AUTHOR]

Sediment traps are an important tool for studying the source, composition and sedimentation processes of sinking particulate matter in the ocean. An in situ observational mooring (TJ-A-1) is located in the northern South China Sea (20.05°N, 117.42°E) at a water depth of 2 100 m and equipped with two sediment traps deployed at 500 m and 1 950 m. Samples were collected at 18-day intervals, and 20 samples were obtained at both depths from May 2014 to May 2015. Large amounts of fecal matter and marine snow were collected in the lower trap. The fluxes of marine snow and fecal pellets exhibited a fluctuating decrease between May 2014 and early August 2014 and then stabilized at a relatively low level. Scanning electron microscopy observations revealed that the main components of the marine snow and fecal pellets were diatoms, coccolithophores, radiolarians, and other debris, all of which are planktons mostly produced in photic zone. Used in conjunction with the particle collection range estimates from the lower trap and data on ocean surface chlorophyll, these marine snow and fecal pellets were related to the lateral transport of deep water and not vertical migrations from overlying water column. Moreover, the source area might be southwest of Taiwan. [ABSTRACT FROM AUTHOR]

Neomysis awatschensis is an important prey item for various fishes in Lake Kasumigaura, Japan. There is, however, a contradiction concerning the major food sources of this mysid species: whether "bottom mud", "particulate organic matter (POM) including phytoplankton", or "mesozooplankton" is the main diet, and this uncertainty may be due to differences in the methodology used to determine the prey items in previous studies. This study examined the main food sources of N. awatschensis by combining three methods to eliminate methodological biases: DNA metabarcoding, microscopy and stable isotope analysis. Planktonic diatoms and green algae sequences were the main taxa detected by DNA metabarcoding and microscopy on the fecal pellets. The δ15N values of the mysids were similar to those of phytoplankton feeders rather than carnivorous planktonic crustaceans. These results suggest that diatoms and green algae were the major food sources for N. awatschensis in Lake Kasumigaura during the investigation period, and that its trophic level is as low as that of herbivores. However, the partial contribution of other "POM" (e.g., benthic diatoms) is also implied, considering the dispersion in δ13C values. Mesozooplankton prey, such as copepods, were detected both using DNA metabarcoding and microscopy, but they could not be a major food source due to the low nitrogen stable isotopic signature of the mysids. The opportunistic feeding habits of N. awatschensis possibly explain the consistent dominance of this species in the lake, where the ecosystem structure was substantially changed because of successive desalination. [ABSTRACT FROM AUTHOR]

Contemporary publications on various aspects of sediment traps application in marine and fresh waters are reviewed. Recommendations are given to construction and exposure of sediment traps in water column to a representative collection of settling particles (shape and size of traps, bafflers, covers, sodium chloride addition, suspending devices and free drifting traps, bactericides, swimmers influence, periphyton growth and settling material decomposition assessment, exposure duration, and bottom resuspension correction). Accuracy and precision of the trap method are discussed. A comparative analysis of sinking velocity values of large particles (marine snow, fecal pellets and zooplankton carcasses) obtained by different methods is carried out. Some modern traps and suspension systems are described; considerable progress in video recording is noted; reasonable traps to collect zooplankton carcasses are choosen.

Population genetic analyses for moose have been based on DNA extracted from blood and other body tissues. Non-invasive sampling of fecal pellets is another potential source of DNA. We compared DNA extraction from blood, liver tissue, and fecal pellet samples from moose in Minnesota and Yellowstone National Park, USA. Extracted DNA from all source types was sufficient for genotyping using 15 microsatellites. DNA extracted from fecal pellets was of lower quality and quantity than DNA extracted from blood and tissue. We provide comparisons of efficiency and effectiveness of DNA extraction protocols for blood, tissue, and fecal pellets, and demonstrate the suitability of using DNA extracted from non-invasively sampled material in moose.

