Biomass and productivity responses of zooplankton communities to experimental thermocline deepening

Sastri, Akash R.; Gauthier, Joanna; Juneau, Philippe; Beisner, Beatrix E.

doi:10.4319/lo.2014.59.1.0001

Cited by 26 publications

(22 citation statements)

References 41 publications

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“…However, high assimilation of diatoms during fall mixing did not result in a high biomass of Daphnia. We speculate that increasing mixing depth was probably unfavorable to vertically migrating Daphnia because it increases mortality, accompanying a reduction in hypolimnetic refuge volume (Sastri et al 2014).…”

Section: Discussionmentioning

confidence: 93%

Eutrophication and browning influenceDaphnianutritional ecology

et al. 2019

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Climate change and land use practices can enhance lake eutrophication and browning, which influence phytoplankton composition by decreasing the availability of food high in nutritional quality (algae) and increasing the abundance of low-quality food (terrestrial detritus, bacteria) for herbivorous zooplankton. Nutritionally valuable algae for zooplankton are rich in essential biomolecules such as amino acids, polyunsaturated fatty acids (PUFA), sterols, and phosphorus. We performed laboratory experiments and showed a stronger positive relationship between zooplankton (Daphnia) cumulative offspring number and availability of high-quality algae (Cryptophytes: Rhodomonas/Cryptomonas; and Chrysophytes: Mallomonas) than with intermediate-quality (Chlorophytes: Acutodesmus) or poor-quality (Dinoflagellates: Peridinium) algae. The higher cumulative offspring number of Daphnia was a result of higher amounts of total ω-3 and ω-6 PUFA, proteins, sterols, and amino acids in the algal diets. The experiments also showed that even a small addition of high-quality algae (Rhodomonas) to intermediate-quality (Acutodesmus) or low-quality diets (bacteria, heterotrophic nanoflagellates, or terrestrial organic matter) can enhance the Daphnia cumulative offspring production. Our carbon mass balance calculation for a eutrophic clearwater lake and an oligotrophic polyhumic lake showed that the abundance of highquality phytoplankton (cryptophytes, chrysophytes, diatoms) among total particulate organic carbon was minor (8.7% [SD 2.4%] and 6.5% [7.0%]). We modeled Daphnia diets (i.e., resource assimilation) using a fatty acid mixing model. Our analyses showed that Daphnia were able to locate high-quality algae (cryptophytes, chrysophytes, and diatoms) more effectively during cyanobacteria blooms in a eutrophic lake (55% [SD 12%]) than in a polyhumic lake (25% [10%]). Nevertheless, our results show that intense eutrophication and browning diminish assimilation of high quality algae, limiting Daphnia biomass production.

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Section: Discussionmentioning

confidence: 93%

Eutrophication and browning influenceDaphnianutritional ecology

et al. 2019

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“…biomass, body size; Gliwicz, ). However, a greater overall zooplankton biomass with thermocline deepening also points to a signal of increased reproductive rates and secondary production in the altered community, as we have demonstrated elsewhere for 1 year (2010) of this study (Sastri et al ., ). In addition to these treatment effects, we also observed some important interannual variation in the experimental responses, indicating that predation effects may accumulate over time.…”

Section: Discussionmentioning

confidence: 97%

“…These observations thus only partially support our hypothesis that Zoo:Chl should decline in our experiment as a result of increased fish predation because such large biomass increases in small zooplankton were not originally accounted for. On the other hand, the fact that total zooplankton biomass increased supports our hypothesis that increased TP with thermocline deepening may have produced a bottom‐up effect; an observation that is supported by the higher zooplankton production measured (only in 2010) in the experimental basins (Sastri et al ., ). From the zooplankton composition changes observed here, however, we predict that the positive fish biomass response to thermocline deepening observed over these two experimental years (Gillespie, ) may be unsustainable.…”

Section: Discussionmentioning

confidence: 97%

Thermocline deepening and mixing alter zooplankton phenology, biomass and body size in a whole‐lake experiment

