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Temporal trends in contaminants in Herring in the Baltic Sea in the period 1980-2005
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Key message
The temporal trend analyses of heavy metals showed 14 significant trends (5 upwards and 9 downwards) out of 50 tests. The remarkable upward trends were cadmium (2), zinc (2), and mercury (1). The downward trends were lead (5), mercury (3), and copper (1) .
The temporal trend analyses of PCB’s (Poly Chlorinated Biphenyls) and Lindane showed 41 significant trends (all downwards) out of 78 tests.
Results and assessment
The temporal trend analyses of heavy metals showed 14 significant trends (5 upwards and 9 downwards) out of 50 tests. For cadmium 2 areas (Hanöbukt, and Gävlebukt) had strong significant upward trend. For lead 5 areas showed a downward trend. Mercury showed a significant downward trend in one area and an upward in another area. Two upwards trends were found for zinc and one downward trend for cupper.
Indications of improvements of the situation compared to last years indicator update have occurred. Last years update showed 5 significant upward trends in the zinc concentrations. Three of these trends have now become insignificant due to decreasing concentrations in during the last years. Similarly one upward trend in copper has become insignificant whereas on non-significant trend for mercury has become significantly upwards. The two significant upwards trends for cadmium and on upward trend for zinc is starting to be reversed by decreasing concentrations during the last years.
The trend within the period 1995- has also been tested and several time series with no overall (whole period) trends has shown significant decrease during the more recent time (1995-).
The temporal trend analyses of PCB’s (Poly Chlorinated Biphenyls) and Lindane showed 41 significant trends (all downwards) out of 78 tests.
The trends documented in Table 1 are summarised in the Figures 1-13.
The observed upward trend in the concentration of cadmium in Herring is comparable to observations in other biotic matrices. The temporal trend of cadmium in seawater shows in general a downward trend. This remarkable difference between matrices has so far no clear explanation.
The downward trends of lead in the majority of the areas are probably caused by the reduced atmospheric input of anthropogenic lead due to the removal of lead from the petrol. The causes of the two upward trends in zinc are not clear.
Both copper and zinc are involved in many metabolic processes and carry out specific physiological roles which means that the observed changes can be related to natural variability as well as anthropogenic activities.
The very pronounced reduction in the concentration of PCB’s in many areas is probably a result of the regulations and bans in the countries around the Baltic Sea.
The downward trend in the concentration of Lindane in Herring in five areas is probably a result of regulations and bans in countries around Baltic Sea leading to a reduced emission of Lindane.
Table 1: The results of the time trend analysis using a non-parametric Mann-Kendall test. For each area and substances the results of the test are given. All the chemical analyses for Heavy metals are done on liver tissue except for Mercury were the analyses are done on muscle tissue. All the chemical analyses for PCB’s and Lindane are done on muscle tissue. (r): the Kendall tau correlation coefficient. (P): significance level. (n); number of observations (years) in the time series. The last year in the time series are indicated italic in parentheses. The significant upward trends are indicated by P-values shown in red while significant downward trends are indicated by P-values in green. The significance level of P<0.05 are used.
