RESUMO
Phytoplankton bloom received considerable attention for many decades. Different approaches have been used to explain the bloom phenomena. In this paper, we study a Nutrient-Phytoplankton-Zooplankton (NPZ) model consisting of a periodic driving force in the growth rate of phytoplankton due to solar radiation and analyse the dynamics of the corresponding autonomous and non-autonomous systems in different parametric regions. Then we introduce a novel aspect to extend the model by incorporating another periodic driving force into the growth term of the phytoplankton due to sea surface temperature (SST), a key point of innovation. Temperature dependency of the maximum growth rate (µmax) of the phytoplankton is modelled by the well-known Q10 formulation: [Formula: see text] , where µ0 is maximum growth at 0oC. Stability conditions for all three equilibrium points are expressed in terms of the new parameter ρ2, which appears due to the incorporation of periodic driving forces. System dynamics is explored through a detailed bifurcation analysis, both mathematically and numerically, with respect to the light and temperature dependent phytoplankton growth response. Bloom phenomenon is explained by the saddle point bloom mechanism even when the co-existing equilibrium point does not exist for some values of ρ2. Solar radiation and SST are modelled using sinusoidal functions constructed from satellite data. Our results of the proposed model describe the initiation of the phytoplankton bloom better than an existing model for the region 25-35° W, 40-45° N of the North Atlantic Ocean. An improvement of 14 days (approximately) is observed in the bloom initiation time. The rate of change method (ROC) is applied to predict the bloom initiation.
Assuntos
Modelos Biológicos , Fitoplâncton , Fitoplâncton/crescimento & desenvolvimento , Fitoplâncton/fisiologia , Temperatura , Eutrofização , Animais , Zooplâncton/fisiologia , Zooplâncton/crescimento & desenvolvimento , Luz SolarRESUMO
Decline of the dissolved oxygen in the ocean is a growing concern, as it may eventually lead to global anoxia, an elevated mortality of marine fauna and even a mass extinction. Deoxygenation of the ocean often results in the formation of oxygen minimum zones (OMZ): large domains where the abundance of oxygen is much lower than that in the surrounding ocean environment. Factors and processes resulting in the OMZ formation remain controversial. We consider a conceptual model of coupled plankton-oxygen dynamics that, apart from the plankton growth and the oxygen production by phytoplankton, also accounts for the difference in the timescales for phyto- and zooplankton (making it a "slow-fast system") and for the implicit effect of upper trophic levels resulting in density dependent (nonlinear) zooplankton mortality. The model is investigated using a combination of analytical techniques and numerical simulations. The slow-fast system is decomposed into its slow and fast subsystems. The critical manifold of the slow-fast system and its stability is then studied by analyzing the bifurcation structure of the fast subsystem. We obtain the canard cycles of the slow-fast system for a range of parameter values. However, the system does not allow for persistent relaxation oscillations; instead, the blowup of the canard cycle results in plankton extinction and oxygen depletion. For the spatially explicit model, the earlier works in this direction did not take into account the density dependent mortality rate of the zooplankton, and thus could exhibit Turing pattern. However, the inclusion of the density dependent mortality into the system can lead to stationary Turing patterns. The dynamics of the system is then studied near the Turing bifurcation threshold. We further consider the effect of the self-movement of the zooplankton along with the turbulent mixing. We show that an initial non-uniform perturbation can lead to the formation of an OMZ, which then grows in size and spreads over space. For a sufficiently large timescale separation, the spread of the OMZ can result in global anoxia.
