Differential Impacts of Copepods and Cladocerans on Lake Seston, and Resulting Effects on Zooplankton Growth

Becker, Claes; Feuchtmayr, Heidrun; Brepohl, Daniela C.; Santer, Barbara; Boersma, Maarten

doi:10.1023/b:hydr.0000041603.41913.95

Cited by 24 publications

(19 citation statements)

References 48 publications

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“…However, the time-response of the RNA: DNA ratio may be slower in Eurytemora than in Daphnia owing to lower growth rates and longer generation times of copepods than those of cladocerans (Becker et al 2004). This may have led to a temporal decoupling between zooplankton and seston, so that the RNA:DNA ratio of zooplankton sampled at a given station could instead integrate the signal of an earlier feeding episode on some other seston of different quality.…”

Section: Apparent Decoupling Between Seston Fa Composition and Zooplamentioning

confidence: 99%

Relating RNA:DNA ratio in Eurytemora affinis to seston fatty acids in a highly dynamic environment

Pommier¹,

Frenette

Glémet³

2010

Mar. Ecol. Prog. Ser.

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Nine stations were sampled across the St. Lawrence estuarine transition zone (ETZ) in summer 2006 in order to investigate the variability in Eurytemora affinis growth condition, as revealed by RNA:DNA ratios, and its relationship to the nutritional quality of seston, expressed in terms of fatty acid (FA) composition. The population of E. affinis in the St. Lawrence ETZ was under the influence of brackish waters, as well as fresh and saline waters landwards and seawards of the frontal mixing zone, respectively. The RNA:DNA ratio for E. affinis throughout the ETZ ranged from 2.14 to 23.01, with an average value of 10.30 ± 4.35. When compared with the previously reported RNA:DNA ratio for copepods under optimal growth conditions, our values suggest that the summertime population of E. affinis in the St. Lawrence ETZ was in good growth condition. The hydrodynamic imprint within the St. Lawrence ETZ translated into the distribution pattern of seston having various FA compositions. Freshwater seston was of better nutritional quality (i.e. richer in essential fatty acids) than that from brackish and more saline waters. However, this did not translate into a significantly different E. affinis RNA:DNA ratio between the 3 types of waters. Yet, the growth condition of E. affinis under the influence of fairly stable fresh waters was associated with the relative abundance of 20:5n3-rich seston advected from upstream despite the low contribution of chl a to total suspended particulate matter. Moreover, a comparison between seston and zooplankton FA composition revealed the potential trophic transfer of diatom-related FA from producers to consumers within fresh waters. No such correlations were evidenced within the most dynamic parts of the ETZ (brackish and more saline waters) where the relationship between E. affinis growth condition and seston quality was likely constrained by a spatial-temporal decoupling between seston and zooplankton.KEY WORDS: Eurytemora affinis · RNA:DNA ratio · Fatty acids · Estuarine transition zone · St. Lawrence River Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 400: [143][144][145][146][147][148][149][150][151][152][153][154] 2010 The zooplankton assemblage in the St. Lawrence ETZ is dominated by Eurytemora affinis. This calanoid copepod plays an important role in the trophic dynamics of the St. Lawrence upper estuary where it feeds on phytoplankton (Winkler et al. 2003), mainly freshwater species advected from upstream (Lapierre & Frenette 2008), as well as on aggregates and attached bacteria (Zimmermann-Timm 2002, Martineau et al. 2004). E. affinis is amongst the major prey items for anadromous fish larvae (Winkler et al. 2003, Barnard et al. 2006, such as Microgadus tomcod and Osmerus mordax, which may colonize downstream environments later in their ontogenic cycle. Given its key trophic position within the St. Lawrence ETZ, E. affinis may therefore be considered an important regulator of the biological connectivity between the St...

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Section: Apparent Decoupling Between Seston Fa Composition and Zooplamentioning

confidence: 99%

Relating RNA:DNA ratio in Eurytemora affinis to seston fatty acids in a highly dynamic environment

Pommier¹,

Frenette

Glémet³

2010

Mar. Ecol. Prog. Ser.

