Abundant Copepod Species Research Articles

Diet composition of the Mediterranean horse mackerel, Trachurus mediterraneus (Steindachner, 1868) (Osteichthyes: Carangidae), from the Aegean Sea

Data on feeding habits in aquatic ecosystems are of great importance in determining the role that a certain fish species plays in its habitat and in related ecosystems. In this study, the diet composition of Mediterranean horse mackerel, Trachurus mediterraneus was investigated for 728 specimens from the central Aegean Sea to compare our data with those from other regions of the Mediterranean Sea and throughout all four seasons. Catches from five major groups were identified. Crustaceans (particularly copepods) proved to be the most important food item considering the index of relative importance (IRI). At least 58 different copepod species were identified. Abundant copepod species that occur in every season were Corycaeus sp., Oncaea media, Oncaea spp., Isias clavipes, Euterpina acutifrons and Oithona nana. Isias clavipes occurred only in spring, with all of them appearing in the diet with a %IRI >10. Although found in a relatively smaller quantity, teleost larvae ranked as the second most important prey in the overall diet, with increasing quantities in fish larger than 18.0 cm.

From Phenotypes to Genotypes and Back: Toward an Integrated Evaluation of Biodiversity in Calanoid Copepods

Zooplankton molecular analyses allow for accurate species identification with a proper molecular signature, complementing classic phenotypic-based taxonomy (α taxonomy). For the first time in the Mediterranean Sea, cytochrome oxidase I (COI) gene sequences of calanoid copepods were associated with morphological identification, HD and SEM images, using a fully integrated approach to assess taxonomic diversity. Such method was applied to selected species, generating consensus sequences from the Gulf of Naples (Central Tyrrhenian Sea, Western Mediterranean Sea) also including reference barcodes of three target species (Nannocalanus minor, Pleuromamma gracilis and the non-indigenous species (NIS) Pseudodiaptomus marinus) that are new for the Mediterranean area. The new barcodes were selected including: dominant and rare species; species that were originally described in the study area as type locality, but lacking a molecular description; emergent NIS and potential species complex. The integration between morphological and molecular identification by tree placement, using species-specific highly conserved oligonucleotides, also provided new and high-quality references of the most common and abundant copepod genera and species in the Mediterranean Sea. Our regional reference library was then integrated and analyzed with global data reference available on BOLD database to explore the presence of potential cryptic species and biogeographic patterns and links among geographically distant populations of copepods. Overall, this study provides valuable insight into the actual copepod taxonomic diversity and contributes to building baseline knowledge to monitor coastal biodiversity in neritic areas worldwide, where copepods are of paramount ecological importance, paving the way for future metabarcoding studies.

Demrek Baraj Gölü (Kırıkhan, Hatay) Zooplankton Faunası

The annual average of Secchi disk depth (100.42 ±38. 99 cm), water temperature (21.06±5.96 ºC), dissolved oxygen (8.33±0.99 mg/l), nitrate (0.43±0.19 mg/l), nitrite (0.02±0.01), hardness (172±17.27 mg/l), silica (1.17±0.28 mg/l), phosphate (0.14±0.03 mg/l), organic phosphate (1.09 ±0.56 mg/l) and chlorophyll-a (0.05±0.03 mg /l) were detected and according to these values, it was determined that the reservoir water has eutrophic and hyperneurophic character. Rotifera had the highest proportion with 45 taxa, followed by Cladocera with 11 species and Copepoda with 7 species. Asplanchna priodonta, Keratella cochlearis, Polyarthra dolichoptera, Sychaeta stylata Bosmina longirostris, Diaphanosoma birgei, and Disparalona rostrata were present throughout the whole study period. The most abundant species from Rotifera was Sychaeta stylata (26034±56482.24 ind./m3) followed by Polyarthra dolichoptera (15356±9593.48 ind./m3) and Keratella cochlearis (11850±15441.51 ind./m3). In the study, the most common species belonging to Cladocera was Ceriodaphnia pulchella (7042±6759.93 ind./m3) and the most abundant copepod species was Cyclops vicinus (2553±1596.48 ind./m3).

