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  • 1
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    Effects of ocean acidification on the calcification of otoliths of larval Atlantic cod Gadus morhua (2013)
    Inter Research
    In:  Marine Ecology Progress Series, 477 . pp. 251-258.
    Details
    Publication Date: 2018-06-25
    Description: The growth and development of the aragonitic CaCO3 otoliths of teleost fish could be vulnerable to processes resulting from ocean acidification. The potential effects of an increase in atmospheric CO2 on the calcification of the otoliths were investigated by rearing Atlantic cod Gadus morhua L. larvae in 3 pCO2 concentrations—control (370 µatm), medium (1800 µatm) and high (4200 µatm)—from March to May 2010. Increased otolith growth was observed in 7 to 46 d post hatch (dph) cod larvae at elevated pCO2 concentrations. The sagittae and lapilli were usually largest in the high pCO2 treatment followed by the medium and control treatments. The greatest difference in mean otolith surface area (normalized to fish length) was for sagittae at 11 dph, with medium and high treatments being 46 and 43% larger than the control group, respectively. There was no significant pCO2 effect on the shape of the otoliths nor were there any trends in the fluctuating asymmetry, defined as the difference between the right and left sides, in relation to the increase in otolith growth from elevated pCO2.
    Type: Article , PeerReviewed , info:eu-repo/semantics/article
    Format: text
    DOI: 10.3354/meps10146
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 2
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    Seasonal and spatial variations in the RNA:DNA ratio and its relation to growth in sub-Arctic scallops (2010)
    Inter Research
    In:  Marine Ecology Progress Series, 407 . pp. 87-98.
    Details
    Publication Date: 2018-06-19
    Description: We examined the RNA and DNA concentration of field-caught scallops Chlamys islandica, maintained in suspended cultures at 15 and 30 m depth, and scallops from a wild population at 50 to 60 m in Kobbefjord, southwest Greenland. General relations between RNA and DNA concentrations and individual shell height were established, and we found that the RNA:DNA ratio (RD) worked well as a standardisation of the RNA concentration independent of size and sex. During an experimental period of 14 mo, we observed a pronounced seasonal pattern in RD and mass growth, and differences between depths. Even though the period with high levels of RD reflected the growth season relatively well, RD was a poor predictor of individual mass growth rates of C. islandica. However, we found a non-linear response in RD to increased food concentrations resulting in RD being up- and down-regulated at the beginning and end of the productive summer season, respectively. These results indicate that short-term dynamics in the actual mass growth rate might be controlled through regulation of ribosome activity rather than ribosome number (RNA concentration). This adaption would allow scallops to up-regulate protein synthesis more rapidly, thereby ensuring efficient utilisation of the intense peaks in food availability in coastal areas in the Arctic. Therefore, we suggest that RD in C. islandica reflects the growth potential rather than the actual growth rate. Still, the amount of unexplained variance in RD is considerable and not independent over time, suggesting the existence of unresolved mechanisms or relationships.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3354/meps08540
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    Comparative nutritional condition of larval dab Limanda limanda and lesser sandeel Ammodytes marinus in a highly variable environment (2007)
    Inter Research
    In:  Marine Ecology Progress Series, 334 . pp. 205-212.
    Details
    Publication Date: 2019-09-23
    Description: We investigated the nutritional condition of larval fishes caught in daily ichthyoplankton hauls in the ‘Helgoland Roads’ (54°11.18’N and 07°54.00’E) from February to June 2004. We concentrated on larvae of dab Limanda limanda and lesser sandeel Ammodytes marinus in order to compare early life stages of iteroparous and nearly semelparous fish. We analysed length, weight and RNA:DNA ratios as a proxy for condition of the larvae. The relationship between larval nutritional condition and larval size provided an indication of condition-selective mortality due to a loss of larvae in poor condition from the larger size-classes. For the sandeel, larvae in good condition were present in all size-classes, whereas for the dab maximum larval condition increased with increasing size. Variability in both standard length and condition was high in the 2 species during their planktonic stage. Both species showed good nutritional condition in the early to mid portion of the recruitment period and declines in condition in late April. This was more pronounced in larval dab, which showed a higher dependency on feeding conditions than larval sandeel. Together, these findings indicate a more conservative strategy of early life stages of the nearly semelparous sandeel compared with the iteroparous dab.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3354/meps334205
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Exploring Ocean Change: BIOACID - Biological Impacts of Ocean Acidification (2017)
    GEOMAR
    In:  GEOMAR, Kiel, Germany, 23 pp.
