A comparison of the vertical zonation of diatom, foraminifera, and macrophyte assemblages in a coastal marsh: implications for greater paleo-sea level resolution

Researchers generally use only one type of plant or animal to study a parti cular marsh. Consequently, it has been impossible to directly compare zonat ions obtained using different groups between sites. To facilitate such comp arison, cluster analysis of foraminiferal, diatom, and macrophyte data coll ected in transects from a tidal marsh at Zeballos, northwestern Vancouver I sland, British Columbia, was carried out. These analyses yielded three, six , and four mostly elevation-controlled assemblage zones, respectively. Phys ical parameters such as salinity and oxygen concentration affect the: vario us taxa differently, resulting in significantly different assemblage bounda ries between groups. A composite analysis of all groups yielded an assembla ge zonation very similar to that obtained with the macrophytes alone. Altho ugh fewer assemblage zones were resolved with the composite analysis than w ith the diatom data alone, fewer sample misclassifications resulted in more precise elevation determinations. A second composite analysis using only f oraminiferal and diatom data, which is more useful to paleo-sea level resea rchers, also gave four elevation controlled assemblage zones, although asse mblage zone elevational boundaries differed slightly from those obtained wi th data from all groups. Our results will permit researchers working on dia toms, foraminifera or macrophytes to calibrate their zonations thus making it easier for workers in different fields to compare their results.