Abundance Of Calanoid Copepods Research Articles

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

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

Mesozooplankton community responses to a large-scale harmful algal bloom induced by the non-indigenous dinoflagellate Lingulodinium polyedra

Our understanding of how zooplankton community composition varies in relation to harmful algal blooms remains limited, particularly in ecosystems where toxin-producing algae may have been introduced through anthropogenic activities. Harmful algal blooms (HABs) naturally occur on the coast of southern Africa, where they are predominantly associated with the cold Benguela region. In the warm-temperate waters east of Cape Agulhas, HABs occur rarely and red tides are mostly associated with the non-toxin producing dinoflagellate Noctiluca scintillans. Blooms of N. scintillans may cause water discolouration, but this is generally short-lived with limited impact on the ecosystem. However, in December 2013 the eastern Agulhas region experienced an extensive HAB, which persisted for ca. 4 months and affected >500 km of coastline, from Wilderness to East London. This unprecedented event was caused by the non-indigenous toxin-producing dinoflagellate, Lingulodinium polyedra. The impact on the coastal seas was widespread and severe, with instances of low dissolved O2 levels and fish kills being reported at the time in the broader Algoa Bay area. This study investigated the impact of the L. polyedra bloom on the mesozooplankton of Algoa Bay and reports the successive changes in zooplankton community composition and biomass observed from July 2013 to July 2014. The bloom impacted species diversity and richness, with a marked shift in dominance from a calanoid copepod dominated community to one dominated by microzooplankton (specifically cyclopoid copepods, tintinnids and cladocerans), over the period November 2013–March 2014. Calanoid copepod abundance was significantly reduced throughout Algoa Bay with the progression of the bloom, and this significantly impacted the total zooplankton biomass of the region. The results of the study suggest that harmful algal blooms have a negative impact on zooplankton communities, with notable implications for the higher trophic levels of the coastal pelagic ecosystem.

Seasonality and interannual variability of copepods in the Western English Channel, Celtic Sea, Bay of Biscay, and Cantabrian Sea with a special emphasis to Calanus helgolandicus and Acartia clausi

Abstract A total of five mesozooplankton time series data sets were assembled to compare the seasonal and interannual patterns of abundance of calanoid copepods in the Western English Channel (Station L4), Celtic Sea, Bay of Biscay (Continuous Plankton Recorder), and the Cantabrian Sea (RADIALES time series, Santander, St-4 and St-6) from January 1992 to December 1999. A strong seasonal component in taxonomic composition was detected at the locations considered. There was also a strong latitudinal effect on diversity at each location, southernmost locations being more diverse. The seasonal dynamics and year-to-year variability of two copepod species: Calanus helgolandicus and Acartia clausi were studied in detail. A latitudinal pattern in the seasonal cycles of both copepod species was observed. The peaks of both occur earlier in spring in the warmer southern region and move northwards, consistent with the temperature regimes at each location, supporting the broad concept that species occupy a thermal niche in time as well as in space. There was a strong degree of interannual variability between sites and between species. No clear trends, but some coherent events among data sets, reveal a regional response to environmental forcing factors. Correlations suggest possible connections with environmental indices like the North Atlantic Oscillation and the Gulf Stream North Wall index. There was a positive correlation between the NAO and the abundance of C. helgolandicus at station L4 off Plymouth; however, the relationship in the Celtic Sea and Bay of Biscay was opposite to that expected based on previous results. Despite the differences in the sampling techniques used within each dataset, the results are comparable and coherent in terms of taxonomic composition and the seasonal and interannual patterns detected.

Vertical Migration of Pelagic and Mesopelagic Scatterers From ADCP Backscatter Data in the Southern Norwegian Sea

Records of backscatter and vertical velocity obtained from moored Acoustic Doppler Current Profilers (ADCP) enabled new insights into the dynamics of deep scattering layers (DSLs) and diel vertical migration (DVM) of mesopelagic biomass between these deep layers and the near-surface photic zone in the southern Norwegian Sea. The DSL exhibits characteristic vertical movement on inter-monthly time scales, which is associated with undulations of the main pycnocline between the warm Atlantic water and the underlying colder water masses. Timing of the DVM is closely linked to the day-night light cycle—decent from the photic zone just before sunrise and ascent immediately after sunset. Seasonal variations are also evident, with the highest DVM activity and lowest depth averaged mean volume backscatter strength (MVBS) during spring. This suggests that both oceanographic and optical conditions are driving the complex dynamics of pelagic and mesopelagic activity in this region. We hypothesize that the increased abundance of calanoid copepods in the near-surface layer during spring increases the motivation for vertical migration of pelagic and mesopelagic species, which therefore can explain the increased DVM activity during this season.

