Dasysiphonia japonica

Invasion History

First Non-native North American Tidal Record: 0
First Non-native West Coast Tidal Record:
First Non-native East/Gulf Coast Tidal Record: 0

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General Invasion History:

The red seaweed Dasysiphonia japonica is native to the Northwest Pacific from Pacific Russia to China, including the Sea of Japan and East China Sea, and the Japanese Pacific Coast (Sjotun et al. 2010; Guiry and Guiry 2022). In Europe, it was first recorded on farmed oysters in Brittany, France, and now ranges from Norway to Galicia, Spain, and locations in the Mediterranean involved in oyster culture, including the Thau Lagoon, France, the Venice Lagoon, and the Gulf of Taranto, Italy (Sjotun et al. 2008; Petrocelli et al. 2016). This seaweed was first reported from Quonochontaug Beach, Charlestown, Rhode Island, on the Atlantic Coast of North America, and now is found south to the Great South Bay, Rhode Island, to Nova Scotia (Mathieson 2016; Newton et al. 2013; Savoie and Saunders 2013; Saunders 2022). Ballast water, hull fouling, and transplants of Pacific Oysters are all likely vectors for the introduction of D. japonica to Europe (Sjotun et al. 2008). Introductions of Pacific Oysters have been limited on the East Coast of North America, so shipping vectors are more likely in this region.

North American Invasion History:

Invasion History on the East Coast:

Dasysiphonia japonica was first reported from Quonochontaug Beach, Charlestown, Rhode Island, on the Atlantic Coast of North America in 2009, where it was found washed up by a storm (Schneider 2010). In 2010 to 2013, it was found at a variety of sites from Long Island Sound from Casco Bay Maine (MacIntyre et al. 2010; Schneider 2010; Newton et al. 2013; Savoie and Saunders 2013; Mathieson 2016). In 2012, four specimens of D. japonica were collected from Mahone Bay, Nova Scotia (Savoie and Saunders 2013). This seaweed now seems to be established in Nova Scotia (Saunders 2022, photos). Since 2018 D. japonica is established on the south side of Long Island, in Shinnecock Bay and Great South Bay (Young and Gobler 2021;Young et al. 2022).

 

Invasion History Elsewhere in the World:

Dasysiphonia japonica was first reported as Heterosiphonia japonica from Roscoff, Brittany, France, in 1984. In 1988, it was found in Galicia, Spain.  By 2007, D. japonica was found in 14 separate locations from northern Spain to Norway and Sweden. Many of these sites were also locations of intense oyster culture (Sjotun et al. 2008). In the Mediterranean D. japonica became established in the Thau Lagoon, France, the Lagoon of Venice (1998–1999; Sjotun et al. 2008) and the Gulf of Taranto (2014; Petrocelli et al. 2019).  Sjotun et al. (2008) consider both shipping and oyster-transfers as important vectors. New locations for Dasysiphonia japonica in Europe include the Orkney and Shetland Islands (Collin et al. 2015; Nall et al. 2015), and southwest Norway (Husa et al. 2004).

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Description

Dasysiphonia japonica grows as a flattened fan-shaped thallus, dichotomously branching in one plane, and attached by a disk-like holdfast, with rhizoids. The plants are deep rose-red and 20–200 mm tall. Some growth axes are prostrate and attached to the substrate by down-growing rhizoids. The central axes are covered by a cortex formed by rhizoids, small branchlets develop from single basal cells on almost every segment, contributing to a densely bushy appearance. The tetrasporangia  occur in pod-like stichidia (swellings). This species is abundant both as attached plants and in drifting masses. It was previously placed in the genus Heterosiphonia (Schneider 2010; Sjøtun; et al. 2008 Mathieson and Dawes 2017; Saunders 2022).

 

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Taxonomy

Ecology

General:

The red seaweed Dasysiphonia japonica has successfully invaded a wide range of warm-temperate and cold-temperate habitats in Europe and North America (Bjaerke and Rueness 2004; Sjotun et al. 2008; Newton et al. 2013; Glenn et al. 2020). It has colonized coastal areas prone to ice formation (Maine, Nova Scotia, Norway) but also areas with high summer temperatures (Long Island bays, Mediterranean lagoons) (Newton et al. 2013; Savoie and Saunders 2015; Sjotun et al. 2008). In culture, D. japonica tolerates temperatures from 0 to 30 ºC, optimally 19–25 ºC, and with best growth at 20–30 PSU. Sporelings survived 4 ºC, but showed little growth; growth was better at 6 and 10º C (Bjaerke and Rueness 2014). Sporelings survived at least 40 days in darkness, suggesting that survival in ballast water is possible. In culture experiments on the west coast of Sweden, D. japonica grew faster than several native seaweeds, and faster than the non-native Bonnemaisonia hamifera, which devotes much of its energy to producing antifeeding compounds (Sagerman et al. 2014). Although D. japonica did not produce easily detectable anti-feeding compounds, it was only grazed at low rates by herbivores. Homogenized D. japonica produces red-colored exudates which are toxic to invertebrates. Low palatability may explain the rapid rise to dominance in alga communities (Sagerman et al. 2015; Young et al. 2022).

