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Titolo:
DETECTION OF ENVIRONMENTAL IMPACTS - NATURAL VARIABILITY, EFFECT SIZE, AND POWER ANALYSIS
Autore:
OSENBERG CW; SCHMITT RJ; HOLBROOK SJ; ABUSABA KE; FLEGAL AR;
Indirizzi:
UNIV CALIF BERKELEY,DEPT INTEGRAT BIOL BERKELEY CA 94720 UNIV CALIF SANTA BARBARA,INST MARINE SCI,COASTAL RES CTR SANTA BARBARA CA 93106 UNIV CALIF SANTA BARBARA,DEPT BIOL SCI SANTA BARBARA CA 93106 UNIV CALIF SANTA CRUZ,INST MARINE SCI SANTA CRUZ CA 95064
Titolo Testata:
Ecological applications
fascicolo: 1, volume: 4, anno: 1994,
pagine: 16 - 30
SICI:
1051-0761(1994)4:1<16:DOEI-N>2.0.ZU;2-S
Fonte:
ISI
Lingua:
ENG
Soggetto:
STATISTICAL POWER; DESIGN; POPULATIONS; SETTLEMENT; MORTALITY; PATTERNS; CONSEQUENCES; COMMUNITIES; RECRUITMENT; ENRICHMENT;
Keywords:
BEFORE-AFTER-CONTROL-IMPACT DESIGN; ENVIRONMENTAL IMPACT; ENVIRONMENTAL MONITORING; IMPACT ASSESSMENT; INDIVIDUAL VS POPULATION PARAMETERS; POLLUTION; PRODUCED WATER; SERIAL CORRELATION; SPATIAL VARIABILITY; STATISTICAL POWER; TEMPORAL VARIABILITY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
62
Recensione:
Indirizzi per estratti:
Citazione:
C.W. Osenberg et al., "DETECTION OF ENVIRONMENTAL IMPACTS - NATURAL VARIABILITY, EFFECT SIZE, AND POWER ANALYSIS", Ecological applications, 4(1), 1994, pp. 16-30

Abstract

The power of any test of an environmental impact is simultaneously constrained by (1) the variability of the data, (2) the magnitude of theputative impact, and (3) the number of independent sampling events. In the context of the Before-After-Control-Impact design with Paired sampling (BACIP), the variability of interest is the temporal variation in the estimated differences in a parameter (e.g., population density)between two unperturbed sites. The challenges in designing a BACIP study are to choose appropriate parameters to measure and to determine the adequate number and timing of sampling events. Two types of studiesthat are commonly conducted can provide useful information in designing a BACIP study. These are (1) long-term studies that provide estimates of the natural temporal and spatial variability of environmental parameters and (2) spatial surveys around already-perturbed areas (''After-only'' studies) that can suggest the magnitude of impacts. Here we use data from a long-term study and an After-only study to illustrate their potential contributions to the design of BACIP studies. The long-term study of parameters sampled at two undisturbed sites yielded estimates of natural temporal variability. Between site differences in chemical-physical parameters (e.g., elemental concentration) and in individual-based biological parameters (e.g., body size) were quite consistent through time, while differences in population-based parameters (e.g., density) were more variable. Serial correlation in the time series of differences was relatively small and did not appear to vary amongthe parameter groups. The After-only study yielded estimates of the magnitude of impacts through comparison of sites near and distant from a point-source discharge. The estimated magnitude of effects was greatest for population-based parameters and least for chemical-physical parameters, which tended to balance the statistical power associated with these two parameter groups. Individual-based parameters were intermediate in estimates of effect size. Thus, the ratio of effect size to variability was greatest for individual-based parameters and least for population and chemical-physical parameters. The results suggest that relatively few of the population and chemical-physical parameters could provide adequate power given the time constraints of most studies. This indicates that greater emphasis on individual-based parameters is needed in field assessments of environmental impacts. It will be critical to develop and test predictive models that link these impacts witheffects on populations.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 24/09/20 alle ore 21:00:42