Biological effects (micronucleus) of contaminants in fish
Results indicate that flatfish in the UK portions of the Greater North Sea and the Celtic Sea generally have near-background exposure to chemicals that can damage genetic information, although several near shore locations show increased exposure to such chemicals. These findings indicate that risks of fish suffering genetic damage from such chemicals are generally likely to be low.
Background
UK target on biological effects (micronucleus) in fish
This indicator is used to supplement the target covering the biological effects of contaminants set out in the Marine Strategy Part One (HM Government, 2012), which requires that for biological effects “the intensity of those biological or ecological effects due to contaminants agreed by OSPAR as appropriate for Marine Strategy Framework Directive purposes are below the toxicologically-based standards”. Whilst this indicator has not yet been agreed by OSPAR for Marine Strategy Framework Directive (European Commission, 2008) purposes, it provides valuable information on the exposure of fish to substances that cause damage to the genetic information of cells (genotoxins) and has therefore been included in the assessment of Good Environmental Status for Contaminants.
Key pressures and impacts
The key pressures associated with this indicator are the presence of genotoxic contaminants in the marine environment (such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls and some heavy metals) result in cytogenetic damage in exposed organisms, including flatfish. In the UK Initial Assessment (HM Government, 2012), the main anthropogenic pressures responsible for the presence of contaminants in the sea were identified as being point sources (for example, industrial and sewage discharges and emissions) and diffuse sources (such as agriculture, roads run-off, households, and atmospheric deposition). No significant new pressures have since been identified.
Measures taken to address the impacts
There is a robust UK legislative framework in place for controlling pollution from the main sources of contaminants (energy production, transport, urban and industrial uses) including appropriate consenting and River Basin Management Plans described in the Marine Strategy Part Three (HM Government, 2015). However, a lot of genetically-damaging chemicals entered the sea before many of the controls were put in place and, due to their persistence, are still present.
Monitoring, assessment and regional co-operation
The determination of micronucleus in fish is an OSPAR candidate indicator, as not all Contracting Parties currently include this in their monitoring programmes.
Areas that have been assessed
Status assessments were conducted for the UK biogeographic marine regions and aggregated to the UK portions of the Greater North Sea and the Celtic Seas Marine Strategy Framework Directive sub-regions.
Monitoring and assessment methods
Risk-based monitoring and assessment was conducted within the annual Clean Seas Environmental Monitoring Programme survey using methods and principles set out by the OSPAR Co-ordinated Environmental Monitoring Programme.
Assessment thresholds
OSPAR has developed species-specific Background Assessment Criteria to assess genetic damage in fish blood cells using the micronucleus assay. Below the Background Assessment Criteria, the effects are deemed to be at a background level and the organisms are not significantly exposed to contaminants that cause genetic damage. Currently, OSPAR has not developed an upper threshold for the micronucleus assay (Environmental Assessment Criteria) that indicates significant environmental harm.
Regional co-operation
The micronucleus assay was recommended by the OSPAR/ICES Study Group on Integrated Monitoring of Contaminants (ICES, 2011) and successfully used to assess the presence of contaminants that can cause genetic damage in the north-east Atlantic under the International Council for the Exploration of the Sea Integrated Contaminants Workshop.
Further information
Description of the indicator
Contaminants can enter the marine environment from natural sources and as a result of anthropogenic activities, either as direct inputs or via rivers, estuaries and the atmosphere. Pollution itself is considered to be the introduction of substances which have, or are likely to have, deleterious effects on the marine environment and its uses (United Nations Convention on the Law of the Sea – Part I). This includes effects that result in harm to the health of organisms, loss of biodiversity, are hazardous to human health, impair water quality, and reduce our ability to use the sea.
A number of anthropogenic and natural contaminants are known to be mutagenic or carcinogenic, that is they can cause genetic damage in significantly exposed organisms. These contaminants include some polycyclic aromatic hydrocarbons, metals (including cadmium, copper, mercury and zinc), flame retardants such as polybrominated diphenyl ethers, alkylphenols, phthalates, certain pesticides, pharmaceuticals and radionuclides.
