ResearchArticle DMSPinmarinemacroalgaeandmacroinvertebrates: Distribution,function,andecologicalimpacts KathrynL.VanAlstyne * andMelanyP.Puglisi Shannon Point Marine Center, Western Washington University, 1900 Shannon Point Road, Anacortes, WA 98221, USA Received: 9 June 2006; revised manuscript accepted: 4 April 2007 Abstract. The production of dimethylsulfoniopropio- nate (DMSP) and its cleavage products are well studied in phytoplankton. However, less is known about their sources, distributions, functions, and impacts in other marine organisms. We examined the distribution of DMSP in benthic macroalgae and macroinvertebrates geographically and taxonomical- ly. In macroalgae, concentrations significantly in- creased from the tropics to the poles in the northern, but not the southern, hemisphere. The increase in the northern hemisphere was due to an increase in concentrations with latitude in the Chlorophyta. This pattern was generated by a relatively high proportion of species in the order Ulvales (median [DMSP]: 145 mmolg –1 drymass(DM))athigherlatitudes,andahigh proportion of species in the orders Caulerpales and Siphonocladales (median [DMSP]: below detection level for both orders) in the tropics. Low DMSP concentrations (< 10 mmol g –1 DM) were reported from all red and brown macroalgae, except Polysi- phonia and Halopytis. In macroalgae, some of the reportedfunctionsofDMSPanditscleavageproducts included acting as a compatible solute, an anti- herbivore defense, a reactive oxygen scavenger, and a cryoprotectant. Among macroinvertebrates, DMSP occurredinhigherconcentrationsincnidariansthanin sponges and molluscs. Concentrations in animals harboring endosymbiotic algae were 6.5 times higher than animals without symbionts. This and direct measurements of DMSP from isolated symbionts suggest that endosymbionts are a major source of DMSP for some macroinvertebrates. Diet may be a source of DMSP in animals that lack endosymbionts. The functions and impacts of DMSP in invertebrates are not well known. Key words. Biogeography; community interactions; phenotypic plasticity; physiological ecology; taxonomic distribution. Introduction Early work on the sulphonium compound dimethyl- sulfoniopropionate(DMSP)focusedonitsoccurrence in benthic marine macroalgae. DMSP was first described as a precursor of dimethylsulfide (DMS) in the red macroalga, Polysiphonia fastigiata (Chal- lenger and Simpson, 1948). The DMSP cleavage pathway that generates DMS and acrylic acid was later described in a green macroalga, Ulva (previously Enteromorpha) intestinalis (Bywood and Challenger, 1953). In 1956, an enzyme that could catalyze this reaction, termed DMSP lyase, was identified from a * Corresponding author phone: 1-(360) 293-2188; fax: 1-(360) 293-1083; email: kathy.vanalstyne@wwu.edu Published Online First: August 8, 2007 Aquat. Sci. 69 (2007) 394 – 402 1015-1621/07/030394-9 DOI 10.1007/s00027-007-0888-z #Eawag, Dübendorf 2007 Aquatic Sciences