Low Prey Concentrations Research Articles

Temperature and prey density drive growth and otolith formation of the world's most valuable fish stock

Peruvian anchovy (Engraulis ringens) represents the largest single-species fishery worldwide. Knowledge on how temperature and prey availability influences growth and age estimation during marine fish early life stages is critical for predicting bottom-up processes impacting stock productivity under changing environmental conditions. We reared Peruvian anchovy larvae at two temperatures (14.5 and 18.5 °C) and prey concentrations [high (HF), and low (LF)] from 6 to 30 days post-hatch (dph) to measure growth rate and examine daily deposition of otolith increments. Peruvian anchovy larvae grew faster at 18.5 °C compared to 14.5 °C. Larvae reared at low prey concentration (18.5-LF) and low temperature (14.5-HF) grew 61 and 35% slower, respectively, than those at high prey and warm temperature (18.5-HF). Age and growth rates of larvae were well depicted in the otolith microstructure of well-fed larvae at 18.5 °C. However, larvae reared at 18.5-LF or 14.5-HF, had only 55 and 49% of the expected number of daily otolith increments. Our results suggest caution when attempting to explore how ocean processes regulate small pelagic stocks, the productivity of which are largely driven by changes in the survival and growth of young larvae.

COMBINED IMPACT OF CANNIBALISM AND ALLEE EFFECT ON THE DYNAMICS OF A PREY–PREDATOR MODEL

In ecological environment, Allee effect is one of the important factors which cause significant changes to the system dynamics. In this paper, using the theory of dynamical systems, we analyze a variation of a standard cannibalistic two-dimensional prey–predator model with Holling type-II functional response in the presence of both weak and strong Allee effects. We have analyzed the impact of strong and weak Allee effects on the dynamics of a cannibalistic system, knowing the dynamics of the cannibalistic model without Allee effect. We have deduced that in the presence of cannibalism, both strong and weak Allee effects generate bistability between equilibrium points. For strong Allee effect, bistability occurs between trivial equilibrium point and predator-free equilibrium point as well as between trivial and coexistence equilibrium points. But for weak Allee effect, bistability occurs only between coexistence equilibrium points. We also pointed out that the cannibalistic system without Allee effect exhibits tristability among the trivial equilibrium point, coexistence equilibrium point having low prey concentration and coexistence equilibrium point having comparatively high prey concentration. But in the presence of strong Allee effect, cannibalistic system experiences tristability among trivial and two other stable coexistence equilibrium points. By a comprehensive bifurcation analysis, we have observed that Allee effect enriches both the local and global dynamics of the system. Here, we have reported all possible codimension-one and codimension-two bifurcations extensively by choosing cannibalism, Allee effect and predator natural death rate as the bifurcation parameters. In the analysis of bifurcations, we have explored the existence of transcritical bifurcation, saddle-node bifurcation, Hopf bifurcation, Bogdanov–Takens bifurcation and Bautin bifurcation. Our analytical findings are validated through exhaustive numerical simulations. Finally, we have reported a comparative study between the impacts of strong and weak Allee effects on the dynamics of the cannibalistic system.

Optimizing intensive culture protocols for Atlantic cod (Gadus morhua) larvae

Larval cod require live prey as food, and prey concentration (PC) and feeding frequency (FF) often affect their growth and survival. Apart from this, water exchange rates/water flow (WER/WF) and water current (WC) also affect the prey resident time in the tank and larval/early juvenile behaviour, respectively. High water current is also known to induce stress in finfish larvae, and this stress response is believed to be dependent on larval developmental stage. Thus, we conducted a study to evaluate three larval rearing protocols varying in prey concentration, feeding frequency, and water current/exchange rate. Three protocols were used: low prey concentration (PC), low feeding frequency (FF), and low water flow (protocol 1); medium PC, medium FF, and medium WF (protocol 2); and high PC, high FF, and high WF (protocol 3) (see Table 1). Larvae were sampled periodically for growth and cortisol measurements. Cortisol extraction and radioimmunoassay (RIA) were conducted using methods previously validated for cod larvae. Larvae reared using protocols 2 and 3 were significantly bigger and heavier than larvae reared using protocol 1. Rearing protocol had a significant effect on the cortisol level in larval cod. Larvae showed a developmental stage-dependent stress response. Protocol 2 had significantly higher survival than protocols 1 and 3. Our results indicate that an intermediate PC, FF, and WF (protocol 2) is suitable during cod larval rearing.

