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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

Photo of the sediment trap.
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pone.0131431.g001: Photo of the sediment trap.

Mentions: Three pairs of sediment traps were deployed at 12 m (± 1 m) in the lower part of the thermocline each day for 6 consecutive days. Each trap, after the design of Håkanson [28], consisted of a pair of cylindrical collectors with a closing mechanism (Fig 1). Each collector had the dimensions of 0.077 m dia. × 0.485 m height; the height-to-diameter ratio therefore satisfied the recommended value to prevent resuspension [29]. Before deploying, the cylinders were filled with water from 12 m pre-screened through a 90 μm mesh; no poison was used. The cable was anchored, stretched by a submerged buoy and marked by a surface buoy. Trap exposure time was 1 day, except on 10th July when the exposure time was 20 hours. After traps retrieval, zooplankton samples from the paired collectors were pooled, concentrated on a 90 μm mesh and processed to obtain Y in Eq 6.


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)

Photo of the sediment trap.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0131431.g001: Photo of the sediment trap.
Mentions: Three pairs of sediment traps were deployed at 12 m (± 1 m) in the lower part of the thermocline each day for 6 consecutive days. Each trap, after the design of Håkanson [28], consisted of a pair of cylindrical collectors with a closing mechanism (Fig 1). Each collector had the dimensions of 0.077 m dia. × 0.485 m height; the height-to-diameter ratio therefore satisfied the recommended value to prevent resuspension [29]. Before deploying, the cylinders were filled with water from 12 m pre-screened through a 90 μm mesh; no poison was used. The cable was anchored, stretched by a submerged buoy and marked by a surface buoy. Trap exposure time was 1 day, except on 10th July when the exposure time was 20 hours. After traps retrieval, zooplankton samples from the paired collectors were pooled, concentrated on a 90 μm mesh and processed to obtain Y in Eq 6.

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