| Cadmium (liver) | Lead (liver) | Mercury (muscle) | Copper (liver) | Zinc (liver) | |
| Kattegat N | r=-0.095 | r=-0.584 | r=0.291 | r=-0.343 | r=0.165 |
| P=0.518 | P<0.0001 | P=0.042 | P=0.023 | P=0.277 | |
| n=24 (2005) | n=24 (2005) | n=25 (2005) | n=24 (2005) | n=23 (2005) | |
| Hanöbukt | r=0.463 | r=-0.377 | r=0.071 | r=0.275 | r=0.404 |
| P=0.002 | P=0.011 | P=0.612 | P=0.065 | P=0.008 | |
| n=24 (2005) | n=24 (2005) | n=26 (2005) | n=24 (2005) | n=23 (2005) | |
| Stockholm area | r=0.104 | r=-0.596 | r=0.167 | r=-0.073 | r=-0.266 |
| P=0.491 | P<0.0001 | P=0.234 | P=0.633 | P=0.085 | |
| n=23 (2005) | n=23 (2005) | n=26 (2005) | n=23 (2005) | n=22 (2005) | |
| Åland | r=0.195 | r=-0.197 | r=-0.089 | r=0.429 | r=-0.619 |
| P=0.543 | P=0.568 | P=0.66 | P=0.177 | P=0.051 | |
| n=7 (2004) | n=7 (2004) | n=14 (2004) | n=7 (2004) | n=7 (2004) | |
| Outer Gulf of Finland | R=-0.333 | r=0.577 | r=0.126 | r=-0.333 | r=0.733 |
| P=0.348 | P=0.143 | P=0.499 | P=0.348 | P=0.0388 | |
| n=6 (2004) | n=6 (2004) | n=16 (2004) | n=6 (2004) | n=6 (2004) | |
| Inner Gulf of Finland | R=0.143 | r=0.5 | r=-0.354 | r=0.071 | r=-0.357 |
| P=0.621 | P=0.127 | P=0.025 | P=0.805 | P=0.216 | |
| n=8 (2005) | n=8 (2005) | n=21 (2005) | n=8 (2005) | n=8 (2005) | |
| Gävlebukt | r=0.346 | r=-0.419 | r=-0.311 | r=0.273 | r=0.263 |
| P=0.018 | P=0.005 | P=0.03 | P=0.068 | P=0.081 | |
| n=24 (2005) | n=24 (2005) | n=25 (2004) | n=24 (2005) | n=23 (2005) | |
| Bothnian Sea | r=0.357 | r=0.5 | r=-0.67 | r=0.071 | r=-0.357 |
| P=0.216 | P=0.127 | P<0.0001 | P=0.805 | P=0.216 | |
| n=8 (2005) | n=8 (2005) | n=20 (2005) | n=8 (2005) | n=8 (2005) | |
| Bothnian Bay | r=0.143 | r=-0.157 | r=0.143 | r=-0.143 | |
| P=0.652 | P=0.0.286 | P=0.652 | P=0.652 | ||
| n=7 (2004) | n=7 (2004) | n=24 (2004) | n=7 (2004) | n=7 (2004) | |
| Luleå | r=0.037 | r=-0.476 | r=0.057 | r=0.045 | r=0.264 |
| P=0.797 | P=0.0009 | P=0.676 | P=0.759 | P=0.074 | |
| n=25 (2005) | n=25 (2005) | n=27 (2005) | n=25 (2005) | n=24 (2005) |
Table 1 Continued
| CB28 | CB52 | CB101 | CB118 | CB138 | CB153 | CB180 | HCHG Lindane | |
| Kattegat N | r=-0.333 | r=-0.424 | r=-0.779 | r=-0.765 | r=-0.765 | r=-0.554 | r=-0.581 | r=-0.819 |
| P=0.089 | P=0.019 | P<0.0001 | P=0.0001 | P<0.0001 | P=0.002 | P=0.002 | P<0.0001 | |
| n=17 (2005) | n=17 (2005) | n=17 (2005) | n=17 (2005) | n=17 (2005) | n=17 (2005) | n=17 (2005) | n=16 (2004) | |
| Hanöbukt | r=0.046 | r=-0.529 | r=-0.426 | r=-0.477 | r=-0.307 | r=-0.033 | r=0.046 | r=-0.956 |
| P=0.802 | P=0.003 | P=0.017 | P=0.006 | P=0.075 | P=0.85 | P=0.791 | P<0.0001 | |
| n=17 (2005) | n=17 (2005) | n=17 (2005) | n=18 (2005) | n=18 (2005) | n=18 (2005) | n=18 (2005) | n=17 (2004) | |
