| 1. |
- Garcia-Martin, E. Elena, et al.
(författare)
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Sources, Composition, and Export of Particulate Organic Matter Across British Estuaries
- 2023
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Ingår i: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 128:4
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Tidskriftsartikel (refereegranskat)abstract
- Estuaries receive and process a large amount of particulate organic carbon (POC) prior to its export into coastal waters. Studying the origin of this POC is key to understanding the fate of POC and the role of estuaries in the global carbon cycle. Here, we evaluated the concentrations of POC, as well as particulate organic nitrogen (PON), and used stable carbon and nitrogen isotopes to assess their sources across 13 contrasting British estuaries during five different sampling campaigns over 1 year. We found a high variability in POC and PON concentrations across the salinity gradient, reflecting inputs, and losses of organic material within the estuaries. Catchment land cover appeared to influence the contribution of POC to the total organic carbon flux from the estuary to coastal waters, with POC contributions >36% in estuaries draining catchments with a high percentage of urban/suburban land, and <11% in estuaries draining catchments with a high peatland cover. There was no seasonal pattern in the isotopic composition of POC and PON, suggesting similar sources for each estuary over time. Carbon isotopic ratios were depleted (-26.7 +/- 0.42 parts per thousand, average +/- sd) at the lowest salinity waters, indicating mainly terrigenous POC (TPOC). Applying a two-source mixing model, we observed high variability in the contribution of TPOC at the highest salinity waters between estuaries, with a median value of 57%. Our results indicate a large transport of terrigenous organic carbon into coastal waters, where it may be buried, remineralized, or transported offshore. Plain Language Summary Estuaries transport and process a large amount terrigenous particulate organic matter (i.e., carbon and nitrogen) prior to its export to coastal waters. In order to understand the fate of organic carbon and the role of estuaries in the global carbon cycle it is essential to improve our knowledge on its composition, origin, and amount of carbon transported. We quantified the elemental concentrations and stable isotopes composition of carbon and nitrogen to quantify the amount of terrigenous particulate organic matter transported by 13 British estuaries, which drain catchments of diverse land cover under different hydrological conditions. We found a great variability in particulate organic carbon (POC) and particulate organic nitrogen concentrations across the salinity gradient, implying inputs, and losses of material within the estuaries. Each estuary had similar sources of particulate material throughout the year. In most of the estuaries, the POC had a terrigenous origin at the lowest salinity waters. The terrigenous organic carbon contribution decreased toward coastal waters with an average contribution of 57% at the highest salinity waters, indicating a large transport of terrigenous organic carbon into coastal waters.
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| 4. |
- Babcock, L.E., et al.
(författare)
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Anatomy, paleoecology, and taphonomy of the trilobite Buenellus from the Sirius Passet biota (Cambrian), North Greenland
- 2002
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Specimens of the nevadiid trilobite Buenellus higginsi from the Sirius Passet Biota (Buen Formation: Cambrian) of North Greenland show a combination of features reflecting both biomineralized and non-biomineralized anatomy, and providing direct or indirect evidence of paleoecologic associations and taphonomic history. Buenellus illustrates some key aspects of the role that trilobites played in the Early Paleozoic Marine Revolution (apparently serving as both predator and prey); its role in sediment-excavation, however, is unknown. The Sirius Passet Biota has a low diversity and low abundance of mineralizing organisms. Buenellus specimens, which account for most of the biomineralized skeletal parts, are normally preserved as decalcified, articulated exoskeletons, parallel to bedding. Their composition is dominated by clay minerals, although quartz, chlorite, muscovite, and chloritoid, are present, indicating metamorphism of shale to greenschist grade. Specimens of B. higginsi were preferentially oriented ventral-up as collected; this suggests both that minor current reorientation of remains occurred on the sea floor, and that strata at the Sirius Passet locality are overturned. Carnivory on B. higginsi is implied by the remains of anomalocaridids and other potential predators, and by sublethal predation scars. Slight disarticulation in the thoracic region of some fossils may have resulted from either decay or scavenging. Slender traces associated with various arthropod body fossils, including those of B. higginsi, suggests scavenging. Coprolites containing trilobite sclerites are unknown, and isolated, fragmentary sclerites are rare. Preserved non-biomineralized parts of B. higginsi are: 1, slender antennae projecting from under the exoskeleton; and 2, axial structures (inflated cavities lined with silica and limonite). Three types of axial structures are present: 1, a large cavity in the rear-subcentral part of the cephalon (interpreted as the stomach cavity); 2, a narrow, smooth-sided, medial tube that tapers slightly posteriorly (interpreted as the intestinal tract); and 3, metamerically divided pairs of sagitally located structures (interpreted as midgut glands). A carnivorous feeding habit is suggested by the lack of sediment-filled guts in B. higginsi.