Trophic Status:

Primary Producer

PrimProd

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Habitats

General Habitat	Oyster Reef	None
General Habitat	Marinas & Docks	None
General Habitat	Rocky	None
General Habitat	Unstructured Bottom	None
Salinity Range	Polyhaline	18-30 PSU
Salinity Range	Euhaline	30-40 PSU
Tidal Range	Subtidal	None
Tidal Range	Low Intertidal	None
Vertical Habitat	Epibenthic	None

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Life History

Dasysiphonia japonica has an alternating life cycle with two morphologically somewhat similar life-cycle phases, a diploid tetrasporophyte and a haploid gametophyte (Bold and Wynne 1978). However, the gametophytes are rarely seen in Japan or Europe (Bold and Wynne 1978; Sjotun 2008). The blades of the tetrasporophytes bear pod-like stichidia, which release carpospores. The tetrasporangia divide into a fourfold (cruciate) pattern to produce tetraspores. The tetraspores are released, and settle, and grow into gametophytes (Bold and Wynne 1978). However, these gametophytes rarely become fertile in European and North American waters. Reproduction is largely asexual, through fragmentation of small branchlets (pseudolaterals) which settle, produce rhizoids and grow on various substrates. In experiments, plants developing through fragmentation outnumber those produced by settling of tetraspores (Husa and Sjotun 2006). In introduced habitats, the life cycle of algae or flowering plants is often modified, which is consistent with a rule, called 'Baker's Law', which states that asexual life-cycle stages tend to predominate in invading populations. For example, North American and European populations of the introduced red alga Gracilaria vermiculophylla consist largely of diploid populations reproducing by fragmentation (Krueger-Hadfield et al. 2016). In Dasysiphonia japonica, the predominant plants are tetraspophytes, reproducing asexually (Husa and Sjotun 2006).

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Tolerances and Life History Parameters

Minimum Temperature (ºC)	0	Experimental (Bjaerke and Rueness 2004) and field (Sjotun et al. 2004)
Maximum Temperature (ºC)	30	Experimental ( (Bjaerke and Rueness 2004)
Minimum Salinity (‰)	20	Experimental (Bjaerke and Rueness 2004)
Maximum Salinity (‰)	38	Based on occurrence in the Mediterranean
Minimum Reproductive Temperature	17	For sexual reproduction in cultures (Bjaerke and Rueness 2004)
Maximum Reproductive Temperature	24	For sexual reproduction in cultures (Bjaerke and Rueness 2004)
Minimum Reproductive Salinity	30	For sexual reproduction in cultures (Bjaerke and Rueness 2004)
Minimum Length (mm)	20	Mathieson and Dawes 2017
Maximum Length (mm)	200	Mathieson and Dawes 2017
Broad Temperature Range	None	Cold emperate-Warm temperate
Broad Salinity Range	None	Polyhaline-Euhaline

General Impacts

The red alga Dasysiphonia japonica has shown a pattern of rapid spread and population growth, sometimes becoming a biomass dominant, altering habitat. In some cases, the period of dominance is followed by a decline. This alga has functioned as a a habitat engineer and a modifier of food-webs (Dijkstra et al. 2007).

Competition- In surveys in 2012, from Casco Bay, Maine, to the mouth of Long Island Sound, Dasysiphonia japonica comprised 14% of the subtidal community, but 80% in some locations (Newton et al. 2013). On New England rocky reefs, D. japonica grew more rapidly than native filamentous algae and were associated with reduced community diversity. When raised in isolation, growth rates of D. japonica and native algae were comparable, as was grazing by herbivores, but in the context of the assemblage, D. japonica predominated. One factor was D. japonica's higher rate of nitrate uptake (Low et al. 2015).  Over 5 years of surveys in an area invaded by Dasysiphonia japonica (Nahant, Massachusetts) biodiversity decreased by 50%, but D. japonica became less aggressive, co-inhabiting member of the community (Ramsay-Newton et al. 2017).

