Small Fecal Pellets Research Articles

Dominant tree species and earthworms affect soil aggregation and carbon content along a soil degradation gradient in an agricultural landscape

Soil organic matter (SOM) is considered an important determinant of soil fertility in tropical agroecosystems. While numerous studies have shown the value of agroforestry in increasing soil nutrients and improving crop yield, few have addressed the systematic impacts of duration of cultivation on soil aggregation and C storage in such systems. A study was conducted in South Nandi (Kenya) to assess spatial influence of three dominant trees (Croton megalocarpus, Eucalyptus grandis and Zanthoxylum gilletii) on soil aggregation and C content in agroforestry systems. The study was conducted in a chronosequence experimental set-up where farms were continuously cultivated for 10, 16 and 62 years since conversion from primary forest. It was hypothesized that soil aggregates and whole soil and aggregate-associated C would decrease with duration of cultivation, with the magnitude of influence being reduced by the presence of trees and abundance of earthworms and termites. Greater abundance of small macroaggregates and microaggregates were recorded in soils under the canopy of Z. gilletii with an average weight of 62.8 g and 9.4 g 100 g−1 of soil compared to 53.9 g and 3.1 g 100 g−1 in soils under C. megalocarpus and 48.7 g and 3.9 g 100 g−1 in soils under E. grandis, respectively. These differences could be attributed to the high number of endogeic earthworm species, Nematogenia lacuum (Ocnerodrilidae) in soils under the canopy of Z. gilletii trees. Since N. lacuum is a small-sized species (40–55 mm long), it produces small faecal pellets and thus, we could infer that this species may have contributed to the fragmentation of large macroaggregates into small macroaggregates and microaggregates. The C content decreased by almost 40% in soils under longer duration of cultivation, with higher magnitude of differences associated with Z. gilletii trees. Increased microbial population in earthworms’ casts can increase mineralization rates, which may explain the low aggregate-associated C content under Z. gilletii trees where high number of N. lacuum were recorded. This study shows the significance of specific trees in shaping soil aggregation process and soil C content which could have far-reaching implications for the long-term C storage in the soil and hence net contributions to climate change mitigation.

Small faecal pellets in Ordovician shelly fossils from Estonia, Baltoscandia

Small faecal pellets in Ordovician shelly fossils from Estonia, Baltoscandia

Small faecal pellets in Ordovician shelly fossils from Estonia, Baltoscandia

Small faecal pellets in Ordovician shelly fossils from Estonia, Baltoscandia

Growth and mortality of coccolithophores during spring in a temperate Shelf Sea (Celtic Sea, April 2015)

Coccolithophores are key components of phytoplankton communities, exerting a critical impact on the global carbon cycle and the Earth’s climate through the production of coccoliths made of calcium carbonate (calcite) and bioactive gases. Microzooplankton grazing is an important mortality factor in coccolithophore blooms, however little is currently known regarding the mortality (or growth) rates within non-bloom populations. Measurements of coccolithophore calcite production (CP) and dilution experiments to determine microzooplankton (≤63 µm) grazing rates were made during a spring cruise (April 2015) at the Central Celtic Sea (CCS), shelf edge (CS2), and within an adjacent April bloom of the coccolithophore Emiliania huxleyi at station J2.CP at CCS ranged from 10.4 to 40.4 µmol C m−3 d−1 and peaked at the height of the spring phytoplankton bloom (peak chlorophyll-a concentrations ∼6 mg m−3). Cell normalised calcification rates declined from ∼1.7 to ∼0.2 pmol C cell−1 d−1, accompanied by a shift from a mixed coccolithophore species community to one dominated by the more lightly calcified species E. huxleyi and Calciopappus caudatus. At the CCS, coccolithophore abundance increased from 6 to 94 cells mL−1, with net growth rates ranging from 0.06 to 0.21 d−1 from the 4th to the 28th April. Estimates of intrinsic growth and grazing rates from dilution experiments, at the CCS ranged from 0.01 to 0.86 d−1 and from 0.01 to 1.32 d−1, respectively, which resulted in variable net growth rates during April. Microzooplankton grazers consumed 59 to >100% of daily calcite production at the CCS. Within the E. huxleyi bloom a maximum density of 1986 cells mL−1 was recorded, along with CP rates of 6000 µmol C m−3 d−1 and an intrinsic growth rate of 0.29 d−1, with ∼80% of daily calcite production being consumed.Our results show that microzooplankton can exert strong top-down control on both bloom and non-bloom coccolithophore populations, grazing over 60% of daily growth (and calcite production). The fate of consumed calcite is unclear, but may be lost either through dissolution in acidic food vacuoles, and subsequent release as CO2, or export to the seabed after incorporation into small faecal pellets. With such high microzooplankton-mediated mortality losses, the fate of grazed calcite is clearly a high priority research direction.

