Evidence for benthic body size miniaturization in the deep sea

Janne I. Kaariainen, Brian J. Bett
2006 Journal of the Marine Biological Association of the United Kingdom  
The benthic body size miniaturization hypothesis states that deep-sea communities are dominated by organisms of smaller body size, although some ¢eld studies have produced contradictory results. Using appropriate sample sets, this study tests this hypothesis by contrasting the benthic communities of the Fladen Ground (North Sea, 150 m) and the Faroe^Shetland Channel (1600 m). Samples were collected for large (500 mm) and small macrofauna (250^355 mm), meiofauna (45 mm) as well as an
more » ... sized 'mesofauna' (180 mm) to ensure comprehensive coverage of the full meio-and macro-faunal body size-range. The body size structure of the benthos was compared using two methods. The more widely used average individual biomass method involves dividing the total sample biomass by sample abundance. Additionally, body size accumulation curves were constructed by assigning all specimens into a logarithmic size-class and then plotting the cumulative percentage of individuals present in each size-class. The results seem to support the hypothesis that the deep-sea environment is a small organism habitat. Although these ¢ndings only represent two locations, the overall body size accumulation curves clearly display a statistically signi¢cant shift towards smaller body sizes at the deeper site. The magnitude of the e¡ect is appreciable with median metazoan body size reducing from 14.3 mg wet weight in the Fladen Ground to 3.8 mg wet weight in the Faroe^Shetland Channel. The average individual biomass measurements are shown to be of limited value and can lead to potentially misleading conclusions if the underlying sizestructure is not analysed in detail.
doi:10.1017/s0025315406014366 fatcat:hdcoklbxqjfq5npftbjxtnjsqm