Codium fragile (Suringar)

COMPILED BY: Anastasija Zaiko
CITATION OF THIS ENTRY: Zaiko A. 2005. Codium fragile. In: Baltic Sea Alien Species Database. S. Olenin, E. Leppakoski and D. Daunys (eds.).
INTERNET: http://www.corpi.ku.lt/nemo/mainnemo.html

TAXONOMY

Codium fragile (Photo by Sergej Olenin)

IDENTIFICATION

• Diagnosis:

Codium fragile is a dark green alga, ranging from ten to forty cm high and consists of repeatedly branching cylindrical segments about 0.5 to 1.0 cm in diameter, and the branches can be as thick as pencil. The segments look like dark green fingers. Its holdfast is a broad, spongelike cushion of tissue. The tips of segments are blunt and the surface is soft, so it is sometimes mistaken as sponge. Its body consists of interwovern, filamentous cells with incomplete crosswalls froming the inner part of the branches. The surface layer of the plant is often covered by other small epiphytic algae. Young species of codium fragile stand upright but then it droops as it gets longer. For large one, its length may exceed 30cm (Kam 2001).

INTRODUCTION AND DISTRIBUTION

• First record from the Baltic Sea (year, area, reference):

Year ­ In period from 1932 to 1938
Area - Kattegat and Belt Sea
Reference - Nikolaev 1951

• Established:

in the entire Baltic Sea ­ ?
in the area of primary introduction ­ Yes

• Origin of the species:

Indo-Pacific

• General characteristics:

Salinity range. C. fragile inhabits both estuarine and marine shores. For example, on N.W. Atlantic shores, the alga occurs in Long Island Sound, New York at salinities of 18–30 ppt and in Great South Bay, New York at salinities of 25–30 ppt. On Scottish and New Zealand shores, however, C. fragile occurs commonly in sea lochs and marine harbours and bays with salinities of 34–36 ppt (Trowbridge 1999).
Tolerance to pollution. C. fragile on N. Atlantic shores is nutrient-limited in summer, and nutrient-rich shores may be particularly vulnerable to the invasive alga. Field experiments manipulating nutrient levels in situ have never been conducted but observational evidence around the world does support this hypothesis. For example, persistent populations of C. fragile on Scottish shores are near sewage outfalls or other sources of nutrient enrichment. In Port Phillip Bay, Australia, it is common at Werribee, in close proximity to the sewage discharge (Trowbridge 1999).
Preferable substrate. C. fragile is common intertidally and subtidally attached to rocks, seawalls, piers and floating docks (Cohen, Carlton 1995). It is found both on the tops and sides of rocks and seems to prefer east-facing rocks (Tyson 1996).
Vulnarable (invasible) habitats. The tidal height at which a species lives is a function of the species’ tolerance to high and low temperature and dehydration. In geographic regions where intertidal organisms often freeze in the winter, C. fragile occurs primarily subtidally; in areas where freezing is unusual, the alga commonly forms dense intertidal stands. The species on British and Irish shores occurs in pools (all tidal levels) and on emergent rocky surfaces from mid intertidal to shallow subtidal habitats. On NW Atlantic shores, the alga is primarily subtidal, although there are several reports of the alga in high intertidal rock pools. In the last few years, it has expanded its distribution into the low intertidal zone on Maine and New Hampshire shores. On New Zealand shores, the introduced alga occurs in high pools, on emergent low intertidal shores, and in shallow subtidal areas (Trowbridge 1999).
Reproduction. Unlike many algae and other plants, Codium has only a gametophyte generation. The eggs and sperm are found in separate chambers called gametangia which project off the utricles. Most species of Codium are dioecious, with the male and female gametangia on separate plants. Each of the gametes has two flagella, and the female gametes are larger than the male gametes (Tyson 1996).

THE ROLE IN THE BALTIC SEA ECOSYSTEM

Competition for food and/or space. May cause the displacement of the native algal species. For example, on shores of S England and W Ireland, the alga is not considered a pest but has reputedly replaced the native congener C. tomentosum; whether this change was due to a competitive displacement or to a temporal replacement has never been investigated. Quantitative information on interspecific competition and inter-subspecific competition for C. fragile is meagre. There were some field studies on NW Atlantic shores, investigating the interactions between C. fragile and Zostera marina; was reported that the introduced alga is an inferior competitor. Other subtidal field experiments has shown that removals of C. fragile enabled red algal species to re-establish. Qualitative information, however, is common but must be considered cautiously (Eno et al. 1997; Trowbridge 1999; Pizzola 2003).
Habitat change. The main negative social effect is that the introduced alga grows profusely and fouls wharf pilings, jetties, ropes, and beaches thereby reducing the amenity associated with the use of coastal areas (Trowbridge 1999).
Food-prey for native species. As it was proved by experimental studies in other regions, C. fragile is being successfully consumed by grazers. In laboratory experiments held in Australia, herbivores were offered pairwise choices of the invasive alga C. fragile and the sympatric, native, encrusting congener C. convolutum. The generalist snail Cookia sulcata and sea urchin Evechinus chloroticus preferred the invasive alga whereas one of the ascoglossan sea slugs (P. dendritica) preferred the native species but the other had no preference. When grazers were offered pairwise choices of the invasive Feeding preferences were not related to herbivore size, diet breadth, life history, or geographical range, and differences in algal structural morphology were not clearly related to herbivore choice. Field observations and an algal transplant experiment indicated that intertidal herbivores exerted little grazing pressure on C. fragile. Results of such studies suggest that the introduced alga may successfully invade new habitats despite the diverse herbivore fauna (Trowbridge 1993; Trowbridge 1999).
Accumulation of toxic substances. A green marine sea-grass Codium fragile, which grows abundantly on numerous varieties of coastal substrates may enable scentists to draw precise mapping of pollutions according to metallic compounds concentration into its tissues. It accumulates heavy metals within its thallus: the lower, older parts of thallus contain substantially more metals than the distal branch tips Thye species also accumulates metals (copper, cadmium, and lead). The extent to which heavy metals accumulated in the algal thalli are transferred to grazers and humans that consume the alga has not been explored (Cristiani 1979; Trowbridge 1999).

