Feeding habits of Calanus sinicus (Crustacea : Copepoda) during spring and autumn in the Bohai Sea studied with the herbivore index

Pigment ingestion rate (PIR) and egg production rate (EPR) of the dominant copepod Calanus sinicus, as well as chlorophyll-a concentration and phytoplankton assemblages were measured in the Bohai Sea, North China in June 1997, October 1998 and May 1999. A herbivore index (H) was also calculated as the carbon specific ratio of PIR and EPR, in order to investigate its feeding habits in the spring and autumn phytoplankton bloom respectively. On average, chlorophyll-a concentration was relatively similar (1-1.34 mg m(-3)) in the three cruises, but PIR was quite different. It was 3.24 mu g C female(-1) d(-1) in October, equivalent to one half of the PIR for June and one third of the PIR for May. Average EPR was highest in May, and quite similar during the other two months. According to H values, herbivorous feeding contributed 100% of the egg production of C. sinicus in June, 82.5% in May, but only 47.8% in October. It is possible that omnivorous feeding of C. sinicus in October was induced by a prevalence of large-sized diatoms and sufficient non-phytoplankton food resources during the autumn bloom period.

Macrophysiology of Calanus finmarchicus in the North Atlantic Ocean

Copepods represent the major part of the dry weight of the mesozooplankton in pelagic ecosystems and therefore have a central role in the secondary production of the North Atlantic Ocean. The calanoid copepod species Calanus finmarchicus is the main large copepod in subarctic waters of the North Atlantic, dominating the dry weight of the mesozooplankton in regions such as the northern North Sea and the Norwegian Sea. The objective of this work was to investigate the relationships between both the fundamental and realised niches of C. finmarchicus in order to better understand the future influence of global climate change on the abundance, the spatial distribution and the phenology of this key-structural species. Based on standardised Principal Component Analyses (PCAs), a macroecological approach was applied to determine factors affecting the spatial distribution of C. finmarchicus and to characterise its realised niche. Second, an ecophysiological model was used to calculate the Potential Egg Production Rate (PEPR) of C. finmarchicus and the centre of its fundamental niche. Relationships between the two niches were then investigated by correlation analysis. We found a close relationship between the fundamental and realised niches of C. finmarchicus at spatial, monthly and decadal scales. While the species is at the centre of its niche in the subarctic gyre, our joint macroecological and macrophysiological analyses show that it is at the edge of its niche in the North Sea, making the species in this region more vulnerable to temperature changes.

Effects of stocking density on A. tonsa (Copepoda: Calanoida) culture

Dissertação de Mestrado, Aquacultura e Pescas, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2009

Efeito dos níveis de triptofano digestível em dietas para codornas japonesas em postura

The adequate level (0.12, 0.16, 0.20, 0.24, and 0.28%) of the dietary digestible tryptophan was evaluated in 400 laying Japanese quail from 21 to 30 weeks old. The animals were housed in laying cages, with initial weight of 158.50 g and egg production average of 84.50%. A completely randomized blocks design, with eight blocks, five diets, eight replicates of ten birds per replicate and three experimental periods of 21 days each was used. Feed intake (g/bird/day), digestible tryptophan intake (mg/bird/day), egg production (%/bird/day), egg weight (g), egg mass (kg/bird/day) and feed conversion (kg feed intake per kg eggs and dozen eggs) were the characteristics evaluated. Only the characteristics digestible tryptophan intake and egg production rate show significant effects of digestible tryptophan levels in the diets. Performance response of the Japanese quails in posture, regarding the adjustment obtained through models of linear regression and broken-line regression model, and the biological interpretation, allow to conclude that to obtain the best productive performance, the Japanese quails diets should contain the level of 0.21% digestible tryptophan, that results in a daily intake of 45.0 mg/ bird of digestible tryptophan, corresponding to the digestible tryptophan: digestible lysine ratio of 21%. © 2008 Sociedade Brasileira de Zootecnia.

Zooplankton carbon budget from Trondheim mesocosm experiment

We measured respiration, egg production and fecal pellet production of five common copepod species, when fed on suspended or aggregated food from two mesocosm, + NP and + NPSi. We hypothetised that calanoid copepods (Temora longicornis, Acartia spp., Centropages spp.) would feed mainly on suspended food, and have low respiration and egestion rates when food was only available as aggregates, while harpacticoids and Oncaea spp. would mainly feed on aggregated food and have low metabolic rates when only suspended food was available. Copepods were collected from the lagoon, and adapted to experimental conditions for 24 h. Food suspension was collected from the mesocosms, and either offered to copepods directly (suspended food) or after rotating in a plankton wheel until most phytoplankton was aggregated together (aggregated food). After 24-h incubation we counted the produced eggs and pellets, and measured copepod respiration using microelectrodes.

Have we been underestimating the effects of ocean acidification in zooplankton?