The concentrations of several of these substances have long been monitored in flatfish as part of the UK’s marine monitoring programme. The additional use of biological effects monitoring allows an integrative measure of the impacts caused by the mixtures of contaminants found in the marine environment because it includes substances that can cause genetic damage (genotoxins) not included in the chemical monitoring programme. The UK has begun to monitor the genotoxic impacts of contaminants by determination of the incidence of micronuclei within red blood cells (erythrocytes) of flatfish collected as part of the routine annual monitoring surveys (Figure 1).
Figure 1. Collecting blood from plaice (Pleuronectes platessa).
Micronuclei are membrane-bound fragments of nuclear material, originating as acentric chromosome fragments or as whole chromosomes that did not migrate fully to the spindle poles during mitotic cell division (Fenech, 2000; Figure 2). The micronucleus assay, therefore, detects the effects of substances that cause clastogenic (disruption or breakage in chromosomes) or aneugenic (abnormal number of chromosomes) events. It was first developed as a screening test in the safety assessment of new pharmaceuticals (Heddle, 1972; Schmid, 1975; OECD, 1997). Whilst micronuclei can be determined in many cell types, fish erythrocytes provide a convenient and sensitive tissue for the assay. Exposure to genotoxic contaminants using the micronucleus assay has been reported for fish from marine and freshwaters around the world, including the Firth of Forth (Bombail and others, 2001), North Sea (Baršienė and others, 2004, 2013; Rybakovas and others, 2009), Baltic Sea (Baršienė and others, 2004, 2012b; Rybakovas and others, 2009), and Aegean Sea (Çakal Arslan and others, 2015). Furthermore, the frequency of micronucleated erythrocytes has been shown to be positively correlated to liver tumour formation in flatfish (Köhler and Ellesat, 2008) and micronucleus frequency in lymphocytes is predictive of increased risk of breast, pancreas and lung cancers in humans (Bonassi and others, 2010; Chang and others, 2011; Cardinale and others, 2012). Other nuclear abnormalities can be observed during the micronucleus assay, some of which are due to genotoxicity and are predictive of carcinogenicity whilst others indicate cytotoxicity (Rybakovas and others, 2009; Bonassi and others, 2010; Baršienė and others, 2013). This indicator assessment focuses on the frequency of micronucleated erythrocytes in flatfish as OSPAR has developed Background Assessment Criteria for this biomarker of genotoxic exposure.
Figure 2. Micronucleus in fish red blood cell (image is ca. 40 µm by 40 µm; photo: J. Baršienė)
UK target on biological effects
Within the UK, the Clean Seas Environmental Monitoring Programme is one way in which our national and international commitments to monitor marine biota in near-shore and offshore marine waters are met (Nicolaus and others, 2016). The main drivers for the current programme are the Co-ordinated Environmental Monitoring Programme and the OSPAR Joint Assessment and Monitoring Programme (OSPAR, 2014), together with the EU Marine Strategy Framework Directive (MSFD; European Commission, 2008) and Water Framework Directive (WFD; European Commission, 2000). Within the Clean Seas Environmental Monitoring Programme, the UK monitors contaminants and their biological effects in flatfish (mainly dab but including flounder and plaice) from British seas. This micronucleus in fish indicator is one of several used to inform progress against the target covering the biological effects of contaminants set out in the Marine Strategy Part One (HM Government, 2012). The micronucleus test gives a sensitive and integrated measure of exposure to genotoxic substances and has recently been introduced into the Clean Seas Environment Monitoring Programme monitoring of flatfish, providing information to inform progress towards this target. Monitoring and assessments in the Clean Seas Environment Monitoring Programme are done at the scale of the 8 UK biogeographical marine regions defined in the Charting Progress 2 report on the status of the seas (UKMMAS, 2010). Assessments have been aggregated to report on the UK portions of the Marine Strategy Framework Directive Greater North Sea and the Celtic Seas sub-regions.
