The role of grazers in early-life stages of Cystoseira sensu lato can be crucial in the restoration of marine forests

Abstract

Grazing is one of the most important biological factors controlling the abundance of early-life stages of fucoids and one of the major issues when restoring marine forests. Benthic macroinvertebrates (e.g., sea urchins) and fish shape and regulate benthic macroalgal communities from polar to tropical regions and can be responsible for regime shifts leading to the predominance of turfs and/or barren grounds. However, other herbivores (i.e., mesograzers) could also significantly participate in the grazing, especially on early-life stages, hampering the persistence and capacity of Cystoseira sensu lato populations to recover after major disturbances and being a cause of failure of restoration actions. We performed experiments in the field and in mesocosm in order to investigate the herbivory pressure and the effects of different grazers on recruits of Cystoseira compressa. The results highlight that non-strict herbivorous invertebrates, such as Clibanarius erythropus, Cerithium vulgatum, and Idotea balthica, graze on recruits of Cystoseira s.l. spp., with I. balthica showing the highest consumption rate. We concluded that biotic factors such as herbivory, which affect key life stages, can be crucial for the conservation of Cystoseira s.l. forests and need to be better understood and considered on a case-by-case basis when planning restoration actions.

A decision-support framework for the restoration of Cystoseira sensu lato forests

“…All present and potential future impacts have to be assessed (Cebrian et al, 2021), particularly natural ones such as extreme climatic conditions and climate change, which may be solved with identification of future potential restoration areas, and the use of different species strains or more tolerant species (Verdura et al, 2021). More efforts to understand the role of grazers (fish and invertebrates, including mesograzers, Monserrat et al, 2023) in the control of macroalgal forests are also needed to define strategies for reducing grazing pressure to an adequate level, over which the restoration programme would not be viable.…”

“…CARLIT/EEI-c Biological, chemical and nutrient waterassessment Cormaci and Furnari, 1999;Thibaut et al, 2005;Arevalo et al, 2007;Ballesteros et al, 2007;Devescovi and Ivesǎ, 2007;Pinedo et al, 2007;Mangialajo et al, 2008a;Irving et al, 2009*;Fraschetti et al, 2011;Orfanidis et al, 2011;Sales et al, 2011;Ivesǎ et al, 2016 Comparison of present and past historical data and mapping Gros, 1978;Thibaut et al, 2005;Sales and Ballesteros, 2010;Meinesz et al, 2013;Torras et al, 2016;www.medam Sala et al, 2011;Giakoumi, 2014;Vergeś et al, 2014;Gianni et al, 2017;Papadakis et al, 2021 Population density management Temporary herbivore management or exclusion can be considered for restoration actions Gianni et al, 2020;Papadakis et al, 2021 Sea urchins and other invertebrates Assessment of density, population structure and dynamic; barren mapping (e.g. barren areas) Verlaque, 1987;Arrighi, 1995;Sala et al, 1998;Ballesteros et al, 2002;Sala et al, 2012;Mariani et al, 2019;Monserrat et al, 2023; Huve, 1960;Gros, 1978;Benedetti-Cecchi and Cinelli, 1996;Piazzi and Ceccherelli, 2006;…”

“…can hinder survival and growth of the introduced individuals (Tamburello et al, 2019;Gianni et al, 2020). Other smaller invertebrate species, such as gastropods and decapods (e.g., marine snails and hermit crabs) can also graze the different life stages of canopy-forming species (Arrontes et al, 2004;Gunnarsson and Berglund, 2012;Hong et al, 2021;Monserrat et al, 2023;Navarro-Barranco et al, 2023). After a preliminary identification of herbivorous species and the assessment of grazing pressure on canopy-forming species, complementary actions of herbivory management should be integrated into the restoration program (Ballesteros et al, 2002;Cebrian et al, 2021).…”

Keep It Simple: Improving the Ex Situ Culture of Cystoseira s.l. to Restore Macroalgal Forests

“…On the other hand, open laboratory system cultures of Cystoseira s.l. can also be negatively affected by grazing pressure, especially at early-life stages [ 78 ]. Herbivorous gastropods, crustaceans, and polychaetes can also play a role in consuming various parts of the thalli, potentially affecting its biomass and the overall health of the algae [ 78 ].…”

“…can also be negatively affected by grazing pressure, especially at early-life stages [ 78 ]. Herbivorous gastropods, crustaceans, and polychaetes can also play a role in consuming various parts of the thalli, potentially affecting its biomass and the overall health of the algae [ 78 ]. Grazing plays a crucial role in regulating the density of canopy-forming fucoids and represents a major challenge in marine forest restoration efforts.…”