Gut fluorescence technique to quantify pigment feeding in Downs herring larvae

Denis, Jérémy; Vincent, Dorothée; Antajan, Elvire; Vallet, Carole; Mestre, Julie; Lefebvre, Valérie; Caboche, Josselin; Cordier, Rémy; Marchal, Paul; Loots, Christophe

doi:10.3354/meps12775

Cited by 3 publications

(2 citation statements)

References 84 publications

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“…As an alternative, ingestion rates were estimated from the gut fluorescent content method (Mackas and Bohrer, 1976) which is often performed at laboratory or in situ to estimate zooplankton herbivory. It constitutes a fast and easy method to set up that could be carried out on a variety of planktonic (copepods, salps, and krill; Pakhomov et al, 1996;Perissinotto and Pakhomov, 1998;Lópes et al, 2007), pelagic (herring larvae, Denis et al, 2018), and benthic organisms (Díaz et al, 2012;Gaonkar and Anil, 2012). Although potential issues exist regarding gut pigments destruction ; Durbin and Campbell, 2007) and gut evacuation rate estimates , the method appeared well suited to quantify aggregate ingestion by copepods, using total chlorophyllian pigments as a proxy of prey biomass.…”

Section: Methodological Considerationsmentioning

confidence: 99%

Copepod Grazing Influences Diatom Aggregation and Particle Dynamics

et al. 2019

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In marine ecosystems, carbon export is driven by particle flux which is modulated by aggregation, remineralization, and grazing processes. Zooplankton contribute to the sinking flux through the egestion of fast sinking fecal pellets but may also attenuate the flux by tearing apart phytoplankton aggregates into small pieces through swimming activity or direct ingestion. Freely suspended cells, artificial monospecific aggregates from two different diatom species (Chaetoceros neogracile and Skeletonema marinoi) and natural aggregates of Melosira sp. were independently incubated with five different copepod species (Acartia clausi, Temora longicornis, Calanus helgolandicus, Euterpina acutifrons, and Calanus hyperboreus). During the grazing experiments initiated with free diatoms, E. acutifrons feeding activity evidenced by ingestion rates of 157 ± 155 ng Chl a ind −1 d −1 , induced a significant increase of S. marinoi aggregation. Transparent exopolymeric particles (TEP) production was only slightly boosted by the presence of grazers and turbulences created by swimming may be the main trigger of the aggregation processes. All copepods studied were able to graze on aggregates and quantitative estimates led to chlorophyll a ingestion rates (expressed in Chla a equivalent, i.e., the sum of chlorophyll a and pheopigments in their guts) ranging from 4 to 23 ng Chl a eq ind −1 d −1 . The relation between equivalent spherical diameters (ESDs) and sinking velocities of the aggregates did not significantly change after grazing, suggesting that copepod grazing did not affect aggregate density as also shown by Si:C and C:N ratios. Three main trends in particle dynamics could be identified and further linked to the copepod feeding behavior and the size ratio between prey and predators:(1) Fragmentation of S. marinoi aggregates by the cruise feeder T. longicornis and of Melosira sp. aggregates by C. hyperboreus at prey to predator size ratios larger than 15; (2) no change of particle dynamics in the presence of the detritic cruise feeder E. acutifrons; and finally (3) re-aggregation of C. neogracile and S. marinoi aggregates when the two filter feeders A. clausi and C. helgolandicus were grazing on aggregate at prey to predator size ratios lower than 10. Aggregation of freely suspended cells or small aggregates was facilitated by turbulence resulting from active swimming of small copepods. However, stronger turbulence created by larger cruise feeders copepods prevent aggregate formation and even made them vulnerable to breakage.