The large-bodied copepods off Masirah Island, Oman: An investigation of Southwest Monsoon onset and die-off

Abstract Masirah Island, situated off the southern coast of Oman in the Arabian Sea, is surrounded by upwelled water during the Southwest Monsoon (SWM) and was used as a base for time-series studies of the copepod community for a decade beginning in 2006, covering the Spring Intermonsoon (SIM), April–May, and including June, and the SWM period, August–October. Subeucalanus pileatus and Calanoides natalis were the two most abundant copepod species (33.9% and 32.7% respectively of the total abundances). These two species shifted their dominance during the two main seasonal periods. During the SWM, C. natalis was the dominant species occurring mainly at sea surface temperatures (SST) between 18 and 27 °C while S. pileatus dominated during the SIM occurring at warmer SSTs, frequently between 25 and 28 °C. Results from generalized linear models indicated that the season and the SST were the best predicted variables affecting the abundances of C. natalis and S. pileatus. Calanoides carinatus was also affected by wind speed and wind direction, meaning that strong SWM winds and low temperatures (seasonal upwelling) favor the occurrence of this species. Upwelling favorable winds lasted longer in 2015/2016 than in 2009/2010; peak winds shifted from June in 2009–2011 to July in 2012–2016. The SST was higher in 2016 than in the previous five years. Time-series of C. natalis life stages showed three large peaks of early copepodites from June through September 2016 during the SWM season, in contrast to only one peak observed at the beginning of the SWM season from previous years. This result suggests that C. natalis was able to capitalize on the longer SWM in 2016 by continuing to reproduce throughout September. Diapausing C. natalis reached the surface in mid-to-late June as stage CV, ruling out any reproduction by this species at its overwintering depth. Unfavorable SST at the end of the SWM corresponded to a downward migration by C. natalis in 2015. Overall, the physical forcing of this upwelling region appears to be changing and C. natalis seems to be adapting to these changing conditions by continuing to reproduce at the surface as long as SST is favorable.

Predatory efficacy of five locally available copepods on Aedes larvae under laboratory settings: An approach towards bio-control of dengue in Sri Lanka.

Many countries are in search of more effective and sustainable methods for controlling dengue vectors, due to undeniable inefficiencies in chemical and mechanical vector control methods. Bio-control of vectors by copepods is an ideal method of using interactions in the natural ecosystem for vector management, with minimum consequences on the environment. Current study determined the predatory efficacy of five locally abundant copepod species on, Aedes larvae under laboratory conditions. Copepods were collected from the pre-identified locations within the districts of Gampaha and Kandy, and identified morphologically. Individual species of copepods were maintained as separate colonies with Paramecium culture and wheat grain as supplementary food. Five adult copepods of each species was introduced into separate containers with 200 larvae (1st instar) of Aedes aegypti. Number of larvae survived in containers were enumerated at 3 hour intervals within a duration of 24 hours. Each experiment was repeated five times. The same procedure was followed for Ae. albopictus. Significance in the variations among predation rates was evaluated with General Linear Modelling (GLM) followed by Tukey’s pair-wise comparison in SPSS (version 23). Significant variations in predation rates of studied copepod species were reported (p<0.05), whereby M. leuckarti indicated the highest followed by M. scrassus, while C. languides indicated the lowest predatory efficacy. The effect of different Aedes larval species on the predation rates of copepods remained significant (p<0.05), even though the effect on predatory efficiency was not significant. Based on the findings, both M. leuckarti and M. scrassus, with the highest predatory efficiencies, could be recommended as potential candidates for biological controlling of Aedes vectors in Sri Lanka.

Stable isotope compositions of dominant zooplankton species in relation to environmental factors in the Dardanelles

Samples were collected seasonally from three stations in the Dardanelles between April 2016 and October 2017 to determine the effects of biological and physicochemical properties of the coastal system on the isotopic compositions of the most abundant copepod species, Acartia clausi and Calanus helgolandicus, and a cladoceran, Penilia avirostris. Plankton samples were collected horizontally with a 200-?m-mesh plankton net and isotopic analyses were performed by mass spectrometry after identification to species level. Total zooplankton abundance reached its maximum in spring and summer. The ?13C values of copepods showed statistically significant differences both between stations and seasons. As a selective feeder, C. helgolandicus had the highest values in both ?13C and ?15N. Being a filter feeder, P. avirostris distinctly differed from C. helgolandicus and A. clausi. Enrichment was observed in ?15N values of copepods in winter, when the highest values of total suspended solids and chlorophyll-a were determined. The results showed that ?13C values of the copepods were under the influence of environmental and biological factors. Additionally, dietary differences between herbivorous groups and other groups were clearly demonstrated, as well as differences in the diets of filter-feeding and selectively-feeding zooplanktonic species.

