Fecal Pellet Production Rates Research Articles

Calanus finmarchicus basin scale life history traits and role in community carbon turnover during spring

Abstract The copepod Calanus finmarchicus was investigated in four Subpolar Basins, Labrador, Irminger, Iceland, and Norwegian Seas, during spring, covering the time of ascent, grazing, and initiation of reproduction in the area. Lipid content, spawning activity, and stage composition and vital rates, such as egg and faecal pellet production were measured and linked to environmental parameters. Specific egg- and faecal pellet production rates varied with diatom biomass and were negatively correlated with temperature. Comparison of the various biological indicators revealed different life history traits C. finmarchicus has adopted in the different basins. In Labrador Sea, the females have invested in large eggs compared to the remaining basins. Labrador and Irminger Sea C. finmarchicus invest in size that we propose to be adaptation to cope with warmer overwintering habitats resulting in larger potential lipid storage capacity, while the Iceland and Norwegian Sea females can invest their remaining lipid storage in spring to fuel lipid-driven egg production. Grazing pressure on the phytoplankton community was estimated and compared between copepod and two dominating groups of protozooplankton; ciliates and heterotrophic dinoflagellates. Despite approximately the same biomass in the upper 100 m, the grazing impact of the protozoan grazers was an order of magnitude higher than the C. finmarchicus dominated mesozooplankton. This illustrates the importance to also include the smallest grazers when studying the spring bloom in high latitude marine ecosystems if the fate of the primary production should be fully understood.

Effects of Microalgal Food Quantity on Several Productivity-Related Parameters of the Calanoid Copepod Bestiolina similis (Calanoida: Paracalanidae)

The optimization of copepod feeding protocol is paramount to improve culture productivity and to maintain favorable water quality parameters overtime, as well as saving operational costs by preventing the production of unnecessary quantities of microalgae. The influence of microalgal feeding concentration on major parameters related to culture productivity of the calanoid copepod Bestiolina similis (Paracalanidae) was investigated in a series of laboratory experiments. B. similis was fed eight different concentrations (0, 150, 300, 600, 900, 1,200, 1,500 and 1,800 μgC l–1) of a mixed microalgal diet consisting of Tahitian strain of Isochrysis species, Pavalova 50 and Tetraselmis chuii at 1:1:1 carbon ratio. The results indicate that female daily and cumulative egg production over lifespan, egg hatching rate, naupliar and copepodite survival and development, adult female life expectancy, population growth and fecal pellet production rate (FPPR) were all significantly affected by microalgae feeding ration. Conversely, no significant influence could be established between microalgae food concentration and egg diameter or adult sex ratio. Feeding rations as low as 150 μgC l–1 led to lower egg hatching rates, survival and development, adult female life expectancy and population growth compared with the higher microalgae rations tested. Feeding concentration ≤ 900 μgC l–1 significantly limited female daily egg and fecal pellet production rate, as well as their cumulative egg production over lifespan, when compared to a level of 900 μgC l–1. Bestiolina similis fed with 1,200 μgC l–1 significantly improved female egg and fecal pellet production when compared to the lower treatments and was responsible for the highest female lifespan egg production and population growth observed among all treatments. Feeding rations as high as 1,500 μgC l–1 and 1,800 μgC l–1 did not lead to significant improvement in any of the parameters measured. This is likely due to a saturation effect at high food concentration which is known to decrease calanoid copepods feeding efficiency. Finally, B. similis FPPR, used as a proxy for ingestion, was found to saturate at a microalgae concentration of 783.4 μgC l–1 using a non-linear Michael-Menton (2 parameters), indicating that CVI female ingestion did not increase significantly above this concentration. Based on the above results it is recommended that B. similis cultures should be fed at a concentration of 1,200 μgC l–1, and not above, as rations > 1,200 μgC l–1 will not significantly improve any of the productivity-related parameters observed in this study. Feeding rations should never be below 783.40 μgC l–1 as this is the threshold level below which adult female ingestion rates become limiting.