| Stockholm area | r=-0.52 | r=-0.66 | r=-0.464 | r=-0.477 | r=-0.464 | r=-0.268 | r=-0.373 | r=-0.868 |
| P=0.003 | P=0.0001 | P=0.007 | P=0.006 | P=0.007 | P=0.12 | P=0.031 | P<0.0001 | |
| n=18 (2005) | n=18 (2005) | n=18 (2005) | n=18 (2005) | n=18 (2005) | N=18 (2005) | n=18 (2005) | n=17 (2004) | |
| Åland | r=0.195 | r=-0.786 | r=-0.571 | r=-0.786 | R=-0.714 | r=-0.929 | r=-0.143 | |
| P=0.543 | P=0.006 | P=0.048 | P=0.007 | P=0.013 | P=0.001 | P=0.652 | ||
| n=5 (2002) | n=7 (2002) | n=8 (2002) | n=8 (2002) | n=8 (2002) | N=8 (2002) | n=8 (2002) | n=7 (2002) | |
| Outer Gulf of Finland | r=-0.182 | r=-0.429 | r=-0.429 | r=-0.571 | R=-0.429 | r=-0.50 | r=0.238 | |
| P=0.533 | P=0.138 | P=0.138 | P=0.048 | P=0.138 | P=0.083 | P=0.453 | ||
| n=4 (2002) | n=8 (2002) | n=8 (2002) | n=8 (2002) | n=8 (2002) | N=8 (2002) | n=8 (2002) | n=7 (2002) | |
| Inner Gulf of Finland | r=-0.141 | r=0.167 | r=-0.364 | r=-0.410 | r=-0.581 | r=-0.44 | r=-0.657 | r=-0.333 |
| P=0.6 | P=0.41 | P=0.06 | P=0.033 | P=0.003 | P=0.023 | P=0.0006 | P=0.113 | |
| n=9 (2005) | n=14 (2005) | n=15(2005) | n=15 (2005) | n=15 (2005) | n=15 (2005) | n=15 (2005) | n=13 (2005) | |
| Gävlebukt | r=-0.299 | r=-0.134 | r=-0.515 | r=-0.338 | r=-0.485 | r=-0.265 | r=-0.294 | r=-0.912 |
| P=0.134 | P=0.488 | P=0.004 | P=0.058 | P=0.007 | P=0.138 | P=0.099 | P<0.0001 | |
| n=16 (2005) | n=15 (2005) | n=17 (2005) | n=17 (2005) | n=17 (2005) | n=17 (2005) | n=17 (2005) | n=16 (2004) | |
| Bothnian Sea | r=-0.036 | r=0.18 | r=-0.273 | r=-0.491 | r=-0.587 | r=-0.527 | r=-0.745 | r=-0.378 |
| P=0.9 | P=0.473 | P=0.243 | P=0.036 | P=0.013 | P=0.024 | P=0.001 | P=0.128 | |
| n=8 (2005) | n=10 (2005) | n=11 (2005) | n=11 (2005) | n=11 (2005) | n=11 (2005) | n=11 (2005) | n=10 (2005) | |
| Bothnian Bay | r=0.074 | r=0.065 | r=-0.209 | r=-0.165 | r=-0.319 | r=-0.275 | r=-0.318 | r=-0.168 |
| P=0.802 | P=0.759 | P=0.298 | P=0.412 | P=0.112 | P=0.171 | P=0.1124 | P=0.45 | |
| n=8 (2002) | n=13 (2002) | n=14 (2002) | n=14 (2002) | n=14 (2002) | n=14 (2002) | n=14 (2002) | n=12 (2002) | |
| Luleå | r=-0.348 | r=-0.471 | r=-0.556 | r=-0.516 | r=-0.634 | r=-0.399 | r=-0.477 | r=-0.887 |
| P=0.095 | P=0.018 | P=0.001 | P=0.003 | P=0.0002 | P=0.021 | P=0.006 | P<0.0001 | |
| n=16 (2005) | n=15 (2005) | n=18 (2005) | n=18 (2005) | n=18 (2005) | n=18 (2005) | n=18 (2005) | n=17 (2004) |
Fig.1. Temporal trends of cadmium in herring livers. Red arrows indicate a significant upward trend. Green arrows indicate a significant downwards trend. Blue dots indicate no significant trend. Blue dots with green arrows indicate no trend during the whole time series but significant decrease from 1995 onwards. Click image to enlarge.