Zooplankton From a Reef System Under the Influence of the Amazon River Plume.

At the mouth of the Amazon River, a widespread carbonate ecosystem exists below the river plume, generating a hard-bottom reef (∼9500 km2) that includes mainly large sponges but also rhodolith beds. The mesozooplankton associated with the pelagic realm over the reef formation was characterized, considering the estuarine plume and oceanic influence. Vertical hauls were carried out using a standard plankton net with 200 μm mesh size during September 2014. An indicator index was applied to express species importance as ecological indicators in community. Information on functional traits was gathered for the most abundant copepod species. Overall, 179 zooplankton taxa were recorded. Copepods were the richest (92 species), most diverse and most abundant group, whereas meroplankton were rare and less abundant. Species diversity (>3.0 bits.ind-1) and evenness (>0.6) were high, indicating a complex community. Small holoplanktonic species dominated the zooplankton, and the total density varied from 107.98 ind. m-3 over the reef area to 2,609.24 ind. m-3 in the estuarine plume, with a significant difference between coastal and oceanic areas. The most abundant copepods were the coastal species ithona plumifera and Clausocalanus furcatus and early stages copepodites of Paracalanidae. The holoplanktonic Oikopleura, an important producer of mucous houses, was very abundant on the reefs. The indicator species index revealed three groups: (1) indicative of coastal waters under the influence of the estuarine plume [Euterpina acutifrons, Parvocalanus crassirostris, Oikopleura (Vexillaria) dioica and Hydromedusae]; (2) characterized coastal and oceanic conditions (Clausocalanus); (3) characterized the reef system (O. plumifera). Two major copepods functional groups were identified and sorted according to their trophic strategy and coastal-oceanic distribution. The species that dominated the coastal area and the area over the rhodolith beds are indicators of the estuarine plume and are mixed with species of the North Brazil Current. These species practically disappear offshore, where occur oceanic species commonly found in other oligotrophic tropical areas. This ecosystem shows a mixture of estuarine, coastal and oceanic communities coexisting in the waters over the Amazon reefs, with no significant differences among these areas. However, the MDS clearly separated the communities along the salinity gradient in the plume.

Copepod assemblage structure (Crustacea: Copepoda) along a longitudinal environmental gradient in a tropical river-floodplain system, Brazil

Abstract Aim: In this study, we analyzed the structure of the copepod community along a longitudinal axis of the last undammed stretch of the Upper Paraná River floodplain, downstream of Porto Primavera reservoir. We hypothesized that (i) copepod assemblage would show an increase in the abundance of organisms, species richness and specific diversity with the distance from the Porto Primavera reservoir, due to the arrival of species from adjacent lakes and tributaries; (ii) copepod abundance and species richness would be higher in tributaries and adjacent lakes located at the floodplain, which show higher environmental heterogeneity and function as a species source; and (iii) spatial patterns of copepod assemblage structure are related to the environmental gradient, since copepods show a rapid response to the variation of environmental conditions. Method Sampling was performed quarterly from August 2013 to July 2014, at the subsurface of the pelagic region. Sampling sites were located along the Paraná River, in seven of its tributaries, and in eight lakes located in its floodplain. Results We identified 29 species belonging to two families: Cyclopidae (21 species) and Diaptomidae (eight species). On contrary of our first hypothesis, ANOVA results showed a significant decrease in copepod abundance in the downstream direction. Similarly, the tributaries showed higher values of ecological attributes in the upstream stretch. RDA results showed that in axis 1, the Paraná River and the lakes were positively correlated with conductivity, pH, temperature and suspended organic matter, characterized by the most abundant copepod species. The tributaries, on the other hand, were negatively correlated with turbidity, total nitrogen, total phosphorus and depth. Axis 2 showed a positive correlation of the Paraná River with conductivity and suspended organic matter, and a higher abundance of Argyrodiaptomus azevedoi, Notodiaptomus iheringi, N. henseni, N. cearensis and N. cf. spinuliferus. On the other hand, the lakes were positively correlated with temperature and pH and also with a higher abundance of Thermocyclops minutus and T. decipiens. Conclusion We highlight the importance of the maintenance of the ecological integrity of the Upper Paraná River floodplain, especially of its tributaries, in order to support the high biodiversity registered in the last undammed stretch. Furthermore, we highlight the importance of manipulation of water levels in reservoirs located upstream of this stretch, a necessary condition to maintain the hydrological connectivity between floodplain habitats and the main river.