Copepod faecal pellet transfer through the meso- and bathypelagic layers in the Southern Ocean in spring

Abstract. The faecal pellets (FPs) of zooplankton can be important vehicles for the transfer of particulate organic carbon (POC) to the deep ocean, often making large contributions to carbon sequestration. However, the routes by which these FPs reach the deep ocean have yet to be fully resolved. We address this by comparing estimates of copepod FP production to measurements of copepod FP size, shape, and number in the upper mesopelagic (175–205 m) using Marine Snow Catchers, and in the bathypelagic using sediment traps (1500–2000 m). The study is focussed on the Scotia Sea, which contains some of the most productive regions in the Southern Ocean, where epipelagic FP production is likely to be high. We found that, although the size distribution of the copepod community suggests that high numbers of small FPs are produced in the epipelagic, small FPs are rare in the deeper layers, implying that they are not transferred efficiently to depth. Consequently, small FPs make only a minor contribution to FP fluxes in the meso- and bathypelagic, particularly in terms of carbon. The dominant FPs in the upper mesopelagic were cylindrical and elliptical, while ovoid FPs were dominant in the bathypelagic. The change in FP morphology, as well as size distribution, points to the repacking of surface FPs in the mesopelagic and in situ production in the lower meso- and bathypelagic, which may be augmented by inputs of FPs via zooplankton vertical migrations. The flux of carbon to the deeper layers within the Southern Ocean is therefore strongly modulated by meso- and bathypelagic zooplankton, meaning that the community structure in these zones has a major impact on the efficiency of FP transfer to depth.

Vertical flux and degradation rates of copepod fecal pellets in a zooplankton community dominated by small copepods

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 323:195-204 (2006) - doi:10.3354/meps323195 Vertical flux and degradation rates of copepod fecal pellets in a zooplankton community dominated by small copepods Louise K. Poulsen*, Thomas Kiørboe Danish Institute for Fisheries Research, Department of Marine Ecology and Aquaculture, Kavalergården 6, 2920 Charlottenlund, Denmark *Email: lkp@dfu.min.dk ABSTRACT: Sediment trap studies have revealed that copepod fecal pellets can be degraded at high rates in the sea, and copepods, particularly of the order Cyclopoida, have been implicated as the main degraders of these fecal pellets. A field budget of copepod fecal pellet production, degradation and sedimentation was constructed from water column and sediment trap samples as well as from shipboard incubations during a 7 d late-summer period in the North Sea. In addition, fecal pellet degradation due to the activity of copepods and other zooplankton organisms >200 µm was estimated from shipboard experiments. The copepod community was dominated by the cyclopoid copepod Oithona similis. Only 3 to 39% of the fecal pellets produced in the upper 50 m of the water column were collected by sediment traps at 50 m, corresponding to specific degradation rates of fecal pellets of 1 to 3 d–1. Accordingly, the fraction of suspended fecal pellets lost through sinking (sinking losses) and estimated pellet sinking velocities were low, and residence times short. Small fecal pellets were degraded at higher rates than larger fecal pellets. However, copepods and other zooplankton organisms >200 µm did not play an important role in the degradation of fecal pellets, since the estimated degradation due to zooplankton was 3 orders of magnitude lower than the total degradation rates of fecal pellets in the water column. This generally challenges the anticipated role of copepods in retarding the vertical flux of their own fecal pellets, and indicates that smaller plankton organisms (<200 µm) have an important role in degrading fecal pellets in the sea. KEY WORDS: Vertical flux · Fecal pellet · Degradation rate · Copepod · North Sea Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 323. Online publication date: October 05, 2006 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2006 Inter-Research.

