| 1. |
- Aarestrup, K., et al.
(författare)
-
Survival and progression rates of anadromous brown trout kelts Salmo trutta during downstream migration in freshwater and at sea
- 2015
-
Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 535, s. 185-195
-
Tidskriftsartikel (refereegranskat)abstract
- The marine migration of post-spawning anadromous fish remains poorly understood. The present study examined survival and progression rates of anadromous brown trout Salmo trutta L. after spawning (kelts) during downriver, fjord, and sea migration. Kelts (n = 49) were captured in the Danish River Gudenaa, tagged with acoustic transmitters and subsequently recorded by automatic receivers. Kelts spent on average 25 d moving down the 45 km river and through the brackish fjord. The fish entered the Kattegat Sea between 14 April and 30 May. Eighteen of the 49 kelts disappeared in the river and fjord during outward migration, likely due to mortality. Survival was not significantly related to gill Na+/K+-ATPase activity, suggesting that physiological adaptation to saltwater may be less critical for adults compared to juveniles (smolts). Of the 31 fish that entered the Kattegat Sea, 45% survived and returned to the fjord. The duration of the entire marine migration, from leaving to entering the river, was on average 163 d. The fish returned from the Kattegat Sea to the fjord between 22 July and 21 October. Upon return, the fish spent 1-90 d passing through Randers Fjord, with most individuals completing the reach within 4 d, suggesting that the kelts spent limited time foraging after returning to the fjord. The total survival during the entire marine migration, including the fjord, was a minimum of 29%. Our study provides data that are important for management of anadromous brown trout, and the high survival highlights that kelts may represent a valuable resource for both population reproduction and recreational fisheries.
|
|
| 2. |
- Aldvén, David, 1986, et al.
(författare)
-
Migration speed, routes, and mortality rates of anadromous brown trout Salmo trutta during outward migration through a complex coastal habitat
- 2015
-
Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 541, s. 151-163
-
Tidskriftsartikel (refereegranskat)abstract
- Little is known about migratory routes and habitat use of anadromous brown trout Salmo trutta at sea. We therefore conducted a 2 yr study (2011-2012) on sea trout in the River Himlean system (a river, an estuary, and a coastal sea environment) in western Sweden. The main objectives were to investigate migration speed, migration routes, and mortality both for adult brown trout returning to the sea (kelts) and smolts (generally 2 yr old trout migrating to the sea for the first time). Brown trout were captured and tagged with hydro-acoustic transmitters, after which they were released and monitored during their initial migration. Migration was primarily nocturnal in the river and estuary, whereas no tendency for nocturnal migration was observed along the coast. Migration speed tended to decrease as individuals progressed from the river through the estuary and along the coast, and we found no differences in absolute migration speed between kelts and smolts. Smolts and kelts showed similar mortality. Mortality during the initial part of the migration ranged between 5 and 51% and was significantly higher in 2011, for both smolts and kelts. Our study is the first to compare migratory patterns and mortality rates between sea trout kelts and smolts during the transition from freshwater into an open coastal system.
|
|
| 3. |
- Attard, Karl M., et al.
