A New Coverage Range Index for Assessing Impact of Substrate Composition on Distribution of Hard Bottom Macrobenthos

This study evaluated the impact of substrate composition on macrobenthos distribution using a new Coverage Range Index (CRI), and diversity index variables and macrobenthos data sets obtained over a period of 12 months, between June 2015 and June 2016, along 6 sampling transects at 2 sites. The selected transects were all situated in littoral zone of Hormuz Island in the Persian Gulf and had hard bottom type with different substrate compositions. Accordingly, macrobenthos samples at each site were taken from 3 hard bottom types: boulder, cobble, and pebble. CRI and diversity indices (Simpson, Shannon-Wiener, Pielou, Brillouin, Menhinick, Margalef and Berger-Parker) were employed to evaluate the abundance of macrobenthos. CRI was also selected to tentatively assign the investigated abundance range of macrobenthos into 3 coverage range categories: wide, middle, narrow. CRI boundary of the categories was estimated. The analyses of CRI and diversity indices revealed a similar clustering between the sampling transects. These findings indicate that CRI is a simpler indicator in assessing abundance of macrobenthos than diversity indices, because CRI is only based on species abundance, but diversity indices are based on both species number and abundance. Hence, CRI proved to be a universal ecological index due to its different ranges of small to large samples, rare species to dominant ones, and individual specimens to polyps of animal colonies. Future study should focus on extending the database to test CRI in other bottom types. Finally, the results from this study may be useful not only for developing countries but also for any organization struggling to use macrobenthos based indices with restricted financial resources and knowledge.