Fish-seastar facilitation leads to algal forest restoration on protected rocky reefs

AbstractAlthough protected areas can lead to recovery of overharvested species, it is much less clear whether the return of certain predator species or a diversity of predator species can lead to re-establishment of important top-down forces that regulate whole ecosystems. Here we report that the algal recovery in a Mediterranean Marine Protected Area did not derive from the increase in the traditional strong predators, but rather from the establishment of a previously unknown interaction between the thermophilic fish Thalassoma pavo and the seastar Marthasterias glacialis. The interaction resulted in elevated predation rates on sea urchins responsible for algal overgrazing. Manipulative ex…

Synergistic reduction of a native key herbivore performance by two non-indigenous invasive algae

Abstract Native generalist grazers can control the populations of non-indigenous invasive algae (NIIA). Here, it was found that the simultaneous consumption of two co-occurring NIIA, Caulerpa cylindracea and C. taxifolia var. distichophylla, hinders the grazing ability of the main Mediterranean herbivorous, the native sea urchin Paracentrotus lividus. The ingestion of any of the two NIIA alone did not produce any difference in sea urchin righting time with respect to usual algal diet. In contrast, the simultaneous consumption of both NIIA, which grow intermingled in nature and are consumed by P. lividus, retarded its righting behavior. Such result reveals substantial physiological stress in…

Distribution and diet of Marthasterias glacialis at Ustica Island MPA

Distribution and diet of Marthasterias glacialis was studied at Ustica Island MPA. We conducted observations of the asteroid along the upper infralittoral zone using random parallel transects. M. glacialis was more abundant at study sites characterized by low densities of erect algae. Most frequent prey species was a bivalve and sea urchins

Il progetto S.E.P.I.A. (Sperimentazione sull’Educazione Pubblica ed Informazione Ambientale) nell’Area Marina Protetta “Isola di Ustica”.

Effetti della raccolta ricreativa sulla distribuzione di Paracentrotus lividus e Arbacia lixula nell’amp “Isola di Ustica” (Mediterraneo occidentale, Italia).

The rise of thermophilic sea urchins and the expansion of barren grounds in the Mediterranean Sea

Recent ecological studies have shown a strong relation between temperature, echinoids and their grazing effects on macro-algal communities. In this study, we speculate that climate warming may result in an increasingly favourable environment for the reproduction and development of the sea urchin Arbacia lixula. The relationship between increased A. lixula density and the extent of barren grounds in the Mediterranean Sea is also discussed.

Atmospheric CO2 Concentrations in Caves Protected as Nature Reserves and Related Gas Hazard

Atmospheric CO2 concentrations can reach high levels inside natural caves, representing a hazardous condition for both humans frequenting the underground environment and its safeguard due to the corrosion of speleothems induced by the acidification of atmospheric moisture. These issues are particularly critical for the eco-sustainable management of caves protected as nature reserves and undergoing touristic exploitation. In this paper we present the results of the C6 project, which was activated in 1999 for the monitoring of air quality inside three caves protected as nature reserves in Sicily (Italy). Near-real-time and spot measurements of air temperature and CO2 concentration have been c…

Diet and trophic interactions of Paracentrotus lividus and Arbacia lixula in two alternative stable states of the Mediterranean rocky sublittoral community

An integrated approach to investigate the seismotectonics of northern Sicily and southern Tyrrhenian

Abstract This paper deals with a comparison among recent structure and seismicity in the hinge zone between northern Sicily and southern Tyrrhenian, corresponding to both emerged and submerged northern portion of the Maghrebian chain. This hinge zone is part of a wider W–E trending right-lateral shear zone, mainly characterized by both a synthetic NW-SE/W–E oriented, and antithetic left-lateral N–S/NE-SW fault systems, which has been affecting the tectonic edifice, since the Pliocene. The inland structures have been mapped using aerial-photo interpretation, geological mapping and mesostructural analysis to reconstruct the stress regime in the study area. On the contrary, the offshore struct…

Sea temperature and echinoid Arbacia lixula (L.) population fluctuations on Ustica Island MPA

Influenza della protezione sulla struttura dei popolamenti algali. AMP "Isola di Ustica", un caso di studio

Native predators control the population of an invasive crab in no-take marine protected areas

1. The resistance of an ecosystem to species invasion is considered to be related to the abundance and diversity of native species i.e. biotic resistance hypothesis). Theory predicts that the high native diversity in pristine systems can hinder the establishment and/or the spread of non‐native species through direct and indirect mechanisms (e.g. through competitive and/or predatory interactions). 2. Here we tested whether predation provides higher resistance to invasion by the Percnidae crab Percnon gibbesi (H. Milne Edwards, 1853) in protected native communities, compared with exploited ones. Specifically, this study aimed to compare: (i) the abundance and diversity of potential predator a…

Unveiling the diet of the thermophilic starfish Ophidiaster ophidianus (Echinodermata: Asteroidea) combining visual observation and stable isotopes analysis

The starfish Ophidiaster ophidianus is an Atlanto-Mediterranean species protected under the EU’s Habitat Directive. Despite the wide distribution and the current range of expansion of this thermophilic species in the northern Mediterranean Sea, nothing is known about its diet. Using field observations and δ13C and δ15N Stable Isotopes Analysis (SIA), the feeding habits of O. ophidianus were explored in two Mediterranean rocky reef areas located in the southern Tyrrhenian (Ustica Island, Italy) and the eastern Adriatic Sea (Molunat, Croatia). According to field observations, O. ophidianus preys mainly on crustose coralline algae (CCA) and the keratose sponge Ircinia variabilis in both areas.…

Population structure of the sea urchins Paracentrotus lividus and Arbacia lixula across a depth gradient

Sea urchins are considered to have a paramount role in structuring rocky shallow communities. Under certain conditions, grazing by sea-urchins has been reported to produce a shift from macroalgae-dominated communities to barren habitat dominated by encrusting algae. However, this process is not recorded at all depths. The effect of depth on the structure of the sea-urchin populations may be thus a key feature to understand the origin and maintenance of the barren habitat within certain depths. In the present study, the structure of Paracentrotus lividus (Lam.) and Arbacia lixula (L.) populations are analyzed across a depth gradient in the Ustica Island MPA (NW Mediterranean), where the barr…

Interazioni e trofodinamica della megafauna bentonica associata a due stati stabili alternativi dell'infralitorale superiore roccioso del Mediterraneo.

Ruolo ecologico degli Asteroidei in due comunità dell'infralitorale superiore dell'Isola di Ustica

Gli asteroidi sono predatori che si ritrovano comunemente negli ecosistemi marini di fondo duro e mobile. Nell’Area Marina Protetta “Isola di Ustica” il divieto di raccolta del riccio edule Paracentrotus lividus nell’infralitorale superiore, ha determinato la sostituzione della comunità ad alghe fotofile erette con una comunità dominata da alghe incrostanti e ricci (barren) in gran parte dell’isola. Tre specie di asteroidi, Marthasterias glacialis, Ophidiaster ophidianus e Coscinasterias tenuispina, si ritrovano comunemente sia nell’habitat dominato dal barren che in quello dove rimangono elevate coperture ad alghe fotofile erette. Sono state studiate la distribuzione e le abitudini aliment…