Wyniki wyszukiwania - BazTech

Ograniczanie wyników

Znaleziono wyników: 2

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: otoliths

Sortuj według:

Ogranicz wyniki do:

Annual, seasonal and spatial differences in the growth rate of Baltic cod larvae and early juveniles in relation to zooplankton biomass fluctuations in 2006-2014

Spich Katarzyna, Fey Dariusz Piotr

Oceanological and Hydrobiological Studies

2023

Vol. 52, No. 4

399--419

It is an acknowledged theory that a faster growth rate, determined by various environmental drivers, may boost the survival of larval and juvenile fish. In this study we examined the differences in the growth rate of larval and juvenile cod (age 2 – 136 d; SL: 4.1 – 39.2 mm) between the years 2006 and 2014, sub-areas of the Baltic Sea (Bornholm Basin, BB; Słupsk Furrow, SF; Gdansk Basin, GB), and seasons (spring and summer). The average growth rate for all specimens was 0.25 mm/d, with significantly lower values between 2012 and 2014 than between 2006 and 2011. A reduction in zooplankton biomass, especially the large zooplankton fraction, was observed after the 2006–2008 period, which was related to the prevailing temperature conditions in the surface layers. The reduction in zooplankton biomass was accompanied by changes in the structure of zooplankton: less T. longicornis, C. hamatus, and Pseudocalanus spp., and more Acartia spp. The results suggest that the inter-annual differences observed in zooplankton biomass and structure are likely responsible for the observed reduction in the growth rate of cod larvae between 2012 and 2014 compared to the years between 2006 and 2011. The growth rate reduction could be one of the reasons for the decline in the recruitment of eastern Baltic cod between the years 2013 and 2015, after the high recruitment years of the period 2011-2012.

Reconstruction of the unusual Middle Miocene (Badenian) palaeoenvironment of the Carpathian Foredeep (Lomnice/Tišnov denudational relict, Czech Republic)

Holcova K., Brzobohatý R., Kopeckáa J., Nehyba S.

Geological Quarterly

2015

Vol. 59, No. 4

654--678

Multiproxy sedimentological, gamma-spectrometric, foraminiferal, calcareous nannoplankton, and otolith data were used for the reconstruction of the Badenian (Middle Miocene) history of the Moravian part of the Carpathian Foredeep. The study material originated from the new borehole LOM-1, which drilled >20 metres of monotonous clayey siltstones with exceptionally rich and well-preserved microfossil assemblages. Distal parts of the Carpathian Foredeep (a forebulge depozone) are exposed in this succession. Generally, a quiet environment of outer shelf to upper bathyal of monotonous clayey silts was interpreted, which is typical for the proximal parts of a peripheral foreland basin. The section studied can be subdivided into six intervals, confirming the cyclical character of Middle Miocene sedimentation in the Central Paratethys. Interannual oscillations of nutrient content, temperature and/or salinity are interpreted based on the oscillations of geochemical as well as palaeobiological data. The turnover connected with the initiation of the Middle Miocene Climatic Transition is recorded above the LO (last occurrence) of Helicosphaera waltrans in agreement with previous observations in the Carpathian Foredeep. The changes include cooling, a decrease in nutrients, a probable increase of the salinity of surface water, and increase of seasonality. Seasonality was manifested by an alternation of mixed and stratified water columns with a seasonal input of nutrients. Concerning nutrients, sources of seasonal riverine input or seasonal upwelling are both possible.