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

Abstract

Brown algae from genus Cystoseira s.l. form dense underwater forests that represent the most productive areas in the Mediterranean Sea. Due to the combined effects of global and local stressors such as climate change, urbanization, and herbivore outbreaks, there has been a severe decline in brown algal forests in the Mediterranean Sea. Natural recovery of depleted sites is unlikely due to the low dispersal capacity of these species, and efficient techniques to restore such habitats are needed. In this context, the aims of our study were (1) to improve and simplify the current ex situ laboratory protocol for the cultivation of Gongolaria barbata by testing the feasibility of some cost-effective and time-efficient techniques on two donor sites of G. barbata and (2) to evaluate the survival and growth of young thalli during the laboratory phase and during the most critical five months after out-planting. Specifically, the following ex situ cultivation methods were tested: (A) cultivation on clay tiles in mesocosms with culture water prepared by three different procedures (a) filtered seawater with a 0.22 μm filter membrane, (b) filtered seawater with a 0.7 μm filter membrane (GF), and (c) UV-sterilized water, and (B) cultivation on clay tiles in open laboratory systems. After two weeks, all thalli were fixed to plastic lantern net baskets suspended at a depth of 2 m in the coastal sea (hybrid method), and the algal success was monitored in relation to the different donor sites and cultivation protocol. The satisfactory results of this study indicate that UV-sterilized water is suitable for the cultivation of G. barbata in mesocosm, which significantly reduces the cost of the laboratory phase. This opens the possibility of numerous and frequent algal cultures during the reproductive period of the species. Additionally, if the young thalli remain in the lantern net baskets for an extended period of several months, they can grow significantly in the marine environment without being exposed to pressure from herbivorous fish.

Identification of Marine Biotechnology Value Chains with High Potential in the Northern Mediterranean Region

“…It is estimated that the key seaweeds grown in the Northern Mediterranean countries (including their Atlantic coasts) in 2030 could include, for instance, sea lettuce (Ulva lactuca) for human consumption, sugar kelp (Saccharina latissima) for use in food products and animal feed, dulse (Palmaria palmata) for the food and cosmetics sectors, Asparagopsis taxiformis for cattle feed additives with methane-reducing properties, and oarweed (Laminaria digitata) to produce alginate for use in the food additives and biopackaging segments [38]. An emerging field is also seaweed farming for the ecological restoration of marine macroalgal forests, given the predicted upscaling from small-scale, short-term academic experiments to industry and restoration practitioners, required to secure the oceans' sustainable future [39][40][41] and building up in the Mediterranean region on the knowledge produced by successful projects such as AFRIMED (http://afrimed-project.eu/, accessed on 17 March 2023) and ROCPOP-life (http://www.rocpoplife.eu/, accessed on 17 March 2023). Regardless on the target value chain, however, it is important to use the basic ecological knowledge of these species and avoid their introduction into new areas, especially where they might be considered invasive, such as is the case for some Asparagopsis species [42].…”

Too Hot to Handle: Effects of Water Temperature on the Early Life Stages of Gongolaria barbata (Fucales)

“…This study aimed to assess the effect of elevated temperature on germination and early thallus ontogeny of G. barbata in the northern Adriatic Sea, where the species still forms some algal forests in the shallow infralittoral zone [15,16,21,29,[65][66][67]. In this area, the species reaches its maximum vegetative and reproductive development from late winter to late spring/beginning of summer (February-May [29]), when sea temperatures range between 8 and 23 • C. The study deals with the development of zygotes and germlings at four different temperature treatments ranging from 15 to 28 • C, corresponding to the currently possible temperatures in the northern Adriatic Sea.…”