Copepod Population Dynamics Research Articles

Population Dynamics of Copepods as Influenced by Heavy Metals in Khanki Headworks, Pakistan

Copepods grow in diverse freshwater habitats, totaling around 2,814 species. As foremost zooplankton, they lead biomass and are pivotal in aquatic ecosystems. The ever-increasing issue of heavy metals contamination affects organisms differently. Copepods, with their broad geographic range, can be valuable bio monitors for metal growth. Objective: To evaluate the effects of heavy metals and fish diversity on the population dynamics of copepods in Khanki Headworks, Pakistan. Methods: For the analysis of heavy metals month wise water samples (1000 ml) from four selected sites were collected for one year (February 2021 to January 2022). Atomic Absorption Spectrophotometry was employed for the analysis of heavy metals. Month wise copepods samples were collected with planktonic net (mesh size: 37µm). Results: In total, seven species and four genera of copepods were identified. Mesocyclops edax was the most dominant copepod species. Three heavy metals zinc (Zn), arsenic (As) and nickel (Ni) were estimated in following order of concentrations Zn> Ni> As. Conclusions: Current investigation revealed that heavy metals generally govern the population dynamics of copepods.

Seasonal Distribution of Copepods as Influenced by Physicochemical Parameters in Khanki Headworks, Pakistan

Copepods are tiny aquatic animals. Their role in aquatic food chains is very crucial as they are involved in organic matter circulation and energy transfer between different trophic levels. They are important source of food for fish larvae and zooplanktivorous fish. Objective: To assess the influence of environmental variables on the abundance, diversity and seasonal variations of planktonic copepods in Khanki Headworks, Pakistan. Methods: For the analysis of environmental variables monthly water samples from four selected sites were collected for a period of one year (February 2021 to January 2022). Environmental variables were analyzed in laboratory by following standard procedures. Month wise samples of copepods were collected with planktonic net (mesh size: 37µm) from four locations (each with 3 sub-sites). Results: In total, 7 species of Copepods belonging to 4 genera were identified from February 2021 to January 2022. Mesocyclops was observed as the most diverse genus (4 species), while Mesocyclops edax was the most prevalent copepod species. Population density and biodiversity were highest in June and minimum in January. Shannon-Weaver diversity index described greater diversity among copepod species in June. Pearson correlation and canonical correspondence analysis (CCA) revealed that electrical conductivity (EC), temperature, turbidity, pH and dissolved oxygen (DO) were important environmental variables affecting the biodiversity and density of copepods. Conclusions: This investigation elucidated that physicochemical parameters generally regulate the population dynamics of Copepods.

Naupliar exposure to acute warming does not affect ontogenetic patterns in respiration, body size, or development time in the cosmopolitan copepod Acartia tonsa.

Short-term, acute warming events are increasing in frequency across the world's oceans. For short-lived species like most copepods, these extreme events can occur over both within- and between-generational time scales. Yet, it is unclear whether exposure to acute warming during early life stages of copepods can cause lingering effects on metabolism through development, even after the event has ended. These lingering effects would reduce the amount of energy devoted to growth and affect copepod population dynamics. We exposed nauplii of an ecologically important coastal species, Acartia tonsa, to a 24-hour warming event (control: 18°C; treatment: 28°C), and then tracked individual respiration rate, body length, and stage duration through development. As expected, we observed a decrease in mass-specific respiration rates as individuals developed. However, exposure to acute warming had no effect on the ontogenetic patterns in per-capita or mass-specific respiration rates, body length, or development time. The lack of these carryover effects through ontogeny suggests within-generational resilience to acute warming in this copepod species.

Highlighting the promise of qPCR-based environmental monitoring: response of the ribosomal RNA:DNA ratio of calanoid copepods to toxic cyanobacteria.

