1-meter Composite Mosaic of the Sidescan Sonar Survey National Oceanic and Atmospheric Administration (NOAA) H11045 in west-central Long Island Sound off Bridgeport, Connecticut in Geographic (H11045_GEO1M_WGS84_INV.TIF)

The U.S. Geological Survey, in cooperation with the National Oceanic and Atmospheric Administration and the Connecticut Department of Environmental Protection, has produced detailed geologic maps of the sea floor in Long Island Sound, a major East Coast estuary surrounded by the most densely populated region of the United States. These studies have built upon cooperative research with the State of Connecticut that was initiated in 1982. The current phase of this research program is directed toward studies of sea-floor sediment distribution, processes that control sediment distribution, nearshore environmental concerns, and the relation of benthic community structures to the sea-floor geology. Anthropogenic wastes, toxic chemicals, and changes in land-use patterns resulting from residential, commercial, and recreational development have stressed the environment of the Sound, causing degradation and potential loss of benthic habitats (Koppelman and others, 1976; Long Island Sound Study, 1994). Detailed maps of the sea floor are needed to help evaluate the extent of adverse impacts and to help manage resources wisely in the future. Therefore, in a continuing effort to better understand Long Island Sound, we have constructed and interpreted sidescan sonar mosaics (complete-coverage acoustic images of the sea floor) within specific areas of special interest. The mosaic presented herein covers a 190.3 km square area of the sea floor in the West-Central Basin of Long Island Sound. The mosaics and their interpretations serve many purposes, including: (1) defining the geological variability of the sea floor, which is one of the primary controls of benthic habitat diversity; (2) improving our understanding of the processes that control the distribution and transport of bottom sediments and the distribution of benthic habitats and associated infaunal community structures; and (3) providing a detailed framework for future research, monitoring, and management activities. The sidescan sonar mosaics also serve as base maps for subsequent sedimentological, geochemical, and biological observations, because precise information on environmental setting is important for selection of sampling sites and for accurate interpretation of point measurements.美国地质调查局（U.S. Geological Survey）与美国国家海洋和大气管理局（National Oceanic and Atmospheric Administration）、康涅狄格州环境保护部（Connecticut Department of Environmental Protection）合作，针对美国东海岸人口最稠密区域环绕的重要河口湾——长岛海湾（Long Island Sound）的海底，编制了高精度地质图。该项研究的基础为1982年启动的康涅狄格州合作研究项目。本研究计划的当前阶段，聚焦于海底沉积物分布、调控沉积物分布的过程、近岸环境关切问题，以及底栖生物群落结构与海底地质的关联。 人为废弃物、有毒化学物质，以及住宅、商业和休闲开发引发的土地利用模式变化，已对该海湾的生态环境造成胁迫，引发底栖生境退化乃至潜在丧失（Koppelman等，1976；长岛海湾研究，1994）。高精度海底图件对于评估不利影响的波及范围、指导未来资源的科学管理均具有重要意义。因此，为持续深化对长岛海湾的认知，研究团队针对特定重点区域，构建并解译了侧扫声呐镶嵌图（sidescan sonar mosaics，即海底全覆盖声学影像）。本次发布的镶嵌图覆盖了长岛海湾中西部海盆190.3平方千米的海底区域。 该镶嵌图及其解译成果具备多重应用价值：(1) 刻画海底地质变异性——该因素是调控底栖生境多样性的核心控制因子之一；(2) 深化对调控海底沉积物分布与输运、底栖生境分布及相关底内生物群落结构的过程机制的认知；(3) 为后续的研究、监测与管理活动提供精细化的研究框架。此外，侧扫声呐镶嵌图还可作为后续沉积学、地球化学及生物学观测的基础底图，因为环境背景的精确信息对于采样点位遴选与单点测量结果的准确解译均具有关键作用。