The sulfur-bearing limestones interbedded in the upper Miocene diatomaceous sediments (Tripoli Formation) of the Lorca Basin (SE Spain) are typified, as other Mediterranean coeval carbonate and gypsum deposits, by filamentous, circular and rod-shaped microstructures of controversial origin. These features have been interpreted both as fecal pellets of brine shrimps and/or of copepods, remains of algae or cyanobacteria and fossilized sulfide-oxidizing bacteria. To shed light on their origin, a multidisciplinary study including optical, UV and scanning electron microscopy, Raman microspectroscopy, and geochemical (carbon and oxygen stable isotopes) analyses has been carried out on three carbonate beds exposed along the La Serrata ridge. The different composition of the filamentous and circular objects with respect to the rod-shaped microstructures suggest that the former represent remains of bacteria, while the latter fecal pellets of deposit- or suspension-feeder organisms. Size and shape of the filamentous and circular microfossils are consistent with their assignment to colorless sulfide-oxidizing bacteria like Beggiatoa (or Thioploca) and Thiomargarita, which is further supported by the presence, only within the microfossil body, of tiny pyrite grains. These grains possibly result from early diagenetic transformation of original sulfur globules stored by the bacteria, which are a diagnostic feature of this group of prokaryotes. The development of microbial communities dominated by putative sulfide-oxidizing bacteria at Lorca was favored by hydrogen sulfide flows generated through degradation of organic matter by sulfate-reducing bacteria thriving in underlying organic-rich sediments.

The role of plankton in the vertical flux in the East Siberian Sea was studied in the 69 cruise of the RV "Akademik Mstislav Keldysh" in September 2017. Vertical fluxes were measured in sediment traps on two buoy stations in the area of the Indigirka River plume and in the marine shelf area. Mass vertical flux and particulate organic carbon flux varied from 80 to 530 mg/m2/d and from 16 to 49 mgС/m2/d, accordingly. Phytoplankton in sediment traps was dominated by cysts and spores of diatoms and dinoflagellates. Phytoplankton flux increased with depths from 0.22–0.33 to 1.2–1.3 mgС/m2/d. Fecal pellet fluxes (7–12 mgС/m2/d) were similar at two studied stations and did not change with depth. Zooplankton in the traps was dominated by larvacean houses and carcasses of copepods Jashnovia tolli and Calanus glacialis. Flux of zooplankton varied from 3 to 17 mgС/m2/d. The influence of the continental runoff reflected in a decrease of the proportion of planktonogenic components in the vertical flux of organic carbon. In the river plume area, their total contribution to organic carbon flux did not exceed 30%; on the marine shelf it reached 80% of organic carbon flux. [ABSTRACT FROM AUTHOR]

The sulfur-bearing limestones interbedded in the upper Miocene diatomaceous sediments (Tripoli Formation) of the Lorca Basin (SE Spain) are typified, as other Mediterranean coeval carbonate and gypsum deposits, by filamentous, circular and rod-shaped microstructures of controversial origin. These features have been interpreted both as fecal pellets of brine shrimps and/or of copepods, remains of algae or cyanobacteria and fossilized sulfide-oxidizing bacteria. To shed light on their origin, a multidisciplinary study including optical, UV and scanning electron microscopy, Raman microspectroscopy, and geochemical (carbon and oxygen stable isotopes) analyses has been carried out on three carbonate beds exposed along the La Serrata ridge. The different composition of the filamentous and circular objects with respect to the rod-shaped microstructures suggest that the former represent remains of bacteria, while the latter fecal pellets of deposit- or suspension-feeder organisms. Size and shape of the filamentous and circular microfossils are consistent with their assignment to colorless sulfide-oxidizing bacteria like Beggiatoa (or Thioploca) and Thiomargarita , which is further supported by the presence, only within the microfossil body, of tiny pyrite grains. These grains possibly result from early diagenetic transformation of original sulfur globules stored by the bacteria, which are a diagnostic feature of this group of prokaryotes. The development of microbial communities dominated by putative sulfide-oxidizing bacteria at Lorca was favored by hydrogen sulfide flows generated through degradation of organic matter by sulfate-reducing bacteria thriving in underlying organic-rich sediments. [ABSTRACT FROM AUTHOR]