Calanoid copepods are integral to aquatic food webs and may drive the bioaccumulation of toxins and heavy metals, spread of infectious diseases, and occurrence of toxic cyanobacterial harmful algal blooms (HABs) in freshwater aquatic systems. However, interrelationships between copepod and cyanobacterial population dynamics and ecophysiology remain unclear. Insights into these relationships are important to aquatic resource management, as they may help guide mitigation efforts. We developed a calanoid copepod qPCR assay to investigate how copepod abundance and physiological status relate to the abundance of cyanobacteria and the concentration of total microcystin in a HAB-prone freshwater multi-use eutrophic lake. Through in silico and in vitro validation of primers and analyses of time series, we demonstrate that our assay can be used as a reliable tool for environmental monitoring. Importantly, copepod RNA:DNA ratios on and shortly after the day when microcystin concentration was at its highest within the lake were not significantly lower (or higher) than before or after this period, suggesting that copepods may have been tolerant of microcystin levels observed and capable of perpetuating bloom events by consuming competitors of toxic cyanobacteria.

Seasonal dependence on seagrass detritus and trophic niche partitioning in four copepod eco-morphotypes

Benthic copepods dominate meiofaunal communities from marine phytodetritus, both in terms of numerical abundance and species diversity. Nevertheless, ecological factors driving copepod co-existence and population dynamics are still largely unknown. Here, we aimed to explore feeding habits of four copepod species commonly found in Mediterranean seagrass detritus accumulations, representing distinct eco-morphotypes (planktonic, phytal, epibenthic and mesopsammic). Joint use of fatty acid and stable isotope trophic markers showed that co-occurring harpacticoid copepods have diversified diets. Contrary to what was expected, microphytobenthos does not serve as their main food source. Instead, we found evidence from both techniques that major food items include heterotrophic biomass, macro-epiphytes and, depending on eco-morphology and season, of seagrass detritus-derived organic matter. Isotopic niches suggested that eco-morphotypes showed resource segregation. This segregation varies temporally, and partial overlap occurs between niches of phytal and epibenthic eco-morphotypes in some seasons. Our results highlight that, contrary to what is often assumed for meiofaunal consumers, considerable trophic diversity exists among copepod assemblages. They also indicate that, through multiple non-exclusive possible mechanisms, copepods could constitute a major link between seagrass detritus and associated biomass and higher trophic levels (namely macroinvertebrates and juvenile fish).

Trophic decoupling of mesozooplankton production and the pelagic planktivores sprat Sprattus sprattus and herring Clupea harengus in the Central Baltic Sea

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 592:181-196 (2018) - DOI: https://doi.org/10.3354/meps12512 Trophic decoupling of mesozooplankton production and the pelagic planktivores sprat Sprattus sprattus and herring Clupea harengus in the Central Baltic Sea Matthias Bernreuther1,4,*, Janna Peters1, Christian Möllmann1, Jasmin Renz2, Jörg Dutz3, Jens-Peter Herrmann1, Axel Temming1 1Institute of Hydrobiology and Fisheries Science, University of Hamburg, 22767 Hamburg, Germany 2Senckenberg am Meer, German Center for Marine Biodiversity Research, 20146 Hamburg, Germany 3Leibniz Institute for Baltic Sea Research, 18119 Rostock, Germany 4Present address: Thünen Institute of Sea Fisheries, 22767 Hamburg, Germany *Corresponding author: matthias.bernreuther@thuenen.de ABSTRACT: Quantitative analysis of the predation impact of planktivores on zooplankton is essential for proper understanding of energy flow and trophic coupling in ecosystems. To quantify trophic dynamics between zooplankton and small pelagic fish in the Baltic Sea, we conducted a temporally resolved investigation on the diet, feeding and predation impact of the dominant planktivorous fish species sprat Sprattus sprattus L. and herring Clupea harengus L. in the Central Baltic Sea (Bornholm Basin). Bi-weekly to monthly coverage between April 2002 and November 2003 included net sampling of copepods, determination of predator stock size using hydroacoustics and trawl surveys, and extensive stomach content sampling. Herring and sprat were mainly zooplanktivorous, feeding on the calanoid copepods Temora longicornis, Pseudocalanus acuspes and Acartia spp. and, in summer, on the cladocerans Bosmina spp. and Podon spp. We observed temporally high predation impact of sprat and herring on T. longicornis and P. acuspes in April and May, when more than the production of these 2 copepod species (copepodite stages C1-6) was consumed (consumption/production [C/P] > 3.5). However, the impact on the population dynamics of both copepods was negligible. Likewise, the impact on Acartia spp. was considered negligible (C/P < 0.1). Integrated over the year, utilization of estimated copepod production by both clupeids was comparatively low, with only 18% of the annual production of T. longicornis and 36% of the annual production of P. acuspes consumed; the production of Acartia species (1.4%) and cladocerans (2.3%) was almost completely unused. Use of only 9% of the combined production of copepods and cladocerans indicates poor trophic coupling between mesozooplankton and pelagic planktivores in the Central Baltic Sea. KEY WORDS: Predation impact · Zooplantivores · Open pelagic · Consumption versus production · Competition Full text in pdf format PreviousNextCite this article as: Bernreuther M, Peters J, Möllmann C, Renz J, Dutz J, Herrmann JP, Temming A (2018) Trophic decoupling of mesozooplankton production and the pelagic planktivores sprat Sprattus sprattus and herring Clupea harengus in the Central Baltic Sea. Mar Ecol Prog Ser 592:181-196. https://doi.org/10.3354/meps12512 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 592. Online publication date: March 29, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Egg Development Time (EDT) in &amp;lt;i&amp;gt;Mesocyclops ogunnus&amp;lt;/i&amp;gt;

