Seasonal changes in community composition and trophic structure of fish populations of five salt marshes along the Essex coastline, United Kingdom

European intertidal salt marshes are important nursery sites for juvenile fish and crustaceans. Due to the increasing threat of habitat loss, the seasonal changes of salt marsh fish communities need to be understood in order to appreciate the ecological and economic importance of the saltmarsh habitat. This study was the first in Great Britain to investigate the seasonal changes of salt marsh fish communities and the variation in community structure between closely located marsh habitats. Between February 2007 and March 2008, five marshes on three estuaries of the Essex coastline were sampled using flume nets to block off intertidal creeks at high tide. Fourteen fish species were caught. The community overall was dominated by three species that made up 91.6% of the total catch: the common goby Pomatoschistus microps (46.2% of the total catch), juvenile herring Clupea harengus (24.3%), and juvenile and larval sea bass Dicentrarchus labrax (21.2%). Cluster analysis demonstrated clear seasonal patterns, with some community structures unique to specific marshes or estuaries. The marsh fish community shifts from a highly diverse community during spring, to a community dominated by D. labrax and P. microps in autumn, and low diversity during winter months. Gravimetric stomach content analysis of fish community identified three main trophic guilds; macroinvertivores, planktivores and omnivores. The macroinvertivore feeding guild contained D. labrax and P. microps, the two most frequently occurring species. This investigation demonstrates the importance of British salt marshes as nursery habitats for commercial fish species.     

A deep burrowing sipunculan of ecological and geochemical importance

In late 1980s, a dense network of deep capillary burrows was reported on the Vøring Plateau, Nordic Seas, and associated with a sipunculan belonging to the genus Nephasoma. This sipunculan was responsible for rapid transport of organic matter from the sediment surface down a deep burrow network. Over 460 specimens belonging to the genus Nephasoma were collected from the deep Nordic Seas during four cruises from 2000–2005 and four species identified: Nephasoma abyssorum abyssorum, N. diaphanes diaphanes, N. diaphanes corrugatum and N. lilljeborgi. The species responsible for the deep burrows and rapid subduction of organic matter can now be confirmed as Nephasoma lilljeborgi. Deep burrows associated with N. lilljeborgi were observed on the Vøring Plateau, Bear Island Fan, Svalbard Margin and Yermak Plateau and may be a seabed feature endemic to the Nordic Seas region. N. lilljeborgi could have a significant role in influencing the ecology and geochemistry of the Nordic Seas region. It is recommended that future benthic community studies in the Nordic Seas region confirm the species identity of sipunculan specimens in order to determine the ecological and geochemical importance of the specimens.     

Sieve‐bucket for rapid field separation of macrofauna from bottom samples (note)

A lidded, 18‐litre sieve bucket was used to separate benthic macroinvertebrates from samples of mud taken with an Ekman grab. The device is operated in shallow water near the shore, and an entire Ekman grab sample (up to 10 litres) can be sieved in 5–10 min.     

Hooker's sea lions in southern New Zealand

The discovery at Stewart Island of a hauling‐out ground regularly used by Hooker's sea lions (Phocarctos hooked) is described, and recent sightings of sea lions in southern New Zealand are reported. An attempted copulation between a male Hooker's sea lion and a dead female fur seal (Arctocephalus forsteri) is also described.     

Evidence for distinct proportions of subducted oceanic crust and lithosphere in HIMU-type mantle beneath El Hierro and La Palma, Canary Islands