Abstract Copepods fecal pellets (FPs) are important contributors to carbon export in the ocean, but their role in the carbon export is poorly understood in the eutrophic coastal sea, where copepods biomass is always high. Two cruises were carried out in one of the most eutrophic coastal seas in the world — the Changjiang (Yangtze River) estuary during spring and summer in 2011, and copepods fecal pellets carbon (FPC) concentration, their production rates and sinking rates were measured, and a potential export flux of copepods FPs was also calculated. The copepods FPC concentration ranged from 0.21 to 1.25 mg C m−3 (mean = 0.58 ± 0.24 mg C m−3) in spring and 0.46–1.53 mg C m−3 (mean = 0.76 ± 0.25 mg C m−3) in summer, which was significantly lower than that of phytoplankton cells, indicating that copepods FPs only accounted for a minor part of the POC pool in this area. Production rates of copepods FPs fell in the range of the reported values, and the high values always appeared at stations with high phytoplankton biomass. Sinking rates of copepods FPs determined in the lab ranged from 17.82 to 223.30 m d−1 (mean = 73.46 ± 47.56 m d−1) in spring and 34.62–262.33 m d−1 (mean = 92.81 ± 56.80 m d−1) in summer, and they were significantly positive correlated with the FPs volume. The density of copepods FPs was also calculated with the determined sinking rate, and it was higher in summer than that in spring due to the variation of phytoplankton diets from spring to summer. The potential copepods FPs export flux ranged from 17.72 to 60.20 mg C m−2 d−1 (mean = 37.13 ± 16.21 mg C m−2 d−1) in spring and 23.80–166.10 mg C m−2 d−1 (mean = 79.44 ± 48.86 mg C m−2 d−1) in summer, and it was at a comparable level with the export flux of phytoplankton cells during both cruises. This study indicated that copepods FPs comprised a substantial fraction of exported carbon in the Changjiang (Yangtze River) estuary, and they should be taken into account when we study the biological pump in other eutrophic coastal seas around the world. [ABSTRACT FROM AUTHOR]

The difficulty of collecting occurrence and population dynamics data in mammalian populations of low density poses challenges for making informed management decisions. We assessed the use of scat-detection dogs to search for fecal pellets in a low density moose (Alces alces) population in the Adirondack Park in New York State, and the success rate of DNA extraction from moose fecal pellets collected during the surveys. In May 2008, two scat-detection dog teams surveyed 20, 4-km transects and located 138 moose scats. In 2011 we successfully amplified DNA from 39 scats (28%) and were able to uniquely identify 25 individuals. Improved storage protocols and earlier lab analysis would increase the amplification success rate. Scat-detection dogs proved to be a reasonable, non-invasive method to collect useful data from the low density moose population in the Adirondack Park.

Protozoa are natural predators of bacteria, but some bacteria can evade digestion once phagocytosed. Some of these resistant bacteria can be packaged in the fecal pellets produced by protozoa, protecting them from physical stresses and biocides. Depending on the bacteria and protozoa involved in the packaging process, pellets can have different morphologies. In the present descriptive study, we evaluated the packaging process with 20 bacteria that have never been tested before for packaging by ciliates. These bacteria have various characteristics (shape, size, Gram staining). All of them appear to be included in pellets produced by the ciliates Tetrahymena pyriformis and/or T. thermophila in at least one condition tested. We then focused on the packaging morphology of four of these bacteria. Our results demonstrated that, as shown previously for Mycobacterium smegmatis, the packaging of Microbacterium oxydans, Micrococcus luteus, and Cupriavidus sp. was formed of a single layer of material. The packaging of Cellulosimicrobiumfunkei was made of indistinguishable material. A different pellet morphology was obtained for each of the four bacterial strains studied. The ingestion of small bacteria resulted in rounder, denser, and more regular pellets. These results support the idea that bacteria packaging is a relatively widespread phenomenon.