A study was carried out on the impacts of temperature and light/dark regime on the Egg Development Time (EDT) of the cyclopoida copepod, Mesocyclops ogunnus in Lake Kinneret. It was found that EDT was 148, 33 and 20 hours under 15°C, 22°C, and 27°C respectively. EDT was different between the two regimes of 12/12 hrs light/dark and 24 hrs light. Egg hatching and survival were higher under 24 hrs light regime. The results of temperature and light regime impacts on EDT indicate ecological implication on cyclopoida copepod population dynamics in lakes. The implication of the results to the global warming trend is also suggested.

Identification of some common food items in the guts of fish larvae and juveniles in the Black Sea

Over the past decade the positive trends in the average annual number of fish larvae and in the copepod population dynamics in the coastal area of the Black Sea agree. The increased fish larvae abundance is hypothesized due to improvement of their nutrition associated with the drastic increase in number of introduced invasive cyclopoid copepod Oithona davisae. This assumption is difficult to be verified through fish gut content analysis in absence of methodology allowing prey species identification from their fragmentary residual remnants. Our paper offers an original approach to identification of several common copepod prey using specific distinctive features detected on their chitin fragments from guts of fish larvae and juveniles. To identify specific features of the common species from the coastal areas off Sevastopol (Acartia tonsa, Oithona davisae, Longipedia sp., Cyclopina sp.), alive copepods were isolated from the samples and reared as monospecific cultures in laboratory. Images of alive copepods of each species at successive stages of development and their moulted exoskeletons were compared with the images of chitin remnants found in the fish guts. This technique discloses relatively intact specific morphological features remaining undigested in chitin fragments of prey. These species-specific taxonomic features are suggested to be used for trophic analysis of the Black Sea fishes at early stages of development. Application of proposed method is helpful for assessment of qualitative and quantitative composition of consumed prey and selectivity of fish, especially during the changes in zooplankton community structure affecting significantly survival of fish generations.

