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Remote sensing observations from satellites and global biogeochemical models have combined to revolutionize the study of ocean biogeochemical cycling, but comparing the two data streams to each other and across time remains challenging due to the strong spatial-temporal structuring of the ocean. Here, we show that the Wasserstein distance provides a powerful metric for harnessing these structured datasets for better marine ecosystem and climate predictions. The Wasserstein distance complements commonly used point-wise difference methods such as the root-mean-squared error, by quantifying differences in terms of spatial displacement in addition to magnitude. As a test case, we consider chlorophyll (a key indicator of phytoplankton biomass) in the northeast Pacific Ocean, obtained from model simulations, in situ measurements, and satellite observations. We focus on two main applications: (i) comparing model predictions with satellite observations, and (ii) temporal evolution of chlorophyll both seasonally and over longer time frames. The Wasserstein distance successfully isolates temporal and depth variability and quantifies shifts in biogeochemical province boundaries. It also exposes relevant temporal trends in satellite chlorophyll consistent with climate change predictions. Our study shows that optimal transport vectors underlying the Wasserstein distance provide a novel visualization tool for testing models and better understanding temporal dynamics in the ocean.

Simple Summary: Otoliths, which are calcium carbonate structures found in the inner ears of fish, can be used to describe the use of freshwater and saltwater habitats during the lifespan of fish. This is performed by looking at the ratio of strontium to calcium along the radius of an otolith, where a high ratio indicates the use of saltwater and a low ratio indicates the use of freshwater. We studied brown trout (Salmo trutta L.) from the Swedish River Emån. We found that most brown trout, as expected, spent the first 1–2 years of their lives in freshwater before migrating to the Baltic Sea. We also found that 13% spent considerably less than one year in the river, which was not expected based on classical life history patterns for brown trout. In addition, we found that brown trout, which ranged from 3 to 6 years of age, returned to freshwater 2.3 times, and the amount of time spent in freshwater after hatching was negatively related to the number of visits to freshwater. Previous studies have explained that precocial migration occurs when there is a risk of drought. This explanation cannot apply to the permanently flowing River Emån. By analyzing otolith microchemistry, we examined the use of freshwater and marine environments by brown trout Salmo trutta L. that spawn in the Swedish River Emån and migrate to the Baltic Sea. We estimated the time juveniles spent in freshwater and the number of times the fish returned to freshwater, presumably to spawn. Twenty-six percent of the fish migrated to sea by 1 year of age. However, 13% spent less than one year in the river. Most brown trout (48%) migrated to the sea between 1 and 2 years of age. On average, brown trout, which averaged 4.4 years in age (range 3–6 years), returned to freshwater 2.3 times, and there was an inverse relationship between time spent in freshwater after hatching and the number of visits to freshwater. Our results do not support the classical life history pattern, where brown trout spend one or more years in freshwater before migrating to the sea. Here, we found evidence that part of the population leaves freshwater during their first year. While the cause for precocial migration in the River Emån is not known, our results from this permanently flowing river do not support the idea proposed for other Baltic Sea populations, where the risk of drought has been suggested to be the cause. [ABSTRACT FROM AUTHOR]

