Predator effects on prey density 1 Title : Evaluating consumptive and nonconsumptive predator effects on prey density using 2 field times series data 3 4 (original) (raw)
Related papers
Large Nonlethal Effects of an Invasive Invertebrate Predator on Zooplankton Population Growth Rate
Ecology, 2007
We conducted a study to determine the contribution of lethal and nonlethal effects to a predator's net effect on a prey's population growth rate in a natural setting. We focused on the effects of an invasive invertebrate predator, Bythotrephes longimanus, on zooplankton prey populations in Lakes Michigan and Erie. Field data taken at multiple dates and locations in both systems indicated that the prey species Daphnia mendotae, Daphnia retrocurva, and Bosmina longirostris inhabited deeper portions of the water column as Bythotrephes biomass increased, possibly as an avoidance response to predation. This induced migration reduces predation risk but also can reduce birth rate due to exposure to cooler temperatures. We estimated the nonlethal (i.e., resulting from reduced birth rate) and lethal (i.e., consumptive) effects of Bythotrephes on D. mendotae and Bosmina longirostris. These estimates used diel field survey data of the vertical gradient of zooplankton prey density, Bythotrephes density, light intensity, and temperature with growth and predation rate models derived from laboratory studies. Results indicate that nonlethal effects played a substantial role in the net effect of Bythotrephes on several prey population growth rates in the field, with nonlethal effects on the same order of magnitude as or greater (up to 10-fold) than lethal effects. Our results further indicate that invasive species can have strong nonlethal, behaviorally based effects, despite short evolutionary coexistence with prey species.
Journal of Marine Systems
The effect of multiple stressors on marine ecosystems remains poorly understood and most of the knowledge available is related to phytoplankton. To partly address this knowledge gap, we tested if combining multimodel inference with generalized additive modelling could quantify the relative contribution of environmental variables on the population dynamics of a zooplankton species in the Belgian part of the North Sea. Hence, we have quantified the relative contribution of oceanographic variables (e.g. water temperature, salinity, nutrient concentrations, and chlorophyll a concentrations) and anthropogenic chemicals (i.e. polychlorinated biphenyls) to the density of Acartia clausi. We found that models with water temperature and chlorophyll a concentration explained ca. 73% of the population density of the marine copepod. Multimodel inference in combination with regression-based models are a generic way to disentangle and quantify multiple stressor-induced changes in marine ecosystems. Future-oriented simulations of copepod densities suggested increased copepod densities under predicted environmental changes.
ICES Journal of Marine Science, 2014
Plourde, S., and Browman, H. I. 2014. Parameterizing and operationalizing zooplankton population dynamic and trophic interaction models. – ICES Journal of Marine Science, 71: 234–235. This themed set (TS) of articles was motivated by the need for modellers and biologists–ecologists to work more closely together to produce more realistic simulation models of zooplankton population dynamics and trophic interactions. The TS was intended to cover a broad range of subjects and potential approaches, including identifying crucial gaps in our knowledge and parameterization of biological/physiological processes, experimental/fieldwork aimed at quantifying the response of key physiological and behavioural processes to variations in the environment, identifying novel modelling approaches that would enable the development of simulation models that would minimize the need for species-specific (and stage-specific) model parameterization, etc. Five articles were accepted for inclusion in the TS. T...
Journal of Great Lakes Research, 2012
We examined seasonal dynamics of zooplankton at an offshore station in Lake Michigan from 1994Michigan from to 2003Michigan from and 2007Michigan from to 2008. This period saw variable weather, declines in planktivorous fish abundance, the introduction and expansion of dreissenid mussels, and a slow decline in total phosphorus concentrations. After the major expansion of mussels into deep water (2007)(2008), chlorophyll in spring declined sharply, Secchi depth increased markedly in all seasons, and planktivorous fish biomass declined to record-low levels. Overlaying these dramatic ecosystem-level changes, the zooplankton community exhibited complex seasonal dynamics between 1994-2003 and 2007-2008. Phenology of the zooplankton maximum was affected by onset of thermal stratification, but there was no other discernable effect due to temperature. Interannual variability in zooplankton biomass during 1994 and 2003 was strongly driven by planktivorous fish abundance, particularly age-0 and age-1 alewives. In 2007-2008, there were large decreases in Diacyclops thomasi and Daphnia mendotae possibly caused by food limitation as well as increased predation and indirect negative effects from increases in Bythotrephes longimanus abundance and in foraging efficiency associated with increased light penetration. The Bythotrephes increase was likely driven in part by decreased predation from yearling and older alewife. While there was a major decrease in epilimnetic-metalimnetic herbivorous cladocerans in 2007-2008, there was an increase in large omnivorous and predacious calanoid copepods, especially those in the hypolimnion. Thus, changes to the zooplankton community are the result of cascading, synergistic interactions, including a shift from vertebrate to invertebrate planktivory and mussel ecosystem impacts on light climate and chlorophyll.