It is necessary to estimate the population abundance of deer for managing their populations. However, most estimates are from high-density populations inhabiting the forests of North America or Europe; there is currently a lack of necessary knowledge regarding low-density deer populations in different forest habitats. In this article, we used fecal DNA based on the capture-mark-recapture method to estimate the population abundance of Siberian roe deer (Capreolus pygargus) in Liangshui National Nature Reserve in the Lesser Xing’an Mountains, northeast China, where the deer population was found to be of a low density by limited studies. We used a robust survey design to collect 422 fecal pellet groups in 2016 and extracted DNA from those samples, generating 265 different genotypes; we thus identified 77 deer individuals based on six microsatellite markers (Roe1, Roe8, Roe9, BM757, MB25 and OarFCB304). With capture and recapture records of these 77 individuals, the abundance of roe deer was estimated to be 87 deer (80–112, 95% CI) using the Program CAPTURE. Using an effective sampling area which resulted from the mean maximum recapture distance (MMRD), we converted the population abundance to a density of 2.9 deer/km2 (2.7–3.7, 95% CI). Our study estimated the roe deer population abundance by a feces-based capture-mark-recapture approach in northeast China, successfully demonstrating the applicability of non-invasive genetic sampling in monitoring populations of deer in this area, which contributes to the development of low-density deer population ecology and management.

Abstract Predicting marine carbon sequestration in a changing climate requires mechanistic understanding of the processes controlling sinking particle flux under different climatic conditions. The recent occurrence of a warm anomaly (2014–2015) followed by an El Niño (2015–2016) in the southern sector of the California Current System presented an opportunity to analyze changes in the biological carbon pump in response to altered climate forcing. We compare primary production, mesozooplankton grazing, and carbon export from the euphotic zone during quasi-Lagrangian experiments conducted in contrasting conditions: two cruises during warm years - one during the warm anomaly in 2014 and one toward the end of El Niño 2016 – and three cruises during El Niño-neutral years. Results showed no substantial differences in the relationships between vertical carbon export and its presumed drivers (primary production, mesozooplankton grazing) between warm and neutral years. Mesozooplankton fecal pellet enumeration and phaeopigment measurements both showed that fecal pellets were the dominant contributor to export in productive upwelling regions. In more oligotrophic regions, fluxes were dominated by amorphous marine snow with negligible pigment content. We found no evidence for a significant shift in the relationship between mesozooplankton grazing rate and chlorophyll concentration. However, mass-specific grazing rates were lower at low-to-moderate chlorophyll concentrations during warm years relative to neutral years. We also detected a significant difference in the relationship between phytoplankton primary production and photosynthetically active radiation between years: at similar irradiance and nutrient concentrations, productivity decreased during the warm events. Whether these changes resulted from species composition changes remains to be determined. Overall, our results suggest that the processes driving export remain similar during different climate conditions, but that species compositional changes or other structural changes require further attention. Highlights • Productivity, grazing, and export were measured during El Niño-neutral and warm years. • Carbon export and controlling processes were similar during both climatic conditions. • Net primary production was lower at similar light and nutrients during warm years. • When export was high, it was associated with sinking mesozooplankton fecal pellets. • When export was low, sinking particles were predominantly unrecognizable POM. [ABSTRACT FROM AUTHOR]

Although the Korean tidal flats in the Yellow Sea have been highlighted as a typical macrotidal system, so far, there have been no measurements of the sediment erodibility and critical shear stress for erosion ( τ ce ). Using the Gust erosion microcosm system, a series of field experiments has been conducted in the Ganghwa tidal flat to investigate quantitatively the effects of biogenic materials on the erodibility of intertidal cohesive sediments. Four representative sediment cores with different surficial conditions were analyzed to estimate the τ ce and eroded mass. Results show that τ ce of the “free” sediment bed not covered by any biogenic material on the Ganghwa tidal flat was in the range of 0.1–0.2 Pa, whereas the sediment bed partially covered by vegetation ( Phragmites communis ) or fecal pellets had enhanced τ ce up to 0.45–0.6 Pa. The physical presence of vegetation or fecal pellets contributed to protection of the sediment bed by blocking the turbulent energy. An inverse relationship between the organic matter included in the eroded mass and the applied shear stress was observed. This suggests that the organic matter enriched in a near-bed fluff layer is highly erodible, and the organic matter within the underlying sediment layer becomes depleted and less erodible with depth. Our study underlines the role of biogenic material in stabilizing the benthic sediment bed in the intertidal zone. [ABSTRACT FROM AUTHOR]

