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Estimating In Situ Zooplankton Non-Predation Mortality in an Oligo-Mesotrophic Lake from Sediment Trap Data: Caveats and Reality Check.

Dubovskaya OP, Tang KW, Gladyshev MI, Kirillin G, Buseva Z, Kasprzak P, Tolomeev AP, Grossart HP - PLoS ONE (2015)

Bottom Line: Mortality due to non-predation factors is often ignored even though anecdotal evidence of non-predation mass mortality of zooplankton has been reported repeatedly.Zooplankton carcasses may be exposed to water column microbes for days before entering the benthos; therefore, non-predation mortality affects not only zooplankton population dynamics but also microbial and benthic food webs.This would be particularly important for carbon and nitrogen cycles in systems where recurring mid-summer decline of zooplankton population due to non-predation mortality is observed.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biophysics, Siberian Branch of the Russian Academy of Sciences, 50/50 Akademgorodok, Krasnoyarsk, 660036, Russia; Siberian Federal University, 79 Svobodny avenue, Krasnoyarsk, 660041, Russia.

ABSTRACT

Background: Mortality is a main driver in zooplankton population biology but it is poorly constrained in models that describe zooplankton population dynamics, food web interactions and nutrient dynamics. Mortality due to non-predation factors is often ignored even though anecdotal evidence of non-predation mass mortality of zooplankton has been reported repeatedly. One way to estimate non-predation mortality rate is to measure the removal rate of carcasses, for which sinking is the primary removal mechanism especially in quiescent shallow water bodies.

Objectives and results: We used sediment traps to quantify in situ carcass sinking velocity and non-predation mortality rate on eight consecutive days in 2013 for the cladoceran Bosmina longirostris in the oligo-mesotrophic Lake Stechlin; the outcomes were compared against estimates derived from in vitro carcass sinking velocity measurements and an empirical model correcting in vitro sinking velocity for turbulence resuspension and microbial decomposition of carcasses. Our results show that the latter two approaches produced unrealistically high mortality rates of 0.58-1.04 d(-1), whereas the sediment trap approach, when used properly, yielded a mortality rate estimate of 0.015 d(-1), which is more consistent with concurrent population abundance data and comparable to physiological death rate from the literature.

Ecological implications: Zooplankton carcasses may be exposed to water column microbes for days before entering the benthos; therefore, non-predation mortality affects not only zooplankton population dynamics but also microbial and benthic food webs. This would be particularly important for carbon and nitrogen cycles in systems where recurring mid-summer decline of zooplankton population due to non-predation mortality is observed.

No MeSH data available.


Related in: MedlinePlus

Turbulent mixing within the water column during the field experiment.Turbulent diffusion coefficient KZ averaged for the study period (thick solid line) and the dissipation rate of the turbulent kinetic energy (thin dash lines are individual profiles; thick dash line is the average for the whole study).
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pone.0131431.g003: Turbulent mixing within the water column during the field experiment.Turbulent diffusion coefficient KZ averaged for the study period (thick solid line) and the dissipation rate of the turbulent kinetic energy (thin dash lines are individual profiles; thick dash line is the average for the whole study).

Mentions: The weather was calm during the study with daily mean wind speed <2 m s-1; surface water temperature increased from 19.5°C on 3rd July to 23°C on 10th July (Fig 2A). A strong thermocline began at 8 m, and temperature at the sediment trap depth (12 m) was ca. 7°C (Fig 2B). ε decreased from 5×10−9 m2 s-3 at 8 m to 5×10−10 m2 s-3 at 20 m and remained close to the detection limit below (Fig 3). In the epilimnion, ε increased rapidly from ~10−8 m2 s-3 at 5 m to ~10−5 m2 s-3 at 1.5 m, characteristic of turbulence produced by wind shear and surface wave breaking [21]. KZ was close to kinematic molecular viscosity (~10−6 m2 s-1) in the metalimnion, increased slightly in the deeper water, and was high (~10−4 m2 s-1) across the surface mixed layer (Fig 3). Overall, the water column was characterized by a shallow epilimnion exposed to wind mixing, a strong thermocline, and a cold hypolimnion with low mixing intensity between ~15 m and 65 m. Therefore, the bulk of the water column was a nearly homogeneous non-turbulent environment, close to the classical Stokes’ condition.