Видовой состав и численность метазойного микрозоопланктона в водах северо-восточной части Чёрного моря летом 2013 г.

Метазойный микрозоопланктон играет решающую роль в питании личинок и мальков многих видов рыб, в том числе промысловых. Целью работы являлось исследование обилия и видового состава микрометазоопланктона в водах северо-восточной части Чёрного моря, для которой подобные сведения единичны. Батометрические пробы воды для исследований взяты на двух полигонах в прикерченском районе моря: над шельфом (I) и над континентальным склоном (II). Над большими глубинами концентрация планктона в поверхностном слое была почти в 2 раза выше, а доля неритических видов — значительно ниже по сравнению с концентрацией в акватории над шельфом. Характер вертикального распределения численности микрометазоопланктона зависел от выраженности градиентов температуры и солёности. Общее снижение численности в прибрежных водах южного берега Крыма с глубиной гораздо сильнее выражено над континентальным склоном. В верхних слоях воды доминировали копеподы рода Acartia и Centropages ponticus; в шельфовых водах существенную долю составлял также недавний вселенец в Чёрное море Oithona davisae. В слое термоклина и под ним массовыми были копеподы Oithona similis, Acartia clausi, Paracalanus parvus; из нерачкового планктона преобладали Rotifera. Вновь полученные и ранее опубликованные данные свидетельствуют о тенденции увеличения общего обилия микрометазоопланктона в крымских акваториях Чёрного моря в последние годы.

Phenology and fitness of Calanus glacialis, C. finmarchicus (Copepoda), and their hybrids in the St. Lawrence Estuary

Hybrids between 2 abundant copepod species, Calanus glacialis and C. finmarchicus, were recently detected along the Atlantic and Arctic Cana- dian coast. Hybridization may affect population dy- namics and, thus, impact local productivity. Our study aims to characterize the effect of hybridization on Calanus demography by comparing the in situ repro- ductive phenology and fitness of parental species and their hybrids. Environmental conditions were moni- tored and adult Calanus females were sampled in the upper layer in the St. Lawrence Estuary every second week from the pre-bloom (March to May) to bloom period (June to July) in 2010. Maximal abundance of hybrids (17%) occurred in April between the maxi - ma of C. glacialis (March) and C. finmarchicus (June). The different reproductive phenology of hybrids and parental species likely reduces interspecific gene flow. Contrastingly, fitness components such as the egg production rate of hybrids matched those of their maternal ancestor over the sampling interval. Still, hybrids represented only 10% of total abundance, and their population-based egg production rate was always smaller than that of one parental species. The pre-bloom conditions during the peak abundance of hybrids may partially explain their small reproductive output in that area. Consequently, the impact of hy- bridization on the parental species' population size seems small in 2010 in the St. Lawrence Estuary. However, long-term and spatial surveys are required to conclude on the general effect of hybridization on the population size of parental species over the vast area where they co-occur.

Relationships between copepod community structure, rainfall regimes, and hydrological variables in a tropical mangrove estuary (Amazon coast, Brazil)

The influence of rainfall and hydrological variables on the abundance and diversity of the copepod community was investigated on a monthly basis over an annual cycle in the Taperaçu mangrove estuary. In general, the results show that there were no clear spatial or tidal patterns in any biological variables during the study period, which was related to the reduced horizontal gradient in abiotic parameters, determined mainly by the morphological and morphodynamic features of the estuary. Nevertheless, seasonal and monthly trends were recorded in both the hydrological data and the abundance of the dominant copepod species. In particular, Pseudodiaptomus marshi (6,004.6 ± 22,231.6 ind m−3; F = 5.0, p < 0.05) and Acartia tonsa (905.6 ± 2,400.9 ind m−3; F = 14.6, p < 0.001) predominated during the rainy season, whereas Acartia lilljeborgii (750.8 ± 808.3 ind m−3; U = 413.0, p < 0.01) was the most abundant species in the dry season. A distinct process of succession was observed in the relative abundance of these species, driven by the shift in the rainfall regime, which affected hydrological, in particular salinity, and consequently the abundance of copepod species. We suggest that this may be a general pattern governing the dynamics of copepod populations in the estuaries of the Brazilian Amazonian region.

