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Journal ArticleDOI

Long‐term responses of zooplankton to invasion by a planktivorous fish in a subarctic watercourse

01 Jan 2009-Freshwater Biology (Wiley)-Vol. 54, Iss: 1, pp 24-34
TL;DR: Increased predation pressure following the vendace invasion induced many effects on the crustacean zooplankton, and this paper documents comprehensive and strong direct and indirect long-term impacts of an introduced non-native predator on the native prey community.
Abstract: Summary 1. Introduced or invading predators may have strong impacts on prey populations of the recipient community mediated by direct and indirect interactions. The long-term progression of predation effects, covering the invasion and establishment phase of alien predators, however, has rarely been documented. 2. This paper documents the impact of an invasive, specialized planktivorous fish on its prey in a subarctic watercourse. Potential predation effects on the crustacean plankton, at the community, population and individual levels, were explored in a long-term study following the invasion by vendace (Coregonus albula). 3. Over the 12-year period, the density and species richness of zooplankton decreased, smaller species became more abundant and Daphnia longispina, one of the largest cladocerans, was eliminated from the zooplankton community. 4. Within the dominant cladocerans, including Daphnia spp., Bosmina longispina and Bosmina longirostris, the body size of ovigerous females and the size at first reproduction decreased after the arrival of the new predator. The clutch sizes of Daphnia spp. and B. longirostris also increased. 5. Increased predation pressure following the vendace invasion induced many effects on the crustacean zooplankton, and we document comprehensive and strong direct and indirect long-term impacts of an introduced non-native predator on the native prey community.

Summary (2 min read)

Jump to: [INTRODUCTION][METHODS][RESULTS][DISCUSSION] and [Legends to figures:]

INTRODUCTION

  • Of alien species represents one of the greatest threats to global biodiversity (Gido & Brown, 1999; Davis, 2003).
  • Thus, based on short-term studies, it is not possible to conclude which mechanisms drive the changes in the prey community or to quantify the rates of change, precluding in-depth understanding and predictions.
  • In addition to the numerical, direct effects of predation, prey populations may be affected by invasive predators via trait-mediated interactions (Bolker et al., 2003).
  • Accordingly, in several cladoceran species a smaller size at first reproduction has been demonstrated to occur with increasing predation pressure from fish (Stibor, 1992; Vonder Brink & Vanni, 1993; Weber & Declerck, 1997).

METHODS

  • The Pasvik water system (69oN, 29oE) originates from Lake Inari (1102 km2) in Finland, runs into Russia and then defines the border between Norway and Russia for a length of about 120 km.
  • The lake is dimictic, oligotrophic and humic with a Secchi-depth from 2-4 m.
  • From each sampling occasion, the body size of Daphnia spp. was measured under a binocular microscope with 40 X magnification on 50 females and, when possible, on up to 40 females with subitaneous eggs.
  • Binary logistic regressions were performed with the number of eggs (one or two) as the dependent variable, and body length and year as independent variables.

RESULTS

  • The total density of crustacean zooplankton showed a strong negative trend during the study period, including a sharp decrease from 1991 to 1993, followed by a recovery in abundance in 1995, and thereafter a steep decline towards 2002 (Fig. 2a).
  • Excluding this species from the analyses gave a significant overall decline in the total density of other zooplankton species over the time period from 1991 to 2002 (Linear regression; P<0.05, R2=0.44).
  • The most abundant cladocerans were Bosmina longirostris, Bosmina longispina and Daphnia cristata, whereas Daphnia longiremis, Daphnia longispina (O.F.M), Ceriodaphnia quadrangula (O.F.M), Holopedium gibberum Zaddach and Leptodora kindtii occurred more occasionally.
  • The size at first reproduction decreased significantly over the study period for the two Bosmina species (Fig. 5; Table 2; logistic regression: P<0.001 for both species), with the largest decrease being observed in B. longispina.
  • The size at first reproduction also decreased significantly in Daphnia spp. during the study, but with a less clear-cut trend than for the Bosmina species (Table 2; logistic regression: P<0.05).