(författare)
-
Benthic oxygen exchange in a live coralline algal bed and an adjacent sandy habitat : an eddy covariance study
- 2015
-
Ingår i: Marine Ecology Progress Series. - : Inter-Research. - 0171-8630 .- 1616-1599. ; 535, s. 99-115
-
Tidskriftsartikel (refereegranskat)abstract
- Coralline algal (maerl) beds are widespread, slow-growing, structurally complex perennial habitats that support high biodiversity, yet are significantly understudied compared to seagrass beds or kelp forests. We present the first eddy covariance (EC) study on a live maerl bed, assessing the community benthic gross primary productivity (GPP), respiration (R), and net ecosystem metabolism (NEM) derived from diel EC time series collected during 5 seasonal measurement campaigns in temperate Loch Sween, Scotland. Measurements were also carried out at an adjacent (similar to 20 m distant) permeable sandy habitat. The O-2 exchange rate was highly dynamic, driven by light availability and the ambient tidally-driven flow velocity. Linear relationships between the EC O-2 fluxes and available light indicate that the benthic phototrophic communities were light limited. Compensation irradiance (E-c) varied seasonally and was typically similar to 1.8-fold lower at the maerl bed compared to the sand. Substantial GPP was evident at both sites; however, the maerl bed and the sand habitat were net heterotrophic during each sampling campaign. Additional inputs of similar to 4 and similar to 7 mol m(-2) yr(-1) of carbon at the maerl bed and sand site, respectively, were required to sustain the benthic O-2 demand. Thus, the 2 benthic habitats efficiently entrap organic carbon and are sinks of organic material in the coastal zone. Parallel deployment of 0.1 m(2) benthic chambers during nighttime revealed O-2 uptake rates that varied by up to similar to 8-fold between replicate chambers (from -0.4 to -3.0 mmol O-2 m(-2) h(-1); n = 4). However, despite extensive O-2 flux variability on meter horizontal scales, mean rates of O-2 uptake as resolved in parallel by chambers and EC were typically within 20% of one another.
|
|
| 4. |
- Bartolino, Valerio
(författare)
-
Role of prey abundance and geographical variables in a demersal top predator's feeding habits (Merluccius merluccius)
- 2015
-
Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 541, s. 165-177
-
Tidskriftsartikel (refereegranskat)abstract
- Demersal predators can take advantage of a large pool of potential prey including benthic, demersal and pelagic species; therefore disentangling the variables that influence their diet is of key relevance for food web ecologists. To this aim, we analysed a large dataset of the stomach contents of European hake Merluccius merluccius, a top predator in the demersal food web of the Cantabrian Sea. We combined 2 modelling approaches: a zero-truncated generalised additive model targeting fullness variability, and a multinomial model on the probability of consumption for each prey. Predator size, geographical variables (i.e. longitude and depth), and abundance of prey were considered as independent variables, and had significant effects on predator stomach fullness. We also documented a positive effect of continental shelf width on predator stomach fullness. The hake's main prey, blue whiting Micromesistius poutassou, had the strongest effect on predator feeding success. However, in the absence of this prey species, consumption of all other prey items increased. Consumption was highly influenced by prey abundance, but predator density dependence was only evident in instances of cannibalism. Both the full/empty ratio and stomach fullness decreased during ontogeny, and a change from low-energy demersal to high-energy pelagic prey was documented, matching the onset of maturity. While the abundance of prey significantly affected feeding success, a large diet breadth rather than prey surrogates seemed to act as an effective buffer, ensuring feeding at low abundance of specific prey.
|
|
| 5. |
- Berg, Florian, et al.
(författare)
-
Genetic origin and salinity history influence the reproductive success of Atlantic herring
- 2019
-
Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 617, s. 81-94
-
Tidskriftsartikel (refereegranskat)abstract
- Atlantic herring populations inhabit environments ranging in salinity from fully marine to nearly freshwater, but their relative reproductive success in these respective environments remains unclear. We conducted factorial crossing experiments using parents from 3 wild populations associated with different salinity environments: the Baltic Sea (similar to 6 psu), an inland brackish lake in Norway (Landvikvannet, similar to 16 psu), and the Atlantic (similar to 30 to 35 psu). Further experiments used crosses within and between Atlantic purebreds and Atlantic/Baltic hybrids reared until first maturity at 3 yr of age. Crossing experiments were conducted at 6, 16 and 35 psu. Fertilization and hatching rates were estimated, and egg sizes were measured. Fertilization rates were highest at 16 psu for all combinations. The paternal genetic and salinity origin influenced fertilization rates at 6 and 35 psu, indicating a genetic adaptation to their original environment. Fertilization rates for males originating from 16 psu were low at 35 psu. Atlantic/Baltic hybrids had lower fertilization rates than Atlantic purebreds at 35 psu. Hatching rates were not influenced by any parental factors or salinity. Maternal effects and salinity influenced egg size. Atlantic females had significantly larger eggs than the Atlantic/Baltic hybrid females. For all genetic groups, egg size decreased with increasing salinity at incubation mainly due to osmotic effects. The observed lower fertilization success at salinities other than those of the parental fish habitat would have evolutionary consequences when herring colonize new habitats with different salinities or if interbreeding occurred between populations originating from different salinity habitats.
|
|
| 6. |
- Blomqvist, Sven, et al.
