This indicator is a HELCOM supplementary indicator and is applicable in assessment units shared by Finland and Sweden.
Monitoring of embryo malformation rates in the Contracting Parties of HELCOM is described on a general level in the HELCOM Monitoring Manual in the monitoring topic Biological effects of contaminants.
However, no specific sub-programme or HELCOM monitoring guidelines have so far been developed. As the information is not yet included in the HELCOM Monitoring Manual, a description of the main points of the guidelines applied nationally are presented in the indicator report. Monitoring guidelines are documented in detail in 'Handboken för miljöövervakning' (in Swedish) (eng. The handbook for environmental monitoring).
The amphipod Monoporeia affinis and the marine amphipod Pontoporeia femorata are included in the national monitoring program in Sweden (SNMMP). However, P. femorata has very low abundance in the Bothnian Sea and the Quark. Collection of gravid females of the amphipods Monoporeia affinis and Pontoporeia femorata takes place in mid- to late January, when the embryos are in late developmental stages, which facilitates the embryo analysis. To obtain a quantitative sample, a grab sampler (e.g. Van Veen) is used to collect amphipods inhabiting sediments. When amphipods occur at low abundances, a bottom sled is used to achieve greater sampling efficiency. To collect the sediment-dwelling amphipods, 5-and 1-mm sieves could be used depending on the size of the amphipods. For species producing several broods during the reproductive period, the sampling should preferably be carried out in the early mating period when specimens in the population demonstrate a more synchronous maturation than in the later part of the reproductive period. It is also possible to collect sediment and sexually maturing females and males in situ, to be incubated in aquaria allowing for mating and embryogenesis. In this case, the field-collected amphipods should be transported to the laboratory in ambient water/sediment and at temperature matching their natural habitat at the time of sampling. Many Baltic glacial relicts are stenotherm cold-water species and are particularly sensitive to temperature stress during the oogenesis (Eriksson Wiklund and Sundelin 2001). During sampling of amphipods Baltic Standard is used.
The analysis of embryos is performed on living gravid females under a stereomicroscope. The frequency of malformed embryos of Monoporeia affinis has a comparatively low variation in pristine areas and 50 gravid females per station give sufficient statistical power. They are analysed for fecundity in terms of number of eggs per female, number of malformed, membrane damaged embryos, dead embryos and females with dead broods. For details see Sundelin et al. 2008 (Times no 41, http://ices.dk/publications/our-publications/Pages/-ICES-Techniques-in-Marine-Environmental-Sciences-.aspx). When conducting embryo analyses, several persons analyse the same brood to assess the accuracy of determination. Normally there is 95-98 % agreement between the experts.
The amphipods used for the secondary threshold are G. tigrinus, G. fasciatus and P. robustoides. These species were used as bioindicators in survival test within Russian Research Monitoring Programs by different institutions from 1990s, and monitoring of amphipod reproduction started in 2009. This method is developed mainly by the Zoological Institute of the Russian Academy of Sciences. Preliminary assessment of environmental health in the eastern Gulf of Finland was conducted at 12 coastal sites and is planned to continue. Collection of these amphipods is conducted from end of May to September by a grab or scuba diving. The field-collected living amphipods are transported carefully to the laboratory and analysed under stereomicroscope. The amphipods are separated into four categories: juveniles, males, females I (without eggs in marsupium) and females II (gravid females, with eggs/embryos in marsupium). The determination of the reproductive status of the females is based on the presence and structure of brood plates (oostegites). The immature females have oostegites lacking setae. The gravid females are size-sorted in a 0.5 mm step and placed individually into Petri dishes; then the eggs are carefully teased out of the marsupium with pins or forceps. Only females carrying a closed marsupium are included in the analysis. The seven developmental stages of eggs (embryos) may be distinguished according to Weygoldt (1924) and Scadsheim (1982), cited in Pöckl (1993).
The indicator on malformations in amphipod embryos has been monitored in the SNMMP since 1994 at 14 stations in Bothnian Sea and northern Baltic proper, in 2012 the program design was changed to include more stations to give a more comprehensive covering of the Baltic (Monitoring requirements figure 1).
Monitoring of amphipod reproduction in the Gulf of Finland started in 2009 and is conducted by the Zoological Institute of the Russian Academy of Sciences.
Monitoring requirements figure 1. Sampling stations used for amphipod collection in 1994-2011 (left) and from 2012 onwards (right) within the Swedish National Marine Monitoring Programme (SNMMP).
Monitoring of embryo malformation rates should be carried out in all relevant HELCOM assessment units. Extending the spatial scope of the monitoring effort would increase the possibility to accurately evaluate the pressure from environmental contaminants on benthic animals in the Baltic Sea. To obtain a more comprehensive picture of the health status of the amphipods, it would be optimal to include also stations in the Bothnian Bay, southern part of the Baltic, including Bornholm. Particularly alarming situation in the Hanö Bight has been found by the surveys conducted during the assessment period. Recently Estonian scientists have started to monitor Monoporeia affinis in coastal areas. Also, in the Gulf of Riga, scientists started to work with embryo malformations of amphipods including M. affinis.