Temperature during egg incubation and early development influences later life stages of fishes, potentially influencing survival. Throughout its distribution, Atlantic salmon (Salmo salar Linnaeus, 1758) have experienced population declines, and in view of ongoing global warming, we tested if temperature during the earliest developmental stages modified body shape and fin size when temperatures averaged 2.6 vs. 5.6 [degrees]C. This temperature difference simulates increases predicted in climate change scenarios. Based on previous studies, we hypothesized that salmon originating from eggs subjected to cold incubation temperatures would have slimmer bodies and larger pectoral and dorsal fins than salmon from eggs that experienced warmer temperatures. After hatching, the juveniles were raised for 1 year under identical temperatures, after which we measured their body shape and fin areas. We found no support for our hypothesis regarding body shape. Indeed, we found the opposite, with cold-incubated salmon having deeper bodies than warm-incubated salmon. For fin size, the pectoral fins of cold-incubated salmon were larger than for warm-incubated salmon as predicted, but there was no difference in dorsal fin size. These results suggest that global warming may lead to altered body shape and fin size, possibly affecting swimming performance, and thus raise questions about the ecological consequences of the changes. Key words: ectotherm, phenotypic plasticity, morphology, global warming, incubation temperature, Salmo salar, Atlantic salmon. La temperature durant l'incubation des oeufs et le developpement precoce influence les etapes subsequentes du cycle biologique des poissons et pourrait influencer leur survie. A la grandeur de son aire de repartition, le saumon atlantique (Salmo salar Linnaeus, 1758) a connu des baisses demographiques et, etant donne le rechauffement planetaire en cours, nous avons verifie si la temperature durant les toutes premieres etapes du developpement modifie la forme du corps et la taille des nageoires quand les temperatures moyennes sont de 2,6 et 5,6 [degrees]C. Cette difference de temperatures simule des augmentations predites par differents scenarios de changements climatiques. A la lumiere d'etudes anterieures, nous avons postule que les saumons issus d'oeufs assujettis a de basses temperatures d'incubation auraient des corps plus elances et de plus grandes nageoires pectorales et dorsales que les saumons issus d'oeufs incubes a des temperatures plus elevees. Apres leur eclosion, des poissons juveniles ont ete eleves pendant une annee a des temperatures identiques, apres quoi nous avons mesure la forme de leur corps et l'aire de leurs nageoires. Nous n'avons trouve aucun appui pour notre hypothese concernant la forme du corps. C'est en fait le contraire que nous avons constate, les saumons incubes a basse temperature presentant des corps plus hauts que les saumons incubes a temperature plus elevee. En ce qui concerne la taille des nageoires, les nageoires pectorales des saumons incubes a basse temperature etaient plus grandes que celles des saumons incubes a temperature elevee, conformement aux predictions, mais les nageoires dorsales ne presentaient aucune difference. Ces resultats indiqueraient que le rechauffement planetaire pourrait mener a la modification de la forme du corps et de la taille des nageoires, ce qui pourrait avoir une incidence sur la performance de nage, et ils soulevent des questions concernant les consequences ecologiques de ces changements. [Traduit par la Redaction] Mots-cles : ectotherme, plasticite phenotypique, morphologie, rechauffement planetaire, temperature d'incubation, Salmo salar, saumon atlantique., Introduction Increased temperature mediated by global warming represents a type of environmental stress with potentially large impacts on the earth's biota (Milligan et al. 2009; Bellard et al. 2012; Paaijmans [...]

Changes in the number, structure, and function of mitochondria during the early life stages of animals can play an important role for an organism's metabolic rate, growth, and health. Previous studies have shown that juvenile brown trout (Salmo trutta) subjected to elevated temperatures during the embryonic stage respond phenotypically with a reduced metabolic rate. The aim of this study was to explore if embryonic temperature affects the mitochondria content of young brown trout and as such explains the previously found differences in metabolic rates. Here, we optimize a quantitative PCR (qPCR) method for the mitochondria cytochrome c oxidase subunit I gene, and then use the method as a proxy for mitochondrial DNA content. We hypothesize that young trout subjected to elevated temperatures during the embryonic stage respond phenotypically with a reduced mitochondrial DNA content. To test this hypothesis, we subjected brown trout to either control ambient (4.4 ± 1.5 °C) or elevated temperatures (7.1 ± 0.6 °C) during embryogenesis. Subsequently, we extracted DNA from liver and white muscle tissue of juvenile brown trout from the two different incubation temperature treatments and successively optimized qPCR for mitochondrial DNA. We found that the amount of mitochondria DNA in liver tissue was 18 times higher than in white muscle tissue, but there was no significant difference in mitochondria content in liver or muscle tissue between brown trout exposed to elevated and ambient control temperatures during embryogenesis. We conclude that reduced metabolic rate is not likely associated with mitochondria DNA content. We also suggest that qPCR is a simple and cost-effective method to quantify mitochondria DNA in frozen and partly degraded tissue from different treatment groups and a useful proxy for identification of differences in mitochondria number. [ABSTRACT FROM AUTHOR]

