Spatio-temporal variability of macrozoobenthos size structure of a coastal lagoon: the influence of spectrum resolution

Abstract

1 - The influence of spectrum resolution on the detection of spatio-temporal variability in macrozoobenthos size structure was investigated in a coastal lagoon located in southern Italy (Le Cesine, Puglia). 2 - In fall 2004 and spring 2005, the individual dry mass of benthic macroinvertebrates collected in box-corer samples was determined at six experimental sites. Individual data were allocated to size class scales with logarithmic bases ranging from ×1.2 to ×3.0 with a 0.1 increment; spectra with a decreasing degree of resolution were produced and tested for the effects of the two orthogonal factors “season” and “site”. 3 - Significant interaction effects between the two factors were observed independently from the scale used to produce the size spectrum. Subsequent post-hoc comparisons showed no predictable, scale-dependent patterns either in fall or in spring; nonetheless, in the two seasons the minimum and maximum number of significant inter-site post-hoc comparisons were respectively observed for an octave class (×2) spectrum. 4 - Our results indicate that evaluating the influence of scale-dependent effects on size spectra might be helpful for increasing the consistency of size-related approaches to the analysis and monitoring of macrozoobenthic assemblages.