A fish-mediated trophic cascade on freshwater calanoid copepod abundance is concealed by food web fatty acid availability, functional traits and population sex ratio

A fish-mediated trophic cascade on freshwater calanoid copepod abundance is concealed by food web fatty acid availability, functional traits and population sex ratio

Effects of nutrient and water level changes on the composition and size structure of zooplankton communities in shallow lakes under different climatic conditions: a pan-European mesocosm experiment

Lentic ecosystems act as sentinels of climate change, and evidence exists that their sensitivity to warming varies along a latitudinal gradient. We assessed the effects of nutrient and water level variability on zooplankton community composition, taxonomic diversity and size structure in different climate zones by running a standardised controlled 6-months (May to November) experiment in six countries along a European north–south latitudinal temperature gradient. The mesocosms were established with two different depths and nutrient levels. We took monthly zooplankton samples during the study period and pooled a subsample from each sampling to obtain one composite sample per mesocosm. We found a significant effect of temperature on the community composition and size structure of the zooplankton, whereas no effects of water depth or nutrient availability could be traced. The normalised size spectrum became flatter with increasing temperature reflecting higher zooplankton size diversity due to higher abundance of calanoid copepods, but did not differ among depths or nutrient levels. Large-bodied cladocerans such as Daphnia decreased with temperature. Taxonomic diversity was positively related to size diversity, but neither of the two diversity measures demonstrated a clear pattern along the temperature gradient nor with nutrient and water levels. However, genus richness decreased at the warm side of the temperature gradient. Our experiment generally supports recent empirically based findings that a continuing temperature increase may result in lower genus richness and lower abundance of large-sized zooplankton grazers, the latter likely resulting in reduced control of phytoplankton.

Direct and indirect effects of additions of chromophoric dissolved organic matter on zooplankton during large‐scale mesocosm experiments in an oligotrophic lake

Summary The effects of changes in chromophoric dissolved organic matter (CDOM) on zooplankton grazers in pelagic food webs can be difficult to predict due to the potential for conflicting direct and indirect effects of CDOM on water column optics and food‐web dynamics. We compared the responses of two dominant zooplankton groups, Daphnia spp. and calanoid copepods, to elevated CDOM in two mesocosm experiments conducted in a transparent, oligotrophic lake. In the first experiment, low, medium and high additions of CDOM [dissolved organic carbon (DOC) = 2.7, 3.0 and 4.3 mg L−1, respectively] and non‐manipulated controls (DOC = 1.6 mg L−1) were used to test the hypothesis that food‐web stimulation will increase with CDOM concentration. In the second experiment, we manipulated both CDOM (control and addition) and ultraviolet radiation (UV; ambient and shielded) to determine the importance of CDOM as a UV screen, as well as to examine the role of UV in food‐web stimulation by CDOM. We also conducted short‐term bioassays alongside this second experiment to assess the food resources for Daphnia and calanoids in treatments with UV‐exposed and non‐UV‐exposed CDOM. Daphnia abundance increased in the low and medium CDOM additions in the first experiment, and when food resources were simultaneously stimulated by CDOM and protected from the direct negative effects of UV in the second experiment. In contrast, calanoid copepod abundance declined or remained unchanged when CDOM was added, and this response was not mediated by food resources. Overall, our findings suggest that increased CDOM in clear lakes could alter the relative abundance of zooplankton groups through a combination of direct and indirect effects.

Spatial changes in the vertical distribution of calanoid copepods down to great depths in the North Pacific.

