Non-consumptive predator effects indirectly influence marine plant biomass and palatability

Abstract

Summary1. Predators can reduce herbivory and increase plant biomass by consuming herbivores, lowering individual herbivore feeding rates, or both. We tested whether the presence of predators increases plant quality by non-consumptively reducing grazing pressure and thereby weakening the strength of the induced response in plant chemical defences.2. We performed a 42-day outdoor mesocosm experiment in which the herbivorous amphipod Ampithoe longimana was cultured on the brown seaweed Sargassum filipendula in the presence and absence of olfactory cues of its principal fish predator, the pinfish Lagodon rhomboides. The presence of fish cues reduced per capita rates of amphipod grazing by nearly 50%. Over the span of the mesocosm experiment, this per capita reduction in feeding rate yielded at least a 40% lower growth rate of amphipod populations (i.e. r reduced from 1.01 to 0.61). The lower rates of amphipod grazing (overall or per capita) correlated with higher algal biomass. 3. We pursued a series of laboratory-based feeding choice assays with naı¨ve amphipods to determine tissue palatability and the plant traits that mediate feeding choices. Tissue from tanks without grazers was more palatable than tissue from tanks with grazers, a pattern of induced plant defences that has been documented previously. Surprisingly, however, plant tissue from tanks with grazers and fish cues was more palatable than tissue from tanks with grazers but without fish cues. All changes in algal palatability were mediated by polar, but not lipophilic metabolites. These results suggest that the non-consumptive effects of fish predators increases the food quality of Sargassum by weakening the strength of its induced chemical defences. 4. Synthesis. The smell of predators has the potential to regulate herbivore populations and affect the ecological dynamics of plant biomass and chemical defences.

Effects of Trophic Skewing of Species Richness on Ecosystem Functioning in a Diverse Marine Community

“…Mesocosms were covered with 5 cm opening Vexar mesh lids and were placed in water tables to maintain constant temperature. Light, temperature and salinity within the mesocosms closely approximated field conditions in the nearby Bogue Sound during the course of the experiments [45], [89]. Mesocosms were rotated every 5 days to reduce positioning artifacts.…”

Macrofauna associated with the brown algae Dictyota spp. (Phaeophyceae, Dictyotaceae) in the Sebastião Gomes Reef and Abrolhos Archipelago, Bahia, Brazil

“…ͳͳ Epifaunal abundance can be affected by fish predation and, by regulating the presence of mesograzers, invertivore fishes may even play a role in macroalgae performance (Moksnes et al, 2008;Pérez-Matus and Shima, 2010;Reynolds and Sotka, 2011). Dictyota is known as a chemically-defended seaweed against fishes (Hay, Duffy et al, 1987;, which turns it into a good choice of habitat for mesograzers (Christie et al, 2003(Christie et al, , 2009Duffy and Hay, 1991;Hay, 1997).…”

Multiple predator species alter prey behavior, population growth, and a trophic cascade in a model estuarine food web

“…Screens were prepared using either freeze-dried, ground D. menstrualis or the highly palatable Ulva linza mixed with agar and spread over pieces of window screen 5 squares 3 6 squares in size (for detailed methods and recipe, see Reynolds and Sotka [2011]). Here, however, each tank housed one cup with and one without A. longimana, and cups received feeding screens with reconstituted rather than fresh algal tissue.…”