Publication Abstract

Seasonal changes in benthic fluxes of dissolved oxygen and ammonium asssociated with marine cultured Atlantic salmon

B.T. Hargrave, D.E. Duplisea, E. Pfeiffer and D.J. Wildish

Benthic fluxes of dissolved oxygen and ammonium were measured at bi-weekly to monthly intervals during 1990-91 proximate to and under an array of pens holding Atlantic salmon Salmo salar Linn. in L'Etang Inlet, a macrotidal embayment in the Bay of Fundy, Canada. Hierarchical clustering of data indicated that the 7 stations could be divided into 3 groups (3 stations under the pen array, 2 at the perimeter of the array and 2 away from pens). Average rates of oxygen uptake and ammonium release for the 3 stations under the pens were 4 and 27 times higher, respectively, than values at the 2 stations distant from the cages. Maximum average rates of ammonium release (38 mmol m^-2 d^-1) in late July and oxygen uptake (99 mmol m^-2 d^-1) in early September for stations under the pens coincided with maximum water temperatures and sediment sulfide accumulation, respectively. Negative redox (Eh) potentials (< 0 mV) and reduced numbers of benthic polychaetes Capitella spp. also occurred in sediments under pens between mid-July and September. Values of > 100 mM S^» in sediment pore water during September could have been toxic to benthic fauna as well as to heterotrophic bacteria that produce substrates utilized by sulfate-reducing bacteria.

Reference:

B.T. Hargrave, D.E. Duplisea, E. Pfeiffer and D.J. Wildish, 1993. Seasonal changes in benthic fluxes of dissolved oxygen and ammonium asssociated with marine cultured Atlantic salmon. Marine Ecology Progress Series, 96: 249-257.