Desiccation tolerance of the introduced marine green alga Codium fragile ssp. tomentosoides – clues for likely transport vectors?

Abstract

The invasive marine green macroalga Codium fragile ssp. tomentosoides is now considered to be an introduced marine pest along the northwest Atlantic and southern Australian coasts. International or domestic translocation of C. fragile ssp. tomentosoides is usually attributed to the fouling of ship hulls or shellfish, particularly oysters. A likely domestic vector is shipboard transport, involving the translocation of whole thalli or fragments entangled in fishing nets, ropes, etc. that are then released in a previously unaffected area. Here we investigated the survival of C. fragile ssp. tomentosoides under emersed conditions, simulating shipboard transport. C. fragile ssp. tomentosoides was able to survive periods of emersion of up to 90 days in high relative air humidity. Net photosynthesis remained positive at about 50% of the rates of submersed control thalli. After 2 days of emersion and 4 days of rehydration under submersed conditions thalli recover to their initial net photosynthesis rates. Hence, C. fragile ssp. tomentosoides is likely to survive long shipboard journeys entrapped in fishing nets, anchor wells or other protected, high-humidity areas of a vessel. Furthermore, C. fragile ssp. tomentosoides may survive emersion on an exposed deck during short trips, especially in cooler conditions such as at night. The incursion sites of C. fragile ssp. tomentosoides in Australia are generally in modified environments, often associated with shipping-related infrastructure such as wharves, jetties, rip rap, and moorings.

Responses of Germlings to Acute Environmental Stress

“…In comparison to other stresses, germlings were more vulnerable to desiccation at a relative humidity of 80%, which is consistent with our previous study [13]. In contrast, small thallus pieces of Codium fragile (green alga) can survive long periods of emersion (90 days) when kept under high relative air humidity of 90% [20]. We suggest that desiccation tolerance is related to relative humidity.…”

Species boundaries and phylogenetic relationships within the green algal genus Codium (Bryopsidales) based on plastid DNA sequences

“…The dispersal stages of Codium include motile flagellated cells, which account for local dispersal, and mature thallus fragments, which are responsible for long-distance dispersal (Carlton and Scanlon, 1985; and references therein). Thallus fragments float because of oxygen bubble formation and can withstand fairly long periods of desiccation, increasing chances of successful dispersal by rafting (Schaffelke and Deane, 2005). The question of dispersal is particularly important with respect to C. fragile ssp.…”

Spatial and temporal variation in DMSP content in the invasive seaweed Codium fragile ssp. fragile: effects of temperature, light and grazing

“…tomentosoides, Provan et al 2008; Codium fragile hereafter), and investigate the role of environmental factors that may contribute to this variation through their influence on resource availability and the alga's requirements for DMSP's putative functions. The success of C. fragile as an introduced and invasive species has often been attributed to traits that may be linked to its production of DMSP: it flourishes under a wide range of environmental conditions, is tolerant of physiological stresses, and is undesirable for many generalist herbivores (Trowbridge 1998, Schaffelke & Deane 2005. Here, we examine patterns in DMSP content in C. fragile at different sites, and depths within sites, in the rocky subtidal zone (and intertidal zone at one site) on the Atlantic coast of Nova Scotia, between 2004 and 2009.…”