The UK has also been active within OSPAR and the International Council for the Exploration of the Sea (ICES) to develop an integrated assessment framework for contaminants and their biological effects (Davies and Vethaak, 2012; OSPAR Commission, 2016; Vethaak and others, 2017), including an extensive practical workshop to test this at the Regional Seas scale (Hylland and others, 2017a, 2017b; Robinson and others, 2017; Vethaak and others, 2017).
Assessment method
Assessment scales
Monitoring of contaminants and their effects in flatfish is undertaken at fixed stations in estuarine, coastal and offshore waters. Data were assessed at the individual stations scale, and these were spatially aggregated to the level of the 8 UK marine biogeographical regions. Aggregation was based on data from sampling stations in representative coastal and offshore waters, rather than sites located at known impacted sites (estuarine sites do not fall within the scope of the Marine Strategy Framework Directive). The assessments of the 8 UK regions were used as the basis of expert opinion when assessing status at the scale of the UK waters within the two Marine Strategy Framework Directive sub-regions: Greater North Sea and Celtic Seas.
Assessment thresholds for micronucleus in flatfish
OSPAR Background Assessment Criteria for micronucleus frequency have been developed for flounder (Platichthys flesus) and dab (Limanda limanda) based on the empirical 90th percentile of observations from 5 or more reference stations (Table 1). Background Assessment Criteria were developed to test if observed results are near background levels. For most contaminants and biological effects, upper level Environmental Assessment Criteria have been developed by OSPAR and exceeding these indicates environmental harm. However, Environmental Assessment Criteria have not been derived for micronucleus in fish as this is a marker of exposure to genotoxins and not of harmful effect at the population-level. It is difficult to relate early stage responses such as micronucleus to subsequent responses such as tumour formation or to population-level effects. However, an association between micronucleus and tumours in flatfish has been observed (Köhler and Ellesat, 2008) and frequency of micronucleus in human lymphocytes is predictive of breast and lung cancers (Bonassi and others, 2010; Cardinale and others, 2012). In order to indicate the risk of genotoxic exposure for each site/region, this assessment is based upon the proportion of fish exceeding the Background Assessment Criteria, an approach adapted from Baršienė and others (2012b).
Table 1. OSPAR Background Assessment Criteria for the micronucleus assay in flatfish red blood cells; n.a. = not available.
|
Species |
Background Assessment Criteria (micronucleus per 1000 cells) |
|
Flounder |
0.3 |
|
Dab |
0.5 |
|
Plaice |
n.a. |
Assessment of micronucleus frequency in flatfish
The frequency of micronucleated erythrocytes (micronucleus per 1,000 cells) was determined in dab and flounder collected on annual Clean Seas Environment Monitoring Programme surveys. Following fish collection, a drop of blood from the caudal sinus was placed on an identification-coded microscope slide, air dried and fixed with methanol. Subsequently, cells were stained with 5% Giemsa in phosphate buffer (pH 6.8) for 15 to 30 minutes and microscopically examined (without knowledge of sampling information) for the presence of micronuclei at 1000 times magnification. Micronuclei were identified as round or oval membrane-bound bodies within the cytoplasm, of similar colour to the nucleus, but of less than approximately one-third of the nuclear diameter and completely separated from it (Carrasco and others, 1990; Fenech and others, 2003; Baršienė and others, 2006; 2012a). Quality assurance between UK analytical laboratories was ensured via staff training and sample swap ring trial.
Due to micronucleus having only recently been added to the UK monitoring programme, assessment of trends is not yet possible. The assessment at the 34 sites and of 6 UK biogeographical regions is based on the proportion of sampled fish with micronucleus frequency above the Background Assessment Criteria, categorised on a scale of 1 to 4 (adapted from Baršienė and others, 2012b) and then colour coded as indicated in Table 2. If the median frequency (50%) of micronucleus in fish at a site was above the Background Assessment Criteria, the site was classified as having above background levels of exposure to genotoxins and colour coded amber, otherwise the site was assessed as close-to-background.