2014

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1. Summer thermal stratification is thought to be one of the key structuring physical factors for north temperate lake zooplankton. Shifts associated with climate change may lead to altered thermocline depths in stratified lakes through changes to (i) wind stress and associated water column mixing or (ii) air temperature and precipitation. The effects of thermocline deepening through these two scenarios were simulated in a whole-lake experiment to assess the effects on the phenology, biomass and mean body size of the zooplankton. 2. The thermocline of a three-basin dimictic lake was deepened to 7-8 m in one basin using a lake mixer. Through heat transfer, the thermocline of the adjacent basin was deepened to 6-7 m, while the third basin served as an unmanipulated control (4-5 m deep thermocline). Zooplankton community dynamics were followed weekly in a control year and in two experimental years. A before-after-control-impact (BACI) statistical protocol was used to assess the effects of two treatments: Deepening and Deepening+Mixing. 3. Thermocline depth was the main factor influencing zooplankton changes. The biomass and late-season dominance by smaller-bodied and more fish-evasive species were favoured by deepening, leading to a decline in mean community body size, but an increase in total biomass. 4. While many effects could be attributed to thermocline deepening, additional or exacerbated responses were observed when mixing was also present. This resulted mostly from a loss of the hypolimnetic refuge for zooplankton, which accentuated predation effects by warm-water fish on larger cladocerans. Overall, our treatments promoted top-down (predation) effects that increased over the 2 years of the experiment.

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“…While the timing of the early season sampling is the same in both years, the timing of the late season sampling differs between years owing to logistical constraints (i.e., timing of In Year 2 (2014), the thermal structure of Experimental Lake was manipulated using a solar-powered hydraulic lift system (Medora Corporation SolarBee 10000v18), which pumps water up from a selected depth and redistributes it to the surface. This is the same system used in other whole-lake manipulations that assessed the biological effects of changing thermocline depth (Cantin et al 2011;Jobin and Beisner 2014;Sastri et al 2014). The SolarBee was deployed by helicopter into the deep area of the lake on 15 June 2014.…”

Section: Whole-lake Experimentsmentioning

confidence: 99%

A whole‐lake experiment confirms a small centric diatom species as an indicator of changing lake thermal structure

Saros

Northington

Anderson

et al. 2016

Limnol Oceanogr Letters

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In many lakes across the Northern Hemisphere, paleolimnological records have revealed that the relative abundances of the small centric diatom, Discostella stelligera, changed over the past century, with these widespread shifts attributed to climate change. Specifically, small‐scale experiments and current spatial distribution patterns suggested that this species is more abundant when lake mixing depths are shallower, but a direct test of this hypothesis at the whole‐lake scale was lacking. We conducted a whole‐lake mixing manipulation in a remote arctic lake that normally has relatively shallow thermal stratification and abundant D. stelligera populations during the summer. We employed a “Before‐After‐Control‐Impact” design using an experimental lake and a control lake. Lake thermal structure and diatom populations were monitored in both lakes in summer 2013 without manipulating either lake, and again in summer 2014 when the experimental lake was manipulated to achieve deeper mixing depths. The abundance of D. stelligera declined during the manipulated period of deeper mixing in 2014, while it increased during the same time frame in the control lake. The same pattern was not observed for the four other diatom taxa found in both lakes in both years. Our results confirm the use of D. stelligera as an indicator of changing lake thermal structure, and suggest that the broader application of this tool to lake sediment records will yield greater insight into longer‐term variability in the response of lake ecosystems to climate.

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Biomass and productivity responses of zooplankton communities to experimental thermocline deepening

Cited by 26 publications

References 41 publications

Eutrophication and browning influenceDaphnianutritional ecology

Eutrophication and browning influenceDaphnianutritional ecology

Thermocline deepening and mixing alter zooplankton phenology, biomass and body size in a whole‐lake experiment

A whole‐lake experiment confirms a small centric diatom species as an indicator of changing lake thermal structure

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