Assuntos
Simulação por Computador , Modelos Biológicos , Oxigênio , Fitoplâncton , Zooplâncton , Animais , Oxigênio/metabolismo , Zooplâncton/metabolismo , Zooplâncton/crescimento & desenvolvimento , Zooplâncton/fisiologia , Fitoplâncton/metabolismo , Fitoplâncton/crescimento & desenvolvimento , Fitoplâncton/fisiologia , Oceanos e Mares , Plâncton/metabolismo , Plâncton/crescimento & desenvolvimento , Conceitos Matemáticos , Ecossistema , Água do Mar/química , Cadeia Alimentar , AnaerobioseRESUMO
Considerable attention is given to absolute nutrient levels in lakes, rivers, and oceans, but less is paid to their relative concentrations, their nitrogen:phosphorus (N:P) stoichiometry, and the consequences of imbalanced stoichiometry. Here, we report 38 y of nutrient dynamics in Flathead Lake, a large oligotrophic lake in Montana, and its inflows. While nutrient levels were low, the lake had sustained high total N: total P ratios (TN:TP: 60 to 90:1 molar) throughout the observation period. N and P loading to the lake as well as loading N:P ratios varied considerably among years but showed no systematic long-term trend. Surprisingly, TN:TP ratios in river inflows were consistently lower than in the lake, suggesting that forms of P in riverine loading are removed preferentially to N. In-lake processes, such as differential sedimentation of P relative to N or accumulation of fixed N in excess of denitrification, likely also operate to maintain the lake's high TN:TP ratios. Regardless of causes, the lake's stoichiometric imbalance is manifested in P limitation of phytoplankton growth during early and midsummer, resulting in high C:P and N:P ratios in suspended particulate matter that propagate P limitation to zooplankton. Finally, the lake's imbalanced N:P stoichiometry appears to raise the potential for aerobic methane production via metabolism of phosphonate compounds by P-limited microbes. These data highlight the importance of not only absolute N and P levels in aquatic ecosystems, but also their stoichiometric balance, and they call attention to potential management implications of high N:P ratios.
Assuntos
Ecossistema , Lagos , Nitrogênio , Fósforo , Fitoplâncton , Zooplâncton , Animais , China , Monitoramento Ambiental , Eutrofização , Lagos/química , Lagos/microbiologia , Metano/biossíntese , Nitrogênio/análise , Nitrogênio/metabolismo , Organofosfonatos/metabolismo , Fósforo/análise , Fósforo/metabolismo , Fitoplâncton/crescimento & desenvolvimento , Fitoplâncton/metabolismo , Zooplâncton/crescimento & desenvolvimento , Zooplâncton/metabolismoRESUMO
Cladocerans are a diverse group of species that show rapid responses to changes in environmental conditions. This adaptive capacity has important implications for egg production and life cycle, especially in transitory environments such as temporary waterbodies. The present study investigated the life history and egg production of Alona gutatta Sars, 1862 (Crustacea, Cladocera), an abundant and frequent species from a high-altitude temporary pond (Lagoa Seca, Minas Gerais, Brazil). Newly hatched neonates were monitored in relation to time of maturation, number of eggs produced per female and time of survival. Neonates required a mean of 8 days to mature. A. guttata survived for a mean of 30.9 ± 8.1 days and produced 2 eggs per brood, generating a mean of 10.95 ± 6.41 neonates during the entire life cycle. The rapid development, short time to produce eggs and long life cycle are important adaptations to the adverse environmental conditions of temporary aquatic environments, which can contribute to the rapid colonization of Alona guttata in transitory ecosystems.
Os cladóceros formam um grupo diverso de espécies que apresentam respostas rápidas às mudanças nas condições ambientais. Essa capacidade adaptativa tem implicações importantes para a produção de ovos e para o ciclo de vida, especialmente em ambientes transitórios, como corpos dágua temporários. O presente estudo investigou a história de vida e a produção de ovos da espécie Alona guttata Sars, 1862 (Crustacea, Cladocera) coletada em uma lagoa temporária de altitude (Minas Gerais, Brasil). Organismos recém eclodidos foram observados (em condições de laboratório) em relação ao tempo de maturação, número de ovos produzidos por fêmea e tempo de sobrevivência. Os neonatos levaram em média 8 dias para atingir o primeiro estágio de maturação. As fêmeas produziram 2 ovos por ninhada e geraram uma média de 10,95 ± 6,41 neonatos durante todo o ciclo de vida. A. guttata apresentou uma média de 30,9 ± 8,1 dias de sobrevivência. O rápido desenvolvimento, o pouco tempo para a produção de ovos e o ciclo de vida longo são adaptações importantes às condições ambientais adversas de ambientes aquáticos temporários, que podem contribuir para a rápida colonização de Alona guttata em ecossistemas transitórios.
