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We measured concentrations of dimethylsulfoniopropionate (DMSP) in Spartina alterniflora (Loisel.) in response to the plant hormones abscisic acid (ABA), jasmonic acid (JA), and salicylic acid (SA) to determine whether DMSP concentration is linked to any of their signaling pathways. DMSP concentrations were also measured in plants at a salt marsh dieback site in Georgetown County, South Carolina (USA), to determine whether dieback conditions affect foliar DMSP concentrations. We found elevated levels of DMSP in plants receiving SA treatment compared to a control treatment, but we found no treatment effect for either of the other 2 hormone treatments. This suggests that DMSP production or transformation is linked to the SA signaling pathway. Diminished levels of DMSP were observed in plants nearest the dieback edge compared to those farthest from the dieback in an apparently healthy marsh, which suggests that DMSP concentration responds to environmental conditions connected with salt marsh dieback. Using a ring assay, we found that Littoraria irrorata snails, potential herbivores of S. alterniflora, were attracted to DMSP. However, we found no correlation between DMSP concentration and L. irrorata density at the acute dieback site. These results suggest that factors such as plant biomass may play a more important role than DMSP in determining L. irrorata distribution in dieback areas. KEY WORDS: Stress hormone · Attractant · Deterrent · Salt marsh dieback Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 406: [47][48][49][50][51][52][53][54][55] 2010 more frequently by rice rats Oryzomys palustris compared to plants in unfertilized plots. They observed that the rats had chewed through the sheath of the stem in order to reach the younger shoots inside. Upon further analysis, the investigators found that the inner tissue of the stems that the rice rats were probably trying to reach contained a much lower concentration of DMSP than the same tissue from the unfertilized plants ( Otte et al. 2004). These observations, along with others (Dacey & Wakeham 1986, Nakajima 1989, Wolfe & Steinke 1996, Wolfe et al. 1997, Van Alstyne & Houser 2003, suggest that DMSP may act as an herbivore deterrent. Attractant properties of DMSP have also been observed. Van Alstyne et al. (2001) demonstrated that DMSP can act as a feeding attractant for the purple sea urchin Strongylocentrotus purpuratus and the green sea urchin Strongylocentrotus droebachiensis. DMSP is also a foraging cue for certain species of planktivorous reef fishes (DeBose et al. 2008). DMSP released during algal grazing by zooplankton allows fishes to 'eavesdrop on trophic interactions' (DeBose et al. 2008) by recognizing that the presence of residual DMSP is an indication of prey presence. In a similar way, DMSP produced by S. alterniflora or ephiphytic algae growing on S. alterniflora and marsh substrate may act as a foraging or orientation cue for herbivores, enabling them to identify potential food or re...

Abstract. Marine species with planktonic larvae often have high spatial and temporal variation in recruitment that leads to subsequent variation in the ecology of benthic adults. Using a combination of published and unpublished data, we compared the population structure of the salt marsh snail, Littoraria irrorata, between the South Atlantic Bight and the Gulf Coast of the United States to infer geographic differences in recruitment and to test the hypothesis that the Deepwater Horizon oil spill led to widespread recruitment failure of L. irrorata in Louisiana in 2010. Size-frequency distributions in both ecoregions were bimodal, with troughs in the distributions consistent with a transition from sub-adults to adults at~13 mm in shell length as reported in the literature; however, adult snails reached larger sizes in the Gulf Coast. The ratio of sub-adults to adults was 1.5-2 times greater in the South Atlantic Bight than the Gulf Coast, consistent with higher recruitment rates in the South Atlantic Bight. Higher recruitment rates in the South Atlantic Bight could contribute to higher snail densities and reduced adult growth in this region. The ratio of sub-adults to adults in Louisiana was lower in 2011 than in previous years, and began to recover in 2012-2014, consistent with widespread recruitment failure in 2010, when large expanses of spilled oil were present in coastal waters. Our results reveal an important difference in the ecology of a key salt marsh invertebrate between the two ecoregions, and also suggest that the Deepwater Horizon oil spill may have caused widespread recruitment failure in this species and perhaps others with similar planktonic larval stages.

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