Factors affecting variability in macroalgae

Macroalgae are known to be variable in chemical composition. Black (1950) mentions in his introduction to his work the importance of recording the history of the algae e.g. time of year, habitat, and depth of water as these may all have bearing on how experimental results are interpreted.

Basic sources of variability are found between the three major types or groups of macroalgae, Phylum Chlorophyta, Class Ulvophyceae, (green algae), Phylum Rhodophyta (red algae), Phylum Ochrophyta, class Phaeophyceae (brown algae). Differences were found by Matanjun et al. (2008), Pedersen, et al. (2008), Renaud & Luong-Van (2006), De Angelis (2005), Aguilera et

al.(2002), Bischof et al.(2002), and Wahbeh (1997) in their studies

encompassing green, red and brown macroalgae. These were collected from waters round Australia (Matanjun, et al. 2008), Renaud and Luong-Van 2006), the United States (Pedersen, et al. 2008), Canada and China (De Angelis 2005), Norway (Aguilera et al. 2002, Bischof et al. 2002)) and Jordan (Wahbeh, 1997). Compositional variability is also found within a Phylum, such as the Rhodophyta demonstrated by Dawes et al. (1974) or taxonomic class such as the Phaeophyceae (Rioux et al, 2007; Young et al. 2007; Bischof et al. 2002;

Black 1950; 1948abcd) and Ulvophyceae (Shanab et al. 2011).

Physical location can also affect chemical components, such as different localities as recorded by Rodríguez-Montesinos et al. 2008 working with

Macrocystis off the coast of Mexico and by Black 1950, 1948abcd who compared macroalgae growing in sheltered vs. exposed sea areas. Variability can even be affected by position on the foreshore (Pedersen, 2008).

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These variable chemical components may have possible pharmaceutical effects e.g. antioxidant (Huang and Wang 2004; Shanab et al. 2007), phenolics (Abdala-Díaz et al. 2006; Ragan and Jensen 1978), bioactive polysaccharides such as galactofucans (Honya et al. 1999; Rioux et al, 2009, Rioux et al, 2007) and photosynthetic pigments (Bischof et al. 2002; Aguilera et al. 2002). More frequently recorded however, are the major basic components such as ash, carbohydrates and sugars, total protein, alginates and lipids (De Angelis 2005;

McDermid and Stuercke 2003, Bird 1990; Black 1950, 1948abcd).

However, the majority of the studies mentioned above relate to single sampling events (Taboada, et al. 2009; Dawczynski, et al. 2007; De Angelis 2005; Sánchez-Machado, et al. 2004) or to purchased stocks of macroalgae (Rupérez and Saura-Calixto 2001). Frequently the month, season or sampling is not referred to (Gressler, et al. 2010; Marsham, et al. 2007; Huang and Wang 2004; McDermid 2003; Le Tutour et al. 1998). Therefore, these works, although useful can only provide a snapshot of the chemical components of macroalgae.

2.14.1 Seasonality in macroalgae

A major source of variability in composition can be attributed to the season of collection. The degree of seasonal changes can vary between

species within a taxonomic class such as the Phaeophyceae (Rioux et al. 2007;

Black 1950). Within a single species, it can also be attributed to season of collection (Adams et al. 2011a, Black 1950). A number of species have been examined over seasonal cycles with greater or lesser degrees of sampling intensity (Wahbeh 1997, Dawes et al. 1974, Black 1950 and 1948abcd).

2.14.2 Seasonal variation in the lipid and FAME of macroalgae

Up to the time of writing, no data on the seasonal cycling of lipids and FAME in macroalgae grown in UK waters has been recorded. Where seasonal sampling to measure FAME has occurred, although providing us with a more complete picture of seasonal cycles, it frequently is only one sampling occasion per season such as in Rodríguez-Montesinos and Hernández-Carmona (2008) and Shanab et al. (2011). Work involving multiple sampling events still tends to few sampling occasions; two collection dates are reported in Ginniken et al.

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(2011), Gómez-Ordóñez et al. (2010) and Sanina et al. (2008) and Renaud and Luong-Van (2006). Although in Ginneken et al. (2011) the interpretation of the results is somewhat confounded by the fact that there are only two sample dates but multiple countries of origin for the samples.

Although Renaud and Luong-Van (2006) and Dawes et al. (1974) did not find seasonal differences in tropical macroalgae seasonal differences in energy storage compounds such as mannitol and laminarin have been noted in cold-water species by Black (1950; 1948abcd). Multi-season sampling regimes such as Wahbeh (1997), Dawes et al. (1974) and all of the work by Black (1950;

1948abcd) give a more complete description of the seasonal cycling and the chemical composition of the macroalgae. Wahbeh (1997) looked at species such as Ulva lactuca, which although found in the UK, was collected from the warm waters off Jordan and it has been noted that species collected from warm waters have lower lipid content (De Angelis 2005).

2.14.4 Seasonal variation in the protein content of macroalgae

Black (1948abcd) found seasonal cycling in soluble sugars, protein and alginates in Laminaria hyperborea (Black 1948a)), L. digitata (Black 1948b), Saccharina bulbosa and S. latissima (Black 1948c) and Ascophyllum nodosum (Black 1948d). Seasonal variation has also been reported in protein content in selected macroalgae from tropical waters (Renaud and Luong-Van 2006), including Eucheuma spp (Dawes et al. 1974) and Macrocystis pyrifera (Rodríguez – Montesinos and Hernández-Carmona 1991).

From more temperate waters Fleurence et al. (1999) found that there was variation in the size of protein molecules with the season of collection Oct – Feb and their rate of breakdown by trypsin, chymotrypsin and human intestinal juice in Ulva armoricana. Yotsokura et al. (2010) found seasonal differences in the types of protein expressed in Saccharina japonica.

Appendix 2.3 also demonstrates the lack of seasonal data available regarding the protein content of macroalgae, particularly UK and temperate species from Northern latitudes. This information is required as it will inform the decision making process for the optimum harvest period of any macroalgae species used as biomass for biofuel production.

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2.14.5 Seasonal variation in the saccharide content of macroalgae

The increase in research into seasonal variation in macroalgae indicates the importance being placed on acknowledging the seasonal variability in some of the macroalgae saccharides e.g. laminarin can go from being undetectable to 33 % of the dry weight of the algae over the yearly cycle (Adams et al. 2011a; Black 1950). Therefore, for any process requiring macroalgae saccharides, knowledge of the appropriate harvest time for maximal yield is vital.

Appendix 2.4 indicates the frequency of seasonal sampling regimes when the saccharides of macroalgae have been investigated. Of the species of interest in this study Laminaria digitata has been examined by 5 research groups but seasonal work has only been undertaken twice; in 1948-50 (Black 1948a, Black 1950) and 2011 (Adams et al. 2011a). Seasonal work on the saccharides of Laminaria hyperborea was last undertaken in 1948 -1950 (Black 1948a, Black 1950). Seasonal measurement of soluble saccharides has been done once for Ascophyllum nodosum in 1948 (Black 1948d) and for Ulva lactuca in 2000 (Siddhanta et al. 2000). The other species in this study Fucus serratus, Fucus vesiculosis, Mastocarpus stellatus, Palmaria palmata and Porphyra umbilicalis have not had seasonal studies carried out before and little is known about their saccharides generally.