Age and growth variability of the yellow clam (Mesodesma mactroides) in two populations from Argentina: implications under climate change

Abstract

Morphometric relationships and age and growth rates of the yellow clam (Mesodesma mactroides Reeve, 1854 = Amarilladesma mactroides (Reeve, 1854)) were compared in two populations from Argentina: Santa Teresita (36°32′00″S) and Mar del Plata (37°57′52″S). The Santa Teresita clams were heavier (shell, soft parts) than the Mar del Plata clams. Cross sections stained with Mutvei’s solution and acetate peels revealed an internal shell growth pattern of well-defined slow-growing translucent bands and alternating fast-growing opaque bands. Translucent bands (clusters) representing external rings were formed mostly during October in both sites, coinciding with gonadal maturation processes and spawning. Data confirm the annual formation of translucent bands in this species. Comparison of growth parameters showed a higher growth rate k and lower maximum age in Mar del Plata (8 years) than in Santa Teresita (9 years), which could be triggered by differences in salinity between localities due to the influence of the Rio de la Plata estuary, which is strongly linked to climate variability. Shell mass condition index and Oceanic Niño Index were negatively correlated, showing the influence of El Niño in shell properties of the species. Considering that events are becoming more intense and frequent, changes in growth rates and shell properties of Santa Teresita’s population could be expected to be more vulnerable under climate change.

Testing macroecological hypotheses in sandy beach populations: the wedge clam Donax hanleyanus in South America

“…Individual shell mass decreased at low salinities and increased with higher beach slopes, which characterize reflective beaches. Low salinity reduces the shell deposition rate (Malone & Dodd 1967) and leads to more fragile valves, as ob -served in the sympatric yellow clam Mesodesma mactro ides (Risoli et al 2020). Thicker valves found on reflective beaches may constitute an adaptation to the harsh swash climate, and considering that coarse sediments affect the burrowing capacity of D. hanleyanus (Marcomini et al 2002), thickness could reduce the risk of damage during burial (see also McLachlan et al 1995).…”

“…Latitudinal patterns in life-history traits have been observed in a broad range of intertidal organisms (Dugan et al 1994, Defeo & McLachlan 2005, Mc -Lachlan & Defeo 2018, including bivalves that dominate sandy-beach biota (Cardoso & Veloso 2003, Fiori & Defeo 2006, Moss et al 2016). These species also exhibit higher individual growth rates and lower longevity with increasing SSTs (Marquardt et al 2022), and a reduced abundance, survival, growth, and fecundity in beaches affected by large-scale salinity gradients (Schoeman & Richardson 2002, Risoli et al 2020, Celentano et al 2022 or low food availability (Risoli et al 2022). Concerning the role of local morphodynamics, a negative impact on life-history traits is expected in populations inhabiting reflective beaches compared to dissipative ones, according to the habitat harshness hypothesis (HHH).…”