Habitat Change- The replacement of native kelps by Dasysiphonia japonica decreased the preferred habitat for a native fish (Cunner, Tautogolabrus adspersus) seeking refuges from predators. However, the overall effects on this species are unknown (O'Brien et al. 2019).

Foodwebs- At the beginning of 5 years of surveys, in Nahant, Massachusetts,  Dasysiphonia japonica had an extremely high rate of nitrate-use efficiency, about an order of magnitude of that of other species.  Over the period of the survey, the nitrate-use efficiency of D. japonica dropped to levels comparable to those of other species (Ramsay-Newton et al. 2017).

Toxicity- Dasyiphonia japonica and the native red alga Gracilaria tikvahiae produce exudates that can inhibit the growth of the noxious brown tide picoplankter Aureococcus anophagefferens. Potentially, these effects could be useful in maintaining water quality, especially in aquaculture operations (Benitt et al. 2022). Sagerman et al. (2015) observed that 'red colored' exudates from D. japonica were toxic to crustacean herbivores. Decaying blooms of D. japonica in Great South Bay, Long Island created red discoloration of the water. Young et al. (2022) exposed fishes of two species (Cyprinodon variegatus, Sheepshead Minnow; Menidia beryllina, Tidewater Silverside), and larvae of  two bivalves (Eastern Oyster, Crassostrea virginica) and Hard Clam (Mercenaria mercenaria) to water that had contained decaying D. japonica. Exposure to this 'red water' caused 50–90% mortality in fishes and bivalves. The red water contained compounds resembling caulerpin, a known algal toxin, and other unidentified compounds (Young et al. 2022).

Fisheries- Dasysiphonia japonica has had adverse affects on commercial fishes in Rhode Island by clogging nets and lobster traps (National Fisherman 2004).

 

