Add chemicals or minerals to sediments to remove or neutralise pollutants

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
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How is the evidence assessed?

Effectiveness

40%
Certainty

20%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Marine sediments can accumulate pollutants over time, such as those leaching from aquaculture systems, sewage outfalls, or nearby agriculture fields, and negatively affect subtidal benthic invertebrates. Chemicals or minerals can be added to sediments to reduce or remove pollutants within the sediments (Shin & Kim 2016; Yamamoto et al. 2013). For example, granulated coal ash can be used with the aim of reducing concentrations of phosphates and hydrogen sulphide (Kim et al. 2014). This may reduce pollution levels in the sediment at the treated area and allow subtidal benthic invertebrate communities to recover over time (Kim et al. 2014).

_{Kim K., Hibino T., Yamamoto T., Hayakawa S., Mito Y., Nakamoto K. & Lee I.C. (2014) Field experiments on remediation of coastal sediments using granulated coal ash. Marine Pollution Bulletin, 83, 132–137.}

_{Shin W. & Kim Y.K. (2016) Stabilization of heavy metal contaminated marine sediments with red mud and apatite composite. Journal of Soils and Sediments, 16, 726–735.}

_{Yamamoto, T., Harada, K., Kim, K.H., Asaoka, S., & Yoshioka, I. (2013) Suppression of phosphate release from coastal sediments using granulated coal ash. Estuarine, Coastal and Shelf Science, 116, 41–49.}

Study locations

Key messages

Two studies examined the effects of adding chemicals or minerals to sediments to remove or neutralise pollutants on subtidal benthic invertebrate populations. Both studies evaluated the use of coal ash in Hiroshima Bay (Japan).

COMMUNITY RESPONSE (1 STUDY)

Overall richness/diversity (1 study): One controlled, before-and-after study in Hiroshima Bay found that adding coal ash increased invertebrate species richness in winter but not summer compared to untreated sites.

POPULATION RESPONSE (2 STUDIES)

Overall abundance (2 studies): One controlled, before-and-after study in Hiroshima Bay found that adding coal ash increased invertebrate abundance in winter but not summer compared to untreated sites. One controlled study in Hiroshima Bay found that one of two types of coal ash increased combined invertebrate and fish abundance, but not biomass.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A controlled, before-and-after study in 2008–2010 in one area of soft seabed in Hiroshima Bay, Japan (Kim et al. 2014) found that adding coal ash to sediments to remove phosphate and hydrogen sulphide appeared to result in more species and individual invertebrates compared to before treatment and to adjacent untreated sites, during winter but not summer. However, results were not statistically tested. In winter, species richness increased (post-treatment: 17–22; pre-treatment: 8; untreated: 0–11/sample), and invertebrate abundance increased (post-treatment: 3,345–3,859; pre-treatment: 42; untreated: 0–507/m²). In summer, species richness and invertebrate abundance were similar in post-treatment sites (species: 3–7/sample; abundance: 49–944/m²), pre-treatment sites (species: 2 /sample; abundance: 204/m²), and untreated sites (species: 0–6/sample; abundance: 0–261/m²). Annually between August 2008 and August 2012 (except 2009), two sites were sampled once in winter and once in summer (one sample/site/time point). In May 2010, coal ash was scattered onto the sediment at one site to a depth of 10 cm; the other site was untreated. At the treated site, sediment samples were collected using a 25 x 25 cm quadrat to a depth of 10 cm. At the untreated site, sediment samples were collected using a sediment grab (dimensions unspecified). Invertebrates (> 1 mm) were identified and counted.
Study and other actions tested
Referenced paper
Kim K., Hibino T., Yamamoto T., Hayakawa S., Mito Y., Nakamoto K. & Lee I. (2014) Field experiments on remediation of coastal sediments using granulated coal ash. Marine Pollution Bulletin, 83, 132-137.
A controlled study in 2008–2011 in one area of soft seabed in Hiroshima Bay, Japan (Yamamoto et al. 2015) found that adding coal ash to sediments to remove hydrogen sulphide increased combined invertebrate and fish abundance compared to untreated sediments in one of two comparisons, but did not change overall biomass over three years. Abundance at the site treated with Osaki coal ash was greater (41–496 individual/quadrat) than at the untreated site (14–281). The site treated with Onoda coal ash had similar abundance (29–262) to the untreated site. Combined invertebrate and fish biomass at the treated sites were similar (Osaki: 0.3–8.5 unit unspecified; Onoda: 0.3–9) to that of the untreated site (untreated: 0.6–13). In October 2008, two sites (75 x 50 m; 80 m apart) were treated with one of two types of coal ash (Onoda or Osaki; see study for details) to a depth of 20 cm and a third site (50 m away) was not treated. Every three months between February 2009 and November 2011, three sediment samples were collected at each site using a 25 x 25 cm quadrat to a depth of 20 cm. Both invertebrates and fish (>1 mm) were identified, counted, and weighed.
Study and other actions tested
Referenced paper
Yamamoto T., Harada K., Kim K.H., Asaoka S. & Yoshioka I. (2015) A pilot study on remediation of sediments enriched by oyster farming wastes using granulated coal ash. Marine Pollution Bulletin, 90, 54-59.

Please cite as:

Lemasson, A.J., Pettit, L.R., Smith, R.K. & Sutherland, W.J. (2020) Subtidal Benthic Invertebrate Conservation. Pages 635-732 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Subtidal Benthic Invertebrate Conservation

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Add chemicals or minerals to sediments to remove or neutralise pollutants Action Link	Unknown effectiveness (limited evidence)	2	Synopsis Link
Establish pollution emergency plans Action Link	No evidence found (no assessment)	0	Synopsis Link