Circulation of water through a mussel raft: clearance area vs. idealized linear flows

Abstract

This study suggests revision of ecological concepts as food depletions and/or water flow reductions based on idealized linear flows through mussel rafts. We offer an alternative based on the extension of the clearance area, defined as the area affected by the nonlinear effects produced by each raft and surroundings ones. These conclusions are supported by our results, which indicate that (i) the preferential entry of water through a mussel raft does not occur through the bow, contrary to previously thought, and (ii) the intraraft circulation is strongly influenced by the orientation of the raft relative to the background current direction and does not follow a defined pattern. Intraraft circulation is assessed by means of four current metres installed at each side of the raft and the dimensions of the clearance area using long-term data provided by GPS and compass. While both intraraft circulation and clearance area dimensions are mainly controlled by tide, the net water exchange through the raft is reasonably explained by wind (velocity and direction) and river discharges.

Microscale pH and Dissolved Oxygen Fluctuations within Mussel Aggregations and Their Implications for Mussel Attachment and Raft Aquaculture

“…Whereas a promising explanation for hourly pH and oxygen excursions, DBL thickness is unlikely to result in the persistent hypoxia and acidification observed in this study. Within mussel aggregations, the most extreme excursion in pH (<7.0) and oxygen (<5.0) was maintained for more than 5 days in the summer at depth, requiring a flow reduction for much longer than has been reported underneath aquaculture rafts (Blanco et al 1996, Grant & Bacher 2001, Aguiar et al 2017 or in tidally driven nearshore systems (Cahalan et al 1989, Leonard et al 1998. Alternatively, the fact that pH and oxygen excursions of this magnitude almost exclusively occurred at 7 m during the late summer could be explained by an accelerated accumulation of particulate organic matter, driven by an increase in primary productivity (Wieters et al 2003).…”

The Galician mussel industry: Innovation and changes in the last forty years

“…During this stage, a predictive model was developed on the food, its quality and abundance (Aguiar, 2015), and the analysis of growth models (Álvarez-Salgado et al 2017. Models were also developed of the water circulation in the Ría and through the rafts (Cranford et al 2014, Aguiar et al 2017 , which models allow to establish residence times and available food based on meteorological variables that determine such parameters and the potential clearance area of the raft. In the last decade, the increasing recurrence of harmful microalgae blooms (red tides) in the Galician Rías, especially of the genus Dynophysis, has become a serious problem for the management and exploitation of industrial mussel farming.…”

Literatuuronderzoek naar effecten van de configuratie van MZI-systemen op de productie van mosselzaad

“…wordt beschreven welke factoren in de configuratie van kweeksystemen de meeste invloed hebben op de productie van off-bottom kweeksystemen. (Boyd & Heasman 1998, Grant & Bacher 2001, Strohmeier et al 2005, Riethmüller et al 2006, Aure et al 2007, Stevens et al 2008, O'Donncha et al 2013, Aguiar et al 2017.…”