DISCUSSION

  • Throughout the whole study, the zooplankton community in Ruskebukta was dominated by small cladocerans, in particular D. cristata, B. longispina and B. longirostris.
  • The present findings confirm that efficient and selective predation by vendace may have very strong effects on the density and composition of the zooplankton community, and also demonstrate the impact of an invading predator on its prey community.
  • The size at first reproduction also decreased during the study period in all the examined cladoceran species, and B. longispina seemed to be the most affected.
  • Whatever the actual mechanisms are in the present system, the observed decreases in size at first reproduction demonstrate severe impacts of the alien predator even on life history traits of the prey populations.
  • The authors also acknowledge two anonymous referees for their helpful comments and suggestions.

Legends to figures:

  • Relative contribution of vendace in gillnet catches from the pelagic fish community in Ruskebukta during the time period from 1991 to 2002.
  • Stippled line represents asymptotic power curve fitted to the data.
  • Fig. 2. Total density (a), species diversity (b) and relative species composition (c) of the crustacean zooplankton community in Ruskebukta during the study period.
  • For equations and statistics of regression lines, see Table 1. Fig.
  • Size at first reproduction (body length with 50% egg-bearing females, EL50) of B. longispina and B. longirostris during the study period.

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1
Long-term responses of zooplankton to invasion by a
planktivorous fish in a subarctic watercourse
Per-Arne Amundsen*, Anna Siwertsson*, Raul Primicerio* & Thomas hn*
§
* Department of Aquatic Biosciences, Norwegian College of Fishery Science, University of
Tromsø, Tromsø, Norway
§
Norwegian Institute of Gene Ecology, Breivika, Tromsø, Norway
Correspondence: Per-Arne Amundsen, Norwegian College of Fishery Science, University of
Tromsø, N-9037 Tromsø, Norway.
E-mail: Per-Arne.Amundsen@nfh.uit.no
Keywords: invasion, zooplankton, planktivory, Daphnia, Bosmina, predation
Published in Freshwater Biology (2009) 54, 24–34. doi: 10.1111/j.1365-
2427.2008.02088.x

2
Summary
1. Introduced or invading predators may have strong impacts on prey populations of the
recipient community mediated by direct and indirect interactions. The long-term progression
of predation effects, covering the invasion and establishment phase of alien predators,
however, has rarely been documented.
2. This paper documents the impact of an invasive, specialised planktivorous fish on its prey
in a subarctic watercourse. Potential predation effects on the crustacean plankton, at the
community, population and individual levels, were explored in a long-term study following
the invasion by vendace (Coregonus albula).
3. Over the 12-yr period, the density and species richness of zooplankton decreased, smaller
species became more abundant, and Daphnia longispina, one of the largest cladocerans, was
eliminated from the zooplankton community.
4. Within the dominant cladocerans, including Daphnia spp., Bosmina longispina and
Bosmina longirostris, the body size of ovigerous females and the size at first reproduction
decreased after the arrival of the new predator. The clutch sizes of Daphnia spp. and B.
longirostris also increased.
5. Increased predation pressure following the vendace invasion induced many effects on the
crustacean zooplankton, and we document comprehensive and strong direct and indirect long-
term impacts of an introduced non-native predator on the native prey community.

