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

PAN, JAB, MARCOVAL, MAB, ARZOZ, NB, TIRONI VC

Mar del Plata

Congreso; XVIII Congreso Latino-Americano de Ciencias del Mar (XVIII COLACMAR); 2019

Universidad de Mar del Plata

The rhodophyte Schyzimenia dubyi (Halymeniaceae; Fig. A) is a tropical-, highly-invasive macroalga from Japan, which has expanded its distribution to the NW and NE Atlantic and the Mediterranean, through accidental human introductions. It has been cited for S Brazil and Uruguay in the SW Atlantic. Well-established specimens, representing a conspicuous, if not dominant component of the lower intertidal (Fig. B), were first observed in Argentina (SE Buenos Aires province) in January 2014, representing the first report of S. dubyi, at latitudes below 38°S in the SW Atlantic. The objectives of this study were to seasonally characterize eco-physiological parameters of S. dubyi, and asses its reproductive/invasion potential in Argentina.Environmental parameters (seawater temperature and salinity, light penetration in water column, 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 location, namely: 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 at each site through randomly-sampled quadrats (n = 3; 0.5 × 0.5 m). Frond tissue chlorophyll a, UV-absorbing and antioxidant compounds were estimated from freshly-collected specimens. 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 at both sites (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 (equivalent to an average biomass of 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 at both locations. Likewise, there were seasonal- and site differences in vegetative-frond chlorophyll a (2-way ANOVA p