Effects of the ‘Prestige’ oil spill on cellular biomarkers in intertidal mussels: results of the first year of studies

Natural variability in size and membrane stability of lysosomes in mussel digestive cells: seasonal and tidal zonation

“…In summer (August) 2005 (after the effects of the November 2002 Prestige oil spill were shown to remit significantly; Cajaraville et al 2006), HT mussels (from the 2.5 to 3 m level) were sampled, from the same breakwater as that in the previous experiment at suc-cessive time intervals: 30 min before emersion during a normal tide cycle (07:20 h), immediately just before emersion (07:50 h), every following hour (08:50, 09:50, 10:50, 11:50, 12:50 and 13:50 h) during aerial exposure, and a further 30 and 45 min after immersion into seawater during the next high tide (14:20 and 14:35 h).…”

“…Expt 1: In winter (March) and summer (August) 2001, mussels Mytilus galloprovincialis Lmk. were collected in Gorliz (Biscay Coast, 43°26' N, 2°55' W), a relatively non-polluted site (Orbea et al 2006) on the protected side of a breakwater adjacent to the beach, following a transect throughout the tidal zone. Mussels were sampled from subtidal (0 m tidemark level) and intertidal (0.5, 1, 1.5, 2, 2.5 and 3 m tidemark level) zones.…”

“…Nevertheless, since digestive cell lysosomes in LT mussels exhibit a pattern of seasonal variation, the range of variation for each particular study area must be established in order to design a proper sampling strategy in monitoring programmes. Thus, whereas along the Adriatic coast, lysosomal biomarkers do not show a strong dependence on season (Petrovic et al 2004), along the Basque coast seasonality is crucial (Etxeberria et al 1995) and winter samples appear to be meaningless as regards lysosomal biomarkers (Marigómez et al 2006, Orbea et al 2006. Particularly, in our study area, mussels collected around 1 m tidemark level are the best (or at least mussels below the 0.5 and above the 2 m tidemark levels should be discarded), since minor variability occurs between the 0.5 and 1.5 m tidemark levels in the studied lysosomal parameters and, in addition, seasonal variability is kept at a minimum in these mussels.…”

“…In contrast, subtidal mussels would have almost continuous food availability, making cyclic digestion more subtle, with less conspicuous changes in the morphology of digestive cells (Robinson & Langton 1980), which would possess a more stable and homogeneous endo-lysosomal system comprised of abundant small lysosomes (results of the present study). It is worth noting that, at any given moment, there is not necessarily a simple direct relationship between lysosomal Vv and LP; therefore, the principle that enlargement precedes destabilisation (Marigómez & Baybay-Villacorta 2003, Marigómez et al 2006) must be considered with caution when lysosomal biomarkers are interpreted.…”

“…Nevertheless, let's suppose that LT mussels exposed to air for 4 h are stressed as revealed by low LP values: why is lysosomal size reduced (low Vv and high S/V values) to the size of lysosomes in HT musssels? Low LP values may be indicative of environmental stress (ICES 2005, Marigómez et al 2006) but it should be accompanied by lysosomal enlargement (Moore & Viarengo 1987, Marigómez et al 2005. On the other hand, it is conceivable that after 4 h of air exposure, LT mussels have reached a late stage of intracellular digestion (i.e.…”