3
INTRODUCTION
The introduction of alien species represents one of the greatest threats to global biodiversity
(Gido & Brown, 1999; Davis, 2003). Introduced predators may have a particularly strong
impact on recipient communities due to a high vulnerability of naïve prey to new predators
(Park, 2004). Prey naiveté is most common in freshwater ecosystems (Cox & Lima, 2006),
and isolated environments like lakes and islands are particularly sensitive to predator
introductions (Kaufman, 1992; Courchamp et al., 2003). In lakes, invasive predators may
even be able to drive native species to extinction (Zaret & Paine, 1973; Witte et al., 1992).
Classic examples of strong predatory impacts include lacustrine introductions of
planktivorous fish that have caused extinction of large-sized zooplankton species (Hrbáček et
al., 1961; Brooks & Dodson, 1965).
Most studies of predation effects on zooplankton are short-term comparisons of the prey
communities before and after predator introductions, or comparisons of similar systems with
and without the predator (Hrbáček et al., 1961; Brooks & Dodson, 1965; Hall et al., 1976;
DeMelo, France & McQueen, 1992). Such short-term surveys may lack the power to separate
weak trends from natural variations (Elliott, 1994). Furthermore, such snapshot studies can
not distinguish between direct and indirect effects of predator introductions, and do not
provide any information on the transitory dynamics between different prey community states.
Thus, based on short-term studies, it is not possible to conclude which mechanisms drive the
changes in the prey community or to quantify the rates of change, precluding in-depth
understanding and predictions. Long-term studies of predator impact on prey are necessary to
obtain information on relevant mechanisms and transient dynamics, but have rarely been
performed (Strayer et al., 2006). The present contribution relates to the introduction and

4
invasion of an alien fish species, the vendace Coregonus albula (Linnaeus, 1758), in a
subarctic watercourse, examining the long-term effects on the planktonic prey community
over a 12-yr period during the establishment of this specialised zooplanktivore.
Predation by planktivorous fish has large impacts on the dynamics and structure of
zooplankton communities (Zaret, 1980; Lazzaro, 1987; Gliwicz & Pijanowska, 1989). The
primary, direct effect is an increased mortality rate of the prey. However, predation is often
highly selective and most planktivorous fish are visual predators that select the largest visible
prey (O'Brien, 1987; Gliwicz & Pijanowska, 1989; Lampert & Sommer, 1997). Cladocerans
are often preferred prey since they have a conspicuous pattern of motion (Zaret, 1980) and are
easy to capture compared to copepods which have a more effective escape response (O'Brien,
1987; Lampert & Sommer, 1997). The egg clutches carried by gravid cladocerans may further
increase their vulnerability, and selection of ovigerous females and females carrying a large
number of eggs may strengthen the predation effects on prey density, composition and
demography (Gliwicz, 1981; Dawidowicz & Gliwicz, 1983).
In addition to the numerical, direct effects of predation, prey populations may be affected by
invasive predators via trait-mediated interactions (Bolker et al., 2003). Several cladoceran
species are able to adjust their life-history in response to increased predation risk detected via
chemical cues associated with digested prey (Stabell, Ogbebo & Primicerio, 2003; Pohnert,
Steinke & Tollrian, 2007). Cues associated with predation risk from fish are known to
anticipate the onset of reproduction in order to increase the chance of reproducing
successfully before being eaten (Taylor & Gabriel, 1992; Larsson & Dodson, 1993; Lass &
Spaak, 2003). Accordingly, in several cladoceran species a smaller size at first reproduction
has been demonstrated to occur with increasing predation pressure from fish (Stibor, 1992;