Assuntos
Animais , Ambiente Aquático , Artrópodes/crescimento & desenvolvimento , Crustáceos/crescimento & desenvolvimento , Zooplâncton/crescimento & desenvolvimentoRESUMO
Unusually warm conditions recently observed in the Pacific Arctic region included a dramatic loss of sea ice cover and an enhanced inflow of warmer Pacific-derived waters. Moored sediment traps deployed at three biological hotspots of the Distributed Biological Observatory (DBO) during this anomalously warm period collected sinking particles nearly continuously from June 2017 to July 2019 in the northern Bering Sea (DBO2) and in the southern Chukchi Sea (DBO3), and from August 2018 to July 2019 in the northern Chukchi Sea (DBO4). Fluxes of living algal cells, chlorophyll a (chl a), total particulate matter (TPM), particulate organic carbon (POC), and zooplankton fecal pellets, along with zooplankton and meroplankton collected in the traps, were used to evaluate spatial and temporal variations in the development and composition of the phytoplankton and zooplankton communities in relation to sea ice cover and water temperature. The unprecedented sea ice loss of 2018 in the northern Bering Sea led to the export of a large bloom dominated by the exclusively pelagic diatoms Chaetoceros spp. at DBO2. Despite this intense bloom, early sea ice breakup resulted in shorter periods of enhanced chl a and diatom fluxes at all DBO sites, suggesting a weaker biological pump under reduced ice cover in the Pacific Arctic region, while the coincident increase or decrease in TPM and POC fluxes likely reflected variations in resuspension events. Meanwhile, the highest transport of warm Pacific waters during 2017-2018 led to a dominance of the small copepods Pseudocalanus at all sites. Whereas the export of ice-associated diatoms during 2019 suggested a return to more typical conditions in the northern Bering Sea, the impact on copepods persisted under the continuously enhanced transport of warm Pacific waters. Regardless, the biological pump remained strong on the shallow Pacific Arctic shelves.
Assuntos
Ciclo do Carbono , Animais , Regiões Árticas , Clorofila A/análise , Copépodes/crescimento & desenvolvimento , Copépodes/metabolismo , Diatomáceas/crescimento & desenvolvimento , Diatomáceas/metabolismo , Ecossistema , Camada de Gelo , Fitoplâncton/crescimento & desenvolvimento , Fitoplâncton/metabolismo , Temperatura , Zooplâncton/crescimento & desenvolvimento , Zooplâncton/metabolismoRESUMO
The organic carbon produced in the ocean's surface by phytoplankton is either passed through the food web or exported to the ocean interior as marine snow. The rate and efficiency of such vertical export strongly depend on the size, structure and shape of individual particles, but apart from size, other morphological properties are still not quantitatively monitored. With the growing number of in situ imaging technologies, there is now a great possibility to analyze the morphology of individual marine snow. Thus, automated methods for their classification are urgently needed. Consequently, here we present a simple, objective categorization method of marine snow into a few ecologically meaningful functional morphotypes using field data from successive phases of the Arctic phytoplankton bloom. The proposed approach is a promising tool for future studies aiming to integrate the diversity, composition and morphology of marine snow into our understanding of the biological carbon pump.
Assuntos
Sedimentos Geológicos/química , Fitoplâncton/crescimento & desenvolvimento , Fitoplâncton/metabolismo , Animais , Regiões Árticas , Ciclo do Carbono , Ecossistema , Eutrofização , Cadeia Alimentar , Oceanos e Mares , Tamanho da Partícula , Água do Mar/química , Análise Espaço-Temporal , Zooplâncton/crescimento & desenvolvimento , Zooplâncton/metabolismoRESUMO
Zooplankton community inventories are the basis of fisheries management for containing fish larvae and their preys; however, the visual identification of early-stage larvae (the "missing biomass") is difficult and laborious. Here, eDNA metabarcoding was employed to detect zooplankton species of interest for fisheries from open and coastal waters. High-Throughput sequencing (HTS) from environmental samples using small water volumes has been proposed to detect species of interest whose DNA is the most abundant. We analyzed 6-L water samples taken from subtropical and tropical waters using Cytochrome oxidase I (COI) gene as metabarcode. In the open ocean, several commercial fish larvae and invertebrate species important in fish diet were found from metabarcodes and confirmed from individual barcoding. Comparing Atlantic, Mediterranean, Red Sea, and Pacific samples we found a lower taxonomic depth of OTU assignments in samples from tropical waters than in those from temperate ones, suggesting large gaps in reference databases for those areas; thus a higher effort of zooplankton barcoding in tropical oceans is highly recommended. This and similar simplified sampling protocols could be applied in early detection of species important for fisheries.
