High-marsh invertebrates are susceptible to eutrophication

Johnson, David Samuel

doi:10.3354/meps09306

Cited by 23 publications

(27 citation statements)

References 26 publications

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“…The most striking response is the nutrient-induced destabilization of the creek-bank habitat (the zone of tall S. alterniflora), leading to marsh loss as a result of decreased belowground production and increased microbial respiration of organic matter (Deegan et al 2012). Additionally, we have seen strong bottom-up stimulation of the food web, including invertebrates , Johnson 2011, Johnson and Short 2013 and nekton (Deegan et al 2007, Lockfield et al 2013, most likely related to increases in benthic algae .…”

Section: Discussionmentioning

confidence: 86%

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Saltmarsh plant responses to eutrophication

Johnson¹,

Warren

Deegan

et al. 2016

Ecological Applications

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Abstract. In saltmarsh plant communities, bottom-up pressure from nutrient enrichment is predicted to increase productivity, alter community structure, decrease biodiversity, and alter ecosystem functioning. Previous work supporting these predictions has been based largely on short-term, plot-level (e.g., 1-300 m 2 ) studies, which may miss landscape-level phenomena that drive ecosystem-level responses. We implemented an ecosystem-scale, nine-year nutrient experiment to examine how saltmarsh plants respond to simulated conditions of coastal eutrophication. Our study differed from previous saltmarsh enrichment studies in that we applied realistic concentrations of nitrate (70-100 μM NO 3 − ), the most common form of coastal nutrient enrichment, via tidal water at the ecosystem scale (~60,000 m 2 creeksheds). Our enrichments added a total of 1,700 kg N·creek −1 ·yr −1 , which increased N loading 10-fold vs. reference creeks (low-marsh, 171 g N·m −2 ·yr −1 ; high-marsh, 19 g N·m −2 ·yr −1 ). Nutrients increased the shoot mass and height of low marsh, tall Spartina alterniflora; however, declines in stem density resulted in no consistent increase in aboveground biomass. High-marsh plants S. patens and stunted S. alterniflora did not respond consistently to enrichment. Nutrient enrichment did not shift community structure, contrary to the prediction of nutrient-driven dominance of S. alterniflora and Distichlis spicata over S. patens. Our mild responses may differ from the results of previous studies for a number of reasons. First, the limited response of the high marsh may be explained by loading rates orders of magnitude lower than previous work. Low loading rates in the high marsh reflect infrequent inundation, arguing that inundation patterns must be considered when predicting responses to estuarine eutrophication. Additionally, we applied nitrate instead of the typically used ammonium, which is energetically favored over nitrate for plant uptake. Thus, the form of nitrogen enrichment used, not just N-load, may be important in predicting plant responses. Overall, our results suggest that when coastal eutrophication is dominated by nitrate and delivered via flooding tidal water, aboveground saltmarsh plant responses may be limited despite moderate-to-high water-column N concentrations. Furthermore, we argue that the methodological limitations of nutrient studies must be considered when using results to inform management decisions about wetlands.

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Section: Discussionmentioning

confidence: 86%

“…Additionally, we have seen strong bottom‐up stimulation of the food web, including invertebrates (Johnson et al. , Johnson , Johnson and Short ) and nekton (Deegan et al. , Lockfield et al.…”

Section: Discussionmentioning

confidence: 96%

Saltmarsh plant responses to eutrophication

Johnson¹,

Warren

Deegan

et al. 2016

Ecological Applications

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“…But an organism can be a specialist at one life stage but not another (Rudolf & Lafferty, ). For instance, Melampus has long been considered a generalist species (Hausman, ) because it has a broad diet (Thompson, ) and occupies multiple habitats (Fell et al., ; Johnson, ; Price, ; Russell‐Hunter, Apley, & Hunter, ; Spelke, Fell, & Helvenston, ; Vince et al., ). We demonstrate, however, that habitats other than S. patens are not interchangeable for young age classes in the U.S. northeast and Melampus may be an ontogenetic habitat specialist.…”

Section: Discussionmentioning

confidence: 99%

Sea level rise may increase extinction risk of a saltmarsh ontogenetic habitat specialist

