This field manual encompasses gear designed to sample unconsolidated sediment and organisms on the seafloor, including grabs, box corers, and push corers.
The samples collected by grabs and box corers can be used to derive a range of physical, chemical, and biological parameters (Eleftheriou 2013), and each of these parameters requires a particular method to process and analyse the sample (Danovaro 2010). In the interest of developing a standard protocol for marine monitoring that is readily accessible to multiple users among various disciplines, this field manual includes only a sub-set of these variables (Table 9.1). These variables were chosen because they can be used by multiple disciplines, are relatively easy to undertake, require minimal specialised equipment or chemicals, and are applicable to ecological indicators in marine monitoring (Hayes et al. 2015). Importantly, the protocol detailed here does not preclude other parameters from being investigated (e.g. Gallen et al 2019, Potter et al. 2022); rather it provides an achievable standard for acquiring fundamental data for monitoring that can be expanded as required to meet additional objectives on a given survey.
For information about how to sample microplastics from sediments, please see the Microplastics Field Manual.
This field manual does not include methods for sediment contaminant monitoring, as this is comprehensively covered elsewhere (Simpson et al. 2005). As activities develop (e.g. deep-sea mining) the scope may be expanded in future field manual versions to encompass sediment contaminant monitoring.
Other equipment able to sample sediment is not included in this field manual due to difficulties deploying in deeper waters (e.g. suction samplers) or limited applicability to biological sampling (e.g. gravity, piston, vibro-cores) (Eleftheriou and Moore 2013). In addition, multicorers are not explicitly included because small sample volume may preclude the collection of representative biological communities without aggregation (Williams et al. 2018), although we note that multicorer samples can be aggregated and processed as described in this manual. Although they are able to quantify infaunal activity, sedimentology, and biogeochemistry, sediment profile imaging (SPI) is also excluded from this field manual due to the vast differences in equipment requirements and data processing (i.e. imagery instead of sediment samples) (Aller et al. 2001, Germano et al. 2011).
Although larger grabs and box corers can sample larger macrofauna and megafauna, including epifauna, for the purposes of this field manual, we focus on smaller macrofauna, including infauna (e.g. Przeslawski et al. 2018). Epifauna are targeted in the Sled and Trawl Field Manual. If researchers opt to use a grab or box corer to sample epifauna, we recommend combining Pre-Survey Preparations and Onboard Sample Acquisition from this Field Manual with Onboard Sample Processing from the Sled and Trawl Field Manual (Chapter 8). Meiofauna and microbes are not included in this field manual, and we refer researchers instead to Somerfield and Warwick (2013).
For the purposes of this manual, macrofauna refer to organisms larger than 500 µm. There are varying definitions of faunal size classifications, and these differences seem to reflect the environment under consideration. For example, deep-sea researchers often consider macrofauna to be anything larger than 300 µm (e.g. De Smet et al. 2017) due to the prevalence of small body sizes in the deep-sea, while researchers in coastal or shelf waters are more likely to consider macrofauna as > 500 -1000 µm (e.g. Gray and Elliot 2009).
Table 9.1: List of potential measurements from grabs and corers, including whether they are included in this field manual.
| Parameter | Description | Included in field manual | |
|---|---|---|---|
| Sedimentology | Sediment texture | A measure of the proportions of mud, sand and gravel size fractions within a sample | Y |
| Mean grain size | A summary statistical measure of the size of sediment grains by using effective spherical diameter (ESD) | Y | |
| Kurtosis | A summary statistical measure of the range of grain size within a sample, ranging from platykurtic (wide range) to leptokurtic (narrow range) | N | |
| Skewness | A summary statistical measure of the size and direction of the tail in a sediment size frequency distribution, ranging from negative skewness (coarse-tailed) to positive skewness (fine-tailed) | N | |
| Carbonate | A measure of the proportion of a sample comprising calcium carbonate material | Y | |
| Mass physical properties | A measure of bulk or dry density, water content, porosity, or permeability | N | |
| Biogeochemistry | Organic matter content | A measure of the total organic matter content , organic carbon, or organic phosphorus | Y |
| Contaminants | Concentrations of various pollutants including heavy metals, PAHs, PCBs, etc | N | |
| Pigment | Quantification of chlorophyll-a, phaeophytin and other by-products of photosynthesis | Y | |
| Bioavailable organic matter | Quantification of carbohydrates, proteins and lipids | N | |
| Redox balance | Quantification of the Eh of sediments, providing an indication of anaerobic conditions and diagenesis | Y | |
| Sediment respiration | Quantification of the release of CO2 from sediments over time | N | |
| Porewater chemistry | Chemical characterisation of water between sediment grains | N | |
| Biology | Microbes | Abundance, biomass, or composition of viruses, bacteria and other prokaryotes, protists | N |
| Meiofauna | Abundance, biomass, or composition of metazoan meiofauna | N | |
| Macrofauna | Abundance, biomass, or composition of macrofauna | Y | |
| Megafauna | Abundance, biomass, or composition of megafauna | N | |
| Other | Plastics | Presence, type, and size of nano- or microplastics | N1 |