Table 2. Thresholds used for the assessment for micronucleus frequency in flatfish red blood cells (adapted from Baršienė and others, 2012a).
|
Proportion of sampled fish above the Background Assessment Criteria |
Description of the level of exposure |
Colour coding* |
|
0 – 25% |
Negligible |
Blue |
|
26 – 50% |
Low |
Blue |
|
51 – 75% |
Moderate |
Amber |
|
76 – 100% |
High |
Amber |
Results
Findings in the 2012 UK Initial Assessment
No assessment was carried out in 2012.
Latest findings
Status assessment
The overall status of micronucleus frequency in the Greater North Sea can be described as being close to background (Figure 3). More than half of fish sampled at three of the 21 stations exceeded the Background Assessment Criteria for micronucleus frequency, indicating only localised areas of high exposure. Two of the UK biogeographical regions were classed as having Negligible or Low exposure to substances that cause genetic damage. Only 2 sampling sites are present in UK Region 3 (the Eastern Channel), meaning the assessment of this area is tentative.
Micronuclei frequency in the Celtic Seas was, at low levels overall, with all sites classed as having Negligible or Low exposure to substances that cause genetic damage. Only one sampling site is located in UK Region 6, making the assessment here tentative. No stations are located in Regions 7 or 8, preventing assessment of these areas, although potential exposure is expected to be lower here than elsewhere.
Figure 3. Micronucleus status assessment for the sampling locations and of the UK biogeographic regions. Blue = Negligible or Low genotoxic exposure, amber = Moderate, or High frequency of exposure to substances that can cause genetic damage. Hatched regions have insufficient data for a robust assessment and white regions lack data. Regions: 1 = Northern North Sea; 2 = Southern North Sea; 3 = Eastern Channel; 4 = Western Channel & Celtic Sea; 5 = Irish Sea; 6 = Minches & Western Scotland; 7 = Scottish Continental Sea; 8 = Atlantic North West Approaches.
Trend assessment
Data are only available for a maximum of 2 years at any one site, therefore it is not possible to determine if there are any significant trends.
Further information
The UK target for biological effects requires that the intensity of those biological or ecological effects due to contaminants agreed by OSPAR as appropriate for Marine Strategy Framework Directive purposes are below the toxicologically-based standards. Whilst the micronucleus assay and its associated toxicologically-based standards are not yet agreed by OSPAR, it is one of several biological effects indicators used to assess pollutant effects and can inform the overall assessment of contaminants.
Currently, there is no upper-threshold for the micronucleus assay to indicate if significant environmental harm has occurred to flatfish, and OSPAR has not defined an Environmental Assessment Criteria for use with this indicator. The findings below essentially indicate the degree of exposure to genotoxic substances and possible genotoxic risk using a scale modified from Barsiene and others (2012a).
The frequency of micronucleus incidence in red blood cells was determined in flatfish from 34 stations, including a range of near shore and open water locations (Figure 3 and Table 3). The Background Assessment Criteria was exceeded by more than 50% of sampled fish at 3 stations (~9%) and these were classified as having a Moderate level of genotoxic exposure, 21 stations (62%) had a Low level of exposure, and 10 stations (29%) had Negligible exposure to genotoxic substances. There was a Low level of genotoxic risk in each of the 4 biogeographic regions with 3 or more sampling stations. Two regions had insufficient data to allow a robust assessment: Region 6 (Minches and Western Scotland) is suggested to be of Negligible exposure on the basis of a single sampling station, whilst fish from Region 2 (Eastern Channel) are suggested to have a Moderate degree of genotoxic exposure with one site indicating a Moderate level of exposure and one a Low level of exposure to genotoxic substances. There are no data available for regions 7 and 8, to the northwest of Scotland. Samples have been collected for 2 stations in Region 7 (Scottish Continental Shelf) but have not yet been analysed.