Despite its ecological importance, little information is available regarding the spatial and vertical changes in the calanoid copepod community over large geographical regions. This study investigated the spatial and vertical patterns in calanoid copepod abundance and community structure using zooplankton samples collected between depths of 0 and 2,615 m across the North Pacific from 0° to 56°N. A total of 211 calanoid copepod species belonging to 66 genera and 24 families were identified. Calanoid copepod abundance decreased with increasing depth, and few latitudinal differences were detected. Across the entire region, species diversity peaked near 500 to 2,000 m in depth. The calanoid copepod community was separated into seven groups with distinct spatial and vertical distributions. For all groups, the number of species was low (28 to 37 species) in the subarctic region (north of 40°N) and high (116 to 121 species) in the subtropical-tropical region. The deepest group in the subtropical-tropical region was composed of cosmopolitan species, and this group was also observed in deep water in the subarctic region. Indeep water, most of the calanoid copepod community consisted of cosmopolitan species, while an endemiccommunity was observed in the subarctic region. Because the food of deep-sea calanoid copepods originates fromthe surface layer, sufficient and excess flux in the eutrophic subarctic region may be responsible for maintaining the endemic species in the region.

Variability in Calanus spp. abundance on fine- to mesoscales in an Arctic fjord: implications for little auk feeding

We studied the abundance of calanoid copepods of the genus Calanus in a high-resolution sampling grid located in the vicinity of a breeding colony of an avian Calanus predator, the little auk (Alle alle) in an Arctic fjord (Isfjorden, Svalbard) in July 2007. Within diving reach of little auks, all copepodite stages of C. finmarchicus, as well as stages CIII–CV of C. glacialis, were recorded in all 26 stations sampled. Spatial autocorrelation analysis was used to detect spatial heterogeneity (patches) in the distribution of Calanus spp. Positive spatial autocorrelation was detected on scales up to 1.2 km for C. finmarchicus stages CIII–CV and for C. glacialis CIV and CV, but was rarely detected for the younger stages. This suggests that the tendency to form patches varies with ontogeny in Calanus spp. At an adjacent little auk colony, the diet prey composition from 30 gular pouches of little auks returning from feeding trips was investigated. Calanus glacialis CIV and CV were numerically dominant in the prey samples, while C. finmarchicus CIV which was dominant in the net samples did not contribute to the little auk diet. This could suggest selective feeding, a detection of patches beyond the scale of our survey, feeding beyond the sampling area or a combination of these factors. Large Calanus abundance differences within the sampling grid underline the necessity of a proper choice of grid size, in this case 2 km between stations.

Distribution and Ecophysiology of Calanoid Copepods in Relation to the Oxygen Minimum Zone in the Eastern Tropical Atlantic

Oxygen minimum zones (OMZs) affect distribution patterns, community structure and metabolic processes of marine organisms. Due to the prominent role of zooplankton, especially copepods, in the marine carbon cycle and the predicted intensification and expansion of OMZs, it is essential to understand the effects of hypoxia on zooplankton distribution and ecophysiology. For this study, calanoid copepods were sampled from different depths (0–1800 m) at eight stations in the eastern tropical Atlantic (3°47′N to 18°S) during three expeditions in 2010 and 2011. Their horizontal and vertical distribution was determined and related to the extent and intensity of the OMZ, which increased from north to south with minimum O2 concentrations (12.7 µmol kg−1) in the southern Angola Gyre. Calanoid copepod abundance was highest in the northeastern Angola Basin and decreased towards equatorial regions as well as with increasing depth. Maximum copepod biodiversity was observed in the deep waters of the central Angola Basin. Respiration rates and enzyme activities were measured to reveal species-specific physiological adaptations. Enzyme activities of the electron transport system (ETS) and lactate dehydrogenase (LDH) served as proxies for aerobic and anaerobic metabolic activity, respectively. Mass-specific respiration rates and ETS activities decreased with depth of occurrence, consistent with vertical changes in copepod body mass and ambient temperature. Copepods of the families Eucalanidae and Metridinidae dominated within the OMZ. Several of these species showed adaptive characteristics such as lower metabolic rates, additional anaerobic activity and diel vertical migration that enable them to successfully inhabit hypoxic zones.