The turbidity front as a habitat for Acartia tonsa (Copepoda) in the Río de la Plata, Argentina-Uruguay

Acartia tonsa is one of the most abundant copepod species in estuaries worldwide. In the Río de la Plata, its highest densities appear to occur in an area of low quality food (detritus): the turbidity front (TF). The objective of this study was to understand how trophic and oceanographic drivers contribute to the high densities of A. tonsa in the Río de la Plata TF. The patterns of spatial distribution and density of this species were analyzed in relation to oceanographic and biological attributes of the system. The egg production rate (EPR) in the TF was evaluated as a measure of fitness, and a stable isotope analysis indicated the possible sources of organic matter in the species' diet. This study confirmed that the highest observed densities of A. tonsa were mostly associated with the TF, where high suspended matter and low Chl-a occur. Immediately offshore from the TF, decreased copepod densities and the maximum Chl-a values were found. Females close to the estuarine turbidity maximum (ETM) had a lower EPR than those closer to the high Chl-a concentrations. Within the TF, A. tonsa apparently fed on detritus close to the ETM and phytoplankton close to the edge of the TF. The report includes a discussion of how retention processes, two layered flow and the life history strategy of A. tonsa could be contributing to the development of high densities (more than 10,000indm−3) of this species in the inner estuarine zone, despite the poor quality of food available for development in that area. A. tonsa can live and prosper in areas with high turbidity and low chlorophyll concentrations. This trait exemplifies the plasticity of this species and helps explain why it is a key species in many worldwide estuaries.

Morphometric differentiation ofPseudocalanus minutuspopulations in the Barents Sea

Dvoretsky VG. and Dvoretsky AG. 2011. Morphometric differentiation of Pseudocalanus minutus populations in the Barents Sea. —Acta Zoologica (Stockholm) 00: 1–12. We investigated spatial variations in the morphometric characteristics (total length of body, lengths of cephalothorax, abdomen and antennules, and their relative proportions) of Pseudocalanus minutus, an abundant copepod species across the Barents Sea in August–September 2007. Females were found to have higher values for the measured parameters than males. The average absolute morphometric characters of both sexes increased from the south to the north. In most cases, parameters were similar in the southern, central, and eastern regions delineated by cluster analyses of oceanographic variables. The morphometric characteristics were strongly correlated with environmental variables in both males and females. Multiple regression analysis showed that temperature together with salinity explained 72–85% (in females) and 38–91% (in males) of the total variations in the log10-transformed morphometric parameters. According to principal component analysis and discriminant function analysis, two distinct groups could be separated in the Barents Sea. The first group included the copepods from the northern region; the other included populations from the southern, central, and eastern regions. The observed morphological variation can be interpreted as geographical variation connected with hydrological variability.

Copepods and salmon: characterizing the spatial distribution of juvenile salmon along the Washington and Oregon coast, USA

Yearling Chinook (Oncorhynchus tshawytscha) and coho salmon (Oncorhynchus kisutch) were sampled concurrently with physical variables (temperature, salinity, depth) and biological variables (chlorophyll a concentration and copepod abundance) along the Washington and Oregon coast in June 1998–2008. Copepod species were divided into four different groups based on their water-type affinities: cold neritic, subarctic oceanic, warm neritic, and warm oceanic. Generalized linear mixed models were used to quantify the relationship between the abundance of these four different copepod groups and the abundance of juvenile salmon. The relationships between juvenile salmon and different copepod groups were further validated using regression analysis of annual mean juvenile salmon abundance versus the mean abundance of the copepod groups. Yearling Chinook salmon abundance was negatively correlated with warm oceanic copepods, warm neritic copepods, and bottom depth, and positively correlated with cold neritic copepods, subarctic copepods, and chlorophyll a concentration. The selected habitat variables explained 67% of the variation in yearling Chinook abundance. Yearling coho salmon abundance was negatively correlated with warm oceanic copepods, warm neritic copepods, and bottom depth, and positively correlated with temperature. The selected habitat variables explained 40% of the variation in yearling coho abundance. Results suggest that copepod communities can be used to characterize spatio-temporal patterns of abundance of juvenile salmon, i.e., large-scale interannual variations in ocean conditions (warm versus cold years) and inshore-offshore (cross-shelf) gradients in the abundance of juvenile salmon can be characterized by differences in the abundance of copepod species with various water mass affinities.

