Effects of decadal climate change on zooplankton over the last 50 years in the western subarctic North Pacific

Decadal‐ to multi‐decadal variations have been reported in many regional ecosystems in the North Pacific, resulting in an increasing demand to elucidate the link between long‐term climatic forcing and marine ecosystems. We detected phenological and quantitative changes in the copepod community in response to the decadal climatic variation in the western subarctic North Pacific by analyzing the extensive zooplankton collection taken since the 1950s, the Odate Collection. Copepod species were classified into five seasonal groups depending on the timing of the annual peak in abundance. The abundance of the spring community gradually increased for the period 1960–2002. The spring–summer community also showed an increasing trend in May, but a decadal oscillation pattern of quasi‐30‐year cycles in July. Phenological changes coincided with the climate regime shift in the mid‐1970s, indicated by the Pacific decadal oscillation index (PDO). After the regime shift, the timing of the peak abundance was delayed one month, from March–April to April–May, in the spring community, whereas it peaked earlier, from June–July to May–June, in the spring–summer community, resulting in an overlap of the high productivity period for the two communities in May. Wintertime cooling, followed by rapid summertime warming, was considered to be responsible for delayed initiation and early termination of the productive season after the mid‐1970s. Another phenological shift, quite different from the previous decade, was observed in the mid‐1990s, when warm winters followed by cool summers lengthened the productive season. The results suggest that climatic forcing with different decadal cycles may operate independently during winter–spring and spring–summer to create seasonal and interannual variations in hydrographic conditions; thus, combinations of these seasonal processes may determine the annual biological productivity.     

A new trend in the development of the phytoplankton in the Oosterschelde (SW Netherlands) during and after the construction of a storm-surge barrier

During the pre-barrier period (1982–83), the Oosterschelde phytoplankton were a diatom-dominated community, comprising a species-rich assemblage throughout the year. Assemblages of spring, early summer and summer, developed in response to a gradually evolving turbidity-light gradient during the course of the year.During the barrier-construction period (1984–87), characterized by decreasing current velocities, increasing sedimentation of suspended matter, increasing water transparencies and unchanged nutrient conditions, the growth season for the phytoplankton started earlier and lasted longer. Some flagellate species responded by much higher biomass than before. The impact of short-term climatic factors during this period, notably severe winters, could be illustrated with examples of clear responses of some species (e.g. Biddulphia aurita).In the post-barrier years (1987–90) a changed light-nutrient-salinity regime (i.e. much light, limitation of nitrate, high salinity) was demonstrated and an extended summerseason developed, without the original gradual transitions. This was reflected in an a-seasonal trend of the phytoplankton assemblage, where summer species were already observed in spring and spring species decreased in abundance. In summer small flagellates increased and some weakly silicified diatom species made their appearance. In the eastern compartment no colony formation of Phaeocystis occurred in summer and this was thought to be due to nitrate limitation. Changes in abundance of some species (Phaeocystis, Ditylum brightwellii, Skeletonema costatum), occurring during the entire period of investigation (1982–90), could be explained using field observations compared with experimental evidence from the literature.The relationship between species composition and biomass on the one hand and environmental variables on the other hand, was analysed in a Canonical Correspondence Analysis, for both compartments separately.     

Population differences in the timing of diapause: a test of hypotheses

Summary The reproductive phenology of the freshwater copepod Diaptomus sanguineus differs markedly between populations residing in two Rhode Island ponds. In a permanent pond the population switches abruptly from making subitaneous (immediately hatching) eggs to diapausing eggs at the end of March each year. In contrast, a temporary pond population switches egg types in May, returns to production of subitaneous eggs in June, and concludes the reproductive season by making diapausing eggs in July. An ESS model suggests that the pattern of diapause expected of a copepod population is a function of annual variation in the onset of harsh conditions (catastrophe date). When variation is relatively low, the superior strategy is for diapause to begin a constant period before the mean catastrophe date. When variation is high, females should make first subitaneous eggs and then diapausing eggs irrespective of the expected catastrophe date. With discrete generations, such a population would alternate between egg types. In the permanent pond, variation of catastrophe date the spring onset of planktivory by sunfish is low, whereas in the temporary pond variation of the catastrophe (pond drying) is high. The model predicts well the phenology of the two copepod populations.In the research reported here, we tested the hypothesis that copepods from the permanent pond, which switch to diapause at the same time every year, are cued by the environment to begin diapause (i.e. by photoperiod, temperature, or both), whereas those from the temporary pond make both egg types regardless of environmental conditions. In opposition to our hypothesis, experimental results indicate that diapause in both populations is cued by the environment. The distinct reproductive phenologies documented in the two populations apparently result from the copepods responding to different environmental cues, rather than one being responsive to the environment while the other is not.     

