Page 1 - Poster2015

An evalua)on of Caulerpa cylindracea prolifera)on on the

marine ecosystem of the Preveto islet, Favignana, Egadi MPA, Italy
ROBERTO LO MONACO, PIERA BIONDI, GIOVANNI DIEGO MASUCCI, TOMMASO PINTO, GIANLORENZO VISCONTI1
1. Dipar?mento di Scienze della Vita e dell’Ambiente - Università Politecnica delle Marche
Contact: r.lomonaco@hotmail.it

INTRODUCTION

Caulerpa cylindracea (Caulerpaceae) is a tropical algae, which is invasive in the Mediterranean Sea. The observed consenquences of the C. cylindracea

invasion involve changes in the environmental condi?ons, in the marine landscape and in the structure of the benthic communi?es (Klein et Verlaque,

2008). Posidonia oceanica is a marine phanerogam endemic in the Mediterranean Sea. Its meadows are able to structure the marine landscape and are

responsible for many important ecosystem services like their contribu?on to primary produc?on, (Pergent et al., 1994), reducing par?cle resuspension

(Terrados, 2000) and as a nursery for the juveniles of many fish species (Kalogirou et al., 2010). These are some of the reasons why P. oceanica is

considered a species to protect (AOachment 1, DireQva Habitat). The Egadi MPA is the widest MPA in Europe and its P. oceanica meadow is one of the

largest in the Mediterranean Sea.

AIM OF THE STUDY

The aim of our study was to monitor the distribu?on and abundancy of C. cylindracea, in rela?on to the

P. oceanica meadow. We tried to evaluate the nature of the interac?on between C. cylindracea and

P. oceanica, which could have important consequences on the trophic net of the area.

MATERIALS AND METHODS

13 Point Intercept Transects (50m each) were conducted within the C zone, near the island of Favignana,

along the Preveto small island perimeter. We used reels with metered tape and the presence of P. oceanica

and C. cylindracea was registered meter by meter, along with informa?on about depth and substrate typology.

0 Every transect was georeferenced with a waterproof GPS device, at meters 1 and 50.

Depth(m) -2

-4 RESULTS

-6

-8 Geomorphological profiles enabled us to obtain data regarding the nature of the sea floor and its inclina?on.

-10 The graph on the lef shows an example of one of these profiles with P. oceanica and C. cylindrace added at
-12

-14 each depth. The sea floor is divided into a rocky por?on and another part covered by stones.
-16

-18 The overlapping points between the two species are circled in red.
-20

Geomorphological profile (transect n°10)

C. cylindracea/ P. oceanica

1. Considering the ra?o between the frequency of C. cylindracea and P. oceanica, a difference emerged between the northern sheltered side and 2
1,5

the southern exposed one, which consists of a major presence of C. cylindracea on the exposed part compared to the sheltered one. C/P 1

Rela)on between P. oceanica and type of substrate 0,5

100% 2. Taking into account the frequency of P. oceanica and C. cylindracea 0 Interno Esterno

Substrate frequency 90% depending on the type of substrate, a clear paOern showed that

80% Rock P. oceanica is much more common on sof boOoms. Conversely, it is less

70% present on rocky boOoms.
This rela?on proved to be highly significant (χ12= 130.61 >> 6.63; P < 0.01).
60% A similar paOern has not been observed in C. cylindracea, which is Hard BoWom SoV BoWom

50% therefore less influenced by the substrate, when compared to P. oceanica. Total substrate
Substrate with
40% Stones P. oceanica 256 394
% P. oceanica
30% 86 310

20%

10% Sand 34% 79%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
0%
P. oceanica frequency

3. Sta?s?cal analysis conducted on our data showed a nega?ve correla?on between 4. The graph above underlines the rela?onship between the slope of the marine
boOom and the frequency of P. oceanica (ρs |0.633 > 0.481| ; 13 DOF, P > 0.05) and
C. Cylindracea and P. oceanica. the correla?on proved to be non significant when we C. cylindracea (ρs |0.382 < 0.481| ; 13 DOF, P > 0.05). Higher inclina?on values are related
to a reduc?on of P. oceanica and to an increase in the abundancy of C. cylindracea.
considered all the available transects (ρs |0.444 < 0.481| ; 13 DOF, P > 0.05), but sta?s?cally

significant when only the sof boOoms were taken into account (ρs |0.662 > 0.535|; 11 DOF; P << Slope effect
0.05).
P. oceanica
[ρs= Spearman coefficient; DOF= Degrees Of Freedom; P= confidence level]
C. cylindracea
C. cylindracea frequency (meters) 18 Caulerpa/Posidonia: soV boWoms Frequency 100%
16 90% 10 20 30 40 50 60
14 5 10 15 20 25 30 35 40 45 50 80%
12 70% Sea floor inclina)on (Degrees)
10 P. Oceanica frequency (meters) 60%
50%
8 40%
6 30%
4 20%
2 10%
0 0%
0
0

FINAL DISCUSSION
Our results show that P. oceanica can be quite selec?ve about the nature of the substrate and the inclina?on of the sea floor. While the medow is generally very healthy. This natural
selec?veness could make it poten?ally more sensi?ve to different kinds of impacts. This paOern was not found with C. cylindracea, whose growth shows no correla?on either with the inclina?on
level or with the type of substrate. This makes us assume that the allochthonous alga may be less selec?ve, compared to the phanerogam, regarding the nature of the substrate. Finally, we
found that, where P. oceanica was abundant, C. cylindracea was less so and vice versa, which allows us hypothesize a possible inhibi?on effect. This study underlines the importance of the
conserva?on of P. oceanica, due to its poten?al ability to exert control over the prolifera?on of C. cylindracea. The large number of boats in Favignana during the summer season, along with the
rela?ve increase of anchoring events per day, emphasize the importance of the MPA existence. The Egadi MPA is therefore vital to manage such a strong anthropic presence and to protect this
unique ecosystem. We would like to thank all the staff of the MPA for their support which made this work possible.