Copepod fecal pellets are ubiquitous throughout the oceans. Their production and export can represent a highly efficient pathway of carbon export. However, the role these fecal pellets play in carbon export in the Changjiang (Yangtze) River estuary is not well known. Two cruises were carried out in the Changjiang estuary in the spring and summer of 2013, during which time carbon biomass, production, and export of copepod fecal pellets were studied. Spring and summer fecal pellet carbon biomass ranged 0.30–1.01 mg C/m3 (mean=0.56±0.20 mg C/m3) and 0.31–1.18 mg C/m3 (mean=0.64±0.24 mg C/m3), respectively, significantly lower than phytoplankton. At most stations, fecal pellet carbon biomass was higher in surface or subsurface layers than deeper layers. Production rates ranged 0.65–1.49 pellets/(ind.∙h) (mean=1.02±0.27 pellets/(ind.∙h)) in spring and 0.62–1.34 pellets/(ind.∙h) (mean=0.98±0.22 pellets/(ind.∙h)) in summer, within the range reported in previous studies. Higher production rates of fecal pellets occurred at stations with higher chlorophyll a concentrations, and production rates of copepods of size 500–1 000 μm greater than copepods >1 000 μm during both cruises. The potential export flux of fecal pellets was slightly higher in summer (mean=68.95±14.37 mg C/(m2 ∙d)) than spring (mean=52.08±11.33 mg C/(m2 ∙d)) owing to higher summer copepod abundances. To our knowledge, this study is the first of its kind in the Changjiang estuary, and it confirms the significant role of copepod fecal pellets in local carbon export. [ABSTRACT FROM AUTHOR]

The calanoid copepod Acartia steueri Smirnov, 1936 is a dominant embayment species in the temperate coastal waters of Sagami Bay, Japan and food concentration in the embayment area varies abruptly. In this study, we examined the biological responses of A. steueri in the embayment following an abrupt decrease in food concentration and subsequent starvation in the laboratory. Unlike other neritic species, A. steueri survived for 18 days and continued to produce eggs for 15 days under starvation. Dry weight, carbon weight, and C/N ratio of A. steueri under the high food condition were much higher than those of other Acartia copepods, while prosome length and nitrogen weight of A. steueri were similar. The length-weight relationship of A. steueri was atypical for marine planktonic copepods. Oillike droplets, similar to the oil sac in oceanic copepods, were observed in the body cavity of A. steueri raised at the high food condition for more than 10 days. In the field, the rapid accumulation of lipids during sporadic high food conditions might contribute to continue the metabolism and egg production under low food conditions until they encounter favorable food conditions again. Thus, the survival strategy to abrupt changes in food concentration or starvation might support the population of A. steueri in the embayment. [ABSTRACT FROM AUTHOR]

The amoeba Dictyostelium discoideum produces and secretes multilamellar bodies (MLBs) mainly composed of amoebal membranes upon digestion of bacteria. After their secretion, the fate of these MLBs remains unknown. The aim of this study was to determine if protozoa can internalize and digest secreted D. discoideum MLBs. Our results showed that MLBs were ingested by naive axenic D. discoideum cells (i. e. cells not exposed to bacteria and consequently not producing MLBs). Only a small fraction of the ingested MLBs were found in cells’ post-lysosomes compared to undigestible beads suggesting that naive amoebae digest them. D. discoideum MLBs were also ingested by the ciliates Tetrahymena pyriformis and Tetrahymena thermophila . MLBs internalized by the ciliates were compacted into pellets and expelled in the extracellular medium without obvious signs of degradation. The results of this study provide new insights on the biological function of MLBs and, considering that MLBs are also involved in bacteria packaging, suggest additional layers of complexity in microbial interactions. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) overlap in size with phytoplankton and can be ingested by zooplankton, transferring them to higher trophic levels. Copepods are the most abundant metazoans among zooplankton and the main link between primary producers and higher trophic levels. Ingestion of MPs has been investigated in the laboratory, but we still know little about the ingestion of MPs by zooplankton in the natural environment. In this study, we determined the concentration and characteristics of MPs down to 10 μm in zooplankton samples, sorted calanoid copepods, and fecal pellets collected in the Kattegat/Skagerrak Sea (Denmark). We found a median concentration of 1.7 × 10 -3 MPs ind -1 in the zooplankton samples, 2.9 × 10 -3 MPs ind -1 in the sorted-copepods, and 3 × 10 -3 MPs per fecal pellet. Most MPs in the zooplankton samples and fecal pellets were fragments smaller than 100 μm, whereas fibers dominated in the sorted copepods. Based on the collected data, we estimated a MP budget for the surface layer (0-18 m), where copepods contained only 3% of the MPs in the water, while 5% of the MPs were packed in fecal pellets. However, the number of MPs exported daily to the pycnocline via fecal pellets was estimated to be 1.4% of the total MPs in the surface layer. Our results indicate that zooplankton are an entry point of small MPs in the food web, but the number of MPs in zooplankton and their fecal pellets was low compared with the number of MPs found in the water column and the occurrence and/or ingestion of MPs reported for nekton. This suggests a low risk of MP transferring to higher trophic levels through zooplankton and a quantitatively low, but ecologically relevant, contribution of fecal pellets to the vertical exportation of MPs in the ocean.

