Dominant Copepod Species Research Articles

The modified artificial cohort method for three dominant pelagic copepods in the northern North Pacific revealed species-specific differences in the optimum temperature

The most concerning recent ocean changes in temperature issues are known as marine heat waves. Under these conditions, it is important to evaluate the effects of temperature on zooplankton. In this study, we investigated the growth rates of three dominant copepod species (Eucalanus bungii, Metridia pacifica, and Neocalanus plumchrus) in the northern North Pacific under three different temperature conditions (3, 7, and 11°C) using an artificial cohort method. Experimental conditions for 42 hour incubations were set to light intensity and photoperiod corresponding to 50 m depth. The dissolved oxygen solubility after rearing ranged from 69.2% to 102.1%, suggesting sufficient conditions for copepod growth. Chlorophyll a increased in 83% of the experiments, indicating that the food conditions were sufficient for the copepods. The mean proportion of dead specimens evaluated using neutral red was 10.2%, corresponding with the reported values in the field. Thus, it can be concluded that the laboratory-rearing conditions used in this study provided sufficient food, and the only effect evaluated would be that of the three different temperatures. Since the developmental time for each stage is longer than the rearing period, it is important to conduct experiments with a large number of individuals to obtain accurate growth rate results. The specific growth rates of E. bungii and M. pacifica increased with increasing temperature. In contrast, N. plumchrus showed the highest growth rate under moderate water temperature conditions. In terms of weight units (dry, carbon, and nitrogen), the carbon weight-specific growth rates were higher than those of the other two units, a common characteristic of the three species. This reflected lipid accumulation during the late copepodite stages. The interspecies differences in growth rate responses to water temperature reflect species-specific differences in temperature tolerance or the optimum temperature for each species. As E. bungii and M. pacifica reproduce near the surface layer through income breeding, their temperature tolerance or optimum temperature is expected to be high. However, because the reproduction of N. plumchrus occurs in the cold deep layer by using capital breeding, its temperature tolerance and optimum temperature would be lower than those of the former two species.

Sediment trap samples reveal regional differences in the population structure of Calanus hyperboreus from the Arctic Ocean

Abstract Calanus hyperboreus is one of the dominant copepod species in the Arctic zooplankton communities. The impact of climate change varies among regions within the Arctic, implying that C. hyperboreus populations may be differently affected at different locations, but knowledge on seasonal population dynamics in relation to biogeography is scarce. To fill this gap, we counted C. hyperboreus in samples from sediment traps that were moored from 2009 to 2014 in three regions of the Arctic Ocean (eastern Fram Strait, northern Chukchi Sea and MacKenzie Trough). The C. hyperboreus flux increased between April and May in all regions, likely associated with the ascent from overwintering depth to the surface. In the descent period, high fluxes were observed between July and September in the Fram Strait, between September and November in the northern Chukchi Sea, and between August and October in the MacKenzie Trough, suggesting that the timing of descent varied among the regions characterized by differences in light regime, phytoplankton development and water temperature. The copepodite stage composition in the eastern Fram Strait and the MacKenzie Trough varied with season, suggesting successful local reproduction while it was uniform in the northern Chukchi Sea, possibly because the population is fueled by advection.

Population Dynamics of Copepods as Influenced by Heavy Metals in Khanki Headworks, Pakistan

Copepods grow in diverse freshwater habitats, totaling around 2,814 species. As foremost zooplankton, they lead biomass and are pivotal in aquatic ecosystems. The ever-increasing issue of heavy metals contamination affects organisms differently. Copepods, with their broad geographic range, can be valuable bio monitors for metal growth. Objective: To evaluate the effects of heavy metals and fish diversity on the population dynamics of copepods in Khanki Headworks, Pakistan. Methods: For the analysis of heavy metals month wise water samples (1000 ml) from four selected sites were collected for one year (February 2021 to January 2022). Atomic Absorption Spectrophotometry was employed for the analysis of heavy metals. Month wise copepods samples were collected with planktonic net (mesh size: 37µm). Results: In total, seven species and four genera of copepods were identified. Mesocyclops edax was the most dominant copepod species. Three heavy metals zinc (Zn), arsenic (As) and nickel (Ni) were estimated in following order of concentrations Zn> Ni> As. Conclusions: Current investigation revealed that heavy metals generally govern the population dynamics of copepods.

