Copepod Populations Research Articles

Active avoidance from a crude oil soluble fraction by an Andean paramo copepod.

Several oil spills due to ruptures in the pipeline oil systems have occurred at the Andean paramo. A sample of this crude oil was mixed with water from a nearby Andean lagoon and the toxicity of the soluble fraction was assessed through lethal and avoidance assays with a locally occurring copepod (Boeckella occidentalis intermedia). The integration of mortality and avoidance aimed at predicting the immediate decline of copepod populations facing an oil leakage. The 24-h median lethal PAH concentration was 42.7 (26.4-91.6) µg L(-1). In the 12-h avoidance assay, 30% avoidance was recorded at the highest PAH concentration (19.4 µg L(-1)). The mortality at this PAH concentration would be of 25% and, thus, the population immediate decline would be of 55%. The inclusion of non-forced exposure testing with the quantification of the avoidance response in environmental risk assessments is, therefore, supported due to underestimation of the lethal assays.

Contrasting patterns of MAAs accumulation in two populations of the copepod Boeckella gracilipes

The bio-accumulation of mycosporine-like amino acids (MAAs) is common in planktonic copepods that inhabit environments exposed to high levels of solar radiation. MAAs accumulation in copepods can be affected both by extrinsic (environmental) and intrinsic factors (local adaptation, genotype, etc.). Laboratory experiments were performed to study the bio-accumulation of MAAs in two geographically-isolated populations of Boeckella gracilipes from a mountain and a piedmont lake of North Patagonia. We performed two series of 10-day incubations of B. gracilipes from the different lakes applying two radiation conditions (PAR + UVR and darkness), at five different temperatures (5 to 20 °C) and providing a MAA-free flagellate as food. We assumed that differences in final MAAs concentrations between copepod populations should be exclusively due to environmental factors, and that any difference in the patterns of MAAs accumulation should exclusively arise from differences in MAAs concentration at the time of collection. MAAs concentration was three fold higher in B. gracilipes from Lake Verde than in copepods from the Lake Morenito. The MAAs suite was dominated (∼90%) by a combination of porphyra-334 and mycosporine-glycine in copepods from Lake Verde, and porphyra-334 and MAA-332 in those from Lake Morenito. Two exclusive MAA compounds were identified, mycosporine-glycine in copepods from Lake Verde and shinorine in the copepod population from Lake Morenito. Laboratory experiments showed that: (i) exposure to PAR + UVR stimulated the accumulation of MAAs in both copepod populations; (ii) temperature affected the response of MAAs and, remarkably, low temperatures stimulated MAAs accumulation even in dark incubations, (iii) the response to radiation and temperature in MAAs accumulation was more pronounced in the population with low initial MAAs than in the population with high initial MAAs concentrations. The differences in intrinsic factors between B. gracilipes populations, such as local adaptation to contrasting UV and temperature scenarios, among others, appear to play an important role in determining levels and patterns of MAAs accumulation in B. gracilipes.

Modeling the impacts of multiple environmental stress factors on estuarine copepod populations.

Many studies have focused on natural stress factors that shape the spatial and temporal distribution of calanoid copepods, but bioassays have shown that copepods are also sensitive to a broad range of contaminants. Although both anthropogenic and natural stress factors are obviously at play in natural copepod communities, most studies consider only one or the other. In the present investigation, we modeled the combined impact of both anthropogenic and natural stress factors on copepod populations. The model was applied to estimate Eurytemora affinis densities in the contaminated Scheldt estuary and the relatively uncontaminated Darß-Zingst estuary in relation to temperature, salinity, chlorophyll a, and sediment concentrations of cadmium, copper, and zinc. The results indicated that temperature was largely responsible for seasonal fluctuations of E. affinis densities. Our model results further suggested that exposure to zinc and copper was largely responsible for the reduced population densities in the contaminated estuary. The model provides a consistent framework for integrating and quantifying the impacts of multiple anthropogenic and natural stress factors on copepod populations. It facilitates the extrapolation of laboratory experiments to ecologically relevant end points pertaining to population viability.