Ingestion and impact of microplastics on arctic Calanus copepods

Microplastics (MPs) are contaminants of emerging concern in the Arctic, but knowledge of their potential effects on Arctic plankton food webs remains scarce. We experimentally investigated ingestion and effects of MPs (20 μm polyethylene spheres) on the arctic copepods Calanus finmarchicus, C. glacialis and C. hyperboreus. These species dominate arctic zooplankton biomass and are relevant target species to investigate the potential impacts of MPs on the Arctic marine ecosystem. Females of each species were exposed to two concentrations of MPs (200 and 20,000 MPs L−1) in combination with different food (diatom) concentrations, reflecting high (3000–5000 cells mL−1, spring phytoplankton bloom) and low (50–500 cells mL−1, pre/post bloom) food conditions. MPs did not affect negatively fecal pellet production rates in any of the species at the studied exposure concentrations. However, egg production rates of copepods exposed to MPs were 8 times higher compared with the controls, which suggests that MP exposure can cause stress-induced spawning in arctic copepods. Microscopic examination of the fecal pellets confirmed ingested MPs in the three species (up to aprox. 1000 MPs cop−1 d−1). The number of MPs per pellet decreased exponentially with increasing food concentration. The daily ingestion of MPs per copepod was higher at low- food concentrations (250–500 cells mL−1). At our exposure conditions, the presence of MPs inside C. hyperboreus fecal pellets did not affect their sinking rates. Overall, our experimental research show that 1) acute exposure to virgin polyethylene MPs has a low impact on arctic Calanus species at environmentally relevant MP concentrations, independent of food availability, and 2) arctic copepods influence the environmental fate of plankton-sized MPs by exporting buoyant MPs from the surface layer to the sea floor via fecal pellets.

Microplastics do not increase bioaccumulation of petroleum hydrocarbons in Arctic zooplankton but trigger feeding suppression under co-exposure conditions

Arctic sea ice has alarmingly high concentrations of microplastics (MPs). Additionally, sea ice reduction in the Arctic is opening new opportunities for the oil and maritime industries, which could increase oil pollution in the region. Yet knowledge of the effects of co-exposure to MPs and crude oil on Arctic zooplankton is lacking. We tested the influence of MPs (polyethylene, 20.7 μm) on polycyclic aromatic hydrocarbon (PAH) bioaccumulation and oil toxicity in the key arctic copepod Calanus hyperboreus after exposure to oil with and without dispersant. Up to 30% of the copepods stopped feeding and fecal pellet production rates were reduced after co-exposure to oil (1 μL L−1) and MPs (20 MPs mL−1). The PAH body burden was ~3 times higher in feeding than in non-feeding copepods. Copepods ingested both MPs and crude oil droplets. MPs did not influence bioaccumulation of PAHs in copepods or their fecal pellets, but chemical dispersant increased bioaccumulation, especially of ≥4 ring-PAHs. Our results suggest that MPs do not act as vectors of PAHs in Arctic marine food webs after oil spills, but, at high concentrations (20 MPs mL−1), MPs can trigger behavioral stress responses (e.g., feeding suppression) to oil pollution in zooplankton.

Grazing rates of freshwater copepod Thermocyclops decipiens (Kiefer, 1929) on Chlorella vulgaris under different light intensities

