Nearshore currents on the southern Namaqua shelf of the Benguela upwelling system

The physical oceanography of upwelling systems and the development of harmful algal blooms

“…12; Pitcher and Nelson, 2006), and are supported by observations of nearshore currents (Fawcett et al, 2008) and the barotropic model of Penven et al (2000) in the simulation of a coastal jet retention mechanism. During upwelling (Fig.…”

“…Of particular importance are inner shelf, poleward counter-currents, which may coexist with farther offshore, equatorward flow when upwelling winds relax or reverse to downwelling winds (Hickey, 1989; Sordo et al, 2001; Torres and Barton, 2007; Fawcett et al, 2008). These poleward flows tend to strengthen during the latter stages of the upwelling season, and have in some cases been associated with the poleward progression of HABs (Pitcher et al, 1998; Pitcher and Weeks, 2006).…”

Anoxia in southern Benguela during the autumn of 2009 and its linkage to a bloom of the dinoflagellate Ceratium balechii

“…Inshore stations on the 19 March were characterised by Chl a concentrations of <1 mg m À3 whereas a week later Chl a concentrations in parts of the bay exceeded 2000 mg m À3 . The appearance of red tide in the nearshore environment of the northern shoreline of St Helena Bay and its association with increasingly stratified conditions is known to be driven by alongshore flow from the north following wind relaxation and reversal of surface currents Pitcher and Nelson, 2006;Fawcett et al, 2008). The persistence of quiescent conditions and of blooms of the magnitude observed here poses an increasing risk of bloom collapse and decay leading to anoxia.…”

“…The mean alongshore flow of bottom water on the southern Namaqua shelf is poleward (Fawcett et al, 2008), and it is recognized that local shelf biogeochemistry is likely to be important in determining the oxygen content of this water (Chapman and Shannon, 1985). Increased deposition of organic carbon derived from primary production maxima in summer and autumn (Bailey, 1991), together with the development of an increasingly stratified environment exacerbate dissolved oxygen deficits leading to a progressive decline in dissolved oxygen concentrations in the cold bottom layer (Bailey and Chapman, 1991).…”

Distribution of Dinophysis species in the Bay of Biscay and possible transport pathways to Arcachon Bay

“…Pitcher et al (2010) reviewed HABs in the Benguela, California and Iberian upwelling systems. Particular features of these systems are innershelf, poleward counter-currents, which may coexist with farther offshore, equatorward flow when upwelling winds relax or reverse to downwelling winds (Fawcett et al, 2008;Hickey, 1989;Sordo et al, 2001;Torres and Barton, 2007). These poleward flows have in some cases been associated with poleward transport of HABs (Pitcher and Calder, 1998;Pitcher and Weeks, 2006).…”