Contemporary Trends in the Acid–Base Status of Two Acid-Sensitive Streams in Western Maryland

Eshleman, Keith N.; Kline, Kathleen M.; Morgan, Raymond P.; Castro, Nancy M.; Negley, Timothy L.

doi:10.1021/es071195e

Cited by 11 publications

(10 citation statements)

References 30 publications

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“…Decreasing trends in surface-water acidity are consistent with results from several previous studies showing chemical recovery from acidification across Europe and North America (Stoddard et al 1999, Eshleman et al 2008). However, despite widespread evidence of chemical recovery, support for biological recovery has been patchy, and the environmental variables driving or delaying recovery have been difficult to ascertain.…”

Section: Discussionsupporting

confidence: 90%

Tracing recovery under changing climate: response of phytoplankton and invertebrate assemblages to decreased acidification

Johnson

Angeler

2010

Journal of the North American Benthological Society

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Section: Discussionsupporting

confidence: 90%

Tracing recovery under changing climate: response of phytoplankton and invertebrate assemblages to decreased acidification

Johnson

Angeler

2010

Journal of the North American Benthological Society

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“…The magnitude of chemical recovery from acidification across Europe and North America is increasingly being established (Stoddard et al 1999;Evans et al 2001;Davies et al 2005;Eshleman et al 2008). In the UK Acid Waters Monitoring Network (AWMN), H + concentrations declined significantly during 1988-2002 at around one-third of the 22 sites typically Table 5.…”

Section: Discussionmentioning

confidence: 99%

Restoration and recovery from acidification in upland Welsh streams over 25 years

Ormerod

Durance

2009

Journal of Applied Ecology

103

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Summary 1.Streams affected by acid deposition should now be recovering biologically, but long-term assessments are scarce. Here, we use the experimental catchments at Llyn Brianne (Wales, UK) to evaluate trends over 25 years in the chemistry and macroinvertebrates of acid moorland and forest streams restored by liming relative to those responding 'naturally' to reduced deposition. 2. Mean H + concentrations in acid moorland streams fell by c . 15-16 μ quiv L − 1 over the study, increasing mean winter pH by 0·8-1·3 units to pH 5·6-6·1. Liming moorland streams in 1987 and 1988 increased mean pH to 5·5-6·4, but differences from naturally recovering streams diminished over 12-18 years. 3. In limed and acid moorland streams, changes in invertebrate composition were consistent with recovery, and near-identical. Four acid-sensitive species, from a local pool of 29, increased significantly in abundance or occurrence, but effects were too small to increase similarity with circumneutral reference streams. , but mean winter pH increased by only 0·4 units and remained too acid for invertebrate recovery (mean pH 4·8-5·2; Al > 0·3-0·6 mg L − 1 ). One forest stream limed in 1987 and 1988 remained at mean pH > 5·9 thereafter, but there was no invertebrate response. 5. Climate affected recovery pattern. After accounting for time trends, wet winters increased acidity in moorland and forest streams sufficiently to offset 21-41% of the total 25-year decrease in H + concentration. 6. Synthesis and applications . These data from one of the world's longest running experiments on acidification confirm that upland British streams are recovering, but ecological effects are marginal and vary with land use. Conifer forest streams at Llyn Brianne remain too acid for sensitive invertebrates, while moorland streams are still at risk from acid events. In this example, liming had few long-term benefits compared with natural recovery, and we suggest that this should be a key, general criterion in evaluating the outcomes of ecological restoration.

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“…Therefore, similar to Holmes et al (), we used LOADEST to model daily fluxes of DSi, BSi, DIP, and NOx, but not NH 4 + . LOADEST, a widely used program for calculating daily loads of material (Eshleman et al, ; Holmes et al, ; Phillips & Cowling, ; Stenback et al, ), is based on multiple regression equations from Cohn et al () and requires inputs of daily average discharge and spot samples ( n > 12) of constituent concentration. LOADEST calculates daily load estimates based on three models (adjusted maximum likelihood estimation (AMLE), maximum likelihood estimation, and least absolute deviation).…”

Section: Methodsmentioning

confidence: 99%

Arctic River Dissolved and Biogenic Silicon Exports—Current Conditions and Future Changes With Warming

Carey

Gewirtzman

Johnston

et al. 2020

Global Biogeochemical Cycles

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Silicon (Si) exports from terrestrial to marine systems can dictate phytoplankton species composition in Arctic coastal waters. Diatoms are often the dominant autotroph in Arctic waters, making Si an important control on Arctic marine primary productivity. Yet even as Arctic regions are among the fastest warming on Earth, we lack baseline knowledge on the magnitudes and controls of Arctic river Si exports. To address uncertainties in current and future Si behavior, we used a combination of field data and modeling to quantify daily yields of dissolved Si (DSi) and biogenic Si (BSi) from a 400 km space‐for‐time latitudinal gradient of seven basins across the boreal‐Arctic transition in Alaska (United States) over the course of 2 years (2015–2016). Mean annual DSi concentrations (33–149 μM) and yields (13–49 kmol km−2 year−1) were significantly and positively correlated with mean basin active layer depth, indicating that permafrost thaw will likely increase DSi fluxes to Arctic coastal waters. Conversely, BSi concentrations (7–16 μM) and yields (2.6–4.5 kmol km−2 year−1) were more uniform across the seven basins, indicating that warming may not substantially alter BSi loads to coastal systems in the near future. Our data also indicate that climatic warming will advance the timing of Si delivery to coastal waters in the spring, although the ratios of Si to nitrogen in Arctic river exports will likely remain steady. These results highlight the important role of basin hydrology, largely driven by permafrost extent, as a key driver of Si exchange at the land‐sea interface in the Arctic.

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Contemporary Trends in the Acid–Base Status of Two Acid-Sensitive Streams in Western Maryland

Cited by 11 publications

References 30 publications

Tracing recovery under changing climate: response of phytoplankton and invertebrate assemblages to decreased acidification

Tracing recovery under changing climate: response of phytoplankton and invertebrate assemblages to decreased acidification

Restoration and recovery from acidification in upland Welsh streams over 25 years

Arctic River Dissolved and Biogenic Silicon Exports—Current Conditions and Future Changes With Warming

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