Assuntos
Biodiversidade , Biomassa , Código de Barras de DNA Taxonômico , Cadeia Alimentar , Sequenciamento de Nucleotídeos em Larga Escala , Zooplâncton/genética , Animais , Monitoramento Ambiental , Oceanos e Mares , Zooplâncton/classificação , Zooplâncton/crescimento & desenvolvimentoRESUMO
We investigated changes in the species richness, abundance, and composition of the zooplankton community in response to the formation of a small reservoir in the Caveiras River, southern Brazil. Zooplankton were collected using a motor-pump and aplankton net (68 μm mesh), with 600 L of water filtered per sample. Sampling occurred during the pre-(April, August, and December 2011) and post-impoundment (July and October 2013, and January 2014) phases of the Caveiras River. We identified 86 taxa in this study, and rotifers were the predominant group. The species richness and abundance of the zooplankton increased after the filling of the reservoir. Furthermore, the zooplankton community showed a clear change in the species composition between the phases before and after the formation of the reservoir, with the emergence of typical planktonic species. Changes in the structure of the zooplankton community were related to changes in limnological characteristics due to the impoundment of the river, mainlyin the availability of food and in the concentration of nutrients.
Assuntos
Reservatórios de Água , Zooplâncton/classificação , Zooplâncton/crescimento & desenvolvimentoRESUMO
The biological pump transports organic carbon produced by photosynthesis to the meso- and bathypelagic zones, the latter removing carbon from exchanging with the atmosphere over centennial time scales. Organisms living in both zones are supported by a passive flux of particles, and carbon transported to the deep-sea through vertical zooplankton migrations. Here we report globally-coherent positive relationships between zooplankton biomass in the epi-, meso-, and bathypelagic layers and average net primary production (NPP). We do so based on a global assessment of available deep-sea zooplankton biomass data and large-scale estimates of average NPP. The relationships obtained imply that increased NPP leads to enhanced transference of organic carbon to the deep ocean. Estimated remineralization from respiration rates by deep-sea zooplankton requires a minimum supply of 0.44 Pg C y-1 transported into the bathypelagic ocean, comparable to the passive carbon sequestration. We suggest that the global coupling between NPP and bathypelagic zooplankton biomass must be also supported by an active transport mechanism associated to vertical zooplankton migration.
Assuntos
Biomassa , Oceanos e Mares , Zooplâncton/crescimento & desenvolvimento , Acústica , Animais , Carbono/química , Marcação por Isótopo , Minerais/químicaRESUMO
Regime shifts are increasingly prevalent in the ecological literature. However, definitions vary and detection methods are still developing. Here, we employ a novel statistical algorithm based on the Bayesian online change-point detection framework to simultaneously identify shifts in the mean and (or) variance of time series data. We detected multiple regime shifts in long-term (59-154 years) patterns of coastal Norwegian Atlantic cod (>70% decline) and putative drivers of cod productivity: North Atlantic Oscillation (NAO); sea-surface temperature; zooplankton abundance; fishing mortality (F). The consequences of an environmental or climate-related regime shift on cod productivity are accentuated when regime shifts coincide, fishing mortality is high, and populations are small. The analyses suggest that increasing F increasingly sensitized cod in the mid 1970s and late 1990s to regime shifts in NAO, zooplankton abundance, and water temperature. Our work underscores the necessity of accounting for human-induced mortality in regime shift analyses of marine ecosystems.
Assuntos
Gadus morhua/crescimento & desenvolvimento , Animais , Oceano Atlântico , Teorema de Bayes , Clima , Mudança Climática , Ecossistema , Dinâmica Populacional , Temperatura , Zooplâncton/crescimento & desenvolvimentoRESUMO
While flow is known to be a major driver of estuarine ecosystems, targeted flow manipulations are rare because tidal systems are extremely variable in space and time, and because the necessary infrastructure is rarely available. In summer 2018 we used a unique water control structure in the San Francisco Estuary (SFE) to direct a managed flow pulse into Suisun Marsh, one of the largest contiguous tidal marshes on the west coast of the United States. The action was designed to increase habitat suitability for the endangered Delta Smelt Hypomesus transpacificus, a small osmerid fish endemic to the upper SFE. The approach was to operate the Suisun Marsh Salinity Control Gates (SMSCG) in conjunction with increased Sacramento River tributary inflow to direct an estimated 160 x 106 m3 pulse of low salinity water into Suisun Marsh during August, a critical time period for juvenile Delta Smelt rearing. Three-dimensional modeling showed that directing additional low salinity water into Suisun Marsh ("Flow Action") substantially increased the area of low salinity habitat for Delta Smelt that persisted beyond the period of SMSCG operations. Field monitoring showed that turbidity and chlorophyll were at higher levels in Suisun Marsh, representing better habitat conditions, than the upstream Sacramento River region throughout the study period. The Flow Action had no substantial effects on zooplankton abundance, nor did Suisun Marsh show enhanced levels of these prey species in comparison to the Sacramento River. Fish monitoring data suggested that small numbers of Delta Smelt colonized Suisun Marsh from the Sacramento River during the 2018 Flow Action. Comparison of the salinity effects of the Flow Action to historical catch data for Suisun Marsh further supported our hypothesis that the Flow Action would have some benefit for this rare species. Our study provides insight into both the potential use of targeted flow manipulations to support endangered fishes such as Delta Smelt, and into the general response of estuarine habitat to flow management.
