With a current estimate of ~1,000 million tons, mesopelagic fishes likely dominate the world total biomass. However, recent acoustic observations show that biomass could be significantly larger than estimate. Here we combine modelling and sensitivity analysis from Malaspina 2010 Circumnavigation Expedition to previous needs revised at least one order magnitude higher. We there is close relationship between open ocean primary production, energy transfer efficiency phytoplankton in higher what...

Abstract Models of visual range and location distances are crucial for quantification vision based feeding opportunities predation risk in the pelagic habitat. We compare an earlier published model with measurements reactive distance Gobiusculus flavescens relative to two species copepods. Although this gave reasonable predictions at low light intensities, higher intensities were much lower than those predicted by model. modified account saturation high intensities. With additional feature,...

Abstract The distribution, biomass, and predator-prey relationships of the pelagic assemblage in Masfjorden, western Norway, was studied January 1989. biomass dominated by particulate organic matter. Biomasses copepods, macroplankton, mesopelagic fishes were same order magnitude, while larger one less. Predator-prey seemed most important at intermediate higher trophic levels. Two sound-scattering layers, consisting adult Maurolicus muelleri (lower layer) juvenile M. (upper performed...

The deep scattering layer (DSL) is a ubiquitous acoustic signature found across all oceans and arguably the dominant feature structuring pelagic open ocean ecosystem. It formed by mesopelagic fishes invertebrates. DSL animals are an important food source for marine megafauna contribute to biological carbon pump through active flux of organic transported in their daily vertical migrations. They occupy depths from 200 1000 m at daytime migrate varying degree into surface waters nighttime....

Actions to transform food systems are key addressing biodiversity loss.

Secchi depth is a valuable proxy for detecting long term changes in the water clarity of oceanic and coastal ecosystems. We analyse approximately 40 000 observations, which are available from ICES, Baltic Sea North 20th century. Our results suggest pronounced effects bottom distance to coast on depth, we account this topographical effect an assessment change clarity. centennial shoaling 3.2 ± 0.2 5.8 0.6 m areas that shallower deeper than 100 Sea. For corresponding numbers were 1.8 0.3 5.2...

In microbial competition theory, the Michaelis‐Menten (MM) half‐saturation coefficient is often considered to be a trait of an organism defining competitive strength in trade‐off conflict with maximum uptake rate. Theoretical studies have shown that quadratic model characterizes rate, and this can approximated by MM model. Here, we review recent developments nutrient modeling particular emphasis on cell size, sites, molecular diffusion. We quantify bias approximation up 50% some...

Abstract With climate warming, a widespread expectation is that events in spring, such as flowering, bird migrations, and insect bursts, will occur earlier because of increasing temperature. At high latitudes, increased ocean temperature suggested to advance the spring phytoplankton bloom due stabilization water column. However, warming also expected cause browning lakes rivers increases terrestrial greening, ultimately reducing clarity coastal areas where freshwater drain. In shallow areas,...

Abstract The forest cover of Northern Europe has been steadily expanding during the last 120 years. More terrestrial vegetation and carbon fixation leads to more export surface waters. This may cause freshwater browning, as degraded plant‐litter ends up chromophoric (colored) dissolved organic matter. Although most ultimately drains coastal waters, link between browning water darkening is poorly understood. Here, we explore this relationship through a combination centennial records clarity,...

Abstract A simple, but general, simulation model is specified according to the state-of-the-art within phytoplankton modelling: Process representations are based upon prevailing theoretical and empirical given in literature, a set of earlier published values coefficients that have demonstrated good fit reliable observations was selected. The emerging then validated against data obtained from enclosure experiments with light-, N-, P- Si-limitations. We applied no tuning as purpose this test...

Aquatic food webs are affected from the bottom up by light through its effect on photosynthesis and productivity. But also has a top‐down effect, because it is crucial for visual foraging efficiency in many fish. Here we present data suggesting that marine pelagic primarily structured vision For light‐limited fjord ecosystems, show abundance of zooplanktivorous fish proportional to vertical extension feeding habitat, represented inverse absorbance coefficient water column. We both...

