marine organism-environment interaction
DMS from marine sources is a major contributor to geochemical sulfur cycling and global climate regulation. Consequently, considerable effort has gone into measuring and modeling its production and distribution in the marine environment, extending from local (prey patch size) to global spatial scales. It is arguably unprecedented to have such detailed information on the production and distribution of a biogenic scented compound, and these data have provided important insights into how seabirds and other marine organisms might use chemical information in foraging and navigation at both local and global spatial scales.
DMS is a byproduct of the metabolic decomposition of DMSP in marine phytoplankton and other marine algae (including zooxanthalae in coral reefs). DMS is frequently associated with oceanic features where phytoplankton are plentiful, including upwelling zones, seamounts and shelf breaks. These are areas where seabirds and other marine predators tend to aggregate and forage. DMSP tends to be released when phytoplankton cells are crushed and it is then rapidly converted to DMS via processes within the marine microbial food web. DMS emissions increase when phytoplankton are grazed by zooplankton, suggesting that local elevations in DMS may opportunistically alert higher order predators (including birds) to rapidly accumulating aggregations of zooplankton (e.g. krill) and zooplankton predators (fish and squid).
DMS and DMSP as signal molecules in marine trophic interactions: links to global climate regulation
We have studied how tube-nosed seabirds (petrels and albatrosses) use DMS and other associated cues for foraging and navigation. We showed early on that members of this order can detect DMS at concentrations of at least one million times lower than had previously been reported for any odor in birds. The view we have now is that, instead of a ‘featureless’ environment, these birds detect changes in the olfactory landscape to recognize potentially productive foraging opportunities as they fly over them. This odor landscape reflects bathymetric features, which tend to accumulate phytoplankton and therefore prey, and we speculate that birds build up a map of these features over time.
We have gone on to show that these sulfur compounds produced by phytoplankton and other forms of marine algae are more pervasive than we previously imagined. Recent work from our lab has shown, for example, that coral reef fishes also use DMS and its precursor DMSP as aggregation cues. This work has been extended by our lab and others to include harbor seals, penguins, whale sharks and bacteria.
How do marine birds and fishes forage and navigate over the seemingly featureless landscape of the open ocean? What cues do they use to find their way? My lab has pioneered research showing that biogeochemical regulators of climate, including dimethyl sulfide (DMS) and its precursor dimethylsulfoniopropionate (DMSP), also serve as signal molecules in marine habitat.
