Compensation of nutrient pollution by herbivores in seagrass meadows

McSkimming, Chloe; Tanner, Jason E.; Russell, Bayden D.; Connell, Sean D.

doi:10.1016/j.jembe.2015.05.018

Cited by 32 publications

(23 citation statements)

References 47 publications

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“…Using well‐established methods (McSkimming et al. ), we wrapped varying weights of fertilizer (Osmocote Pro, Scotts, Australia) in nylon mesh bags and secured them at substrate level with plastic stakes (see Supporting Information for translation of fertilizer weight to DIN concentrations in the field). Plots were separated by a minimum of 2.0 m to ensure independence of enrichment, based on a previous field‐trial that showed background concentrations occurred within at least 0.5 m of such bags of Osmocote (Scotts, Australia).…”

Section: Methodsmentioning

confidence: 99%

Testing for thresholds of ecosystem collapse in seagrass meadows

Connell

Fernandes

Burnell

et al. 2017

Conservation Biology

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Although the public desire for healthy environments is clear-cut, the science and management of ecosystem health has not been as simple. Ecological systems can be dynamic and can shift abruptly from one ecosystem state to another. Such unpredictable shifts result when ecological thresholds are crossed; that is, small cumulative increases in an environmental stressor drive a much greater change than could be predicted from linear effects, suggesting an unforeseen tipping point is crossed. In coastal waters, broad-scale seagrass loss often occurs as a sudden event associated with human-driven nutrient enrichment (eutrophication). We tested whether the response of seagrass ecosystems to coastal nutrient enrichment is subject to a threshold effect. We exposed seagrass plots to different levels of nutrient enrichment (dissolved inorganic nitrogen) for 10 months and measured net production. Seagrass response exhibited a threshold pattern when nutrient enrichment exceeded moderate levels: there was an abrupt and large shift from positive to negative net leaf production (from approximately 0.04 leaf production to 0.02 leaf loss per day). Epiphyte load also increased as nutrient enrichment increased, which may have driven the shift in leaf production. Inadvertently crossing such thresholds, as can occur through ineffective management of land-derived inputs such as wastewater and stormwater runoff along urbanized coasts, may account for the widely observed sudden loss of seagrass meadows. Identification of tipping points may improve not only adaptive-management monitoring that seeks to avoid threshold effects, but also restoration approaches in systems that have crossed them.

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Section: Methodsmentioning

confidence: 99%

Testing for thresholds of ecosystem collapse in seagrass meadows

Connell

Fernandes

Burnell

et al. 2017

Conservation Biology

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“…), or through greater per‐capita consumption (Russell & Connell ; McSkimming et al . ). Increased nutrient availability may promote a rise in per‐capita consumption through a quantitative ( i.e .…”

Section: Introductionmentioning

confidence: 97%

“…) and resource availability in the system (Russell & Connell ; Jaschinski & Sommer ; McSkimming et al . ), determine grazing intensity on epiphytes in seagrass ecosystems. The experimental fieldwork of Philippart () showed significant reductions in epiphyte biomass on Zostera noltii leaves under increased densities of the gastropod Hydrobia ulvae , similar to the results found in aquaria with Zostera marina by Hootsmans & Vermaat ().…”

Section: Introductionmentioning

confidence: 99%

“…Consumer pressure on epiphyte biomass depends on several factors. Grazer and epiphyte species abundance and composition (Nicotri 1980;Arrontes 1990;Jaschinski et al 2010), which are highly seasonal (Antoli e 1985; Gambi et al 1992;Peirano et al 2001;Prado et al 2008;, along with hydrodynamics (Schanz et al 2002) and resource availability in the system (Russell & Connell 2007;McSkimming et al 2015), determine grazing intensity on epiphytes in seagrass ecosystems. The experimental fieldwork of Philippart (1995) showed significant reductions in epiphyte biomass on Zostera noltii leaves under increased densities of the gastropod Hydrobia ulvae, similar to the results found in aquaria with Zostera marina by Hootsmans & Vermaat (1985).…”

Section: Introductionmentioning

confidence: 99%

“…A nutrient-driven increase in food resources may promote grazing pressure by two mechanisms: through an increase in the number of individuals feeding on meadows with high numbers of epiphytes (i.e. population growth effect, ; aggregation response effect, Moksnes et al 2008; Castej on-Silvo et al 2012b), or through greater per-capita consumption (Russell & Connell 2007;McSkimming et al 2015). Increased nutrient availability may promote a rise in per-capita consumption through a quantitative (i.e.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Experimental assessment ofPosidonia oceanica‐associated gastropods grazing on an early‐successional biofilm community: nutrient availability and species‐specific effects

