Environmental forcing on growth and recruitment of marine bivalve species at Northern Patagonia, Southwestern Atlantic

DOLDAN, MARÍA DEL S.; GIMENEZ, LUCAS H.; MORSAN, ENRIQUE M.

Praga

Congreso; 9th European Congress of Malacological Socity; 2021

Malacological Socity of London

In coastal ecosystems, the recruitment of bivalves is characterized by year-to-year variability. Annual cohorts often differ in the number of recruits, resulting in irregular pulses of high abundance (i.e., successful recruitment) followed by periods of scarcity (i.e., failing recruitment). Environmental forcing likely underlies these pulses as favourable conditions (i.e., temperature, food availability) determine whether larvae settle and whether new recruits survive. As a factor that operates in a large-scale, it can also result in a synchronic recruitment of populations of multiple species within the same area. Sessile organisms represent a continuous record of environmental variability for a given location as a result of changes in annual growth rates. These changes can be seen in the shells as wide and narrow growth increments, representing favourable and unfavourable environmental conditions, respectively. At San Matías Gulf (Northern Patagonia, Argentina) the clam Glycymeris longior offers an opportunity to assess the effects of environmental forcing on the recruitment of commercial bivalve species along coastal ecosystems ofthe Southwestern Atlantic based on the growth anomalies recorded on its shells. In this context, we generated a multi-decadal growth chronology ( 60 years) using sclerochronological on G. longior live colleeted individuals. We assessed the relationship between annual standardized growth variability and environmental factors. We also analysed the coherence between G. longior growth and successful recruitments reported for three clam populations from the area (Panopea abbreviata, Ameghinomya antiqua and G. longior itself). We found a positive relationship between the sclerochronology and the mean sea surface temperature of autumn (Spearman correlation, p= 0.48, p= 0.04) and the Southern Annular Mode index for winter months (Spearman correlation, p= 0.54, p= 0.007). On the other hand, the successful annual recruitments corresponded to peak values of growth, particularly for the periods 1976-1979, 1982-1983, 1997- 1998. Our findings support a geographic large-scale coherence in recruitment for bivalve populations.