Suspended particulate matter (seston) in aquatic ecosystems contains two compartments: organisms (plankton) and particles. To know the contribution of particles to the pelagic realm is essential to ...understand the structure and dynamics of aquatic ecosystems. This study aims to determine the relative contribution of particles to the meso-sized seston biomass in plankton samples obtained with common plankton nets (meshes: 200 and 300 μm) comparing wet weight measurements and image analysis using a ZooScan equipment. Samples were obtained in Tamandaré Bay and in the Rio Formoso estuary (Pernambuco, Brazil) during two years (June/2013 to May/2015) at bi-monthly intervals during dry and rainy seasons, totalizing 155 samples. The estuarine environment had the highest values of wet meso-seston biomass, abundance, and volume. In the estuary, the relative contribution of particles in volume units (>55%) was higher than zooplankton. In the bay surrounded by coral reefs, relative particle volume was lower than in the estuary, but still very important (36.86% and 52.15% in the 200 and 300 μm nets, respectively). Zooplankton and particles were more abundant during the dry season. We found significant and positive linear relationships (r2 = 0.68; p < 0.0001), indicating that ZooScan-derived volume data can be confidently used to estimate wet biomass. This study provides a novel approach for the analysis of non-fragile mesoparticles and mesozooplankton in estuarine and marine ecosystems, based on sampling with plankton nets and subsequent analysis with imaging systems. This approach allows new interpretations on the composition of large-sized, robust seston in tropical areas.
Shellfish reefs have been lost from bays and estuaries globally, including in the Swan-Canning Estuary in Western Australia. As part of a national program to restore the ecosystem services that such ...reefs once provided and return this habitat from near extinction, the mussel Mytilus galloprovincialis was selected for a large-scale shellfish reef construction project in this estuary. To assess the potential filtration capacity of the reef, estuary seston quality, mussel feeding behavior, and valve gape activity were quantified in the laboratory and field during winter and summer. In general, estuary water contained high total particulate concentrations (7.9–8.7 mg L−1). Standard clearance rates were greater in winter (1.9 L h−1; 17 °C) than in summer (1.3 L h−1; 25 °C), the latter producing extremely low absorption efficiencies (37%). Mussel valves remained open ~97% and ~50% of the time in winter and summer, respectively. They often displayed erratic behavior in summer, possibly due to elevated temperatures and the toxic microalgae Alexandrium spp. Despite numerous stressors, the reef, at capacity, was estimated to filter 35% of the total volume of the estuary over winter, incorporating 42.7 t of organic matter into mussel tissue. The reefs would thus make a substantial contribution to improving estuary water quality.
Critical research is needed regarding harmful algal blooms threatening ecosystem and human health, especially through respiratory routes. Additional complexity comes from the poorly understood ...factors involved in the physical production of marine aerosols coupled with complex biogeochemical processes at ocean surfaces. Here-by using a marine aerosol generation tank-five bubble-bursting experiments (with contrasting incubation times and, likely, physiological microalgal states) were run to investigate simultaneously the concentrations of the toxins, synthesized by a natural
cf.
bloom, in suspension in the water and in the atmosphere. The first two experiments (EXP1-2) were run with moderate levels of
cf.
cell numbers (ca. 10
cells·L
) and total toxin in suspension (4 × 10
pg·L
) obtained at an early phase of the bloom. After 0.75-4 h incubation, toxin concentration in the aerosols accounted for 49-69 pg·L
. By striking contrast, three experiments (EXP3-5)-conducted with samples collected two weeks later with higher cell abundances and higher toxin concentration in the seston (respectively, about 1 × 10
cells·L
and 2 × 10
pg·L
) and incubated for 21 h-showed about 15-fold lower atmospheric concentrations (3-4 pg·L
), while important foam accumulation was observed in the water surface in the tank. Offline spectroscopic analysis performed by proton-nuclear magnetic resonance spectroscopy showed that the particulate organic carbon in the water was drastically different from that of bubble-bursting aerosols from the tank experiments-suggesting a selective transfer of organic compounds from seawater into the atmosphere. Overall, the results suggest that aerosol production and diffusion of marine toxins in the atmosphere are regulated by complex interactions between biological processes and air-sea aerosol production dynamics.