Prediction of the activity of rabies foci based on biotic and climatic factors

Investigations carried out in Voronezh Province have shown that the activity of the foci of rabies is poorly related to the changes in the fox population. For the prognostication of the situation to be expected, good promise is held in the use of such data as the size of the population of murine rodents and the climatic conditions of the autumn and winter period. Rises in rabies morbidity are observed following an increase in the number of murine rodents (26% and higher) in autumn and a sharp decrease in their number by the spring of the epizootic year, and also if in the preceding year autumn began early and temperatures in winter and spring were above the average level, flood came quickly and water levels were low. It is expedient to use these regularities for the short-term prognosis of the epidemiological situation.     

Grazing impact of copepod assemblages and gravitational flux in coastal and oceanic waters off central Chile during two contrasting seasons

In evaluating carbon flux in coastal and oceanic waters offcentral Chile (~36°S), the grazing pressure by copepod size-assemblagesand the gravitational flux from the surface layer were estimatedduring two contrasting seasons: spring upwelling (October 1998)and winter (July 1999) periods. Grazing pressure upon phytoplanktonbiomass was small (<5%) during both periods at all stations.It was, however, an important proportion of primary productionat the coast during the spring (17–43%) but minimal inwinter (<5%) while, at the oceanic station, it was significantduring both seasons (13–46%). Similarly, the downwardflux of particulate organic carbon was a significant percentageof primary production at the coast during the spring (31%) andless so in winter (15%); at the oceanic station, it was a higherfraction during both seasons (46–47%). Copepod pelletswere only a minor component of the faecal flux, suggesting thatthey were rapidly recycled in the water column. The seasonaldifferences in these carbon fluxes in the coastal upwellingzone were related directly to the larger quantities of organicmatter in the water column during the spring upwelling period,including higher chlorophyll a concentrations and primary productionrates. During the winter, the particulate organic carbon appearsto be mainly recycled in the water column. In the oceanic zone,in contrast to what is expected, a large percentage of the primaryproduction appears to be exported during both periods, thoughconsumption by copepod assemblages was also important, suggestingsignificant horizontal carbon export from the coast to the openocean.     

Are badgers ‘Under The Weather’? Direct and indirect impacts of climate variation on European badger (Meles meles) population dynamics

Weather conditions, and how they in turn define and characterize regional climatic conditions, are a primary limit on global species diversity and distribution, and increasing variability in global and regional climates have significant implications for species and habitat conservation. A Capture–Mark–Recapture study revealed that badger (Meles meles) life history parameters interact in complicated ways with annual variability in the seasonality of temperature and rainfall, both in absolute and in phenological terms. A strong predictive relationship was observed between survival and both temperature and late‐summer rainfall. This link at the population dynamics level was related to individual body‐weight increases observed between summer and autumn. In addition, fecundity was correlated with spring rainfall and temperature. We investigated and confirmed that relationships were consistent with observed variation in the intensity of a parasitic infection. Finally, fecundity during any given year correlated with conditions in the preceding autumn. Badger survival also correlated with late winter weather conditions. This period is critical for badgers insofar as it coincides with their peak involvement in road traffic accidents (RTAs). RTA rate during this period was linked strongly to temperature, underlining the intricate ways in which a changing climate might interact with anthropogenic agents to influence species' population processes. Equinoctial conditions produced significant population driver effects. That is, while summers will always be relatively warm compared with winters, spring and autumn weather can be more variable and functionally delimit the ‘productive’ vs. nonproductive period of the year in terms of badger behavioural and physiological cycles. This study highlights how appropriately informed conservation strategies, mindful of trends in climatic conditions, will become ever‐more essential to ensure the survival of many species globally.     