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“…The role of the intermediate trophic level (mainly occupied by ciliates, but also some heterotrophic dinoflagellates) was clearly evident in numerous mesocosm experiments where plankton assemblages were subject to different copepod densities (BECKER et al, 2004;BURNS and SCHALLENBERG, 1996;FEUCHTMAYR et al, 2004;GRANÉLI and TURNER, 2002;SOMMER, F. et al 2005;SOMMER, F. et al 2005;SOMMER et al, 2001SOMMER et al, , 2004SOM-MER and SOMMER, 2006). Copepods always suppressed larger and medium sized protozoa, thus relaxing their predatory impact on heterotrophic nanoflagellates and nanophytoplankton, which could compensate the top-down effect of copepods on larger phytoplankton.…”

Section: Omnivory and Intermediate Trophic Levelsmentioning

confidence: 99%

Trophic Cascades in Marine and Freshwater Plankton

Sommer

2008

International Review of Hydrobiology

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Transmission of top-down control from fish to phytoplankton via crustacean mesozooplankton is a cornerstone of limnetic plankton ecology. Such trophic cascades are less frequently reported from the marine pelagic. In this article a case is made for consideration of scale issues and for the distinction between full (affecting entire trophic levels) and partial (affecting only some functional groups) trophic cascades. Partial cascades are more widespread while the full cascades are either ephemeral or depend on the suppression of compensatory growth of the predation-resistant size-fractions of phytoplankton. This suppression can only be achieved if there is a persistent coexistence between zooplankton feeding on different parts of the phytoplankton size spectrum. This condition is fulfilled in plankton communities where microphageous cladocerans (mainly Daphnia) and microphageous copepods coexist (many lake communities) or where krill and copepods coexist (high latitude marine communities). It is not fulfilled in many temperate and low-latitude marine communities where copepods effectively suppress filter-feeding appendicularians. Thus, the observed difference in the frequency of marine and limnetic pelagic cascades is considered real.Are all trophic cascades wet? STRONG et al., 1992

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“…This has previously been shown in freshwater ecosystems, where copepod grazing positively affected Daphnia growth (Becker et al 2004). In marine systems this nonselective feeding could be played by ciliates, appendicularians (Bedo et al 1993), or by cladocerans.…”

Section: Mesocosmsmentioning

confidence: 62%

“…The effects have been studied on various levels from bacteria to zooplankton (see F. U. Sommer et al 2001Zö llner et al 2003;Becker et al 2004). In this paper we focus on interactions between the phytoplankton community and the nutritional status of the zooplankton.…”

Section: Methodsmentioning

confidence: 99%

Impacts of copepods on marine seston, and resulting effects on Calanus finmarchicus RNA:DNA ratios in mesocosm experiments

et al. 2004

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We investigated the impact of copepods on the seston community in a mesocosm set-up, and assessed how the changes in food quantity, quality and size affected the condition of the grazers, by measuring the RNA:DNA ratios in different developmental stages of Calanus finmarchicus. Manipulated copepod densities did not affect the particulate carbon concentration in the mesocosms. On the other hand, chlorophyll a content increased with higher copepod densities, and increasing densities had a positive effect on seston food quality in the mesocosms, measured as C:N ratios and x3:x6 fatty acid ratios. These food quality indicators were significantly correlated to the nutritional status of C. finmarchicus. In contrast to our expectations, these results suggest a lower copepod growth potential on higher quality food. However, in concordance with earlier studies, we found that when copepods were in high densities the large particles (>1000 lm 3 ) decreased and that the smaller particles (<1000 lm 3 ) increased in number. These patterns were closely linked to the condition of C. finmarchicus, which were of better condition (RNA:DNA ratios) with increasing biovolumes of large particles, and, conversely, lower RNA:DNA ratios with increasing biovolumes of smaller particles. Consequentially, the selective grazing by copepods stimulated increased biovolumes of smaller plankton, and this increase was responsible for the increased food quality, in terms of C:N and x3:x6 ratios. Thus, we conclude that the decreasing growth potentials of C. finmarchicus were a result of a decrease of favourably sized food particles, induced by copepod grazing.

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Differential Impacts of Copepods and Cladocerans on Lake Seston, and Resulting Effects on Zooplankton Growth

Cited by 24 publications

References 48 publications

Relating RNA:DNA ratio in Eurytemora affinis to seston fatty acids in a highly dynamic environment

Relating RNA:DNA ratio in Eurytemora affinis to seston fatty acids in a highly dynamic environment

Trophic Cascades in Marine and Freshwater Plankton

Impacts of copepods on marine seston, and resulting effects on Calanus finmarchicus RNA:DNA ratios in mesocosm experiments

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