Browsing by Author "Gestoso, Ignacio"
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- Local benthic assemblages in shallow rocky reefs find refuge in a marine protected area at Madeira IslandPublication . Alves, Filipe; Canning-Clode, João; Ribeiro, Cláudia; Gestoso, Ignacio; Kaufmann, ManfredThe patterns of variability in the composition and structure of benthic communities along two depth strata (5 and 10 m) and the presence of sea urchins in structuring the subtidal rocky reefs were quantified in a long-established coastal marine protected area (Garajau MPA) and in two size equivalent and contiguous impacted areas (one highly urbanized and other with high fishing pressure) at Madeira Island (northeast Atlantic). Results suggest i) the MPA could be acting as a refuge for local biodiversity, ii) communities from the highly fished area could be suffering an impoverishment of local biodiversity, and iii) communities from the highly urbanized area would be enriched by the establishment of opportunistic species. These findings support that the level of human-pressure likely plays an important role in the composition of benthic communities in this insular ecosystem, although this was more relevant at the shallower stratum where the key grazer Diadema africanum explained 65% of the variance of benthic assemblages. It is suggested that this MPA small dimension and proximity to human impacted areas are limiting the survival of predators of the D. africanum.
- The collapse of marine forests: drastic reduction in populations of the family Sargassaceae in Madeira Island (NE Atlantic)Publication . Bernal-Ibáñez, Alejandro; Gestoso, Ignacio; Wirtz, Peter; Kaufmann, Manfred; Serrão, Ester A.; Canning-Clode, João; Cacabelos, EvaSpecies of the genera Cystoseira, Ericaria, Gongolaria, and Sargassum (family Sargassaceae) are key components of the Mediterranean-Atlantic marine forests, essential for biodiversity and ecosystem functioning. Populations of these foundational species are particularly vulnerable to anthropogenic impacts, likely to be intensified under future scenarios of climate change. The decline and even disappearance of these species have been reported in different areas of the world. At Madeira Island (NE Atlantic), populations of Gongolaria abies-marina, Ericaria selaginoides, Sargassum vulgare, and Sargassum filipendula, the most ecologically relevant species in Macaronesian marine forests, have been suffering a drastic decline during the last decades, especially on the southern coast of the island, where anthropogenic pressure is higher than on the north coast. The lack of sufficient temporal coverage on qualitative and quantitative studies of Sargassaceae communities in Madeira poses a challenge to establish a specific period for this decline. Consulting qualitative studies and historical records, we have set for the first time a timeline that shows an evident decrease in Sargassaceae populations in the last 20 years on Madeira Island. Following this timeline, we pinpoint the start of this decline in the first decade of the 2000s. This can be particularly confirmed for places like Funchal and Reis Magos, with significantly higher historical records. Currently, most benthic communities on shallow subtidal rocky reefs along the south coast are dominated by sea urchins and crustose coralline algae, the so-called sea urchin barrens. However, in some cases, they are entirely covered by a layer of sediment. We discuss the possible factors contributing to these drastic changes, bringing Madeira’s marine forests to a dramatic decline. As many animal species rely on marine forests, the decline of Sargassaceae populations represents an invaluable ecological loss for the coastal ecosystem of the island.