Abstract
Despite increasing interest in winter limnology, few studies have examined under-ice zooplankton communities and the factors shaping them in different types of temperate lakes. To better ...understand drivers of zooplankton community structure in winter and summer, we sampled 13 lakes across a large trophic status gradient for crustacean zooplankton abundance, taxonomic and functional community composition and C/N stable isotopes. Average winter zooplankton densities were one-third of summer densities across the study lakes. Proportionally, cladocerans were more abundant in summer than winter, with the opposite pattern for calanoids and cyclopoids. In green (eutrophic) lakes, zooplankton densities were higher under the ice than in brown (dystrophic) and blue (oligotrophic) lakes, suggesting better conditions for zooplankton in productive lakes during winter. Overall, zooplankton communities were more similar across lakes under the ice than during the open water season. Feeding group classification showed a decrease in herbivore abundance and an increase in predators from summer to winter. C/N stable isotope results suggested higher lipid content in overwintering zooplankton and potentially increased reliance on the microbial loop by winter zooplankton. Our results show substantial variation in the seasonality of zooplankton communities in different lake types and identify some of the factors responsible for this variation.
To understand the potential risks of dietary metals to marine bivalves, it is important to study the interaction between dietary metal bioaccumulation and bivalve feeding behavior. Key processes in ...affecting the dietary metal influx are the selection of different particles during the ingestion process as well as the differential assimilation of metals during the digestion process. In this study, we quantified the influences of seston quality and quantity on the dietary assimilation of Cd and Zn as well as pre-ingestion particle selectivity in a razor clam Sinonovacula constricta following feeding on radiolabeled diatoms and sediments with different mixtures at four food concentrations. Bioavailability of 109Cd and 65Zn from seston was measured by assimilation efficiency (AE) using a pulse-chase feeding technique. The AEs of Cd and Zn were significantly affected by the seston quantity and quality (higher for Zn than they were for Cd and higher for diatoms than for suspended sediments), but were independent of the presence of other particles during the feeding process. Dual gamma radiotracer technique was further employed to study pre-ingestion particle selectivity. Particle selectivity was weak during pre-ingestion in razor clams, although there was evidence that clams might be able to differentiate particles during the process of pseudofeces production. Our study demonstrated that seston composition and quantity substantially affected the bioavailability of Cd and Zn to the razor clams. The results are important to understand the bioaccumulation of metals in clams living in dynamic food environments of estuary.
Display omitted
•Seston composition and quantity substantially affected the bioavailability of Cd and Zn to the razor clams.•Assimilation of Cd and Zn was independent of the presence of other particles during feeding.•Particle selectivity was weak during the pre-ingestion in razor clams.•Dual radiotracers can be used to study the particle selection in bivalevs.
Organisms at the base of aquatic food webs synthesize essential nutrients, such as omega‐3 polyunsaturated fatty acids (n‐3 PUFA), which are transferred to consumers at higher trophic levels. Many ...consumers, requiring n‐3 long‐chain (LC) PUFA, such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have limited ability to biosynthesize them from the essential dietary precursor α‐linolenic acid (ALA) and thus rely on dietary provision of LC‐PUFA.
We investigated LC‐PUFA metabolism in freshwater zooplankton using stable hydrogen isotopes (δ2H) of fatty acids as tracers. We conducted feeding experiments with the freshwater keystone grazer Daphnia to quantify changes in the δ2H value of body FA in response to the FA composition of their food and the δ2H value of the ambient water.
The isotopic composition of LC‐PUFA changed in Daphnia, depending on the integration of 2H from ambient water during de novo synthesis or bioconversion from dietary precursors, allowing us to distinguish dietary from bioconverted EPA in body tissue. We tested the applicability of these laboratory findings in a field setting by analysing δ2H values of PUFA in primary producers and consumers in eutrophic ponds to track EPA sources of zooplankton.
Multilinear regression models that included conversion of ALA to EPA correlated better with zooplankton δ2HEPA than seston δ2HEPA at low dietary EPA supply.
This study provides evidence that zooplankton can compensate for low dietary EPA supply by activating LC‐PUFA biosynthesis and shows that herbivorous zooplankton play a crucial role in upgrading FA for higher trophic levels during low dietary EPA supply.
A free Plain Language Summary can be found within the Supporting Information of this article.
A free Plain Language Summary can be found within the Supporting Information of this article.