Inclusions of wood debris loosened from pine-like trees are abundant in Baltic amber of Eocene and Oligocene age. The possibilities to find insect frass and excrement among wood debris are outlined and some examples are given. Comparison with the frass and excrement produced by present-day insects provide a possibility to identify insects even though their fossils are lacking. This information can be used to characterize former forest environments. Amber forests may have also covered Southern Finland, and this possibility is discussed. Furthermore, the presence of wood debris may be utilized to recognize amber fakes, which is important for both gem trade and paleontology. It is proposed that databases and identification keys of frass and excrement should be constructed.

Summary Iron is an essential nutrient for phytoplankton, but low concentrations limit primary production and associated atmospheric carbon drawdown in large parts of the world’s oceans [ 1, 2 ]. Lithogenic particles deriving from aeolian dust deposition, glacial runoff, or river discharges can form an important source if the attached iron becomes dissolved and therefore bioavailable [ 3–5 ]. Acidic digestion by zooplankton is a potential mechanism for iron mobilization [ 6 ], but evidence is lacking. Here we show that Antarctic krill sampled near glacial outlets at the island of South Georgia (Southern Ocean) ingest large amounts of lithogenic particles and contain 3-fold higher iron concentrations in their muscle than specimens from offshore, which confirms mineral dissolution in their guts. About 90% of the lithogenic and biogenic iron ingested by krill is passed into their fecal pellets, which contain ∼5-fold higher proportions of labile (reactive) iron than intact diatoms. The mobilized iron can be released in dissolved form directly from krill or via multiple pathways involving microbes, other zooplankton, and krill predators. This can deliver substantial amounts of bioavailable iron and contribute to the fertilization of coastal waters and the ocean beyond. In line with our findings, phytoplankton blooms downstream of South Georgia are more intensive and longer lasting during years with high krill abundance on-shelf. Thus, krill crop phytoplankton but boost new production via their nutrient supply. Understanding and quantifying iron mobilization by zooplankton is essential to predict ocean productivity in a warming climate where lithogenic iron inputs from deserts, glaciers, and rivers are increasing [ 7–10 ]. [ABSTRACT FROM AUTHOR]

