ENVIRONMENTAL STATEMENT BARDOLINO DEVELOPMENT

Bardolino Development Environmental Statement
their lifecycle in the pelagic stage before settling on the benthos. Important groups within this
category include the larvae of starfish and sea urchins (echinoderms), crabs and lobsters
(decapods), and some fish (DTI, 2001).
Zooplankton in the area of the proposed development comprises mostly neritic (coastal)
species and intermediate (mixed water) species, with biomass peaking from early May to mid-
July until October. The euphasusiid species, Thysanoessa inermis and T. raschi dominate
during the spring and summer months. During late summer and autumn, there is an
introduction of oceanic species (such as Calanus finmarchicus and Metridia lucens) via an
inflow of Atlantic waters.
Zooplankton communities can be affected by oil, both directly through the hydrocarbon
content of their food and indirectly via a change in the ecosystem. Reduced egg production
and an increase in juvenile mortality have been associated with oil contamination, and there is
a strong suggestion that oil treated with dispersant has a more pronounced effect. Any
possible long-term genetic changes caused by the disruption of internal chemical signals are
difficult to recognise and likely to be subtle (SAHFOS, 2001).
4.4.2 Benthos
Benthic fauna comprises species which live either within the seabed sediment (infauna) or on
its surface (epifauna). Such species, which may be either sedentary or motile, and may
encompass a variety of feeding habits (i.e. filter-feeding, predatory or deposit-feeding),
occupy a variety of different niches. Bacteria and benthic organisms play a major role in the
decomposition of organic material that originates from primary production by phytoplankton in
surface waters and settles on the seabed (NSTF, 1993). Some bacteria can degrade
hydrocarbons and use it as a source of food source (Clark, 1996).
Benthic fauna are also typically divided into various categories, principally according to size.
The largest are the megafauna and this comprises animals, usually living on the seabed,
which are large enough to be seen in bottom photographs and caught by trawl (i.e. brittle
stars, sea urchins, sea cucumbers, sea spiders, sponges, corals). Macrofauna are defined as
those animals that are between 250 µm and 300 µm in size. Meiofauna comprises the
smaller interstitial animals (mainly nematode worms and harpacticoid copepods) with a lower
size limit of between 45 µm and 62 µm.
Colonisation of sediments by different species is largely dependent on the type of sediment
present and its characteristics. Both physical and biological factors are important in
determining species abundance and distribution, including seabed depth, water movements,
salinity, temperature and available oxygen. Infaunal species are particularly vulnerable to
external influences, which alter the physical, chemical or biological community of the
sediment. Such infaunal organisms are largely sedentary and are thus unable to avoid
unfavourable conditions. Each species has its own response and degree of adaptability to
changes in the physical and chemical environment. Consequently the species composition
and relative abundance in a particular location provides a reflection of the immediate
environment, both current and historical (Clark, 1996).
Benthic fauna are susceptible to physical disturbance of the seabed, for example from fishingtrawls,
anchoring, pipeline trenching and rock dumping operations, or smothering from
discharged cuttings (DTI, 2001). The effects of discharged cuttings on benthic fauna include
physical smothering, the presence of potential toxins (heavy metals and hydrocarbons), and
organic enrichment (BMT Cordah, 1998). The responses shown by benthic communities to
cuttings discharges are the result of a combination of these effects. Directly below a
development, beneath the cuttings pile, the impact is through smothering. Beyond this point,
the effects of toxins and organic enrichment become more evident, and the changes in the
species composition, diversity and abundance of benthic communities may be attributed to
one or all of these impacts (BMT Cordah, 1998).
In addition to the possible impact from drilling operations, accidental events such as major oil
spills and blow-outs can result in oil reaching the seabed offshore. Effects reported from such
accidents range from none detected (e.g. after the Ekofisk blowout in 1977) to chemical
contamination but no acute biological effects detectable (e.g. after the wreck of the Braer in
1993) (DTI, 2001).
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