(författare)
-
Long overdue improvement of box corer sampling
- 2015
-
Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 538, s. 13-21
-
Tidskriftsartikel (refereegranskat)abstract
- An improved, large double-jawed box corer, intended primarily for sampling of soft sediments on continental margins and in large lakes, is described. The device performs reliably when entering the sediment and enclosing the sample, during withdrawal and hoisting on board the ship and also when detaching the collected sediment sample. It offers the following advantages: (1) robust design, (2) minimally impeded flow of water through the box chamber during lowering and (3) an efficient closure mechanism. It is furnished with a supporting stand, a transparent liner and an accessory anti-slosh baffle for insertion in the liner as the corer is set down on the ship's deck. In situ video records and turbidity measurements from field trials, as well as visual inspection of the core and supernatant water after retrieval, show that the device collects minimally disturbed sediment when properly and carefully operated. This contrasts with the bulky United States Naval Electronics Laboratory (USNEL) Spade Corer in which water flow through the box chamber during lowering is impeded, causing a bow-wave ahead of the corer that displaces surficial sediment. In addition, the USNEL's single-spade closing mechanism deforms the sediment sample severely and can even cause loss of sediment. Our new box corer performs much better, making it suitable for quantitative benthic sampling.
|
|
| 7. |
- Brault, Emily K., et al.
(författare)
-
Trophic position and foraging ecology of Ross, Weddell, and crabeater seals revealed by compound-specific isotope analysis
- 2019
-
Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 611, s. 1-18
-
Tidskriftsartikel (refereegranskat)abstract
- © The authors 2019. Ross seals Ommatophoca rossii are one of the least studied marine mammals, with little known about their foraging ecology. Research to date using bulk stable isotope analysis suggests that Ross seals have a trophic position intermediate between that of Weddell Leptonychotes weddellii and crabeater Lobodon carcinophaga seals. However, consumer bulk stable isotope values not only reflect trophic dynamics, but also variations in baseline isotope values, which can be substantial. We used compound-specific isotope analysis of amino acids (CSI-AA) to separate isotopic effects of a shifting baseline versus trophic structure on the foraging ecology of these ecologically important Antarctic pinnipeds. We found that Ross seals forage in an open ocean food web, while crabeater and Weddell seals forage within similar food webs closer to shore. However, isotopic evidence suggests that crabeater seals are likely following sea ice, while Weddell seals target productive areas of the continental shelf of West Antarctica. Our CSI-AA data indicate that Ross seals have a high trophic position equivalent to that of Weddell seals, contrary to prior conclusions from nitrogen isotope results on bulk tissues. CSI-AA indicates that crabeater seals are at a trophic position lower than that of Ross and Weddell seals, consistent with a krill-dominated diet. Our results redefine the view of the trophic dynamics and foraging ecology of the Ross seal, and also highlight the importance of quantifying baseline isotope variations in foraging studies.
|
|
| 8. |
- Brosset, Pablo, et al.