This document discusses the impact of climate change on salmonid fishes in rivers. Climate warming poses a serious threat to these cold-adapted ectotherms, leading to population declines, genetic and phenotypic changes, and alterations in behavior, physiology, and distribution. Climate change also affects habitats, including flow regimes, vegetation, oxygen concentration, and water turbidity. The document highlights the importance of understanding these alterations to improve habitat and population management. It also provides insights into the effects of temperature on metabolic rates, genetic diversity, transcriptome, migration patterns, river flow, growth, and predator-prey interactions. The document concludes with a literature review on climate impacts on Pacific and Atlantic salmon, offering guidance for stakeholders, managers, and researchers. [Extracted from the article]

The consistency of the global declining trend of Atlantic salmon (Salmo salar) populations suggests that climate-driven reduced survival and growth at sea are the main driving factors. The southernmost populations have experienced the greatest declines, consistent with harsher conditions in natal fresh waters. We analyzed temporal trends in Spanish Atlantic salmon, important food organisms at sea, and climatic variables in the breeding (fresh water) and feeding (marine) salmon areas from 1950 onwards to elucidate drivers of declining patterns. Salmon abundance dropped abruptly in 1970-1971, plausibly linked to widespread overfishing coincident with incipient changes in the marine food webs and freshwater hydrology. A major regime shift in biophysical conditions throughout the North Atlantic salmon feeding grounds occurred in 1986-1987, driven by the concurrence of an abrupt acceleration in the anthropogenic warming trend and the warm phase of the Atlantic Multidecadal Oscillation. This regime shift may be the proximate cause of the collapse of Spanish salmon observed in 1988-1989, which kept declining in parallel to trends of ever-increasing ocean and freshwater temperatures, decreasing river flows, and poorer marine trophic conditions. La coherence de la tendance planetaire a la baisse des populations de saumon atlantique (Salmo salar) porte a croire que les reductions de la survie et de la croissance en mer causees par le climat en sont les principaux facteurs. Les populations les plus meridionales ont subi les plus grandes baisses, ce qui concorde avec des conditions plus difficiles dans les eaux douces natales. Nous avons analyse les tendances dans le temps du saumon atlantique espagnol, d'importants organismes lui servant de nourriture en mer et de variables climatiques dans ses aires de reproduction (en eau douce) et d'alimentation (en mer) a partir de 1950, afin de cerner les causes de ces declins. L'abondance du saumon a chute abruptement en 1970-1971, cette baisse etant plausiblement liee a la coincidence d'une surpeche repandue et de modifications emergentes aux reseaux trophiques marins et a l'hydrologie des cours d'eau douce. Un important changement du regime de conditions biophysiques dans toutes les aires d'alimentation du saumon dans l'ocean Atlantique Nord s'est produit en 1986-1987, cause par la cooccurrence d'une acceleration soudaine du rechauffement d'origine anthropique et de la phase chaude de l'oscillation atlantique multidecennale. Ce changement de regime pourrait etre la cause proximale de l'effondrement du saumon espagnol observe en 1988-1989, qui s'est poursuivi parallelement a des tendances d'augmentation continue des temperatures de l'eau de mer et de l'eau douce, de diminution des debits des rivieres et de deterioration des conditions trophiques marines. [Traduit par la Redaction], Introduction Current climate change is a main driver of the biodiversity loss that will not only increase but also accelerate global and local extinctions (Urban 2015). Specifically, both marine and [...]