Light is one of the most important structuring factors for life in aquactic biology. For zooplankton grazers, including copepods, light offers a behavioral dilemma that is potentially present at both small and large scales. We investigated the grazing rate, clearance rate, fecal pellet production rate, egg production rate, percertage of egg hatching and survival percentage of the freshwater copepod Thermocyclops deceipiens under different light intensities (0 lx, 500 lx, 1500 lx) over periods of 15 days. For the grazing experiment the fresh water microalgae Chlorella vulgaris was used at concentrations 2–6 × 106 cells/mL−1. The grazing rates of the copepod decreased at higher light intensities when compared to other treatments. Maximum grazing rate and the clearance rate occurred in the treatment with 500 lx (70,490 cells copepod−1 h−1, 0.23 mL copepod−1 h−1). Egg production rate and hatching rate percentage (17.4 eggs female−1 day−1, 99 ± 0.98%) were also higher at the algae fed with 500 lx light intensity. Copepods survived well and continuously produced fecal pellets on a 500 lx light intensity diet of Chlorella vulgaris. The results suggest that low light intensity influenced the grazing rate, fecundity and survival of copepod T.decipiens.

Ecology of Pseudodiaptomus annandalei in tropical aquaculture ponds with emphasis on the limitation of production

ABSTRACT The calanoid copepod Pseudodiaptomus annandalei is used as live feed in aquaculture because of its nutritional value and the ability to cope with environmental fluctuations in outdoor ponds. However, little knowledge exists on its ecology. Here we investigated the ecology of P. annandalei in an aquaculture pond in Vietnam. Temperature, salinity, chlorophyll a and biomass of protozoans and copepods were monitored every other day for 1 month. Experiments on protozoan growth and grazing by P. annandalei were also conducted. Copepod fecal pellet production and temperature-dependent egg hatching rates were likewise quantified. Despite very high phytoplankton biomass, biomass of P. annandalei was surprisingly low. Copepod production was estimated from three independent methods: clearance, weight-specific egg production rate (SEP) and specific fecal pellet production rate. SEP proved to be accurate to predict the in situ population growth in the pond. A simple model for production of P. annandalei based on SEP was developed. Our study extends our knowledge of how environmental conditions in the pond may affect the population dynamics and production of copepods. The results have important implications for pond managements ensuring stable copepod production and harvest.

The potential contributions of phytoplankton cells and zooplankton fecal pellets to POC export fluxes during a spring bloom in the East China Sea

Sinking particles are mainly composed of phytoplankton cells and zooplankton fecal pellets, but the proportions of these sources contribute to the overall particulate organic carbon (POC) flux are highly variable temporally and spatially. Here, we report for the first time simultaneous estimates of the POC fluxes from phytoplankton cells and zooplankton fecal pellets during a spring bloom in the East China Sea. The sinking rate of phytoplankton during the bloom event was 12 ± 2 m d–1, which was more than 10 times the rate at non-bloom stations (1.0 ± 0.8 m d–1). Microscopic observations indicated that the formation of aggregates by the Prorocentrum donghaiense (the dominant phytoplankton species) enhanced the sinking rates during the bloom. These enhanced sinking rates and 10 times higher phytoplankton biomass during the bloom increased POC fluxes to as high as 24 g C m–2 d–1, about 100 times the rate at reference non-bloom stations (0.26 g C m–2 d–1). The POC flux of fecal pellets at bloom stations (0.95–1.4 g C m–2 d–1) increased to only about 6 times the rates at non-bloom stations (0.20–0.25 g C m–2 d–1). The fecal pellet POC flux was mainly enhanced by the increase of phytoplankton abundance, which led to higher mesozooplankton grazing rates and fecal pellet production rates during the bloom. In summary, the majority of the enhanced sinking POC flux during the bloom was directly associated with phytoplankton sinking. This enhanced flux sequestered carbon faster than anticipated because of the enhancements of both phytoplankton sinking rates and abundance. Such dramatic, albeit brief, events make very important potential contributions to the annual POC flux.