Understanding how copepods may respond to ocean acidification (OA) is critical for risk assessments of ocean ecology and biogeochemistry. The perception that copepods are insensitive to OA is largely based on experiments with adult females. Their apparent resilience to increased carbon dioxide (pCO2) concentrations has supported the view that copepods are 'winners' under OA. Here, we show that this conclusion is not robust, that sensitivity across different life stages is significantly misrepresented by studies solely using adult females. Stage-specific responses to pCO2 (385-6000 µatm) were studied across different life stages of a calanoid copepod, monitoring for lethal and sublethal responses. Mortality rates varied significantly across the different life stages, with nauplii showing the highest lethal effects; nauplii mortality rates increased threefold when pCO2 concentrations reached 1000 µatm (year 2100 scenario) with LC50 at 1084 µatm pCO2. In comparison, eggs, early copepodite stages, and adult males and females were not affected lethally until pCO2 concentrations >= 3000 µatm. Adverse effects on reproduction were found, with >35% decline in nauplii recruitment at 1000 µatm pCO2. This suppression of reproductive scope, coupled with the decreased survival of early stage progeny at this pCO2 concentration, has clear potential to damage population growth dynamics in this species. The disparity in responses seen across the different developmental stages emphasizes the need for a holistic life-cycle approach to make species-level projections to climate change. Significant misrepresentation and error propagation can develop from studies which attempt to project outcomes to future OA conditions solely based on single life history stage exposures.

Parental exposure to elevated pCO2 influences the reproductive success of copepods

Substantial variations are reported for egg production and hatching rates of copepods exposed to elevated carbon dioxide concentrations (pCO2). One possible explanation, as found in other marine taxa, is that prior parental exposure to elevated pCO2 (and/or decreased pH) affects reproductive performance. Previous studies have adopted two distinct approaches, either (1) expose male and female copepoda to the test pCO2/pH scenarios, or (2) solely expose egg-laying females to the tests. Although the former approach is more realistic, the majority of studies have used the latter approach. Here, we investigated the variation in egg production and hatching success of Acartia tonsa between these two experimental designs, across five different pCO2 concentrations (385-6000 µatm pCO2). In addition, to determine the effect of pCO2 on the hatching success with no prior parental exposure, eggs produced and fertilized under ambient conditions were also exposed to these pCO2 scenarios. Significant variations were found between experimental designs, with approach (1) resulting in higher impacts; here >20% difference was seen in hatching success between experiments at 1000 µatm pCO2 scenarios (2100 year scenario), and >85% at 6000 µatm pCO2. This study highlights the potential to misrepresent the reproductive response of a species to elevated pCO2 dependent on parental exposure.

Copepod vital rates under CO2-induced acidification: a calanoid species and a cyclopoid species under short-term exposures

Although copepods have been considered tolerant against the direct influence of the ocean acidification (OA) projected for the end of the century, some recent studies have challenged this view. Here, we have examined the direct impact of short-term exposure to a pCO2/pH level relevant for the year 2100 (pHNBS, control: 8.18, low pH: 7.78), on the physiological performance of two representative marine copepods: the calanoid Acartia grani and the cyclopoid Oithona davisae. Adults of both species, from laboratory cultures, were preconditioned for four consecutive days in algal suspensions (Akashiwo sanguinea) prepared with filtered sea water pre-adjusted to the targeted pH values via CO2 bubbling. We measured the feeding and respiratory activity and reproductive output of those pre-conditioned females. The largely unaffected fatty acid composition of the prey offered between OA treatments and controls supports the absence in the study of indirect OA effects (i.e. changes of food nutritional quality). Our results show no direct effect of acidification on the vital rates examined in either copepod species. Our findings are compared with results from previous short- and long-term manipulative experiments on other copepod species.

Lack of evidence for elevated CO2-induced bottom-up effects on marine copepods: a dinoflagellate-calanoid prey-predator pair

Rising levels of atmospheric CO2 are responsible for a change in the carbonate chemistry of seawater with associated pH drops (acidification) projected to reach 0.4 units from 1950 to 2100. We investigated possible indirect effects of seawater acidification on the feeding, fecundity, and hatching success of the calanoid copepod Acartia grani, mediated by potential CO2-induced changes in the nutritional characteristics of their prey. We used as prey the autotrophic dinoflagellate Heterocapsa sp., cultured at three distinct pH levels (control: 8.17, medium: 7.96, and low: 7.75) by bubbling pure CO2 via a computer automated system. Acartia grani adults collected from a laboratory culture were acclimatized for 3 d at food suspensions of Heterocapsa from each pH treatment (ca. 500 cells/ml; 300 ?g C/l). Feeding and egg production rates of the preconditioned females did not differ significantly among the three Heterocapsa diets. Egg hatching success, monitored once per day for the 72 h, did not reveal significant difference among treatments. These results are in agreement with the lack of difference in the cellular stoichiometry (C : N, C : P, and N : P ratios) and fatty acid concentration and composition encountered between the three tested Heterocapsa treatments. Our findings disagree with those of other studies using distinct types of prey, suggesting that this kind of indirect influence of acidification on copepods may be largely associated with interspecific differences among prey items with regard to their sensitivity to elevated CO2 levels.