Decadal decline of dominant copepod species in the North Sea is associated with ocean warming: Importance of marine heatwaves

Time-series are crucial to understand the status of zooplankton communities and to anticipate changes that might affect the entire food web. Long-term time series allow us to understand impacts of multiple environmental and anthropogenic stressors, such as chemical pollution and ocean warming, on the marine ecosystems. Here, a recent time series (2018–2022) of abundance data of four dominant calanoid and one harpacticoid copepod species from the Belgian Part of the North Sea was combined with previously collected (2009–2010, 2015–2016) datasets for the same study area. The time series reveals a significant decrease (up to two orders of magnitude) in calanoid copepod abundance (Temora longicornis, Acartia clausi, Centropages spp., Calanus helgolandicus), while this was not the case for the harpacticoid Euterpina acutifrons. We applied generalized additive models to quantify the relative contribution of temperature, nutrients, salinity, primary production, turbidity and pollution (anthropogenic chemicals, i.e., polychlorinated biphenyls and polycyclic aromatic hydrocarbons) to the population dynamics of these species. Temperature, turbidity and chlorophyll a concentrations were the only variables consistently showing a relative high contribution in all models predicting the abundances of the selected species. The observed heat waves which occurred during the summer periods of the investigated years coincided with population collapses (versus population densities in non-heatwave years) and are considered the most likely cause for the observed copepod abundance decreases. Moreover, the recorded water temperatures during these heatwaves correspond to the physiological thermal limit of some of the studied species. As far as we know, this is the first study to observe ocean warming and marine heat waves having such a dramatic impact (population collapse) on the dominant zooplankton species in shallow coastal areas.

Impact of a Dinophysis acuminata Bloom on the Copepod Acartia clausi: First Indications

Faecal pellet production and content along with egg production of the dominant copepod species Acartia clausi were studied in the Thermaikos Gulf (NW Aegean Sea) during a pre-bloom and a bloom of the toxic dinoflagellate Dinophysis acuminata. Both faecal pellet production (6.8–8.6 ind−1 d−1) and egg production (15.8–47.6 ind−1 d−1) appeared unrelated to the D. acuminata bloom. Less than 11% of the copepod faecal pellets contained one or two D. acuminata cells, almost intact, whereas the other material in the pellets was broken into small pieces or amorphous shapes. The toxin outflux seemed to be insignificant when compared to the mean toxin concentration from the whole D. acuminata population. Finally, the potential grazing impact of A. clausi on D. acuminata during the study period was low.

Copepods and mixotrophic Rhizaria dominate zooplankton abundances in the oligotrophic Indian Ocean

The large, tropical oligotrophic gyres of the world's oceans are understood to be relatively unproductive, with low phytoplankton and zooplankton biomass, and inefficient food webs, although data are scarce. Here we investigate changes in the zooplankton assemblage along a 15 °C temperature gradient from 20 stations on the 110°E transect as part of the second International Indian Ocean Expedition. To ensure that we reflect most of the zooplankton biodiversity, we used a 100 μm mesh net to capture the small copepod and microzooplankton components that are important and often overlooked in tropical systems. Further, to obtain a synoptic view, we towed the Continuous Plankton Recorder between stations across 30° of latitude. We found that copepod assemblages clustered into four groups, with the most distinct being at the highest latitudes south of the sub-tropical Front. As the ocean temperature increased from south to north along the transect, zooplankton abundance and diversity also increased. The dominant copepod species changed accordingly and were predominantly those with the ability and/or preference to selectively feed on microzooplankton. Although copepods were the most abundant taxon, the proportion of microzooplankton, particularly, mixotrophic Rhizaria, was consistently high. Thus, our study found a highly mixotrophic system supporting secondary production in the oligotrophic Indian Ocean.

Vertical occurrence of copepod carcasses in the Cosmonaut Sea during austral summer

Zooplankton carcasses and their contribution to carbon export are increasingly garnering attention in food web studies of polar oceans. We investigated the occurrence of carcasses of dominant copepod species at four depths (100–200 m, 200–500 m, 500–1000 m, 1000–1500 m) and their potential contribution to particulate organic carbon (POC) concentrations in the Cosmonaut Sea, Antarctica, during summer, 2019/2020. The abundance of small copepods (< 2 mm), either live or dead individuals, was 1-3 orders of magnitude higher than the four dominant large copepod species Calanoides acutus, Calanus propinquus, Metridia gerlachei and Rhincalanus gigas at each depth. Most carcasses were observed at the surface (100–200 m), while the proportions of dead individuals increased with depth, from 22% in the 100–200 m layer to 70% of the 500–1500 m layer. The total number of passive sinkers (carcasses and moults) was dominated by carcasses of small copepods in each depth layer, while the carbon biomass of passive sinkers was dominated by carcasses of large copepods. Both abundance and carbon biomass of passive sinkers decreased with depth. The average contribution of passive sinkers to the POC concentration decreased from 0.27% in the 100–200 m depth stratum to 0.10% in the 500–1500 m layer. This study provides the first report of occurrence and contribution of carcasses from the surface to the mesopelagic layer of the Southern Ocean. This information can improve understanding of the role zooplankton play in downward carbon flux within the ocean’s twilight zone.