Table 3. Micronuclei frequency in flatfish from each sampling station and for the 8 UK biogeographic marine regions. n= total number of fish analysed; SD = standard deviation; BAC = Background Assessment Criteria; risk rating based on criteria in Table 1.
|
Site |
Species |
n |
Mean |
SD |
Median |
% fish above BAC |
Risk rating |
|
Amble |
DAB |
16 |
0.63 |
0.81 |
0.00 |
43.8 |
Low |
|
St Andrews Bay |
FLOUNDER |
15 |
0.52 |
0.64 |
0.25 |
46.7 |
Low |
|
Balta |
DAB |
14 |
0.32 |
0.25 |
0.25 |
14.3 |
Negligible |
|
Farne |
DAB |
18 |
0.33 |
0.59 |
0.00 |
27.8 |
Low |
|
Intermediate Moray Firth |
DAB |
32 |
0.23 |
0.30 |
0.00 |
18.8 |
Negligible |
|
Kingston Hudds |
DAB |
9 |
0.78 |
0.63 |
0.75 |
66.7 |
Moderate |
|
Montrose Bank |
DAB |
29 |
0.17 |
0.28 |
0.00 |
6.9 |
Negligible |
|
Off Flamborough |
DAB |
19 |
0.68 |
0.95 |
0.00 |
47.4 |
Low |
|
Outer Moray Firth |
DAB |
32 |
0.16 |
0.23 |
0.00 |
6.3 |
Negligible |
|
SE Fair Isle (Fladen) |
DAB |
15 |
0.42 |
0.35 |
0.25 |
40.0 |
Low |
|
Tees Bay |
DAB |
17 |
0.71 |
0.92 |
0.00 |
47.1 |
Low |
|
NORTHERN NORTH SEA |
|
216 |
0.39 |
0.58 |
0.00 |
27.8 |
Low |
|
West Dogger |
DAB |
20 |
1.00 |
1.17 |
1.00 |
55.0 |
Moderate |
|
Central Dogger |
DAB |
20 |
0.45 |
0.76 |
0.00 |
35.0 |
Low |
|
Indefatigable Bank |
DAB |
20 |
0.30 |
0.73 |
0.00 |
20.0 |
Negligible |
|
North Dogger |
DAB |
20 |
0.40 |
0.94 |
0.00 |
25.0 |
Low |
|
NE Dogger |
DAB |
20 |
0.45 |
0.60 |
0.00 |
40.0 |
Low |
|
Off Humber |
DAB |
17 |
0.24 |
0.44 |
0.00 |
23.5 |
Low |
|
Outer Humber |
DAB |
19 |
0.32 |
0.58 |
0.00 |
26.3 |
Low |
|
Smiths Knoll Bank |
DAB |
17 |
0.65 |
1.06 |
0.00 |
41.2 |
Low |
|
SOUTHERN NORTH SEA |
|
153 |
0.48 |
0.84 |
0.00 |
33.3 |
Low |
|
Off Newhaven |
DAB |
19 |
0.53 |
0.61 |
0.00 |
47.4 |
Low |
|
Rye Bay |
DAB |
18 |
0.67 |
0.59 |
1.00 |
61.1 |
Moderate |
|
EASTERN CHANNEL |
|
37 |
0.59 |
0.60 |
1.00 |
54.1 |
Moderate |
|
Camarthen Bay |
DAB |
30 |
0.33 |
0.61 |
0.00 |
26.7 |
Low |
|
Celtic Deep |
DAB |
20 |
0.40 |
0.68 |
0.00 |
30.0 |
Low |
|
South of Eddystone |
DAB |
23 |
0.65 |
0.88 |
0.00 |
47.8 |
Low |
|
West Lundy |
DAB |
10 |
0.90 |
1.37 |
0.00 |
40.0 |
Low |
|
W. CHANNEL & CELTIC SEA |
|
83 |
0.51 |
0.83 |
0.00 |
34.9 |
Low |
|
Burbo Bight |
DAB |
19 |
0.47 |
0.70 |
0.00 |
36.8 |
Low |
|
Liverpool Bay Trend |
DAB |
30 |
0.57 |
0.97 |
0.00 |
33.3 |
Low |
|
Morecombe Bay |
DAB |
29 |
0.17 |
0.54 |
0.00 |
10.3 |
Negligible |
|
North Cardigan Bay |
DAB |
30 |
1.07 |
1.87 |
0.00 |
33.3 |
Low |
|
Red Wharf Bay |
DAB |
30 |
0.77 |
1.19 |
0.00 |
43.3 |
Low |
|
SE Isle of Man |
DAB |
29 |
0.59 |
1.09 |
0.00 |
34.5 |
Low |
|
South Cardigan Bay |
DAB |
30 |
1.67 |
2.28 |
0.00 |
46.7 |
Low |
|
St Bees Head |
DAB |
30 |
0.17 |
0.53 |
0.00 |
10.0 |
Negligible |
|
IRISH SEA |
|
227 |
0.70 |
1.38 |
0.00 |
30.8 |
Low |
|
North Minch |
DAB |
28 |
0.21 |
0.37 |
0.00 |
10.7 |
Negligible |
|
MINCHES & W. SCOTLAND |
|
28 |
0.21 |
0.37 |
0.00 |
10.7 |
Negligible |
Statistical analysis (Kruskall-Wallis ANOVA by ranks and Dunn’s post hoc test) revealed that sites at Kingston Hudds, Rye Bay, and West Dogger Bank had significantly higher levels of micronucleus incidence than Morecombe Bay or St Bees Head, whilst South Cardigan Bay had higher micronucleus incidence than Morecombe Bay (p < 0.05). Kingston Hudds, Rye Bay and West Dogger were also the only 3 sites with more than 50% of fish exceeding the Background Assessment Criteria for micronucleus and being classified as having Moderate exposure. Fish from Morecombe Bay and St Bees Head were classified as having Negligible exposure to genotoxins whilst those from South Cardigan Bay were classed having Low level exposure.
