Individual health and reproductive disorders

Imposex and intersex in certain species of marine snails (Prosobranch gastropods) are signs of endo-crine disruption and are widely used as specifi c biomarkers for TBT contamination (OSPAR 2008, Strand 2009a, 2009b). Ship traffi c is regarded as the main source of TBT in the Baltic (see also Section 2.2.4). Imposex refers to the develop-ment of male sexual characteristics superimposing female characteristics, while intersex refers to the transformation of female sexual characteristics towards those of a male. The different stages of imposex are classifi ed using a vas deferens sequence index (VDSI).

The red whelk (Neptunea antiqua) represents a very sensitive species with regard to imposex because high levels occur even in non-coastal areas. In the Belt Sea area (Denmark), 100%

of the red whelks have developed imposex and about 10% of the individuals were regarded as sterile due to a severe imposex development stage (Strand 2009a). Similar to TBT levels, the levels of imposex have also declined during recent years owing to the ban on the use of TBT as an antifouling agent on ship hulls. This trend is par-ticularly clear in the netted whelk (Hinia reticu-lata) from coastal waters, whereas the trend is not completely clear in the more long-living red whelk in the open-sea areas of the Belt Sea (Fig.

2.43). In low-salinity regions of the Baltic Sea, imposex has also been found in the mud snails Hydrobia ulvae (Gercken & Sordyl 2007, Magnus-son 2008).

Adverse effects of various hazardous substances on the reproduction of the soft-bottom amphi-pod Monoporeia affi nis are visible as malformed embryos in the Baltic Sea (Sundelin & Eriksson 1998, Sundelin et al. 2008). This variable has been

0

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007

Red whelk (open waters) Netted whelk (coastal waters)

-Imposex intensity (VDSI)

Threshold for red whelk

Threshold for netted whelk

Year

Distance from point source (km)

0 5 10 15 20 25 30

Figure 2.43 Temporal trends of imposex levels (intensity classi-fi ed as VDSI with 4.0 as the maximum value) in two marine snail species, the netted whelk (Hinia reticulata) and the more sensi-tive red whelk (Neptunea antiqua) from coastal and open waters in the Danish part of the Belt Sea (Strand 2007). Threshold values for imposex in the two species are shown for comparison (OSPAR 2008). Symbols denote median values and broken lines show 95%

confi dence intervals.

Figure 2.44 The proportion of malformed embryos in the amphi-pod Monoporeia affi nis increases with decreasing distance from the point source, suggesting that there is a strong relationship between the emission sources studied and the malformation rate.

The analysis includes results from a total of 24 sampling stations from six regional studies at polluted recipient sites. Results have been transformed into “effect sizes” in order to make the studies comparable (mean-centred and scaled with 1/SD).

57

Effects on the reproduction of the viviparous fi sh eelpout (Zoarces viviparus) have been measured in coastal areas of Sweden, Denmark, Germany and Poland. These measurements are now included in national monitoring programmes. The presence of abnormal development of embryos and larvae in eelpout broods is used as an indicator of impaired reproduction because chronic exposure to various contaminants has the potential to induce adverse developmental effects in fi sh (Fig. 2.46). In some areas that are known to be more polluted, mal-formed larvae are found in more than 80% of the eelpout broods (Vetemaa et al. 1997, Strand et al. 2004, Gercken et al. 2006). Other studies on endocrine disturbances in eelpout carried out in German and Danish coastal waters have also recorded a widespread occurrence of intersex, i.e., primary oocyte development, in the testes of more than 25% of the males studied (Fig. 2.47) (Gercken & Sordyl 2002, Gercken & Sundt 2007, Strand et al. 2009). A skewed sex ratio with a prev-alence of females in eelpout broods was observed close to an effl uent output site of a Swedish pulp mill (Larsson et al. 2000).

Diseases in wild Baltic Sea fi sh have been moni-tored on a regular basis since the beginning of the 1980s as a component of national environmental monitoring and assessment programmes. Within these programmes, signifi cant alterations in the disease prevalence are used as a general ecosystem health indicator, refl ecting the effects of environ-mental change, including anthropogenic impacts, on the disease resistance of wild fi sh. The fi sh dis-eases cannot be directly linked to any specifi c com-pound, but they are probably caused by multiple stressors in the environment.

Temporal changes in the prevalence of one of the most conspicuous diseases of Baltic cod (Gadus morhua), the bacterial skin ulcer disease, are shown in Figure 2.48. Over the period 1994–2008, there was a marked fl uctuation in prevalence, with maximum values of 23.6% in 1998 (ICES Subdivi-sion 24) and 18.9% in 2002 (ICES SubdiviSubdivi-sion 26), respectively. For some periods, there is an indication of upward or downward trends.