Here, I review thermal influences on metabolic rates and aerobic scope; growth; adult body size; and reproductive and behavioural traits, such as tendency and timing of the migration of salmonid fishes. A thermal window bounded by the upper and lower incipient lethal temperatures (UILT and LILT) determines where salmonids can survive. For most salmonids, LILT is close to 0 and UILT is between 20 and 30 °C. UILT and LILT are influenced by the acclimation temperature. Thermal tolerance is affected by fish size and ambient oxygen content, which decreases with increasing temperature. Standard metabolic rate (SMR), the energy required to maintain essential functions, increases with temperature, whereas maximum metabolic rate (MMR) increases with temperature until reaching a peak (pejus). Then, it decreases gradually to zero, i.e., the upper critical limit (TCrit). Aerobic scope (AS = MMR-SMR) reaches its maximum at the pejus temperature. Metabolic rates and aerobic scope can be modified by temperatures that the fish experiences during embryogenesis and possibly also as larvae and young fry. At maximum feeding, maximum growth increases to a point at or below the pejus temperature. The optimum temperature for growth decreases with reduced food intake and increased body size. As for metabolic rate, the growth rate is influenced by the temperature during embryonic development. In a warmer climate, adult body size is expected to decrease chiefly because of a younger age at maturity. Parental fish retained at a higher temperature during maturation produce larger eggs, and this change in egg size may also be transferred to next-generation offspring. Furthermore, embryogenesis in warmer water leads to larger gonad and egg sizes at maturity. Water temperature influences locomotion, foraging and migratory activity. In a warmer climate, juveniles migrate to the sea earlier in spring. In addition, higher embryo temperature leads to delayed return of adult salmon from the ocean. Thus, temperature affects life history traits of salmonid fishes, partly as a direct effect on metabolic rates and food consumption and partly induced as a phenotypically plastic effect. The phenotypically plastic response may preadapt offspring to perform better in the expected future thermal environment. [ABSTRACT FROM AUTHOR]

The particle size distribution (PSD) of suspended particles in near-surface seawater is a key property linking biogeochemical and ecosystem characteristics with optical properties that affect ocean color remote sensing. Phytoplankton size affects their physiological characteristics and ecosystem and biogeochemical roles, e.g., in the biological carbon pump, which has an important role in the global carbon cycle and thus climate. It is thus important to develop capabilities for measurement and predictive understanding of the structure and function of oceanic ecosystems, including the PSD, phytoplankton size classes (PSCs), and phytoplankton functional types (PFTs). Here, we present an ocean color satellite algorithm for the retrieval of the parameters of an assumed power-law PSD. The forward optical model considers two distinct particle populations: phytoplankton and non-algal particles (NAPs). Phytoplankton are modeled as coated spheres following the Equivalent Algal Populations (EAP) framework, and NAPs are modeled as homogeneous spheres. The forward model uses Mie and Aden–Kerker scattering computations, for homogeneous and coated spheres, respectively, to model the total particulate spectral backscattering coefficient as the sum of phytoplankton and NAP backscattering. The PSD retrieval is achieved via spectral angle mapping (SAM), which uses backscattering end-members created by the forward model. The PSD is used to retrieve size-partitioned absolute and fractional phytoplankton carbon concentrations (i.e., carbon-based PSCs), as well as particulate organic carbon (POC), using allometric coefficients. This model formulation also allows the estimation of chlorophyll a concentration via the retrieved PSD, as well as percent of backscattering due to NAPs vs. phytoplankton. The PSD algorithm is operationally applied to the merged Ocean Colour Climate Change Initiative (OC-CCI) v5.0 ocean color data set. Results of an initial validation effort are also presented using PSD, POC, and picophytoplankton carbon in situ measurements. Validation results indicate the need for an empirical tuning for the absolute phytoplankton carbon concentrations; however these results and comparison with other phytoplankton carbon algorithms are ambiguous as to the need for the tuning. The latter finding illustrates the continued need for high-quality, consistent, large global data sets of PSD, phytoplankton carbon, and related variables to facilitate future algorithm improvements. [ABSTRACT FROM AUTHOR]