(författare)
-
Linking small pelagic dietary shifts with ecosystem changes in the Gulf of Lions
- 2016
-
Ingår i: Marine Ecology Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 554, s. 157-171
-
Tidskriftsartikel (refereegranskat)abstract
- Since 2008, a severe decrease in size and body condition together with a demographic truncation has been observed in the sardine (secondarily in anchovy) population of the Gulf of Lions (NW Mediterranean Sea). In parallel, sprat biomass, which was negligible before, has increased tenfold. All of these changes have strongly affected the regional fisheries. Using trophic and isotopic data from contrasting periods of low versus high growth and condition, we investigated potential changes in diet and interspecific feeding interactions through time. Evidence of resource partitioning was found between sprat and both anchovy and sardine in 2004 and 2005. Since 2010, the isotopic niches of the 3 species have tended to overlap, suggesting higher risk of competition for food resources. Moreover, the wider trophic niche of sprat indicates higher variability in individual diets. Anchovy and sardine diet varied through time, with a high proportion of large copepods or cladocerans in periods of high growth and condition (1994 and 2007, respectively) versus a dominance of small copepods in the present (2011-2012). Furthermore, an important reduction in prey diversity was also identified in the diet of both anchovy and sardine during the most recent period. Our results support the hypothesis that changes in small pelagic fish growth, size and body condition and ultimately biomass could be due to bottom-up control characterized by changes in food availability and increasing potential trophic competition.
|
|
| 9. |
- Burdett, Heidi L., et al.
(författare)
-
Community-level sensitivity of a calcifying ecosystem to acute in situ CO2 enrichment
- 2018
-
Ingår i: Marine Ecology Progress Series. - : Inter-Research. - 0171-8630 .- 1616-1599. ; 587, s. 73-80
-
Tidskriftsartikel (refereegranskat)abstract
- The rate of change in ocean carbonate chemistry is a vital determinant in the magnitude of effects observed. Benthic marine ecosystems are facing an increasing risk of acute CO2 exposure that may be natural or anthropogenically derived (e.g. engineering and industrial activities). However, our understanding of how acute CO2 events impact marine life is restricted to individual organisms, with little understanding for how this manifests at the community level. Here, we investigated in situ the effect of acute CO2 enrichment on the coralline algal ecosystem - a globally ubiquitous, ecologically and economically important habitat, but one which is likely to be sensitive to CO2 enrichment due to its highly calcified reef-like structures engineered by coralline algae. Most notably, we observed a rapid community-level shift to favour net dissolution rather than net calcification. Smaller changes from net respiration to net photosynthesis were also observed. There was no effect on the net flux of DMS/DMSP (algal secondary metabolites), nor on the nutrients nitrate and phosphate. Following return to ambient CO2 levels, only a partial recovery was seen within the monitoring timeframe. This study highlights the sensitivity of biogenic carbonate marine communities to acute CO2 enrichment and raises concerns over the capacity for the system to 'bounce back' if subjected to repeated acute high-CO2 events.
|
|
| 10. |
- Båmstedt, Ulf, 1946-, et al.
(författare)
-
Mixing depth and allochthonous dissolved organic carbon: controlling factors of coastal trophic balance
- 2016
-
Ingår i: Marine Ecology Progress Series. - Oldendorf/Luhe : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 561, s. 17-29
-
Tidskriftsartikel (refereegranskat)abstract
- ABSTRACT: The interacting effects of different mixing depths and increased allochthonous dissolved organic carbon (DOC) on the ratio of heterotrophic to autotrophic production (i.e. trophic balance) was evaluated in a mesocosm study with a stratified water column. An autumn plankton community from the northern Bothnian Sea showed significantly decreased phytoplankton production and somewhat increased bacterial production with added DOC. In addition, increased mixing depth further reduced phytoplankton production. With a deep pycnocline and added DOC, the system became net-heterotrophic, with an average bacteria-to-phytoplankton production ratio of 1.24. With a deep pycnocline without added DOC, the trophic balance was changed to 0.44 (i.e. autotrophic). With a shallow pycnocline, the system remained net-autotrophic irrespective of DOC addition. We propose that increased precipitation in northern Europe due to climate change may result in changed density stratification and increased allochthonous DOC transport to the sea, leading to more heterotrophic coastal aquatic ecosystems. Such a scenario may entail reduced biological production at higher trophic levels and enhanced CO2 emission to the atmosphere.
|
|