Assuntos
Monitorização de Parâmetros Ecológicos , Estuários , Osmeriformes , Animais , Ecossistema , Espécies em Perigo de Extinção , Microcystis/crescimento & desenvolvimento , Osmeriformes/crescimento & desenvolvimento , Rios , Salinidade , São Francisco , Áreas Alagadas , Zooplâncton/crescimento & desenvolvimentoRESUMO
Climate changes in the Arctic may weaken the currently tight pelagic-benthic coupling. In response to decreasing sea ice cover, arctic marine systems are expected to shift from a 'sea-ice algae-benthos' to a 'phytoplankton-zooplankton' dominance. We used mollusc shells as bioarchives and fatty acid trophic markers to estimate the effects of the reduction of sea ice cover on the food exported to the seafloor. Bathyal bivalve Astarte moerchi living at 600 m depth in northern Baffin Bay reveals a clear shift in growth variations and Ba/Ca ratios since the late 1970s, which we relate to a change in food availability. Tissue fatty acid compositions show that this species feeds mainly on microalgae exported from the euphotic zone to the seabed. We, therefore, suggest that changes in pelagic-benthic coupling are likely due either to local changes in sea ice dynamics, mediated through bottom-up regulation exerted by sea ice on phytoplankton production, or to a mismatch between phytoplankton bloom and zooplankton grazing due to phenological change. Both possibilities allow a more regular and increased transfer of food to the seabed. This article is part of the theme issue 'The changing Arctic Ocean: consequences for biological communities, biogeochemical processes and ecosystem functioning'.
Assuntos
Exoesqueleto/anatomia & histologia , Bivalves/anatomia & histologia , Ecossistema , Exoesqueleto/química , Exoesqueleto/crescimento & desenvolvimento , Animais , Regiões Árticas , Bário/análise , Bivalves/química , Bivalves/crescimento & desenvolvimento , Cálcio/análise , Mudança Climática/história , Ácidos Graxos/análise , Cadeia Alimentar , História do Século XX , História do Século XXI , Camada de Gelo , Fitoplâncton/crescimento & desenvolvimento , Datação Radiométrica , Estações do Ano , Zooplâncton/crescimento & desenvolvimentoRESUMO
Magnesium (Mg) is a mining-related contaminant in the Alligators Rivers Region of tropical northern Australia. A mesocosm experiment was used to assess Mg toxicity to aquatic freshwater assemblages. Twenty-five 2700-L tubs were arranged, stratified randomly, on the bed of Magela Creek, a seasonally flowing, sandy stream channel in the Alligator Rivers Region of northern Australia. The experiment comprised 5 replicates of 4 nominal Mg treatments, 2.5, 7.5, 23, and 68 mg L-1 , and a control. Phytoplankton biomass, and diatom, zooplankton, and macroinvertebrate assemblages present in the treatment tubs were sampled before and after Mg addition. A significant negative relationship between phytoplankton biomass and Mg was observed 4 wk after Mg addition as measured by chlorophyll a concentrations (r2 = 0.97, p = 0.01). This result was supported by reductions in some major phytoplankton groups in response to increasing Mg concentrations, in the same experiment and from independent field studies. There was a significant negative relationship between zooplankton assemblage similarity (to control) and Mg concentrations (r2 = 0.96, p = 0.002). Seven weeks after Mg addition, macroinvertebrate assemblages were dominated by 3 microcrustacean groups (Ostracoda, Cladocera, and Copepoda), each reaching maximum abundance at intermediate Mg concentrations (i.e., unimodal responses). The responses of phytoplankton and zooplankton were used to derive assemblage effect concentrations (Mg concentrations resulting in x% of the assemblage change [ECx]). Magnesium concentrations resulting in assemblage EC01 values were <3 mg L-1 . Together with candidate guideline values from other laboratory- and field-based lines of evidence, the mesocosm EC01 values were incorporated into a weight-of-evidence framework for a robust regulatory approach to environmental protection. Environ Toxicol Chem 2020;39:1973-1987. © 2020 Commonwealth of Australia. Published by Wiley Periodicals LLC on behalf of SETAC.