Relationships between clogging in irrigation systems and plankton community structure and distribution in wastewater reservoirs

The development of large populations of cladocerans and copepods in reservoirs that store wastewater for crop irrigation causes severe clogging in irrigation systems. In most reservoirs in Israel water is filtered at the banks of the reservoirs before being sent to irrigation. This avoids/reduces clogging in the irrigation systems transferring the problem to the storage reservoirs. To cope with this problem we studied relationships between clogging and particle size distribution in a range of secondarily treated wastewater reservoirs with different characteristics and water management. Since the reservoirs are deep and thermal stratification develops, measurements of the time required to clog 100μm pore net filters and samples for physico-chemical and microscopic analyses were collected in the surface, deep epilimnion and hypolimnion. Factor analysis allowed identifying two independent sets of environmental conditions and planktonic species that lead to clogging of irrigation filters. The first set is related to thermal stratification and the development of a planktonic community with a complex web of feeding interactions in which the organisms capable of clogging filters are mainly copepods. The second set occurs in spring and fall, and includes planktonic organisms forming a short food chain in which the organisms capable of clogging filters are mainly cladocerans. A third factor was organic loading, mostly related to the entrance of fresh wastewater into the reservoirs during the irrigation season, which had a negative effect on nitrification and promoted blue green algae development and copepod reproduction. The analysis of potential management procedures to avoid filter clogging indicates that in these reservoirs manipulations of food web interactions in the planktonic community structure towards smaller organisms that do not clog filters would not be effective against copepods. A better option to decrease clogging events is to avoid pumping water out from the deep epilimnion, preferably pumping from the hypolimnion.

Latest Diversity Trend and Seasonal Abundance of Population of Zooplankton (Holoplankton) Communities in the South Caspian Sea, Iran

Seasonal variations of zooplankton communities were studied in the southern Caspian Sea for 4 successive seasons and 8 transects with 5 stations from 5 to 100 m depths which sampled during 2009. The zooplankton population constituted of 73.33% copepods, 24.21% rotifers, 2.23% cladocerans and 0.23% protozoans. Copepods were dominant at all stations with a density between 1456±531 ind. m -3 (Transect 8) to 4524±1215 ind. m -3 (transect 2). The predominant species of copepods was Acartia tonsa constituting 99.50% of all copepod populations. They were most abundant during warm months of summer in the upper layers (surface to 20 m depth) while rotifers replaced them during cold season. The maximum density of zooplankton was observed in the west decreasing towards the eastern parts of the sea.

Characterization of copepod Scottomyzon gibberum scott population on Asterias rubens L. starfishes under different anthropogenic load conditions

This articles describes copepod Scottomyzon gibberum population on Asterias rubens starfishes collected during the 2012 growth period. The population increases from mid-June to late September. Heterogeneity in the population was also shown, which can be related with anthropogenic load. The population of copepods on the starfishes is higher in regions with increased anthropogenic load conditions. An increase in the copepods population on the starfishes with depth was observed.

Trophic role and top-down control of a subarctic protozooplankton community

Plankton succession was investigated in the subarctic Godthabsfjord, Western Greenland, from March to August 2010. The trophic role of protozooplankton (ciliates and hetero- trophic dinoflagellates) was evaluated with emphasis on their seasonal succession and as prey for the copepod community. The integrated protozooplankton biomass ranged between 0.1 and 4.0 g C m �2 , and was dominated by ciliates. Over the 6 mo study period, maximum potential ingestion rates of the protozooplankton ranged from 0.02 to 1.2 g C m �2 d �1 , corresponding to 30 to 194% of primary production d �1 or 0.5 to 37% of phytoplankton biomass d �1 . The highest copepod biomass (24 g C m �2 ) occurred in spring, with Metridia longa alone contributing up to 92% of the biomass. A grazing experiment with M. longa feeding on a natural plankton assemblage confirmed that this species cleared cells in the size range 10 to 60 µm with an average clearance rate of 2.4 ml µg C �1 d �1 . The copepod community, dominated by the genera Calanus, Metridia, Pseudocalanus, Oithona, Microsetella and Triconia/Oncaea, accounted for 72 to 93% of the copepod biomass in the spring. After the large calanoid copepod species left the surface layer, the protozooplankton increased numerically and were the most important grazers for some weeks until a late summer copepod community, dominated by cyclopoids Oithona spp., controlled the protist community. Our study indicated that protozooplankton succession is regulated by copepod grazing during most of the season, and that these protists provide an essential source of nutrition for the copepod populations.

Low fertilization rates in a pelagic copepod caused by sexual selection?

We studied female fertilization status in North Sea summer populations and laboratory cultures of the marine copepod Temora longicornis and found fractions of fertilized females in both field and laboratory populations that were much smaller (,50%) than predicted by a theoretical model that assumes random mating. Such low fertilization rates are normally related to environmental factors such as poor food or low densities, which we could not confirm in our experiment. Male density was negatively related to fertilization rate, and a large fraction of males did not mate in laboratory incubations. We therefore suggest that sexual selection, through mate choice or male–male competition could account for low fertilization rates of females in populations of pelagic copepods during some periods of the year.

Acute toxicity of tributyltin on the marine copepod Tisbe biminiensis

Antifouling systems (AFS) are physical or chemical treatments that control or prevent biological fouling on submerged surfaces (IMO, 2001). Tributyltin-based compounds have been used as AFS since the 1960s. These chemicals were soon recognized as ideal biocides and became the main AFS applied to ship hulls for several decades. Champ (2001) estimated that tributyltin (TBT) was applied to approximately 60,000 vessels of the world’s merchant fleet in 2001. The widespread use of TBT as an AFS was identified to be a marine pollution issue in the 1970s when oyster shell anomalies and population declines were observed in Arcachon Bay, France (ALZIEU et al., 1986). Other TBT toxic effects have been identified in marine invertebrates, including imposex in mollusks, reduced reproductive success in amphipods and biased female-to-male ratio in copepod populations (HUANG et al., 2006; AONO; TAKEUCHI, 2008; BIGATTI et al., 2009). In 2001, the International Maritime Organization (IMO) proposed an international convention for controlling the use of harmful AFS on ships (IMO, 2001). The initial goal of banning TBT by 2008 was challenging and did not succeed. Officially, the convention came into force only on September 17, 2008 and it currently has 63 Parties whose combined fleet represents 81% of the world’s merchant ships (IMO, 2012). After proposal of the AFS convention in 2001, TBT concentrations in seawater began to decline although concentrations are still considered high in some parts of the world (ANTIZAR-LADISLAO, 2008). Liu et al. (2011) reported seawater concentrations ranging from 17 to 274 ng L

Predation of calanoid copepods on their own and other copepods’ offspring

Predation of eggs and nauplii by adult copepods is often used to explain unexpected death rates in population dynamics studies, but the phenomenon has been rarely investigated or quantified. Therefore, we studied the predatory feeding of adult females (Acartia clausi, Centropages hamatus, Centropages typicus, and Temora longicornis) on their own and other species’ eggs and young nauplii with different densities of single animal-prey, mixtures of animal-prey and in the presence of diatoms. All species preyed on eggs and nauplii of their own and all other species. Maximal egg predation varied between 7 and 64 eggs fem−1 day−1. Ingestion of Centropages spp. eggs was lowest, potentially due to the spiny egg surface. Maximal feeding rates on nauplii ranged from 5 to 45 nauplii fem−1 day−1. T. longicornis preferred eggs, when eggs and nauplii were offered together at the same densities, and the other predators selected for nauplii. At a diatom concentration of 60 μg C l−1 predation on eggs by C. typicus was higher than without algae, whereas A. clausi and T. longicornis did not change their uptake of eggs. Feeding on nauplii in the presence of diatoms was again enhanced in C. typicus, and unaffected in A. clausi and C. hamatus. T. longicornis reduced its feeding on nauplii in the presence of diatoms. Calculated predation rates, using field abundances of predators and prey, suggest that predation of copepods on their own young stages may account for ca. 30 % of total mortality of young stages in North Sea copepod populations.

Variation in assimilation efficiencies of dominant Neocalanus and Eucalanus copepods in the subarctic Pacific: Consequences for population structure models

The assimilation efficiency of zooplankton is an essential parameter required to estimate energy transfer to higher trophic levels in marine ecosystems. However, little information is available for large oceanic copepods, especially the Neocalanus and Eucalanus species dominant in the subarctic Pacific. In this study, the assimilation efficiencies of the C5 stages of Neocalanus cristatus, Neocalanus flemingeri and Eucalanus bungii were evaluated using eight phytoplankton species as food. The average assimilation efficiencies of N. cristatus, N. flemingeri and E. bungii ranged between 45 and 66%, 44 and 66% and 34 and 65%, respectively. The assimilation efficiency was highly variable depending on the food phytoplankton species. In all species, the assimilation efficiency showed a significant negative relationship with the ash content of the phytoplankton (r2=0.79–0.87, p<0.001). The assimilation efficiency of large-body sized N. cristatus for large-sized diatoms was higher than for the other copepod species. In population models of N. cristatus, changes in assimilation efficiency affect the growth and survival rates of the population. The Lagrangian ensemble model (LEM) for N. cristatus showed that, for assimilation efficiencies less than 57%, the population could not be maintained. Because variations in assimilation efficiency may have significant effects on the copepod population, their variability should be incorporated into marine ecosystem models in the future.

ON MODELING THE GROWTH DYNAMICS OF A STAGE STRUCTURED POPULATION

A Lagrangian modeling approach is applied to the numerical simulation of the temporal dynamics of a stage-structured population. The growth dynamics is determined only by the main biological processes: development of an individual, mortality, reproduction. Different approaches in modeling the development process of an individual are implemented: stochastic advection-diffusion models (backward–forward dispersion models), and stochastic development models where regression effects, defined as negative development on the status of an individual, are forbidden (forward dispersion models). Some properties of the residence times of an individual in a stage are investigated: in particular, their role in the calibration of the development models and in the estimation of some parameters introduced in the model equation. As a study case a multi-stage pelagic copepod population is considered. Trying to separate the effects of the main biological processes on the temporal dynamics, numerical simulations have been carried out in some idealized situations: first only the development of the individuals, neglecting mortality and reproduction, is considered; then the mortality process is introduced, and finally both the mortality and reproduction processes. The results of the numerical simulations, are compared and discussed.

What factors drive copepod community distribution in the Gulf of Gabes, Eastern Mediterranean Sea?

The spatial and temporal variations in copepod communities were investigated during four oceanographic cruises conducted between July 2005 and March 2007 aboard the R/V Hannibal. A close relationship was observed between the temperature, salinity, hydrographic properties and water masses characterising the Gulf of Gabes. Indeed, water thermal stratification began in May-June, and a thermocline was established at a 20-m depth, but ranged from 25 m in July to more than 30 m in September. The zooplankton community is dominated by copepods representing 69 % to 83 % of total zooplankton. Spatial and temporal variation of copepods in relation to environmental factors shows their close relationship with the hydrodynamic features of the water column. Thermal stratification in the column, established in summer, supports copepod development. In fact, copepod abundance increases gradually with rising water temperature and salinity, starting from the beginning of thermal stratification (May-June 2006) and lasting until its completion (July 2005 and September 2006). When the water column is well mixed (March 2007), copepod abundance decreased. Our finding shows that temperature and salinity seem to be the most important physical factors and thus strongly influence the taxonomic diversity and distribution of the copepod population. They are characterised by the dominance of Oithona nana, representing 75-86 % of total cyclopoid abundance. The most abundant species during the stratification period were O. nana, Acartia clausi and Stephos marsalensis in July 2005 and September 2006. However, during the mixing period, Euterpina acutifrons was more abundant, representing 21 % of the total. Unlike the copepod community, which is more abundant during the period of high stratification, phytoplankton proliferates during semi-mixed conditions.

Non-consumptive mortality in copepods: occurrence of Calanus spp. carcasses in the Arctic Ocean during winter

During a research cruise to the Arctic Ocean in January 2012, we observed high occurrence of carcasses of Calanus spp. We analysed live samples to separate living from dead individuals. In Rijpfjorden, an Arctic fjord in north-eastern Svalbard, 9–14% of the Calanus population were observed to be dead. At Sofiadjupet, an oceanic basin located at 81.4N at the southern edge of the Arctic Ocean, 94% of the Calanus at depth (between 300 and 2000 m) were dead. This is the first estimation of the contribution of carcasses to high Arctic copepod populations. Lipid sacs were preserved in part of the observed carcasses and the lipid sac area was significantly smaller in dead Calanus than in living individuals. We discuss possible causes for the observed mortality, its implication for population dynamics and energy transfer and review previous accounts of non-predatory mortality of marine copepods. In our case, partial consumption by predators and death after reproduction are unlikely causes of mortality, thus other stressors (starvation, environmental conditions, parasitic or viral infection) may be responsible. Our analysis shows that we have a poor understanding of factors other than predation causing mortality in copepod populations.

Response of Copepods to Elevated pCO2 and Environmental Copper as Co-Stressors – A Multigenerational Study

We examined the impacts of ocean acidification and copper as co-stressors on the reproduction and population level responses of the benthic copepod Tisbe battagliai across two generations. Naupliar production, growth, and cuticle elemental composition were determined for four pH values: 8.06 (control); 7.95; 7.82; 7.67, with copper addition to concentrations equivalent to those in benthic pore waters. An additive synergistic effect was observed; the decline in naupliar production was greater with added copper at decreasing pH than for decreasing pH alone. Naupliar production modelled for the two generations revealed a negative synergistic impact between ocean acidification and environmentally relevant copper concentrations. Conversely, copper addition enhanced copepod growth, with larger copepods produced at each pH compared to the impact of pH alone. Copepod digests revealed significantly reduced cuticle concentrations of sulphur, phosphorus and calcium under decreasing pH; further, copper uptake increased to toxic levels that lead to reduced naupliar production. These data suggest that ocean acidification will enhance copper bioavailability, resulting in larger, but less fecund individuals that may have an overall detrimental outcome for copepod populations.

Copepods and hypoxia in Chesapeake Bay: abundance, vertical position and non-predatory mortality

Live and dead copepod abundances and environmental conditions were measured during summer in Chesapeake Bay to determine how population size, vertical position and non-predatory mortality varied with hypoxia. Abundances of copepod nauplii and Acartia tonsa copepodites decreased when low-oxygen water was present. Possible explanations include copepods altering their vertical position to avoid hypoxia, resulting in increased predation and advection losses. Alternatively, copepods residing in hypoxic water may experience increased mortality and sub-lethal effects of hypoxia on growth and reproduction. The vertical position of copepod nauplii did not appear to respond to hypoxia, but the vertical position of A. tonsa copepodites shifted upward in response to lethal hypoxia in bottom water. Nonpredatory mortality of nauplii increased with the severity of hypoxia, but no similar increase was apparent for copepodites. Overall, it appears that hypoxia in Chesapeake Bay can result in lower copepod population abundances. Under moderate hypoxia, sub-lethal effects of low oxygen on growth and reproduction likely contribute to lower abundances, since the copepods do not avoid the hypoxic water. Under severe hypoxia, non-predatory mortality due to low oxygen is likely more important for naupliar stages, and the effects of altered vertical position on predation and advection may be important for copepodites.

Emergence of the Arctic Themisto libellula (Amphipoda: Hyperiidae) on the southeastern Bering Sea shelf as a result of the recent cooling, and its potential impact on the pelagic food web

AbstractPinchuk, A. I., Coyle, K. O., Farley, E. V., and Renner, H. M. 2013. Emergence of the Arctic Themisto libellula (Amphipoda: Hyperiidae) on the southeastern Bering Sea shelf as a result of the recent cooling, and its potential impact on the pelagic food web. – ICES Journal of Marine Science, 70: 1244–1254. The eastern Bering Sea shelf experienced a sequence of warm years after a regime shift in the late 1970s. Following a series of unusually warm years in the early 2000s, the climate shifted again in 2007 to a series of extremely cold years that were marked by intense ice coverage and late ice retreat. Spatial and temporal variability in zooplankton communities during the recent cold period was investigated as part of the collaborative BEST-BSIERP program. An increasing presence of the Arctic hyperiid Themisto libellula, which had not been reported from the southeastern Bering Sea since the 1970s, was observed in the Middle Shelf Domain, indicating a developing structural shift in the zooplankton community in response to continuous cold conditions. Simultaneously, T. libellula became an increasingly dominant prey in the diets of zooplanktivorous fish and seabirds, demonstrating the important role for T. libellula in the pelagic food web. Our analysis suggests that T. libellula is capable of controlling copepod populations, thus it may become a potential contributor to top-down regulation of Calanus spp. in the eastern Bering Sea.

