First report, and seasonal characterization of the invasive rhodophyte Grateloupia turuturuin coastal Argentina

JERÓNIMO PAN ; M. ALEJANDRA MARCOVAL; NATALIA ARZOZ; VALERIA A. TIRONI

Congreso; Congreso Latinoamericano de Ciencias del Mar-COLACMAR 2019; 2019

The rhodophyte Grateloupia turuturu(Halymeniaceae) is a tropical-, highly-invasive macroalga from Japan, which has expanded its distribution range to theNW and NE Atlantic and the Mediterranean, throughaccidental human introductions. It has been cited for SBrazil and Uruguay in the SW Atlantic. Well-established specimens, representing a conspicuous, if not dominant component of the lower intertidal, were first observed in Argentina (SE Buenos Aires province) in January 2014, representing the first report of G. turuturu, at latitudes below 38°Sin the SW Atlantic. The objectives of this study were toseasonallycharacterize eco-physiological parameters of G. turuturu, and asses its reproductive/invasion potential.Environmental parameters (seawater temperature and salinity, light penetration in water column, planktonic chlorophyll a; and atmospheric PAR and UVradiation)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 (wet and dry tissue weight) were estimated at each site through randomly-sampledquadrats (n = 3; 0.5 × 0.5 m).Frond tissue chlorophyll a, UV-absorbing and antioxidant compounds werealsoestimated from freshly collected specimens. The seasonal reproductive potentialwas assessedthrough carpogonia density by microscopy (n = 4 fronds).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). 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 794.3gFW 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 wereseasonal- and site differences in vegetative-frond chlorophyll a(2-way ANOVA p0.05). Notably,G. turuturu retained its reproductive potential at winter seawater temperatures.Provided its reproductive potential, and the high biomass, G. turuturu has undoubtedly become a dominant member of the rocky intertidal below 38°S. Despite presenting seasonal variation in eco-physiological parameters, and a lack of significant vegetative biomass in winter, it has demonstrated considerable invasive potential for rocky intertidal environments. The ecological interaction, interference or positive effects with other components of the intertidal and subtidal community remain unknown.