ENVIRONMENTAL FORCING ON GROWTH AND RECRUITMENT OF MARINE BIVALVE SPECIES AT NORTHERN PATAGONIA, SOUTHWESTERN ATLANTIC

DOLDAN, M. SOCORRO; GIMENEZ, LUCAS H.; MORSAN, ENRIQUE M.

Praga

Congreso; Euromal 2021 - 9th European Congress of Malacological Societies; 2021

Czech University of Life Sciences Prague

In coastal ecosystems, the recruitment of bivalves is characterized by substantial year-to-year variability. Annual cohorts often differ in the number of recruits by orders of magnitude, 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 supply) determine whether larvae settle and whether new recruits survive. As a factor that operated in a large-scale, it can also result in 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 commercially important bivalve species along coastal ecosystems of the 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 techniques (i.e., growth increment measurement, detrending and standardization) on G. longior individuals collected in 2015-2016 (nshells = 8; nincrements = 281). 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 relation between the sclerochronology and the mean sea surface temperature of autumn (Spearman correlation, ρ= 0.48, p= 0.04) and the Southern Annular Mode index for winter months (Spearman correlation, rho = 0.54, p = 0.007). At a local scale, G. longior growth seems to be influenced by temperature and food supply. On the other hand, the successful annual recruitments corresponded to peak values of growth, particularly in the years 1976-1979, 1982-1983, 1997-1998. Our findings support a geographic coherence in recruitment for distant bivalve populations of three species. This pattern suggests that both growth and recruitment success seem to be influenced by environmental forcing.