Rhodolith Beds Heterogeneity along the Apulian Continental Shelf (Mediterranean Sea)

Abstract

Rhodolith beds represent a key habitat worldwide, from tropical to polar ecosystems. Despite this habitat is considered a hotspot of biodiversity, providing a suite of ecosystem goods and services, still scarce quantitative information is available thus far about rhodolith beds occurrence and ecological role, especially in the Mediterranean Sea. This study reports the composition and patterns of distribution of rhodolith assemblages found in four study areas along ca. 860 km of coast in the Central Mediterranean Sea. These rhodolith beds were studied for the first time and significant differences at all spatial scales have been highlighted, documenting the high variability of this habitat. Rhodolith species composition, morphology and distribution have been discussed considering the potential role of environmental factors in driving these patterns. The need for improving their protection is discussed to complement present conservation and management initiatives, particularly in the frame of the EU Marine Strategy Framework Directive.

Morphostructural Characterization of the Heterogeneous Rhodolith Bed at the Marine Protected Area “Capo Carbonara” (Italy) and Hydrodynamics

“…These rhodoliths are associated with gravelly sand (Table 2). These results firstly underline that, although in MPA "Capo Carbonara" we identified a unique rhodolith bed, there is a strong morphostructural heterogeneity, as typical for some other Mediterranean rhodoliths beds [42,43]. The morphometrics definition of rhodoliths based on the quantitative description of morphotype and shape easily depicts such heterogeneity and surely represents the first and mandatory step for the evaluation of the variability of this kind of habitat, as suggested by Basso et al [29].…”

The Punta de la Mona Rhodolith Bed: Shallow-Water Mediterranean Rhodoliths (Almuñecar, Granada, Southern Spain)

“…Rhodolith beds dominated by this species have been reported off Murcia in Spain (Aguado-Giménez and Ruiz-Fernández, 2012) and several locations, such as the Balearic Islands (Barberá et al, 2012), Tyrrhenian Sea (Basso, 1995;Bracchi et al, 2019;Rendina et al, 2020b) and Adriatic Sea (Chimienti et al, 2020). The composition of Mediterranean rhodolith beds, however, is heterogeneous even in small areas (Chimienti et al, 2020). No clear pattern of species dominance can be observed at the regional scale, since Lithophyllum racemus (Sañé et al, 2016;Chimienti et al, 2020), Lithothamnion minervae (Rendina et al, 2020b), Spongites fruticulosus (Ballesteros, 1989;Joher et al, 2015), and Lithothamnion corallioides (Barberá et al, 2017) have been reported as dominant species in different beds.…”

“…Lithothamnion valens, the dominant species in the Punta de la Mona bed, is a Mediterranean endemic (Guiry and Guiry, 2022), which was considered a major structural component of a type of detrital bottom, called "facies de Lithothamnion valens," since the early descriptions of Mediterranean benthic habitats (Pérès and Picard, 1964). Rhodolith beds dominated by this species have been reported off Murcia in Spain (Aguado-Giménez and Ruiz-Fernández, 2012) and several locations, such as the Balearic Islands (Barberá et al, 2012), Tyrrhenian Sea (Basso, 1995;Bracchi et al, 2019;Rendina et al, 2020b) and Adriatic Sea (Chimienti et al, 2020). The composition of Mediterranean rhodolith beds, however, is heterogeneous even in small areas (Chimienti et al, 2020).…”

“…The morphospecies richness in the Punta de la Mona bed (25 morphospecies, 22 of them identified at the species level, in 9 genera) is the highest described in the Mediterranean so far in a single bed. Traditionally, the Mediterranean rhodolith beds have been considered richer than those of the eastern Atlantic at similar latitudes (Basso et al, 2017), although only 4-13 species have been reported from beds in the western Mediterranean (Ballesteros, 1989;Basso, 1998;Lanfranco et al, 1999;Mannino et al, 2002;Sciberras et al, 2009;Barberá et al, 2012;Basso et al, 2014;Nitsch et al, 2015;Sañé et al, 2016;Bracchi et al, 2019;Rendina et al, 2020b;Chimienti et al, 2020). The majority of rhodolith-forming species living in the Mediterranean (Basso et al, 2017;Rindi et al, 2019) have been recorded in the Punta de la Mona bed, except for Phymatolithon lusitanicum V. Peña (Peña et al, 2015), and Neogoniolithon hauckii (Rothpletz) RA Townsend & Huisman (Townsend and Huisman, 2018).…”

The Status of Posidonia oceanica at Tremiti Islands Marine Protected Area (Adriatic Sea)

“…The Tremiti Archipelago is characterized by a high diversity of habitats and species due to its position in the Adriatic Sea, benefiting from north-coming water masses, which bring nutrients from the northern part of the basin [ 69 , 70 ]. These peculiar oceanographic conditions support different habitats of great conservation value, including coral forests, rhodolith beds, and, at shallower depths, P. oceanica meadows [ 57 , 58 , 71 ]. Unfortunately, these habitats are currently suffering due to global warming, and heat-related mass mortality events have been recently reported at the Tremiti Islands, where extensive populations of the red gorgonian Paramuricea clavata (Risso, 1826) are largely affected by a combination of stressors, including heat waves, lowering of the thermocline, mucilaginous bloom, and massive macroalgal overgrowth [ 66 , 69 , 72 ].…”