The utilization potential, in terms of agar production, of the invasive alga, Gracilaria vermiculophylla, collected at Ria de Aveiro, northwestern Portugal was investigated. The agar yield ranged from 15% to 33%, with pre-extraction treatment with alkali generally increasing the yield. The gel quality (gel strength and apparent Young's modulus) was best (>600 g cm −2 and >1,000 kPa, respectively) when alkali treatment with 6% NaOH for 3.5 h was performed. At these pretreatment conditions, the effect of extraction time was also investigated and highest yield and best gel quality were obtained with a 2 h extraction time. By employing these extraction conditions, G. vermiculophylla can be a source of industrial food-grade agar. The structure of agar from G. vermiculophylla was determined through chemical techniques and FTIR and NMR spectrometry. It is mainly composed of alternating 3-linked D-galactose and 4-linked 3,6-anhydro-L-galactose, with methyl substitution occurring at 16-19 mol% of C-6 in 3-linked units and 2-3 mol% of C-2 in 4-linked units. A minor sulfation on C-4 of 3-linked units was also detected; while precursor units (6-sulfated 4-linked galactosyl moieties) were found in the native extract.

Large scale rearing of coral larvae during mass spawning events and subsequent direct introduction of competent larvae onto denuded reefs ("larval seeding") has been proposed as a low-tech and affordable way of enhancing coral settlement and hence recovery of degraded reefs. While some studies have shown positive short-term effects on settlement, to date, none have examined the long-term effects of larval seeding for a broadcast spawning coral. Here we test whether larval seeding significantly increases coral recruitment rates both in the short (5 weeks) and longer (~6 mo to 1 year) term. Larvae of Acropora digitifera were reared ex situ and approx. 1 million larvae were introduced to 7 artificial reefs (ARs) while 7 others were left unseeded. Settlement tiles deployed on both seeded and control ARs were retrieved for examination 5 and 30 weeks after seeding. In addition, the presence of visible coral recruits on the AR surfaces was monitored before and for ~13 months post-seeding. Density of acroporid spat was significantly higher on seeded tiles than controls 5 weeks after seeding but this effect had vanished by 30 weeks. Comparison of the densities of new visible Acropora recruits between seeded and control ARs showed no significant difference ~13 months after seeding. Larval seeding therefore had no long term effect due to high postsettlement mortality (which appeared to be density related). Results suggest that reef rehabilitation methods that aim to harness coral sexual reproduction might better focus on rearing juveniles through early post-settlement mortality bottlenecks.

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