Abstract

We studied growth and photosynthetic response of a shallow-water population of the invasive alga Caulerpa racemosa var. cylindracea off the Island of Ischia (Gulf of Naples, Italy). The effects of temperature on relative growth rate (RGR), light-saturated photosynthetic rate (P_max), dark respiration rate (R_d) and optimal quantum yield (F_v/F_m) were assessed for thalli collected in two seasons (early winter and early summer). While temperatures higher than 22°C stressed early winter thalli, as reflected in the decrease in growth rates and optimal quantum yields, both increased with temperature in early summer plants. A difference between the two seasonal samples also occurred in the high-temperature sensitivity of respiration rates, which was enhanced in early winter plants. As changes in a number of the traits considered occur in advance of seasonal minima and maxima, C. racemosa var. cylindracea may behave as a season anticipator. The contribution of observed patterns to the colonization success of the alga is discussed.