Mercury concentrations in the Laurentian Great Lakes waters are among the lowest reported in the literature, while game fish concentrations approach consumption advisory limits, particularly in Lakes ...Superior, Huron, and Michigan, indicating efficient methylmercury transfer from water to game fish. To determine if increased transfer efficiency is evident within the lower food web, we measured (2010–2018) mercury and dissolved organic carbon (DOC) in water, and in size-sieved seston, dietary tracers (carbon and nitrogen isotope ratios), phytoplankton methylmercury bioaccumulation, and methylmercury biomagnification between increasing seston size fractions. We observed consistently low filter-passing methylmercury (<0.010 ng L–1) and comparatively variable DOC (1.1 to 3.4 mg L–1) concentrations. Methylmercury biomagnification factors between size-sieved seston were similar between lakes. Bioaccumulation factors in phytoplankton were among the highest in the literature (log 5.5 to 6.1), exceeding those in oceans, smaller lakes, and streams, and was influenced by DOC. Higher bioaccumulation rates increase the susceptibility of methylmercury accumulation into the food web. Because mercury is dominantly delivered to the Great Lakes through the atmosphere and the biota therein is highly susceptible to methylmercury uptake, we propose that the Laurentian Great Lakes are excellent sentinels to trace the success of efforts to decrease global mercury emissions (e.g., Minamata Treaty) in the future.
This study is devoted to the distribution of trophic groups of zoobenthos in the Arctic Ocean. The patterns of distribution of detritus feeders, seston feeders, and predators along the bottom of the ...Arctic polar basin are analyzed. The object of the study is the geoecology of the distribution of food groups of benthic animals in the polar regions. The subject of the study is the methods used in assessing the distribution of zoobenthos with different types of nutrition in the polar regions. The results of the work are based on the analysis of the vertical and horizontal structures of the distribution of benthic fauna, reflected in the map of the distribution of trophic groups of zoobenthos and systematized in the distribution table of the leading species of zoobenthos in the Arctic Ocean. To assess the patterns of geoecological distribution of zoobenthos according to the method of feeding, the following were used: actual and cartographic scientific data on the relief, soils, waters, ice cover, maps on the distribution of plankton and the content of organic matter in bottom sediments, as well as data on the trophic characteristics of the benthic fauna of the polar regions, leading biocenoses of the polar regions and geoecological conditions for the existence of benthic fauna in the polar regions. This article presents a map of the distribution of zoobenthos in the Arctic Ocean (according to literary sources), developed by the author, and a table of distribution of guide species of zoobenthos trophic groups in various areas of the Arctic Ocean, compiled by the author based on literary sources. The obtained results of the distribution of food groups of zoobenthos can be used in further detailed assessment of food reserves of bioresources in the polar regions of the World Ocean and their consumption; when designing the economic development of the polar regions; during landscape monitoring.
Abstract
Climate change is already transforming the seascapes of our oceans by changing the energy availability and the metabolic rates of the organisms. Among the ecosystem-engineering species that ...structure the seascape, marine animal forests (MAFs) are the most widespread. These habitats, mainly composed of suspension feeding organisms, provide structural complexity to the sea floor, analogous to terrestrial forests. Because primary and secondary productivity is responding to different impacts, in particular to the rapid ongoing environmental changes driven by climate change, this paper presents some directions about what could happen to different MAFs depending on these fast changes. Climate change could modify the resistance or resilience of MAFs, potentially making them more sensitive to impacts from anthropic activities (i.e. fisheries and coastal management), and vice versa, direct impacts may amplify climate change constraints in MAFs. Such changes will have knock-on effects on the energy budgets of active and passive suspension feeding organisms, as well as on their phenology, larval nutritional condition, and population viability. How the future seascape will be shaped by the new energy fluxes is a crucial question that has to be urgently addressed to mitigate and adapt to the diverse impacts on natural systems.
Spatial and temporal zooplankton feeding dynamics across the water column of lakes are key for understanding site-specific acquisition of diet sources. During this 6-week lake study, we examined ...stable carbon (δ
13
C) and nitrogen (δ
15
N) isotopes and conducted compound-specific fatty acid (FA) stable isotope analysis (CSIA) of edible seston in the epi-, meta-, and hypolimnion, and zooplankton of Lake Lunz, Austria. We predicted that CSIA of essential FA can discern the foraging grounds of zooplankton more accurately than the commonly used bulk stable isotopes. The δ
13
C and δ
15
N values of seston from different lake strata were similar, whereas a dual CSIA approach using stable carbon and hydrogen isotopes of FA (δ
13
C
FA
and δ
2
H
FA
) provided sufficient isotopic difference in essential FA to discern different lake strata-specific diet sources throughout the study period. We present a CSIA model that suggests strata-specific foraging grounds for different zooplankton groups, indicating higher preference of cladocerans for feeding on epilimnetic diet sources, while calanoid copepods retained more hypolimnetic resources. The CSIA approach thus yields strata-specific information on foraging strategies of different zooplankton taxa and provides more details on the spatial and temporal trophodynamics of planktonic food webs than commonly used bulk stable isotopes.
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