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Search: authors:"Ulf Båmstedt"

14 papers found.
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An indoor pelagic mesocosm facility to simulate multiple water-column characteristics

Mesocosms are important research tools in aquatic ecology because they close the gap between laboratory studies at the individual or lower organization level and field studies at the population and ecosystem level. However, most mesocosm studies regarding the pelagic environment do not consider the effects of physical factors like water-column stratification, turbulence and...

A cost-precision model for marine environmental monitoring, based on time-integrated averages

Ongoing marine monitoring programs are seldom designed to detect changes in the environment between different years, mainly due to the high number of samples required for a sufficient statistical precision. We here show that pooling over time (time integration) of seasonal measurements provides an efficient method of reducing variability, thereby improving the precision and power...

Evidence of Diel Vertical Migration in Mnemiopsis leidyi

The vertical distribution and migration of plankton organisms may have a large impact on their horizontal dispersal and distribution, and consequently on trophic interactions. In this study we used video-net profiling to describe the fine scale vertical distribution of Mnemiopsis leidyi in the Kattegat and Baltic Proper. Potential diel vertical migration was also investigated by...

Seasonal abundance and vertical distribution of siphonophores in western Norwegian fjords

Seasonal abundance of siphonophores in Korsfjord and Fanafjord was studied by net sampling. Nanomia cara, Lensia conoidea and Dimophyes arctica were dominant species present throughout the year. Abundance of N. cara colonies peaked in late May and early June. Low numbers of relatively large colonies and high numbers of siphonulae were observed during winter. Dimophyes arctica and...

Seasonal variation in wax ester concentration and gut content in a Baltic Sea copepod [Limnocalanus macrurus (Sars 1863)]

Limnocalanus macrurus from Bothnian Bay in the northern part of the Baltic Sea was studied during the ice-free period (April–December) in order to understand its life history and feeding biology. Our data on the population dynamics indicated that reproduction occurred during the ice-covered period, during which lipid storage was reduced to a minimum. From spring to late summer...

Strain-related physiological and behavioral effects of Skeletonema marinoi on three common planktonic copepods

Three strains of the chain-forming diatom Skeletonema marinoi, differing in their production of polyunsaturated aldehydes (PUA) and nutritional food components, were used in experiments on feeding, egg production, hatching success, pellet production, and behavior of three common planktonic copepods: Acartia tonsa, Pseudocalanus elongatus, and Temora longicornis. The three...

In situ behaviour and acoustic properties of the deep living jellyfish Periphylla periphylla

The importance of jellyfish in marine systems is increasingly being recognized, and in some ecosystems, jellyfish may now be considered the top predator. We studied the behaviour of individuals of the deep-water schypozoan Periphylla periphylla in one such location, the Lurefjord, Norway. The study was performed using a combination of submersible acoustics (38 kHz), video and net...

PCR–DHPLC assay for the identification of predator–prey interactions

Denaturing high-performance liquid chromatography (DHPLC) is a relatively new method for separating amplicons in a mixture, and was recently developed for parasite detection in the blue crab Callinectes sapidus. That assay used a peptide nucleic acid (PNA) PCR hybridization blocking probe (PNA–PCR–DHPLC) to decrease the generic PCR bias of dominant templates (the host) in the...

Future Climate Scenarios for a Coastal Productive Planktonic Food Web Resulting in Microplankton Phenology Changes and Decreased Trophic Transfer Efficiency

We studied the effects of future climate change scenarios on plankton communities of a Norwegian fjord using a mesocosm approach. After the spring bloom, natural plankton were enclosed and treated in duplicates with inorganic nutrients elevated to pre-bloom conditions (N, P, Si; eutrophication), lowering of 0.4 pH units (acidification), and rising 3°C temperature (warming). All...

Variation in hatching success and egg production of Eurytemora affinis (Calanoida, Copepoda) from the Gulf of Bothnia, Baltic Sea, in relation to abundance and clonal differences of diatoms

We monitored the hatching frequencies and clutch sizes of Eurytemora affinis, and environmental variables in the Gulf of Bothnia, between May and October 2003. We tested the hypothesis that the hatching frequency of the copepod would be negatively affected during time periods with high diatom concentrations. Results from two stations showed significant differences between the...

Swimming and feeding in Periphylla periphylla (Scyphozoa, Coronatae)

Some western Norwegian fjords host extraordinarily abundant and persistent populations of the mesopelagic, coronate scyphomedusa, Periphylla periphylla. In these environments, from late autumn to spring, the medusae undertake regular diel vertical migrations into surface waters. From unique observations obtained with a remotely operated vehicle (ROV), including observations made...

An evaluation of acoustic and video methods to estimate the abundance and vertical distribution of jellyfish

Four non-invasive methods (three acoustic and one video) were compared to estimate the abundance and vertical distribution of scyphomedusae, using the locally abundant coronate species Periphylla periphylla in Lurefjorden, north of Bergen, Norway, as the test organism. The acoustic methods included single-target quantification by, respectively, a hull-mounted 38 kHz split-beam...

Food regulation of growth and maturation in a natural population of Aurelia aurita (L.)

Growth and maturity development of the moon jellyfish. Aurelia aurita, were recorded in Vågsbøpollen, a small and semi-enclosed bay on the Norwegian west coast, and compared to those of medusae transferred to excess food and starving conditions, respectively. Mesozooplankton were extremely scarce in Vågsbøpollen. The abundance and biomass of the medusae in the poll were higher...

Causes for mass occurrences of the jellyfish Periphylla periphylla: a hypothesis that involves optically conditioned retention

The mesopelagic coronate medusa Periphylla periphylla has been very abundant (20–320 individuals m−2), with as many as 2.5 individuals m−3, for more than a decade in certain Norwegian fjords. These abundances are two to three orders of magnitude higher than reported from open ocean environments. Comparisons of the size, density and behavior of this jellyfish in three fjords...