Erik E. Syvertsen

Chapter 2 – Marine Diatoms

This chapter provides an introductory biology of marine diatoms, their classification, heteromorphy, evolution, and critical evaluation. It consists of sections on classification as well as generic atlas. A diatom system is based on results from light and electron microscopy and constructed key to the diatom families. Diatoms reproduce vegetatively by binary fission resulting in formation of two new individuals within the parent cell frustule. The probable size range of the diatom cells are species dependent, and the specific variation may be as large as 8–10 times the length of the apical axis or the diameter. Despite the availability of other publications, there is still a need to fill the gap with respect to the global aspect, especially when identifying Marine diatoms at the specific level. The entire discussion aims to meet the morphological need of new diatom information as well as the classical identification literature. This comprehensive volume explores the two Polar Regions and has an ecological interpretation as well as a taxonomic part with the key to the study of marine diatom species. General characteristics of marine diatoms together with their life cycles have also been discussed.

A review ofPseudo-nitzschia, with special reference to the Skagerrak, North Atlantic, and adjacent waters

ThePseudo-nitzschia flora of the Skagerrak, North Atlantic, and adjacent waters, comprisingP. pungens, P. multiseries, P. seriata, P. fraudulenta, P. heimii, P. delicatissima, andP. pseudodelicatissima, has been examined. Except forP. australis, allPseudo-nitzschia species shown to produce the toxin domoic acid are present in the area although an outbreak of amnesic shellfish poisoning has never been reported. For comparison of morphological and taxonomic characters,Pseudo-nitzschia seriata f.obtusa, P. australis, P. subfraudulenta, P. subpacifica, P. lineola, P. inflatula, andP. cuspidata have been included in this investigation. Fine details of band structure and poroid occlusions, previously ignored or unresolved, have proven to add to the morphological distinction betweenP. pungens andP. multiseries, P. seriata andP. fraudulenta, P. seriata andP. australis, andP. delicatissima andP. pseudodelicatissima. Additional information on the structure of the proximal mantle compared to that of the valve face has revealed similarities in most of the species but differences betweenP. pungens andP. multiseries. The species seasonal and long-term distributional patterns during the sampling period (October 1978 through September 1993) in the Skagerrak area are outlined. The greatest abundances ofP. seriata, a cold-water species most likely restricted to the northern hemisphere, occurred in the spring, and those of the presumably cosmopolitan diatomsP. pungens, P. multiseries andP. pseudodelicatissima, in the autumn. WhereasP. multiseries seems to have decreased in abundance in the 1990s,P. pseudodelicatissima has apparently increased.

Proposed terminology and reporting units for sea ice algal assemblages

SummaryMany terms and units are used to describe the algae associated with sea ice. Most of these terms are open to misinterpretation and have been frequently misused. The use of a number of different units when reporting on experimental studies makes it difficul, if not impossible, to compare studies done by different investigators. In an attempt to avoid these ambiguities and to make comparisons easier, we here suggest some standard terms and repoting units that should be used when discussing ice algal assemblages.

Nitrogen uptake in the Weddell Sea during late winter and spring

Uptake rates of ammonium, nitrate and urea were measured during the EPOS leg 1 cruise to the Weddell Sea in October–November 1988 using the isotope 15N. Nitrate was the most important nitrogen source both for ice algae (f-ratio ≥0.88) and for phytoplankton in the water column (f-ratio ≥0.85). Indications of a gradual decrease in % new production with time were found in the outer marginal ice zone. Nitrogen uptake rates in ice algae from the sub-ice assemblage were light-limited at in situ irradiances. Significant regeneration of ammonium was found in ice algal samples only.

FOSSULA ARCTICA GEN. NOV., SPEC. NOV., A MARINE ARCTIC ARAPHID DIATOM

Fossula, gen. nov., type Fossula arctica spec, nov, is described from Arctic waters influenced by sea ice. It forms ribbon shaped colonies like Fragilariopsis and Fragilaria but differs from these genera in valve and band structure. It differs from Fragilariopsis by having a sternum in the middle of the valve, a labiate process and no raphe, and from Fragilaria (e.g. F. capucina, F. crotonensis and F. striatula) by the cell apices having one row of larger, elongate openings in the valve mantle midway between valve face and valve margin and another irregular row of smaller openings closer to the margin, and by bands with vertical columns of poroids. Fossula arctica is distinguished from Arctic Fragilariopsis species and from Fragilaria striatula also by the shape and location of the chloroplasts.

Ice algae during EPOS, leg 1: assemblages, biomass, origin and nutrients

Ice algae in infiltration assemblages were the dominating primary producers in the northwestern Weddell Sea during the austral spring 1988. Band and sub-ice assemblages were encountered at a few stations only. Maximum ice algal biomass measured was 424 μg Chl. a1−1 compared to less than 0.4 μg Chl. a1−1 in the water column. Biomass and nutrient concentrations in the infiltration layer decreased inward from the edge of ice floes. The composition of algal groups indicated that the concentric distribution was due to migration by mobile taxa. Various procedures were for melting of ice-containing samples of algae were tested. Melting in dialysis tubing seemed to have advantages over other methods, especially for cells to be used in physiological experiments.

“Linnaeus” and beyond: workshop report on multimedia tools for the identification and database storage of biodiversity

The Expert center for Taxonomic Identification distributes the Linnaeus compact disk (CD), with multimedia information on protists in Scandinavian coastal waters. The principal features of the program are discussed. Species-related information is presented on “cards” and can be accessed along a variety of paths, including taxonomic keys. Building on the Linnaeus program, ETI has developed a new multimedia database and identification system that can store and easily retrieve all sorts of species-related information: text descriptions, images (colour and black-and-white), sounds, movies, maps, synonyms, etc.