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| 5. |
- Babcock, Loren E., et al.
(författare)
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Palaeobiology, taphonomy and stratigraphic significance of the trilobite BUENELLUS from the Sirius Passet Biota, Cambrian of North Greenland
- 2007
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Ingår i: Memoirs of the Association of Australasian Palaeontologists. - 0810-8889. ; 34, s. 401-418
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Tidskriftsartikel (refereegranskat)abstract
- The Sirius Passet Biota, collected from the lower Buen Formation (Cambrian Series 2, Stage 3), North Greenland, contains one species of trilobite, the nevadiid Buenellus higginsi Blaker, 1988. The species shows considerable morphological variation, especially in exoskeletal width. Many specimens of B. higginsi show some form of exceptionally preserved, non-biomineralised tissue. Structures interpreted as alimentary tracts and probable digestive glands are commonly preserved by silica and limonite. Antennae are rarely preserved, apparently through replication in clay minerals. Tendinous bars in the axial region also seem to be preserved by replication in clay minerals. Mineral-filled gut tracts in B. higginsi suggest they were fluid-filled at the time of burial, and that the species was a non-durophagous predator. Healed injuries, some of which are the result of unsuccessful predaceous attacks, are uncommon in B. higginsi. Other exoskeletons show evidence of post-mortem disruption, perhaps scavenging. Buenellus higginsi, one of the earliest known trilobites from Laurentia, seems to have played an important role in the Sirius Passet ecosystem, serving both as predator on, and prey for, contemporary animals.
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| 6. |
- Conway Morris, Simon, et al.
(författare)
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The earliest annelids : Lower Cambrian polychaetes from the Sirius Passet Lagerstätte, Peary Land, North Greenland
- 2008
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Ingår i: Acta Palaeontologica Polonica. - 0567-7920 .- 1732-2421. ; 53:1, s. 137-148
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Tidskriftsartikel (refereegranskat)abstract
- Apart from the Phyllopod Bed of the Burgess Shale (Middle Cambrian) polychaete annelids are practically unknown from any of the Cambrian Lagerstdtten. This is surprising both because their diversity in the Burgess Shale is considerable, while to date the Chengjiang Lagerstatte which is equally impressive in terms of faunal diversity has no reliable records of any annelids. Here we describe, on the basis of about 40 specimens, Phragmochaeta canicularis gen. et sp. nov. from the Lower Cambrian Sirius Passet Lagerstatte of Peary Land, North Greenland. This makes it by far the oldest known polychaete, with a likely age of lower to middle Atdabanian, The body consists of approximately 20 segments, each bearing notochaetae and neurochaetae. The former appeared to have formed a felt-like covering on the dorsum, whilst the neurochaetae projected obliquely to the longitudinal axis. Apart from minor differences in chaetal size at either end there is no other tagmosis. Details of the head are obscure, and presence of palps, tentacles and eyes are conjectural. Jaws appear to have been absent. The gut was straight, and flanked by massive longitudinal musculature. P. canicularis was evidently benthic, propelling itself on the neurochaetae, with the dorsal neurochaetae conferring protection. Its stratigraphic position and generalized appearance are consistent with P. canicularis being primitive, but the phylogenetic relationships within the polychaetes remain problematic, principally because of paucity of relevant morphological information.
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| 7. |
- Ebbestad, Jan Ove R., et al.
(författare)
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Predation on bellerophontiform molluscs in the Palaeozoic
- 2009
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Ingår i: Lethaia. - : Scandinavian University Press / Universitetsforlaget AS. - 0024-1164 .- 1502-3931. ; 42:4, s. 469-485
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Tidskriftsartikel (refereegranskat)abstract
- Shell repair assumed to result from failed predation is documented in 66 specimens of Ordovician-Carboniferous bellerophontiform tergomyan and gastropod molluscs to examine the relationship between the distribution and appearance of injuries, shell morphology and the internal anatomy of the molluscs, as well as the attack strategies of the presumed predators. Furthermore, the distribution of repaired injuries from failed attacks along the apertural margin as a reflection of the nature of the margin and emarginations is investigated. Bellerophontiform molluscs are ideal for this study because of their distinctive isostrophic morphology and the possibility to directly compare broad and narrow conchs with either deep or shallow medial emarginations. The results show that taxa with a deep medial emargination in the form of a slit have significantly more medial injuries than lateral ones. Near-equal frequencies of lateral and medial injuries in specimens with a shallow emargination (slit or sinus) suggest random distribution. Shell form (narrow or broad) does not exert overall control on the distribution of injuries except, perhaps, in some broad explanate shells with an insignificant medial emargination. While this suggests that it is the type of medial emargination that governs distribution of injuries in these forms, it is not clear if this is a result of passive selection due to structural geometry or preferential targeting by predators (i.e. site-specific mode of attack). Predation strategies on bellerophontiform molluscs thus seem to be dependent on the morphological features of the shells rather than their interpretation as tergomyan or gastropod.