Bioenergetics of the copepod Temora longicornis under different nutrient regimes

The copepod Temora longicornis depends on constant prey availability, but its performance also depends on how efficiently it utilizes its food sources. Our research goal was to understand copepod energy allocation in relation to diet quality. The working hypothesis was that Temora performs better on the diet whose elemental ratio is closest to its own. Diatoms (Diat) and dinoflagellates (Dino) cultured in nutrient-replete (+) and nitrogen-depleted (-) conditions were fed to the copepods. Ingestion, respiration, excretion and egg and fecal pellet production rates were measured. Carbon (C) and nitrogen (N) budgets were built to investigate differences in dietary C and N partitioning. Copepods fed nitrogen-depleted diatoms (Diat-), which had the most different C: N ratio to that of Temora longicornis, had high metabolic losses and low growth. Copepods fed nitrogen-rich dinoflagellates (Dino+) with a more similar C: N ratio to their own also had high metabolic losses, but displayed the highest investment into somatic growth and egg production. The results indicate that dinoflagellates are a better food source for T. longicornis. Furthermore, consumption of low-quality food leads to higher respiration rates and faster leakage of dissolved organic carbon from copepod fecal pellets; and egestion is a main pathway in copepods for eliminating unabsorbed and non-metabolized carbon.

Laboratory screening of thermo-mechanically densified and thermally modified timbers for resistance to the marine borer Limnoria quadripunctata

Thermo-mechanically densified material of five different wood species (English oak, European ash, European beech, Norway spruce, poplar) was subjected to three different vacuum-heat treatment processes (A 230 °C/20% vacuum; B 230 °C/80% vacuum; C 240 °C/20% vacuum) and tested for its resistance against the marine borer Limnoria quadripunctata by comparing their faecal pellet production rates. The three different treatments caused a notable reduction in the feeding rates of up to 66% indicating significantly increased durability against Limnoria if exposed to marine environment. Neither the treatment temperature nor the application of a higher vacuum affected the faecal pellet production significantly.

Carbon flow through the pelagic food web in southern Chilean Patagonia: relevance of Euphausia vallentini as a key species

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 557:91-110 (2016) - DOI: https://doi.org/10.3354/meps11826 Carbon flow through the pelagic food web in southern Chilean Patagonia: relevance of Euphausia vallentini as a key species H. E. González1,2,*, M. Graeve4, G. Kattner4, N. Silva5, L. Castro6,7, J. L. Iriarte2,3,7,8, L. Osmán9, G. Daneri3,7, C. A. Vargas10 1Universidad Austral de Chile, Instituto de Ciencias Marinas y Limnológicas, Valdivia, Chile 2Centro FONDAP de Investigación de Ecosistemas Marinos de Altas Latitudes (IDEAL), Universidad Austral de Chile, Valdivia, Chile 3Centro de Investigación de Ecosistemas de la Patagonia (CIEP), Coyhaique, Chile 4Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Bremerhaven, Germany 5Escuela de Ciencias del Mar, P. Universidad Católica de Valparaíso, Valparaíso, Chile 6Departamento de Oceanografía, Universidad de Concepción, Concepción, Chile 7Centro COPAS-Sur Austral, Universidad de Concepción, Concepción, Chile 8Universidad Austral de Chile, Instituto Acuicultura, Puerto Montt, Chile 9The Nature Conservancy, Los Helechos 635, Valdivia, Chile 10Departamento de Sistemas Acuáticos, Facultad de Ciencias Ambientales, Millennium Institute of Oceanography (IMO), and Center for the Study of Multiple-Drivers on Marine Socio-Ecological Systems (MUSELS), Universidad de Concepción, Concepción, Chile *Corresponding author: hgonzale@uach.cl ABSTRACT: The southernmost Patagonian region constitutes a major glaciered area with a high freshwater input loaded with particulate and dissolved matter. We assessed the relevance of the terrestrial (allochthonous) and marine (autochthonous) matter that permeates into the fjord and channel system and their possible impact on the euphausiid-based food web. A research cruise (CIMAR 16) was conducted from 18 October to 13 November 2010 (austral spring) in the area between Magellan Strait and Drake Passage to study the physical-chemical and biological characteristics of the pelagic food web, as well as the main biological processes linked with the food web. The dominance of phytoplankton within the autochthonous fractions of particulate organic carbon (POC) and the high abundance and bacterivory rate shown by the heterotrophic nanoflagellates suggest an interplay between microbial and classical food webs. Euphausia vallentini showed a moderate grazing impact (3% of the gross primary production) and a daily ration of 18.6%, and the fecal pellet production rate corresponded to 24.5% of the ingestion rate. This species removed heterotrophic prey (67.5%) preferentially over diatoms (32.5%), and the ingested diet was mainly dinoflagellates, tintinnids, crustacean nauplii and centric diatoms. Overall, euphausiids fed preferentially on marine matter, which showed a tight link with the pelagic food web. Congeneric species of the genus Euphausia shared the condition of ‘key species’ as they constitute a major carbon and energy flow from lower to higher trophic levels and an important part of the POC flux through their active vertical migration and passive fecal-carbon export. KEY WORDS: Chilean Patagonia · Euphausia vallentini · Pelagic carbon flux · Euphausiid diet Full text in pdf format Supplementary material PreviousNextCite this article as: González HE, Graeve M, Kattner G, Silva N and others (2016) Carbon flow through the pelagic food web in southern Chilean Patagonia: relevance of Euphausia vallentini as a key species. Mar Ecol Prog Ser 557:91-110. https://doi.org/10.3354/meps11826 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 557. Online publication date: September 28, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