Estimating In Situ Zooplankton Non-Predation Mortality in an Oligo-Mesotrophic Lake from Sediment Trap Data: Caveats and Reality Check.

Dubovskaya OP, Tang KW, Gladyshev MI, Kirillin G, Buseva Z, Kasprzak P, Tolomeev AP, Grossart HP - PLoS ONE (2015)

Turbulent mixing within the water column during the field experiment.Turbulent diffusion coefficient KZ averaged for the study period (thick solid line) and the dissipation rate of the turbulent kinetic energy (thin dash lines are individual profiles; thick dash line is the average for the whole study).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4492990&req=5

pone.0131431.g003: Turbulent mixing within the water column during the field experiment.Turbulent diffusion coefficient KZ averaged for the study period (thick solid line) and the dissipation rate of the turbulent kinetic energy (thin dash lines are individual profiles; thick dash line is the average for the whole study).
Mentions: The weather was calm during the study with daily mean wind speed <2 m s-1; surface water temperature increased from 19.5°C on 3rd July to 23°C on 10th July (Fig 2A). A strong thermocline began at 8 m, and temperature at the sediment trap depth (12 m) was ca. 7°C (Fig 2B). ε decreased from 5×10−9 m2 s-3 at 8 m to 5×10−10 m2 s-3 at 20 m and remained close to the detection limit below (Fig 3). In the epilimnion, ε increased rapidly from ~10−8 m2 s-3 at 5 m to ~10−5 m2 s-3 at 1.5 m, characteristic of turbulence produced by wind shear and surface wave breaking [21]. KZ was close to kinematic molecular viscosity (~10−6 m2 s-1) in the metalimnion, increased slightly in the deeper water, and was high (~10−4 m2 s-1) across the surface mixed layer (Fig 3). Overall, the water column was characterized by a shallow epilimnion exposed to wind mixing, a strong thermocline, and a cold hypolimnion with low mixing intensity between ~15 m and 65 m. Therefore, the bulk of the water column was a nearly homogeneous non-turbulent environment, close to the classical Stokes’ condition.

Bottom Line: Mortality due to non-predation factors is often ignored even though anecdotal evidence of non-predation mass mortality of zooplankton has been reported repeatedly.Zooplankton carcasses may be exposed to water column microbes for days before entering the benthos; therefore, non-predation mortality affects not only zooplankton population dynamics but also microbial and benthic food webs.This would be particularly important for carbon and nitrogen cycles in systems where recurring mid-summer decline of zooplankton population due to non-predation mortality is observed.

View Article: PubMed Central - PubMed

Affiliation: Institute of Biophysics, Siberian Branch of the Russian Academy of Sciences, 50/50 Akademgorodok, Krasnoyarsk, 660036, Russia; Siberian Federal University, 79 Svobodny avenue, Krasnoyarsk, 660041, Russia.

ABSTRACT

Background: Mortality is a main driver in zooplankton population biology but it is poorly constrained in models that describe zooplankton population dynamics, food web interactions and nutrient dynamics. Mortality due to non-predation factors is often ignored even though anecdotal evidence of non-predation mass mortality of zooplankton has been reported repeatedly. One way to estimate non-predation mortality rate is to measure the removal rate of carcasses, for which sinking is the primary removal mechanism especially in quiescent shallow water bodies.

Objectives and results: We used sediment traps to quantify in situ carcass sinking velocity and non-predation mortality rate on eight consecutive days in 2013 for the cladoceran Bosmina longirostris in the oligo-mesotrophic Lake Stechlin; the outcomes were compared against estimates derived from in vitro carcass sinking velocity measurements and an empirical model correcting in vitro sinking velocity for turbulence resuspension and microbial decomposition of carcasses. Our results show that the latter two approaches produced unrealistically high mortality rates of 0.58-1.04 d(-1), whereas the sediment trap approach, when used properly, yielded a mortality rate estimate of 0.015 d(-1), which is more consistent with concurrent population abundance data and comparable to physiological death rate from the literature.

Ecological implications: Zooplankton carcasses may be exposed to water column microbes for days before entering the benthos; therefore, non-predation mortality affects not only zooplankton population dynamics but also microbial and benthic food webs. This would be particularly important for carbon and nitrogen cycles in systems where recurring mid-summer decline of zooplankton population due to non-predation mortality is observed.

No MeSH data available.


Related in: MedlinePlus