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| 8. |
- Ebbestad, Jan Ove R., 1967-, et al.
(författare)
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Shell injuries, repair and malformation in the early Cambrian mollusc Helcionella antiqua from Scania, Sweden
- 2022
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Ingår i: GFF. - : Taylor & Francis. - 1103-5897 .- 2000-0863. ; 144:3-4, s. 203-209
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Tidskriftsartikel (refereegranskat)abstract
- Three cases of repaired injuries and malformation in specimens of the helcionelloid mollusc Helcionella antiqua (Ki & UAELIG;r, 1917) from the lower Cambrian (Cambrian Series 2, Stage 4) Gislov Formation of southern Sweden document some of the oldest known durophagous attacks on Palaeozoic molluscs. Two of the injuries are developed as clefts, of which one had a severe effect on the continued growth of the shell. The third example is a large embayment removing large portions of the supra-apical part of the shell. A similar repaired injury is known in the slightly older mollusc Marocella mira Geyer, 1986. from Antarctica and Australia. The morphology of the injuries and the hydrodynamically quiet depositional setting suggests that the shell damage was caused by failed predatory attacks. The location of the repaired injuries suggests that the attacks may have targeted the head region of the molluscs, thus supporting an endogastrically coiled orientation of the shell in Helcionella. Only three repaired injuries in 252 Helcionella specimens were found, giving a shell repair frequency of 1.2%. All three examples occur in the larger size classes. The size-frequency distribution (N = 182) is strongly right skewed, which could suggest high input of juvenile specimens into the assemblage. The assemblage is interpreted as a time averaged and mixed death assemblage, albeit with good correspondence with the living shelly assemblage, due to a relatively thin, homogenous unit that may suggest within-habitat time averaging.
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| 9. |
- Geyer, Gerd, et al.
(författare)
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A remarkable Amgan (Middle Cambrian, Stage 5) fauna from the Sauk Tanga, Madygen region, Kyrgyzstan
- 2014
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Ingår i: Bulletin of Geosciences. - : Czech Geological Survey. - 1214-1119 .- 1802-8225. ; 89:2, s. 375-400
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Tidskriftsartikel (refereegranskat)abstract
- Early Middle Cambrian bituminous coquinoid limestones from a tectonically isolated outcrop in southwestern Kyrgyzstan yield a remarkably diverse fauna, with stem-group cnidarians, trilobites, rhynchonelliformean brachiopods, and other shelly fossils. The fossil site is in the northern foothills of the Turkestan Range and thus forms part of the westernmost extension of the South Tien Shan. The fauna includes two fairly well known trilobite species, Glabrella ventrosa Lermontova, 1940 and Dorypyge richthofeniformis Lermontova, 1940, that provide confident support for an Amgan age of the rocks. New described taxa include the stem-group cnidarian Cambroctoconus kyrgyzstanicus Peel sp. nov., the trilobite Olenoides sagittatus Geyer sp. nov., and the helcionelloid Manasoconus bifrons Peel gen. et sp. nov. Additional fossils within the samples include the trilobites Olenoides sp. A, Kootenia sp., and Pseudoeteraspis? sp.; the rhynchonelliform brachiopods Narynella cf. ferganensis (Andreeva, 1962), Narynella? sp., Austrohedra? sp. nov., and two species of uncertain generic affinity; the tommotiid Tesella sp.; the hyolithelminth Hyolithellus sp.; and the palaeoscolecid Hadimopanella oezgueli Gedik, 1977. Of particular interest is Cambroctoconus kyrgyzstanicus with an octagonal corallum and a sparsely septate calyx.
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| 10. |
- Geyer, Gerd, et al.
(författare)
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Elrathia hensonensisnomen novum, new replacement name for Elrathia groenlandica Geyer and Peel, 2017 (Trilobita, Ptychopariacea)
- 2020
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Ingår i: Journal of Paleontology. - : Cambridge University Press (CUP). - 0022-3360 .- 1937-2337. ; 94:5, s. 1007-1007
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Tidskriftsartikel (refereegranskat)abstract
- In an article by Geyer and Peel (2017, p. 288), we inadvertently coined a species-group name, Elrathia groenlandica Geyer and Peel, 2017 for a trilobite species of the superfamily Ptychopariacea. This name is a junior homonym of Elrathia? groenlandica Poulsen, 1927 and is thus invalid (ICZN Article 57.2; see International Commission on Zoological Nomenclature, 1999). We therefore propose Elrathia hensonensis new name as the replacement name for E. groenlandica Geyer and Peel, 2017. The new species name is derived from the Henson Gletscher area, North Greenland, the region where the type locality of this species is located.
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