1-meter composite digital sidescan sonar mosaic of National Oceanic and Atmospheric Administration (NOAA) survey H11043 in north-central Long Island Sound off Branford, Connecticut (H11043_GEO_WGS84.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 (Poppe and Polloni, 1998; fig. 1). The mosaic presented herein covers a 41.1 km2 of the sea floor in north-central Long Island Sound off Branford, Connecticut. 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，针对美国东海岸核心河口、毗邻全美人口最密集区域的长岛海湾（Long Island Sound），编制了详细的海底地质图。本系列研究基于1982年启动的康涅狄格州合作研究项目开展。当前研究阶段聚焦于海底沉积物分布、调控沉积物分布的动力过程、近岸环境相关问题，以及底栖生物群落结构（benthic community structures）与海底地质的关联。 人类活动产生的废弃物、有毒化学品，以及住宅、商业与休闲开发引发的土地利用模式改变，均对海湾环境造成了显著压力，导致底栖栖息地（benthic habitats）退化甚至潜在丧失（Koppelman等，1976；长岛海湾研究，1994）。当前亟需高精度海底地图，以评估不利影响的波及范围，并为未来资源的科学管理提供支撑。为此，为持续深化对长岛海湾的认知，我们针对特定重点区域构建并解译了侧扫声呐镶嵌图（sidescan sonar mosaics，即全覆盖海底声学影像）（Poppe与Polloni，1998；图1）。本次展示的镶嵌图覆盖了康涅狄格州布兰福德附近、长岛海湾中北部的41.1平方千米海底区域。 该声呐镶嵌图及其解译成果可服务于多重目标：其一，明确海底地质变异性——这是调控底栖生境多样性的核心控制因素之一；其二，深化对调控海底沉积物分布与运移、底栖生境及相关内生群落结构分布的动力过程的理解；其三，为未来的研究、监测与管理活动提供精细的研究框架。此外，侧扫声呐镶嵌图还可作为后续沉积学（sedimentological）、地球化学与生物学观测的底图，因为环境背景的精确信息对于采样点位选择和单点测量结果的准确解译至关重要。