    Details
    Publication Date: 2019-09-23
    Type: Report , NonPeerReviewed
    Format: text
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    OceanRep: Report - other report
  • 5
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    Dem Ozeanwandel auf der Spur: BIOACID - Biologische Auswirkungen von Ozeanversauerung (2017)
    GEOMAR
    In:  GEOMAR, Kiel, Germany, 23 pp.
    Details
    Publication Date: 2019-09-23
    Type: Report , NonPeerReviewed
    Format: text
    Location Call Number Limitation Availability
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    OceanRep: Report - other report
  • 6
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    Improvements in the fluorimetric determination of the RNA and DNA content of individual marine fish larvae (1993)
    Inter Research
    In:  Marine Ecology Progress Series, 100 . pp. 177-183.
    Details
    Publication Date: 2018-03-07
    Description: The RNA/DNA ratio is a useful indicator of the nutritional condition of fish larvae. The presented analytical procedure is an improvement of Clemmesen's (Meeresforschung 32: 134-143, 1988) methodology which involves purification of fish larvae tissue homogenates and subsequent fluorescence-photometric measurements using specific nucleic acid dyes. The modifications concern the homogenization and nucleic acid extraction procedures. A 'shaking mill' was compared to a potter Elvehjem microhomogenizer and a reduction in the washing and purification steps was achieved. Treatment of samples with ribonuclease A and subsequent fluorescence measurement using ethidium bromide was given preference compared to the DNA-bisbenzimidazole determinations due to problems arising from high self-fluorescence of the samples and the influence of 'quenching' substances disturbing the DNA-bisbenzmidazole determinations. Different RNase concentrations and their influences on RNA and DNA were checked. Recovery rates of standard RNA and DNA 'spikes' were determined. Fish larvae samples were analysed with the previous and the improved modified procedure and a correction factor to compare results measured with the 2 procedures was calculated. With the presented method the physiological condition of individual larvae and the amount of variability can be determined.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 7
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    Temperature effects on growth and nucleic acids in laboratory-reared larval coregonid fish (2003)
    Inter Research
    In:  Marine Ecology Progress Series, 259 . pp. 285-293.
    Details
    Publication Date: 2018-05-28
    Description: Somatic growth and nucleic acid content were studied in North Sea houting Coregonus oxyrhinchus larvae fed exclusively on dry diets at 2 temperatures (8.4 and 17.5°C) during a 32 d rearing experiment. The higher temperature enhanced growth significantly. Mean dry weights at the end of the experiment were 3.6 mg (SD = 1.07, range 1.4 to 5.7 mg) and 31.5 mg (SD = 21.9, range 3.6 to 96.0 mg), and mean standard lengths were 17.7 ± mm (SD = 1.6, range 11.8 to 19.6 mm) and 25.5 mm (SD = 4.2, range 17.0 to 35 mm), respectively. Significant responses to temperature were also found in the nucleic acids. However, these differences were not as remarkable and gave indications that differences in protein growth between treatments was based on protein biosynthesis being driven by the activity of the ribosomes, rather than their number. The use of the degree-day approach to normalize the data clearly showed the temperature-dependence of somatic growth. Only small differences in growth and nucleic acid content were observed in the comparable range of the first 280 degree-days in fed fish. In non-fed fish, the starving potential was very similar (approx. 350 degree-days). Shifts in growth pattern from predominantly hyperplasia to predominantly hypertrophy were detected, with ongoing growth at both temperatures.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3354/meps259285
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 8
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    Invading Mnemiopsis leidyi as a potential threat to Baltic fish (2007)
    Inter Research
    In:  Marine Ecology Progress Series, 349 . pp. 303-306.
