Description

The red alga Melanothamnus harveyi (formerly Polysiphonia harveyi; Neosiphonia harveyi)was described from CT in 1848, but has cytological features otherwise only known from Pacific members of the genus (Maggs and Stegenga 1999). Morphologically similar populations are found in the northeast Pacific, and are introduced and spreading in the northeast Atlantic. This species complex may have been described under at least 20 different names in different parts of the world. Molecular comparisons of RbCl genes of chloroplast DNA indicate that N. harveyi-resembling algae from Japan (P. japonica, P. harlandii), the northeast Pacific (CA, P. acuminata); New Zealand , the northwest Atlantic (NC), Britain , and Ireland indicate that these organisms are conspecific (Christine Maggs, 2000 pers. comm.). New Zealand and NC specimens were genetically identical. (McIvor et al. 2001). A revision of the genus put this species in the new genus Neosiphonia (Choi et al. 2001). A later revision moved the complex to the new genus and found M. harveyi and M. japonicus to be distinct species. Melanothamnus harveyi was more abundant, and more widely distributed, but M. japonicus was present at locations in RI and NC. Evidence of introgression betweenM. harveyi and M. japonicus was found from hode Island to Nova (Savoie and Saunders 2015).

Taxonomy

Kingdom	Phylum	Class	Order	Family	Genus
Protista	Rhodophyta	Rhodophyceae	Ceramiales	Rhodomelaceae	Melanothamnus

Synonyms

Polysiphonia harveyi; Polysiphonia olneyi; Polysiphonia insidiosa; Polysiphonia violacea; Polysiphonia acuminata; Polysiphonia harlandii; Polysiphonia japonica; Polysiphonia fibrillosa; Polysiphonia havanensis var. olneyi; Neosiphonia harveyi

Invasion History

Chesapeake Bay Status

First Record	Population	Range	Introduction	Residency	Source Region	Native Region	Vectors
1957	Established	Stable	Cryptogenic	Regular Resident	Western Atlantic	Western A;lantic	Shipping(Fouling Community, Ballast Water); Natural Dispersal(Natural Dispersal)

History of Spread

The taxonomy and biogeographic status of the red algal tribe Polysiphonieae has changed drastically in the past two decades. The red alga Melothamnus harveyi (until recently, Polysiphonia harveyi and later Neosiphonia harveyi (Choi et al. 2001; Savoie and Sauders 2915) was described from Connecticut in 1848 (Taylor 1957). Closely related species, NM japonica Harvey 1857, and P. akkeshiensis, both from Japan, and P. acuminata Gardner 1927, from California, were described. Features of cell structure and DNA sequences suggested that these forms constituted a single species of northwest Pacific origin, introduced into the Atlantic Ocean by the early 18th century (Maggs and Stegenga 1999; McIvor et al. 2001). However, later work supports the separate status of these three species (Kim and Yang 2006; Savoie and Saunders 2015).

Savoie and Saunders (2015) found that Melanothamnus harveyi was confined to the North Atlantic, while specimens of M. japonica were identified from the Northwest Pacific, and scattered records from California, Rhode Island, North Carolina, Spain. Western Australia, and New Zealand Kim and Yang 2006; (Savoie and Saunders 2015). Historical data supports the status of M. harveyi as an invader in the northeast Atlantic. It was first collected in Brittany, and described as M. insidiosa in 1867, and collected in the British Isles in 1908. Its range on the coast of Europe, now from Norway to the Canary Islands, is still expanding (Maggs and Stegenga 1999). It has been found in the Western Mediterranean in the Thau Lagon, (Sette, France) (1958, Verlaque 2001) and at La Spezia, Italy (McIvor et al. 2001). However, many of these populations will need to be re-examined for cryptic occurrences of N. japonica Savoie and Saunders consider N. harveyi to be native to the Northwest Pacific, but other authors point to its close morphological similarities to Indo-Pacific species (Kim and Yang 2006). Provisionally, we will treat it as cryptogenic in the Northwest Atlantic.

Invasion Comments

Ecology

Environmental Tolerances

	For Survival		For Reproduction
	Minimum	Maximum	Minimum	Maximum
Temperature (ºC)	0.0	30.0
Salinity (‰)	7.0	35.0
Oxygen
pH
	Salinity Range	meso-eu

Age and Growth

	Male	Female
Minimum Adult Size (mm)	30.0	30.0
Typical Adult Size (mm)	65.0	65.0
Maximum Adult Size (mm)	100.0	100.0
Maximum Longevity (yrs)
Typical Longevity (yrs

Reproduction

	Start	Peak	End
Reproductive Season
Typical Number of Young Per Reproductive Event
Sexuality Mode(s)
Mode(s) of Asexual Reproduction
Fertilization Type(s)
More than One Reproduction Event per Year
Reproductive Startegy
Egg/Seed Form

Impacts

Economic Impacts in Chesapeake Bay

As an abundant member of the fouling community in mid- and lower Chesapeake Bay, Melanothamnus harveyi could have economic impacts on boat and ship fouling, and on industrial water use. However, the relative importance of this species is not known.

Economic Impacts Outside of Chesapeake Bay

As an abundant member of the fouling community in many coastal waters around the world, Melanothamnus harveyi could have economic impacts on boat and ship fouling, and on industrial water use. However, the relative importance of this species is not known, and its small size may limit its importance (Eno et al. 1996).

References- Eno et al. 1996

Ecological Impacts on Chesapeake Native Species

Impacts of Melanothamnus harveyi on the Atlantic coast of the US have not been well-studied, because this abundant red alga has been historically regarded as native. In Europe, where it is a more recent invader, its impacts are better-known.

Competition- Melanothamnu is a common epiphyte on larger macroalgae and on Zostera marina (Eelgrass) (Matheison and Fuller 1969; Schneider and Searles 1991; Maggs and Stegenga 1999). Epiphytes, in high densities, can adversely affect growth of the host plant through shading and nutrient competition. Competition with other epiphytic species is also possible. However, the extent to which M. harveyi has affected native seaweeds and seagrasses is unknown.

Food/Prey, Toxicity- Observations in Europe suggest that this alga is resistant to grazers. 'Finally, we have observed that in heavily Littorina-grazed pools, M. harveyi is one of the few surviving seaweeds. Members of the Rhodomelaceae are perhaps one of the most prolific synthesizers of halogenated metabolites' (Maggs and Stegenga 1999).

References- Maggs and Stegenga 1999; Matheison and Fuller 1969; Schneider and Searles 1991

Ecological Impacts on Other Chesapeake Non-Native Species

Melanothamnus harveyii is a potential competitor with other introduced epiphytic algae, such as Bonnemaisonia hamifera, Stictyospiphon soriferus, and Striaria attenuata. It appears to be resistant to grazing by the snail Littorina littorea (Common Periwinkle) (Maggs and Stegenga 1999).

References- Maggs and Stegenga 1999

Melanothamnus harveyi

Algae