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.

Effect of Diatom Silica Content on Copepod Grazing, Growth and Reproduction

Diatoms are often a major food source for zooplankton and contribute significantly to vertical POC flux through sinking of dead cells, aggregates and zooplankton fecal pellets. The silica content of diatoms varies among different species and within a species growing under different environmental conditions and physiological status. However, to-date there has been no investigation of the effect of diatom silica content on zooplankton grazing, growth and reproduction. We conducted a series of experiments using the diatom Thalassiosira weissflogii with different silica content achieved by growth under high and low light and these cells were fed to a copepod, Parvocalanus crassirostris. Our results show that this copepod strongly preferred cells with low silica content over high silica-containing cells, with the ingestion rate on low silica diatoms being 2-3 times higher than that on high silica diatoms. Fecal pellet production rate was significantly higher for copepods feeding on highly silicified cells. Furthermore, copepod growth rate (measured as an increase in wet weight), egg production rate and hatching success were all severely compromised under a high silica diatom diet. Females of P. crassirostris feeding on a low silica diatom diet produced an average 90 eggs during a one day incubation, while those fed with high silica diatoms produced only 11 eggs per day. Similarly, the hatching success during a 3-day period was 82 ± 17% and 23 ± 36% for the low and high silica diatom treatments, respectively, with zero success observed in ~65% of the females feeding on high Si diatoms. Our findings have important ecological implications for the biological pump and may alter our previous view of the role of diatoms in planktonic food webs and the role of the degree of silicification in controlling amount of POC flux to deeper waters.

Effects of salinity on egg and fecal pellet production, development and survival, adult sex ratio and total life span in the calanoid copepod, Acartia tonsa: a laboratory study

The effects of salinity on the copepod, Acartia tonsa in terms of daily egg production rate (EPR), hatching success, fecal pellet production rate (FPR), naupliar development time and survival, sex ratio, and total life span were determined in laboratory conditions through three experiments. In experiment 1, EPR, hatching success, and FPR of individual females were monitored at salinities of 13, 20, 35 and 45 during short-periods (seven consecutive days). Results show EPR was affected by salinity with the highest outputs recorded at 20 and 35, respectively, which were considerably higher than those at 13 and 45. Mean FPR was also higher in 35 and 20. In experiment 2, the same parameters were evaluated over total life span of females (long-term study). The best EPR and FPR were observed in 35, which was statistically higher than at 13 and 20. In experiment 3, survival rates of early nauplii until adult stage were lowest at a salinity of 13. The development time increased with increasing of salinity. Female percentage clearly decreased with increasing salinity. Higher female percentages (56.7% and 52.2%, respectively) were significantly observed at two salinities of 13 and 20 compared to that at 35 (25%). Total longevity of females was not affected by salinity increment. Based on our results, for mass culture we recommend that a salinity of 35 be adopted due to higher reproductive performances, better feeding, and faster development of A. tonsa.