Low-pH Freshwater Discharges Drive Spatial and Temporal Variations in Life History Traits of Neritic Copepod Acartia tonsa

Land weathering by river runoff makes coastal oceans highly variable ecosystems in terms of seawater pH; however, its effects on biological components and, hence, on the coastal ecosystem functioning has been scarcely addressed. In this study, we determined part of the spatial and seasonal variability of the physical–chemical characteristics of seawater, and life history traits of the neritic copepod Acartia tonsa, along an estuarine-to-coastal zone geographic gradient in the southern Pacific Ocean. There, freshwater influences give rise to sharp gradients in pH, salinity, and temperature, which in turn, may affect the fitness of copepod populations inhabiting along the gradient. In fact, most of the studied copepod traits (egg size, ingestion, and egg production rates) were moderately (r 2 = 0.5, p < 0.05) to robustly (r 2 = 0.9, p < 0.05) explained by physical–chemical and biological (food abundance and composition) factors. Noteworthy was the negative relationship between low-pH waters and copepod reproductive outcomes. This effect was far evident in the estuarine area where small brood sizes and depleted egg production rates were significantly correlated with low seawater pH (r 2 = 0.6, p < 0.05). If short-term episodes of low-pH seawater constitute a significant threshold for reproduction, current findings should stimulate a better description of pH variability in coastal zones, as well as the study of biological consequences derived from the interaction between pH and others drivers on coastal marine populations.

Reproductive and phylogenetic divergence of tidepool copepod populations across a narrow geographical boundary in Baja California

AbstractAimPrevious work on the tidepool copepodTigriopus californicusrevealed a curious case of incipient speciation at the southern end of the species' range in Baja California, Mexico. The present study expands on the geography of this pattern and tests for congruence between reproductive and phylogenetic patterns.LocationThe Pacific coast of North America, from central Baja California to south‐eastern Alaska (27–57° N), including the full range ofT. californicus.MethodsPrimary techniques included mating experiments (&gt; 4000 crosses), phylogeny reconstruction (mitochondrial cytochromecoxidase subunit I) and screening of single nucleotide polymorphisms (SNPs, 42 loci). Analyses used &gt; 8000 copepods for the mating experiments, 86 copepods for the phylogeny and 41 copepods for theSNPassays. Phylogenies were constructed using Bayesian, maximum likelihood and maximum parsimony methods.ResultsPopulations were found to fall into three reproductive groups: northern and southern groups that were reproductively isolated from each other, and an intermediate group that could serve as a conduit for gene flow. The northern and intermediate populations fell into one clade while all southern populations fell into a second clade. These two clades are now separated by less than 12 km at latitude 29.35° N. NuclearSNPdata for a subset of locations confirmed striking divergence between populations on either side of this boundary. The second (southern) clade was further subdivided into two clades separated by the lagoon region of Guerrero Negro (latitude 28° N).Main conclusionsReproductive assays and molecular data (both mitochondrial and nuclear) reveal a sharp break at 29.35° N, a region with no obvious barriers to dispersal, with no evidence for mixing across this narrow transition zone. Results also showed a milder break at the Guerrero Negro Lagoon (28° N), a location where breaks have been reported for other taxa.

Copepod diversity in a subtropical bay based on a fragment of the mitochondrial COI gene

Copepod communities in lagoons and embayments on subtropical islands in the Pacific Ocean are geographically isolated from other populations along continents and other islands. Nevertheless, taxonomic identifications suggest that many of these species are cosmopolitan. The genetic diversity of planktonic copepod species in a subtropical embayment, Kaneohe Bay, Hawaii, was investigated by pairing morphological identification of the species with sequencing a 710 bp fragment of the mitochondrial cytochrome oxidase c subunit I (mtCOI) gene. DNA sequences were obtained for six calanoid and three cyclopoid copepod species. The sequences of two oceanic species found in the bay, Undinula vulgaris and Paracalanus parvus, were ≤3.0% divergent from conspecifics in the coastal western Pacific Ocean. In contrast, sequences from the more estuarine, Parvocalanus crassirostris and Bestiolina similis specimens were ≥16.0% divergent from conspecifics of the western Pacific Ocean. The Labidocera sp. and Acartia sp. were ≥16.0% divergent from all congeners, while three Oithona species differed by ≥26.5% from congeners. These results suggest significant genetic isolation of the more estuarine species, although more sequence data for Hawaii and elsewhere will be needed to understand the population and genetic structure of coastal island copepod populations.