Aim: Dispersal and environmental gradients shape marine microbial communities, yet the relative importance of these factors across taxa with distinct sizes and dispersal capacity in different ocean layers is unknown. Here, we report a comparative analysis of surface and deep ocean microbial beta diversity and examine how these patterns are tied to oceanic distance and environmental gradients. Location: Tropical and subtropical oceans (30°N–40°S). Time period: 2010–2011. Major taxa studied: Prokaryotes and picoeukaryotes (eukaryotes between 0.2 and 3 μm). Methods: Beta diversity was calculated from metabarcoding data on prokaryotic and picoeukaryotic microbes collected during the Malaspina expedition across the tropical and subtropical oceans. Mantel correlations were used to determine the relative contribution of environment and oceanic distance driving community beta diversity. Results: Mean community similarity across all sites for prokaryotes was 38.9% in the surface and 51.4% in the deep ocean, compared to mean similarity of 25.8 and 12.1% in the surface and deep ocean, respectively, for picoeukaryotes. Higher dispersal rates and smaller body sizes of prokaryotes relative to picoeukaryotes likely contributed to the significantly higher community similarity for prokaryotes compared with picoeukaryotes. The ecological mechanisms determining the biogeography of microbes varied across depth. In the surface ocean, the environmental differences in space were a more important factor driving microbial distribution compared with the oceanic distance, defined as the shortest path between two sites avoiding land. In the deep ocean, picoeukaryote communities were slightly more structured by the oceanic distance, while prokaryotes were shaped by the combined action of oceanic distance and environmental filtering. Main conclusions: Horizontal gradients in microbial community assembly differed across ocean depths, as did mechanisms shaping them. In the deep ocean, the oceanic distance and environment played significant roles driving microbial spatial distribution, while in the surface the influence of the environment was stronger than oceanic distance. [ABSTRACT FROM AUTHOR]

Field studies have revealed that many ectotherms mature younger and smaller in warmer environments although they grow faster. This has puzzled ecologists because the direct effect of factors that accelerate growth is expected to be larger, not smaller size. We tested this experimentally for Atlantic salmon (Salmo salar) at two winter temperatures and diets. Logistic regression revealed that the probability of maturation during the second year in sea water, relative to the probability of older maturation, increased with temperature and growth rate during the first winter. Also, large size and high condition factor 1 year prior to maturation stimulated maturation. In females, a high lipid diet increased the probability of maturation as one-sea-winter fish, and there were significant interactions between winter temperature and food quality and between body size and condition factor the first autumn in sea water. Thus, if the direct effect of temperature on growth rate is the main effect of warming, salmon are likely to attain maturity younger and smaller. Also, richer food decreased age at maturation in females. This finding has consequences for interpretations of climate change impacts on age at maturity in Atlantic salmon and may also hold for many other ectotherm species. Des etudes de terrain ont revele que de nombreux ectothermes atteignent la maturite a des ages et des dimensions moindres en milieux plus chauds, bien que leur croissance soit plus rapide. Il s'agit la d'une enigme pour les ecologistes puisque l'effet direct des facteurs qui accelerent la croissance devrait etre une taille plus grande, non plus petite. Nous avons verifie cette hypothese experimentalement chez des saumons atlantiques (Salmo salar) soumis a deux temperatures et regimes alimentaires hivernaux. La regression logistique a revele que la probabilite de maturation durant la deuxieme annee en eau de mer comparativement a celle d'une maturation a un age plus avance augmentait parallelement a la temperature et au taux de croissance durant le premier hiver. En outre, une grande taille et un coefficient de condition eleve 1 an avant la maturation stimulaient cette derniere. Chez les femelles, un regime riche en lipides se traduisait par une probabilite accrue de maturation pour les poissons ayant passe un hiver en mer, et il y avait des interactions significatives entre la temperature hivernale et la qualite de la nourriture, ainsi qu'entre la taille du corps et le coefficient de condition durant le premier automne en eau de mer. Ainsi, si l'effet direct de la temperature sur le taux de croissance est le principal effet d'un rechauffement, il est probable que les saumons atteignent la maturite a des ages et des tailles plus faibles. En outre, des aliments plus riches entrainent une diminution de l'age a la maturation chez les femelles. Ce resultat a des consequences sur les interpretations de l'incidence des changements climatiques sur l'age a la maturite chez le saumon atlantique et pourrait egalement s'appliquer a de nombreuses autres especes ectothermes., Introduction Recent research has revealed that many marine, diadromous, and freshwater living ectotherms mature younger and at smaller body sizes although they grow faster in warmer environments (e.g., Todd et [...]