Bacillus thuringiensis (Bt) synthesizes crystalline inclusions that are toxic to caterpillars (Lepidoptera) and other orders of invertebrates. Materials associated with 37 caterpillars from 16 species, collected while feeding on 15 different species of host plants in dry, cloud and rain forests located in the Área de Conservación Guanacaste in northwestern Costa Rica, were examined for the presence of Bt. From a total of 101 derived samples, 25 Bt isolates were cultured: 56% from host plant leaves, 8% from caterpillar guts and 36% from caterpillar fecal pellets. Bt was isolated from at least one sample in 38% of the systems constituted by the food plant, gut and fecal pellets corresponding to a single caterpillar. Four different morphologies of crystalline inclusions were observed, with bipyramidal and irregular crystal morphologies being the most prevalent. Rev. Biol. Trop. 54(2): 265-271. Epub 2006 Jun 01.Bacillus thuringiensis (Bt) sintetiza inclusiones cristalinas que resultan tóxicas para algunas larvas de lepidópteros y otros órdenes de invertebrados. Su presencia fue examinada en materiales asociados a 37 orugas de mariposas de 16 especies, las cuales fueron colectadas mientras se alimentaban en 15 especies diferentes de plantas hospederas en bosques secos, nubosos y húmedos localizados dentro del Área de Conservación Guanacaste (ACG) en el noroeste de Costa Rica. A partir de un total de 101 muestras se obtuvo 25 aislamientos de Bt: 56% a partir de material foliar de las plantas hospederas, 8% a partir del contenido intestinal de las larvas y 36% a partir de sus excrementos. Esta bacteria fue cultivada a partir de al menos uno de los 3 diferentes tipos de muestra asociados a una oruga particular (planta hospedera, intestino, excremento) en 38% de los casos posibles. En la colección de aislamientos obtenida se observaron cuatro morfologías de inclusiones cristalinas, siendo aquellas bipiramidales e irregulares las más prevalentes.

Copepods are important grazers on phytoplankton and contributors to carbon export, but their role is poorly understood in the Western Antarctic Peninsula (WAP), a region of high productivity and rapid climate warming. We conducted grazing and egestion experiments with large, dominant copepods each January from 2012 to 2014. We found higher gut evacuation rates (k), initial gut pigment and ingestion rates (I) for Calanus propinquus and Rhincalanus gigas compared with Calanoides acutus. Since k and I linearly increased with chlorophyll a for most species, ingestion rates were 4-70 times greater in more productive coastal regions than offshore, slope waters. Copepods have a low grazing impact on phytoplankton biomass (<1%) and productivity (1%, up to 11%) compared with the dominant WAP macro- and microzooplankton. Egestion rates were high (0.8-37.3 μgC ind.-1 day-1); however, ~58% of fecal pellets are retained in the upper water column. Daily carbon rations of ~1% indicated feeding on other carbon sources (protozoans and metazoans) to meet metabolic demands. However, during a coastal phytoplankton bloom, daily C rations increased to up to 13%, indicating increased reliance on phytoplankton. Future changes in the WAP plankton community may affect food web carbon flow and export. [ABSTRACT FROM AUTHOR]

Invertebrate and microbial marine communities associated with mammal bones are interesting and poorly understood habitats, mainly known from studies on deep-water whale remains. In order to characterize these communities in the shallow-water Mediterranean, we present here the results of a pioneering experiment using mammal bones. Minke whale, pig and cow bones were experimentally deployed on three different background communities: rocky substrate, soft-bottom and a Posidonia oceanica meadow. Bones were deployed for a year at about 20 m depth and collected every 3 months, and the invertebrate fauna colonizing the bones was identified to the lowest possible taxonomic level. As expected, mammal bones showed remarkable differences when compared with background communities. Within bones, four different clusters could be identified, primarily on the basis of the polychaete fauna, the most abundant and diverse group in the survey. Clusters A1-A3 corresponded to high to moderately altered successional stages composed by a fauna closer to that of anthropogenically enriched shallow-water environments. These clusters were characterized by the occurrence of the opportunist polychaetes Ophryotrocha puerilis, Neanthes caudata (Cluster A1), Protodorvillea kefersteini (Cluster A2) and Ophryotrocha alborana (Cluster A3). Cluster B was characterized by the presence of the polychaete Oxydromus pallidus together with typical invertebrate background fauna, which suggests that this community, after a year of deployment, was closer to that found in natural conditions. As opposed to similar shallow-water studies in other geographic areas, no occurrence of the polychaete Osedax (commonly known as bone-eating worms) was reported from our experiments. Apart from the study on the invertebrate communities, insights about the population dynamics of three of the most abundant species ( O. puerilis, O. alborana, N. caudata) are given as well as remarks on a hypothetical trophic network based on fecal pellet analysis. [ABSTRACT FROM AUTHOR]

