7.3 Sampling Seamounts
On seamount voyages researchers will typically conduct a bathymetric survey (usually using multibeam sonar) of the target seamount. The resulting baythmetric map provides the basis for more detailed planning of the sampling program: plans that will take into account factors such as seamount size, shape, and depth. Echosounder information can also be used to identify substrate type and can guide sampling to target soft and hard bottoms.
The sampling gear and methodology used will depend on the nature of the research and thein situ conditions, for example weather and substrate. For biodiversity surveys, camera transects (undertaken using towed camera platforms, remotely operated vehicles, or submersibles) should be performed where possible. Remote methodologies have the advantage of being non-destructive and enabling researchers to view intact community composition, and to potentially gain valuable information on animal behavior. However, to quantify biodiversity fully, “ground-truthing” is required, and physical collection is vital for the completion of a full taxonomic inventory. A combination of sampling gears (for example grabs, corers, dredges, sleds, trawls) may be deployed on seamount surveys, but the hard and rough ground that frequently prevails on seamounts may limit researchers to the use of towed dredges or sleds (Fig. B7.3).
||Fig. B7.3 Researchers will typically conduct (A) a bathymetric survey followed by (B) camera transects e.g., Deep Towed Imaging System (pictured) and then collect physical specimens using a (C) beam trawl and/or (D) epibenthic sled (National Institute of Water and Atmospheric Research).
The sample from each gear type deployed is sorted on board and separated out as close to species or putative species (that is, apparently morphologically distinct organisms, sometimes called operational taxonomic units) as possible. The samples are then chemically fixed or frozen (following taxa-specific recommendations, as well as taking into account genetic sampling requirements). At the end of the voyage the samples will be delivered to taxonomists who will complete the final faunal inventory. This assessment of biodiversity can take many years, based on the high numbers of samples and low numbers of taxonomists.
Two working groups have helped drive the CenSeam research effort; the Data Analysis (DAWG) and Standardization Working Group (SWG). Members of each group have convened several workshops to tackle specific research questions and challenges, for example standardizing survey design, sampling, and analysis techniques (where possible) to facilitate geographic comparisons.