First report, and seasonal characterization of the invasive rhodophyte Schyzimenia dubyi in coastal Argentina

ARZOZ, NATALIA S.; MARCOVAL, MARÍA ALEJANDRA; PAN, JERÓNIMO; TIRONI, VALERIA A.

Mar del Plata

Congreso; XVIII Congreso Latinoamericano de Ciencias del Mar; 2019

ALICMAR

Grateloupia turuturu (Halymeniaceae; Fig. A) is a tropical-, highly-invasive macroalga from Japan, which has expanded its distribution to NW and NE Atlantic and the Mediterranean; it has been recently cited for S Brazil and Uruguay. Well-established specimens, representing a conspicuous, dominant component of the rocky-, lower intertidal (Fig. B) were observed in SE Buenos Aires province (Argentina) since January 2014, representing the first report of G. turuturu at latitudes below 38°S in SW Atlantic. The objectives of this study were to seasonally characterize eco-physiological parameters of G. turuturu, and asses its reproductive potential in coastal Argentina. Environmental parameters (seawater temperature and salinity, light penetration, planktonic chlorophyll a; and atmospheric PAR and UV radiation) were recorded in situ for each sampling event (March and June 2019; Austral summer and winter, respectively), at two locations: Chapadmalal (CHP; 38°12´S-57°42´W), and Mar del Sur (MDS; 38°20´S-57°59´W). Density and biomass (fresh and dry tissue weight) were estimated through randomly-sampled quadrats (n=3; 0.5×0.5 m). Vegetative-frond chlorophyll a, UV-absorbing and antioxidant compounds were estimated. The seasonal reproductive potential was assessed through carpogonia density by microscopy (n=4 fronds; Fig. C). There was a seasonal drop in seawater temperature from 18.1 to 10.9°C, while salinity remained constant (S=33.8); UV radiation dropped from 1.18 mW cm-2 in summer to 0.05 mW cm-2 in winter. Summer density was 281.3 and 152.0 fronds m-2, for the MDS and CHP populations respectively (biomass= 935.6 and 794.3 gFW m-2), with no significant differences (in either density or biomass) among sites (1-way ANOVAs p>0.05). There was a significant die-off in winter, leading to very poor standing stocks in June 2019. Conversely, there were seasonal- and site differences in chlorophyll a (2-way ANOVA p