Is the copepod egg production in a highly turbid estuary (the Gironde, France) a function of the biochemical composition of seston?

The influence of the biochemical composition of particles originating from surface waters of the Gironde estuary on egg production rates of Eurytemora affinis zooplanktonic population was studied. In the high turbidity zone, suspended particulate matter had a low nutritional quality because the easily available organic fraction represented less than 15% of the overall particulate organic matter. In waters located seaward of the high turbidity zone, a slight increase in nutritional quality was observed. As a result, the sum of easily extractable organic macromolecules represented 15 to 33% of the overall particulate organic matter. The present study suggests that the low egg-production rate of Eurytemora affinis, occurring in the high turbidity zone, results from combined effects of temperature and bad feeding conditions in the area. Low copepod production can be explained by little phytoplankton growth due to light limitation and, therefore, restricted food availability, as well as difficulties in food selection, non-living particle may being dominant.     

Variations in the composition and adsorption behavior of dissolved organic matter at a small, forested watershed

This study investigated the properties and sorption by goethite of bulk (unfractionated) dissolved organic matter (DOM) from surface and shallow groundwaters at McDonalds Branch, a small freshwater fen in the New Jersey Pine Barrens (USA). Water samples were collected in the spring and fall seasons from two surface-water sampling sites, an upstream potential recharge area and a downstream discharge area, as well as from a set of in-stream nested wells in the upstream potential recharge area. Changes in DOM concentration, molecular weight distribution, and molar absorptivity at 280 nm were measured. Surface and shallow (1.6 m below land surface) groundwater samples collected in spring 1997 in the potential recharge zone (actual recharge impeded by an extensive clay lens) were found to be very similar in terms of DOM concentrations and physicochemical properties and is believe to originate from a common source. Samples taken in fall 1997 yielded no surface water because of drought conditions, and the shallow groundwater DOM collected from the recharge well contained significantly less and chemically altered DOM. This change in chemical properties is believed to be caused in part by fractionation resulting from sorption to mineral phases. Batch isotherm experiments show that sorption by goethite of the DOM from both spring surface and shallow groundwaters in the potential recharge area were similar, whereas the fall groundwater possessed a much lower affinity for the sorbent. This study demonstrated that shallow groundwaters collected under different climatic and hydrologic conditions (spring, high flow versus fall, drought conditions) resulted in different physicochemical properties and adsorption affinities.     

Mediterranean marine copepods: basin-scale trends of the calanoid Centropages typicus

The Mediterranean Sea is located in a crossroad of mid-latitude and subtropical climatic modes that enhance contrasting environmental conditions over both latitudinal and longitudinal ranges. Here, we show that the large-scale environmental forcing is reflected in the basin scale trends of the adult population of the calanoid copepod Centropages typicus. The species is distributed over the whole Mediterranean basin, and maximal abundances were found in the north-western basin associated to oceanic fronts, and in the Adriatic Sea associated to shallow and semi enclosed waters. The peak of main abundances of C. typicus correlates with the latitudinal temperature gradient and the highest seasonal abundances occurred in spring within the 14–18°C temperature window. Such thermal cline may define the latitudinal geographic region where C. typicus seasonally dominates the >200 μm-sized spring copepod community in the Mediterranean Sea. The approach used here is generally applicable to investigate the large-scale spatial patterns of other planktonic organisms and to identify favourable environmental windows for population development.     

Nitrogen supply from some soil types with various organic-matter treatments

Summary An evaluation of the N release by soil organic matter can be obtained by measurements of the course of soil mineral nitrogen on uncropped objects. This N mineralization was studied during several years on some soil types with incorporations of various organic matter. The real N mineralization on a given soil with similar inputs of organic matter varied little from year to year. On the other hand, the net result of NO ₃ ^– -N increase between spring and autumn showed wider variation, especially due to N losses.     

