<i>Cocconeis molesta</i> Kütz., <i>C. diaphana</i> W.Sm. and <i>C. dirupta</i> W.Greg. (Bacillariophyta): type material, ambiguities and possible synonymies

F.T. Kützing introduced Cocconeis molesta with only an uninformative description and a poor illustration: C. molesta has small, oblong valves and is an epiphyte. Another species, Cocconeis diaphana, described by William Smith, is said to have larger valves than C. molesta, with frustules that are relatively oblong. Smith described two forms: one with a distinct fascia on its raphe valve (var. β), the other without this feature. A third species, Cocconeis dirupta was described by Gregory, who expressed doubts that it differed from C. diaphana. Finally, Cocconeis molesta var. crucifera Grunow was first introduced in Van Heurck’s Atlas but was subsequently treated by Van Heurck as a synonym of C. molesta. No previous account has examined the type material of these species. In this paper, we undertake that task and examine type slides and raw material in order to discriminate these different taxa. We conclude by recognizing three species: Cocconeis molesta Kütz., C. diaphana W.Sm. and C. dirupta W.Greg. Cocconeis diaphana var. β is considered to be a synonym of C. dirupta and C. molesta var. crucifera is considered to be a synonym of C. molesta. Lectotypes are designated for C. diaphana and C. dirupta

Two new marine species of Cocconeis (Bacillariophyceae) from the west coast of Sweden

This paper is part of a project of studying benthic diatom biodiversity on marine coastal regions of Sweden with focus on rare and less known species. Two new species of Cocconeis Ehrenb. are described from Vrångö, a small island in the west coast of Sweden. Both species were found as epiphytic on the green alga Ulva intestinalis L. Cocconeis magnoareolata Al-Handal, Riaux-Gob., R.Jahn & A.K.Wulff sp. nov. is a small species not exceeding 9 µm in length and characterized by having large subquadrangular areolae on the sternum valve. Cocconeis vrangoensis Al-Handal & Riaux-Gob. sp. nov. appears similar to some taxa of the ‘Cocconeis scutellum complex’, but differs by its stria density on both valves and variable features of the areola and valvocopula ultrastructure. Detailed descriptions based on light and electron microscopy examination, a comparison with closely related taxa, as well as a description of the habitat of both species are here presented

<i>Planothidium juandenovense</i> sp. nov. (Bacillariophyta) from Juan de Nova (Scattered Islands, Mozambique Channel) and other tropical environments: a new addition to the <i>Planothidium delicatulum</i> complex

Planothidium juandenovense sp. nov. (Bacillariophyta) is described from the marine tropical environments of Juan de Nova I. (Mozambique Channel), Rodrigues I. (Mascarene Archipelago) and from Guam (Northern Mariana Is., Pacific). This small and relatively rare taxon has short multiseriate striae on the sternum valve (SV), hooked raphe valve (RV) terminal raphe endings and no SV cavum or hoof–shaped area. This taxon has similarities with Planothidium delicatulum (Kütz.) Round et Bukht. and Planothidium septentrionale (Østrup) Round et Bukht. ex Rumrich et al., but also differences: e.g. a relatively narrow and rhombic SV sternum, void of areolae, with vestigial radiate structures and an uninterrupted marginal SV elevated crest or ‘crista marginalis’. P. juandenovense sp. nov. is compared to some other Achnanthales with short SV striae. Cocconeis quarnerensis var. lanceolata Jurilj and Planothidium quarnerense f. rhombica (Giffen) comb. nov. may be close to our new taxon

Distribution and morphology of the diatom genus Olifantiella Riaux-Gobin &amp;amp; Compère in Indonesian and Australian waters, including the description of O. gondwanensis sp. nov.

Samples from coastal tropical waters of Central Sulawesi, Bangka Island and Bawean Island in Indonesia and from the Great Barrier Reef at Fitzroy Island in Queensland, Australia were analysed for species composition of diatom assemblages with a focus on Olifantiella. Whereas samples from Fitzroy Island littoral in Australia retrieved only one species of Olifantiella, in Poso Bay, Indonesia, we observed at least six species. All established taxa were documented with light (LM) and scanning electron microscope (SEM) and principal component analysis (PCA) analysis was used to compare the species, based on the basic valve parameters of length, width, length to width ratio and striae density. A new species of the genus Olifantiella, O. gondwanensis is described from Australia. In addition, we showed the distinct nature of O. pilosella var. rhizophorae permitting to species status. Particular attention is placed on girdle bands in this genus

Source identification and distribution reveals the potential of the geochemical Antarctic sea ice proxy IPSO25

The presence of a di-unsaturated highly branched isoprenoid (HBI) lipid biomarker (diene II) in Southern Ocean sediments has previously been proposed as a proxy measure of palaeo Antarctic sea ice. Here we show that a source of diene II is the sympagic diatom Berkeleya adeliensis Medlin. Furthermore, the propensity for B. adeliensis to flourish in platelet ice is reflected by an offshore downward gradient in diene II concentration in >100 surface sediments from Antarctic coastal and near-coastal environments. Since platelet ice formation is strongly associated with super-cooled freshwater inflow, we further hypothesize that sedimentary diene II provides a potentially sensitive proxy indicator of landfast sea ice influenced by meltwater discharge from nearby glaciers and ice shelves, and re-examination of some previous diene II downcore records supports this hypothesis. The term IPSO25-Ice Proxy for the Southern Ocean with 25 carbon atoms-is proposed as a proxy name for diene II

Sinking Jelly-Carbon Unveils Potential Environmental Variability along a Continental Margin

Particulate matter export fuels benthic ecosystems in continental margins and the deep sea, removing carbon from the upper ocean. Gelatinous zooplankton biomass provides a fast carbon vector that has been poorly studied. Observational data of a large-scale benthic trawling survey from 1994 to 2005 provided a unique opportunity to quantify jelly-carbon along an entire continental margin in the Mediterranean Sea and to assess potential links with biological and physical variables. Biomass depositions were sampled in shelves, slopes and canyons with peaks above 1000 carcasses per trawl, translating to standing stock values between 0.3 and 1.4 mg C m2 after trawling and integrating between 30,000 and 175,000 m2 of seabed. The benthopelagic jelly-carbon spatial distribution from the shelf to the canyons may be explained by atmospheric forcing related with NAO events and dense shelf water cascading, which are both known from the open Mediterranean. Over the decadal scale, we show that the jelly-carbon depositions temporal variability paralleled hydroclimate modifications, and that the enhanced jelly-carbon deposits are connected to a temperature-driven system where chlorophyll plays a minor role. Our results highlight the importance of gelatinous groups as indicators of large-scale ecosystem change, where jelly-carbon depositions play an important role in carbon and energy transport to benthic systems