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Section: Methodological Considerationsmentioning

confidence: 99%

Copepod Grazing Influences Diatom Aggregation and Particle Dynamics

et al. 2019

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“…copepod nauplii (Checkley, 1982). But, recent publications also point to microplankton such as ciliates and dinoflagellates, and even larger phytoplankton as important prey items (Denis et al, 2018;Illing et al, 2018). In our experiment, the critical period for herring larvae related to phase III (2 -25 DPH), where combined abundances/biomass of these potential prey organisms did not display sufficient treatment differences to explain higher fish larval survival under high pCO 2 , despite concentrations on the lower end of the ideal prey density of C. harengus (e.g.…”

Section: Possible Bottom-up Factorsmentioning

confidence: 99%

Ocean Acidification Alters the Predator – Prey Relationship Between Hydrozoa and Fish Larvae

et al. 2022

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Anthropogenic CO2 emissions cause a drop in seawater pH and shift the inorganic carbon speciation. Collectively, the term ocean acidification (OA) summarizes these changes. Few studies have examined OA effects on predatory plankton, e.g. Hydrozoa and fish larvae as well as their interaction in complex natural communities. Because Hydrozoa can seriously compete with and prey on other higher-level predators such as fish, changes in their abundances may have significant consequences for marine food webs and ecosystem services. To investigate the interaction between Hydrozoa and fish larvae influenced by OA, we enclosed a natural plankton community in Raunefjord, Norway, for 53 days in eight ≈ 58 m³ pelagic mesocosms. CO2 levels in four mesocosms were increased to ≈ 2000 µatm pCO2, whereas the other four served as untreated controls. We studied OA-induced changes at the top of the food web by following ≈2000 larvae of Atlantic herring (Clupea harengus) hatched inside each mesocosm during the first week of the experiment, and a Hydrozoa population that had already established inside the mesocosms. Under OA, we detected 20% higher abundance of hydromedusae staged jellyfish, but 25% lower biomass. At the same time, survival rates of Atlantic herring larvae were higher under OA (control pCO2: 0.1%, high pCO2: 1.7%) in the final phase of the study. These results indicate that a decrease in predation pressure shortly after hatch likely shaped higher herring larvae survival, when hydromedusae abundance was lower in the OA treatment compared to control conditions. We conclude that indirect food-web mediated OA effects drove the observed changes in the Hydrozoa – fish relationship, based on significant changes in the phyto-, micro-, and mesoplankton community under high pCO2. Ultimately, the observed immediate consequences of these changes for fish larvae survival and the balance of the Hydrozoa – fish larvae predator – prey relationship has important implications for the functioning of oceanic food webs.

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Insights into planktonic food-web dynamics through the lens of size and season

Giraldo,

Cresson,

MacKenzie

et al. 2024

Sci Rep

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Knowledge of the trophic structure and variability of planktonic communities is a key factor in understanding food-web dynamics and energy transfer from zooplankton to higher trophic levels. In this study, we investigated how stable isotopes of mesozooplankton species varied seasonally (winter, spring, autumn) in relation to environmental factors and plankton size classes in a temperate coastal ecosystem. Our results showed that spring is characterized by the strongest vertical and size-structured plankton food-web, mainly fueled by the phytoplankton bloom. As a result, spring displayed the largest isotopic niche space and trophic divergence among species. On the contrary, both pelagic and benthic-derived carbon influenced low productive seasons (winter and autumn), resulting in more generalist strategies (trophic redundancy). Stable isotope mixing models were used to explore how different seasonal structures influenced the overall food web up to predatory plankton (i.e., mysids, chaetognaths, and fish larvae). Different feeding strategies were found in spring, with predators having either a clear preference for larger prey items (> 1 mm, for herring and dab larvae) or a more generalist diet (sprat and dragonets larvae). During low productive seasons, predators seemed to be more opportunistic, feeding on a wide range of size classes but focusing on smaller prey. Overall, the food-web architecture of plankton displayed different seasonal patterns linked to components at the base of the food web that shaped the main energy fluxes, either from phytoplankton or recycled material. Additionally, these patterns extended to carnivorous plankton, such as fish larvae, emphasizing the importance of bottom-up processes.

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Gut fluorescence technique to quantify pigment feeding in Downs herring larvae

Cited by 3 publications

References 84 publications

Copepod Grazing Influences Diatom Aggregation and Particle Dynamics

Copepod Grazing Influences Diatom Aggregation and Particle Dynamics

Ocean Acidification Alters the Predator – Prey Relationship Between Hydrozoa and Fish Larvae

Insights into planktonic food-web dynamics through the lens of size and season

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