Feeding dynamics of the invasive calanoid copepod Pseudodiaptomus inopinus in two northeast Pacific estuaries

The Asian calanoid copepod Pseudodiaptomus inopinus, first observed in the Columbia River Estuary in the early 1990s, has since become the dominant copepod species in many estuaries along the US Pacific coast, but its feeding behavior has not been previously studied. In October 2019 and 2020, when P. inopinus was at peak seasonal abundance, we conducted incubation experiments with this species feeding on natural microplankton prey assemblages sampled from 2 invaded estuaries: the Chehalis River estuary, Washington, and the Yaquina River estuary, Oregon. In both estuaries, diatoms were the most numerically abundant prey group, with 11-15 µm Chaetoceros sp. and 21-25 µm Cyclotella sp. dominating the Chehalis and Yaquina estuaries, respectively. Diatom and ciliate biomass were highest in both estuaries, with all prey cells in the Yaquina estuary typically larger than those in the Chehalis estuary. P. inopinus fed omnivorously on microplankton prey, with a preference for prey &gt;20 µm and occasional avoidance of cyanobacteria and cells &lt;10 µm. Ingestion rates were highest on ciliates and diatoms. The omnivory of P. inopinus may contribute to its success as an invader in northeast Pacific estuaries.

Latitudinal gradient of copepod functional diversity in the South Atlantic Ocean

There is a growing consensus for assessing the multifaceted marine biodiversity by analyzing morphological taxonomy and biological traits to link the biodiversity and ecosystem functioning relationships (BEF) to environmental variability. We applied taxonomic and functional diversity indices to relate copepod biodiversity with ecosystem functioning along different biogeographic zones from the Southwestern Atlantic to the Southern Ocean. To assess the link between functional traits and environmental gradients, we clustered 94 species into functional groups based on the combination of five functional traits. Taxonomic and functional diversity showed a linear decreasing trend along the latitudinal gradient. Species richness peaked at the subtropical latitude (∼30°S), while the functional richness was similar from the tropical up to the temperate region (∼45°S), which hosted on average 70% of the total pool of species, and dropped to only 16% in polar waters. We found that small- and medium-bodied broadcasting, large cruising carnivorous and detritivorous copepods contributed mostly to the larger functional space in tropical and subtropical zones. In turn, dominant copepod species with contrasting traits enhanced the functional divergence and decreased functional evenness poleward. Our results indicate that distinct copepod functional groups with specific environmental preferences are influenced by ecological mechanisms that promote functional richness through complementary resource use and niche partitioning. These findings highlight the relationship between species diversity and ecosystem functioning, which might contribute to ecosystem stability and resilience along environmental gradients.

Density‐dependent modulation of copepod body size and temperature–size responses in a shelf sea

AbstractBody size is a fundamental trait in ecology, and body size reduction with increasing temperature has been termed the third universal response to climate warming. Although effects of temperature and food on phenotypic plasticity of zooplankton adult body size have been investigated, density‐dependent effects have been neglected. We measured seasonal changes in the prosome length of 7098 adult females of 7 dominant copepod species in 13 yr spanning a 27‐yr period of warming at the L4 time series off Plymouth, UK. The seasonal temperature–size (T–S) response varied greatly among species, from reductions of 2.93% of carbon mass °C−1 for Paracalanus parvus to 10.15% of carbon mass °C−1 for Temora longicornis. Evidence for a long‐term T–S response was detected in at least two species, supporting the hypothesis that climatic warming leads to smaller adult sizes. April was a crucial month for determining the strength of the T–S response. During this month, body size related negatively to total zooplankton abundance. We suggest that the mechanism for this density dependence is via competition for food and/or intraguild predation, since spring was also the period when the ratio of food biomass to zooplankton biomass was at its lowest. Our study is among the first in situ demonstrations of density‐dependent effects on the body size of marine zooplankton and shows the need to consider the effect of top‐down as well as bottom‐up factors on body size in a warming climate.