Development, growth, and reproduction of the cyclopoid copepod Limnoithona tetraspina in the upper San Francisco Estuary

Limnoithona tetraspina is a small cyclopoid copepod that was introduced to the San Francisco Estuary (SFE), USA, in 1993 and became the most abundant copepod species in the low- salinity zone (LSZ). Two previous studies have shown that it feeds only on motile prey, predominantly ciliates. Little is otherwise known of its biology or its role in the estuarine foodweb. We determined development times, growth rates, and fecundity of L. tetraspina from March to August of 2006 and 2007. The mean growth rate of copepodites in both years was 0.03 d -1 , which is low relative to values reported for related Oithona spp. Development times were longer in the field than in the laboratory at food saturation, indicating food limitation in the SFE. Mean weight-specific fecundity rate in 2007 was 0.10 d -1 , which is twice that of 2006, but within the range of reported values for Oithona spp. Low growth and fecundity rates indicate that the population success of L. tetraspina is due to low mortal- ity. L. tetraspina may avoid certain mortality agents (e.g. visual predation) to which larger copepods are susceptible.

Fine-scale vertical distribution of coastal and offshore copepods in the Golfo de Arauco, central Chile, during the upwelling season

In order to understand the mechanism by which zooplankters from different origins co-occur during the upwelling season within Golfo de Arauco, one of the most productive areas in central Chile, we assessed short term variations in the vertical distribution of the most abundant copepod species. Fine-scale, day and night vertical zooplankton sampling was done with a pump over 12 days in summer. The water column in the gulf consisted of three layers: Equatorial Subsurface Water of low dissolved oxygen content in the deeper part of the water column, strong temperature and oxygen gradients at mid-depth (15–25 m), and a layer of warmer, more oxygenated, less saline water at the surface. Copepods within the gulf originated from offshore, from the continental shelf, and from the coastal area. Most taxa showed distinctive vertical distributions. Three copepod groups were identified by their mean weighted depths of residence. One group included shallow residents found above the thermocline/oxycline ( Acartia tonsa, Centropages brachiatus, Corycaeus sp., Paracalanus parvus, Oncaea sp.). A second group was comprised by species distributed at or below the thermocline/oxycline ( Oithona sp., Oncaea conifera, Lucicutia sp., Metridia sp., Heterorhabdus papilliger). The third group was composed of vertical migrators that crossed the thermocline/oxycline ( Calanus chilensis, Calanoides patagoniensis, Aetideus armatus, Pleuromamma piseki). In spite of their different vertical distribution ranges, the most abundant and frequent copepod species ( P. parvus, C. chilensis, C. patagoniensis, C. brachiatus) share a common capacity to withstand wide ranges of oxygen concentration and temperature. This characteristic, along with the capacity to vary their life strategies under different environmental conditions, seems to facilitate the maintenance of large numbers of copepods in coastal waters along the Humboldt Current.

The seasonal abundance and production of Oithona nana (Copepoda:Cyclopoida) in Southampton Water

Recent studies indicate that Oithona spp. contribute significantly to total copepod biomass. Little is known, however, about their ecological significance, particularly in the case of the estuarine Oithona nana. A study comprising three sites within Southampton Water was conducted to evaluate the late-stage copepodite/adult (stages IV to VI) O. nana community, using 120 μm mesh nets. Although present throughout the estuary, there was a striking spatial gradient with O. nana most common in the upper estuary. A clear seasonal pattern was observed with O. nana as the most abundant copepod species from late-summer until early-winter. It comprised 61% of all copepods recorded, with a biomass of 757.22 mg C m -3 . Production estimates of O. nana were derived from the “instantaneous-growth” approach, using appropriate growth equations. The estimated production of O. nana ranged from 1.50 mg C m -3 yr -1 within the lower estuary to 146.77 mg C m -3

Copepod feeding behaviour and egg production during a dinoflagellate bloom in the North Sea

