title: Body Size Versus Depth: Regional and Taxonomical Variation in Deep-Sea Meio- and Macrofaunal Organisms.
abstract: Body size (weight per individual) is an important concept in ecology. It has been studied in the deep sea where a decrease in size with increasing depth has often been found. This has been explained as an adaptation to food limitation where size reduction results in a lowered metabolic rate and a decreased energetic requirement. However, observations vary, with some studies showing an increase in size with depth, and some finding no depth correlation at all. Here, we collected data from peer-reviewed studies on macro- and meiofaunal abundance and biomass, creating two datasets allowing statistical comparison of factors expected to influence body size in meio- and macrofaunal organisms. Our analyses examined the influence of region, taxonomic group and sampling method on the body size of meiofauna and macrofauna in the deep sea with increasing depth, and the resulting models are presented. At the global scale, meio- and macrofaunal communities show a decrease in body size with increasing depth as expected with the food limitation hypothesis. However, at the regional scale there were differences in trends of body size with depth, either showing a decrease (e.g. southwest Pacific Ocean; meio- and macrofauna) or increase (e.g. Gulf of Mexico; meiofauna only) compared to a global mean. Taxonomic groups also showed differences in body size trends compared to total community average (e.g. Crustacea and Bivalvia). Care must be taken when conducting these studies, as our analyses indicated that sampling method exerts a significant influence on research results. It is possible that differences in physiology, lifestyle and life history characteristics result in different responses to an increase in depth and/or decrease in food availability. This will have implications in the future as food supply to the deep sea changes as a result of climate change (e.g. increased ocean stratification at low to mid latitudes and reduced sea ice duration at high latitudes).
authors: Department of Zoology, University of Oxford, Oxford, United Kingdom. Electronic address: jesse.vandergrient@zoo.ox.ac.uk.
authors: Jesse M A
authors: JM
authors: van der Grient
authors: Department of Zoology, University of Oxford, Oxford, United Kingdom.
authors: Alex D
authors: AD
authors: Rogers
mesh_terms: D063147:Animal Distribution / Q000502:physiology*; D000818:Animals; D059001:Aquatic Organisms; D018533:Biomass; D049628:Body Size; D017753:Ecosystem; D007448:Invertebrates / Q000033:anatomy & histology* / Q000145:classification / Q000502:physiology*
keywords: Deep sea; Macrofauna; Meiofauna; Regional influence; Sampling; Taxonomic influence