Mechanisms of thermal treatment on two dominant copepod species in O3/BAC processing of drinking water

Phyllodiaptomus tunguidus and Heliodiaptomus falxus are dominant copepods species in drinking water processing plants in southern China. With a potential penetration risk, the breeding and leakage of copepods are drawing more and more attention in recent years. The current study provided a thermal treatment method to control copepods and their eggs. Results showed that: (1) the immediate death rates of P. tunguidus and H. falxus after heated to 34–40 °C for 5 min are positively correlated to the treatment temperatures (P < 0.01), and all individuals of the both species were eliminated after heated at 40 °C for 5 min; (2) overall hatching rates of P. tunguidus eggs were negatively correlated with treatment temperatures (P < 0.01) between 39–45 °C, with zero percent hatched after treatment at 45 °C for 5 min; (3) hatching rates of H. falxus were negatively correlated with treatment temperatures (P < 0.01) between 37–41 °C, with no nauplii hatched when treated at 41 °C for 5 min; (4) paraffin section histological examination indicated that thermal treatment caused severe damage to internal organs and egg structure. Finally, based on the experimental data, the application of the thermal treatment method was discussed in ozonation combined with biological activated carbon (O3/BAC) processing of drink water treatment.

Application of Next-Generation Sequencing for the Determination of the Bacterial Community in the Gut Contents of Brackish Copepod Species (Acartia hudsonica, Sinocalanus tenellus, and Pseudodiaptomus inopinus).

Simple SummaryCopepods are important components of marine coastal food chains, supporting fishery resources by providing prey items mainly for fish. Copepods interact with small microorganisms via feeding on phytoplankton. DNA methods can determine the gut contents of copepods and provide important information regarding how copepods interact with phytoplankton and bacteria. In the present study, we designed a method for extracting the gut content DNA from small-sized copepods that are important in coastal and brackish areas. Based on DNA analyses, Rhodobacteraceae, which is common in marine waters and sediments, was most abundant in the gut contents of the three copepod species (Acartia hudsonica, Sinocalanus tenellus, and Pseudodiaptomus inopinus). However, the detailed composition of bacteria was different among species and locations. The results suggested that environmental variables and species-specific feeding behaviour can affect the gut bacterial community. The bacteria play an important role in digestion and in the overall degradation and release of metabolites to the outside water. Further analyses with advanced methods regarding DNA isolation from small microorganisms and identification skills using a DNA library for better understanding of biological interactions and matter cycling in marine food webs are required.The gut bacterial communities of copepods can affect metabolic processes, and consequently, their activity can be related to the release of organic substances to the environment. Hence, they are important for organic matter cycling in marine coast food webs. However, information regarding the variation in gut bacterial communities based on copepod species and environmental variations is limited. We analysed the differences in gut bacterial communities from dominant copepod species, i.e., Acartia hudsonica, Sinocalanus tenellus, and Pseudodiaptomus inopinus, in a brackish reservoir. The core bacteria among the copepod species and locations consisted of the following main operational taxonomic units (OTUs): Novosphingobium capsulatum and the family Rhodobacteraceae belonging to Alphaproteobacteria, which is abundant in seawater and freshwater aquatic ecosystems as a zooplankton-associated bacterial community. The bacterial community composition of each copepod (except the core species) showed high variability. The bacterial community diversity differed depending on the copepod species and the sites’ environmental conditions, especially salinity, e.g., compositional variations in the bacterial community of P. inopinus were high at sites with low salinity. Therefore, the gut bacterial community of each copepod species responds differently to the environment.

Can chaoborid larvae control their zooplanktonic prey populations in a neotropical lake?

AbstractAlthough it is well known that predatory Chaoborus Lichtenstein 1800 larvae have a strong negative impact on zooplankton populations in many Holarctic lakes, this top‐down control is still not entirely clear in the Neotropics. In Lake Carioca, a Brazilian monomictic lake, chaoborids became one of the main zooplankton predators after the depletion of planktivorous fish by non‐native piscivorous fish. The aim of this research was to test the hypothesis that Chaoborus spp. larvae control the density of their prey populations. Enclosures simulated conditions with higher (Pr+) and lower (Pr−) predatory Chaoborus spp. larva densities over 30 days in two periods (stratification and mixing). Our results indicated that the dominant copepod species was affected only in the stratification period when its population was smaller. In this circumstance, predated individuals were probably not replaced in the same proportion by reproductive output of the smaller population. Rotifers were not sensitive to changes in chaoborids densities in both periods. The lack of a strong top‐down effect recorded by our mesocosm experiments emphasises the importance of continuing to investigate the ecological roles played by this invertebrate predator in aquatic food webs and if its ability to regulate the zooplankton in most Holarctic lakes can (or cannot) be widely generalised to Neotropical communities. Such a result also suggests that alternative research approaches, besides in‐situ experiments, may be necessary to better clarify this topic. Specifically for cladocerans, parallel paleolimnological analyses in Lake Carioca have supported the idea of a possible negative impact of Chaoborus larvae on bosminids after the introduction of non‐native piscivorous fishes.Abstract in Portuguese is available with online material.