Size as the master trait in modeled copepod fecal pellet carbon flux

AbstractZooplankton fecal pellet flux is a highly variable component of the biological carbon pump. While fecal pellets can comprise 0 to nearly 100% of particulate organic carbon collected in sediment traps, mechanisms for this variability remain poorly understood. Fecal pellet carbon flux is a complex function of several variables. We present a model that incorporates individual‐scale metabolic processes to determine fecal pellet production rate, the relationship between body size and fecal pellet size, the relationship between fecal pellet size and sinking rate, and a function representing the breakdown of particles in the water column. When applied to copepod communities sampled by the continuous plankton recorder in the Gulf of Maine over 25 years, a seasonal pattern of fecal pellet carbon flux emerges. The interannual flux time series produced by the model reflects known oceanographic perturbations and shows how organism‐scale processes can be scaled up to explain ecosystem level variability. We conclude that fecal pellet carbon flux in the Gulf of Maine is driven by copepod community size structure and copepod abundance, and that the fraction of fecal pellet carbon that reaches depth is a function of copepod size, rather than abundance. Changes in the physical environment which alter the size composition of the copepod community lead to variability in fecal pellet carbon flux. Our results indicate that incorporating size composition into biogeochemical models can more accurately constrain zooplankton‐mediated carbon flux.

Thermal response of ingestion and egestion rates in the Arctic copepod Calanus glacialis and possible metabolic consequences in a warming ocean

Climate change is particularly rapid in the Arctic, where water temperatures are predicted to increase substantially with implications for Arctic marine organisms, especially ectotherms such as the calanoid copepod Calanus glacialis, a key herbivore in the Arctic marine ecosystem. Feeding depends on temperature, and recent studies indicate different thermal responses in ingestion and respiration implying a possible metabolic mismatch with increasing temperatures. We investigated the thermal response of ingestion and faecal pellet production as an indicator of egestion of the Arctic copepod C. glacialis in incubation experiments at five temperatures ranging from 0 to 10 °C and compared the obtained data with published results on temperature dependence of respiration. Copepods were fed ad libitum with the diatom Thalassiosira gravida, and algae concentration was assessed prior and after 4 h feeding experiments. Egested faecal pellets were collected and counted. Ingestion and faecal pellet production rates increased linearly (Q 10 coefficient ~1.4–1.7 and ~1.8–4.1, respectively). No pronounced effect of feeding history (fed vs. starved for 3 days prior to experiment) was found, but responses in both rates were generally less dependent on temperature in the pre-starved experiment. Q 10 values for ingestion rates were lower than Q 10 values for published respiration rates (~1.8–4.6), indicating that metabolic losses increase stronger with increasing temperature than metabolic gains by ingestion. A persistent imbalance between metabolic losses and energy uptake could lead to reduced fitness for C. glacialis, thereby affecting the population dynamics and distribution of this important species in the Arctic.

Ingestion and sublethal effects of physically and chemically dispersed crude oil on marine planktonic copepods.

