Coralline composition of rhodolits beds: Marine Strategy monitoring

Cecchi E., Marino G., Baino R., Fani F., Mancusi C., Ria M., Verniani D., Voliani A., Benedettini G.

ARPAT, Agenzia Regionale per la Protezione Ambientale della Toscana, Settore Mare.

Introduction Experimental In the Mediterranean Sea Rhodolith To investigate rhodolith distribution Beds (RBs) have undergone to increase multibeam, side scan sonar (SSS) and anthropic and climate pressures, that remotely operated vehicle (ROV) were used resulted in species functional on an area of 25 km2. Samples were relationship changes. In spite of their collected with a box-corer. role, the distribution and structure of  Three RBs were sampled in RBs in the Mediterranean are scarcely Archipelago: Island (24-43 m of documented. The aim of the Marine depth, northern coasts), Island Strategy monitoring is to improve the (50-70 m, western coasts) and Meloria knowledge on rhodolith species Shoals (45-53 m). The percent coverage composition and geographical of the morphotypes was evaluated. Taxa distribution of RBs in Tuscany area. were analyzed with a Scanning Electron Microscope (SEM).

Results

From 2015 to 2018 in each location nine samples of 0.16 m2 were collected. Overall 12 taxa were identified confirming the RBs species composition reported for Tuscan Archipelago with some differences regarding the dominant taxa for each of the three location. The most frequent and abundant species were Lithothamnion crispatum and L. minervae. Elba Island showed lowest number of taxa (n=5) and a high variable coverage (between 10 to 95%), mainly represented by box-works (< 40%) and praline morphotype (30-95%). In Gorgona area 9 taxa were registered, with a coverage from 15% to 65%, and praline dominant morphotype (60-85%); box-work were dominant only in two sites. Along Meloria Shoals 10 taxa were present with a variable coverage (10-90%), mostly pralines and unattached branches.

c

(a) Lithophyllum crispatum (b) Lithothamnion minarvae (c) Phymatolithon calacreum (d) Spongites fruticulosus (e) Lithophyllum racemus (f) Lithothamnion sonderi

Conclusions

In the light of the obtained results that evidence which species and morphotype characterize each sampling site, the different composition of Tuscan Archipelago RBs should be further investigated at different spatial scales, in particular in relation to environmental condition (i.e. water motion, sedimentation)