Temporal changes in pelagic copepod assemblages off Ubatuba, Brazil

AbstractThe inner shelf waters off Southeastern Brazil are periodically enriched by bottom intrusions of the cold and nutrient‐rich South Atlantic Central Water (SACW), which is transported offshore by the Brazil Current. This study examined the temporal contrasts in abundance and structure of pelagic copepod assemblages in a neritic station off Ubatuba, in relation to hydrography and phytoplankton biomass, to investigate the effects of SACW bottom intrusions on copepod population dynamics during three consecutive years. The water‐column characteristics shifted from a well‐mixed, more turbid and phytoplankton‐poor scenario during subsidence conditions to a stratified, less turbid and high Chl‐a concentration scenario during SACW bottom intrusions, leading to increased copepod diversity, abundance, and biomass. The rise in copepod diversity during SACW intrusions was related to the contribution of oceanic species in addition to coastal water species. The copepod community was numerically dominated by small‐sized species, such as Oncaea waldemari, Oithona plumifera, and clausocalanid and paracalanid copepodids, regardless of seasonality and SACW intrusions. Some large calanoid species contributed considerably to the total copepod biomass during intrusions. In addition to confirming that SACW seasonal intrusions play a key role in pelagic processes off Southeast Brazil, this study showed that the multiannual variability of SACW seasonal intrusions is important in regulating the structure and dynamics of copepod communities in this subtropical area.

Impacts of mercury exposure on life history traits of Tigriopus japonicus: Multigeneration effects and recovery from pollution

Here, through a multigenerational life-cycle test, Tigriopus japonicus were exposed to different mercuric chloride treatments in seawater (nominal concentrations of 0, 0.5, 1, 10, and 50μg/L) for five successive generations (F0–F4), and subsequently all the treatments were recovered in clean environments for one generation (F5). Six life history traits (survival, developmental time for nauplius phase, developmental time to maturation, fecundity, number of clutches, and number of nauplii/clutch) were examined for each generation. Mercury (Hg) accumulation was also analyzed for the adult copepods in the F1, F3, and F5. The results indicated that Hg accumulated in a dose-dependent manner for the F1, F3, and F5 generations. Moreover, higher Hg contents were observed in F3 than F1 at the same exposure levels. Among the six life history traits, only fecundity and number of nauplii/clutch showed a greater sensitivity to Hg toxicity, and the inhibitory effects worsened from F0 to F3, which was explained by a trend for higher metal accumulation with increasing generations. In the recovery generation (F5), none of the traits differed from the control, highlighting that Hg might not induce any epigenetic or parental effects in the following generations. Thus, we hypothesized that although cumulative effects might have been involved in Hg multigenerational toxicity, physiological acclimation, that is, phenotypic plasticity could explain Hg tolerance obtained by marine copepods. Impacts on important life history traits could disturb the population dynamics of some important marine copepods, hence having unexpected ecological consequences in the marine ecosystem. Yet, the Hg harmful impacts rapidly fade away as the Hg is cleared from the environment.

Consequences of a cyanobacteria bloom for copepod reproduction, mortality and sex ratio

The aim of the study was to measure copepod reproduction, mortality and sex ratio in the field before, during and after a cyanobacteria bloom during the summer in the western Gulf of Finland. Environment and zooplankton samples were collected every fortnight, and the copepod Acartia spp. was incubated in the laboratory for reproductive output, i.e. egg production and egg hatching success. Other responses monitored were female:male ratio, mortality and body condition. In addition, molecular analyses of the nodularin-producing cyanobacterium Nodularia in Acartia gut contents (GCs) were assessed. Egg production and body condition decreased with increasing Nodularia GCs. During the bloom, hatching decreased as a response to Nodularia in the copepod gut. Although not related to cyanobacteria variables, male mortality was higher than female mortality, resulting in a female-biased sex ratio over most of the summer. The study demonstrates that Acartia reproductive output is constrained by cyanobacteria blooms in the Baltic Sea, and more generally that copepod population dynamics may be negatively affected by such blooms. This is especially significant considering that toxin-producing blooms are predicted to increase due to warming.

Population dynamics of calanoid copepods in the subtropical mesohaline Danshuei Estuary (Taiwan) and typhoon effects

AbstractWe studied the populations of the dominant calanoid copepods Pseudodiaptomus annandalei and Acartia spp. in the mesohaline Danshuei Estuary for two successive springs and summers. We analyzed environmental factors (i.e., temperature, salinity, chlorophyll a, light attenuation coefficient, and suspended particulate matter) and the population densities and structures at the surface and near the estuarine bed. The population of P. annandalei dominated the zooplankton community from surface to bottom, except during a medusa bloom in 2009 and during the post‐typhoon period, when Acartia spinicauda dominated. The relationships between environmental factors and densities differed between and within populations of P. annandalei and Acartia spp. We concluded that the primary determinants of the P. annandalei population are predation and the typhoon‐related freshwater runoff, which can strongly influence the copepod succession in this part of the estuary.

