Northeast Fisheries Science Center J. J. Howard Laboratory, National Oceanic and Atmospheric Administration, National Marine Fisheries Service, Highlands, NJ, USA.
PLoS One. 2013;8(2):e55273. doi: 10.1371/journal.pone.0055273. Epub 2013 Feb 6.
Georges Bank is a large, shallow feature separating the Gulf of Maine from the Atlantic Ocean. Previous studies demonstrated a strong tidal-mixing front during the warm season on the northern bank margin between thermally stratified water in the Gulf of Maine and mixed water on the bank. Tides transport warm water off the bank during flood tide and cool gulf water onto the bank during ebb tide. During 10 days in August 2009, we mapped frontal temperatures in five study areas along ∼100 km of the bank margin. The seabed "frontal zone", where temperature changed with frontal movment, experienced semidiurnal temperature maxima and minima. The tidal excursion of the frontal boundary between stratified and mixed water ranged 6 to 10 km. This "frontal boundary zone" was narrower than the frontal zone. Along transects perpendicular to the bank margin, seabed temperature change at individual sites ranged from 7.0°C in the frontal zone to 0.0°C in mixed bank water. At time series in frontal zone stations, changes during tidal cycles ranged from 1.2 to 6.1°C. The greatest rate of change (-2.48°C hr(-1)) occurred at mid-ebb. Geographic plots of seabed temperature change allowed the mapping of up to 8 subareas in each study area. The magnitude of temperature change in a subarea depended on its location in the frontal zone. Frontal movement had the greatest effect on seabed temperature in the 40 to 80 m depth interval. Subareas experiencing maximum temperature change in the frontal zone were not in the frontal boundary zone, but rather several km gulfward (off-bank) of the frontal boundary zone. These results provide a new ecological framework for examining the effect of tidally-driven temperature variability on the distribution, food resources, and reproductive success of benthic invertebrate and demersal fish species living in tidal front habitats.
乔治斯浅滩是一个大型浅滩，将缅因湾与大西洋隔开。之前的研究表明，在温暖季节，在缅因湾的分层水和浅滩混合水之间的北部浅滩边缘存在强烈的潮汐混合锋。涨潮时，潮水将暖水从浅滩上带走，落潮时将凉爽的海湾水带到浅滩上。在 2009 年 8 月的 10 天里，我们在约 100 公里的浅滩边缘的五个研究区域绘制了锋面温度。海底“锋区”是温度随锋面移动而变化的区域，经历了半日潮的最高和最低温度。分层水和混合水之间的锋面边界的潮汐摆动范围为 6 至 10 公里。这个“锋面边界区”比锋区窄。在垂直于浅滩边缘的横截线上，单个站点的海底温度变化从锋区的 7.0°C 到混合浅滩水的 0.0°C 不等。在锋区站的时间序列中，潮汐周期的变化范围从 1.2°C 到 6.1°C。最大的变化率（-2.48°C/hr）发生在中落潮时。海底温度变化的地理图允许在每个研究区域中绘制多达 8 个分区。分区中温度变化的幅度取决于其在锋区的位置。锋面移动对 40 至 80 米深度间隔的海底温度影响最大。在锋区经历最大温度变化的分区不在锋面边界区，而是在锋面边界区几公里之外的海湾（浅滩之外）。这些结果为研究潮汐驱动的温度变化对生活在潮汐锋区生境中的底栖无脊椎动物和底栖鱼类的分布、食物资源和繁殖成功率的影响提供了一个新的生态框架。