Prefledging Growth and Recruitment of Female Lesser Scaup

Annual variation in juvenile recruitment is an important component of duck population dynamics, yet little is known about the factors affecting the probability of surviving and breeding in the first year of life. Two hypothesized mechanisms to explain annual variability are indirect carry-over effects (COEs) from conditions experienced during the prefledging period and direct effects from climatic conditions during the postfledging period. We used Cormack-Jolly-Seber models to estimate apparent survival and detection rates of 643 juvenile female lesser scaup (Aythya affinis) marked just prior to fledging at Red Rock Lakes National Wildlife Refuge in southwestern Montana, USA, 2010–2018. We evaluated COEs from hatch date, a hatch date × spring phenology interaction, and conspecific duckling density in addition to a direct climatic effect of winter conditions (indexed by the El Niño Southern Oscillation [ENSO]) and spring habitat conditions on the study area. We used growth data from a subset (n = 190) of known-aged ducklings to estimate the influence of hatch date and conspecific density on prefledging growth to help identify mechanisms underlying COEs. Prefledging growth and juvenile apparent survival were negatively related to measures of conspecific duckling density. We found evidence that detection probability varied annually for juvenile (but not adult) scaup, possibly representing decisions to delay breeding and not return to or remain at the study site in their first year of life. Like with apparent survival, there was suggestive evidence that detection probability decreased with increasing duckling density in the previous year. Hatching date was weakly negatively related to detection probability, but unrelated to apparent survival, whereas neither vital rate was related to winter ENSO index. Our results are consistent with a process where density-dependent growth rates in the prefledging period carry over to influence fitness in subsequent life-cycle stages. If this pattern generalizes to other systems, this density COE may have important implications for our understanding of duck population dynamics and reaffirms the importance of maintaining abundant brood-rearing habitats in conservation and management of ducks. © 2021 The Wildlife Society.     

Infection dynamics of Marteilia refringens in flat oyster Ostrea edulis and copepod Paracartia grani in a claire pond of Marennes-Oléron Bay

The protozoan parasite Marteilia refringens has been partly responsible for the severe decrease in the production of the European flat oyster Ostrea edulis Linnaeus in France since the 1970s. The calanoid copepod Paracartia grani Sars was recently found to be a host for M. refringens in French shallow-water oyster ponds ('claires'). This study reconsidered M. refringens transmission dynamics in the light of this finding, taking into account not only oyster infection dynamics and environmental factors but also data concerning the copepod host. P. grani population dynamics in the claire under study revealed that this species is the dominant planktonic copepod in this confined ecosystem. During winter, M. refringens overwintered in O. edulis, with P. grani existing only as resting eggs in the sediment. The increase in temperature in spring controlled and synchronized both the release of M. refringens sporangia in the oyster feces, and the hatching of the benthic resting eggs of the copepod. Infection of oysters by M. refringens was limited to June, July and August, coinciding with (1) the highest temperature recorded in the claire, and (2) the highest abundance of P. grani. PCR detection of M. refringens in P. grani during the summer period was linked to the release of parasite sporangia by the oyster. Our results are supported by previous results on the effective transmission of this parasite from the oyster to the copepod.     

Seasonal abundance, reproduction and development of four key copepod species on the Faroe shelf

The copepod community on the Faroe shelf is dominated by Calanus finmarchicus, Temora longicornis, Acartia longiremis and Pseudocalanus spp. The species composition, abundance and development of the copepod community varied considerably during the season 2004. These variations reflected to a large extent the different life strategies of the copepods. Both nauplii and copepodites of C. finmarchicus were most abundant during spring and early summer. The two neritic copepods T. longicornis and A. longiremis were present in low numbers during spring but dominated the copepod community later during the productive period. Pseudocalanus spp., on the other hand, occurred throughout the year, but showed no clear numerical response in abundance to the spring bloom. The egg production measurements of C. finmarchicus and T. longicornis showed some pre-bloom egg production, but as the spring bloom started the egg production rate increased significantly, especially for C. finmarchicus. There seemed to be a substantial loss of nauplii and copepods from the shelf ecosystem during the productive season. It was, however, not possible to determine whether this was mainly due to mortality or advective loss.     

