Interpretation of the distribution of sedimentary environments of the sidescan sonar mosaic of National Oceanic and Atmospheric Administration (NOAA) survey H11043 off Branford, Connecticut

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 km square area 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合作，针对美国东海岸重要河口湾——长岛海峡的海底完成了详细地质填图工作。该海峡地处美国人口最密集区域周边。本研究依托1982年启动的康涅狄格州合作研究项目推进，当前研究阶段聚焦于海底沉积物分布、调控沉积物分布的过程、近岸环境问题，以及底栖群落结构与海底地质的关联。

人为废弃物、有毒化学品，以及住宅、商业和休闲开发导致的土地利用模式变化，已对海峡环境造成压力，引发底栖栖息地退化乃至潜在丧失（Koppelman等，1976；长岛海峡研究，1994）。当前亟需高精度海底地图，以评估负面影响的波及范围，并助力未来资源的科学管理。为此，为进一步深化对长岛海峡的认知，研究团队针对特定重点区域构建并解读了侧扫声呐镶嵌图（sidescan sonar mosaics，即全覆盖海底声学影像）（Poppe与Polloni，1998；图1）。本次公开的镶嵌图覆盖了康涅狄格州布兰福德附近、长岛海峡中北部一片41.1平方千米的海底区域。

该声呐镶嵌图及其解译成果具备多重应用价值：其一，明确海底地质异质性——这是调控底栖生境多样性的核心控制因素之一；其二，加深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过程的认知；其三，为后续研究、监测与管理活动提供精细的基础框架。此外，侧扫声呐镶嵌图还可作为后续沉积学、地球化学与生物学观测的底图，因为环境背景的精准信息对于采样点位遴选以及单点测量结果的准确解译至关重要。