Influence of diatoms on copepod reproduction. I. Field and laboratory observations related to Calanus helgolandicus egg production

Abstract

Egg production rates (EPR) by Calanus helgolandicus females were investigated with specimens sampled weekly, from April to November 2003 and from March to October 2004, at a station located in the English Channel off Roscoff. Comparison of results between 1994Comparison of results between , 2003Comparison of results between and 2004 showed that C. helgolandicus was a late spawner in 1994 and became an early spawner in 2003 and 2004. In all cases high variations in EPR were observed, which could not be correlated to phytoplankton biomass, expressed as diatom, chlorophyll a, particulate carbon and nitrogen concentrations in 2003 and 2004. Neither were they correlated to food quality, expressed as C/N ratio. To explain this mismatch between EPR and food concentration, a series of mixed phytoplankton species dominated by diatoms (≥11 µm filtrate representing natural diatom assemblages: NDA) and 7 single diatom species, all occurring during blooms in the field, were assayed as diets with C. helgolandicus females. Ingestion of diatoms by females was estimated by faecal pellet production rates and complementary scanning electron microscopy examinations of diatom remains in pellets. Depending on diatom species in diets, EPR was either increased or depressed 2 to 3 d after food uptake by females had started. The EPR decrease was reversible, when diatom diets were replaced by the dinoflagellate Prorocentrum minimum. This effect was also observed when females were transferred to natural phytoplankton populations from the English coast of the Channel close to Plymouth, where food composition in the field differed compared to that off Roscoff. EPR ceased completely when the concentration of NDA diets was artificially increased, but recovered after a shift to a dinoflagellate diet. These results indicate that phytoplankton dominated by diatoms can impair C. helgolandicus egg production in the field. This effect was not related to the production of polyunsaturated aldehydes by diatoms. Limitations due to unidentified essential compounds not provided by the metabolism of diatoms, or unknown diatom-derived toxins, were probably involved. KEY WORDS: Copepod · Diatom · Egg production · English Channel Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 308: [129][130][131][132][133][134][135][136][137][138][139][140][141][142] 2006 the hatching success and larval development of copepods, mediated by deleterious polyunsaturated aldehydes (Miralto et al. 1999, Pohnert et al. 2002, Adolph et al. 2004, Ianora et al. 2004), but egg production can also vary significantly depending on diet. Patterns of variability in egg production conform to changes in dinoflagellate and microzooplankton biomass (Kleppel et al. 1991), as well as to phytoplankton blooms mostly dominated by diatoms (Runge & Plourde 1996, Meyer-Harms et al. 1999). The varying influence of different algae on these stages of ontogenesis has been documented by several laboratory studies (Ban et al. 1997, Pohnert et ...

Effect of food concentration and type of diet on Acartia survival and naupliar development

“…The negative effect was weaker than starvation, but strong enough to make mixtures with adequate food supply of Rhodomonas and T. weissflogii inadequate. This contrasts with previous studies which used P. minimum as a control treatment against the negative impacts of diatoms as T. rotula on copepod hatching success (Chaudron et al 1996) and embryonic (Poulet et al 1994) as well as postembryonic development (Carotenuto et al 2002), and to reverse effects of diatom monodiets on copepod egg production (Poulet et al 2006). P. minimum Fig.…”

“…Since the mid 1990s, there have been an increasing number of culture studies demonstrating a detrimental impact of diatoms on copepod larval development (Ianora et al 2004;Poulet et al 1994), including species of the genus Acartia . While some laboratory studies have shown that diatoms can also suppress egg production and hatching rates of copepods (Ianora et al 1995(Ianora et al , 2003, others show that copepod egg production can be increased or unaffected depending on the diatom species in the diet (Poulet et al 2006). Contrasting effects of diatom diet on copepods are reported from the field.…”

Copepod growth and diatoms: insensitivity of Acartia tonsa to the composition of semi-natural plankton mixtures manipulated by silicon:nitrogen ratios in mesocosms

“…Meanwhile aldehydes and fatty acid hydroperoxides have been identified as the toxic compounds (Ianora et al 2004;Wichard et al 2005;Fontana et al 2007) and it has been shown that these compounds are produced by mechanical cell rupture (Pohnert 2000;Fontana et al 2007). The toxic effect has been identified as being particularly harmful to embryogenesis and thus to reduce the hatching success of eggs (Chaudron et al 1996;Poulet et al 2006). In other laboratory studies, no toxic effect was found, but under some environmental conditions, poor food quality, e.g.…”

Copepod reproduction is unaffected by diatom aldehydes or lipid composition

“…This gradual decrease in hatching could still indicate a depletion or accumulation of other, bioactive or essential compounds controlling egg viability, but it might not necessarily be caused by a single factor. Hitherto unknown toxins might cause the failure of egg production or hatching on diatom diets, as recently suggested by Poulet et al (2006), but yet lack support from experimental studies and specific chemical analyses.…”

“…Some studies suggest an impaired reproduction of copepods associated with various diatom blooms in the field (Miralto et al 1999;Poulet et al 2006;Vargas et al 2006). Despite variable copepod egg production and egg hatching, however, no general negative relationship to diatom biomass has yet been established in various ecosystems (Laabir et al 1998;Irigoien et al 2002).…”