Exchange of nutrients and oxygen across the sediment–water interface below a Sparus aurata marine fish farm in the north-western Mediterranean Sea

Abstract

Morata, T.; Sospedra, J.; Falco Giaccaglia, SL.; Rodilla Alama, M. (2012). Exchange of nutrients and oxygen across the sediment-water interface below a Sparus aurata marine fish farm in the north-western Mediterranean Sea. Journal of Soils and Sediments. 12(10):1623-1632. doi:10.1007/s11368-012-0581-2. It is the first of its kind to be based on benthic flux data gathered in situ below fish farms for this particular area. Materials and methods Samples were collected on four samplingcampaigns over a 1-year cycle under a Sparus aurata fish farm facility where benthic fluxes were measured in situ using light and dark benthic chambers.Bottom water and sediment samples were also collected. Data were compared to those for a nearby control station.Results and discussion Significant differences were found (ANOVA,

Benthic fluxes of oxygen and nutrients in sublittoral fine sands in a north-western Mediterranean coastal area

“…Even over sand bottoms in the Gulf of Valencia, in a very shallow station (Vidal et al, 1989) at a depth of 18 m (Morata et al, 2012) measured oxygen uptakes were higher in both places than in this study. NPP in this study (99 and 1197 µmol m -2 h -1 ) was within the range observed in other permeable bottoms by Marinelli et al (1998) in the South Atlantic Bight (USA) at a depth of 20-40 m (-291 and 3065 µmol m -2 h -1 ) or Morata et al (2012), although the latter presented slightly lower values, (-417 and 708 µmol m -2 h -1 ). On the other hand, in areas with anthropic influence and river discharges such as in the Gulf of Trieste (Bertuzzi et al, 1997), NPP is not usually observed.…”

“…Benthic chambers, similar to those used by Freitas et al (2008) and Morata et al (2012;, were employed for the in situ calculation of the fluxes of DO, NH 4 + , NO 2 -+NO 3 -, PO 4 3-and Si(OH) 4 at the sediment-water interface.…”

“…An aliquot of 180 ml was withdrawn from each chamber, after the homogenization of the incubated water using a manual stirring in order to prevent concentration gradients, every 2-2.5 hours. Fluxes were calculated from the slope of a linear fit of the concentration distribution, following the methodology employed by Morata et al (2012;. Once fluxes in both light and dark conditions had been measured, the mean daily flux (F D ) was calculated using the equation used by Nizzoli et al (2007):…”

“…A large fraction of this pelagic primary production, as well as organic inputs from continent, can reach the sediment surface due to the shallow depth in the inner shelves (Huettel et al, 2014). At surface sediments, an excess of organic material can promote benthic primary production (Karydis and Kitsiou, 2012), organic matter accumulation and even can turn the seafloor anoxic (Morata et al, 2012). Organic matter present in the sediment is the main driving force of mineralization in inner shelve bottoms, which organic and nutrient production can be transported to water column by advective and diffusive transport or fixed by benthic photosynthesizers.…”

“…The study of benthic metabolism and nutrient exchange at the sediment-water interface in continental shelves have been focused on muddy and organic-rich sediments such as estuaries (Pratihary et al, 2009), salt marshes (Ferrón et al, 2009a), aquaculture production areas (Morata et al, 2012) or coastal lagoons (De Vittor et al, 2012).…”