Potential of submerged macrophytes to support food webs in lowland agricultural streams

Abstract

Submerged plants are often abundant in lowland streams in agricultural landscapes, but little is known of their role in stream ecosystems compared to riparian vegetation.We investigated the relative importance of submerged macrophytes as a basal resource of food webs in stream reaches with good and poor riparian vegetation condition, using mixing model analysis with stable carbon and nitrogen isotopes.Epilithic periphyton and terrestrial detritus were important basal resources in good condition reaches, although where macrophytes were present, they did contribute to food webs. Higher assimilation of either the macrophyte Cycnogeton huegelii or conspicuous epiphytes on C. huegelii leaves was associated with poor riparian condition. Where Potamogeton ochreatus and Ottelia ovalifolia occurred in poor condition reaches, these macrophytes contributed moderately to the food web, but were probably of greater importance as substrates for epiphytic algae. Mixing models indicated invertebrates commonly had generalist feeding strategies, feeding on the most available resource at each reach. Thus where riparian vegetation is limited, submerged macrophytes may support opportunistic consumers both directly and as a substrate for epiphytes, thereby partially compensating for the loss of allochthonous resources in lowland agricultural streams.

Omnivory and stability in freshwater habitats: Does theory match reality?

“…Communities subject to a variety of both natural (Pringle & Hamazaki, ; Pusey, Arthington, Stewart‐Koster, Kennard, & Read, ; Reid, Lake, & Quinn, ) and anthropogenic (Cross et al., ; Layer, Hildrew, Monteith, & Woodward, ; Paice, Chambers, & Robson, ) disturbances show high levels of omnivory, which allows the community to persist in a variable environment. Pringle & Hamazaki () showed that removal of the omnivorous fish caused more variable dynamics in algal populations after severe storms, while Cross et al.…”

Spatial and seasonal variability in the trophic role of aquatic insects: An assessment of functional feeding group applicability

“…SD and SEM values are exhibited in Supporting Information Table S4 opportunistic feeding were widespread (e.g. Blanchette et al, 2014;Paice et al, 2016). Furthermore, our study showed that dissimilarities among the diet of each taxon at each site were not explained by the availability of trophic resources.…”

“…Studies that combined different approaches such as stable isotope and gut content analyses also show considerable dietary variation within taxa among sites, and concluded that omnivory and opportunistic feeding were widespread (e.g. Blanchette et al., ; Paice et al., ). Furthermore, our study showed that dissimilarities among the diet of each taxon at each site were not explained by the availability of trophic resources.…”

“…Local differences in resource availability are also likely to determine the FFG to which a given taxon is assigned, as demonstrated by several studies (e.g. Blanchette, Davis, Jardine, & Pearson, 2014;Hynes, 1976;López-Rodríguez, Tierno de Figueroa, & Alba-Tercedor, 2008;López-Rodríguez et al, 2009;Paice, Chambers, & Robson, 2016;Stewart & Stark, 2002).…”

Macrophytes in tropical shallow lakes: An important food item to benthic entomofauna or an underused resource?

“…In M+, Tanypus specimens could explore a higher percentage of animal items, which could be indicative of the trophic complexity found in this ecosystem. The presence of macrophytes in lakes can provide a great amount of resources to sustain complex food webs and long food chains (Ziegler et al ; Pace et al ). In contrast, in M−, Tanypus feeding was rather limited, with a greater affinity for Closterium , which was the only item consumed most of the time.…”