We explored the mechanisms of density-dependent growth in Arctic char (Salvelinus alpinus) by comparing the energetics of growth, consumption, and activity obtained under three replicated density treatments in a large-scale enclosure (90 m2 surface area) experiment. The enclosures permitted the entry of zooplankton and allowed char to feed on the bottom and at the surface of the lake. We found a negative (power) relationship between growth and density. Char consumption rate decreased linearly with increasing density. Growth efficiency was affected by fish density in a similar manner as growth rate. Finally, activity increased with fish density and was particularly high at high densities. Our findings illustrate the complexity of the relationships among consumption, activity, growth rates, and fish density and bring further evidence to the possible involvement of behavioural mechanisms in density-dependent processes, notably by modulating activity costs with density. Nous explorons les mecanismes de croissance dependant de la densite chez l'omble chevalier (Salvelinus alpinus) en comparant la croissance, la consommation, l'efficacite de croissance, et l'activite estimees de maniere independante, avec replication, sous trois traitements de differentes densites, au cours d' une experience a grand echelle en enclos (surface : 90 m2). Les enclos etaient construits de maniere a assurer la libre circulation du zooplancton et a permettre aux ombles de s' alimenter a la surface et au fond du lac. Nous avons observe une relation negative (de puissance) entre la croissance et la densite de poissons. La relation entre la consommation et la densite etait lineaire et negative. L'effet de la densite sur l'efficacite de croissance etait semblable a l'effet de la densite sur le taux de croissance. Enfin, l'activite augmentait avec la densite, cet effet etant particulierement marque a hautes densites. Ces resultats illustrent la complexite des relations entre la consommation, l'activite, la croissance et la densite des poissons et fournissent de nouveaux indices sur l'implication possible de mecanismes comportementaux, notamment par l'entremise de la modulation des couts de l'activite en fonction de la densite, dans les processus dependant de la densite., Introduction It is well accepted that density contributes to the regulation of population abundance. The agreement on the effect of density on individual growth has been less unanimous (Elliott 1994). [...]

A common environment experiment was conducted to assess the magnitude of the difference in growth, consumption, activity rate, and spatial and temporal patterns of habitat use between morphologically different populations of Arctic char (Salvelinus alpinus) originating from two Norwegian lakes. These two lakes contrasted sharply in terms of surface area, depth, elevation, length of the winter period, and fish community structure (presence-absence of brown trout, Salmo trutta). The experimental framework encompassed four littoral enclosures (average volume, 146 [m.sup.3]) stocked with char from either of the two populations with duplicated treatments. Char morphology was quantified with numerical image analysis, food consumption was estimated using caesium analysis ([.sup.133]Cs), and activity cost and patterns were determined using video cameras. Char populations were morphologically distinct and reacted differently in growth (1.9-fold difference between populations), food consumption (3-fold difference), and spatial activity patterns (20-fold difference) to the conditions prevailing in the enclosures. The results highlight that functional differences between morphologically distinct char may drive important differences in their bioenergetic and behavioural responses when exposed to similar environmental conditions. Such functional differences should be incorporated when developing habitat or trophic cascade models. Resume: Une experience en conditions communes a ete realisee afin de quantifier la magnitude des differences de croissance, de consommation, d'activite et de patrons spatiaux et temporels d'utilisation d'habitat chez des ombles chevaliers (Salvelinus alpinus) provenant de deux populations morphologiquement differentes, issues de deux lacs de Norvege. Ces deux lacs differaient de maniere marquee en terme d'aire, de profondeur, d'altitude, de la duree de leur periode d'hivernage et de structure de leurs communautes de poissons (presence ou absence de truite brune, Salmo trutta). Le cadre experimental utilise comprenait quatre enclos de grandes tailles (volume moyen, 146 [m.sup.3]), chacun ensemence avec des ombles provenant de l'une ou l'autre des populations. Les reponses bioenergetiques ont ete estimees en termes de taux de croissance, de consommation et d'activite et des patrons spatiaux et temporels d'activite. Nous avons quantifie la morphologie des ombles, estime leur taux de consommation a l'aide d'un traceur chimique ([.sup.133]Cs) et estime leur taux d'activite et leurs patrons d'activite a l'aide de video-cameras. Les deux populations d'omble chevalier sont morphologiquement distinctes et ont reagi differemment en termes de taux de croissance (un difference d'un facteur de 1,9 entre populations), de consommation (difference d'un facteur de 3) et de patrons spatiaux d'activite (difference d'un facteur de 20) aux conditions qui prevalaient dans les enclos. Ces resultats suggerent que les differences fonctionnelles entre des morphs d'ombles chevaliers peuvent engendrer des differences importantes dans la facon avec laquelle ils repondent, dun point de vue bioe nergetique et comportemental, a un ensemble de conditions environnementales semblables. E tant donne leurs grandeurs, ces differences devraient etre considerees lors de la construction et de l'application de modeles de qualite d'habitat ou de modeles de cascade trophique., Introduction Niche adaptation is a fundamental issue in ecology. Niche adaptation may occur when organisms improve their ability to exploit their habitat through phenotypic plasticity and natural selection. In cases [...]

