Parasites can have strong impacts but are thought to contribute little biomass to ecosystems. We quantified the biomass of free-living and parasitic species in three estuaries on the Pacific coast of California and Baja California. Here we show that parasites have substantial biomass in these ecosystems. We found that parasite biomass exceeded that of top predators. The biomass of trematodes was particularly high, being comparable to that of the abundant birds, fishes, burrowing shrimps and polychaetes. Trophically transmitted parasites and parasitic castrators subsumed more biomass than did other parasitic functional groups. The extended phenotype biomass controlled by parasitic castrators sometimes exceeded that of their uninfected hosts. The annual production of free-swimming trematode transmission stages was greater than the combined biomass of all quantified parasites and was also greater than bird biomass. This biomass and productivity of parasites implies a profound role for infectious processes in these estuaries.

Ecosystem energetic implications of parasite and free-living biomass in three estuaries

Ecology of sea lice parasitic on farmed and wild fish

Global warming can affect the world's biota and the functioning of ecosystems in many indirect ways. Recent evidence indicates that climate change can alter the geographical distribution of parasitic diseases, with potentially drastic consequences for their hosts. It is also possible that warmer conditions could promote the transmission of parasites and raise their local abundance. Here I have compiled experimental data on the effect of temperature on the emergence of infective stages (cercariae) of trematode parasites from their snail intermediate hosts. Temperature-mediated changes in cercarial output varied widely among trematode species, from small reductions to 200-fold increases in response to a 10 degrees C rise in temperature, with a geometric mean suggesting an almost 8-fold increase. Overall, the observed temperature-mediated increases in cercarial output are much more substantial than those expected from basic physiological processes, for which 2- to 3-fold increases are normally seen. Some of the most extreme increases in cercarial output may be artefacts of the methods used in the original studies; however, exclusion of these extreme values has little impact on the preceding conclusion. Across both species values and phylogenetically independent contrasts, neither the magnitude of the initial cercarial output nor the shell size of the snail host correlated with the relative increase in cercarial production mediated by rising temperature. In contrast, the latitude from which the snail-trematode association originated correlated negatively with temperature-mediated increases in cercarial production: within the 20 degrees to 55 degrees latitude range, trematodes from lower latitudes showed more pronounced temperature-driven increases in cercarial output than those from higher latitudes. These results suggest that the small increases in air and water temperature forecast by many climate models will not only influence the geographical distribution of some diseases, but may also promote the proliferation of their infective stages in many ecosystems.

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Global warming and temperature-mediated increases in cercarial emergence in trematode parasites.

Where possible, automation has been a common response of humankind to many activities that have to be repeated numerous times. The routine identification of specimens of previously described species has many of the characteristics of other activities that have been automated, and poses a major constraint on studies in many areas of both pure and applied biology. In this paper, we consider some of the reasons why automated species identification has not become widely employed, and whether it is a realistic option, addressing the notions that it is too difficult, too threatening, too different or too costly. Although recognizing that there are some very real technical obstacles yet to be overcome, we argue that progress in the development of automated species identification is extremely encouraging that such an approach has the potential to make a valuable contribution to reducing the burden of routine identifications. Vision and enterprise are perhaps more limiting at present than practical constraints on what might possibly be achieved.

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Automated species identification: why not?

Causes and effects of a highly successful marine invasion: Case-study of the introduced Pacific oyster Crassostrea gigas in continental NW European estuaries

Wave-swept shores are valuable for developing and testing key ecological principles. A synthesis of research is nonetheless missing a critical component: the chemosensory basis for behavioral interactions that determine population- and community-wide attributes. Chemical signaling environments on wave-swept shores, given their intense, turbulent mixing and complex topographies, would be difficult or impossible to simulate in a laboratory setting. For this reason, appropriately scaled field studies are needed to advance understanding of chemical stimuli and their biotic effects. Here, we performed a field investigation to establish the relative roles of dissolved and contact cues in predation by whelks (Acanthinucella spirata) on barnacles (Balanus glandula), their preferred prey. Experiments tested responses of whelks to seawater drawn above dense prey patches (10,240–12,180 barnacles m−2) and also over adjacent sand flats (no prey present). There was no evidence of waterborne stimuli associated w...

