Substrate roughness, fish grazers, and mesohabitat type interact to determine algal biomass and sediment accrual in a high-altitude subtropical stream

Schneck, Fabiana; Schwarzbold, Albano; Melo, Adriano S.

doi:10.1007/s10750-013-1477-x

Cited by 17 publications

(19 citation statements)

References 44 publications

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“…In our study, biomass (as Chl a) was higher in control ungrazed substrata, consistent with other studies (Giorgi and Tiraboschi, 1999;Álvarez and Peckarsky, 2005;Schneck et al, 2013). The initial Chl a concentration was similar between periphyton from different sources and changed drastically under higher light conditions when grazing was avoided (ungrazed treatment), thus suggesting a strong grazer's control of periphyton in grassland streams, in concordance with previous findings (Feminella and Hawkins, 1995;Hillebrand, 2005).…”

Section: Discussionsupporting

confidence: 93%

“…Herbivore control could be of greater importance in some systems (Hillebrand, 2005;Schneck et al, 2013). Several studies have shown that grazing in lotic ecosystems can substantially influence algal growth form thus controlling assemblage physiognomy Wellnitz and Ward, 1998;Álvarez and Peckarsky, 2005), and reducing biomass significantly (Wallace and Webster, 1996;Álvarez and Peckarsky, 2005;Barbee, 2005).…”

Section: Introductionmentioning

confidence: 99%

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Does grazing change algal communities from grassland and pine afforested streams?: A laboratory approach

et al. 2014

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a b s t r a c tDrastic changes in the composition and physiognomy of riparian vegetation, such as the conversion of grassland to forest, are expected to alter interactions among light availability, primary producers and herbivores. Our aim was to examine in laboratory the influence of a ubiquitous grazer on periphyton grown in a grassland unshaded stream (reference) vs. periphyton from a nearby pine afforested stream. Besides, we evaluated how the community responds to the removal of grazing. Given that grassland streams are exposed to higher light intensity and grazers are more abundant compared to afforested streams, we proposed that if biofilm grown in the afforested stream are dominated by grazing-vulnerable algal species, grazing pressure by Helicopsyche sp. should be stronger. In addition, if biofilm from the afforested stream has low quality or is less abundant as food for consumers, the effects of Helicopsyche sp. may be stronger or weaker depending on their feeding decisions. Helicopsyche sp. caused a decrease in richness and diversity in periphyton grown in the grassland stream and its net grazing effect on chlorophyll a (Chl a) was higher. Algal community composition from grassland stream was strongly changed after grazing, with a decrease in the proportion of overstory algae. In contrast, algal community structure of periphyton from the afforested stream was neither affected by grazing nor by grazing exclusion. Helicopsyche sp. produced significant changes in a short time in structural attributes of algal communities, mainly in periphyton from the grassland stream suggesting that herbivory, as a functional factor, is diminished following afforestation.

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Section: Discussionsupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Does grazing change algal communities from grassland and pine afforested streams?: A laboratory approach

et al. 2014

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“…The roughness provided by the crevices on the surface of the substrata was, therefore, responsible for the higher beta diversity among complex than among simplified substrata when species richness was accounted for. Indeed, the streambed in natural lotic systems is composed of various irregularities (Taniguchi & Tokeshi, ) that provide refuges against grazing and physical disturbances such as high‐discharge and desiccation events for periphytic algae (DeNicola & McIntire, ; Taniguchi & Tokeshi, ; Schneck, Schwarzbold & Melo, ; Tonetto et al ., , ). Complex substrata provide suitable conditions to a large set of species and might favour the occurrence of stochasticity in colonisation/establishment history.…”