Castejón‐Silvo

Terrados

2016

Marine Ecology

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Although grazing is considered an essential process controlling epiphyte biomass on seagrass leaves, there is still a lack of fundamental knowledge about the species‐specific consumption rates of the most common grazers in Mediterranean meadows. This study experimentally assessed the effect of Posidonia oceanica‐associated gastropod grazing on early successional biofilm and the species‐specific relationship between biofilm consumption rates and biofilm biomass. Two biofilms on artificial substrata, both developed in situ (in a P. oceanica meadow), one under ambient conditions and the other under nutrient‐enriched conditions, were offered in aquaria assays to nine species of grazers found in P. oceanica meadows. Biofilm consumption rates and their association with biofilm biomass were assessed. It was found that: (i) there was a positive association between biofilm consumption and biofilm biomass up to 20 mg Chl a·m−2 for Bittium reticulatum, Gibbula ardens, Jujubinus exasperatus and Tricolia pullus; (ii) Alvania montagui, B. reticulatum and Jujubinus striatus showed the highest consumption rates and are thus expected to be amongst the leading consumers in early‐successional epiphytic communities; (iii) there was not an increase of consumption rate when a substratum colonized under nutrient‐enriched conditions was offered to any of the nine studied species. This study provides species‐specific consumption rates knowledge that is useful for the assessment of the strength of grazer–epiphyte interactions and trophic fluxes in P. oceanica meadows.

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While shoot herbivores reduce, root herbivores increase nutrient enrichment’s impact on diversity in a grassland model

Crawford

Schlägel

Wurst

et al. 2021

Ecology

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Nutrient enrichment is widespread throughout grassland systems and expected to increase during the Anthropocene. Trophic interactions, like aboveground herbivory, have been shown to mitigate its effect on plant diversity. Belowground herbivory may also impact these habitats' response to nutrient enrichment, but its influence is much less understood, and likely to depend on factors such as the herbivores' preference for dominant species and the symmetry of belowground competition. If preferential toward the dominant, fastest growing species, root herbivores may reduce these species' relative fitness and support diversity during nutrient enrichment. However, as plant competition belowground is commonly considered to be symmetric, root herbivores may be less impactful than shoot herbivores because they do not reduce any competitive asymmetry between the dominant and subordinate plants. To better understand this system, we used an established, two-layer, grassland community model to run a full-factorially designed simulation experiment, crossing the complete removal of aboveground herbivores and belowground herbivores with nutrient enrichment. After 100 yr of simulation, we analyzed communities' diversity, competition on the individual level, as well as their resistance and recovery. The model reproduced both observed general effects of nutrient enrichment in grasslands and the short-term trends of specific experiments. We found that belowground herbivores exacerbate the negative influence of nutrient enrichment on Shannon diversity within our model grasslands, while aboveground herbivores mitigate its effect. Indeed, data on individuals' above-and belowground resource uptake reveals that root herbivory reduces resource limitation belowground. As with nutrient enrichment, this shifts competition aboveground. Since shoot competition is asymmetric, with larger, taller individuals gathering disproportionate resources compared to their smaller, shorter counterparts, this shift promotes the exclusion of the smallest species. While increasing the root herbivores' preferences toward dominant species lessens their negative impact, at best they are only mildly advantageous, and they do very little reduce the negative consequences of nutrient enrichment. Because our model's belowground competition is symmetric, we hypothesize that root herbivores may be beneficial when root competition is asymmetric. Future research into belowground herbivory should account for the nature of competition belowground to better understand the herbivores' true influence.

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Compensation of nutrient pollution by herbivores in seagrass meadows

Cited by 32 publications

References 47 publications

Testing for thresholds of ecosystem collapse in seagrass meadows

Testing for thresholds of ecosystem collapse in seagrass meadows

Experimental assessment ofPosidonia oceanica‐associated gastropods grazing on an early‐successional biofilm community: nutrient availability and species‐specific effects

While shoot herbivores reduce, root herbivores increase nutrient enrichment’s impact on diversity in a grassland model

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