    Details
    Publication Date: 2018-06-01
    Description: The occurrence of the ctenophore Mnemiopsis leidyi as a new invasive species in the Baltic Sea and the potential consequences for fish stock recruitment was investigated in spring 2007. The study focused on the Bornholm Basin, which serves as the major spawning ground for cod and sprat, the commercially most important fish stocks in the Baltic. The distribution pattern of M. leidyi revealed a substantial overlap with cod eggs. The observed predation of M. leidyi on eggs has the potential to alter the recruitment success of cod, which is the top predator in the system and, thus, to change the Baltic food-web structure.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3354/meps07283
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Depth-dependent nutritional condition of sprat Sprattus sprattus larvae in the central Bornholm Basin, Baltic Sea (2007)
    Inter Research
    In:  Marine Ecology Progress Series, 341 . pp. 217-228.
    Details
    Publication Date: 2018-06-01
    Description: Bimodal depth distribution patterns observed for sprat Sprattus sprattus larvae in previous field studies conducted in the deep basins of the Baltic Sea have led researchers to hypothesise that larval sprat condition was depth-dependent. We examined this hypothesis by measuring morphological, biochemical and otolith-based proxies for nutritional condition in sprat larvae collected in discrete 5 m depth intervals from the surface to the bottom in the central Bornholm Basin. Similar to earlier studies, larval sprat were most abundant in 2 depth strata (0 to 10 and 65 to 75 m). Their nutritional condition in surface and deep waters was not uniformly expressed by the different indices. For example, sprat larvae from 0 to 10 m could not be distinguished from conspecifics caught at 65 to 75 m by a long-latency condition proxy (otolith-based growth rates). Similarly, a medium-latency proxy (RNA:DNA) did not suggest differences in condition between the depths. However, short-latency proxies (protein:standard length and DNA:dry weight) supported the depth-dependent condition hypothesis. The lack of correspondence and pitfalls associated with the use and interpretation of multiple condition indices (e.g. the influences of temperature and body size) are discussed and recommendations to strengthen these various metrics are provided.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3354/meps341217
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Lipids as a proxy for larval starvation and feeding condition in small pelagic fish: a field approach on match-mismatch effects on Baltic sprat (2015)
    Inter Research
    In:  Marine Ecology Progress Series, 531 . pp. 277-292.
    Details
    Publication Date: 2020-07-03
    Description: Sprat Sprattus sprattus larvae were used as model organisms to evaluate whether larval lipids reflect in situ feeding conditions and can thus identify match-mismatch situations. In detail, we determined larval lipid content, growth rates based on RNA:DNA ratios, and fatty acid (FA) composition during the spawning season in the Central Baltic Sea, and evaluated these in light of feeding, mortality and recruitment (which were determined in parallel within the project ‘GLOBEC Germany’). Based on the opposing trend of RNA:DNA and lipid content, as well as on previous observations, we hypothesized that lipid content and current feeding conditions are largely uncoupled in the early life stages of sprat due to reduced lipid anabolism. However, lipids still provide information in several ways: (1) segmented generalised linear models proved to be a suitable tool for identifying phases of lipid catabolism during development, with the slope reflecting size-specific environmental starvation pressure. This method detected a previously identified mismatch situation with suitable prey in the early spawning season, which increased mortality of larger larvae. (2) Estimated starvation resistance, a proxy that accounts for temperature- and size-dependent metabolism, reflected the likelihood of near future starvation of individual larvae. (3) Principal component analyses on FAs identified monthly differences in diet composition. Biomarkers indicated a dinoflagellate and/or microbial loop based carbon flux to the larvae. (4) Regression analyses revealed lower docosahexaenoic acid (DHA) levels in spring, but no obvious effect on growth. Food quality was generally high, and its impact on larval survival was less evident than that of prey size suitability.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.3354/meps11292
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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