Intraspecific differentiation of social behavior and shelter selection in Mesobuthus gibbosus (Brullé, 1832) (Scorpiones: Buthidae)

We compared seasonal shelter selection and social behavior of Mesobuthus gibbosus from autumn to mid-summer in two similar phryganic ecosystems, in continental Greece (near Volos city) and in insular Greece (eastern Crete), and in the laboratory under simulated abiotic conditions. Our results showed that shelter selection is a critical indicator of the seasonal social behavior of the species. The abrupt climatic changes in spring caused a differentiation in shelter selection between the cold period (November–February) and the warm period (March–June) at both sites. Sociality was exhibited only during winter in the field and was more extensive under cold conditions in the laboratory. Co-occurrence of scorpions proved to be age-specific, facilitated by population density and by harsh abiotic conditions during winter, and negatively influenced by intraspecific competition, which was higher in continental Greece. The response of scorpions to changes of abiotic factors reveals synchronization of seasonal shelter selection with climatic changes.     

Climate change and spring-fruiting fungi

Most macrofungi produce ephemeral fruit bodies during autumn but some have adapted to spring fruiting. In this study, temporal changes in the time of spring fruiting in Norway and the UK during 1960–2007 have been investigated by statistical analyses of about 6000 herbarium and field records, covering 34 species. Nearly 30 per cent of the temporal variation in fruiting could be ascribed to spatial and species-specific effects. Correcting for these effects, linear trends towards progressively earlier fruiting were detected during the entire period in both Norway and the UK, with a change in average fruiting day of 18 days over the study period. Early fruiting was correlated with high winter temperatures in both countries, indicating that the observed phenological changes are likely due to earlier onset of spring. There were also significant correlations between climatic conditions in one year and timing of fruiting the following year, indicating that below-ground mycelia are influenced by climatic conditions over a longer time period before fruiting. Fruiting dates were, however, not strictly related to changes in vernal accumulated thermal time. Our results indicate that global warming has lead to progressively earlier fruiting of spring fungi in northwest Europe during the last half century.     

Assessing the impact of extreme adverse weather on the biological traits of a European storm petrel colony

Climate change affects the climatic disturbance patterns and regimes and is altering the frequency and intensity of subtropical cyclones. These events can affect population dynamics of seabirds (e.g., survival, reproduction). In this work we tested the effect of adverse weather on a colony of European storm petrels (Hydrobates pelagicus) located in a small islet (Aketx) in northern Spain. Over a long-term monitoring period (1993–2014) we ringed 3728 petrels. From 2003 onwards we also monitored breeding success, the percentage of immature individuals and moult scores. We used Cormack-Jolly-Seber models and Underhill and Zucchini models to analyze the effects of climatic conditions on a number of biological traits (survival, breeding parameters, moulting patterns). Our analyses revealed a constant value of adult survival over the 26-year monitoring period. Recapture probability, however, tended to be positively influenced by NAO conditions in spring, and negatively influenced by NAO conditions in winter (although this would only affect to a fraction of first-captured birds). Moreover, the impact of adverse weather, especially in 2011 and 2014, resulted in an increasing proportion of yearlings in the breeding population, a lower breeding success and a delayed onset of moult. These effects were similar to those observed during the Prestige oil spill catastrophe.     

Earlier Arctic springs cause phenological mismatch in long-distance migrants

An uneven change in climate across the Northern Hemisphere might severely affect the phenology of migrating animals, and especially long-distance migrating birds relying on local climatic cues to regulate the timing of migration. We examine the forward displacement of spring in both staging areas and breeding grounds of one such population, the East Atlantic light-bellied brent goose Branta bernicla hrota, and evaluate to what extent their migration has made a proportional response. On the breeding grounds in Svalbard the onset of spring advanced 2 weeks during the 24-year period, whereas no significant trend was found in the temperate staging areas. The timing of migration was constant throughout the study period, mirroring the static climatic conditions in the spring staging areas. These findings indicate a global warming-induced phenological mismatch in light-bellied brent geese, as these might arrive on their breeding grounds well beyond optimal breeding conditions. Our data indicated that productivity was negatively influenced by phenological delay and positively influenced by prolonged snow cover. We argue that both these effects might be representative of a negative influence of the growing phenological mismatch, because years with later thaw might partly offset the effects of increasingly earlier Svalbard springs. During the study period reproduction fell below annual mortality, and the population declined in recent years. The wider implications of these findings may extend to many migrating species, and highlight the urgent need to clarify how global change may influence cues and the associated timing of important life history activities.     

