Project 6.3 - Field surveys: The objective of this work is to provide in situ community level data (major taxa and species, diversity, dominant growth forms, abundance, density etc.) for local filter feeders at two scales of survey (large scale: underwater video and scoring, small scale: SCUBA, sampling and analyses) and reveal which taxa or growth forms are habitat-forming and should be used for the experimental work (Project 6.4). The main focus will be on sponges, but other filter feeders will also be included at Class level (sponges vs. tunicates vs. cnidarians vs. bryozoans). In addition, this work will identify changes before vs. after the dredging work and therefore validate parts of the tank work. Subject to the consistency of responses across all filter feeders or immediately obvious patterns, we aim to identify of the most vulnerable organisms that may be used as biomonitors, and responses that may act as bioindicators for dredging-related stress. Samples will be collected to determine community attributes such as proportion of heterotrophy vs. phototrophy etc.
Fieldwork was conducted during two trips (2013 and 2015) aligned with dredging activities at Chevron's Wheatstone Project to allow a 'before dredging' assessment in comparison to 'after'.. Field surveys were conducted at two scales using different methods and answering different questions. Large-scale surveys: Sampling was conducted using underwater towed video. Some general principles are that (1) sample before any dredging activities have started and afterwards, (2) subject to access and benthic communities found by video work we will sample in nearshore, mid and offshore zones, and (3) where possible sample areas where there are existing baseline data or areas that will be monitored throughout the program in the compliance with the monitoring program (monitoring is thought to be based on quarterly sampling), (4) emphasize sampling in the ZHI where dredging impacts are likely and where sampling is often not conducted during dredging programs (as these areas are effectively sacrificial). Small-scale surveys: Replicated IS x 1m belt transects will be investigated and sampled on SCUBA depending on preliminary findings from the video work and conducted according to WAM protocol.
