BSEP116B Biodiversity in the Baltic Sea - Helcom

Bearing in mind the complex hydrographic conditions,
and the fact that most Baltic Sea organisms
live at the edge of their physiological tolerance
range, anthropogenic chemical pollution has to be
seen as a further stress factor acting upon Baltic
Sea biodiversity. Only during recent decades have
we started to gain advanced understanding on
how multiple stressors (e.g., salinity, temperature,
hypoxia and chemical pollution) in combination
may affect biota and, thus, biodiversity.
6.7 Alien species
Chinese mitten crab (Eriocheir sinensis), Bothnian Bay, Finland
other surfaces has been required since 2008 (see
also Chapter 6.2, Maritime activities).
The Baltic is a sea of invaders as most animal and
plant species there are postglacial immigrants. In
contrast to distribution by natural spreading mechanisms,
alien species are defined as ”species or
lower taxa occurring outside of their natural range
(past or present) and dispersal potential...” (IUCN
2002). Some alien species have become invasive,
i.e., an alien whose population undergoes an exponential
growth stage and rapidly extends its range
(Occhipinti-Ambrogi & Galil 2004).
118
EU legislation concerning hazardous substances
includes the Regulation 2006/1907/EC concerning
the Registration, Evaluation, Authorisation and
Restriction of Chemicals (REACH), the Integrated
Pollution Prevention and Control Directive (96/61/
EC) and the Water Framework Directive (60/2000/
EC) complemented with a list of priority substances
(2455/2001/EC and a proposal COM(2006)397).
In addition, many HELCOM recommendations
concern the limitation of chemical pollution,
including HELCOM Recommendation 19/5 on the
HELCOM Strategy for hazardous substances.
6.6.4 Conclusions
There are encouraging signs of decreasing concentrations
and impacts on biota of certain hazardous
substances for which there are long-term monitoring
data. At the same time, there are increasing
concerns about the occurrence and negative biological
effects of substances such as TBT/TPhT, PFOS,
dioxins, furans and dioxin-like PCBs. The effects of
specific substances on Baltic biodiversity are difficult
to estimate owing to a lack of ecotoxicological information
or a lack of monitoring data concerning both
the occurrence of substances and their biological
effects in the Baltic marine environment.
Alien species act as modifiers of biodiversity and
biogeography. Owing to this, the characteristics
and integrity of the Baltic developed since the last
Ice Age are threatened, and the sea is subject to
worldwide homogenization of the aquatic flora
and fauna (Leppäkoski & Olenin 2001). Recent
establishment of a number of alien species populations
can be considered as biocontamination
(Arbačiauskas et al. 2008) of the indigenous Baltic
ecosystem because the invaders have caused alterations
in the taxonomic structure of the invaded
communities. In the Baltic, these changes have
been restricted mainly to the family and genus
level. For example, more than every second established
alien species included in the Baltic Sea Alien
Species Database (Olenin et al. 2008) belongs to
genera that are not represented among the native
flora and fauna of the Baltic Sea. In the inner Baltic,
some newcomers contribute to taxonomic diversity
at higher levels: the alien barnacle Balanus improvisus
is the only representative of its order Thoracica.
Similarly, the only species belonging to gambarid
decapod crayfish (Orconectes limosus and O. virilis)
and to mud crabs (Decapoda, Xanthidae (Rhithropanopeus
harrisii)) as well as the Chinese mitten
crab Eriocheir sinensis (family Grapsidae) are invaders
in the Baltic. Only one native comb jelly species