Fig.2. Temporal trends of lead in herring livers. Red arrows indicate a significant upward trend. Green arrows indicate a significant downwards trend. Blue dots indicate no significant trend. Click image to enlarge.
Fig.3. Temporal trends of mercury in herring livers. Red arrows indicate a significant upward trend. Green arrows indicate a significant downwards trend. Blue dots indicate no significant trend. Blue dots with green arrows indicate no trend during the whole time series but significant decrease from 1995 onwards. Click image to enlarge.
Fig.4. Temporal trends of copper in herring livers. Red arrows indicate a significant upward trend. Green arrows indicate a significant downwards trend. Blue dots indicate no significant trend. Click image to enlarge.
Fig.5. Temporal trends of zinc in herring livers. Red arrows indicate a significant upward trend. Green arrows indicate a significant downwards trend. Blue dots indicate no significant trend. Click image to enlarge.
Fig.6. Temporal trends of CB28 in herring livers. Red arrows indicate a significant upward trend. Green arrows indicate a significant downwards trend. Blue dots indicate no significant trend. Click image to enlarge.
Fig.7. Temporal trends of CB52 in herring livers. Red arrows indicate a significant upward trend. Green arrows indicate a significant downwards trend. Blue dots indicate no significant trend. Click image to enlarge.
Fig.8. Temporal trends of CB101 in herring livers. Red arrows indicate a significant upward trend. Green arrows indicate a significant downwards trend. Blue dots indicate no significant trend. Click image to enlarge.
Fig.9. Temporal trends of CB118 in herring livers. Red arrows indicate a significant upward trend. Green arrows indicate a significant downwards trend. Blue dots indicate no significant trend. Click image to enlarge.
Fig.10. Temporal trends of lead CB138 in herring livers. Red arrows indicate a significant upward trend. Green arrows indicate a significant downwards trend. Blue dots indicate no significant trend. Click image to enlarge.
Fig.11. Temporal trends of CB153 in herring livers. Red arrows indicate a significant upward trend. Green arrows indicate a significant downwards trend. Blue dots indicate no significant trend. Blue dots with green arrows indicate no trend during the whole time series but significant decrease from 1995 onwards. Click image to enlarge.
Fig.12. Temporal trends of CB180 in herring livers. Red arrows indicate a significant upward trend. Green arrows indicate a significant downwards trend. Blue dots indicate no significant trend. Click image to enlarge.
Fig.13. Temporal trends of Lindane in herring livers. Red arrows indicate a significant upward trend. Green arrows indicate a significant downwards trend. Blue dots indicate no significant trend. Blue dots with green arrows indicate no trend during the whole time series but significant decrease from 1995 onwards. Click image to enlarge.
Metadata
Data on various contaminants (cadmium, lead, mercury, copper, zinc, PCB’s and Lindane) in Herring exists from several areas of the Baltic Sea. Based on extractions from the ICES Database on contaminants in biota 10 areas with sufficient temporal coverage were identified. The areas are listed in Table 1 and 2. The length of the time series is rather variable. Some of them extend back to 1980 while others cover only the very recent years. Only time series of more than 5 years are considered in this analysis, but the number of years covered are indicated in the tables. Time series that ended before 2002 are not treated in this analysis.
Time trend analyses were made using the non-parametric Mann-Kendall test using a two-sided test with a significance level of 5%. The analyses revealed some significant trends in various contaminants. The detailed results of the analyses can be found in Table 1 and 2. In total, 55 of the 128 trend-tests showed a significant trend. Even though repetitive testing increases the risk of making a Type I error (getting a significant trend when there actually are no trend) the number of significant trends is well over what would be expected (~6-7) from this error. The time frame for this analysis is the period 1980-2005. Data from some years (especially 2003) are lacking in some areas.
For reference purposes, please cite this indicator fact sheet as follows:
[Author’s name(s)], [Year]. [Indicator Fact Sheet title]. HELCOM Indicator Fact Sheets 2007. Online. [Date Viewed], http://www.helcom.fi/environment2/ifs/en_GB/cover/.
Last updated 3.9.2007