Ecological Modelling, 2009
We have developed a dynamic model to track the evolution of contaminant concentration in an aquatic organism as a function of season and ontogeny throughout its life cycle. We have focused our analysis on the round goby (Apollonia melanostoma), a globally distributed invasive forage fish. By integrating bioenergetics with a bioaccumulation model, we illustrate how life history characteristics interact to influence contaminant accumulation. We use uncertainty and sensitivity analyses to assess how the model output is affected by uncertainty and variability in model parameters. We then demonstrate the influence of important physiological characteristics on contaminant accumulation with two scenarios. First, we probe the influence of sexual dimorphism by comparing gender-specific accumulation of a standard polychlorinated biphenyl congener, PCB153, in male and female round gobies. We hypothesize that lipid loss in female gobies during spawning season leads to a decrease in the PCB body burden compared to male gobies. Second, we compare PCB accumulation in the round goby and in the mottled sculpin (Cottus bairdi), the native forage fish that the round goby displaced in southern Lake Michigan, to determine whether the invasive species has an intrinsically different bioaccumulation potential than the native one. Our non-intuitive findings from these simulations illustrate how the interaction of growth rate with other life history characteristics lead to unexpected bioaccumulation patterns. The model we present is a flexible tool that integrates complex and dynamic interactions among environmental parameters, thus providing a means to better assess the potential for chemical accumulation in human and wildlife populations, and aiding the development of ecological forecasts.
Marine Ecology Progress Series, 2014
Increasing pressure on animal populations through climate change and anthropogenic exploitation fuel the need to understand complex life cycle dynamics of key ecosystem species and their responses to external factors. Here, we provide a novel, integrative study on the long-term population dynamics of Pseudocalanus acuspes, a key species in the Baltic Sea, explicitly considering its distinct life-history stages, and testing for linear, non-linear, and non-additive climate and food web effects. Based on a unique data set of stage-specific abundance covering almost 5 decades of sampling (1960 to 2008, with 1408 samples), we use generalized additive modeling (GAM) and its respective non-additive threshold (TGAM) formulation to test for (1) density effects on subsequent life-history stages within the internal life cycle, (2) the effect of exogenous bottom-up (i.e. hydro-climatic) and top-down (i.e. predation) pressures, and (3) changes between bottom-up and top-down regulation. We show that linear density effects are always present, explaining a high proportion of interannual variability, while effects of external pressures are nonlinear or non-additive and strongly stage-and season-specific. In general, younger stages of P. acuspes are more affected by atmospheric winter conditions and water temperature, whereas older stages are influenced by conditions of deepwater salinity and predation pressure. These bottom-up processes, however, are not necessarily stable, and can depend on the level of top-down predation pressure. Our study demonstrates the complex and non-stationary interplay between internal and external factors regulating long-term animal population dynamics.
ICES Journal of Marine Science, 2017
Several approaches have been developed over the last decade to simultaneously estimate distribution or density for multiple species (e.g. “joint species distribution” or “multispecies occupancy” models). However, there has been little research comparing estimates of abundance trends or distribution shifts from these multispecies models with similar single-species estimates. We seek to determine whether a model including correlations among species (and particularly species that may affect habitat quality, termed “biogenic habitat”) improves predictive performance or decreases standard errors for estimates of total biomass and distribution shift relative to similar single-species models. To accomplish this objective, we apply a vector-autoregressive spatio-temporal (VAST) model that simultaneously estimates spatio-temporal variation in density for multiple species, and present an application of this model using data for eight US Pacific Coast rockfishes (Sebastes spp.), thornyheads (S...
Fisheries Oceanography, 2001
The goal of this study is to determine if an individualbased size-dependent model can realistically simulate changes in the length±frequency distributions of several species of ®sh larvae collected in Conception Bay in 1993 and 1994, using ®eld estimations of growth and predator abundance. We ®rst model the length± frequency distribution of ®eld samples with the best possible estimates of mean growth rate. Then, we add predation mortality given the characteristics of the predator community observed during our surveys, which was composed of macrozooplankton and adult capelin. The larval ®sh community is generally not affected by predation by macrozooplankton, as the average instantaneous mortality rate predicted by the model was 0.004 day ±1. Fish larvae appear to be more vulnerable to predation by the population of adult capelin. We estimate that an abundance of adult capelin ranging between 0.2 and 1.0 individuals per 1000 m ±3 may have a substantial impact on the larval ®sh community. The predictions of an individualbased model are directly related to the accuracy of estimates of the mean growth rates of the larval ®sh cohorts. We ®nd that it is dif®cult to differentiate sizeselective removal of individuals from random selection by analysing changes of the length±frequency distributions of the larval ®sh community.
Biological Invasions, 2010
Understanding population dynamics and population regulation of invasive species is critical for predicting their effects on native ecosystems as well as for control strategies. Many species of gastropod in the genus Pomacea are successful aquatic invaders that have caused economic and ecological impacts in Southeastern Asia where their large fecundity and broad reproductive window helps them to colonize and take advantages of ephemeral agricultural habitats. We followed the population dynamics of P. insularum in permanent, stable freshwater systems (ponds and streams), and in ephemeral agricultural habitats in the upper Texas Gulf Coast region, USA. We found that although P. insularum has a large reproductive potential, its density, biomass and size structure in stable permanent systems did not change significantly from March to November, and densities averaged \2 m -2 . This same species, however, displayed very different population dynamics in ephemeral agricultural environments. We found high densities ([130 m -2 ), and no stable size structure through time. Differences in the stability and persistence of these two types of environments appear to drive these patterns. Stability and persistence of habitats can result in different predator communities and the risk of predation for snails. We suggest that such factors may cause the differences in population dynamics and structure observed. The ability of snails to escape population control and explode in ephemeral habitats could drive the types of impacts seen on agricultural crops.