A three dimensional, full life cycle, anchovy and sardine model for the North Aegean Sea (Eastern Mediterranean): Validation, sensitivity and climatic scenario simulations

We present the development of a 3D full-lifecycle, individual-based model (IBM) for anchovy and sardine, online coupled to an existing hydrodynamic/biogeochemical low-trophic level (LTL) model for the North Aegean Sea. It was built upon an existing 1D model for the same species and area, with the addition of a horizontal movement scheme. In the model, both species evolve from the embryonic stage (egg+yolk sac larva) to the larval, juvenile, and adult stages. Somatic growth is simulated with the use of a “Wisconsin” type bioenergetics model and fish populations with an adaptation of the ‘super individuals’ (SI) approach. For the reference simulation and model calibration, in terms of fish growth and population biomass, the 2000-2010 period was selected. Interannual biomass variability of anchovy was successfully represented by the model, while the simulated biomass of sardine exhibited low variability and did not satisfactorily reproduce the observed interannual variability from acoustic surveys. The spatial distribution of both species’ biomass was in relatively good agreement with field data. Additional single-species simulations revealed that species compete for food resources. Temperature sensitivity experiments showed that both species reacted negatively to a temperature increase. Anchovy, in particular, was more affected since its spawning and larval growth periods largely overlap with the period of maximum yearly temperature and low prey concentration. Finally, simulation experiments using IPCC climatic scenarios showed that the predicted temperature increase and zooplankton concentration decrease in the future will negatively affect anchovy, resulting in sardine prevalence.

Non-lethal effects of the predator Meganyctiphanes norvegica and influence of seasonal photoperiod and food availability on the diel feeding behaviour of the copepod Centropages typicus.

Predators can induce changes in the diel activity patterns of marine copepods. Besides vertical migration, diel feeding rhythms have been suggested as an antipredator phenotypic response. We conducted experiments to assess the non-lethal direct effects of the predator Meganyctiphanes norvegica (northern krill) on the diel feeding patterns of the calanoid copepod Centropages typicus. We also analysed the influence of seasonal photoperiod and prey availability on the intensity of copepod feeding rhythms. We did not detect any large effect of krill presence on the diel feeding behaviour of copepods, either in day-night differences or total daily ingestions. Seasonal photoperiod and prey availability, however, significantly affected the magnitude of copepod feeding cycles, with larger diel differences in shorter days and at lower prey concentrations. Therefore, the role of non-lethal direct effects of predators on the diel feeding activity of marine copepods remain debatable and might not be as relevant as in freshwater zooplankton.

Picophytoplankton Synechococcus as food for nauplii of Amphibalanus amphitrite and Artemia salina

The naupliar forms are important intermediaries between microbial and classical food web as they can efficiently graze on autotrophic picophytoplankton and heterotrophic bacteria in diverse aquatic ecosystems. Current knowledge on feeding behavior of the naupliar grazing on picophytoplankton is limited and need to be explored. Nauplii (NII and NIII instar) of Amphibalanus amphitrite and Artemia salina were used as candidate grazer organisms in feeding experiments in the presence of picophytoplankton Synechococcus. Substantial grazing was observed from these two instars, and feeding behavior exhibited typical Holling type III functional response. At low prey concentration, the adapted foraging technique during food acquisition by the nauplii of both grazers pointing toward sigmoid type III is best suited than the other functional response types. However, lower carbon ingestion rate of NIII than NII and survival only up to NIV instar indicate that picophytoplankton are unable to meet the energy requirement for advanced instar stages of both the grazers. These inferences suggest that picophytoplankton occupy a key position in naupliar diet and should be taken into consideration when assessing mesozooplankton grazing and food web dynamics.

Effect of the silica content of diatom prey on the production, decomposition and sinking of fecal pellets of the copepod <i>Calanus sinicus</i>

Abstract. The effects of changing the amount of silica in the cell wall of diatom prey, on the production, decomposition rate and sinking velocity of fecal pellets of the calanoid copepod, Calanus sinicus, were examined. Using different light intensities to control the growth of the diatom Thalassiosira weissflogii also led to the accumulation of different amounts of biogenic silica. Copepods were then fed either low ( ∼ 1600 cells L−1) or high ( ∼ 8000 cells L−1) concentrations of this diatom. Copepods fed a high concentration of diatoms with high-silica content exhibited a lower grazing rate and lower fecal pellet production rate than those fed a high concentration of diatoms with low-silica content. However, there was no difference in either the grazing or fecal pellet production rates at low prey concentrations with high- or low-silica content. The size of the fecal pellets produced was only affected by the prey concentration, and not by the silica content of prey. In addition, the degradation rate of the fecal pellets was much higher for copepods fed a low-silica diet than for those fed a high-silica diet. Significantly lower densities and sinking rates only occurred in the fecal pellets of copepods fed a low-silica diet and a low prey concentration. Calculating the L ratio (the ratio of degradation rate : sinking rate) for each group indicated that the fecal pellets produced by copepods fed highly silicified diatoms are likely to transport both biogenic silica and organic carbon to the deep layer, whereas those produced following the consumption of low-silica diatoms are likely to decompose in the mixing layer.

Reply to comment: Prey perception in feeding‐current feeding copepods

AbstractWe reply to the comments of Paffenhöfer and Jiang () who argues that remote chemical prey perception is necessary for feeding‐current feeding copepods to fulfill their nutritional requirements in a dilute ocean, that remote chemical prey detection may only be observed at very low prey concentrations, and that chemical prey perception is feasible if prey cells release dissolved organic material in short‐lasting but intense bursts. We demonstrate that mechanoreception at a very short range is sufficient to sustain a living, even in a dilute ocean. Further, if chemoreception requires that prey cells have short intense leakage burst, only a very small fraction of prey cells would be available to the copepod at any instance in time and, thus would be inefficient at low prey concentration. Finally, we report a few new observations of prey capture in two species of copepods, Temora longicornis and Centropages hamatus, offered a 45‐μm sized dinoflagellate at very low concentration. The observed short prey detection distances, up to a few prey cell radii, are consistent with mechanoreception and we argue briefly that near‐field mechanoreception is the most likely and common prey perception mechanism in calanoid copepods.

Obligate mixotrophy of the pigmented dinoflagellate Polykrikos lebourae (Dinophyceae, Dinoflagellata)

The marine sand-dwelling dinoflagellate Polykrikos lebourae possesses obvious gold-brown pigmented plastids as well as taeniocyst-nematocyst complex structures. Despite of the presence of the visible plastids, previous attempts to establish this species in culture all failed and thus the unavailability of cultures of this species has posed a major obstacle to further detailed exploration of ecophysiology of the dinoflagellate. Here, we isolated P. lebourae from sandy sediment of an intertidal flat on Korean western coast, successfully established it in culture, and have been maintaining the stock cul ture over the past 3 years. Using this stock culture, we explored phagotrophy and potential prey resources of P. lebourae, growth and grazing responses of P. lebourae to different prey organisms, the effect of prey concentration on growth and grazing rates and gross growth efficiency (GGE) of P. lebourae when fed three different prey organisms, and the growth kinetics of P. lebourae under different light regimes. P. lebourae captured prey cells using a tow filament and then phagocy tized them through the posterior end. The dinoflagellate was capable of ingesting a broad range of prey species varying in size, but not all prey species tested in this study supported its sustained growth. GGE of P. lebourae was extremely high at low prey concentration and moderate or low at high prey concentrations, indicating that P. lebourae grows heterotrophically at high prey concentrations but its growth seems to be more dependent on a certain growth factor or photosynthesis of plastids derived from the prey. In the presence of prey in excess, P. lebourae grew well at moderate light intensity of 40 µmol photons m -2 s -1 , but did not grow at dim and high (10 or 120 µmol photons m -2 s -1 ) light intensities. Our results suggest that the benthic dinoflagellate P. lebourae is an obligate mixotroph, requiring both prey and light for sustained growth and survival.