Feeding strategies of copepods were studied during a dinoflagellate-dominated bloom in the North Sea in August 2001. The aim of this study was to evaluate the importance of mesozooplankton grazing as a biological loss factor of harmful algal blooms under naturalconditions. Therefore, ingestion,egestionand eggproduction experiments were performedwith themost abundant copepod species Calanus helgolandicus, Temora longicornis and Acartia sp. feeding on the natural phytoplankton community. Dinophysis norvegica and Ceratium furcawere the most abundant dinoflagellate species at the time of the experiments. Grazing experiments as well as examination of fecal pellet content revealed C. helgolandicus fed efficiently on D. norvegica. Ingestion rates up to 47 cells female 1 h 1 were measured and a large proportion of the C. helgolandicus fecal pellets contained intact D. norvegica cells. Dinophysis cells were rarely seen in fecal pellets produced by T. longicornis, and never observed in pellets produced by Acartia sp. The ingestion rate of C. furca, which was the dominating Ceratium species, mimicked that of D. norvegica. C. helgolandicus grazed significantly on C. furca (16 cells female 1 h 1 ), while the ingestion rate of T. longicornis was low and Acartiasp. wasnotable to graze on C. furca. Eggproduction experiments revealed that 92% ofthe C. helgolandicus females produced eggs. The specific egg production rate and the proportion of females producing eggs among T. longicornis were low. This field experiment clearly shows that some copepod species feed efficiently on D. norvegica and C. furca under natural conditions, which may affect the bloom development of these dinoflagellates. # 2005 Elsevier B.V. All rights reserved.

Trophic impact and prey selection by crustacean zooplankton on the microbial communities of an oligotrophic coastal area (NW Mediterranean Sea)

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 35:65-78 (2004) - doi:10.3354/ame035065 Trophic impact and prey selection by crustacean zooplankton on the microbial communities of an oligotrophic coastal area (NW Mediterranean Sea) Elisabetta Broglio, Enric Saiz*, Albert Calbet, Isabel Trepat, Miquel Alcaraz Departament de Biologia Marina i Oceanografia, Institut de Ciències del Mar, CMIMA, CSIC, Passeig Marítim de la Barceloneta 37-49, 08003 Barcelona, Catalunya, Spain *Corresponding author. Email: enric.saiz@icm.csic.es ABSTRACT: Selection for ciliates in the presence of phytoplankton has been previously shown for some species of copepods. However, the factors determining preference for this heterotrophic prey and how crustacean zooplankton predation can affect the ciliate community are not yet fully understood. In this study, we investigated predation rates on phytoplankton and ciliates by the most abundant copepod and cladoceran species in a coastal area of the oligotrophic NW Mediterranean Sea monthly over an annual cycle. Three major results were apparent. Firstly, ciliates were important contributors to zooplankton diet, representing a median of 37 and 17% of the carbon intake, and 51 and 34% of the nitrogen intake for copepods and cladocerans, respectively. Secondly, ciliates were positively selected in most cases, this selection was species specific and apparently independent of phytoplankton concentration. And finally, in spite of the high clearance rates on ciliates, the impact of the crustacean community on the ciliate standing stock was low (median 2%), suggesting a bottom-up control of the ciliate community. KEY WORDS: Copepods · Cladocerans · Ciliates · Food web · NW Mediterranean Full article in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 35, No. 1. Online publication date: April 02, 2004 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2004 Inter-Research.

Dramatic change in the copepod community in Sevastopol Bay (Black Sea) during two decades (1976–1996)

The seasonal and inter-annual fluctuation of species composition and abundance of copepods in Sevastopol Bay (Black Sea) are presented for the years 1976, 1979–80, 1989–90, 1995–96. The copepod community of the Sevastopol Bay shifted to an other state from the beginning of the seventies to 1996. The main change in the species composition occurred in 1989–1996, when the average annual number of copepods decreased approximately by a factor of 17 compared to the period 1976; 1979/80. The two most abundant copepod species,Acartia clausi (small form) andOitbona nana, vanished, whileAcartia clausi (typical form) andPseudocalanus elongatus became the dominating species. The percentage of copepods of total zooplankton decreased from 54% to 21%. As possible reasons for the degradation of the copepod community eutrophication, pollution and the impact of the accidentally introducedMnemiopsis leidyi A. Agassiz, 1865 are discussed.