Chemical and physical features of living and non-living maerl rhodoliths

Abstract

Living (LM) and non-living maerl (NLM) rhodoliths of the species Lithothamnion corallioides (Crouan & Crouan, 1867) from Kingstown Bay, Galway, were sampled and compared in relation to their physical structure and lipid and low molecular weight carbohydrate (LMWC) composition. Saturated (SATFA) and polyunsaturated fatty acids (PUFA) were dominant, in particular 16:0, 20:4n-6 and 20:5n-3, but a diverse range of fatty acids were identified. The abundance of n-alkanals was high, and sterol composition was simple, with cholesterol accounting for over 90% of the total sterols. Mono-, di-, and trisaccharides, with galactose units being dominant, and floridoside were present in high abundance. Notably, the fatty acid and LMWC profiles varied little between NLM and LM. The relatively high abundance of PUFA and floridoside, in particular, suggests that NLM may have further potential for research and commercial purposes in a variety of food, biomedical and industrial applications. Previously reported unidentified 'globular inclusions' were more abundant in NLM and exhibited a crystalline morphology. Together with the bacterial fatty acid composition of LM and NLM, the results indicate that these structures are not bacterial in nature.KEY WORDS: Maerl · Coralline algae · Fatty acids · Floridoside · Lipids · Kingstown Bay · Galway Resale or republication not permitted without written consent of the publisherAquat Biol 15: [215][216][217][218][219][220][221][222][223][224] 2012 tion, as an animal fodder additive, in acid water treatment, in biological denitrification, in drinking water treatment, in toxin elimination and in the pharmaceutical, cosmetics, nuclear and medical industries (Blunden et al. 1975(Blunden et al. , 1977(Blunden et al. , 1997.The primary negative anthropogenic effects on maerl habitats are smothering with fine sediment from trawling and commercial exploitation (De Grave & Whitaker 1998, Grall & HallSpencer 2003, Wilson et al. 2004) and eutrophic conditions due to sewage and fish discharge (Wilson et al. 2004). The European Commission Council Directive 92/43/EEC, commonly known as the 'Habitats Directive', lists Lithothamnion corallioides and Phymatolithon calcareum in Annex V as being subject to management and conservation (European Council 1992). However, this only applies to Atlantic ex ploited maerl and not to any rarer species or non-commercially exploited maerl (Barbera et al. 2003). Data regarding the distribution of Irish maerl beds has been the topic of a recent report (De Grave & Whitaker 1999), which concludes that 65 to 70% of all confirmed maerl beds in Irish waters occur in the Galway-Connemara region, 20 to 25% occur in the southwest region, and the remainder occur along the Donegal coast, with an overall abundance of the order of 3 × 10 6 m 3 of exploitable maerl. With this vast resource, there has been renewed interest in maerl, both commercially and in terms of its ecological importance and conservation needs.To date, the primary focus of research on maerl has been ecolog...

The Critical Importance of Rhodoliths in the Life Cycle Completion of Both Macro- and Microalgae, and as Holobionts for the Establishment and Maintenance of Marine Biodiversity

“…The hypothesis that these inclusions were floridean starch was quickly rejected when iodine starch reaction turned negative for the inclusions (Figure 8). Likewise, the large size of the cellular inclusions excluded the concentric structures from being chloroplasts or bacteria (O'Reilly et al, 2012). Because we observed some coralline cells containing starch grains, and others which did not, we speculate that some of the cellular inclusions in biogenic rhodoliths are heterotrophic, consuming starch granules within perithallial cells of a rhodolith for their required maintenance.…”

Eukaryotic Life Inhabits Rhodolith-forming Coralline Algae (Hapalidiales, Rhodophyta), Remarkable Marine Benthic Microhabitats

“…The hypothesis that these inclusions were floridean starch was quickly rejected when iodine starch reaction turned negative. Likewise, their large size excluded the concentric structures from being chloroplasts or bacteria13. The main objective of this study was to resolve the true nature of the cellular inclusions in rhodolith-forming corallines using a suite of microscopy, culturing, and DNA sequencing tools.…”