Hypoxia tolerance in the copepod Calanoides carinatus and the effect of an intermediate oxygen minimum layer on copepod vertical distribution in the northern Benguela Current upwelling system and the Angola–Benguela Front

There is a growing concern that hypoxic and anoxic areas in the sea spread in extent and intensity, posing a severe risk to marine ecosystems and fisheries. Hypoxia may affect fish stocks directly or via detrimental effects on important prey species, such as zooplankton. A unique feature of the northern Benguela Current upwelling region and Angola–Benguela frontal system is a pronounced intermediate oxygen minimum layer (IOML) at 60–500 m depth with oxygen concentrations ≤ 1.4 mg O 2l − 1 (minimum < 0.7 mg O 2l − 1). Field studies during February–March 2002 demonstrated that the abundance of calanoid copepods and the biomass of mesozooplankton in general were severely reduced within the IOML. The dominant copepod Calanoides carinatus showed a bimodal vertical distribution with parts of the population either comprising all developmental stages concentrated in the surface layer (0–60 m), or copepodids C5 diapausing below 400 m depth apparently avoiding the IOML. Accordingly, abundances of other calanoid copepods were higher at the surface and below 300 m than in the centre of the IOML. The scarcity of planktonic life within the IOML raises the question whether this layer represents an effective barrier for zooplankton vertical migrations. Especially in C. carinatus, ontogenetic vertical migration plays a key role in the retention of the population within the productive upwelling region and for the rapid re-colonisation of plumes of newly upwelled water. To address this issue, the hypoxia tolerance of C. carinatus was determined in a series of laboratory-based, closed-bottle experiments in January 2005. Copepods were kept in gas-tight bottles and the decreasing oxygen concentrations were monitored to establish their minimum oxygen demands. Although copepodids survived apparently unharmed at surprisingly low oxygen concentrations of ca. 1.5 mg O 2l − 1 , they could not tolerate oxygen levels < 1.1 mg O 2l − 1, implying that the core of the IOML, where O 2 concentrations are below this threshold, is uninhabitable for C. carinatus. In contrast, the IOML may represent a refuge from competition and predation for other copepod species specifically adapted to hypoxic environments.

Effects of fomesafen, alone and in combination with an adjuvant, on plankton communities in freshwater outdoor pond mesocosms

Ecotoxicological effects of the diphenyl ether herbicide fomesafen, applied alone or in combination with the adjuvant Agral 90 (mixture of polyethoxylated derivatives of nonylphenol), were assessed on planktonic communities in 18-m3 outdoor mesocosms during a nine-month study. Four mesocosms were treated with fomesafen only (nominal concentration: 40 microg/L), four were treated with the mixture fomesafen-Agral 90 (nominal concentration: 40 microg/L and 90 microg/L, respectively), and four were kept as the controls. Five treatments were performed every three weeks from April 18, 2000. Mean (+/- standard error [SE]) values of fomesafen concentration in water of 62.5 (+/-5.3) and 19.4 (+/-7.6) microg/L were measured at the end of the treatment period in fomesafen- and mixture-treated mesocosms, respectively. Fomesafen, either alone or in mixture with Agral 90, had a significant positive effect on the abundance and biovolume of Cyanobacteria, Cryptophyceae, Dinophyceae, and Bacillariophyceae. Chlorophyceae were inhibited by the herbicide and laboratory toxicity tests confirmed that green algae were more sensitive toward fomesafen than other algal classes. A positive effect of treatments on phytoplankton taxonomic diversity also was observed, indicating that, like natural disturbances of intermediate strength, xenobiotics sometimes may enhance the diversity of algal communities. Fomesafen alone did not have any clear effect on zooplankton. Abundance of calanoid copepods was reduced significantly in the mixture-treated ponds, suggesting either a direct effect of the adjuvant and/or an enhancement of herbicide toxicity by Agral 90. The abundance of other zooplanktonic herbivorous groups increased due to a reduced competition for food for herbivorous species and a higher availability of preys for predators. No algal bloom was observed in the treated ponds, presumably because of grazing pressure and the low availability of nutrients.

