Microphytobenthos of Arctic Kongsfjorden (Svalbard, Norway): biomass and potential primary production along the shore line

During summer 2007, Arctic microphytobenthic potential primary production was measured at several stations around the coastline of Kongsfjorden (Svalbard, Norway) at ?5 m water depth and at two stations at five different water depths (5, 10, 15, 20, 30 m). Oxygen planar optode sensor spots were used ex situ to determine oxygen exchange in the overlying water of intact sediment cores under controlled light (ca. 100 ?mol photons m?2 s?1) and temperature (2–4°C) conditions. Patches of microalgae (mainly diatoms) covering sandy sediments at water depths down to 30 m showed high biomass of up to 317 mg chl a m?2. In spite of increasing water depth, no significant trend in “photoautotrophic active biomass” (chl a, ratio living/dead cells, cell sizes) and, thus, in primary production was measured at both stations. All sites from ?5 to 30 m water depth exhibited variable rates of net production from ?19 to +40 mg O2 m?2 h?1 (?168 to +360 mg C m?2 day?1) and gross production of about 2–62 mg O2 m?2 h?1 (17–554 mg C m?2 day?1), which is comparable to other polar as well as temperate regions. No relation between photoautotrophic biomass and gross/net production values was found. Microphytobenthos demonstrated significant rates of primary production that is comparable to pelagic production of Kongsfjorden and, hence, emphasised the importance as C source for the zoobenthos

Primary production in two shallow lakes with contrasting plant form dominance: A paradox of enrichment?

We estimated total lake plant biomass and primary net production in two shallow Swedish lakes that differ in nutrient loading and plant form dominance. In clearwater Lake Krankesjon (10 mu g chlorophyll a L-1), submerged macrophytes contributed more than phytoplankton and epiphyton to the estimated plant biomass. Estimated net primary production during May to September was 90-130, 1.2, and 14 g C m(-2) for phytoplankton, epiphyton, and submerged macrophytes, respectively. In turbid Lake Borringesjon (60-80 mu g chlorophyll a L-1), primary production by submerged macrophytes and periphyton was negligible. Although gross primary production of phytoplankton was high close to the water surface, estimated areal net primary production during May to September was low, -40 to +25 g C m(-2), as a result of self-shading and high respiration. Grazing pressure from zooplankton rarely exceeded 15% d(-1) in both lakes, indicating that phytoplankton production was not limited by grazing. Low gross epiphyton production could result from high grazing by macroinvertebrates and thus higher trophic transfer efficiency through the benthic than through the pelagic food web. Provided that conditions in Lake Borringesjon reflect previous turbid state conditions in Lake Krankesjon, our results may explain why a shift to a clearwater state was followed by increased biomass of higher trophic levels. Our results also support the paradox of enrichment hypothesis, which predicts lower productivity at high nutrient loading. Contrary to former investigations, we found lower production at a higher nutrient loading already at the trophic level of primary producers

Untersuchungen zum langjaehrigen Verlauf von Schwermetalldepositionen in ausgewaehlten schleswig-holsteinischen Salzmarschen auf der Basis von Radionuklidmessungen

Sediment cores from stratigraphically undisturbed North Frisian saltmarshes were dated using radiological methods ("2"1"0Pb-, "1"3"7Cs- and "1"4C-dating) and analyzed for heavy metals in the <20 #mu#m-particle size fraction using Total-Reflection X-Ray Fluorescence Spectrometry and Atomic Absorbtion Spectrometry. The investigations provide information about local background concentrations of the heavy metals and show temporal variations of heavy metal concentrations in the sediments, thus reflecting the history of industrialization. Concentrations of copper, zinc, cadmium, mercury and lead, in particular, have increased significantly in the sediments during the present century as a result of industrial emissions. Effects of anti-pollution measures and of diagenetic processes on heavy metal profiles are discussed. (orig.)An Bohrkernen aus stratigraphisch ungestoerten Sedimenten nordfriesischer Salzmarschen werden Sedimentdatierungen mit radiologischen Methoden ("2"1"0Pb-, "1"3"7Cs- und "1"4C-Datierung) und Schwermetalluntersuchungen an der <20 #mu#m-Fraktion mit Hilfe von Totalreflexions-Roentgenfluoreszenz-Analyse und Atom-Absorbtions-Spektrometrie durchgefuehrt. Die Untersuchungen geben Aufschluss ueber lokale geochemische Basiskonzentrationen der untersuchten Schwermetalle sowie ueber zeitliche Veraenderungen der Schwermetallkonzentrationen im Sediment, die weitgehend den Verlauf der Industrialisierung reflektieren. Insbesondere die Sedimentgehalte von Kupfer, Zink, Cadmium, Quecksilber und Blei steigen in unserem Jahrhundert infolge industrieller Schwermetallfreisetzungen deutlich an. Die Einfluesse emissionsmindernder Massnahmen und diagenetischer Prozesse auf die Schwermetallprofile werden diskutiert. (orig.)SIGLEAvailable from TIB Hannover: RA 3251(92/E/107) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman