Effects Of Prey Concentration Research Articles

Physical-biological interactions in the ocean: case studies from the northern Canary Current Upwelling Ecosystem

Physical-biological interactions in the ocean: case studies from the northern Canary Current Upwelling Ecosystem

Diel feeding rhythms in marine microzooplankton: effects of prey concentration, prey condition, and grazer nutritional history

In this study, we aim at disentangling the causes and consequences of diel feeding rhythms in marine microzooplankton. We focused on the diel feeding activity of two heterotrophic dinoflagellate species, Gyrodinium dominans (one laboratory strain) and Oxyrrhis marina (laboratory cultivated and wild strains). We observed higher ingestion during the day in both dinoflagellate species. Feeding rhythms appeared to be independent of circadian changes in prey biochemical composition. Grazers fed with prey under stationary phase, with equivalent stoichiometric composition between day and night, showed 5 (G. dominans) and 10 (O. marina) times higher ingestion rates during the day. Previous grazer feeding history (starved vs well-fed) did not affect the feeding rhythm. However, prey concentration altered the rhythm; food limiting conditions reduced the amplitude of the rhythms. Our results establish a resource dependence of diel periodicity in microzooplankton grazing, which can have unanticipated consequences for standard field dilution grazing experiments.

Effect of prey concentrations and feed training on production of Hoplias lacerdae juvenile.

The aim of this work was to investigate the effects of daily prey concentration during the first 15 days of active feeding of Hoplias lacerdae larvae, and the juvenile size on the feed training. In the first phase, the larvae received five Artemia nauplii concentrations (P). In the second phase, the juveniles from each treatment were trained to accept formulated diet. Superior growth was related to higher initial daily prey concentrations (900 and 1100 nauplii larvae-1). During feed training, the growth tendency was similar to that verified in the first phase. The lowest values of specific growth rate (SGR) were registered after the introduction of the semi-moist diet used in the feed training. However, the values of SGR recovered along the experiment and similar rates were found among the treatments. Survival, mortality and cannibalism were similar in the different treatments at the end of both phases. It can be concluded that: the prey concentration affects growth of H. lacerdae during the first 15 days of active feeding, and feed training can be initialized with juveniles of about 16 mm of total length.

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.

Feeding by the newly described mixotrophic dinoflagellate Gymnodinium smaydae: Feeding mechanism, prey species, and effect of prey concentration

To investigate feeding by the newly described mixotrophic dinoflagellate Gymnodinium smaydae, we explored the feeding mechanism and the kinds of prey species that G. smaydae is able to feed on. In addition, we measured the growth and ingestion rates of G. smaydae on optimal and suboptimal algal prey Heterocapsa rotundata and Heterocapsa triquetra as a function of prey concentration. Among the 19 algal prey species offered, G. smaydae ingested only thecate dinoflagellates H. rotundata, H. triquetra, Heterocapsa sp., and Scrippsiella trochoidea. Among the peduncle-feeding dinoflagellates so far reported, G. smaydae is the only grazer that is able to feed on S. trochoidea and one of the two species that are able to feed on H. triquetra. However, G. smaydae did not feed on the raphidophyte Heterosigma akashiwo, the cryptophytes Teleaulax sp. and Rhodomonas salina, and the small dinoflagellate Amphidinium carterae which all the other peduncle-feeding dinoflagellates except Stoeckeria algicida are able to feed on. G. smaydae fed on algal prey using a peduncle after anchoring the prey by a tow filament. All Heterocapsa species supported high positive growth of G. smaydae, S. trochoidea only helped in merely maintaining the predator population. With increasing mean prey concentration, the growth and ingestion rates for G. smaydae on H. rotundata increased rapidly, but became saturated at concentrations of 455ngCml−1 (3500cellsml−1), while that on H. triquetra increased rapidly, but slowly at concentrations of 293ngCml−1 (945cellsml−1). The maximum specific growth rates (i.e., mixotrophic growth) of G. smaydae on H. rotundata and H. triquetra were 2.226d−1 and 1.053d−1, respectively, at 20°C under a 14:10h light–dark cycle of 20μEm−2s−1, while the growth rates (i.e., phototrophic growth) under the same light conditions without added prey were 0.005 to −0.051d−1. The maximum ingestion rates of G. smaydae on H. rotundata and H. triquetra were 1.59ngCgrazer−1d−1 (12.3cellsgrazer−1d−1) and 0.24ngCgrazer−1d−1 (0.8cellsgrazer−1d−1), respectively. The calculated grazing coefficients for G. smaydae on co-occurring H. rotundata or H. triquetra were up to 0.23h−1 or 0.02h−1, respectively (i.e., 21% or 2% of the population of H. rotundata or H. triquetra was removed by G. smaydae populations in 1h). The results of the present study suggest that G. smaydae can sometimes have a considerable grazing impact on the population of H. rotundata.

Mixotrophy in the Newly Described Phototrophic Dinoflagellate Woloszynskia cincta from Western Korean Waters: Feeding Mechanism, Prey Species and Effect of Prey Concentration

Woloszynskia species are dinoflagellates in the order Suessiales inhabiting marine or freshwater environments; their ecophysiology has not been well investigated, in particular, their trophic modes have yet to be elucidated. Previous studies have reported that all Woloszynskia species are photosynthetic, although their mixotrophic abilities have not been explored. We isolated a dinoflagellate from coastal waters in western Korea and established clonal cultures of this dinoflagellate. On the basis of morphology and analyses of the small/large subunit rRNA gene (GenBank accession number=FR690459), we identified this dinoflagellate as Woloszynskia cincta. We further established that this dinoflagellate is a mixotrophic species. We found that W. cincta fed on algal prey using a peduncle. Among the diverse prey provided, W. cincta ingested those algal species that had equivalent spherical diameters (ESDs) ≤12.6 μm, exceptions being the diatom Skeletonema costatum and the dinoflagellate Prorocentrum minimum. However, W. cincta did not feed on larger algal species that had ESDs≥15 μm. The specific growth rates for W. cincta increased continuously with increasing mean prey concentration before saturating at a concentration of ca. 134 ng C/ml (1,340 cells/ml) when Heterosigma akashiwo was used as food. The maximum specific growth rate (i.e. mixotrophic growth) of W. cincta feeding on H. akashiwo was 0.499 d(-1) at 20 °C under illumination of 20 μE/m(2) /s on a 14:10 h light-dark cycle, whereas its growth rate (i.e. phototrophic growth) under the same light conditions without added prey was 0.040 d(-1). The maximum ingestion and clearance rates of W. cincta feeding on H. akashiwo were 0.49 ng C/grazer/d (4.9 cells/grazer/d) and 1.9 μl/grazer/h, respectively. The calculated grazing coefficients for W. cincta on co-occurring H. akashiwo were up to 1.1 d(-1). The results of the present study suggest that grazing by W. cincta can have a potentially considerable impact on prey algal populations.

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.

Feeding by the mixotrophic red-tide dinoflagellate Gonyaulax polygramma: mechanisms, prey species, effects of prey concentration, and grazing impact

The red-tide dinoflagellate Gonyaulax polygramma (GenBank accession number = AJ833631), previously known as an exclusively autotrophic dinoflagellate, has been found to be a mixotrophic species. We investigated feeding mechanisms, types of prey species, and the effects of prey concentration on the growth and ingestion rates of G. polygramma when feeding on an uniden- tified cryptophyte species (equivalent spherical diameter, ESD = 5.6 µm). We also calculated grazing coefficients by combining field data on abundances of G. polygramma and co-occurring cryptophytes with laboratory data on ingestion rates obtained in the present study. Among the phytoplankton prey offered, G. polygramma ingested small phytoplankton species with ESD ≤ 17 µm, but did not feed on large phytoplankton species with ESD > 22 µm. G. polygramma fed on prey cells by engulfing them through the apical horn, a previously unknown mechanism, as well as through the sulcus. The feed- ing mechanism of G. polygramma on phytoplankton mainly depended on the prey species. Specific growth rates of G. polygramma on a cryptophyte increased with increasing mean prey concentration, with saturation occurring at a mean prey concentration of approximately 600 ng C ml -1 . The maxi- mum specific (mixotrophic) growth rate of G. polygramma on a cryptophyte was 0.278 d -1 , under a 14:10 h light:dark cycle of 50 µE m -2 s -1 , while its (phototrophic) growth rate under the same light conditions without added prey was 0.186 d -1 . Its maximum ingestion and clearance rates were 0.18 ng C grazer -1 d -1 (10.6 cells grazer -1 d -1 ) and 0.18 µl grazer -1 h -1 , respectively. The grazing coefficients of G. polygramma on cryptophytes were up to 0.479 h -1 . The results of the present study suggest that G. polygramma can have a considerable grazing impact on cryptophyte populations.

Mixotrophy in the Phototrophic Harmful Alga Cochlodinium polykrikoides (Dinophycean): Prey Species, the Effects of Prey Concentration, and Grazing Impact

We first reported here that the harmful alga Cochlodinium polykrikoides, which had been previously known as an autotrophic dinoflagellate, was a mixotrophic species. We investigated the kinds of prey species and the effects of the prey concentration on the growth and ingestion rates of C. polykrikoides when feeding on an unidentified cryptophyte species (Equivalent Spherical Diameter, ESD = 5.6 microm). We also calculated grazing coefficients by combining field data on abundances of C. polykrikoides and co-occurring cryptophytes with laboratory data on ingestion rates obtained in the present study. Cocholdinium polykrikoides fed on prey cells by engulfing the prey through the sulcus. Among the phytoplankton prey offered, C. polykrikoides ingested small phytoplankton species that had ESD's < or = 11 microm (e.g. the prymnesiophyte Isochrysis galbana, an unidentified cryptophyte, the cryptophyte Rhodomonas salina, the raphidophyte Heterosigma akashiwo, and the dinoflagellate Amphidinium carterae). It did not feed on larger phytoplankton species that had ESD's > or = 12 microm (e.g. the dinoflagellates Heterocapsa triquetra, Prorocentrum minimum, Scrippsiella sp., Alexandrium tamarense, Prorocentrum micans, Gymnodinium catenatum, Akashiwo sanguinea, and Lingulodinium polyedrum). Specific growth rates of C. polykrikoides on a cryptophyte increased with increasing mean prey concentration, with saturation at a mean prey concentration of approximately 270 ng C ml(-1) (i.e. 15,900 cells ml(-1)). The maximum specific growth rate (mixotrophic growth) of C. polykrikoides on a cryptophyte was 0.324 d(-1), under a 14:10 h light-dark cycle of 50 microE m(-2) s(-1), while its growth rate (phototrophic growth) under the same light conditions without added prey was 0.166 d(-1). Maximum ingestion and clearance rates of C. polykrikoides on a cryptophyte were 0.16 ng C grazer(-1)d(-1) (9.4 cells grazer(-1)d(-1)) and 0.33 microl grazer(-1)h(-1), respectively. Calculated grazing coefficients by C. polykrikoides on cryptophytes were 0.001-0.745 h(-1) (i.e. 0.1-53% of cryptophyte populations were removed by a C. polykrikoides population in 1 h). The results of the present study suggest that C. polykrikoides sometimes has a considerable grazing impact on populations of cryptophytes.

Effect of prey concentration on growth of piscivorous Japanese Spanish mackerel Scomberomorus niphonius larvae in the Seto Inland Sea, Japan

Summary Japanese Spanish mackerel, Scomberomorus niphonius, larvae feed almost exclusively on fish larvae from the first-feeding stage. The relationship between the growth of S. niphonius larvae and concentration of major prey organisms of the larvae, clupeid larvae, was investigated in the Sea of Hiuchi, the central Seto Inland Sea, Japan, from 28 to 29 May 1997. Water temperature, salinity, and the concentration of clupeid larvae had no significant effect on the S. niphonius larval concentration. Mean growth rate of S. niphonius larvae varied between 0.38 and 0.64 mm day−1. The temperature and salinity had no significant effect on the mean larval growth rate while there existed prey concentration-dependent growth at lower prey concentration. The relationship between the mean larval growth rate (Gm) and concentration of clupeid larvae (CC) was expressed by a logarithmic equation: Gm = 0.037 log CC + 0.441 (n = 16, r2 = 0.519, P < 0.01).

Mixotrophic feeding of Fragilidium subglobosum (Dinophyceae) on three species of Ceratium:effects of prey concentration, prey species and light intensity

Mixotrophic feeding of Fragilidium subglobosum (Dinophyceae) on three species of Ceratium:effects of prey concentration, prey species and light intensity

Effects of prey concentration, prey size, predator life stage, predator starvation, and season on predation rates of the carnivorous copepod Euchaeta elongata

Adult females of the large carnivorous copepod Euchaeta elongata Esterly were collected from 1977 to 1980 in Port Susan, Washington, USA. Predation rates of the adult females increased with increasing prey abundance when fed the following 4 sizes of copepods: adult females of Calanus pacificus (average prosome length [PL] of 2 650 μm), adults of Aetideus divergens (PL of 1 560 μm), adult females of Pseudocalanus spp. (PL of 1 060 μm), and nauplii of C. pacificus (PL of 410 μm). Saturation feeding levels were reached when adult females of the predator were fed the small adult copepod, Pseudocalanus spp. Maximum biomass ingested of this small copepod was more than the maximum amount ingested of the larger copepods. Predation rates of the predatory copepodids at Stages IV and V also increased with increasing concentration of the 1 060 μm (PL) prey. High feeding rates exhibited by both adults and copepodids at Stage V of the predator indicate their importance as sources of mortality on populations of small copepods. Ingestion efficiency E i (prey wholly consumed [prey attacked]-1) varied as follows: adults of E. elongata were more efficient than copepodids of E. elongata; adults were more efficient than copepodids when ingesting smaller prey; starved adults were more efficient than fed ones; and both adults and copepodids were more efficient at low food concentrations. For adults of E. elongata, there were no marked seasonal variations in predation or respiratory rates that would represent acclimatory responses; however, small adults obtained during winter were more efficient at ingesting prey than were the larger adults gathered in summer. This seasonal variation in the efficiency of ingestion may be a useful indicator of physiological state: high E i values could indicate that predators are starving in winter, and low E i values could indicate that predators are satiated in summer.