Seasonal and spatial variability of dominant copepods along a transect off Walvis Bay (23°S), Namibia

The study provides the first quantitative analysis of changes in zooplankton abundance and community structure in the Walvis Bay area, off Namibia, over a full seasonal cycle (February–December 2000). Zooplankton was collected monthly along a 90-nautical-mile transect. Calanoid copepods were numerically the most abundant mesozooplankton, Metridia lucens, Calanoides carinatus, Rhincalanus nasutus and Centropages brachiatus being the most common species, with each exhibiting a specific distribution pattern. Mean calanoid copepod abundance was lower during autumn, when upwelling was minimal, than during other times of the year. However, abundances were exceptionally low in September, when upwelling was most intense. Offshore transport is believed to be responsible for copepod losses from the area during that period. Abundances of C. carinatus and R. nasutus were high inshore between June and August, at the onset of the upwelling season, and peaked during October–December, towards the end of the upwelling season. These cool-water species were closely associated with upwelled water near the coast. The results concur with previous distribution patterns of zooplankton and their association with upwelling in Namibian waters. Findings suggest a possible decade-scale shift in the zooplankton community structure since the 1960s.

Estuarine calanoid copepod abundance in relation to season, salinity, and land-derived nitrogen loading, Waquoit Bay, MA

Calanoid copepod abundance and distribution were measured by monthly plankton tows from May through November in 1998 and March through August in 1999 in three subestuaries of the Waquoit Bay estuarine system. There was a dramatic seasonal change in the composition of calanoids in Waquoit Bay with a spring community consisting of Acartia hudsonica, Centropages hamatus, and Eurytemora affinis, replaced by Acartia tonsa in the summer. The abundance of A. hudsonica, A. tonsa, and C. hamatus was higher in the saltier reaches of the subestuaries, but the abundance of E. affinis and copepod nauplii was not affected by salinity. Even though different land-derived nitrogen loads created different concentrations of chlorophyll in the water of Waquoit Bay subestuaries, there was no apparent response in the abundance of most calanoid copepods to differences in nitrogen load to the subestuaries. The uncoupling of phytoplankton food from mesozooplankton consumers suggests that other factors such as water residence time, phytoplankton quality and composition, or variations in microzooplankton food play a role in the abundance dynamics of Waquoit Bay calanoid populations.

Annual pattern of calanoid copepod abundance, prosome length and minor role in pelagic carbon flux in the Solent, UK

Investigation of the calanoid copepods at a coastal station in the Solent, UK, over a 14 mo period revealed a numerical dominance by species of the genus Acartia (comprising A. bifilosa, A. clausi, A. discaudata and A. margalefi), and the species Temora longicornis and Centropages hamatus, with sporadic appearances of Paracalanus parvus and Pseudocalanus elongatus. There was clear seasonality in the abundance of calanoids, with total numbers being highest from May onwards, and low after October. Stage-specific prosome lengths varied with season, and in most cases were negatively correlated with temperature. Individual weights and abundance of the copepods, together with measures of temperature, were used to predict weight-specific growth and production rates using a published empirical relationship. Comparisons of annual copepod production with previous measures of annual primary production and production of bacteria and ciliates at this same site were made, and a carbon flow diagram was constructed. Calanoid copepod annual production was 32.2 mgC m -3 yr -1 .. This represents only 0.5 % of the total annual primary production, and 0.6 % of the annual primary production of algae >3 μm. Ciliate annual production was almost 2 orders of magnitude higher, and constituted 33 % of the total annual primary production. In other neritic studies (with water column depths <200 m) annual production by copepods has varied between 21 and 177 % of annual ciliate production, whereas at this Solent site the value was only 1.5 %. It is suggested that the low biomass (and production) achieved by calanoid copepods was the consequence of population loss through high local flushing rates, unfavourable feeding conditions resulting from high suspended particulate matter, and high levels of hydrocarbon contaminants in the area.