Johnson¹,

Williams²

2017

Ecology and Evolution

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Specialist species are more vulnerable to environmental change than generalist species. For species with ontogenetic niche shifts, specialization may occur at a particular life stage making those stages more susceptible to environmental change. In the salt marshes in the northeast U.S., accelerated sea level rise is shifting vegetation patterns from flood‐intolerant species such as Spartina patens to the flood‐tolerant Spartina alterniflora. We tested the potential impact of this change on the coffee bean snail, Melampus bidentatus, a numerically dominant benthic invertebrate with an ontogenetic niche shift. From a survey of eight marshes throughout the northeast U.S., small snails were found primarily in S. patens habitats, and large snails were found primarily in stunted S. alterniflora habitats. When transplanted into stunted S. alterniflora, small snails suffered significantly higher mortality relative to those in S. patens habitats; adult snail survivorship was similar between habitats. Because other habitats were not interchangeable with S. patens for young snails, these results suggest that Melampus is an ontogenetic specialist where young snails are habitat specialists and adult snails are habitat generalists. Temperature was significantly higher and relative humidity significantly lower in stunted S. alterniflora than in S. patens. These data suggest that thermal and desiccation stress restricted young snails to S. patens habitat, which has high stem density and a layer of thatch that protects snails from environmental stress. Other authors predict that if salt marshes in the northeast U.S. are unable to migrate landward, sea level rise will eliminate S. patens habitats. We suggest that if a salt marsh loses its S. patens habitats, it will also lose its coffee bean snails. Our results demonstrate the need to consider individual life stages when determining a species’ vulnerability to global change.

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“…Biological interactions between nematodes, epistrate feeders and macrofauna could alter the community structure of some sensitive species or may directly influence keystone facilitator or foundation species (Bruno & Bertness, ), further inducing changes in nematode community composition. Nutrient enrichment in NEC stimulated algal grazing rates of some macrofaunal species (Johnson ; Johnson & Short ; Pascal et al . ) and meiofauna (Pascal et al .…”

Section: Discussionmentioning

confidence: 99%

“…). Increases in the abundance of epifauna (Johnson ; Johnson & Short ), and increases in per capita and population grazing rates by benthic invertebrates (Pascal & Fleeger ; Pascal et al . ) and nekton (Lockfield et al .…”

Section: Introductionmentioning

confidence: 99%

Long‐term nutrient enrichment alters nematode trophic structure and body size in a Spartina alterniflora salt marsh

Mitwally

Fleeger

2014

Marine Ecology

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The effects of long‐term experimental nutrient enrichment on nematode trophic guilds and morphometrics were examined in intertidal saltmarsh creeks of Plum Island Estuary, Massachusetts, USA. Nematodes from the marsh‐edge Spartina alterniflora habitat in a reference creek (n = 3300) were sampled annually and compared with nematodes (n = 3100) from a creek in which nitrate and phosphate loading rates were increased approximately 10–15× for 6 years. Trophic guilds in both creeks were dominated by epistrate (diatom) feeders and predators, and natural temporal variability across years was high. However, after 4 years of nutrient enrichment, a shift in the nutrient‐enriched creek was detected from a dominance of epistrate feeders to an increased proportion of predators, even though neither the benthic microalgae biomass nor the total density of nematodes was affected by fertilization. Nematodes also became longer, and longer relative to their diameter over time with nutrient enrichment because of the shift in trophic structure as short‐stout epistrate feeders were replaced with longer, more slender predators. These changes may have been directly related to nutrient enrichment effects on benthic algae or indirectly to the many other effects of enrichments on ecosystem structure or function. Our research indicates that nutrient enrichment alters the nematode community and this alternation may directly or indirectly affect the response of benthic algae to nutrient enrichment and as well as other ecosystem services.

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High-marsh invertebrates are susceptible to eutrophication

Cited by 23 publications

References 26 publications

Saltmarsh plant responses to eutrophication

Saltmarsh plant responses to eutrophication

Sea level rise may increase extinction risk of a saltmarsh ontogenetic habitat specialist

Long‐term nutrient enrichment alters nematode trophic structure and body size in a Spartina alterniflora salt marsh

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