The Kingston Hudds site is located in the inner Firth of Forth, close to Edinburgh and the Forth estuary, which are known sources of contaminants. Sediment concentrations of several genotoxins (including some polycyclic aromatic hydrocarbons, mercury, lead, copper and zinc) are above their upper environmental assessment threshold at stations within the inner Firth of Forth and although concentrations of mercury are decreasing that is not the case for other contaminants.
Sediments from the Dogger Bank area are known to have above background concentrations of several contaminants (such as cadmium, lead and polycyclic aromatic hydrocarbons), which is reflected in above background exposure of fish, leading in some cases to significant exposure to polychlorinated biphenyls (CB118, for example, is above Environmental Assessment Criteria in selected samples). Additionally, liver neoplasms (such as tumours) are observed more frequently here.
The Rye Bay site is in the Eastern Channel, the busiest shipping lane in the world, and an area where sediments are known to have elevated concentrations of genotoxic metals (such as mercury, lead and copper) and polycyclic aromatic hydrocarbons (such as benzoperylene, benzo[a]anthracene). Nonetheless, fish from Rye Bay have a very low incidence of liver neoplasms.
Information on the assessment of contaminants at sampling sites is available at the online UK Marine Monitoring and Assessment Strategy data and assessment viewer tool.
Status of the Greater North Sea
The overall status of micronucleus frequency in the Greater North Sea can be described as Good. Approximately 86% of sites were classed as having Negligible or Low exposure to genotoxic substances, based on the proportion of fish exceeding the Background Assessment Criteria for the frequency of micronuclei in circulating erythrocytes of flatfish. Three of 21 sites (Rye Bay, West Dogger and Kingston Hudds) had a median micronucleus frequency above the Background Assessment Criteria. Impacted stations located close to known contaminant sources were excluded from the assessment. Therefore, while the assessment result represents the general situation, there may be issues with genotoxin exposure at localised sites, or in estuaries, where concentrations of genotoxic environmental contaminants may be higher, noting that the Marine Strategy Framework Directive does not apply to estuaries. As data are only available for 1 to 2 years, it is not possible to say whether there are any significant trends in this assessment.
Status of the Celtic Seas
Micronuclei frequency in the Celtic Seas was, overall, at low levels. Although there is limited or no data for significant parts of the Celtic Seas Marine Strategy Framework Directive sub-region, the locations in this sub-region with available micronucleus data are those with the highest legacy of contamination in sediments. Yet all sites were classed as having Negligible or Low exposure to genotoxic substances. Impacted stations located close to known contaminant sources were excluded from the assessment. Therefore, while the assessment result represents the general situation, there may be issues with genotoxin exposure at localised sites, or in estuaries, where concentrations of genotoxic environmental contaminants may be higher, noting that the Marine Strategy Framework Directive does not apply to estuaries.
