The transformation of long chain polyunsaturated fatty acids in benthic food webs: The role of sea urchins

Macroalgae play a major role in the carbon cycle of coastal ecosystems. A significant proportion of this production is consumed in situ, representing a major pool of carbon whose ultimate fate is poorly understood. In a controlled laboratory study using fatty acid analysis, the transformation of long-chain polyunsaturated fatty acids (LC-PUFAs) was studied. LC-PUFAs are a key food quality parameter at the level of both individual organisms and ecosystems. Sea urchins delivered LC-PUFAs to sediments in very low concentrations through the production of faecal pellets, while concentrating LC-PUFAs in the gonad and subsequently in larvae. Both the gonad and the larvae represent a rich source of LC-PUFAs to the pelagic and benthic food webs. The exact nature of this transformation and its subsequent transfer up the food chain is dependent on the species that consumes the primary productivity. Hence biogeochemical cycling in the coastal environment is dependant not only on gross primary production by macroalgae, but also on who consumes that primary productivity. (C) 2011 Elsevier B.V. All rights reserved.