Relative importance of predatory versus non-predatory mortality for dominant copepod species in the northern Chilean (23°S) Humboldt Current System

Relative importance of predatory versus non-predatory mortality for dominant copepod species in the northern Chilean (23°S) Humboldt Current System

Intra-monsoonal variation of zooplankton population in the Sundarbans Estuarine System, India.

The present study was conducted during July 2013 (early phase of monsoon or EM) and September 2013 (later phase of monsoon or LM) to ascertain the intra-monsoonal variation on zooplankton, by selecting 15 study stations in the river Saptamukhi, one of the main estuaries in the Sundarbans Estuarine System (SES). In 2013, SES experienced an unusually high monsoonal rainfall also exacerbated by cloud burst event at Himalayan region (upper stretches of SES) which tremendously increased the river runoff. The present work was aimed to decipher the effect of this unusual precipitation during the monsoon season on zooplankton assemblages along with different hydrological parameters. The abundance of zooplankton was recorded as lower during EM compared to LM. Altogether, 56 zooplankton taxa were identified with copepods forming the predominant population. Thirty-three copepod species were reported with 25 calanoid species forming the bulk of the biomass followed by 5 and 3 species of cyclopoids and harpacticoid, respectively. A combination of multivariate cluster analysis, biotic indices, and canonical correspondence analysis revealed noticeable alterations in the zooplankton community structure across the spatio-temporal scale. Furthermore, significant intra-monsoonal changes in zooplankton population correlated with several hydrological parameters were clearly noticed. Paracalanus parvus, Bestiolina similis and Oithona similis were observed to be the most dominant copepod species in both sampling periods. The result of the present study provides new insight on estuarine zooplankton community after unusual rainfall during monsoon season, and provides further evidence to support the conservation and management of the SES ecosystem.

Copepoda in the shallow hypersaline Bardawil coastal lake (Egypt): Are there long-term changes in composition and abundance?

Abstract Coastal Lake Bardawil (Egypt) is one of the largest hypersaline lakes in the world. In 2009–2010, the authors studied composition, distribution and seasonal dynamics of copepods at 12 sites. A total of 10 species of copepods were recorded in zooplankton during the study period, including 5 Calanoida, 2 Cyclopoida and 3 Harpacticoida. Oithona nana was the most common and most abundant species. All copepods in the lake can be divided into three groups: 1) planktic species that form stable populations, 2) species of Mediterranean plankton incidentally entering the lake from the adjacent sea area, 3) benthic Cyclopoida and Harpacticoida that can be abundant in plankton. Two species – Acartia tonsa and A. danae were recorded here for the first time. The total abundance of copepods in the lake was significantly higher (90 times on average) compared to that observed in 2008–2009 in the waters of the Egyptian Mediterranean Sea. Since 1967, the complex of common and dominant copepod species in the lake has changed significantly. The total average annual copepod abundance varied: in 2002 – it was about 4000 ind. m−3, in 2004 – 152 000 ind. m−3, in 2005 – about 25 300 ind. m−3, and in 2009–2010 – about 56 000 ind. m−3.

Biomass determination based on the individual volume of the dominant copepod species in the Western Egyptian Mediterranean Coast

The biomass of five copepod species (Oithona nana, Calocalanus pavo, Nannocalanus minor, Clausocalanus arcuicornis and Paracalanus parvus) that dominate the western part of the Egyptian Mediterranean Coast had been determined using the individual volume. The length-weight relationships and physicochemical influences on the length of species were also investigated. Copepod samples were seasonally collected during the period 2008–2009. All volumes and weights of the randomly selected adult individuals were measured. Ten regression equations confirmed that; the species weights depend on the total lengths of males and females of all species. However, the females of the examined species were always heavier and longer than males. The length and weight of both sexes of all species were higher in winter than in other seasons. Temperature is considered the main factor influencing the sizes of adult copepods. It was also found that the mean length of the examined individuals was inversely proportional to temperature. However, all the investigated organisms had adequate high levels of dissolved oxygen and didn't show any change with pH, salinity and transparency.

