Ecosystem status and functioning: searching for rules of thumb
using an intersite comparison of food-web models of Northeast
Atlantic continental shelves
Lassalle, G., Lobry, J., Le Loc’h, F., Mackinson, S., Sanchez, F., Tomczak, M. T., and Niquil, N.
ICES Journal of Marine Science; doi:10.1093/icesjms/fss168
This work aimed to provide a better understanding of how the structure and function of marine ecosystems and trophic control mechanisms influence their response to perturbations.

Comparative analysis of Ecopath models of four Northeast Atlantic ecosystems was used to search for rules of thumb defining the similarities and differences between them. Ecosystem indicators, related to the ecology of species interactions, were derived from these models and compared.

Two main questions addressed
(i) What are the main energy pathways and mechanisms of control?
(ii) Do these ecosystems exhibit the widespread and potentially stabilizing food-web structure such that top predators couple distinct energy pathways?

A strong bentho-pelagic coupling operated over the Bay of Biscay Shelf, while energy reached higher trophic levels mostly through pelagic compartments, in northern areas. Zooplankton was demonstrated to be trophically important in all ecosystems, acting as a regulator of the abundance of small pelagic fish.

A latitudinal pattern in flow control was highlighted by this analysis, with a significant contribution of top-down effect at higher latitudes. This top-down control of the Baltic Sea, combined with the fact that this ecosystem did not exhibit the potentially stabilizing two-channel structure, suggested a non-stable environment.

Implications for Good Environmental Status
This finding could have significant implications for the definition of indicators of Good Environmental Status for these large marine ecosystems, as it contrasts with the common view that state or pressure indicators should be systematically selected in  the upper part of the food-web.

Accepted 1 October 2012, Available online 2 November
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Updated: 2013-03-13
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