Do submerged aquatic plants influence their periphyton to enhance the growth and reproduction of invertebrate mutualists?

Abstract

It has been suggested that submerged aquatic plants can influence the nutritional quality of the periphyton which grows on their surfaces, making it more nutritious for grazing invertebrates, particularly snails. In return, these grazers might preferentially feed on the periphyton and clear the plants of a potential competitor, with the plants and grazers both gaining from this mutualistic relationship. A highly replicated experiment was conducted, in which the nature of the plant (isoetid and elodeid types compared with similar-shaped inert substrata), the nutrient loading, and the influence of periphyton grazers (the bladder snail, Physa fontinalis) of similar size and history were controlled. Plant growth and survival significantly increased in the presence of the periphyton grazer. Whilst the presence of the grazers had the largest influence on periphyton abundance, nutrient availability and plant type also had effects. Plant type had little influence on the nutritional quality of the periphyton measured as carbohydrate, protein and C:N. Effects of treatment on snail growth, and the timing and extent of snail reproduction disappeared when they were compared with the quantity of periphyton available. There was no evidence of enhanced grazer success in the presence of the live plants compared with inert substrata. Although submerged plants affect the growth and reproduction of the grazers which feed on their surfaces, through differences in the amount of periphyton which grows there, we found no evidence that they manipulate the periphyton to encourage such grazers.

Diel activity cycles of freshwater gastropods under natural light: Patterns and ecological implications

“…Because macrophytes are central to sustained water transparency in shallow-water, nutrient-rich habitats (e.g., Scheffer, 1998), heavy periphyton grazers with diurnal habits may effectively contribute to stabilize a macrophyte-dominated clear-water state even in otherwise phytoplankton-favoring nutrient-rich habitats. Physid commonness, high effectiveness as periphyton grazers (Jones et al, 1999;Lombardo, 2001), and highly active (feeding) behavior (this study), suggest that P. acuta may indeed play a keystone role in macrophytebased littoral food webs, as suggested by Lombardo (2001), and more so than other snail species with similar diurnal habits.…”

“…Physids in particular are capable of exerting top-down control of epi/periphyton even in the presence of strong bottom-up forces (high nutrient concentrations: Jones et al, 1999;Lombardo, 2001). High grazing rates suggest that snails may play a major role in shallow-water habitats, maintaining or promoting high water clarity in eutrophic waters by enhancing macrophyte well-being through continuous removal of competing epiphyton (Bro¨nmark and Weisner, 1992;Lombardo, 2005).…”

Allelopathic activity of Elodea canadensis and Elodea nuttallii against epiphytes and phytoplankton

“…Previous observations already indicated a negative relationship between Elodea and algae or cyanobacteria. Hasler and Jones (1949) reported lower phytoplankton densities in the presence of www.elsevier.com/locate/aquabot Aquatic Botany 85 (2006) 203-211 E. canadensis, and both E. canadensis and E. nuttallii were less covered with epiphytes than other submersed macrophytes (Wium-Andersen, 1987;Jones et al, 1999;Gross et al, 2003b). Our research revealed that Elodea might be chemically defended against insect herbivores (Erhard, unpublished results), and waterweeds may also produce secondary metabolites that inhibit the growth of co-occurring primary producers.…”

The habitat type and trophic state determine benthic macroinvertebrate communities in lowland shallow lakes of China

“…Generally, macrophytes can provide habitats and foods for aquatic animals, which can increase spatial heterogeneity and allow more species of various ecological niches to coexist in a macrophytedominated lake (Padial et al, 2009;Bazzanti et al, 2010;Robinson and Doering, 2013). In addition, macrophytes provide more surface area for attachment by periphytons, which are a major component in the diet of macroinvertebrates (Jones et al, 1999;Cai et al, 2011). Our findings showed that scrapers had the highest abundance in the macrophyte-dominated regions (Fig.…”