Chemical Ecology of Wave-Swept Shores: the Primacy of Contact Cues in Predation by Whelks.

Life in the lee: Local distributions and orientations of honeycomb worms along the California coast

Foundation species provide critical resources to ecological community members and are major determinants of biodiversity. One such species, the California mussel Mytilus californianus, is a superior competitor and dominates space on rocky, wave-swept shores (northeast Pacific Ocean). Live mussels secrete a 29.6 kDa glycoprotein (named 'KEYSTONEin'), with expression localized in epidermis, extrapallial fluid, and periostracum (organic shell coating). Hence, KEY-STONEin is available for contact recognition as predators crawl on rocky surfaces. Purple sea stars Pisaster ochraceus, whelks (Nucella emarginata and Acanthinucella spirata), and lined-shore crabs Pachygrapsus crassipes are common intertidal carnivores. Spanning 3 phyla and differing substantially in sensory mechanisms and hunting techniques, all are major mussel consumers. Here, we constructed faux prey to mimic both physical and chemical properties of mussels. Purified KEYSTONEin was presented at a typical mussel concentration. All 4 predatory species attacked, and ate, KEYSTONEin-infused faux prey as opposed to the organic enrichment or seawater controls. Sea stars, whelks (both species), and crabs also did not distinguish between KEY-STONEin-laced mimics and their live, intact counterparts. Mechanisms of chemical recognition thus have converged across phylogenetically diverse taxa to promote the exploitation of a valuable, shared, prey resource. By providing critical sensory information, KEYSTONEin drives mussel predation and initiates trophic cascades that shape community structure and function. KEY-STONEin is necessary and sufficient as a predatory cue of considerable ecological consequence.

KEYSTONEin: A glycoprotein cue drives predation on mussels and structures rocky intertidal communities

Author Posting. © The Authors, 2008. This article is posted here by permission of Sears Foundation for Marine Research for personal use, not for redistribution. The definitive version was published in Journal of Marine Research 66 (2008): 275-297, doi:10.1357/002224008785837167.

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Larval settlement in flocculated particulates

Larval supply, settlement (24 h), and recruitment were measured simultaneously with flow and flocculated particulates (flocs) in a muddy, coastal embayment. Fortuitous observations indicated that flocs drifting above the bed touched down at slack tide. Unexpectedly, results showed that larval supply did not portend settlement for the two most abundant polychaetes, Mediomastus ambiseta (resident mud dweller) and Sabellaria vulgaris (nonresident sand dweller). Both variables fluctuated widely and were decoupled. Colonization of mud vs. sand trays was not significantly different, also due to high variances. A statistical power analysis indicated that resolving selectivity would require 45 (median) paired, replicate treatments. Time series of near-bed planktonic larvae showed sizeable and sporadic spikes. Even 24-h means failed to predict settlement. Sabellaria was numerous in zooplankton pump collections, rare in trays, and nonexistent in ambient sediments. In contrast, Mediomastus was absent from pump samples, but dominated mud trays and bottom cores. Floc contents, however, lend insight into these distributions. Densities (of order 105 m−3) of Sabellaria and Mediomastus in flocs greatly exceeded those in tray and pump samples (of order 103 m−3). Located between the water column and seafloor, organic-rich flocs may offer transient larvae food, shelter, transport, and perusal of settlement sites. When aggregates touch down, entrained Mediomastus might exit upon contact with suitable ambient sediments, whereas nonresident Sabellaria remain suspended. Flocs may thus play a critical role in shaping connectivity and structuring species distributions.

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Cheryl Ann Zimmer

Papers

Chemical Ecology of Wave-Swept Shores: the Primacy of Contact Cues in Predation by Whelks.

Life in the lee: Local distributions and orientations of honeycomb worms along the California coast

KEYSTONEin: A glycoprotein cue drives predation on mussels and structures rocky intertidal communities

Larval settlement in flocculated particulates

Flocs, flows, and mechanisms decoupling larval supply from settlement