Abstract Due to advective impact few consistent time-series describing the population development of copepod C.finmarchicus exist. Quantitatively, spring generation seems be most important, and especially in northern areas one per year prevail. A fecundity 102-103 eggs female-1 a sex ratio 1:1 then give maximal reproductive rate 3.9-6.2 year-1. This low compensated by mortality due effective predator avoidance terms diurnal seasonal vertical migrations. We have calculated that renewal...

We have applied the population surface method to estimate mortality rates of eggs, nauplii, and copepodids Calanus spp. in two Norwegian fjords with contrasting predator guilds. Efforts were concentrated Lurefjorden on western coast (sampled weekly from late February mid‐June), an unusual fjord dominated by invertebrate (tactile) planktivores. In addition, monthly sampling Sørfjorden was carried out for comparisons. The latter resembles most Western that it contains populations vertebrate...

Light is an important limiting factor for the visual foraging process in fishes, and light regime may potentially affect competition between tactile predators. We investigated two equal‐sized fjords of quite different pelagic food web structure. Earlier studies have revealed that jellyfish Periphylla periphylla dominates Lurefjorden, while fish predators dominate other fjord, Masfjorden. Furthermore, mesozooplankton stock Lurefjorden larger both total biomass size individuals. Hence, earlier...

Overwintering Calanus spp. were studied in four Norwegian fjords with different predator regimes and ranging depth from 380 to 1300 m. Three held both the planktivorous mesopelagic fish Maurolicus muelleri Benthosema glaciale invertebrate predators, whereas one lacked but had especially high abundance of several predators. Co‐occurrence C. finmarchicus , helgolandicus glacialis rendered distinction between effects environmental conditions inherent species properties choice difficult. The...

At the end of July 1989, toxin-producing Prymnesium parvum was spread through a fjord system in surge freshwater released from hydroelectric power plant. In total, 750 tonnes Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) died fish farms. germinated brackish surface layer branch which, during July, characterized by longer residence time, higher temperatures, lower nitrogen silicate concentrations than rest system. Nutrient loading (especially phosphate) farms may,...

Plankton are typically divided into phytoplankton and zooplankton in marine ecosystem models. Yet, most protists the photic zone engage some degree of phagotrophy, it has been suggested that trophic strategy is really a continuum between pure phototrophs (phytoplankton) phagotrophs (unicellular zooplankton). Such strategies well represented by trait-based modelling techniques. A key model ingredient size individual cells, as constrains affinities for nutrient uptake, photosynthesis active...

We make a comparison of the mesopelagic sound scattering layers (SLs) in two contrasting optical environments; clear Red Sea and murkier coastal waters Norway (Masfjorden). The depth distributions SL Masfjorden are shallower narrower than those Sea. This difference distribution is consistent with hypothesis that organisms distribute according to similar light comfort zones (LCZ) environments. Our study suggest surface underwater measurements ranging more 10 orders magnitude required assess...

Previous studies have shown decline in dissolved oxygen of the ocean basins. A hypothesis for this development is that warming through increased stratification has caused reduced ventilation interior ocean. Here we provide evidence ventilation, which been associated with a 1 °C North Atlantic Water (NAW), contributed to recent deoxygenation mesopelagic zone Norwegian fjord, Masfjorden. Our results suggest after "Great Salinity Anomalies" around 1980, led decreased frequency high-density...

Zooplankton mortality is commonly estimited from time series of abundances (horizontal life table approach) with the assumption that transport processes are minor influence. This violated in marine environment. We provide equations appropriate for analysis stage distributions zooplankton samples at a single (vertical that, certain circumstances, facilitate estimation without requiring abundances. A primary daily recruitment to particular should not be characterized by strong upward or...

Based on existing models of fish vision and turbulence‐mediated ingestion rates, we develop a model rates in larval that combines several physical properties the environment (turbulence, irradiance, light attenuation) visual characteristics predators prey. The range was calibrated with observed estimates herring ( Clupea harengus ) cod Gadus morhua ). improved ability length larvae predicted to be most sensitive part model. Both turbulence had strong impacts rate fish. optimal level...