Late Holocene changes in the humic state of a boreal lake and their associations with organic matter transport and climate dynamics

An important factor in the ontogeny of boreal lakes is the development of their humic state through terrigenous input of organic matter (carbon) that affects strongly the functioning and structure of these ecosystems. The long-term dynamics and role of humic substances for these systems in relation to climate are not clear. In this study, a boreal lake from southern Finland was investigated using paleolimnological methods, including diatom, chironomid and geochemical analyses, for Late Holocene changes in the humic state. The aim was to examine the relationship between sediment biogeochemistry and climate variation. Consistent trends were found in diatom-inferred total lake-water organic carbon (TOC) and in the ratio of humic/oligohumic chironomids. Sediment geochemistry provided further evidence for the limnological development of the lake and related long-term climate trends in the region. The results indicated three distinct phases with differing humic state; the beginning of the record at ca. 4,500 cal year BP was characterized by extremely humic conditions coinciding with warm and dry climatic conditions, a meso-oligohumic period between ca. 3,000–500 cal year BP with increasing allochthonous organic matter transport and cooler and wetter climate, and recent period with polyhumic (TOC >10 mg L^?1) lake status and warming climate. This study shows that instead of straightforward linear development, boreal lakes evolve through dynamic humic stages related to climate and lake-catchment coupling processes. As the changes in the humic state are ultimately climate-driven, the ongoing climate change probably has a major influence on boreal lakes through direct and indirect effects on organic carbon transport, utilization and accumulation.     

Copepod life cycle adaptations and success in response to phytoplankton spring bloom phenology

In a seasonal environment, the timing of reproduction is usually scheduled to maximize the survival of offspring. Within deep water bodies, the phytoplankton spring bloom provides a short time window of high food quantity and quality for herbivores. The onset of algal bloom development, however, varies strongly from year to year due to interannual variability in meteorological conditions. Furthermore, the onset is predicted to change with global warming. Here, we use a long-term dataset to study (a) how a cyclopoid copepod, Cyclops vicinus , is dealing with the large variability in phytoplankton bloom phenology, and (b) if bloom phenology has an influence on offspring numbers. C. vicinus performed a two-phase dormancy, that is, the actual diapause of fourth copepodid stages at the lake bottom is followed by a delay in maturation, that is, a quiescence, within the fifth copepodid stage until the start of the spring bloom. This strategy seems to guarantee a high temporal match of the food requirements for successful offspring development, especially through the highly vulnerable naupliar stages, with the phytoplankton spring bloom. However, despite this match with food availability in all study years, offspring numbers, that is, offspring survival rates were higher in years with an early start of the phytoplankton bloom. In addition, the phenology of copepod development suggested that also within study years, early offspring seems to have lower mortality rates than late produced offspring. We suggest that this is due to a longer predator-free time period and/or reduced time stress for development. Hence, within the present climate variability, the copepod benefited from warmer spring temperatures resulting in an earlier phytoplankton spring bloom. Time will show if the copepod's strategy is flexible enough to cope with future warming.     

Respiratory loss and bulk export of organic matter from cattle dung pats: a field study

Respiratory loss and bulk transport of organic matter from dung pats in a Danish pasture were measured by a chromic oxide marker technique. Measurements covered the period until a dung age of 7-8 weeks. On average, respiration and transport contributed 46% and 54% of organic matter disappearance in three spring experiments: in three autumn experiments the corresponding values were 25% and 75%. Thus, both processes are important. The rate of transport was highest at the bottom of the pat, whereas the highest respiratory rate occurred in the top and periphery. During the first 10–14 days transport predominated, probably owing to the activity of dung insects, whereas respiration was remarkably low. During the remaining period, transport was probably affected mainly by earthworms. Respiration seemed to be mostly microbial and to proceed during dung pat decay in essentially the same way as did cellulolytic activity. Earthworms did not significantly affect the respiration of pats.