Only alpha is considered in the construction of the hypothesis test.

According to Connell�s intermediate disturbance hypothesis (IDH), diversity within a community is maximal at intermediate frequencies and intensities of disturbances. In order to test the IDH, disturbances of different frequencies and intensities were imposed on natural plankton communities in controlled field experiments. These disturbances consisted of an artificial deepening of the mixed layer, leading to the dilution of epilimnetic populations and to a higher level of nutrients. Intervals between disturbances ranged from 2 to 12 d. Different intensities of disturbance were caused by differences in the experimental mixing depth (150 and 225% of the original epilimnion depth). Investigation focused on the effect that disturbances had on the diversity of natural phytoplankton communities. Additionally, we were interested in determining the effect of grazing by zooplankton. The results of the field experiments show for the first time the applicability of the IDH to phytoplankton within complete planktonic communities. Diversity showed a clear maximum at the intermediate disturbance interval of 6 d. Similarly, species number peaked at intermediate interval length (6-10 d).

This effect is related to the type I error of a hypothesis test.

Wilkinson, D.M. (1999) The disturbing history of intermediate disturbance. Oikos, 84, 145-147.

Intermediate disturbance hypothesis - Wikipedia

For example, chloroform in exhaled breath has been used as a biological marker to evaluate dermal exposure while swimming and showering (Levesque et al., 1994).

Graph shows principles of intermediate disturbance hypothesis: ..

Mobilization of contaminants from internal storage can be assessed using biological markers; for example, pesticide mobilization from adipose tissue can be measured in blood following fasting.


explore the third aspect of Connell’s hypothesis ..

For example, knowledge of the presence of pesticides in breast milk may lead an individual to avoid breast-feeding without consideration of its advantages (Vandenberg, 1991; Sim & McNeil, 1992).

Test of the Intermediate Disturbance.

Knowledge of previous exposure or genetic predisposition may have adverse implications for an individual; for example, individuals may be denied health insurance on the basis of presumed future risk.

Intermediate Disturbance Hypothesis in Phytoplankton Ecology

ASSESSING EXPOSURES WITH BIOLOGICAL MARKERS 10.1 Introduction This chapter presents a summary of the major concepts, definitions, advantages, limitations, sampling, media and uses of biological markers as applied for exposure assessment to environmental contaminants.

Intermediate Disturbance Hypothesis in ..

Overview of sampling techniques for airborne pollen grainsa Method Examples Sampling rate and time Remarks Rotating tape/slide impactors Burkard trap 10 litre/min, 7 days cut-off 2.5 or 5.2 µm, depending on slot Lanzoni sampler 10 litre/min, 7 days cut-off 10 µm Moving slide impactors Allergenco air sampler 15 litre/min, intermittent cut-off 2.0 µm Stationary slide impactors Burkard portable sampler 10 litre/min, 1-9 min cut-off 5.2 µm Rotating arm impactors Rotorod sampler 47 litre/min, intermittent cut-off unknown a for detailed information see ACGIH (1995).

17/07/2014 · Connell 1979 intermediate disturbance ..

Biological markers may also indicate the presence of additional exposures; for example, biological markers used in occupational settings have been applied to determine if non-occupational exposures to similar agents are occurring (Lauwerys, 1983).

The intermediate disturbance hypothesis should be ..

For example, blood concentration data for a number of pesticides and metals were collected in a representative sample of the US population in the National Health and Nutrition Evaluation Survey (NHANES IV) and the German Environmental Survey (Krause et al., 1992).

Intermediate Disturbance Hypothesis - WikiVisually

For example, in occupational settings, biological monitoring has no advantages over environmental monitoring for airborne chemicals with biological half-lives less than 10 h, since the integration time for the marker is too short to allow accurate representation of exposure (Droz, 1993).