Effects of prey concentration on ingestion rates of European sardine Sardina pilchardus larvae in the laboratory

The quantification of prey requirements for larval fish is essential to understand how environmental factors act to restrict suitable habitats and recruitment success in marine fish. The effect of prey concentration on ingestion rates of the European sardine Sardina pilchardus was estimated for larvae through 50 d post-hatch (dph) under controlled laboratory conditions at 15°C. Prey were nauplii and copepodites of the calanoid copepod Acartia grani, which were provided to larvae at 3 concentrations (0.5, 2 and 6 nauplii ml −1 and 0.1, 0.5 and 1 copepodites ml −1 ). Larvae were not able to capture copepod nauplii at the beginning of exogenous feeding, suggesting that early larvae depend on smaller prey types and/or less mobile prey than copepods. The mean size of prey found in the guts of sardine larvae increased from 145 to 348 μm for larvae of total length increasing from 6 to 18 mm, respectively. Maximum ingestion rates (232 ± 8.0 μg C larva −1 h −1 ) were reached at the highest prey concentration diet for individuals >40 dph (1500 to 2500 μg C dry weight). These feeding rates are higher than values previously reported for the larvae of small pelagic fish. The inability of sardine larvae to feed at low prey concentrations, particularly during the first weeks of life, suggests that this species relies on and is adapted to forage within dense prey patches. Given this feeding strategy, bottom-up processes causing food limitation may strongly impact the survival and growth of sardine larvae.

On the foraging and feeding ability of Oithona davisae (Crustacea, Copepoda)

The foraging behavior and feeding ability of the cyclopoid copepod Oithona davisae, using the flagellate Tetraselmis tetrathele as prey organism, were observed microscopically and three dimensionally in a flow-cell. The distance between O. davisae and prey was estimated, and prey in front of the antennules or close to the mandible or mouthparts was ingested. Before attacking, O. davisae either sank or jumped. Both these motions are typical of foraging behavior. The instantaneous perceptive sphere was measured from the ingested prey position, while the encounter rate was estimated from the volume of the perceptive sphere, sinking speed, jump frequency plus swimming speed of prey. The calculated encounter rate was in good agreement with previously reported ingestion rates at low prey concentrations. From encounter rate and natural prey density, we conclude that O. davisae is capable of locating sufficient prey for its demands. Under natural conditions, where prey organisms may not be encountered regularly, the voracious O. davisae will ingest prey frequently when available. Our experimental methodology, devised to quantify the feeding abilities of O. davisae, is applicable to studying the foraging behavior of other copepod species.

The zooplankton prey field for rock lobster phyllosoma larvae in relation to oceanographic features of the south-eastern Indian Ocean

The western rock lobster, Panulirus cygnus, provides Australia's most valuable wild caught fishery but, in recent years, there has been a dramatic decline in settlement of the post-larval phase into their natal coastal habitat. One hypothesis for this decline was that the oceanographic conditions no longer favour the survival, feeding and growth of the larval (phyllosoma) phase. To explore this, the oceanography and corresponding zooplankton prey field along five latitudinal transects in the south-eastern Indian Ocean were quantified during July 2010. Leeuwin Current Water (LCW) and Sub-Tropical Surface Water (STSW) were distinguished and a prominent front at ∼30°S characterized by strong eastward flow separated them. Although zooplankton abundance increased towards the north, the prey field was unevenly distributed with patches of higher prey concentration associated mainly with LCW. Chaetognaths were the most abundant prey item (means: 17.2 and 4.1 m−3 in LCW and STSW, respectively) and were positively correlated with chlorophyll a in both water masses. Panulirus cygnus phyllosoma had a highly patchy distribution but, despite lower prey concentrations, were more abundant in STSW than LCW, particularly south of the front. Our results suggest that LC meso-scale features with strong fronts may be implicated in phyllosoma aggregations and shoreward transport of late-stage larvae and that this warrants further investigation.