Conclusions
At the scale of individual stations sampled and of UK assessment regions, assessment of the micronucleus level in flatfish red blood cells indicates a negligible or low risk of exposure to substances that can cause genetic damage. Less than half of sampled fish exceeded the Background Assessment Criteria for micronucleus. Overall, flatfish in the Celtic Seas sub-region were assessed as having a low level of exposure to substances that can cause genetic damage. Flatfish in the Greater North Sea were also assessed as having a low degree of exposure overall, although at 3 locations the median frequency exceeded the Background Assessment Criteria. Further data are required to allow determination of trends. There is a low level of confidence in this assessment as more detailed statistical modelling of the data is required, and additional sampling stations are needed in the Eastern Channel in order to further investigate the possible higher level of risk in this area.
Further information
At approximately 91% of sampling stations (31 of 34) flatfish were found to have negligible or low-level exposure to genotoxic substances. The median micronucleus frequency exceeded the Background Assessment Criteria at only 9% of stations. Of the UK marine regions, the Eastern Channel was the only one not of negligible or low risk, although there are only 2 sampling stations in this region. Overall, fish from both the Celtic Seas and the Greater North Sea sub-regions were assessed as having a low risk from exposure to genotoxic substances, with some locations of higher risk.
Further data are required to allow determination of trends. Data for trend analysis should be focussed on a limited number of both background and impacted sites. There is a low level of confidence in the status assessment for both Marine Strategy Framework Directive sub-regions. More detailed statistical modelling is required and additional sampling stations are needed (particularly in the Eastern Channel) in order to further investigate the possible higher level of risk observed in this area than elsewhere. If a higher level of risk is confirmed for the Eastern Channel, associated causes should be investigated.
Knowledge gaps
This assessment is based on 1 to 2 years of data and further monitoring is required to allow a robust trend assessment. For some UK biogeographic regions there are insufficient sampling stations to allow a robust assessment. Relatively few of the monitoring stations are from near-shore areas and including coastal fish and/or mussels would allow a more complete assessment
Development of Environmental Assessment Criteria is difficult for exposure indicators such as micronucleus. Whilst micronucleus frequency can be predictive of tumour formation in individuals, it’s significance at the population-level is unclear. The development of alternative approaches to assessing exposure biomarkers is required. Assessment Criteria are required for other monitored species (such as plaice).
Further information
Different numbers of cells were scored during analysis at Cefas (1,000 cells per fish) and Marine Science Scotland (4,000 cells per fish). A review of the incidence and power to detect micronucleus above the Background Assessment Criteria (dab = 0.5 micronucleus per 1,000 cells) should be undertaken to agree the number of cells to be scored.
This assessment is based on only 1 to 2 years of data and monitoring should be continued to allow for a trend assessment. To ensure that the current situation is not worsening (for example, from emissions of emerging contaminants such as pharmaceuticals or nanoparticles) monitoring should include stations currently classed as being of low risk from genotoxins, as well as stations classified as being of higher risk and where status might be expected to be improving. Additional sampling stations would be available if plaice and cod data could be included, and if assessment criteria should be established for these species. Relatively few of the flatfish monitoring stations are from near-shore areas; an assessment of genotoxic exposure would be more complete if it included data from coastal fish or mussel sites.
The assessment was based on the percentage of individual samples over the Background Assessment Criteria value. While we have confidence in this method, as it has previously been peer-reviewed (Baršienė and others, 2012b), it would be more consistent with other contaminants indicator assessments if the results for sampling sites were compared directly to the Background Assessment Criteria values. This requires the development of complex statistical models suitable for Poisson distributed data. Use of such models would also allow investigation of the effects of factors other than location, such as number of cells analysed, age of fish, sex, on assessment results.