5
Vonder Brink & Vanni, 1993; Weber & Declerck, 1997). Clutch size has also been found to
increase when predation from fish intensifies (Dodson, 1989; Stibor, 1992; Vonder Brink &
Vanni, 1993). Hence, increased predation from planktivorous fish may result in a multitude of
effects, mediated by direct and indirect interactions, including a decrease in zooplankton
abundance (Gliwicz, 1981; Hamrin & Persson, 1986; Persson et al., 2004), changes in
community and population structure towards smaller species and smaller individuals within
the species (Brooks & Dodson, 1965; Hall, Cooper & Werner, 1970), life-history
modifications (Stibor, 1992; Weider & Pijanowska, 1993) and morphological adaptations
(Dodson, 1988, 1989; Kolar & Wahl, 1998).
Few studies have addressed the impacts of zooplanktivore fish in subarctic and arctic systems
and, to our knowledge, long-term studies of the impact of invasions in the subarctic are absent.
These systems are presently undergoing changes associated with climate warming that are
expected to favour the successful invasion of specialist planktivores (Primicerio et al., 2007).
It is therefore important to document and understand the long-term implications of such
invasions. In the subarctic Pasvik water system, northern Norway, the opportunity to study
long-term ecological responses during the establishment of an alien predator arose when
vendace invaded the watercourse in the late 1980’s (Amundsen et al., 1999). The vendace is a
highly specialised zooplanktivore (e.g., Svärdson, 1976; Hamrin, 1983; Bøhn & Amundsen,
1998) and established successfully as the dominant pelagic fish species during the 1990’s
(Amundsen et al., 1999; Bøhn et al., 2004). Whitefish (Coregonus lavaretus (Linnaeus, 1758))
dominated the native limnetic fish community, but has been displaced from the pelagic habitat
due to competitive interactions with vendace (Amundsen et al., 1999; Bøhn & Amundsen,
2001, Bøhn et al., 2008). The vendace thus represents a new and highly efficient predator of
the native crustacean plankton. The trends in the zooplankton community following the

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References
More filters
Journal ArticleDOI
01 Sep 1995-Ecology
TL;DR: The results of this study suggest that environments with changing predator selectivities favor the evolution of inducible defenses, and the often assumed high physiological costs resulting from the formation or maintenance of the defenses are not necessary to explain the evolution.
Abstract: This study was designed to measure and separate the physiological costs of inducible defenses from life history trade—offs and maternal effects in the waterflea Daphnia pulex. Juveniles of D. pulex produce morphological changes ("neckteeth") and undergo life history shifts as defenses against predatory Chaoborus (phantom midge) larvae. These traits are induced by a chemical cue (kairomone) released by the predator. I performed life history experiments with and without Chaoborus kairomones at different food levels to quantify the induced changes and their potential physiological costs. The Daphnia clone used in this study also increased its body depth in response to the predator substance. Life history shifted toward a larger body size (both length and depth) and higher fecundity, which was balanced by an increased time to reach maturity and by increased adult instar durations. Reproductive effort was higher in the typical morph in the first adult instar, indicating resource allocation shifts towards growth in the protected morph. However, even in the absence of predation the chemically induced protected morph tended to show an increased intrinsic rate of population growth (r). The longer time to reach maturity was not a direct physiological cost of neckteeth production, but a trade—off for larger body size. The life history shifts are independent of neckteeth formation. Developmental mechanisms leading to life history changes occurred after neckteeth were induced and could thus be uncoupled from neckteeth formation and its direct costs. In this study no direct costs were found. Carbon incorporation rates for the two morphs, at high and low food, were not different. As a maternal effect, the large females of the induced morph produced larger neonates which, in turn, matured at a larger size. Morphological changes, life history shifts, and maternal effects acted in concert to form defenses against Chaoborus. This study shows that the often assumed high physiological costs resulting from the formation or maintenance of the defenses are not necessary to explain the evolution of inducible defenses. As morphological changes increase the visibility of Daphnia pulex, a fitness disadvantage can be caused by a changing predator regime (e.g., fish). The results of this study suggest that environments with changing predator selectivities favor the evolution of inducible defenses.

366 citations


"Long‐term responses of zooplankton ..." refers background in this paper

  • ...In Daphnia, maternal size strongly influences size at first reproduction: small-sized females produce small eggs hatching into small neonates, which 16 again are small when they reproduce for the first time (Ebert, 1993; Lampert, 1993; Tollrian, 1995)....

    [...]

  • ...16 again are small when they reproduce for the first time (Ebert, 1993; Lampert, 1993; Tollrian, 1995)....

    [...]

