Abstract
Habitat loss is jeopardizing marine biodiversity. In the Mediterranean Sea, the algal forests of Cystoseira spp. form one of the most complex, productive and vulnerable shallow-water habitats. These forests are rapidly regressing with negative impact on the associated biodiversity, and potential consequences in terms of ecosystem functioning. Here, by comparing healthy Cystoseira forests and barren grounds (i.e., habitats where the macroalgal forests disappeared), we assessed the effects of habitat loss on meiofaunal and nematode biodiversity, and on some ecosystem functions (here measured in terms of prokaryotic and meiofaunal biomass). Overall, our results suggest that the loss of Cystoseira forests and the consequent barren formation is associated with the loss of meiofaunal higher taxa and a decrease of nematode biodiversity, leading to the collapse of the microbial and meiofaunal variables of ecosystem functions. We conclude that, given the very limited resilience of these ecosystems, active restoration of these vulnerable habitats is needed, in order to recover their biodiversity, ecosystem functions and associated services.
Highlights
The decline of macroalgal forests has been widely documented in the Mediterranean Sea: 9 species of Fucales were reported 25 years ago, and only 5 species of the 14 reported in early 1900s are present in the NW M editerranean[17,18]
In the present study we investigated the relationships between biodiversity and ecosystem functioning and efficiency comparing macroalgal forests and barren grounds in six areas of the Mediterranean Sea
These results were compared with data on meiofaunal variables (i.e., richness of meiofaunal higher taxa, expected species number ES(51), index of trophic diversity 1-ITD and maturity index MI and sedimentary organic matter, measured as biopolymeric C concentration, BPC) previously reported from the same a reas[36] (Fig. 1A)
Summary
Several species of this genus are protected by the “Convention on the Conservation of European Wildlife and Natural Habitats” (i.e., Bern Convention), recognized as a priority by the Barcelona Convention and considered vulnerable by international organizations (i.e. IUCN, RAC/SPA, MedPan) In terms of their contributions to ecosystem functions, seaweed-dominated nearshore habitats have been ranked among the most relevant carbon sinks (ca 173 TgC year−1 sequestration29), leading to so called “blue carbon strategies”, aiming at exploring the potential of vegetated-marine habitats for mitigating climate change[30,31,32]. Due to their relevance in the provision of ecosystem s ervices[15], the magnitude of macroalgal forests decline is Scientific Reports | (2020) 10:19970
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