The particle size distribution (PSD) of suspended particles in near-surface seawater is a key property linking biogeochemical and ecosystem characteristics with optical properties that affect ocean color remote sensing. Phytoplankton size affects their physiological characteristics and ecosystem and biogeochemical roles, e.g. in the biological carbon pump, which has an important role in the global carbon cycle and thus climate. It is thus important to develop capabilities for measurement and predictive understanding of the structure and function of oceanic ecosystems, including the PSD, phytoplankton size classes (PSCs) and phytoplankton functional types (PFTs). Here, we present an ocean color satellite algorithm for the retrieval of the parameters of an assumed power-law PSD. The forward optical model considers two distinct particle populations (particle assemblage categories) -- phytoplankton and non-algal particles (NAP). Phytoplankton are modeled as coated spheres following the Equivalent Algal Populations (EAP) framework, and NAP are modeled as homogeneous spheres. The forward model uses Mie and Aden-Kerker scattering computations, for homogeneous and coated spheres (for phytoplankton and NAP, respectively) to model the total particulate spectral backscattering coefficient as the sum of phytoplankton and NAP backscattering. The PSD retrieval is achieved via Spectral Angle Mapping (SAM) which uses backscattering end-members created by the forward model. The PSD is used to retrieve size-partitioned absolute and fractional phytoplankton carbon concentrations (i.e. carbon-based PSCs), as well as particulate organic carbon (POC), using allometric coefficients. The EAP-based formulation allows for the estimation of chlorophyll-a concentration via the retrieved PSD, as well as the estimation of the percent of backscattering due to NAP vs. phytoplankton. The PSD algorithm is operationally applied to the merged Ocean Colour Climate Change Initiative (OC-CCI) v5.0 ocean color data set. Results of an initial validation effort are also presented, using PSD, POC, and pico-phytoplankton carbon in-situ measurements. Validation results indicate the need for an empirical tuning for the absolute phytoplankton carbon concentrations; however these results and comparison with other phytoplankton carbon algorithms are ambiguous as to the need for the tuning. The latter finding illustrates the continued need for high-quality, consistent, large global data sets of phytoplankton carbon and related variables to facilitate future algorithm improvements. [ABSTRACT FROM AUTHOR]