LIKELY IMPACT ON USES/RESOURCES AND HUMAN HEALTH

Aquaculture. In different parts of the species’ broad geographic range, C. fragile is consumed by humans, used as invertebrate food by the mariculture industry, is a pest of natural and cultivated shellfish beds, and is a source of bioactive compounds (Trowbridge 1999; WGITMO 2001).
Fisheries. The most detrimental effect of C. fragile is the fouling of shellfish beds. The parthenogenetic gametes of the alga settle on bivalves (oysters, clams, scallops, mussels – both wild and cultivated). There are several direct and direct effects of this attachment; these include:
• smothering mussels and scallops by preventing opening of the valves;
• lifting shellfish off the sea floor, resulting in their transport by waves and currents away from shellfish beds, and frequently resulting in the death of the shellfish when they are cast up on the shore as drift (hence, the alga is referred to as the “oyster thief”);
• reducing the biomass of oysters;
• increasing the drag on shellfish, resulting in their dislodgement from the sea floor;
• reducing shellfish mobility and increasing their susceptibility to predators;
• clogging scallop dredges and interfering with the collecting of clams;
• fouling nets of fin and squid fishers; and
• increased labour costs during harvesting and processing associated with the need to remove the alga from shellfish.
These deleterious effects are seemingly quite serious, but there is little quantitative information about the alga’s impact to critically evaluate its current “pest status”. There is a need for spatial and temporal information of Codium on different types of shellfish and shellfish beds as well as values for algal loads caught in scallop dredges and fin and squid fisheries nets (Trowbridge 1999).
Tourism. The accumulation of masses of C. fragile rotting on beaches of the NW Atlantic, Mediterranean, and New Zealand can produce unpleasant odours. Tractor-drawn harrows remove such algal debris from beaches in many areas of the world; such activity in itself is a serious disturbance (Trowbridge 1999). During the 60s Codium fragile enjoyed a period of expansion on the Marseilles coasts which caused massive accumulations on the beaches where it had to be eliminated mechanically (Ribera Siguan 2002). Although there are no quantitative data documenting the magnitude of the problem, the absence of data should not be interpreted as the lack of a nuisance.
Human health. Codium fragile contains chemicals, which may be of medical use (Wallentinus 2002).

REFERENCES

1. Cohen A. N., Carlton J. T. 1995. Nonindigenous aquatic species in a United States estuary: a case study of the biological invasions of the San Francisco Bay and Delta. A report for the United States fish and wildlife service, Washington D.C.: 275 p.
2. Cristiani G. 1979. Espices indicatrices de pollution littorale par les métaux lourds au débouché d’un émissaire urbain [Heavy metal pollution indicator species in the vicinity of an outfall discharging urban waste waters in a coastal area]. Vie Marine, 1: 38-51.
3. Eno N. C., Clark R. A., Sanderson W. G. (eds.) 1997. Non-native marine species in British waters: a review and directory. JNCC, Peterbourough: 152 p.
4. Kam Ph. 2001.Codium fragile the Race Rocks taxonomy. http://www.racerocks.com/racerock/eco/taxalab/philipk.htm
5. Nikolaev I.I. 1951. On new introductions in fauna and flora of the North and the Baltic Seas from distant areas [O novyh vselencach v faune i flore Severnogo morja i Baltici iz otdalennyh rajonov]. Zoologicheskij Zhurnal. 30: 556-561 (In Russian).
6. Pizzola P. 2003. Marine Life Information Network for Britain and Ireland - MarLIN. http://www.marlin.ac.uk
   /index2.htm?species/Codtom.htm
7. Ribera Siguan M.A. 2002. Review of non-native marine plants in the Mediterranean Sea. In: Leppakoski E., Gollasch S. and Olenin S.(eds), Invasive Aquatic species of Europe – distribution impacts and management. Kluwer Academic Publishers, Dordrecht, Boston, London: 291-310.
8. Trowbridge C.D. 1993. Interactions between an ascoglossan sea slug and its green algal host: Branch loss and role of epiphytes. Marine Ecology Progress Series, 101 (3): 263-272.
9. Trowbridge C.D. 1999. An assessment of the potential spread and options for control of the introduced green macroalga Codium fragile spp tometosoides on Australian shores. http://www.marine.csiro.au/crimp/Reports
   /Codium_DNRE_Rpt.pdf
10. Tyson K. 1996. Codium fragile. http://www.mbari.org/~conn/botany/greens/kathy/INDEX.HTM
11. Wallentinus I. 2002. Introduced marine algae and vascular plants in European aquatic environments. In: Leppakoski E., Gollasch S. and Olenin S.(eds), Invasive Aquatic species of Europe – distribution impacts and management. Kluwer Academic Publishers, Dordrecht, Boston, London: 27-52.
12. WGITMO 2001. Working group on introductions and transfers of marine organisms. Report. 2001. International Council for the Exploration of the Sea. Barcelona, Spain: 100 p.