Sensitivity of copepod populations to bottom-up and top-down forcing: a modeling study in the Gulf of Maine region

The spatio-temporal variability of marine copepods, like other aquatic and terrestrial organisms, is controlled by both bottom-up (through changes in food resource) and top-down (through changes in predation) forcing. Canonically, climate-related changes in hydrography, nutrient chemistry and circulation can modulate phytoplankton production, thus imposing a bottom-up control on marine copepods, whereas human activities such as fishing may affect the predation mortality of copepods through food-web re-organization such as trophic cascading. Evaluating the sensitivity of copepod populations to bottom-up and topdown forcing is an essential step toward the prediction of future marine planktonic ecosystem changes. In this study, we used a coupled hydrodynamics/food-web/ population-dynamics model to identify the key processes controlling the observed seasonality and distributional patterns of two copepod groups in the Gulf of Maine (GoM) region, including Pseudocalanus spp. and Centropages typicus. Numerical experiments were conducted to assess the sensitivity of the modeled species to changes in phytoplankton biomass and bloom timing, as well as the changes in mortality regime. The results show that both copepod groups are more sensitive to changes in mortality rates than to food availability and peak timing. Bottom-up processes alone cannot explain the observed variability in Pseudocalanus and Centropages population sizes, while top-down controls play a critical role in copepod population dynamics in the GoM region.

A critical body residue approach for predicting persistent bioaccumulative toxicant effects on reproduction and population dynamics of meiobenthic copepods

Critical body residues (CBRs) are the measured tissue toxicant concentrations yielding a median dose-response on a dry-weight or lipid-normalized basis. They facilitate management decisions for species protection using tissue analysis. Population CBR is the mean dose yielding 50% population suppression and was predicted here in Amphiascus tenuiremis for fipronil sulfide (FS) using lifetables and the Leslie matrix. Microplate bioassays (ASTM E-2317-14) produced biomass sufficient for dry mass and lipid-normalized CBR estimates of reproduction (fertility) and population growth suppression. Significant FS toxic effects were delayed naupliar development (at ≥0.10 µg L(-1)), delayed copepodite development (at 0.85 µg L(-1)), decreased reproductive success (at ≥ 0.39 µg L(-1)), and decreased offspring production (at 0.85 µg L(-1)). A reproductive median effective concentration (EC50) of 0.16 µg L(-1) (95% CI: 0.12-0.21 µg L(-1)) corresponded to an adult all-sex CBR and lipid-normalized CBR of 0.38 pg FS · µg(-1) dry weight (95% CI: 0.27-0.52 pg FS · µg(-1)) or 2.8 pg FS · µg(-1) lipid (95% CI: 2.2-3.6 pg FS · µg(-1)), respectively. Copepod log bioconcentration factor (BCF) = 4.11 ± 0.2. Leslie matrix projections regressed against internal dose predicted fewer than five gravid females in a population by the third generation at 0.39 and 0.85 µg FS · L(-1) (i.e., 9.6-10.2 µg FS · µg(-1) lipid), and 50% population suppression at a CBR of 1.6 pg FS · µg(-1) lipid. This more integrative population CBR as a management tool would fall 1.75 times below the CBR for the single most sensitive endpoint-fertility rate.

