Why New England’s amphipods are turning into the scuttling undead
February 14, 2018 4:54 AM   Subscribe

The drama playing out in a New England estuary has all the makings of a Hollywood thriller: unwitting characters carrying out pleasant lives against a bucolic backdrop of branched waterways and rustling grasses when—suddenly!—they’re overtaken by a potent parasite. They turn pumpkin orange and wander away from shelter in zombie-like confusion. Eventually, they’re gobbled whole by winged monsters.

Johnson DS, Heard R. 2017. Bottom-up control of parasites. Ecosphere 8: e01885.
Parasitism is a fundamental ecological interaction. Yet we understand relatively little about the ecological role of parasites compared to the role of free-living organisms. Bottom-up theory predicts that resource enhancement will increase the abundance and biomass of free-living organisms. Similarly, parasite abundance and biomass should increase in an ecosystem with resource enhancement. We tested this hypothesis in a landscape-level experiment in which salt marshes (60,000 m2 each) received elevated nutrient concentrations via flooding tidal waters for 11 yr to mimic eutrophication. Nutrient enrichment elevated the densities of the talitrid amphipod, Orchestia grillus, and the density and biomass of its trematode parasite, Levinseniella byrdi. Strikingly, L. byrdi prevalence increased over time, up to 13 times higher in nutrient-enriched marshes (30%) relative to the mean prevalence in reference marshes (2.4%). The biomass density of infected amphipods was, on average, 11 times higher in nutrient-enriched marshes (1.1 kg/ha) than in reference marshes (0.1 kg/ha), when pooling across all years. Orchestia grillus biomass comprises 67% of the arthropod community biomass; thus, nutrient enrichment elicits a substantial surge in parasitized biomass in the arthropod community. If our results are typical, they suggest that eutrophication can increase parasite abundance and biomass with chronic resource enhancement. Therefore, minimizing aquatic nutrient pollution may prevent outbreaks of parasites with aquatic hosts.
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"The Plum Island Ecosystems Long Term Ecological Research site (PIE LTER) located in northeastern Massachusetts is an integrated research, education and outreach program with the goal of developing a predictive understanding of the long-term response of watershed and estuarine ecosystems to changes in climate, land use and sea level and to apply this knowledge to the wise management and development of policy to protect the natural resources of the coastal zone. PIE LTER research is focused in the estuary and watersheds of Plum Island Sound in northeastern Massachusetts. The estuary is fed by the Ipswich, Rowley and Parker Rivers with a combined drainage basin of 609 square kilometers. The Plum Island Sound estuary is a coastal plain, bar-built estuary with extensive areas of productive tidal marshes: the largest expanse of intertidal marsh in the Northeast." There are citizen science opportunities!

The TIDE project is long-term experimental ecology at the scale of the ecosystem and unique in the world. We use an ecosystem-level approach to understand the effects of eutrophication and altered food webs on saltmarsh ecosystems in the Plum Island Estuary, Massachusetts. We are unique because we are the only experiment in the world to maintain a long-term (8 years as of 2011), landscape-level (6 ha per plot) fertilization manipulation.
posted by ChuraChura (4 comments total) 7 users marked this as a favorite
 
I blame social media. If the amphipods would just put down their phones....
posted by GenjiandProust at 6:02 AM on February 14, 2018 [1 favorite]


More seriously, I’m fascinated by parasites and that narrowish line between symbiotes and parasites. We all have stuff living inside us, some of it helps us, some harms us, and, eventually, some may become us.
posted by GenjiandProust at 6:10 AM on February 14, 2018 [3 favorites]


narrowish line between symbiotes and parasites. We all have stuff living inside us, some of it helps us, some harms us, and, eventually, some may become us.

Yes -- it seems more and more that our categories of "commensalism," "mutualism," and "parasitism" are just arbitrary lines that organisms and ecosystems cross regularly --- here's recent(ish) work on oxpeckers, long used as a classroom example of mutualism but maybe not really; here's a quite recent paper that posits "pathogenicity (or virulence) should be viewed as a dynamical feature of an interaction between a host and microbes," that is, the relationship btwn organisms can be parasitical (or harmful) or not depending on ecological contexts, rather than the organism being categorized as a parasite (or pathogen) always.

"Parasites" could just be friends that hang out with you until specific conditions are reached, then they raid your bank account and eat you.

Although, I have to say, if you've ever been to Crane Beach near Plum Island in mid-summer, if science could do something about green-head flies it would make me pretty happy.
posted by PandaMomentum at 9:05 AM on February 14, 2018 [4 favorites]


Levinseniella byrdi has no effect on human health, but could be an analog for those parasites that do, says Johnson

Oh, don't worry, I'm sure there will be a little something left over for the humans.
posted by sneebler at 7:52 AM on February 15, 2018


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