Egg production by the bay anchovy Anchoa mitchilli in relation to adult and larval prey fields

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 131:61-73 (1996) - doi:10.3354/meps131061 Egg production by the bay anchovy Anchoa mitchilli in relation to adult and larval prey fields Peebles EB, Hall JR, Tolley SG Abundances of copepod nauplii, copepodite/adult copepods, and the larvae of iteroparous anchovies (primarily the bay anchovy Anchoa mitchilli) were monitored in Tampa Bay, Florida (USA) at 2 wk intervals for 2 yr. All possible pairings of the 3 time-series variables yielded significant positive correlations. Nearly all (&GT98%) of the collected anchovy larvae occurred with prey (nauplius) densities higher than those reported to affect larval starvation (&LT100 l-1). The larval association with abundant prey could be explained as (1) the remnants of earlier larval starvation, or (2) spawning being concentrated in zooplankton-rich waters. To evaluate the 2 explanations, the diet of adult A. mitchilli was analyzed, and egg/adult prey surveys were conducted across a 290 km2 area of Tampa Bay. In 5 of the 6 spatial surveys, A. mitchilli egg abundance was correlated with the abundance of calanoid copepods, a principal adult prey item. Calanoids (primarily adult Acartia tonsa) were never correlated with net plankton biomass or with the eggs of the bay anchovy's congener, Anchoa hepsetus. Calanoids were aggregated near sites of stable freshwater discharge during a dry season, but became dispersed as discharge increased during a rainy season. Among spatial surveys, egg abundance exhibited a strong nonlinear relationship with calanoid aggregation (r2 = 0.96, n = 6, p = 0.001). Collectively, these findings suggest that the bay anchovy's size-specific fecundity is related to adult prey availability, with adult prey availability being represented by a combination of abundance and patchiness. We discuss relationships between spawning pattern and environmental instability, and suggest that iteroparity serves to fine-tune reproductive effort to environmental parameters that are relevant to larval survival. Variable fecundity . Larval survival . Plankton patchiness . Life-history strategy . Spawning season . Spawning location Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 131. Publication date: February 08, 1996 Print ISSN:0171-8630; Online ISSN:1616-1599 Copyright © 1996 Inter-Research.

An empirical analysis of zooplankton community size structure across lake trophic gradients1

The hypothesis was tested that zooplankton community size structure shifts toward an increased relative biomass of microzooplankton with increased lake trophy at 12 sites in Quebec. The seasonal mean abundance and biomass of ciliates, rotifers, nauplii, cladocerans, and cyclopoid copepods were significantly (P &lt; 0.1) related to lake trophy, but calanoid copepod abundance and biomass varied independently of lake trophy. Regressions of microzooplankton and macrozooplankton biomass with total phosphorus (TP) were highly significant (P &lt; 0.0001), and TP explained a large proportion of the total variation (microzooplankton: r2 = 0.72; macrozooplankton: r2 = 0.86). The regression models for microzooplankton and macrozooplankton were not significantly different, refuting the hypothesis that relative biomass changes with lake trophy. Further analysis with a community structure index (the slope of the log weight‐log abundance relationship) and mean lengths of various taxa indicated that zooplankton community size structure was not correlated with either TP or chlorophyll. On average, about 40% of the total zooplankton biomass is accounted for by microzooplankton in the Quebec lakes. The inverse relationship between body size and specific flux rates suggests that microzooplankton account for the major portion of zooplankton community rates.

On the Nutrition and Metabolism of Zooplankton XIV. Utilization of Lipid byCalanus HelgolandicusDuring Maturation and Reproduction

The abundance of calanoid copepods in marine plankton and their importance as food for certain fishes has prompted numerous studies of their biology, including several concerned with fecundity (Marshall &amp; Orr, 1952; Mullin &amp; Brooks, 1967; Paffenhöfer, 1970). These studies, however, have all involved animals maintained on various diets in the laboratory: data for egg-production byCalanusunder natural conditions in the sea are still needed.To ensure the survival of the young of many animal species to the stage of independent feeding, biochemical energy in the form of lipid is stored within the egg. During a recent survey ofCalanus helgolandicus(Claus) from the English Channel the level of lipid, mainly in the form of wax esters, in Stage V copepodids was found to be substantially greater than that in female adult stages (Gattenet al.1979). The difference was particularly noticeable during spring periods when egg-laying was in progress. This observation indicates a major role for wax esters during the reproduction ofCalanus.The present study seeks to establish the fate of the lipid reserves in Stage V and female adultCalanuswith particular emphasis on the extent to which the size of such reserves can be used as an index of the fecundity of this copepod.