An approach to analyzing influence of enumeration time periods on detecting ecological features of microperiphyton communities for marine bioassessment

Ecological features of microperiphytons have widely been used as robust indicators for marine bioassessment. The influence of enumeration time periods on analyzing ecological patterns and biodiversity measures of microperiphyton communities was studied using a range of statistical methods in coastal waters of the Yellow Sea, northern China, during the period of May–June, 2010. Samples were collected at depths of 1 and 3 m using an artificial substratum, and were analyzed with different enumeration time periods. Enumeration time periods represented a strong influence on analyzing ecological features of microperiphyton communities, although no significant changes occurred in microperiphyton community structures between two enumeration schemes (within 24 h and 24–48 h) at both water depths. The delayed enumeration (within 24–48 h) may result in the similarity of the communities being reduced 5–25%, and in the biodiversity (richness, evenness, and diversity of species) indices decreasing with shortening community ages. The standard errors due to the delayed enumeration were >10% for analyzing species richness and abundance until the communities ages reached 21 days or more. These results suggest that the enumeration should be completed as soon as possible within 24 h after sampling to analyze ecological features of microperiphyton communities for monitoring programs and ecological conservation researches in marine ecosystems.