Egestion of non-pellet-bound fecal material from the copepod Acartia tonsa: implication for vertical flux and degradation

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 293:131-142 (2005) - doi:10.3354/meps293131 Egestion of non-pellet-bound fecal material from the copepod Acartia tonsa: implication for vertical flux and degradation Michael Olesen1,*, Solvita Strake2, Andris Andrushaitis2 1Marine Biological Laboratory, University of Copenhagen, 3000 Helsingør, Denmark2Institute of Aquatic Ecology, University of Latvia, 2169 Riga, Latvia *Email: molesen@bi.ku.dk ABSTRACT: Only a minor fraction of copepod defecation appears to leave the upper water column as fast-sinking fecal pellets in coastal waters. This study suggests that most egested matter from copepods is retained in the water column because (1) >50% of fecal matter is released as small, slowsinking particles that are not surrounded by a peritrophic membrane and (2) small fecal pellets sink slowly and are degraded rapidly. The production, appearance and fate of fecal material from the calanoid copepod Acartia tonsa (fed on 2 different phytoplankton species, the cryptophyte Rhodomonas salina and the diatom Skeletonema costatum) was followed in association with the grazing activity of the copepod in a laboratory experiment. For both diets, >50% of the defecation was released as dispersed small (<10 mm) non-pellet-bound particles. The diatom was less suitable as a food item than the flagellate and led to a 3 times higher rate of grazing and egestion. Nevertheless, specific assimilation and egg production per female were 2 times higher for the Rhodomonas diet versus the Skeletonema diet. As a result, the total egestion comprised 18% of the ingestion of Rhodomonas and 27% of the Skeletonema ingestion. In terms of vertical loss, sinking rates for both types of fecal pellets were ca. 5 m d–1 and, in terms of degradation, ca. 0.5 d–1 (18°C) in the absence of copepods. Transferring these findings to similar neritic conditions suggests that 60% of the fecal pellets from copepods will be recycled within a 15 m deep mixed layer and that >80% of the total fecal matter can be expected to be retained when the unbound fecal material is also included. KEY WORDS: Zooplankton · Grazing · Chlorophyll · Fecal pellets · Egestion · Assimilation · Degradation · Vertical flux Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 293. Online publication date: June 02, 2005 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2005 Inter-Research.

A Microtexture Study of Palygorskite-Rich Sediments from the Hawthorne Formation, Southern Georgia, by Transmission Electron Microscopy and Atomic Force Microscopy

AbstractA microtexture analysis by TEM and AFM of palygorskite deposits from the Hawthorne Formation, southern Georgia is given. Palygorskite is the dominant mineral comprising an average of 65–70% of the sample volume with smaller volumes of smectite, illite and kaolinite. Morphologic observations indicate that the palygorskite formed in an unconfined environment, such as in the water column or in open-pore space. Some palygorskite textures appear to be secondary growths filling voids. An unusual texture is observed where smectite or illite-smectite (Reichweite, R = 0) form epitaxially on detrital illite and kaolinite particles. Oxides of Fe and Ti are common, and authigenic cassiterite is present but rare. Apatite is a common trace mineral in these sediments and occurs in a variety of textures. Apatite occurs as clusters which are believed to be small fecal pellets. These clusters have been partially dissolved and recrystallized and the crystals in the clusters are 50–100 µm in diameter. Other apatite crystals occur either as single crystals or in clusters that are not associated with fecal pellets.The textural data of this study suggest that there was an evolving and complex mineralogical and geochemical system during and after deposition of the palygorskite deposits in the Hawthorne. The epitaxial overgrowths of smectite on detrital illite and kaolinite particles indicate an intermittent stratified water column occurring in the system. Freshwater was introduced into the system from the northeast of the Apalachicola embayment and overrode more saline water in the southwest portion of the embayment. The results of this study are consistent with previous environmental interpretations and provide additional details.

Ultrastructure, morphology and flux of microzooplankton faecal pellets in an east Antarctic fjord

Small copepods and protozoa are major contributors to heterotrophic biomass in Antarc- tic waters. They produce small (<300 µm) faecal pellets, the fates of which are largely unknown. We examined the distribution and abundance of microzooplankton and small faecal pellets in Ellis Fjord, east Antarctica. We determined statistical relationships between the abundance of microzooplankton and pellets, and examined pellet morphology and ultrastructure using light and scanning electron microscopy. Our results indicate species-specific differences in the morphology and fate of pellets produced by small copepods: Oithona similis and harpacticoid pellets were retained in upper waters, while Oncaea curvata and Paralabidocera antarctica pellets sank to depth. Protozoan pellets did not sink to depth irrespective of their source or morphology and despite the fact they can be larger than those produced by small copepods. The majority of microzooplankton pellets, composed of phyto- plankton that otherwise may have directly sedimented to depth, was retained in near surface waters and probably recycled and remineralised. Despite producing faecal aggregates, heterotrophic activ- ity of most microzooplankton do not contribute to vertical flux but instead support respiration of mat- ter in upper waters. This may reduce the vertical flux of particulate matter to depth, thereby reduc- ing the capacity of Antarctic waters to act as a carbon sink, with implications for global climate.