Functional responses of juvenile herring and sprat in relation to different prey types

The relationship between particulate-feeding rates and prey concentrations (functional response) of juvenile herring and sprat (5–9 cm total length) was investigated in controlled feeding experiments monitored by an underwater camera system. A special tank system was developed allowing the regulation and quantification of low prey concentrations (1–160 L−1). Non-evasive Artemia nauplii was used as prey to estimate the maximum biting rate of both predators. In contrast, Acartia tonsa with a high escape ability was used as a realistic prey type. Herring and sprat showed a type II functional response for both prey types. Nonlinear mixed effects model revealed no significant difference between the functional responses of both predators, except that herring showed significantly higher biting rates than sprat at A. tonsa concentrations below ~40 L−1. For both predators feeding rates were significantly higher with Artemia nauplii than with A. tonsa. Video analysis indicated that sprat, unlike herring, is an obligate particulate-feeder.

Effects of prey density on nocturnal zooplankton predation throughout the ontogeny of juvenile Platax orbicularis (Teleostei: Ephippidae)

Juvenile Platax orbicularis switches foraging tactics from diurnal herbivory to nocturnal zooplanktivory within a day. To examine how juvenile fish actively feed on zooplankton prey during nighttime, a field-recorded video analysis was conducted in the reefs off Kuchierabu-jima Island, southern Japan. Juveniles consistently showed fast and sudden attacks that were accurately directed at individual zooplankton prey, and changed feeding frequencies with different prey densities. A negative relationship was observed between feeding frequency and prey density, with higher feeding frequencies occurring at lower prey concentrations, implying a disturbance effect of clouded zooplankton prey on the juvenile fish. A clear transition from a ram-based to a suction-based feeding mode was observed with fish size, suggesting that changes in the feeding behaviors occur even in juveniles fishes, without drastic morphological changes.

Detecting copepod grazing on low-concentration populations of Alexandrium fundyense using PCR identification of ingested prey

Zooplankton grazing is often a significant loss term for phytoplankton populations, including harmful algae, impacting the development and decline of blooms. However, detecting and quantifying predation on phytoplankton is often challenging, particularly during early bloom stages when phytoplankton cell concentrations are low. In this study, we used polymerase chain reaction (PCR) to detect ingestion of toxic dinoflagellates of the Alexandrium tamarense species complex by two copepods, Acartia hudsonica (laboratory population) and Calanus finmarchicus (field population). Recent ingestion of Alexandrium fundyense cells was indicated by positive amplification of an LSU rDNA fragment specific to A. fundyense from whole copepod extracts. In laboratory experiments, A. fundyense DNA was detectable for 2–4 h post-ingestion in A. hudsonica fed A. fundyense, but not detected in animals fed other phytoplankton, or starved. In field samples, ingestion of A. fundyense by C. finmarchicus was confirmed by PCR, including at four stations where the A. fundyense concentration was ≤14 cells L−1. At these low prey concentrations, ingestion rates on A. fundyense may have been as low as 1 cell copepod−1 day−1. Nevertheless, simulations of A. fundyense population growth suggest that a few predators L−1 have the potential to curb the early development of a slow-growing bloom, even if ingestion rates are extremely low. Low predation rates can still have a large impact when prey populations are small.

The role of prey concentration and size range in the growth and survival of larval cod