Assuntos
Crustáceos/crescimento & desenvolvimento , Magnésio/toxicidade , Fitoplâncton/crescimento & desenvolvimento , Rios/química , Poluentes Químicos da Água/toxicidade , Zooplâncton/crescimento & desenvolvimento , Animais , Austrália , Biomassa , Clorofila A/análise , Cladocera/crescimento & desenvolvimento , Copépodes/crescimento & desenvolvimento , Diatomáceas/crescimento & desenvolvimento , Relação Dose-Resposta a Droga , Magnésio/análise , Modelos Teóricos , Especificidade da Espécie , Poluentes Químicos da Água/análiseRESUMO
Sediments from stratified marine environments often show an enhanced preservation of organic matter (OM) which is attributed to the limitation, or absence, of oxygen in the bottom waters and surface sediments. Yet there is still a limited knowledge about the changes that the associated biomarker signals undergo in the different parts of a stratified environment, and as to which extent the situation in the productive upper parts of the water column is eventually reflected in the sedimentary record. To better understand these processes we studied particulate matter samples from the stratified, partly anoxic Eastern Gotland Basin (EGB, Central Baltic Sea) during a strong cyanobacterial bloom in August 2016. Endmember samples representing the main biomass producers within the phytoplankton (cyanobacteria) and mesozooplankton (copepods) were obtained from different levels of the water column. Major extractable lipids (fatty acids, n-alcohols, sterols, and selected hydrocarbons) were analysed from the same materials and compared to samples cored from the underlying surface sediments (0-12 cm). Given the annually recurring phenomenon of cyanobacterial blooms we anticipated to find a considerable lipid footprint of the major primary producers in the sedimentary record of the EGB. Unexpectedly, however, lipids in the surface sediments largely derived from the storage lipids (mainly wax esters) of the copepod Pseudocalanus spp. which thrived in deeper, more saline and oxygen-depleted waters. Carbon number and unsaturation patterns suggest that the component n-alcohols of these wax esters are transformed into the corresponding n-fatty acids prior to further degradation in the sediment. In the EGB deposits, most of the plankton-derived lipids studied appear to be degraded on a time scale of decades. In terms of relative abundances, long-chain n-alkyl lipids and C29 sterols from terrestrial plant sources instead become predominant in the deeper sediment layers. Likewise, higher stanol/sterol ratios of C27-sterols vs. C29-sterols indicate a more intense biodegradation of planktonic OM as compared to terrestrial OM. Our observations indicate that primary produced particulate OM is heavily modified by mesozooplankton grazing. This overprint adds on the influence of heterotrophic microorganisms and, in the sediment, preferential preservation of terrestrial biomarkers. Taken together, these factors result in a major decoupling of the biomarker signals between the productive upper mixed layer and the oxygen-depleted bottom waters and sediments of the EGB.
Assuntos
Biomarcadores/análise , Sedimentos Geológicos/análise , Lipídeos/análise , Zooplâncton/metabolismo , Animais , Países Bálticos , Copépodes/crescimento & desenvolvimento , Copépodes/metabolismo , Cianobactérias/crescimento & desenvolvimento , Cianobactérias/metabolismo , Ácidos Graxos/análise , Cromatografia Gasosa-Espectrometria de Massas , Hidrocarbonetos/análise , Esteróis/análise , Poluentes Químicos da Água/análise , Zooplâncton/crescimento & desenvolvimentoRESUMO
Global climate change affects marine species including phytoplankton, which constitute the base of the marine food web, by changing the primary productivity. Global warming affects the ocean surface temperature, in turn leading to a change in the oxygen production of phytoplankton. In this work, the fractional oxygen-phytoplankton-zooplankton mathematical model is considered by the Caputo fractional operator. The production rate of photosynthesis is determined by a temperature function. The model is, therefore, based on the idea that the rate of photosynthesis changes due to the impact of global warming, while phytoplankton oxygen production increases and decreases. We analyze the model with the Caputo fractional derivative differently from the classical case of the model and we compare the results with the integer order derivative when α tends to 1. Existence and uniqueness properties of the oxygen-plankton model have been proved by means of a local Lipschitz condition. It was shown that the species are more sustainable than its corresponding classical case in the Caputo model. Our results show that the effect of global warming on the oxygen production rate has been observed to be quite severe, resulting in oxygen depletion and plankton extinction.
