High resolution still photographs of the seafloor across the Mertz Glacier Region

Geoscience Australia and the Australian Antarctic Division conducted a benthic community survey using underwater still photographs on the shelf around the Mertz Glacier region. The purpose of the work was to collect high resolution still photographs of the seafloor across the shelf to address three main objectives:
1.
to investigate benthic community composition in the area previously covered by the Mertz Glacier tongue and to the east, an area previously covered by fast ice
2.
to investigate benthic community composition (or lack thereof) in areas of known iceberg scours
3.
to investigate the lateral extent of cold water coral communities in canyons along the shelf break.
Benthic photos were captured using a Canon EOS 20D SLR 8 megapixel stills camera fitted with a Canon EF 35mm f1.4 L USM lens in a 2500m rated flat port anodised aluminium housing. Two Canon 580EX Speedlight strobes were housed in 6000m rated stainless steel housings with hemispherical acrylic domes. The camera and strobes were powered with a 28V 2.5Ah cyclone SLA battery pack fitted in the camera housing and connected using Brantner Wetconn series underwater connectors. The results were obtained with 100 ASA and a flash compensation value of +2/3 of a stop. The focus was set manually to 7m and the image was typically exposed at f2.8 and a shutter speed of 1/60 sec. The interval between photos was set to 10 or 15 seconds.
The camera was fitted to either the CTD frame or the beam trawl frame and lowered to approximately 4-5 m from the bottom. Two laser pointers, set 50 cm apart, were used for scale. The camera was deployed at 93 stations, 7 using the beam trawl frame and 86 using the CTD frame.
The stations were named by:
1.
Camera deployment frame (e.g. CTD or beam trawl, BT)
2.
Frame sequence number (e.g. CTD53)
3.
Instrument (e.g. camera = CAM)
4.
Sequence of camera deployments through the survey overall (e.g. first deployment = CAM01, second deployment = CAM02 etc).
For example, BT5_CAM16 is the sixteenth camera deployment of the survey overall, and was the fifth deployment using the beam trawl frame.
From the 93 stations, there were 75 successful camera deployments. There were no photos captured at 9 stations. This was due to the camera or strobes malfunctioning, the camera being too far from the bottom, or the camera or strobes being in the mud at the bottom. The photos at a further 9 stations are considered poor due to the camera being out of focus, the camera being a little too far from the bottom or because very few photos were captured of the bottom.
The benthic photo will be used to document the fauna and communities associated with representative habitats in the study area. The post-cruise analysis of the benthic photos will involve recording seabed geology and biology (class or order, and whatever is significant for the habitat) for each image

澳大利亚地质科学局（Geoscience Australia）与澳大利亚南极司（Australian Antarctic Division）联合开展了默茨冰川（Mertz Glacier）区域陆架的底栖生物群落（benthic community）调查，采用水下静态照片（underwater still photographs）作为研究手段。本次调查旨在采集陆架区海底高分辨率静态照片，以实现三大核心目标：
1.
调查默茨冰川舌曾覆盖区域及其东部原固定冰（fast ice）覆盖区的底栖生物群落组成
2.
调查已知冰山擦痕（iceberg scours）区域的底栖生物群落组成（或缺失情况）
3.
调查陆架坡折带（shelf break）沿线峡谷中冷水珊瑚群落（cold water coral communities）的横向分布范围。
底栖照片由佳能EOS 20D单反800万像素静态相机拍摄，该相机配备佳能EF 35mm f1.4 L USM镜头，置于额定深度2500米的平板端口阳极氧化铝外壳中。两台佳能580EX Speedlite闪光灯则安装在额定深度6000米的不锈钢外壳内，外壳配有半球形亚克力罩。相机与闪光灯由相机外壳内的28V 2.5Ah旋风式密封铅酸电池组供电，通过Brantner Wetconn系列水下连接器连接。拍摄参数为：100 ASA感光度，闪光补偿值+2/3档，手动对焦至7米，通常采用f2.8光圈与1/60秒快门速度，照片间隔设为10或15秒。
相机固定于CTD框架或桁拖网（beam trawl，BT）框架上，降至距海底约4-5米处。两个激光指示器间距50厘米，用于提供比例尺。相机共在93个站位部署：7个站位采用桁拖网框架，86个采用CTD框架。
站位名称由以下四部分构成：
1.
相机部署框架类型（如CTD或桁拖网BT）
2.
框架序列编号（如CTD53）
3.
仪器类型（如相机为CAM）
4.
调查期间相机部署的总序列编号（如首次部署为CAM01，第二次为CAM02等）。
例如，BT5_CAM16表示本次调查中第16次相机部署，同时是第5次采用桁拖网框架的部署。
93个站位中，75次相机部署成功。9个站位未捕获任何照片，原因包括相机或闪光灯故障、相机距海底过远，或相机/闪光灯陷入海底泥中。另有9个站位的照片质量不佳，问题涉及相机失焦、距海底稍远，或海底照片数量极少。
底栖照片将用于记录研究区域内代表性栖息地相关的生物群与群落。航后分析将针对每张照片记录海底地质特征及生物信息（包括类或目水平分类，以及栖息地相关的重要特征）。