Invasive copepods in the Lower Columbia River Estuary: Seasonal abundance, co-occurrence and potential competition with native copepods

As part of a multi-year field study to investigate plankton dynamics in the Lower Columbia River Estuary (LCRE), we conducted monthly sampling of the mesozooplankton (> 73 μm) at a station near Astoria, Oregon. The planktonic copepod community was numerically dominated by three non-indigenous species (NIS), Pseudodiaptomus forbesi, Limnoithona tetraspina, and Sinocalanus doerrii, and two native species, Eurytemora affinis and Diacyclops thomasi. However, seasonal co-occurrence of non-indigenous and native copepods was highly variable between species-pairs. The native E. affinis and the non-indigenous S. doerrii showed the greatest temporal overlap (March-October), but other species-pairs also showed periods of considerable overlap during some seasons (e.g., E. affinis and P. forbesi in June-September). Spatial co-occurrence of native and non-indigenous species was also examined in temperature and salinity “space” (rather than geographic space): all six species-pairs (3 non-indigenous species × 2 native species) showed some degree of overlap, with the greatest (proportional) overlap occurring between the native E. affinis and the two nonindigenous species, S. doerrii and P. forbesi. This suggests the potential for competition to occur between native and non-native copepods in the LCRE, although with variation between seasons and species. Future studies are recommended that explicitly test for and distinguish between the relative importance of biological (e.g., competition and predation) and physico-chemical processes (e.g., freshwater runoff, eutrophication) in regulating the population dynamics of native and invasive copepods in the LCRE.

Zooplankton time series in the coastal zone off Chile: Variation in upwelling and responses of the copepod community

Two zooplankton time series from the coastal upwelling region off Chile were studied in terms of copepod biomass and abundance in relation with upwelling variation. The time series from Antofagasta (23°S) was collected between 1988 and 2008 and based on bi-annual sampling, whereas the time series from Concepción (36°S) was based on monthly samples between 2002 and 2008. In both sites, Ekman transport was derived from local wind obtained at coastal stations as an upwelling index. At both sites Ekman transport exhibited a seasonal patterns characterized by stronger upwelling during the spring–summer, although Ekman transport was stronger in northern Chile. Ekman transport also revealed three distinct periods of upwelling intensity between 1988 and 2008 in northern Chile. Copepod biomass varied in association with these periods, as follows: (1) 1988–1997 with a positive linear trend, (2) an abrupt decline in 1998–2000 after the 1997–1998 El Niño, and (3) a negative trend associated with increased upwelling from 2001 to 2008. A negative trend of zooplankton biomass and copepod abundance also occurred at Concepción during the period 2002–2008. Seasonal peaks in copepod biomass also coincided with the upwelling season (spring–summer). The correlation between variation in upwelling and copepod biomasses in northern Chile suggested that population dynamics of copepods may depend on intensity of upwelling. Although the underlying mechanisms are unclear, and several hypotheses dealing with bottom-up or top down factors can be put forth, our findings suggest that upwelling intensity operates through an optimal window for copepod abundance and biomass and increasing upwelling in the last decade (2000–2008) may has been unfavorable for copepod populations.

Heat shock protein expression during stress and diapause in the marine copepod Calanus finmarchicus

Calanoid copepods, such as Calanus finmarchicus, are a key component of marine food webs. C. finmarchicus undergo a facultative diapause during juvenile development, which profoundly affects their seasonal distribution and availability to their predators. The current ignorance of how copepod diapause is regulated limits understanding of copepod population dynamics, distribution, and ecosystem interactions. Heat shock proteins ( Hsps) are a superfamily of molecular chaperones characteristically upregulated in response to stress conditions and frequently associated with diapause in other taxa. In this study, 8 heat shock proteins were identified in C. finmarchicus C5 copepodids ( Hsp21, Hsp22, p26, Hsp90, and 4 forms of Hsp70), and expression of these transcripts was characterized in response to handling stress and in association with diapause. Hsp21, Hsp22, and Hsp70A (cytosolic subfamily) were induced by handling stress. Expression of Hsp70A was also elevated in shallow active copepodids relative to deep diapausing copepodids, which may reflect induction of this gene by varied stressors in active animals. In contrast, expression of Hsp22 was elevated in deep diapausing animals; Hsp22 may play a role both in short-term stress responses and in protecting proteins from degradation during diapause. Expression of most of the Hsps examined did not vary in response to diapause, perhaps because the diapause of C. finmarchicus is not associated with the extreme environmental conditions (e.g., freezing and desiccation) experienced by many other taxa, such as overwintering insects or Artemia cysts.