The effects of food quantity vs. food quality may be influenced by complex interactions that are difficult to isolate in trophic studies of fish larvae in the natural environment. Food quantity, or abundance, is mediated by the proportion of suitable prey available, with ‘suitability’ defined variously as size, species, or nutritional content. Using an experimental approach, food consumption, growth, and survival of larval cod, in response to zooplankton abundance and diversity of zooplankton sizes, were tested in a replicated land-based mesocosm (2500 l) system. Northeast Arctic cod (Gadus morhua L.) larvae were reared for two months with a manipulated zooplankton prey field comprised of narrow (N) or wide (W) prey spectrum (range of prey sizes), combined with high (H) or low (L) prey concentration. In the W treatments, cod larvae were fed both small and large sized zooplankton, while in the N treatments they were fed only small zooplankton. Initial prey concentration was 2000 prey l−1 in the H treatments and 200 prey l−1 in the L treatments, decreasing to 500 and 50 prey l−1 during the course of the experiment. Larval cod grew faster at higher prey concentrations. Prey concentration as well as spectrum affected larval feeding patterns with a wider spectrum prey size leading to the consumption of larger prey, but without a significant effect on larval growth. Survival was significantly higher in high prey concentration treatments, and also tended to be better in treatments with wider prey size diversity.

Role of food uptake for photosynthesis, growth and survival of the mixotrophic dinoflagellate Dinophysis acuminata

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 381:51-62 (2009) - DOI: https://doi.org/10.3354/meps07953 Role of food uptake for photosynthesis, growth and survival of the mixotrophic dinoflagellate Dinophysis acuminata K. Riisgaard*, P. J. Hansen Marine Biological Laboratory, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark *Email: kriisgaard@gmail.com ABSTRACT: Dinophysis acuminata is a mixotrophic dinoflagellate frequently causing diarrhetic shellfish poisoning. D. acuminata was isolated from Danish coastal waters and cultivated using the mixotrophic ciliate Mesodinium rubrum as prey. The roles of food uptake and photosynthesis for the growth and survival of D. acuminata were studied. The observed maximum growth rate was ca. 0.45 d–1 at an irradiance of 100 µmol photons m–2 s–1 when supplied with well-fed M. rubrum at concentrations >1000 M. rubrum ml–1. The corresponding ingestion rate per D. acuminata was about 9 M. rubrum d–1, or 3200 pg C d–1. Apart from the importance of prey concentration, data revealed that ingestion and growth of D. acuminata are, to a certain degree, dependent on the growth rate of its ciliate prey. Photosynthesis was studied in a culture of D. acuminata, initially grown at prey saturation (>1000 M. rubrum cells ml–1) and subsequently allowed to deplete the prey. When the ciliate prey was added, the photosynthetic rate of D. acuminata increased from about 7 to 38 pg C cell–1 h–1 within the first 2 d. When subsequently subjected to starvation, the photosynthetic activity rapidly decreased to a pre-feeding level, and, without a minimum food uptake, D. acuminata was not able to maintain photosynthetic growth. At high prey concentrations, 70 to 90% of the gross C uptake can be explained by food uptake. However, at low prey concentrations, only 0 to 55% of the gross C uptake is likely to be derived from food uptake. The data indicate that in natural environments, D. acuminata may often be food limited, and, in this situation, photosynthesis may not only be a supplement to the basic nutrition, but rather the primary C source. KEY WORDS: Dinophysis acuminata · Dinoflagellate · Mixotrophy · Photosynthesis · Growth · Survival · Mesodinium rubrum Full text in pdf format PreviousNextCite this article as: Riisgaard K, Hansen PJ (2009) Role of food uptake for photosynthesis, growth and survival of the mixotrophic dinoflagellate Dinophysis acuminata. Mar Ecol Prog Ser 381:51-62. https://doi.org/10.3354/meps07953 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 381. Online publication date: April 17, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Effects of prey concentration, light regime, and parental origin on growth and survival of herring larvae under controlled experimental conditions

