Search results for "ocean"
showing 10 items of 2919 documents
Diet composition and biomass consumption of harbour seals in Telemark and Aust-Agder, Norwegian Skagerrak
2020
To explore ecosystem dynamics and functions it is vital to obtain knowledge on predator–prey relations. Harbour seals are piscivorous predators that can come into conflict with fisheries. Recently, as the Skagerrak and Kattegat population of harbour seals has increased, claims have emerged that seals are depleting coastal cod populations. The diet of harbour seals in Norwegian Skagerrak was investigated based on otolith identification from scats. The overall seal diet included 20 different fish species/groups. The most important prey (combined index Q i ) were haddock/pollack/saithe (32.7%), genus Trisopterus (Norway pout/poor cod/bib, 12.5%), plaice (12.4%) and herring (10.0%). Plaice also…
Large-scale distribution analysis of Antarctic echinoids using ecological niche modelling.
2012
Understanding the factors that determine the distribution of taxa at various spatial scales is a crucial challenge in the context of global climate change. This holds particularly true for polar marine biota that are composed of both highly adapted and vulnerable faunas. We analysed the distribution of 2 Antarctic echinoid species, Sterechinus antarcticus and S. neumayeri, at the scale of the entire Southern Ocean using 2 niche modelling procedures. The performance of distribution models was tested with regard to the known ecology of the species. The respective contributions of environmental parameters are discussed along with the putative roles played by biotic interactions and biogeograph…
Phytoplankton in Lake Tanganyika — vertical and horizontal distribution of in vivo fluorescence
1999
Determinations of chlorophyll a and in vivo fluorescence of photosynthetic pigments were used to study vertical and horizontal distribution of phytoplankton in Lake Tanganyika (East Africa). Blue excited fluorescence (IVFb) was an approximate predictor of chlorophyll a at different depths and locations. Green excited fluorescence (IVFg), which reflects phycoerythrin in cyanobacteria, explained chlorophyll a variation equally well, and in combination with IVFb the degree of explanation was improved to 87% (n = 90). Particularly during the shallow stratification in March–May, the maxima of chlorophyll a, IVFb and IVFg were located within the thermocline. Such distribution may have resulted fr…
Ocean Acidification and the Loss of Phenolic Substances in Marine Plants
2012
Rising atmospheric CO(2) often triggers the production of plant phenolics, including many that serve as herbivore deterrents, digestion reducers, antimicrobials, or ultraviolet sunscreens. Such responses are predicted by popular models of plant defense, especially resource availability models which link carbon availability to phenolic biosynthesis. CO(2) availability is also increasing in the oceans, where anthropogenic emissions cause ocean acidification, decreasing seawater pH and shifting the carbonate system towards further CO(2) enrichment. Such conditions tend to increase seagrass productivity but may also increase rates of grazing on these marine plants. Here we show that high CO(2) …
Ocean acidification impairs vermetid reef recruitment
2014
Vermetids form reefs in sub-tropical and warm-temperate waters that protect coasts from erosion, regulate sediment transport and accumulation, serve as carbon sinks and provide habitat for other species. The gastropods that form these reefs brood encapsulated larvae; they are threatened by rapid environmental changes since their ability to disperse is very limited. We used transplant experiments along a natural CO2 gradient to assess ocean acidification effects on the reef-building gastropod Dendropoma petraeum. We found that although D. petraeum were able to reproduce and brood at elevated levels of CO2, recruitment success was adversely affected. Long-term exposure to acidified conditions…
Seasonal cycle of benthic denitrification and DNRA in the aphotic coastal zone, northern Baltic Sea
2020
Current knowledge on the seasonality of benthic nitrate reduction pathways in the aphotic, density stratified coastal zone of the Baltic Sea is largely based on data from muddy sediments, neglecting the potential contribution of sandy sediments. To gain a more comprehensive understanding of seasonality in this part of the Baltic Sea coast, we measured rates of benthic denitrification, anammox and dissimilatory nitrate reduction to ammonium (DNRA) monthly in the ice-free period of 2016 in both sandy and muddy aphotic sediments, northwestern Gulf of Finland. No anammox was observed. The seasonal cycle of denitrification in both sediment types was related to the hydrography-driven development …
Halophila stipulacea descriptors in the native area (Red Sea): A baseline for future comparisons with native and non-native populations
2018
Abstract Halophila stipulacea is a small tropical seagrass species native to the Red Sea. Due to its invasive character, there is growing interest in understanding its ability to thrive in a broad range of ecological niches. We studied temporal (February 2014 and July 2014), depth (5, 9, 18 m) and spatial (NB and SB) related dynamics of H. stipulacea meadows in the northern Gulf of Aqaba. We evaluated changes in density, morphometry, biomass, and biochemical parameters alongside the reproductive effort. In both sites, maximal growth and vegetative performance occurred in the summer with a marked increase of 35% in shoot density and 18% in biomass; PAR reduction with season and depth induced…
On the Role of Perception: Understanding Stakeholders’ Collaboration in Natural Resources Management through the Evolutionary Theory of Innovation
2021
Natural resources management deals with highly complex socioecological systems. This complexity raises a conundrum, since wide-ranging knowledge from different sources and types is needed, but at the same time none of these types of knowledge is able by itself to provide the basis for a viable productive system, and mismatches between the two of them are common. Therefore, a growing body of literature has examined the integration of different types of knowledge in fisheries management. In this paper, we aim to contribute to this ongoing debate by integrating the evolutionary theory of innovation—and specifically the concept of proximity—and the theory of perception. We set up a theoretical …
Seasonal shifts between autochthonous and allochthonous carbon contributions to zooplankton diets in a subarctic lake
2011
We addressed the extent to which autochthonous and allochthonous carbon sources contribute to zooplankton diet throughout the year in oligotrophic subarctic Lake Saanajarvi. Optical measures of dissolved organic matter (DOM) indicated high water discharge and associated terrestrial DOM during winter and low inputs in summer. Bulk particulate organic matter (POM) showed d13C values consistent with allochthonous inputs of DOM. The most positive POM d13C values (227%) occurred during winter, when heterotrophic bacteria and nanoflagellates peaked in abundance; the isotopically lighter autotrophic phytoplankton shifted the POM d13 Ct o229% in summer. The d13C values of zooplankton were up to 4% …
Estimating cod egg developmental stage based on DNA concentration
2017
Abstract Pelagic egg surveys are commonly used to map Atlantic cod spawning areas in the northeastern Atlantic. However, a sampling location may not necessarily indicate a spawning location, because more developed eggs may have drifted long distances in coastal currents. Newly spawned eggs have only a few embryonic cells, whereas eggs in later developmental stages have progressively larger numbers of cells and hence greater amounts of DNA. The progression through developmental stages largely depends on temperature, which influences cell division and growth. Preservation of the eggs for later analysis presents logistical dilemmas. Preservation in ethanol is suitable for DNA extraction but ob…