The difficulty of collecting occurrence and population dynamics data in mammalian populations of low density poses challenges for making informed management decisions. We assessed the use of scat-detection dogs to search for fecal pellets in a low density moose (Alces alces) population in the Adirondack Park in New York State, and the success rate of DNA extraction from moose fecal pellets collected during the surveys. In May 2008, two scat-detection dog teams surveyed 20, 4-km transects and located 138 moose scats. In 2011 we successfully amplified DNA from 39 scats (28%) and were able to uniquely identify 25 individuals. Improved storage protocols and earlier lab analysis would increase the amplification success rate. Scat-detection dogs proved to be a reasonable, non-invasive method to collect useful data from the low density moose population in the Adirondack Park. [ABSTRACT FROM AUTHOR]

The sediment chronology was determined using Lead-210 (Pb) and Cesium-137 (Cs) dating method. Profile distributions of Polonium-210 (Po) and Pb were evaluated with regarding to sediment porosity, core location, bottom currents and prevalent winds. Max. Po and Pb activity concentrations are found as 193.83 ± 4.43 and 187.84 ± 4.84 Bq kg respectively. According to vertical radionuclide (Po/Pb) ratios, sediments especially in east part of the lake are rich with respect to the fecal pellets. Residence time of the Pb is calculated as 1.9 months in the lake. Average sedimentation rate (0.359 ± 0.012 cm year) in central area is higher than the near shore (0.137 ± 0.006 cm year) one in Lake Bafa. [ABSTRACT FROM AUTHOR]

We investigated and quantified defecation rates of crude oil by 3 species of marine planktonic copepods ( Temora turbinata , Acartia tonsa , and Parvocalanus crassirostris ) and a natural copepod assemblage after exposure to mechanically or chemically dispersed crude oil. Between 88 and 100% of the analyzed fecal pellets from three species of copepods and a natural copepod assemblage exposed for 48 h to physically or chemically dispersed light crude oil contained crude oil droplets. Crude oil droplets inside fecal pellets were smaller (median diameter: 2.4–3.5 μm) than droplets in the physically and chemically dispersed oil emulsions (median diameter: 6.6 and 8.0 μm, respectively). This suggests that copepods can reject large crude oil droplets or that crude oil droplets are broken into smaller oil droplets before or during ingestion. Depending on the species and experimental treatments, crude oil defecation rates ranged from 5.3 to 245 ng-oil copepod −1 d −1 , which represent a mean weight-specific defecation rate of 0.026 μg-oil μg-C copepod 1 d −1 . Considering a dispersed crude oil concentration commonly found in the water column after oil spills (1 μl L −1 ) and copepod abundances in high productive coastal areas, copepods may defecate ∼1.3–2.6 mg-oil m −3 d −1 , which would represent ∼0.15%–0.30% of the total dispersed oil per day. Our results indicate that ingestion and subsequent defecation of crude oil by planktonic copepods has a small influence on the overall mass of oil spills in the short term, but may be quantitatively important in the flux of oil from surface water to sediments and in the transfer of low-solubility, toxic petroleum hydrocarbons into food webs after crude oil spills in the sea. [ABSTRACT FROM AUTHOR]

Several works have evidenced in the past the importance and influence of plants and terrestrial invertebrates in metal availability in soils and sediments through changes in metal speciation. In contrast, the impact of estuarine invertebrates and fishes in this process has been poorly explored. The partition of metals in estuarine surface sediments was studied in a controlled environment according to four operationally defined fractions. Sediments were analyzed before and after the passage through the gut of two detritivorous species. Scrobicularia plana feeds on the bottom and suspended sediment particles through the inhalant siphon. Liza ramada is an interface feeder, filtering the superficial layer of the sediment and suspended particles in the water column. Cd, Cu and Ni bound to carbonates increased in the pellets of S. plana , compared with the ingested sediment, as did exchangeable Zn. Similarly, Cd and Zn bound to carbonates have also increased in the pellets of L. ramada ; on the contrary, a decrease of Ni was observable in the pellets of this fish. The outcome of the controlled experiments pointed to a potential increase in some metals' availability in the estuarine environment, as a result of the more mobile metal forms in the excreted fecal pellets. This draws the attention to a relevant impact of the trophic activity of both species, alongside with the potential enhancement brought to it by the bioturbation promoted by them, in the role that the estuary itself has as a contaminants' buffer. [ABSTRACT FROM AUTHOR]