Measurement Protocols for Macrobenthic Abundance and Biomass in the U.S. JGOFS EqPac Program

Craig R. Smith, David C. Kadko and David J. DeMaster

Macrobenthic abundance and biomass are the only biological measurements we will be conducting which can be considered to have ``standard'' protocols. Sediments from spade-core samples remaining after subsampling for geochemical analyses (approximately 0.19 m of surface sediment per box core, assuming a contribution of 300 cm to other JGOFS investigators) will be processed for macrofauna. The top 10 cm of each subcore will be removed; top-water-plus-0--1-cm, 1--5 cm and 5--10 cm depth intervals will then be preserved whole with 10 %-formalin-seawater solution. In the laboratory, samples will be transferred to 80 % ethanol, washed on 300-µm sieves and sorted under dissecting microscopes for macrofauna (see C. Smith (1986) for methods). We will identify all macrofauna to lowest possible taxon (at least to family level) and send materials to taxonomic experts for confirmation. Taxonomic identifications are critical to placement of deep-sea macrofauna into functional groups; a necessary step in identification of important bioturbators. Individuals subsequently will be assigned to trophic groups based on criteria described in Fauchald and Jumars (1979), and on results from core dissections and x-radiography. Size-distributions of macrofauna (for assessing mean body-size changes along the transect) will be obtained from body-size measurements using an ocular micrometer (Smith and Brumsickle, 1989). After identifications and measurements, macrofaunal biomass will be determined by pooling all animals from a box core and wet weighing them according to the methods of K. Smith et al. (1983) and Rowe (1983). A correction for preservation in formalin and ethanol will be made to biomass measurements.

There are no JGOFS protocols for macrofaunal abundance and biomass estimates, but our protocols do match those used for quantitative studies of deep-sea macrobenthos in the U.S.A. and U.K. (e.g., Rowe, 1983). In some other countries, a 500-µm screen is used as the size cutoff for macrofauna; however, there is strong evidence that a substantial fraction of those animals that function as macrofauna pass through a 500-µm screen, but are retained on a 300-µm screen. Thus, if JGOFS does adopt standard protocols for the processing of deep-sea macrofauna, we will push strongly for use of a 300-µm screen size.

Literature Cited

Fauchald, C. and P. Jumars (1979).
The diet of worms: a study of polychaete feeding guilds. Oceanography and Marine Biology. An Annual Review, 17:193--284.
Rowe, G.T. (1983).
Biomass and production of the deep-sea macrobenthos. pp. 97--121, In: The Sea, Vol. 8, Deep-Sea Biology, G.T. Rowe (ed.), Wiley Interscience, NY.
Smith, C.R. (1986).
Nekton falls, low-intensity disturbance and community structure of infaunal benthos in the deep sea. Journal of Marine Research, 44:567--600.
Smith, C.R. and S.J. Brumsickle (1989).
The effects of patch size and substrate isolation on colonization modes and rates in an intertidal sediment. Limnology and Oceanography, 34:1263--1277.
Smith, K.L., M. Laver and N. Brown (1983).
Sediment community oxygen consumption and nutrient exchange in the central and eastern North Pacific. Limnology and Oceanography, 28:882-898.