TROPHIC INTERACTIONS IN THE SEA: AN ECOLOGICAL ROLE FOR CLIMATE RELEVANT VOLATILES?¹

Abstract

When attacked by herbivores, land plants can produce a variety of volatile compounds that attract carnivorous mutualists. Plants and carnivores can benefit from this symbiotic relationship, because the induced defensive interaction increases foraging success of the carnivores, while reducing the grazing pressure exerted by the herbivores on the plants. Here, we examine whether aquatic phytoplankton use volatile chemical cues in analogous tritrophic interactions. Marine algae produce several classes of biogenic gases such as non-methane hydrocarbons, organohalogens, ammonia and methylamines, and dimethylsulfide. The grazing-induced release of marine biogenic volatiles is poorly understood, however, and its effect on the chemical ecology of plankton and the foraging behavior of predators is essentially unknown. We outline grazing-induced defenses in algae and highlight the biogenic production of volatiles when phytoplankton are attacked by herbivores. The role of chemical signaling in marine ecology presents several possible avenues for future research, and we believe that progress in this area will result in better understanding of species competition, bloom development, and the structuring of food webs in the sea. This has further implications for biogeochemical cycles, because several key compounds are emitted that influence the chemistry of the atmosphere and global climate.

The use of algorithms to predict surface seawater dimethyl sulphide concentrations in the SE Pacific, a region of steep gradients in primary productivity, biomass and mixed layer depth

“…DMSP is known to be made by a range of micro and macroalgae as well as by a few higher plants (Stefels, 2000), yet the functions of DMSP and its metabolites may be numerous and remain controversial. It has been suggested to function as an osmolyte , a cryoprotectant (Karsten et al, 1996), a grazing deterrent (Wolfe et al, 1997;Steinke et al, 2002), as a viral defence (Evans et al, 2006), and as an antioxidant (Sunda et al, 2002), amongst other roles. It should be noted that while phytoplankton are the main source of DMSP, recent advances in understanding the DMS cycle indicate that it is the entire marine planktonic food web that determines net DMS production along with photochemical and photobiological processes.…”

Assessment and Characteristics of DMSP Lyase Activity in Seawater and Phytoplankton Cultures

“…Steinke et al (1998) reported that E. huxleyi CCMP 379 had nearly as high lyase activity as CCMP 373, yet this species was isolated in the English Channel where nutrients are relatively high and light penetration low. It is possible that certain phytoplankton maintain a high level of DLA in order to produce acrylate and DMS rapidly to deter grazing or to signal other organisms (Wolfe et al, 1997;Steinke et al, 2002c;Seymour et al, 2009). In addition, DMSP itself can deter grazing without the need for cleavage to the potentially toxic acrylic acid (Strom et al, 2003).…”

Annual cycle of dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) related to phytoplankton succession in the Southern North Sea

“…There are different sources of specific variability in DMSP and DMSO production including growth stage, salinity, temperature, nutrient limitation and light related to several potential physiological functions of these molecules as osmoregulator (Vairavamurthy et al, 1985), cryoprotectant (Kirst et al, 1991), antioxidant (Sunda et al, 2002), methyl donor , grazing deterrent (Wolfe et al, 1997) and overflow mechanism in nitrogen-limiting conditions (Stefels, 2000). DMSP is also a source of carbon (C) and S for heterotrophic organisms (Kiene and Linn, 2000a) and acts as a chemical cue for higher trophic level organisms (Steinke et al, 2002). These physiological functions are not necessarily exclusive (Harada and Kiene, 2011) and phytoplankton cells may use several of them.…”