A Tropical Macroalga (Halimeda incrassata) Enhances Diversity and Abundance of Epifaunal Assemblages in Mediterranean Seagrass Meadows

Abstract

The introduction and successful expansion of tropical species into temperate systems is being exacerbated by climate change, and it is particularly important to identify the impacts that those species may have, especially when habitat-forming species are involved. Seagrass meadows are key shallow coastal habitats that provide critical ecosystem services worldwide, and they are threatened by the arrival of non-native macroalgae. Here, we examined the effects of Halimeda incrassata, a tropical alga that has recently colonized the Mediterranean Sea, on epifaunal assemblages associated with Cymodocea nodosa seagrass meadows of Mallorca Island (Western Mediterranean Sea). This invasive macroalga is an ecological engineer and thus has a high potential of modifying native habitats. A seagrass meadow colonized by H. incrassata exhibited important changes on associated epifaunal assemblages, with an increase in abundance and diversity, particularly driven by higher abundances of Gammaridae, Polychaeta, Copepoda and Caprellidae. Given the key ecological contribution of epifauna to food webs, these alterations will likely have important implications for overall food web structure and ecosystem functioning of native ecosystems.

Oxidative Stress Response in the Seaweed Padina pavonica Associated with the Invasive Halimeda incrassata and Penicillus capitatus

“…From previous studies, the quick and high colonization potential of P. capitatus and H. incrassata seem to be due to their invasive capabilities through efficient nitrogen metabolism [39,40], fast growth, and clonal reproduction by rhizoidal extension and fragmentation [10,38]. Moreover, both species have calcareous thalli that, combined with chemical defences, substantially reduce the susceptibility to herbivory in the new occupied areas [41]. All these traits are enhanced by the increase in the temperature, which allows them to extend their presence during the year and overgrow algal assemblies.…”

Halimeda incrassata (Bryopsidales, Chlorophyta) in Rhodes, Greece, Eastern Mediterranean

“…25.1 mg of O 2 per g of decalcified dry weight per day in Tahiti : Payri, 1988), nourishment (e.g. for the sea-urchin Diadema antillarum in Jamaica: Hillis-Colinvaux, 1974; for the bucktooth parrotfish Sparisoma radians in Virgin Islands: Lobel & Ogden, 1981 and for the pinfish Lagodon rhomboides in the Florida Keys: Ribble, 2019), shelter to other species (Heck & Wetstone 1977) and an ideal surface for the development of epifaunal organisms (Mateo-Ramírez et al, 2022). Although H. incrassata is not a significant competitor of the native phanerogam Posidonia oceanica, it is known to compete with other macrophytes including Dasycladus vermicularis (Sureda et al, 2017) and Thalassia testudinum (Davis & Fourqurean, 2001).…”