Some population sizes and effects of the Enchytraeidae (Oligochaeta) on soil structure in a selection of Scottish soils

This paper is a summary of the results obtained from an investigation of the occurrence of Enchytraeidae in several Scottish soils. Population counts from two sites, one consisting of a rotation of eight crops each grown on plots at four different pH levels and the other consisting of a mixed pine and larch forest, show the highest numbers of enchytraeids at low soil pH levels. Soil thin sections from five sites show that at low pH the main effects of enchytraeids on soil structure are (1) the production of a large number of small granules (faecal pellets) which later fuse to form a soil matrix, and (2) their deposition in channels, other pores and old roots. At higher pH levels enchytraeids consume earthworm aggregates and replace them with their small faecal pellets and they form new pores due to their burrowing activities.

Ecology of amorphous aggregations (marine snow) in the Northern Adriatic Sea. V. Role of fecal pellets in marine snow

Ecology of amorphous aggregations (marine snow) in the Northern Adriatic Sea. V. Role of fecal pellets in marine snow

Fluorometric detection of tracer particles used to study animal‐particle dynamics

I describe a fluorometric procedure to measure concentrations of fluorescent resin used as a tracer of particle dynamics. The technique has sufficient spectral resolution to estimate weights of very small volumes of marked sediment (equivalent to 15 µg mass) and to distinguish concentrations of individual tracer colors from background fluorescence. Concentrations of tracer particles in available and egested sediment were used to estimate sediment weight of small fecal pellets (15–35 µg) of deposit feeders and compared with volumetric measurements of the same pellets. Experiments with scintillation fluor indicated that the quantitative measurement of sediment weight can be performed in concert with radiolabeling techniques.

Gelatinous phytoplankton detritus aggregates on the Atlantic deep-sea bed

Phytoplankton detritus associated with spring and summer blooms of surface phytoplankton rapidly settles to the deepsea bottom at the Porcupine Seabight, North Atlantic, according to earlier descriptions. However, the causes of this large amount of phytodetrital sedimentation to the deep-sea bed were unknown. Detritus material in samples from the bottom and the water column were collected during the Biotrans IV cruise (July to August 1986) on RV “Meteor” to a site more distant from the shelf break (47°N, 20°W) with depths of about 4 500 m. Deposits most often encountered at the bottom were greenish gelatinous aggregates (ca 1 cm) consisting of amorphous mucous substance enclosing single, dispersed algal cells, skeletal elements of protists, and small faecal pellets. Coccolithiphorids (sometimes with preserved cytoplasm and nuclei) were abundant. The most prominent parts in terms of numbers and volumes within the gelatinous aggregates were round faecal pellets having a diameter of 5 to about 80 μm, and consisting of unidentifiable detrital material, folded membranes, and masses of green chlorophyte cells, 3 μm diam. The faecal pellets were identical to those found inside Phaeodaria (Radiolaria), which were collected at the same time in the water column. It is proposed that the loading of drifting phytoplankton-containing mucus flakes with phaeodarian faecal pellets and the entangling of this mucus with spiny phaeodarian cells are important factors in the formation of fast-sinking gelatinous aggregates.

Faunal micromorphological features in moder humus of some Western Canadian soils

Examination of soils extending from the Arctic and Alpine to the Boreal Forest and Prairie regions of Canada showed faunal fecal material to be a significant component of all organic-rich surface layers. In particular, Collembola and Enchytraeidae appeared to play a major role in the development of microstructures within the moder humus forms. The composition of pellets within the thin mull-like moder immediately below the moder layer reflected the indiscriminate feeding habits of Enchytraeids. Fecal material of Tipulid larvae were found throughout the upper layer of moder as well as within partially decomposed leaf litter. Diptera larvae deposited small fecal pellets widely within the moder often extending to an underlying mull-like moder layer. Casts of mull-like material produced by endogeic earthworms in the moder humus were observed as individual units in the Boreal Forest-Tundra region and as a thin welded layer in the Boreal Forest-Prairie region. Fecal pellets of Diplopoda were also present in moder humus from the Boreal Forest and Prairie regions. Oribatid mites produced very distinctive fecal pellets within cavities of partially decomposed plant tissue in all humus profiles. Although morphological similarities often made it difficult to differentiate between excrement produced by different fauna, the possibility of differences in contribution to the organic cycle and plant nutrition must be recognized.

RBE values and repair characteristics for colo-rectal injury after caesium 137 gamma-ray and neutron irradiation. II. Fractionation up to ten doses.