Copepod feeding strategies in the epipelagic to bathypelagic zone of Prydz Bay, Antarctica: an assessment through fatty acids and stable isotopes

Information on the feeding strategies and dietary preferences of copepods from epipelagic to bathypelagic zones of the Southern Ocean are important for understanding the role of zooplankton in carbon and energy transfers through the food web. Using fatty acids (FA) and stable isotopic biomarkers, the present study investigated the feeding strategies and trophic niches of seven dominant copepod species (Calanoides acutus, Calanus propinquus, Metridia gerlachei, Rhincalanus gigas, Paraeuchaeta antarctica, Aetideopsis minor and Bathycalanus richardi) collected from various water strata of Prydz Bay, Antarctica during the austral summer of 2013. Copepods showed species-specific and depth-related differences in FA biomarkers and stable isotopic values. C. acutus and C. propinquus had the largest content of long-chain monounsaturated FA, while M. gerlachei had the smallest FA content (approximately 40 mg g(-1) dry weight) and the highest 18:1n-9. FA of R. gigas were dominated by short- and medium-length carbon chains. The species P. antarctica and meso- and bathypelagic species A. minor and B. richardi showed relatively higher levels of carnivorous FA ratios and delta N-15 values. Higher delta N-15 values in M. gerlachei and P. antarctica dwelled in the mesopelagic and bathypelagic zone indicated the high diversity of feeding strategies of these copepods responding to the changing food availability. The flexible feeding strategies of copepods could enable them to utilise different ecological niches and minimise inter- and intra-specific competition in the Prydz Bay.

Striking taxonomic differences in summer zooplankton in the northern South China Sea: implication of an extreme cold anomaly

An extreme persistent cold anomaly was prevailing in the South China Sea in February 2008. In order to understand the effect of the cold anomaly on zooplankton community, the zooplankton composition, abundance and biomass were analyzed in the northern South China Sea in August 2007 and August 2008. A total of 467 zooplankton species representing 16 groups were identified, with 275 species in August 2007 and 351 in August 2008. Copepods were the most dominant zooplankton group in the study area. Compared with 2007, a dramatic decline was observed in the abundance of four dominant copepod species: Subeucalanus subcrassus, Temora discaudata, Nannocalanus minor and Temora turbinata in 2008. Moreover, zooplankton abundance declined from 133.37 ind./m3 in August 2007 to 75.49 ind./m3 in August 2008. In contrast, the abundance of medusa, such as Diphyes chamissonis, and tunicate, such as Doliolum denticulatum and Dolioletta gegenbauri, increased during the same season. Cluster analysis showed that there was a difference in zooplankton community structure between the two years. These variations in zooplankton communities were indicative of an anomalous oceanographic condition along with the extreme cold event in 2008.

A production season of turbot larvaeScophthalmus maximus(Linnaeus, 1758) reared on copepods in a Danish (56°N) semi-intensive outdoor system

Turbot were reared from yolk sack larvae to juvenile in an outdoor semi-intensive system. Three production cycles were monitored from May to September. A pelagic food chain was established with phytoplankton, copepods and turbot larvae. Abiotic and biotic parameters of lower trophic levels together with turbot larval survival, development, prey electivity and growth were monitored. A decreasing larval survival from 18.4% in May to 13.6% in July and just 7.0% in September was observed. The overall phytoplankton and copepod abundance decreased during the productive season. The turbot larval growth showed significant differences between larvae below (isometric) and above (allometric) 7 mm. Larval fish gut content showed no differences with available prey between production cycles. Therefore, it appears that the available prey concentration is governing their growth in this outdoor system. First-feeding turbot larvae exhibited active selection for nauplii whereas developed larvae switched to copepodites and adult copepods. Although developing turbot larva exhibited active selection towards copepod size classes, there was no evidence of selective feeding on either of the two dominant copepod species. The turbot larvae's prey ingestion was modelled together with the standing stock of copepod biomass. The model results indicated that the estimated need for daily ingestion exceeded the standing stock of copepods. Hence, the initially established food web was unable to sustain the added turbot larvae with starvation as a consequence. We therefore suggest several solutions to circumvent starvation in the semi-intensive system.