Planktonic copepods play a key function in marine ecosystems, however, little is known about the effects of dispersants and chemically dispersed crude oil on these important planktonic organisms. We examined the potential for the copepods Acartia tonsa, Temora turbinata and Parvocalanus crassirostris to ingest crude oil droplets and determined the acute toxicity of the dispersant Corexit® 9500A, and physically and chemically dispersed crude oil to these copepods. We detected ingestion of crude oil droplets by adults and nauplii of the three copepod species. Exposure to crude oil alone (1 µL L−1, 48 h) caused a reduction of egg production rates (EPRs) by 26–39 %, fecal pellet production rates (PPRs) by 11–27 %, and egg hatching (EH) by 1–38 % compared to the controls, depending on the species. Dispersant alone (0.05 µL L−1, 48 h) produced a reduction in EPR, PPR and EH by 20–35, 12–23 and 2–11 %, respectively. Dispersant-treated crude oil was the most toxic treatment, ~1.6 times more toxic than crude oil alone, causing a reduction in EPR, PPR and EH by 45–54, 28–41 and 11–31 %, respectively. Our results indicate that low concentrations of dispersant Corexit 9500A and chemically dispersed crude oil are toxic to marine zooplankton, and that the ingestion of crude oil droplets by copepods may be an important route by which crude oil pollution can enter marine food webs.

Oxygen consumption rates of fecal pellets produced by three coastal copepod species fed with a diatom Thalassiosira pseudonana

Fecal pellet production rate and oxygen consumption rate of copepod fecal pellets egested by Paracalanus sp., Acartia spinicauda and Centropages orsinii feeding on a diatom Thalassiosira pseudonana were measured. Fecal pellet production rates varied between 3.6 and 80.6 pellets ind −1 d −1 among three species, with fecal pellet production of Paracalanus sp. significantly higher than the other two copepod species. Average pellet size varied between 2.82 × 10 5 μm 3 for Paracalanus sp. and 5.36 × 10 5 μm 3 for A. spinicauda. Average volumetric oxygen consumption rates were 27.32, 5.84 and 45 fmol O 2 μm −3 d −1 for fecal pellets produced by Paracalanus sp., A. spinicauda and C. orsinii, respectively. The potential oxygen consumption of fecal pellets egested from Paracalanus sp. was the highest due to its high fecal pellet production rate and high population abundance throughout the year. Overall, the approximate in situ oxygen consumption due to copepod fecal pellet degradation was significant in estuarine and coastal waters of Hong Kong. Results of this study give insight of the role of zooplankton in potential occurrence of hypoxia in coastal waters during summer.

Prymnesium parvum exotoxins affect the grazing and viability of the calanoid copepod Eurytemora affinis

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 361:191-202 (2008) - DOI: https://doi.org/10.3354/meps07374 Prymnesium parvum exotoxins affect the grazing and viability of the calanoid copepod Eurytemora affinis Sanna Sopanen1,*, Marja Koski2, Pauliina Uronen1,3, Pirjo Kuuppo1, Sirpa Lehtinen1, Catherine Legrand4, Timo Tamminen1 1Finnish Environment Institute, PO Box 140, 00251 Helsinki, Finland 2Danish Institute for Fisheries Research, Kavalergården 6, Charlottenlund 2920, Denmark 3Tvärminne Zoological Station, 10900 Hanko, Finland 4Marine Sciences Division, University of Kalmar, Kalmar 39182, Sweden *Email: sanna.sopanen@environment.fi ABSTRACT: The calanoid copepod Eurytemora affinis from the northern Baltic Sea was exposed to cell-free filtrates of the toxic haptophyte Prymnesium parvum as well as to cell mixtures of P. parvum and Rhodomonas salina. To test the effects of P. parvum exudates and allelopathy on selective grazers, copepods were incubated (1) in increasing concentrations of cell-free filtrates of P. parvum in the presence of good food (R. salina), (2) in 1:1 cell mixtures at 2 cell concentrations of P. parvum and R. salina and (3) in R. salina cell suspension, which was used as a control for good-quality food. P. parvum cultures were grown in nutrient-balanced (+NP) or limited (–N or –P) media to obtain different levels of toxicity. Survival, ingestion, faecal pellet production rates and egg production were measured over 3 d, together with measurements of P. parvum toxicity (hemolytic activity) (HA). Most of the copepods incubated in high-filtrate concentrations died or became severely impaired, although (HA) in filtrates was under the detection limit. Further, the ingestion and faecal pellet production rates were suppressed in the highest filtrate concentrations in nutrient-limited treatments. Higher cell density in cell mixtures resulted in significantly lower faecal pellet production, although survival remained high. Our results show that HA is not a good overall indicator of the total harmful effects of P. parvum on grazers. Besides monospecific P. parvum diets, filtrates and cell mixtures have negative effects on grazers, and these effects are stronger under nutrient-depleted conditions; however, the presence of good-quality food lowers harmful effects for copepods. The negative effects caused either by direct intoxication or by food limitation following from strong allelopathic effects of P. parvum on other components of nano- and microplankton suggest that P. parvum blooms have a realistic potential to be deleterious for copepod secondary production, irrespective of the presence of alternative food sources. KEY WORDS: Prymnesium parvum · Exotoxins · Hemolytic activity · Eurytemora affinis · Viability · Feeding · Faecal pellet production · Egg production rate Full text in pdf format PreviousNextCite this article as: Sopanen S, Koski M, Uronen P, Kuuppo P, Lehtinen S, Legrand C, Tamminen T (2008) Prymnesium parvum exotoxins affect the grazing and viability of the calanoid copepod Eurytemora affinis. Mar Ecol Prog Ser 361:191-202. https://doi.org/10.3354/meps07374 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 361. Online publication date: June 09, 2008 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2008 Inter-Research.