The reproductive disorder of salmon (Salmo salar), the M74 syndrome, which is manifested as high mortalities of yolk-sac fry and which threatened the existence of salmon in the Baltic Sea during its Figure 2.45 Percentage of malformed embryos in the amphipod

Monoporeia affi nis collected from stations in the Bothnian Sea and the Baltic Proper. The malformation rate increased between 2001 and 2004 in the Baltic Proper for unknown reasons. Variance is given as upper 95% confi dence intervals.

0 2 4 6 8 10 12 14 16 18 20

1999 2000 2001 2002 2003 2004 2005 2006 2007

% Malformed embryos

Bothnian Sea Baltic proper

Years

Normal Malformed

Figure 2.46 Example of two-headed malformed eelpout larvae (Photo: Jakob Strand).

Figure 2.47 Intersex in eelpout male testis.

PN: primary oocyte, SZ: spermatozoans (Photo: Jonna Tomkiewicz).

SZ

PN1

58

lence decreased somewhat during the 2000s but still remains at a high level. Even though there is no certainty regarding the cause of the increased ulcer formation (Bergman 1999, Bäcklin et al.

2009), PCBs are suspected to be associated with interrupted pregnancies and uterine obstructions in both ringed and grey seals as well as with uterine leiomyomas in the latter (Bergman & Olsson 1985, Bäcklin et al. 2003, Bredhult et al. 2008), and thus probably contributed to the observed small number of Baltic seals in the 1970s. Since the mid-very high prevalence in the 1990s, has been

statis-tically related to high concentrations of dioxins and DL-PCBs in the muscle of female salmon (Vuorinen et al. 1997, 2002), but the cause-effect relationship is not clear.

The prevalence of intestinal ulcers in immature Baltic grey seals (Halichoerus grypus) has increased since the middle of the 1980s, and ten years later the prevalence also increased in mature grey seals (Fig. 2.49A). In the young age group, ulcer

preva-prevalence (%) ICES SD 24

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

ICES SD 22

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

prevalence (%) prevalence (%)

ICES SD 26

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

prevalence (%) ICES SD 25

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00

1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Figure 2.48 Prevalence (± 95% C.I.) of acute skin ulcers in Baltic cod (Gadus morhua) from ICES Subdivisions 22, 24, 25 and 26 in the period 1994–2008 (data from December surveys) (T. Lang, unpublished data).

59

1980s, increases in population sizes of grey seals have been recorded and no uterine obstruction has been observed in Swedish waters since 1997 (Bergman 2007, Bäcklin et al. 2009) (Fig. 2.49B).

The occurrence of uterine leiomyomas has also decreased since the 1990s (Bredhult et al.2008).

A signifi cant phenomenon considered to be directly related to elevated levels of hazardous substances, especially DDT and PCBs, has been the disturbances observed in reproduction and health status of the white-tailed sea eagle (Haliaeetus albicilla). Reproduction in the Baltic eagle popu-lation in the 1970s was reduced to one fi fth of the pre-1950 background level due to a severely reduced hatching success, which led to a dimin-ished population size (Helander et al. 2009). The subsequent recovery correlates with reductions in environmental concentrations of organochlorine compounds resulting from bans on the use of DDT and PCBs during the 1970s around the Baltic Sea (Fig. 2.50). Since the mid-1990s, eagle pro-ductivity has largely returned to pre-1950 levels and the population on the Swedish Baltic coast has increased at a rate of 7.8% per year since 1990 (Helander et al. 2009). However, signs of an improvement in productivity could only be seen after the residue concentrations of DDE in the eggs declined to below 400 mg kg⁻¹. Based on productivity and egg residue concentrations meas-ured in 82 individual females between 1965 and 1997, a lowest observable effect level (LOEL) for DDE of approximately 100–120 mg kg⁻¹ has been estimated. The further positive development of productivity from 1998–2005 continues to support the estimated LOEL.

In another case, exceedingly high chick mortalities have led to the population decline of the nominate lesser black-backed gull (Larus fuscus fuscus) in the Gulf of Finland, which has been associated with the very high concentrations of organochlorines observed in the liver of the chicks (Hario et al.

2004).

Prevalence of intestinal ulcers in Baltic grey seals

0

Prevalence of uterine obstructions and leiomyomas in grey seals older than 4 years

0

DDE - PCB concentration (ppm)

0 Figure 2.49 Prevalence of A) intestinal ulcers and B) uterine obstructions and leiomyomas in the Baltic grey seal (Halichoerus grypus) during different periods from 1977–2008.

Figure 2.50 Mean productivity (green line) vs. egg lipid concentra-tions of DDE (red) and PCBs (blue) of the white-tailed sea eagle (Haliaeetus albicilla) on the Swedish Baltic Sea coast from 1965–

2005 (Helander et al. 2002, 2008). The area below a previously determined lowest estimated effect level (LOEL) for DDE is marked green. Mean productivity is the mean number of nestlings in all occupied nests.

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Im Dokument the Baltic Sea (Seite 59-63)