Journal ArticleDOI
TL;DR: Substantial progress has been made recently in chemically induced anti-predator defences in morphology, life history and behaviour, especially with respect to the identification of predator kairomones that are important for planktonic ciliates.
Abstract: Planktonic organisms exhibit diverse morphological, behavioural and life-history responses to the chemical presence of potential predators. Prey organisms have been found to sense such predators via predator-derived kairomones. The induced reactions are assumed to reduce predation risk and thus to be adaptive. Numerous studies have investigated various aspects of inducible defences in different crustaceans, in rotifers, planktonic ciliates and algae. As a first step, we summarise recent work on chemically induced anti-predator defences in morphology, life history and behaviour. Morphological defences have been found in a wide range of different plankton organisms and recent studies on predator-induced morphologies mainly addressed the question of costs for these changes. Life-history responses were mainly studied in cladocerans and several studies have recently addressed some novel topics, such as diapause induction and the influence of predator kairomones on hatching of resting stages. Behavioural anti-predator defences also have been found for several plankton species and are characterised by relatively fast induction times. We further identified four research directions in which substantial progress has been made recently: (I) The effects of simultaneous exposure to infochemicals from different predators and the consequences of a complex chemical environment. Some environmental contaminants, such as synthetic chemicals or heavy metals, have been found to potentially disturb natural chemical communication in aquatic predator-prey systems. (II) The influence of genetic variation on the reaction to infochemicals and its implications. Clonal differences have not only been found for the presence or absence of a certain trait but also with respect to the type of response. (III) The degree to which different types of responses to a specific kairomone are coupled. Recent studies underline the uncoupling of different anti-predator responses of which some have been considered to be coupled. (IV) Studies on the chemical properties and on the metabolic origin of predator kairomones. Substantial progress has been made recently, especially with respect to the identification of predator kairomones that are important for planktonic ciliates. The identification and isolation of kairomones are an important step towards studies addressing the consequences of predator-induced defences on the level of populations, communities and ecosystems. So far most studies have considered effects and consequences on the level of individual prey organisms and studies taking the consequences at higher ecological levels into account are rare.

351 citations


"Long‐term responses of zooplankton ..." refers background in this paper

  • ...Cues associated with predation risk from fish are known to anticipate the onset of reproduction in order to increase the chance of reproducing successfully before being eaten (Taylor & Gabriel, 1992; Larsson & Dodson, 1993; Lass & Spaak, 2003)....

    [...]

  • ...Reduced size at maturity is an effective way to cope with increased predation pressure from planktivorous fish, allowing individuals to start reproducing before they are exposed to strong size-selective predation (Taylor & Gabriel, 1992; Larsson & Dodson, 1993; Lass & Spaak, 2003)....

    [...]

01 Jan 1995
TL;DR: In this article, the authors measured and separated the physiological costs of inducible defenses from life history trade-offs and maternal effects in the waterflea D(aphnitl /)ulex.
Abstract: This study was designed to measure and separate the physiological costs of inducible defenses from life history trade-offs and maternal effects in the waterflea D(aphnitl /)ulex. Juveniles of D. pulex produce morphological changes ("neckteeth") and undergo life history shifts as defenses against predatory Ch(uoborus (phantom midge) larvae. These traits are induced by a chemical cue (kairomone) released by the predator. I performed life history experiments with and without Chuioboruis kairomones at different food levels to quantify the induced changes and their potential physiological costs. The Dalphni(u clone used in this study also increased its body depth in response to the predator substance. Life history shifted toward a larger body size (both length and depth) and higher fecundity, which was balanced by an increased time to reach maturity and by increased adult instar durations. Reproductive effort was higher in the typical morph in the first adult instar, indicating resource allocation shifts towards growth in the protected morph. However, even in the absence of predation the chemically induced protected morph tended to show an increased intrinsic rate of population growth (r-). The longer time to reach maturity was not a direct physiological cost of neckteeth production, but a trade-off for larger body size. The life history shifts are independent of neckteeth formation. Developmental mechanisms leading to life history changes occurred after neckteeth were induced and could thus be uncoupled from neckteeth formation and its direct costs. In this study no direct costs were found. Carbon incorporation rates for the two morphs, at high and low food, were not different. As a maternal effect, the larger females of the induced morph produced larger neonates which, in turn, matured at a larger size. Morphological changes, life history shifts, and maternal effects acted in concert to form defenses against Chaioboruts. This study shows that the often assumed high physiological costs resulting from the formation or maintenance of the defenses are not necessary to explain the evolution of inducible defenses. As morphological changes increase the visibility of Daiphnlai pule-V, a fitness disadvantage can be caused by a changing predator regime (e.g., fish). The results of this study suggest that environments with changing predator selectivities favor the evo- lution of inducible defenses.