Section: Discussionmentioning

confidence: 99%

Substratum simplification reduces beta diversity of stream algal communities

2016

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Summary Reduced species richness with increased habitat simplification is a well‐known relationship in community ecology. However, habitat simplification can also lead to a reduction in beta diversity if the loss of species is not random. We tested the hypothesis that beta diversity of periphytic algae is lower among simple than among complex substrata. We conducted a field experiment using simple (smooth) and complex (rough) artificial substrata colonised by periphytic algae to calculate beta diversity among each substratum type. We initially estimated beta diversity using the Jaccard dissimilarity index and its turnover component. As species richness differed between substratum types, we also employed the Raup–Crick dissimilarity index that estimates beta diversity by resampling from the species pool. We also deconstructed the total dataset into three functional groups based on the position occupied by each species within the periphytic matrix (low‐profile, high‐profile and motile functional groups). Beta diversity estimated using both Jaccard dissimilarity and its turnover component was higher among simplified substrata for the all‐species dataset and for high‐profile and motile groups. However, after taking into account the differences in species richness between substratum types using the Raup–Crick index, beta diversity was higher among complex substrata than among simple ones for the total dataset and for the low‐profile group. We emphasise that differences in species richness must be considered for the quantification of beta diversity, because this might confound the dissimilarity identified and, consequently, lead to erroneous conclusions. The higher beta diversity among complex substrata might be the result of priority effects, in which early colonists constrain the establishment of later arriving species, causing each patch to harbour a distinct species composition. Furthermore, algae life strategies may be an important driver of beta diversity among simple and among complex substrata, as periphytic algae position in the biofilm may affect their susceptibility to shear stress. On the one hand, stochasticity in colonisation history on complex substrata may have driven high beta diversity for the low‐profile group among this type of substratum. On the other hand, the reduced set of high‐profile and motile species on simple habitats may have driven these species to more occasional and rare occurrence, increasing beta diversity among this type of substratum and resulting in similar beta diversity among both types of substrata. Priority effects should be most frequent on complex substrata. However, only a reduced set of species might survive on simple substrata, occupying most of the available patches and causing beta diversity reduction.

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“…2B). Fish can be important removers of sediment from benthic surfaces, and thereby can enhance algal growth (Schneck et al 2013). The lack of physical disturbance by fish of sediments in the exclusion cages coupled with low current speeds (particularly at the US site; Table 2) may have increased AFDM enough to cover edible algae and inhibit their growth, further damping top-down effects.…”

Section: Discussionmentioning

confidence: 99%

Context dependency of top-down and bottom-up effects in a Northern Australian tropical river

2015

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Top-down and bottom-up forces (consumer and resource limitation, respectively) influence biomass of primary producers and primary consumers in natural food webs. Few investigators experimentally examine both in concert, especially in the tropics. Tropical systems probably are more sensitive than temperate systems to eutrophication and other disturbances, such as destruction of riparian canopy cover, because of wide windows of ecological opportunity. We experimentally examined the relative importance of top-down and bottom-up effects at 2 sites in the Edith River in the Australian wet-dry tropics during baseflow conditions. We used large fishexclusion cages to examine top-down effects of fish, and we used nutrient-diffusing substrates to manipulate bottom-up effects of nutrients. Macroinvertebrates were significantly more abundant in fish-exclusion cages than in open control areas at both sites. At 1 site, chlorophyll a on rock substrate was 1.5× greater and ash-free dry mass was 1.4× greater in fish-exclusion than in open cages. Chlorophyll a was >3× greater in the high-N and -P nutrient treatment than in the unamended control at both sites. Top-down effects on the algae on nutrientdiffusing substrates were detected at only 1 site. Bottom-up factors seem to be relatively more important in controlling primary producer biomass compared to top-down factors, with no evidence of a trophic cascade. Bottomup and top-down effects on macroinvertebrates were strong and consistent, whereas top-down effects on algae were context dependent and varied depending on benthic habitat, current speeds, and community structure. These results indicated spatial variation at the scale of tens of meters.

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Substrate roughness, fish grazers, and mesohabitat type interact to determine algal biomass and sediment accrual in a high-altitude subtropical stream

Cited by 17 publications

References 44 publications

Does grazing change algal communities from grassland and pine afforested streams?: A laboratory approach

Does grazing change algal communities from grassland and pine afforested streams?: A laboratory approach

Substratum simplification reduces beta diversity of stream algal communities

Context dependency of top-down and bottom-up effects in a Northern Australian tropical river

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