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Regional Impacts

NEA-II	None		Ecological Impact	Competition
Competition impacts were listed for the British Isles by Minchin et al. (2013).
NA-ET2	Bay of Fundy to Cape Cod		Ecological Impact	Competition
In the Gulf of Maine, where D. japonica was first discovered in 2010, by 2012 it has become the second most abundant macroalga in subtidal communities, comprising on average 17% of the community. At some locations, it had 100% coverage. Species richness was negatively correlated with H. japonica abundance (Newton et al. 2013). At Nahant MA, on Massachusetts Bay, Heterosiphonia japonica was dominant in areas with reduced native diversity, had higher rates of nitrate uptake, grew faster than other dominants, and had reduced grazing from a common herbivore, the native snail Lacuna vincta (Chink Shell). These differences were context-dependent; growth rates of the species did not differ in isolation in the laboratory (Low et al. 2014). However, the aggressiveness and nutrient uptake of D. japonica decreased in the 5 years since the initial invasion. The biodiversity of the community continued to be reduced after the invasion (Ramsay-Newton et al. 2016).
NA-ET3	Cape Cod to Cape Hatteras		Ecological Impact	Competition
In the Virginian Province (south of Cape Cod), where D. japonica was first discovered in 2009, it has by 2012, become the third most abundant macroalga in subtidal communities, comprising on average, 7% of the community. At some locations, it had up to 52% coverage. Species richness was negatively correlated with D. japonica abundance (Newton et al. 2013).
N170	Massachusetts Bay		Ecological Impact	Habitat Change
At Nahant MA, on Massachusetts Bay, Dasysiphonia japonica was dominant in areas with reduced native diversity, had higher rates of nitrate uptake, grew faster than other dominants, and had reduced grazing from a common herbivore, the native snail Lacuna vincta (Chink Shell). These differences were context-dependent; growth rates of the species did not differ in isolation in the laboratory (Low et al. 2014). However, the aggressiveness and nutrient uptake of D. japonica decreased in the 5 years since the initial invasion. The biodiversity of the community continued to be reduced after the invasion (Ramsay-Newton et al. 2016).
M020	Narragansett Bay		Economic Impact	Fisheries
Dassiphonia japonica has been clogging nets, lines, lobster and conch (whelk) pots in Rhode Island waters, causing serious problems for fishermen (National Fisherman 2014).
NA-ET3	Cape Cod to Cape Hatteras		Economic Impact	Fisheries
Dasysiphonia japonica has been clogging nets, lines, lobster and conch (whelk) plots in Rhode Island waters, causing serious problems for fishermen (National Fisherman 2014).
NA-ET2	Bay of Fundy to Cape Cod		Ecological Impact	Habitat Change
Around the Isles of Shoals, NH-ME, from the 1979 to 2015,  kelps and other larger brown seaweeds were becoming replaced by smaller, bushier red seaweeds (Bonnemaisonia hamifera, Dasysiphonia japonica, and Neosiphonia spp.) and Codium fragile, increasing the structural complexity of the environment, and the abundance and diversity of meso-sized invertebrates (Dijkstra et al. 2017). A mid-sized predatory fish, the Cunner (Tautogolabrus adpsersus) preferred kelps to the shorter, bushier seaweeds, dominated by D. japonica in experiments, but the type of seaweed community did not affect the fish's predation success on invertebrates (O'Brien et al. 2018).
N135	_CDA_N135 (Piscataqua-Salmon Falls)		Ecological Impact	Habitat Change
Around the Isles of Shoals, NH-ME, from the 1979 to 2015, kelps and other larger brown seaweeds were being replaced by smaller, bushier red seaweeds (Bonnemaisonia hamifera, Dasysiphonia japonica, and Neosiphonia spp.) and Codium fragile, increasing the structural complexity of the environment, and the abundance and diversity of meso-sized invertebrates (Dijkstra et al. 2017). The community of short, dense red seaweeds, expanding in the Gulf of Maine, is less preferred by a mid-sized native fish, Tsutogolabris adpersus (Cunner), compared to the declining beds of taller, simpler native kelp (Saccharina latissimus) (O'Brien et al. 2018).
B-I	None		Ecological Impact	Food/Prey
Dasysiphonia japonica was not preferred over native algae by native amphipods and isopods Idotea granulosa (Isopoda); Gammarus locusta; and Gammarellus angulosus (Sagerman et al. 2015).
M045	_CDA_M045 (Southern Long Island)		Ecological Impact	Competition
Favored by local ocean acidification and nitrogen pollution (Young and Gobler 2021)
M050	Great South Bay		Ecological Impact	Competition
Chemicals released by Dasysiphonia japonica and the native red alga Gracilaria tikvahiae inhibit the growth of the cryptogenic and noxious bloom-forming algae Aureococcus anophageffereans ('Brown tide').
NY	New York		Ecological Impact	Competition
Favored by local ocean acidification and nitrogen pollution (Young and Gobler 2021), Chemicals released by Dasysiphonia japonica and the native red alga Gracilaria tikvahiae inhibit the growth of the cryptogenic and noxious bloom-forming algae Aureococcus anophageffereans ('Brown tide').
MA	Massachusetts		Ecological Impact	Habitat Change
At Nahant MA, on Massachusetts Bay, Dasysiphonia japonica was dominant in areas with reduced native diversity, had higher rates of nitrate uptake, grew faster than other dominants, and had reduced grazing from a common herbivore, the native snail Lacuna vincta (Chink Shell). These differences were context-dependent; growth rates of the species did not differ in isolation in the laboratory (Low et al. 2014). However, the aggressiveness and nutrient uptake of D. japonica decreased in the 5 years since the initial invasion. The biodiversity of the community continued to be reduced after the invasion (Ramsay-Newton et al. 2016).
NH	New Hampshire		Ecological Impact	Habitat Change
Around the Isles of Shoals, NH-ME, from the 1979 to 2015, kelps and other larger brown seaweeds were being replaced by smaller, bushier red seaweeds (Bonnemaisonia hamifera, Dasysiphonia japonica, and Neosiphonia spp.) and Codium fragile, increasing the structural complexity of the environment, and the abundance and diversity of meso-sized invertebrates (Dijkstra et al. 2017). The community of short, dense red seaweeds, expanding in the Gulf of Maine, is less preferred by a mid-sized native fish, Tsutogolabris adpersus (Cunner), compared to the declining beds of taller, simpler native kelp (Saccharina latissimus) (O'Brien et al. 2018).
ME	Maine		Ecological Impact	Habitat Change
Around the Isles of Shoals, NH-ME, from the 1979 to 2015, kelps and other larger brown seaweeds were being replaced by smaller, bushier red seaweeds (Bonnemaisonia hamifera, Dasysiphonia japonica, and Neosiphonia spp.) and Codium fragile, increasing the structural complexity of the environment, and the abundance and diversity of meso-sized invertebrates (Dijkstra et al. 2017). The community of short, dense red seaweeds, expanding in the Gulf of Maine, is less preferred by a mid-sized native fish, Tsutogolabris adpersus (Cunner), compared to the declining beds of taller, simpler native kelp (Saccharina latissimus) (O'Brien et al. 2018). Edit Impact Delete Impact

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