Physiological response of the copepod Pseudocalanus sp. in the Baltic Sea at different thermal scenarios

AbstractWe studied the physiological response of Pseudocalanus sp. under four different temperature elevation regimes: +0, +2, +4 and +6 °C above the decadal average temperature in the Western Baltic Sea. We measured fecal pellet (FP) production rates, which was taken as a proxy of ingestion, egg production (EPR) and respiration rates. Experiments lasted from mid‐February to end April, corresponding most of the observations to the postspring bloom phase. We combined small scale incubations with the use of big (ca. 1400 L) mesocosms, which have previously been shown to be appropriate when studying phyto‐ and zooplankton succession, and the water used for the incubations was taken from the mesocosm tanks. Given that the phytoplankton succession varied between the four thermal scenarios, we evaluated (excepting in the case of the respiration rates, where incubations were carried out using 0.2 μm filtered water) both the temperature and the associated food concentration effects. Respiration and ingestion rates were found to increase with temperature. As for EPR, they also increased with temperature during the bloom, but remained at low and constant values during the postbloom in all the four treatments due to the food limitation. Linked to the temperature rise, we also detected an increase in instantaneous mortality rates and a reduction in the net growth efficiency. Finally, we discuss the potential implications of our findings for the spring phyto‐ and zooplankton succession under the forecasted climate warming, as well as for the fisheries in the Baltic Sea, where Pseudocalanus sp. is a key species.

Collapse of Calanus chilensis reproduction in a marine environment with high diatom concentration

Variations of egg production rate (EPR), hatching success (HS), production of abnormal larvae (AL) and histology of gonads have been investigated with Calanus chilensis females sampled weekly, from late November to December 2004, at a station located in the coastal zone off Dichato (Chile), at time diatom concentration in phytoplankton bloom was high. Weekly EPR estimate in nature did not change significantly during this period. It remained close to normal values (25–40 eggs/female/day), whereas HS was constantly low and high proportions of AL were observed. In parallel, bioassays revealed that EPR was strongly depressed by artificially enriched diets, corresponding to natural diatom assemblages (NDA) occurring in the field, while abnormal HS and AL values could not be improved. Ingestion of diatoms by females was estimated by faecal pellet production rates and SEM examination of diatom remains in pellet samples. Low HS and the high amounts of abnormal larvae were not reversible when females were offered a favourable food, the dinoflagellate P. minimum (PM). Minor cell degradations were observed in gonads of females fed NDA diets. In comparison with other environments, present results show that impairment of Calanoid copepod reproductive factors can occur at both high and low diatom concentrations, depending on maternal diets and diatom species in blooms.