Partition of planktonic respiratory carbon requirements during a phytoplankton spring bloom

Abstract

We studied the effect of variable phytoplankton biomass and dominance of the diatom Skeletonema marinoi on the planktonic community respiratory carbon requirement over a period of 14 d (14 to 28 April 2008) in 3 different mesocosms filled with natural water at Espegrend marine biological field station in Raunefjord, Norway. The carbon requirement was measured on mesozooplankton (the calanoid copepod Calanus finmarchicus) and 3 other size fractions of plankton -< 200 µm (dominated by microzooplankton), <15 µm (dominated by nanoplankton including most of the phytoplankton) and particles passing GF/C filters (dominated by bacterioplankton) -by measuring oxygen consumption using an optode system with 2 SensorDish Readers. The respiratory carbon requirement showed no clear trend over time for any of the 4 groups. The mesozooplankton contributed the least to the total community carbon requirement, corresponding to < 6% of primary production. In contrast, microzooplankton and nanoplankton consistently dominated the community carbon requirement, corresponding to > 50% of the primary production, while bacterioplankton showed an intermediate and variable contribution (ca. < 20% with a maximum of 50%). Feeding experiments on mesozooplankton (C. finmarchicus) 2 d before the peak in phytoplankton biomass showed that the copepods ingested from 2.4 to 4.3 times their respiratory carbon requirements, thus providing a high potential for growth. Respiratory carbon requirements of mesozooplankton were not significantly related to dominance or quantity of food available, whereas the respiratory carbon requirements of other groups were all related to the production of 22:6(n-3) fatty acid. The present study confirms the important role of microorganisms in the biological carbon transformation through the food web during a phytoplankton spring bloom. KEY WORDS: Plankton community · Respiratory carbon requirement · Energy transfer · Skeletonema marinoi · Mesozooplankton · Calanus Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 451: 15-29, 2012 16 Rivkin & Legendre 2001), whereas others suggest that bacterioplankton represent less (Ducklow et al. 2000) and that algal respiration (Lancelot et al. 1991) and microzooplankton (Calbet & Landry 2004) account for the bulk of community respiration in some eutrophic ecosystems. Consequently, the balance between photosynthesis and respiration will be strongly influenced by the quantitative relationships between microzooplankton, phytoplankton and bacterioplankton.Mesozooplankton respiration rate is an estimation of their minimum energetic requirements under given conditions, in terms of carbon (Hernández-León & Gómez 1996), thus representing the amount of energy necessary to maintain the structure and activity at this trophic level (Alcaraz & Packard 1989). Mesozooplankton is generally assumed to respire less than the smaller size groups, but, depending on the region studied and method of estimation, the mesozooplankton have been estim...

Plankton Community Metabolism Variations in Two Temperate Coastal Waters of Contrasting Nutrient Richness

“…In both sites a clear link between nutrient dynamics and metabolic activity was observed. The changes in nutrients and standing biomasses coincided with increased CR during the spring bloom, supporting established findings on the positive relationship between blooms and CR (e.g., Iriarte et al., 1991; Md Amin et al., 2012). The negative significant relationship between DIN and CR can be further explained by the fact that DIN is readily utilized by phytoplankton during production, leading to increased CR as labile organic matter becomes available both for heterotrophs and autothrophs (Mantikci et al., 2017, 2020; Sadro et al., 2011, 2014).…”

“…Consequently, these altered interactions could lead to distinct microbial loop patterns in the carbon cycle, ultimately impacting CR. A study using mesocosm experiments in a Norwegian fjord showed that during the spring bloom, microzooplankton and nanoplankton have carbon requirements equivalent to more than half of primary production, while bacterioplankton are intermediate and variable (Md Amin et al., 2012). Perhaps because of this, the role of other heterotrophs in CR outweighs that of the bacterial compartment, which may explain why we were unable to detect significant seasonal differences.…”

Increased microbial activity in a warmer and wetter climate enhances the risk of coastal hypoxia

“…Respiration measurements were taken with a dynamic luminescence quenching-based system (Sensor Dish Reader, SDR2; PreSens GmbH, Germany) to allow continuous measuring. This system has been used previously in a similar way (Warkentin et al, 2007(Warkentin et al, , 2011Amin et al, 2012). Two plates containing 24 samples of 5 mL each were incubated at each temperature, and respiration measurements were performed for 12 h to obtain a sufficient oxygen change.…”