Environmental factors influencing parents or offspring during embryogenesis can have knock-on effects at later life stages of the offspring. These effects may prepare the progeny for conditions that they may encounter as larvae, juveniles, and/or adults. Here, we give examples on how knock-on effects of temperature and predator cues can affect phenotypes of fish, amphibians, and reptiles. Such effects are best described in reptiles, but are generally widespread among ectotherms. Most of the species are oviparous with egg incubation outside the mother's body. The eggs can be exposed to highly different and variable environmental conditions, and developmental plasticity may help offspring cope with influences they may encounter at a later stage, e.g., whether the habitat will be warmer or colder and/or safer or riskier than what they a priori are adapted for. Knock-on effects can be considered a subset of phenotypically plastic responses. They can be instantaneous or delayed, have a physiological foundation, and can be manifested as temperature-dependent sex determination and changes in morphological, physiological, life-history, and behavioral characters. They are often, but not exclusively, assumed evolutionarily favorable, particularly beneficial for invasive species and during periods of rapidly changing environments. However, although several studies suggest that plasticity in some cases increases survival and reproductive success, the fitness gain is still virtually untested. It is assumed that epigenetic mechanisms, such as DNA methylation and histone modifications, could ultimately be important components of molecular mechanisms that allow early perceived cues to be expressed at a later stage in life. Although some empirical cases support this, evidence is still mostly circumstantial. Future research should investigate mechanisms and fitness effects of early environmental stimuli. These effects are important for the ecology of species and should be taken into account in experiments on ecological effects of environmental variables. This is of particular interest today because of climate change and increasing anthropogenic habitat alterations. [ABSTRACT FROM AUTHOR]

The present experiment tested if temperature during embryogenesis and parental heritage affected the migratory behaviour of young brown trout Salmo trutta. Two parental forms were used, a freshwater resident form and an anadromous form, both from the same river system but geographically isolated since 1993–95. Four groups of young S. trutta were produced and reared from (a) freshwater resident parents spawning in a tributary to the River Imsa, Norway, (b) anadromous parents spawning in the main stem of the same river system, (c) resident male × anadromous female parents and (d) resident female × anadromous male parents. The eggs were incubated until first exogenous feeding in River Imsa water, either unheated or heated c. 2.7°C above ambient temperature. Thereafter, all fish experienced the same ambient river temperature until release. Groups were released below an impassable waterfall 900 m upstream of the mouth of the River Imsa, either as age‐0 in October 2019 or as age‐1 in May 2020. About 7.5% of the released fish moved downstream and were captured in a trap at the outlet. For any given body size, the proportion of warm incubated trout that moved downstream was greater than the proportion of cold incubated trout. It was also found that most emigrants of the October‐released S. trutta were caught within a month of release. Also, most May‐released S. trutta emigrated in October. The offspring of the freshwater resident parents emigrated to a larger extent than offspring of anadromous parents. Thus, the difference in emigration with regard to embryonic temperature was phenotypically plastic and may be associated with an epigenetic effect of the thermal conditions during early development. The effect of parental origin suggests there may be genetic divergence between the geographically isolated populations. [ABSTRACT FROM AUTHOR]

Abstract: Activity rate of Arctic char (Salvelinus alpinus) held in 90 [m.sup.2] littoral enclosures were estimated using bioenergetic (with consumption estimated using stable caesium, [sup.133]Cs) and behavioural approaches (with fish [...]

It is well documented that human modification of the hydrological cycle has profoundly affected the flow of liquid water across the Earth's land surface. Alteration of water vapor flows through land-use changes has received comparatively less attention, despite compelling evidence that such alteration can influence the functioning of the Earth System. We show that deforestation is as large a driving force as irrigation in terms of changes in the hydrological cycle. Deforestation has decreased global vapor flows from land by 4% (3,000 [km.sup.3]/yr), a decrease that is quantitatively as large as the increased vapor flow caused by irrigation (2,600 [km.sup.3]/yr). Although the net change in global vapor flows is close to zero, the spatial distributions of deforestation and irrigation are different, leading to major regional transformations of vapor-flow patterns. We analyze these changes in the light of future land-use-change projections that suggest widespread deforestation in sub-Saharan Africa and intensification of agricultural production in the Asian monsoon region. Furthermore, significant modification of vapor flows in the lands around the Indian Ocean basin will increase the risk for changes in the behavior of the Asian monsoon system. This analysis suggests that the need to increase food production in one region may affect the capability to increase food production in another. At the scale of the Earth as a whole, our results emphasize the need for climate models to take land-use change, in both land cover and irrigation, into account. deforestation | irrigation | land-use changes | climate change | evapotranspiration