Abstract Folkvord, A., Høie, H., Johannessen, A., and Solbakken, T. 2009. Effects of prey concentration, light regime, and parental origin on growth and survival of herring larvae under controlled experimental conditions. – ICES Journal of Marine Science, 66: 1702–1709. Experiments were undertaken to study the combined effects of environmental (prey concentration and photoperiod) and genetic (parental spawning season) factors on growth and survival of herring larvae. During the experimental period, constant prey concentrations were maintained at one of the two nominal levels, under either a spring or an autumn light regime. Eggs of one autumn-spawning North Sea Buchan female herring were fertilized either with cryopreserved sperm from three Norwegian spring-spawning males or with fresh sperm from three Buchan males. Larvae of the two groups (the hybrids marked with alizarin) were mixed in replicated treatment tanks, thus ensuring identical environmental conditions. Mean larval growth rates were mostly influenced by food availability, but the hybrids grew significantly faster than the pure autumn-spawned offspring. In addition, the hybrids experienced a survival advantage at low prey concentrations. Hybrid survival was also somewhat better at high prey concentrations under a spring photoperiod than the corresponding group under an autumn photoperiod, suggesting a possible genetic adaptation to seasonal light conditions. The experiment documents the viability beyond first-feeding of offspring from parents with different spawning periods. The results are discussed in relation to herring metapopulation structure.

A common garden experiment with larval Northeast Arctic and Norwegian coastal cod cohorts in replicated mesocosms

Abstract A replicated mesocosm experiment was carried out to evaluate differential effects of feeding conditions for larval Northeast Arctic (NA) cod and Norwegian coastal (NC) cod. The two populations were (1) reared together with a 6-day older NA cohort (mixed) in high (HC) and low prey concentration (LC; 2000 and 200 prey/L initially), and (2) reared separately in HC treatments (non-mixed) to be able to evaluate both the effect of feeding conditions and possible effects of size interaction within mesocosms. The larvae were fed natural zooplankton, and the two stocks were identified in the mixed mesocosms by otolith marking. NA larvae hatched at a larger size, had higher growth rates, and survived better than NC larvae in both mixed and non-mixed mesocosms in the HC treatment. The second cohort clearly survived better in the non-mixed than in the mixed mesocosms, indicating the presence of an interaction effect before cannibalism could occur. We found a significant higher weight-at-length between NC and NA larvae (

Prey size spectrum and bioenergetics of the mixotrophic dinoflagellate Karlodinium armiger

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 50:289-299 (2008) - DOI: https://doi.org/10.3354/ame01166 Prey size spectrum and bioenergetics of the mixotrophic dinoflagellate Karlodinium armiger Terje Berge1,2,*, Per Juel Hansen1, Øjvind Moestrup2 1Marine Biological Laboratory, Aquatic Biology Department of Biology, University of Copenhagen, Strandpromenaden 5, 3000 Helsingør, Denmark 2Phycology Laboratory, Aquatic Biology Department of Biology, University of Copenhagen, Øster Farimagsgade 2D, 1353 Copenhagen K, Denmark *Email: tberge@bi.ku.dk ABSTRACT: We studied the functional and numerical response and prey size spectrum in the tube-feeding dinoflagellate Karlodinium armiger. Growth rates were very low when no food was supplied (0.01 to 0.06 d-1). When K. armiger was fed the dinoflagellate Heterocapsa triquetra and the cryptophyte Rhodomonas salina, maximum growth rates (μ) were 0.48 and 0.55 d-1 and maximum ingestion rates were 215 and 597 pg C cell-1 d-1, respectively. Much lower prey concentrations were required to saturate growth rates compared to the saturation of ingestion rates. The optimal prey size, in terms of ingestion rates, was ~13 µm, which is close to the size of the predator. Smaller prey (<8 µm) were ingested at low rates (20 to 24 pg C cell-1 d-1), but supported fairly high growth rates (0.35 to 0.45 d-1). No upper prey size limit for ingestion was found. Maximum growth rates at food saturation depended more on prey taxa (cryptophytes) than on prey size. K. armiger’s large range of prey types, wide prey size spectrum and nutritional flexibility seem to make it a significant competitor in marine plankton. KEY WORDS: Mixotrophy · Bioenergetics · Prey selection · Peduncle · Karlodinium Full text in pdf format PreviousNextCite this article as: Berge T, Hansen PJ, Moestrup Ø (2008) Prey size spectrum and bioenergetics of the mixotrophic dinoflagellate Karlodinium armiger. Aquat Microb Ecol 50:289-299. https://doi.org/10.3354/ame01166 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 50, No. 3. Online publication date: March 26, 2008 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2008 Inter-Research.