Micronuclei frequency has been correlated with higher incidences of tumours in fish (Köhler and Ellesat, 2008). Mechanistically, DNA damage can lead to cancer formation, meaning micronucleus frequency in lymphocytes is predictive of human cancer risk (Bonassi and others 2010; Cardinale and others, 2012). However, due to the expected time-lags between the formation of micronucleus, tumour formation, and higher-level effects such as mortality, the development of Environmental Assessment Criteria based on population-level responses (such as the median concentration to cause mortality used to develop Environmental Assessment Criteria and Environmental Quality Standards) requires very lengthy exposure experiments and alternative approaches to assessing environmental risk of genotoxins.
References
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Baršienė J, Lazutka J, Šyvokienė J, Dedonytė V, Rybakovas A, Bagdonas E, Bjornstad A, Andersen OK (2004) ‘Analysis of micronuclei in blue mussels and fish from the Baltic and the North Seas’ Environmental Toxicology, 19: 365-371 (viewed on 13 December 2018)
Baršienė J, Dedonytė V, Rybakovas A, Andreikenaitė L, Andersen OK (2006) ‘Investigation of micronuclei and other nuclear abnormalities in peripheral blood and kidney of marine fish treated with crude oil’ Aquatic Toxicology 78, S99-S104 (viewed on 4 January 2019)
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Acknowledgements
Assessment metadata
| Assessment Type | UK Marine Strategy Framework Directive Indicator Assessment |
|---|---|
D8 Contaminants | |
D8.2. Effects of Contaminants | |
| Point of contact email | marinestrategy@defra.gov.uk |
| Metadata date | Wednesday, April 1, 2020 |
| Title | |
| Resource abstract | Biological effects (micronucleus) of contaminants in fish |
| Linkage | |
| Conditions applying to access and use | © Crown copyright, licenced under the Open Government Licence (OGL). |
| Assessment Lineage | The biological effect micronucleus assessment was carried out following a peer reviewed method (Baršiene and others. 2012). Baršiene, J., Rybakovas, A., Lang, T., Grygiel, W., Andreikenaite, L., and Michailovas, A. 2012. Risk of environmental genotoxicity in the Baltic Sea over the period of 2009 -2011 assessed by micronuclei frequencies in blood erythrocytes of flounder (Platichthys flesus), herring (Clupea harengus) and eelpout (Zoarces viviparus). Marine Environmental Research, 77, 35-42. |
| Indicator assessment results | |
| Dataset metadata | https://portal.medin.org.uk/portal/start.php#details?tpc=012_Marine_Scotland_FishDAC_12111 |
| Links to datasets identifiers | Please, see below |
| Dataset DOI |
The Metadata are “data about the content, quality, condition, and other characteristics of data” (FGDC Content Standard for Digital Geospatial Metadata Workbook, Ver 2.0, May 1, 2000).
Metadata definitions
Assessment Lineage - description of data sets and method used to obtain the results of the assessment
Dataset – The datasets included in the assessment should be accessible, and reflect the exact copies or versions of the data used in the assessment. This means that if extracts from existing data were modified, filtered, or otherwise altered, then the modified data should be separately accessible, and described by metadata (acknowledging the originators of the raw data).
Dataset metadata – information on the data sources and characteristics of data sets used in the assessment (MEDIN and INSPIRE compliance).
Digital Object Identifier (DOI) – a persistent identifier to provide a link to a dataset (or other resource) on digital networks. Please note that persistent identifiers can be created/minted, even if a dataset is not directly available online.
Indicator assessment metadata – data and information about the content, quality, condition, and other characteristics of an indicator assessment.
MEDIN discovery metadata - a list of standardized information that accompanies a marine dataset and allows other people to find out what the dataset contains, where it was collected and how they can get hold of it.
Recommended reference for this indicator assessment
Craig D. Robinson1 and John P. Bignell2 2018. Status assessment for biological effects (micronucleus) in fish. UK Marine Online Assessment Tool, available at: https://moat.cefas.co.uk/pressures-from-human-activities/contaminants/micronucleus/
1Marine Scotland
2Centre for Environment, Fisheries and Aquaculture Science