Diatom abundance and fatty acid composition of ice algae and of Calanus glacialis in samples obtained in 2008 in the eastern Beaufort Sea

The copepod Calanus glacialis plays a key role in the lipid-based energy flux in Arctic shelf seas. By utilizing both ice algae and phytoplankton, this species is able to extend its growth season considerably in these seasonally ice-covered seas. This study investigated the impacts of the variability in timing and extent of the ice algal bloom on the reproduction and population success of C. glacialis. The vertical distribution, reproduction, amount of storage lipids, stable isotopes, fatty acid and fatty alcohol composition of C. glacialis were assessed during the Circumpolar Flaw Lead System Study. Data were collected in the Amundsen Gulf, south-eastern Beaufort Sea, from January to July 2008 with the core-sampling from March to April. The reduction in sea ice thickness and coverage observed in the Amundsen Gulf in 2007 and 2008 affected the life strategy and reproduction of C. glacialis. Developmental stages CIII and CIV dominated the overwintering population, which resulted in the presence of very few CV and females during spring 2008. Spawning began at the peak of the ice algal bloom that preceded the precocious May ice break-up. Although the main recruitment may have occurred later in the season, low abundance of females combined with a potential mismatch between egg production/development to the first feeding stage and phytoplankton bloom resulted in low recruitment of C. glacialis in the early summer of 2008.

Seawater carbonate chemistry and reproduction of the two calanoid copepods Centropages typicus and Temora longicornis in a laboratory experiment

Some planktonic groups suffer negative effects from ocean acidification (OA), although copepods might be less sensitive. We investigated the effect of predicted CO2 levels (range 480-750 ppm), on egg production and hatching success of two copepod species, Centropages typicus and Temora longicornis. In these short-term incubations there was no significant effect of high CO2 on these parameters. Additionally a very high CO2 treatment, (CO2 = 9830 ppm), representative of carbon capture and storage scenarios, resulted in a reduction of egg production rate and hatching success of C. typicus, but not T. longicornis. In conclusion, reproduction of C. typicus was more sensitive to acute elevated seawater CO2 than that of T. longicornis, but neither species was affected by exposure to CO2 levels predicted for the year 2100. The duration and seasonal timing of exposures to high pCO2, however, might have a significant effect on the reproduction success of calanoid copepods.

Ocean acidification affects the phyto-zoo plankton trophic transfer efficiency

The critical role played by copepods in ocean ecology and biogeochemistry warrants an understanding of how these animals may respond to ocean acidification (OA). Whilst an appreciation of the potential direct effects of OA, due to elevated pCO2, on copepods is improving, little is known about the indirect impacts acting via bottom-up(food quality) effects. We assessed, for the first time, the chronic effects of direct and/or indirect exposures to elevated pCO2 on the behaviour, vital rates, chemical and biochemical stoichiometry of the calanoid copepod Acartia tonsa. Bottom-up effects of elevated pCO2 caused species-specific biochemical changes to the phytoplanktonic feed, which adversely affected copepod population structure and decreased recruitment by 30 %. The direct impact of elevated pCO2 caused gender-specific respiratory responses in A.tonsa adults, stimulating an enhanced respiration rate in males (> 2-fold), and a suppressed respiratory response in females when coupled with indirect elevated pCO2 exposures. Under the combined indirect+direct exposure, carbon trophic transfer efficiency from phytoplankton-to-zooplankton declined to < 50 % of control populations, with a commensurate decrease in recruitment. For the first time an explicit role was demonstrated for biochemical stoichiometry in shaping copepod trophic dynamics. The altered biochemical composition of the CO2-exposed prey affected the biochemical stoichiometry of the copepods, which could have ramifications for production of higher tropic levels, notably fisheries. Our work indicates that the control of phytoplankton and the support of higher trophic levels involving copepods have clear potential to be adversely affected under future OA scenarios.

Data collection of Calanus finmarchicus reproduction life history traits in the North Atlantic Ocean

Observations of egg production rates (EPR) for female Calanus finmarchicus were compared from different regions of the North Atlantic. The regions were diverse in size and sampling frequency, ranging from a fixed time series station in the Lower St Lawrence Estuary, off Rimouski, where nearly 200 experiments were carried out between May and December from 1994 to 2006, to a large-scale survey in the Northern Norwegian Sea, where about 50 experiments were carried out between April and June from 2002 to 2004. For this analysis the stations were grouped mostly along geographic lines, with only limited attention being paid to oceanographic features. There is some overlap between regions, however, where stations were sometimes kept together when they were sampled on the same cruise. As well some stations other than off Rimouski were occupied more than once during different years and/or in different seasons.

O efeito do peso vivo às 17 semanas de idade de galinhas poedeiras nos parâmetros produtivos e de qualidade do ovo durante a fase de postura

Dissertação de Mestrado em Engenharia Zootécnica/Produção Animal

The effect of stress on egg quality in farmed Atlantic Cod (Gadus morhua L.)

Dissertação de mestrado, Aquacultura, Faculdade de Ciências e Tecnologia, Universidade do Algarve, 2011