INTEGRATION OF BIOTIC AND ABIOTIC DATA TO MAP BENTHIC HABITATS WITHIN BLOCK ISLAND AND RHODE ISLAND SOUNDS

Abstract

The mapping of benthic habitats presents the distribution and extent of seafloor environments, including biotic and abiotic characteristics, in a geo-spatial context. This thesis aims to improve methodologies used in the field of benthic habitat mapping and works towards establishing a standard mapping protocol to facilitate more effective communication both among scientists and resource managers in effort to further the goal of science-based decision making. This study is in response to interest in wind turbine construction within Rhode Island waters. A thorough understanding of benthic habitats is essential for making scientifically valid management decisions to minimize ecological and economical development impacts. Two major challenges facing benthic habitat mapping are: 1.) Appropriate methodology; and 2.) Producing maps that can easily and effectively convey information important to a broad range of users (e.g. scientists, management agencies, non-profit organizations, individual citizens). The first challenge is examined in Chapter 1, which investigates the effectiveness of two mapping approaches, top-down and bottom-up, for classifying and mapping offshore marine environments. Both methods incorporate acoustic data (side-scan sonar and bathymetry), along with sediment and benthic macrofauna samples. The traditional top-down mapping approach identifies biological community patterns based on geologically-defined habitat map units, whereas the bottom-up approach aims to establish units based on biological similarity and then use statistics to determine relationships with associated environmental parameters. Both methods showed statistically strong and significant abiotic-biotic relationships and produced habitat units with distinct macrofaunal assemblages. Overall, the bottom-up approach was more effective at mapping benthic habitats, producing more clearly defined macrofaunal assemblages. However, the spatial heterogeneity prevented development of full-coverage maps with the currently available number of ground-truth samples. Therefore, for the mapping needs of RI, the top-down method is recommended because it can produce full-coverage maps. Chapter 2 addresses the second challenge. Commonly, maps characterize habitats according dominant species or general community type. While useful, such maps do not always offer practical information to managers and can inadequately represent important habitat characteristics and relationships. In response, benthic habitats were classified according to biological and environmental metrics considered important to the existence of healthy, productive benthic habitats. The weighted metrics were totaled to develop an overall index of benthic habitat value. The index also provides individual metric scores, allowing habitats to be evaluated based on metrics relevant to the user. Furthermore, indices can be used to discern biotic-abiotic relationships between and among habitats and index metrics. The indices identified habitats