Early and late colo-rectal damage in mice have been assessed after 137Cs gamma irradiation and 3 MeV neutrons given as 1,2,5 or 10 fractions. Damage was measured by early changes in body weight, the late production of short faecal pellets and the pattern of lethality after irradiation. The data have been analysed in terms of the time course of expression of damage, fractionation effects and the RBE for neutrons over a wide range of doses per fraction (0.5-12.5 Gy neutrons, 3.5-33.5 Gy gamma rays). An initial epithelial denudation led to an early loss of weight, maximal at 11-17 days after irradiation. A dose-dependent weight reduction persisted over the animals' life-time. Deaths after localised pelvic gamma irradiation were progressive with no sharp demarcation between early or late phases of injury. The time course for lethality was qualitatively similar after neutrons. Beyond six months the rectum became constricted by fibrosis and a higher proportion of small faecal pellets was observed. At 6-15 months relatively shallow dose-response curves were obtained for this change. The sparing effect of fractionation was marked for the gamma-irradiated mice and almost absent after neutrons. A very high repair increment (11 Gy) was seen with two gamma-ray fractions of 20 Gy. At lower doses per fraction the proportion of each gamma-ray fraction recovered was 50-69% for all assays, i.e., similar to that for other normal tissues. There was a slight enhancement in the sparing effect for the late compared with the early assays over the lower dose range. The RBE was strongly dependent on dose per fraction because of the lack of reparable damage after neutrons. The RBE for both early and late effects was 5.0 at a neutron dose per fraction of 1 Gy. Extrapolation of the RBE data to lower doses, using the linear quadratic model, predicts a higher RBE for late (7.4-12.7) than for early damage (5.7-8.5) if gamma-ray doses below 5 Gy are used.

Sinking rates of natural copepod fecal pellets

Many pure samples of natural fecal pellets have been collected from mixed small copepods and from the pontellid copepod Anomalocera patersoni in the Ligurian Sea, using a specially designed pellet collection device. Sinking rates of fresh pellets and pellets aged up to 33 days have been determined at 14°C, the mean temperature of the essentially isothermal water column in the Ligurian Sea. Sinking rates of pellets collected during calm sea states increased with increasing pellet volume, but sinking rates of pellets collected during rough sea (Beaufort scale ≃6) showed little correlation with pellet size. Much of the variability in the sinking rate-pellet size relationships was the result of different pellet composition and compaction, but not pellet age. Pellets produced from laboratory diets of phytoplankton and phytoplankton-sediment mixes showed the expected wide variability in sinking rates, with sediment-ballasted pellets sinking much faster than pellets produced from pure algal diets; thus determination of vertical material fluxes in the sea using laboratory-derived fecal pellet sinking rates is unwarranted. Natural pellet sinking data for small copepods and A. patersoni have been combined with similar data for euphausiids, to yield sinking rates of roughly two orders of magnitude over three orders of magnitude in pellet volume. Pellets from small copepods sank at speeds too slow to be of much consequence to rapid material flux to the deep sea, but they undoubtedly help determine upper water distribution of materials. Recalculation of fecal pellet mass flux estimates from the literature, using our sinking rate data for natural small copepod pellets, yielded estimates about half those of previously published values. Earlier studies had concluded that small fecal pellets were of lesser significance to total material flux than fecal matter; our recalculation strengthens that conclusion. Pellets from large copepods and euphausiids, however, have the capability to transport materials to great depths, and probably do not substantially recycle materials near the surface. The fact that the majority of pellets which had previously been collected in deep traps by other workers were of a size comparable to pellets from our large copepods supports the contention that these larger pellets are the main ones involved in vertical flux.

Sedimentological Significance of Fecal Pellets of Macoma Balthica in the Minas Basin Bay of Fundy

ABSTRACT Intertidal sediments of the Minas Basin support an estimated 24 109Macoma balthica. Excreta occurs as either loose coils or strings of pseudofeces, or as small cylindrical fecal pellets, both of which are easily transported. Fecal pellets are picked up with fine sand and settle out of suspension with coarse silt. Some pellets last at least one tidal cycle before breaking down into sand grains and mucus-bound aggregates of mud and silt. Each clam produces about 0.5 g (dry weight)/day of excreta, most of which is resuspended by tidal currents. In the areas of highest recorded population densities (3.500/m2), feeding would remove about one foot of sediment (28 cm) per year. Total daily contribution of excreta to the Minas Basin by the 24 billion Macoma amounts to about 6 109 g (dry weight) of sediment or about 10,000 m3 of wet excreta. This material is likely a valuable food source and is distributed throughout the Minas Basin by tidal currents.