Gracilaria vermiculophylla is a red macroalga that is cartilaginous, cylindrical and up to 50 cm long. It is coarsely branched, often profusely so. G. vermiculophylla can be found as loose-lying thalli or attached to small stones or shells. Red algae are often found in the vegetative state, and characterisation of reproductive structures is often necessary for correct identification of Gracilaria species (AlgaeBase 2010; Liao & Hommersand 2003; Nyberg et al. 2009; Rueness 2005).

Over 179 species are included in the genera Gracilaria and Gracilariopsis. The delineation of species in these genera has been notoriously difficult due to morphological similarities between species (Goff et al. 1994; Rueness 2005). Taxonomic problems have been particularly pronounced for Gracilaria vermiculophylla (Bellorin et al. 2004).

In a recent review Terada and Yamamota (2002 in Rueness 2005) reduced G. asiatica Zhang & Xia into synonymy with G. vermiculophylla.

The morphological similarities between G. vermiculophylla and other related algal species mean that the invasion of this alga is often cryptic, requiring DNA analysis for reliable identification (Thomsen et al. 2006a; Thomsen et al. 2006b). To avoid future taxonomic confusion Thomsen et al. (2006b) recommend researchers create silica-gel, air-dried, and/or herbarium presses as voucher specimens so that the correct identification can be confirmed using morphological and molecular analysis.

Gracilaria vermiculophylla is a perennial species with alternating generations (isomorphic life cycle). Dioecious haploid gametophytes produce either male or female gametes. These fuse to create a diploid zygote which grows into a diploid tetrasporophyte, (Nyberg et al. 2009; Rueness 2005; Thornber 2006). There is also a parasitic heteromorphic carposporophyte generation (Xie et al. 2010).

G. vermiculophylla is widely collected for the production of the biopolymer agar, which is used extensively in the pharmaceutical and food industries (Mollet et al. 1998; Sousa et al. 2010).

Gracilaria vermiculophylla is thought to be a temperate to subtropical alga, and can grow in both temperate and tropical regions. It is well-adapted to low energy, shallow-bottom bays, lagoons, estuaries, harbours and inslets (Yokoya et al. 1999; Thomsen & McGlathery 2007; Nyberg et al. 2009; M. S. Thomsen, pers. comm.). It forms extensive beds in the intertidal zone and upper sublittoral zones, where it attaches to rocks or pebbles, often covered with sand and mud (Bellorin et al. 2004). It often occurs as pure stands to the exclusion of other algae species (Rueness 2005).\r\n\r\n

G. vermiculophylla is able to grow in a wide range of temperatures (5-35 °C), light intensities (20–100 μmol photons m-2 s-1) and salinities (5-60 psu). Optimum growing conditions are between 15-25 °C and 10-45 psu (Rainkar et al. 2001; Rueness 2005). It is also tolerant to other stressses including sedimentation, desiccation, grazing and low nutrients (Rueness 2005). Nybert et al. (2009) found in one instance that this alga was able to survive in complete darkness for more than five months in the laboratory.

Gracilaria vermiculophylla reproduces by spores, which are non-motile, therefore restricting this alga to passive dispersal mechanisms. Male and female gametophytes and tetrasporophytes have a similar morphology (Freshwater et al. 2006; Nyberg et al. 2009; Woelkerling 1990, in Freshwater et al. 2006).

Gracilaria vermiculophylla belongs to the phylum Rhodophyta (red algae). Red algae are primitive photosynthetic eukaryotes (Xie et al. 2010).

Spread is likely to occur on vectors such as fishing and leisure boats (Nyberg 2007 in Nyberg et al. 2009).Fishing gear (Nyberg et al. 2009).

Ecosystem impacts: Gracilaria vermiculophylla inhibits the growth and survival of native algae through competition (Council of Europe 2009; Hamman et al. n.d.). It has been demonstrated to have negative effects on native seagrass beds of Zostera marina by decreasing net leaf photosynthesis and survival rates. Negative effects on seagrass are greater at higher temperatures, suggesting that impacts could increase with future ocean warming (Martínez-Lüscher & Holmer, 2010). In some areas such as Hog Island Bay in Virginia G. vermiculophylla dominate algal assemblages, in all seasons and elevation levels (Thomsen et al. 2006b). Accumulation of G. vermiculophylla may also impair environmental conditions for threatened Charophytes and Zostera noltii in Sweden (Gärdenfors 2005 in Nyberg et al., 2009).\r\n

In high abundance G. vermiculophylla may have dramatic effects on ecosystems. The introduction of G. vermiculophylla adds structural complexity to relatively homogenous soft-bottom systems and add new attachment sites for filamentous algae and sessile animals (Thomsen et al. 2006a; Nyberg et al., 2009). Thus G. vermiculophylla can provide shelter and food for other organisms, including microalgae, gastropods, crustaceans, polychaetes, and mny other small invertebrates. In Virginia research has shown that most invertebrate groups were positively affected by the presence of G. vermiculophylla in native algae (Thomsen et al., 2010).\r\n

While G. vermiculophylla may enhance local diversity, the ability to utilize increased habitat complexity will vary between species (Nyberg et al. 2009). Furthermore these changes could lead to effects on higher trophic levels (Aikins & Kukuchi 2002; Freshwater et al. 2006; Gustafsson 2005 in Nyberg et al. 2009; Nyberg et al. 2009; Thomsen et al. 2007c).\r\n

Loose-lying G. vermiculophylla populations have the potential to develop into dense mats, particularly in shallow bays, lagoons, harbours and estuaries. These mats can modify the habitat available for the benthic faunal community and bottom dwelling fish. Algal mats can also form physical barriers for settling larvae, decrease light intensity, increase the likelihood of anoxia and change water movement patterns, which in turn affects sedimentation rate and thus food availability for deposit feeders (Nyberg et al. 2009).\r\n

Additionally, the movement, accumulation and decomposition of G. vermiculophylla is likely to have important implications for nutrient cycling and trophic dynamics in areas it invades (Thomsen et al. 2009).\r\n

Fisheries: G. vermiculophylla is reported to be a problem in fishing industries through fouling of nets (Freshwater et al. 2000).

Accurate identification of Gracilaria vermiculophylla has been problematic in the past, leading to much confusion with similar species. DNA analysis, including rapid DNA barcoding, is now used for accurate identification (Bellorin et al. 2004; Saunders 2009).\r\n

Prevention: Movement of oysters is a major vector for the introduction of G. vermiculophylla to new locations worldwide. Thus making sure oysters are not transplanted may reduce the incidences of new infestations (M.S. Thomsen, pers. comm. 2011).\r\n

Physical control: Mechanical removal (harvesting) of G. vermiculophylla for use in the production of agar and other applications is a potential control method (Sousa et al. 2010; Villanueva et al. 2010).