Assuntos
Mudança Climática , Modelos Biológicos , Consumo de Oxigênio , Fitoplâncton/crescimento & desenvolvimento , Zooplâncton/crescimento & desenvolvimento , AnimaisRESUMO
Water from mining drainage is turbid because of suspensions. We tested the hypothesis that the chemical composition as well as shape and size of particles in suspensions of natural origin affect the density and functional diversity of zooplankton. The suspensions were analyzed with atomic force microscopy (AFM), energy dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and optical microscopy. Elements found in the beidellite clays were also identified in the mineral structure of the particles. As the size of the microparticles decreased, the weight proportions of phosphorus, sulfur, and chlorine increased in the suspensions. These conditions facilitated the biomass growth of large and small microphages and raptorials. As the size of the nanoparticles decreased, the shares of silicon, aluminum, iron, and magnesium increased. These conditions inhibited raptorials the most. Ecosystem functionality was the highest with intermediate suspension parameters, which were at the lower range of the microphase and the upper range of the nanophase. The functional traits of zooplankton demonstrate their potential for use as sensitive indicators of disruptions in aquatic ecosystems that are linked with the presence of suspensions, and they facilitate gaining an understanding of the causes and scales of the impact of suspensions.
Assuntos
Biodiversidade , Águas Residuárias/química , Zooplâncton/classificação , Animais , Argila/química , Microscopia Eletrônica de Varredura , Mineração , Espectrometria por Raios X , Zooplâncton/crescimento & desenvolvimentoRESUMO
Secondary production in freshwater zooplankton is frequently limited by the food quality of phytoplankton. One important parameter of phytoplankton food quality are essential polyunsaturated fatty acids (PUFAs). Since the fatty acid composition of phytoplankton is variable and depends on the algae's nutrient supply status, inorganic nutrient supply may affect the algal PUFA composition. Therefore, an indirect transfer of the effects of nutrient availability on zooplankton by changes in algal PUFA composition is conceivable. While the phosphorus (P) supply in lakes is largely decreasing, nitrogen (N) inputs continue to increase. This paper presents data from a mesocosm field experiment in which we exposed phytoplankton communities to increasing N enrichment. As a consequence, the PUFA composition of the phytoplankton community changed. With increasing nitrogen fertilisation, we observed lower quantities of essential PUFAs, together with a decrease in the abundances of the dominant herbivorous zooplankton Daphnia sp. Their biomass was significantly correlated with phytoplankton PUFA content (C18:3 ω3, C20:5 ω3, C18:2 ω6). Our data therefore indicate that changes in nitrogen supply, together with the resultant changes in phytoplankton food quality, can negatively affect the secondary production of herbivorous zooplankton by reducing the availability of essential polyunsaturated fatty acids.