348 citations

Journal ArticleDOI
01 May 2003-Ecology
TL;DR: In this article, the authors review and synthesize the theoretical literature on TMIs and, in particular, on trait-mediated indirect interactions, in which the presence of one species mediates the interaction between a second and third species.
Abstract: Trait-mediated interactions (TMIs), in which trophic and competitive inter- actions depend on individual traits as well as on overall population densities, have inspired large amounts of research, but theoretical and empirical studies have not been well con- nected. To help mitigate this problem, we review and synthesize the theoretical literature on TMIs and, in particular, on trait-mediated indirect interactions, TMIIs, in which the presence of one species mediates the interaction between a second and third species. (1) In models, TMIs tend to stabilize simple communities; adding further biological detail often reduces stability in models, but populations may persist even if their dynamics become mathematically unstable. (2) Short- and long-term changes in population density caused by TMIs depend even more on details, such as the curvature of functional responses and trade-offs, which have rarely been measured. (3) The effects of TMIs in multipredator communities depend in a straightforward way on the specificity of prey defenses. (4) Tritrophic and more complex communities are theoretically difficult; few general conclu- sions have emerged. Theory needs new kinds of experiments as a guide. The most critical needs are experiments that measure curvatures of trade-offs and responses, and experiments that (combined with theory) allow us to scale from short- to long-term responses of com- munities. Anecdotal evidence from long-term and large-scale studies suggests that TMIs may affect community dynamics at practical management scales; community models in- corporating TMIs are necessary and require closer collaborations between theory and ex-

345 citations


"Long‐term responses of zooplankton ..." refers background in this paper

  • ...In addition to the numerical, direct effects of predation, prey populations may be affected by invasive predators via trait-mediated interactions (Bolker et al., 2003)....

    [...]

Journal ArticleDOI
TL;DR: The size of the zooplankton consumed by rainbow trout and yellow perch was studied in two Michigan lakes and compared with the size ofThe limnetic zoop lankton was compared with plankton in the stomachs of fish taken at the same time.
Abstract: The size of the zooplankton consumed by rainbow trout and yellow perch was studied in two Michigan lakes and compared with the size of the limnetic zooplankton. One of the study lakes was managed for both rainbow trout and warmwater game fish (a “combination” lake), and the other was managed solely for rainbow trout after it was reclaimed with toxaphene. Plankton samples were collected in the summer both before and after the introduction of rainbow trout, and compared with plankton in the stomachs of fish taken at the same time. Daphnids were the only zooplankton consumed by rainbow trout in both lakes and by yellow perch in the combination lake even though there were many other genera of zooplankters. Both species were very size selective and usually consumed only Daphnia over 1.3 mm in size while ignoring the many and often more numerous smaller zooplankton. Despite the broad range in size of these trout (7.9 to 17.2 inches) and yellow perch (2.8 to 9.8 inches), there was no strong evidence of ...

325 citations

Frequently Asked Questions (1)
Q1. What are the contributions in "Long-term responses of zooplankton to invasion by a planktivorous fish in a subarctic watercourse" ?

Strayer et al. this paper studied the long-term effects of predation on the planktonic prey community over a 12-yr period during the establishment of a specialised zooplanktivore.