Calanoid copepod resting egg abundance and hatching success in the sediment of the Seine estuary (France)

Benthic, viable resting eggs of calanoid copepods were found for the first time in the Seine estuary (France) during July 2008. Vertical distribution of the resting eggs in the sediment was determined up to 10 cm depth. Hatching success of the eggs extracted from different 1-cm thick sediment layers was experimentally tested immediately after extraction and after a long refractory phase (i.e. 11 months) of storage at low temperature (4–5 °C). The hatching success of resting eggs obtained immediately after sediment incubation was lower (0.72%) than the value observed after 11 months (4.50%) with an overall hatching success of 2.37%. The marine, calanoid copepod Temora longicornis was the primary species to hatch from the eggs; however, the estuarine calanoid copepod Eurytemora affinis also hatched from resting eggs. The mean abundance of eggs found in sediment (1.42 × 10 6 eggs m −2) was comparable to that reported for other marine and estuarine calanoid copepods. The Seine estuary sediment had a high variability of egg abundance (between 0.14 and 8.10 × 10 7 eggs m −3) suggesting that the hydrodynamics of this macrotidal estuary are likely responsible for this variability. Significant sediment resuspension occurs in the Seine estuary during flood periods and spring tides leading to resting eggs to contribute along the year to the nauplii recruitment of calanoid copepods. On average, around 400,000 nauplii m −3 month −1 of the main calanoid copepods can emerge from the surface layer sediment in the Seine estuary, suggesting that resting eggs could play an important role in the population dynamics of key calanoid copepods in the Seine estuary.

Explaining regional variability in copepod recruitment: Implications for a changing climate

Characterizing environmental effects on copepod production and their ecological roles is complicated by multiple physical (e.g. temperature) and biological (e.g. food, predation) factors controlling multiple aspects of copepod physiology and demography. For example, data for two regions in eastern Canada (St. John’s, Newfoundland and Halifax, Nova Scotia) indicate that subtle differences in environmental conditions lead to significant differences in seasonal copepod ( Calanus finmarchicus) recruitment timing and magnitude. Here, we quantify how environmental variability influences C. finmarchicus physiology and demography leading to observed regional and seasonal variations in abundance off St. John’s and Halifax. We apply a stochastic individual-based model (IBM) for copepod population dynamics to simulate the seasonal variation in C. finmarchicus abundance of egg through copepodite 1 (C1) stages at the two sites using year-specific local forcing from multi-year data. The model includes individual variability in development, egg production and mortality rates with resulting seasonal C1 abundance averaged among years and compared to analogous observations. We find temperature has a dominant effect on both development and egg production rates while egg recruitment is affected by temperature and female abundance at both sites. We show that mortality rate characterization has a strong influence on modeled abundances, and site-specific environmentally dependent mortality rates are necessary to produce results consistent with observations (temperature vs. food vs. cannibalism via females). Results indicate that prediction of climate change effects on copepod abundance and their ecological roles requires consideration of biological (e.g. chlorophyll a, female abundance) as well as physical (e.g. temperature) factors. In particular, estimates of abundances during the onset of C1 recruitment (i.e. their arrival on the larval fish prey field) are improved by 67–94% when the influence of biological factors on mortality rates are considered.

Improving ecological forecasts of copepod community dynamics using genetic algorithms

The validity of computational models is always in doubt. Skill assessment and validation are typically done by demonstrating that output is in agreement with empirical data. We test this approach by using a genetic algorithm to parameterize a biological–physical coupled copepod population dynamics computation. The model is applied to Cape Cod Bay, Massachusetts, and is designed for operational forecasting. By running twin experiments on terms in this dynamical system, we demonstrate that a good fit to data does not necessarily imply a valid parameterization. An ensemble of good fits, however, provides information on the accuracy of parameter values, on the functional importance of parameters, and on the ability to forecast accurately with an incorrect set of parameters. Additionally, we demonstrate that the technique is a useful tool for operational forecasting.