Assuntos
Daphnia/crescimento & desenvolvimento , Ácidos Graxos Insaturados/análise , Nitrogênio/metabolismo , Fitoplâncton/fisiologia , Ração Animal , Animais , Biomassa , Daphnia/efeitos dos fármacos , Ácidos Graxos Insaturados/farmacologia , Cadeia Alimentar , Herbivoria , Fitoplâncton/química , Fitoplâncton/efeitos dos fármacos , Zooplâncton/efeitos dos fármacos , Zooplâncton/crescimento & desenvolvimentoRESUMO
Most, but not all cnidarian species in the class Hydrozoa have a life cycle in which a colonial, asexually reproducing hydroid phase alternates with a free-swimming, sexually reproducing medusa phase. They are not well known, in part because many of them are microscopic, at least in the medusa phase. Matching the two phases has previously required rearing of the organism from one phase to another, which has not often been possible. Here we show that DNA barcoding makes it possible to easily link life-cycle phases without the need for laboratory rearing. Hydrozoan medusae were collected by zooplankton tows in Newport Bay and the Pacific Ocean near Newport Beach, California, and hydroid colonies were collected from solid substrates in the same areas. Specimens were documented by videomicroscopy, preserved in ethanol, and sent to the Canadian Centre for DNA Barcoding at the University of Guelph, Ontario, Canada for sequencing of the COI DNA barcode. In the order Anthoathecata (athecate hydroids), DNA barcoding allowed for the discrimination between the medusae of eight putative species of Bougainvillia, and the hydroid stages were documented for two of these. The medusae of three putative species of Amphinema were identified, and the hydroid stages were identified for two of them. DNA barcodes were obtained from medusae of one species of Cladonema, one adult of the by-the wind Sailor, Velella velella, five putative species of Corymorpha with the matching hydroid phase for one; and Coryne eximia, Turritopsis dohrnii and Turritopsis nutricula with the corresponding hydroid phases. The actinula larvae and hydroid for the pink-hearted hydroid Ectopleura crocea were identified and linked by DNA barcoding. In the order Leptothecata (thecate hydroids) medusae were identified for Clytia elsaeoswaldae, Clytia gracilis and Clytia sp. 701 AC and matched with the hydroid phases for the latter two species. Medusae were matched with the hydroid phases for two species of Obelia (including O. dichotoma) and Eucheilota bakeri. Obelia geniculata was collected as a single hydroid. DNA barcodes were obtained for hydroids of Orthopyxis everta and three other species of Orthopyxis. One member of the family Solmarisidae, representing the order Narcomedusae, and one member (Liriope tetraphylla) of the order Trachymedusae were recognized as medusae. The results show the utility of DNA barcoding for matching life-cycle stages as well as for documenting the diversity of this class of organisms.
Assuntos
Biodiversidade , Código de Barras de DNA Taxonômico , Hidrozoários , Estágios do Ciclo de Vida/fisiologia , Zooplâncton , Animais , Hidrozoários/classificação , Hidrozoários/genética , Hidrozoários/crescimento & desenvolvimento , Microscopia de Vídeo , Oceano Pacífico , Zooplâncton/genética , Zooplâncton/crescimento & desenvolvimentoRESUMO
Zooplankton biomass and water environment factors in Xiaoxingkai Lake were investigated, and the correlation between biomass and water environment factors was performed using the Pearson correlation analysis and redundancy analysis (RDA). The results showed that the highest zooplankton biomass was recorded in summer and the lowest in spring. Water depth, transparency (SD), electric conductivity, and total nitrogen were the highest in spring, while temperature and total phosphorus were the highest in summer. The values of pH and turbidity were the highest in autumn, while chloride ion and chlorophyll a were the highest in winter. During the spring period, Protozoa were positively correlated with conductivity, transparency (SD), and total nitrogen. While Rotifera demonstrated a strong correlation with turbidity, pH, temperature, and total phosphorus in summer and autumn seasons, and Cladocera were correlated with water depth. There were negative correlations of chlorophyll a and chlorine on Copepoda during the winter. RDA results displayed that zooplankton had strong relationships with the physicochemical characteristics in Xiaoxingkai Lake.
Assuntos
Monitoramento Ambiental/métodos , Lagos/química , Zooplâncton/crescimento & desenvolvimento , Animais , Biomassa , China , Clorofila A/metabolismo , Cladocera/crescimento & desenvolvimento , Cladocera/metabolismo , Copépodes/crescimento & desenvolvimento , Copépodes/metabolismo , Nitrogênio/análise , Fósforo/análise , Rotíferos/crescimento & desenvolvimento , Rotíferos/metabolismo , Estações do Ano , Temperatura , Zooplâncton/metabolismoRESUMO
The available observations for the model are usually sparse and uneven. The application of interpolation methods help researchers obtain an approximate form of the original data. A marine nutrient, phytoplankton, zooplankton and detritus (NPZD) type ecosystem model is applied to simulate the distribution of phytoplankton combined with the spline interpolation (SI) and the Cressman interpolation (CI). In the idealized twin experiments, the performance of these two interpolation methods is validated through the analysis of several quantitative metrics, which show the minor error and high efficiency when using the SI. Namely, the given distributions can be better inverted with the SI. The actual distribution of phytoplankton in the Bohai Sea is interpolated in the practical experiment, where a satisfactory simulation result is obtained by the model with the SI. The model experiments and results verify the feasibility and effectiveness of SI.