Shield-stage high-MgO alkalic lavas from La Palma and El Hierro (Canary Islands) have been characterized for their O-Sr-Nd-Os-Pb isotope compositions and major-, trace-, and highly siderophile-element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundances. New data are also reported for associated evolved rocks, and entrained xenoliths. Clear differences in Pd/Ir and isotopic ratios for high Os (>50 ppt) lavas from El Hierro (δ¹⁸O_olivine = 5.17 ± 0.08‰; ⁸⁷Sr/⁸⁶Sr = 0.7029 to 0.7031; ε_Nd = +5.7 to +7.1; ¹⁸⁷Os/¹⁸⁸Os = 0.1481 to 0.1750; ²⁰⁶Pb/²⁰⁴Pb = 19.1 to 19.7; Pd/Ir = 6 ± 3) versus those from La Palma (δ¹⁸O_olivine = 4.87 ± 0.18‰; ⁸⁷Sr/⁸⁶Sr = 0.7031 to 0.7032; ε_Nd = +5.0 to +6.4; ¹⁸⁷Os/¹⁸⁸Os = 0.1421 to 0.1460; ²⁰⁶Pb/²⁰⁴Pb = 19.5 to 20.2; Pd/Ir = 11 ± 4) are revealed from the dataset.Crustal or lithospheric assimilation during magma transport cannot explain variations in isotopic ratios or element abundances of the lavas. Shallow-level crystal-liquid fractionation of olivine, clinopyroxene and associated early-crystallizing minerals (e.g., spinel and HSE-rich phases) controlled compatible element and HSE abundances; there is also evidence for sub-aerial degassing of rhenium. High-MgO lavas are enriched in light rare earth elements, Nb, Ta, U, Th, and depleted in K and Pb, relative to primitive mantle abundance estimates, typical of HIMU-type oceanic island basalts. Trace element abundances and ratios are consistent with low degrees (2-6%) of partial melting of an enriched mantle source, commencing in the garnet stability field (?110 km). Western Canary Island lavas were sulphur undersaturated with estimated parental melt HSE abundances (in ppb) of 0.07 ± 0.05 Os, 0.17 ± 0.16 Ir, 0.34 ± 0.32 Ru, 2.6 ± 2.5 Pt, 1.4 ± 1.2 Pd, 0.39 ± 0.30 Re. These estimates indicate that Canary Island alkali basalts have lower Os, Ir and Ru, but similar Pt, Pd and Re contents to Hawai’ian tholeiites.The HIMU affinities of the lavas, in conjunction with the low δ¹⁸O_olivine and high ²⁰⁶Pb/²⁰⁴Pb for La Palma, and elevated ¹⁸⁷Os/¹⁸⁸Os for El Hierro implies melting of different proportions of recycled oceanic crust and lithosphere. Our preferred model to explain isotopic differences between the islands is generation from peridotitic mantle metasomatised by <10% pyroxenite/eclogite made from variable portions of similar aged recycled oceanic crust and lithosphere. The correspondence of radiogenic ²⁰⁶Pb/²⁰⁴Pb, ¹⁸⁷Os/¹⁸⁸Os, elevated Re/Os and Pt/Os, and low-δ¹⁸O in western Canary Island lavas provides powerful support for recycled oceanic crust and lithosphere to generate the spectrum of HIMU-type ocean island basalt signatures. Persistence of geochemical heterogeneities throughout the stratigraphies of El Hierro and La Palma demonstrate long-term preservation of these recycled components in their mantle sources over relatively short-length scales (∼50 km).     

The geochemistry of primary and weathered oil shale and coquina across the Julia Creek vanadium deposit (Queensland, Australia)

A significant resource of vanadium and molybdenum exists near Julia Creek, Australia, where the middle Cretaceous organic-rich Toolebuc Formation lies between 0 and 25 m of the surface. We present and discuss a comprehensive geochemical study of the Toolebuc Formation and its enclosing stratigraphy near Julia Creek to understand this ore deposit. V and Mo contents in fresh facies are strongly associated with total organic carbon (TOC) contents, but not with Al or CaCO₃; this suggests that V and Mo were originally concentrated in the organic fraction. However, chemical extractions using H₂O₂ indicate that Mo was originally concentrated in pyrite. The data also suggest that V was mobilised from organic matter during early diagenesis and became associated with clays as little V was extracted by H₂O₂ in the fresh samples. TOC contents in the Toolebuc Formation were removed during weathering, residually enriching trace metals including V and Mo, and as a result, the TOC relationship with V and Mo disintegrates. With weathering, both V and Mo predominantly became associated with iron oxide/hydroxide phases (and possibly other unidentified phases) as these elements in the weathered facies were highly soluble in the sodium citrate–sodium dithionite digestion. Large shale-hosted V and Mo deposits such as Julia Creek offer a potentially viable alternative to the currently mined magnetite-hosted deposits. A thorough understanding of the formation and host mineral phases for V and Mo of these shale deposits, however, is critical to ensure that these valuable metals can be feasibly extracted.