Habitat change in estuaries: predicting broad-scale responses of intertidal macrofauna to sediment mud content. Technical Report
- Author
- Thrush, S.F., Hewitt, J.E., Norkko, A., Nicholls, P.E., Funnell, G.A., Ellis, J.I.
- Year
- 2003
- Journal / Source
- Marine Ecology Progress Series
- Volume
- 263
- Month
- November
- Pages
- 101-112
- Keywords
- Habitat change, Macrofauna, Sediment grain size, Logistic regression, factor ceiling responses, Transition zones,
- Summary
- This paper details a novel strategy developed to enable rapid data collection of macrofaunal densities and sediment characteristics by sampling mud-to-sand transition zones in 19 estuaries for use in species-specific models to investigate the effects of habitat change. THREATS IDENTIFIED AND/OR DESCRIBED Sediment changes SCOPE OF SPECIES, HABITATS AND ECOSYSTEMS IMPACTED: Intertidal macrofauna SPATIAL EXTENT OF THREAT STUDIED: Coastal sites throughout North Island TEMPORAL EXTENT OF THREAT STUDIED: 2000 DATASETS USED IN THE ANALYSES: Macrofauna abundance and sediment characteristics METHODOLOGY USED TO IDENTIFY AND DETERMINE SEVERITY OF THREAT: Species-specific models that predict probability of occurrence relative to sediment mud content were developed for 13 common macrofaunal species. The following were modelled: distribution of maximum density along the gradient from mud to sand; maximum and minimum values for number of taxa; number of individuals; Shannon-Wiener diversity; and taxonomic distinctness. KEY FINDINGS OF THE ANALYSIS: For most variables, good models (r2 > 0.6) were developed. The models developed for species highlighted the potential variation in response to habitat change even for those species that are closely related species and have similar natural history characteristics. Results from probability-of-occurrence models and maximum-density models emphasised the need to consider changes in both occurrence and density when predicting likely responses of a species to changes in habita