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MEPS 321:67-77 (2006)  -  doi:10.3354/meps321067

Macrobenthic biomass, productivity (P/B) and production in a high-latitude ecosystem, North Norway

Marianne Nilsen*, Torstein Pedersen, Einar M. Nilssen

Norwegian College of Fishery Science, University of Tromsø, Breivika, 9037 Tromsø, Norway

ABSTRACT: Macrobenthic invertebrate biomass, productivity (P/B ratio) and production were estimated for a high-latitude fjord ecosystem, Sørfjord, North Norway. A model including individual weight, temperature, depth, taxonomical group, tidal-zone position, faunal category, motility and habitat was used to estimate P/B ratios, and production was calculated by multiplying P/B by biomass. Average biomass, production, abundance and P/B were 307 g wet weight (ww) m–2 (SE = 84, SD = 595, n = 50), 89 g ww m–2 yr–1 (SE = 16, SD = 112, n = 50), 1912 N m–2 (SE = 204, SD = 1442, n = 50) and 0.29 yr–1, respectively. Converted to energy, average biomass was 441 kJ m–2 and production 185 kJ m–2 yr–1. Horizontal and vertical trends were only detected for abundance, but a Monte Carlo test confirmed that subareas, depth and sediments explained a significant part of the variance in the community composition. Polychaeta was the most abundant and productive group, while large mussels (Arctica islandica and Musculus niger) and detrivorous asteroids (Ctenodiscus crispatus) dominated biomass. Even if biomass should always be measured for the area in question, P/B ratios from this study are considered reasonable for other North Norwegian fjords and coastal areas with similar conditions when an approximate measure of production is needed. In Sørfjord, the macrobenthic invertebrate production was much higher than the amount eaten by fish, and predatory benthos are probably more important consumers of benthic invertebrates.

KEY WORDS: Macrobenthos · Macrobenthic invertebrates · Production · Productivity · P/B ratio · Biomass · Abundance · High-latitude systems

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